The morphological description of wear particles in lubricating oil is crucial for wear state monitoring and fault diagnosis in aero-engines. Accurately and comprehensively acquiring three-dimensional (3D) morphological data of these particles has become a key focus in wear debris analysis. Herein, we develop a novel multi-view polarization-sensitive optical coherence tomography (PS-OCT) method to achieve accurate 3D morphology detection and reconstruction of aero-engine lubricant wear particles, effectively resolving occlusion-induced information loss while enabling material-specific characterization.
本文设计了一种由两个一端封堵的金属-绝缘体-金属(MIM)波导与一个的D形腔耦合组成表等离激元波导结构。使用有限元方法(FEM)模拟了该结构的传输特性、磁场分布以及折射率传感特性。在透射光谱中可以明显观察到多Fano共振现象。这些Fano共振是由于D形谐振腔的产生的共振离散态与一端封堵的MIM波导产生的连续状态之间相互耦合产生。通过系统地调整结构参数,研究了其对Fano共振调制的影响。此外,通过改变MIM波导中绝缘层的折射率研究了基于Fano共振折射率传感特性。结果表明,在第一个Fano共振峰处实现了最大1155 RIU/nm的灵敏度。这些研究对高灵敏度光子器件、微型传感器、未来新型片上传感的设计和研究提供了新的途径。
为了对古城墙修复性能进行科学评估,本研究以明代得胜堡长城为对象,采用太赫兹时域光谱(THz-TDS)与红外热成像技术对其土坯砖垒砌法修复段(1区)、保存完好段(2区)和逐层夯筑法修复段(3区)进行检测分析。结果显示:1区的THz光谱数据(时延为3.72 ps、折射率2.224)与原始墙体(2区时延3.02 ps、折射率2.107)差异显著,而3区THz光谱数据(时延3.12 ps、折射率2.098)与2区的几乎一致;红外热像图也表明3区的热均匀性更好,裂缝、毛细现象、生物病害的发生率更低,基本达到了“修旧如旧”的目的。因此,将城墙区域的红外热像图与原位取样的THz光谱相结合方法,不仅可以对修复性能进行定量评估,而且可以为传统工艺科学化评价提供新手段。
Metalens technology has been applied extensively in miniaturized and integrated infrared imaging systems. However, due to the high phase dispersion of unit structures, metalens often exhibits chromatic aberration, making broadband achromatic infrared imaging challenging to achieve. In this paper, six different unit structures based on chalcogenide glass are constructed, and their phase-dispersion parameters are analyzed to establish a database. On this basis, using chromatic aberration compensation and parameterized adjoint topology optimization, a broadband achromatic metalens with a numerical aperture of 0.5 is designed by arranging these six unit structures in the far-infrared band. Simulation results show that the metalens achieves near diffraction-limited focusing within the operating wavelength range of 9-11 µm, demonstrating the good performance of achromatic aberration with flat focusing efficiency of 54% - 58% across all wavelengths.
为实现肿瘤标志物的早期诊断,本文设计了一种适用于流动相样本的单分子免疫检测系统,并对其光学荧光成像平台及图像检测计数算法进行了研究。首先,为满足低浓度、高通量样本的即时检测需求,提出了一种基于流动相的单分子免疫检测方法。其次,结合微流控芯片的规格要求,设计了一套光学荧光成像检测平台,通过滤光和分光元件的合理配置,利用多模块集成实现荧光样本的高分辨率成像。最后,在离焦粒子的图像检测计数算法的基础上,优化了特征匹配方法,以高效处理非焦面荧光粒子信号。实验结果表明,本系统在单分子免疫标志物样本检测中的下限可达到0.001 pg/mL,在0.001~1 pg/mL的理论检测范围内,精度小于10% CVs,可在一小时内完成最多十份样本的检测。本系统满足了单分子免疫检测的稳定性、高灵敏度和高通量检测需求,在癌症早期筛查领域具有重要的应用前景。
在结构光三维测量系统中,相机离焦现象不可避免。在离焦的影响下,物体表面的复杂纹理会引入显著的相位误差,影响测量精度。本文针对该问题,分析并构建了该相位误差的理论模型,指出了其与纹理变化方向的关系,并由此提出了一种基于双向条纹点云匹配的复杂纹理误差校正方法。理论上,通过投影横纵条纹图案获得的双向相位信息应解出完全一致的点云。基于这一原理,本文提出以最小化横纵点云对应点距离为目标,修正每个点对应的相位,最终得到校正后的点云。为了消除标定参数误差导致的点云整体偏移,本文通过点云匹配进行了预校正。对比实验的结果表明:对实际物体,相较传统方法,本文方法的平均绝对误差(MAE)和均方根误差(RMSE)最高可分别降低33.6%和39.1%。本文方法能够以更高的精度重建带有复杂纹理的物体。
为了解决现有超构表面位移测量技术无法同时测量多个物理量的问题,本文设计了一种超构表面级联结构,可用于同时测量径向角位移和纵向线位移。首先,根据级联超构表面对圆偏振光的联合相位调制阐述了位移测量的工作原理。接着,以琼斯传输矩阵分析了相位延迟携带的位移信息,推导了角位移与线位移的数学表征。然后,以设计目标作为约束条件优化单元结构参数,构建超构表面的模型。最后,采用时域有限差分法对超构表面结构进行模拟,验证方法可行性并分析器件测量性能。结果表明,在633nm的工作波长下,角位移灵敏度为0.9716,理论分辨率34.27μrad,线位移灵敏度为0.0041,理论分辨率8.12nm。该方法提高了超构表面位移测量技术的测量自由度,并有希望进一步扩展到六维,以此实现对待测目标的完全姿态确定。
光电混合的光学卷积神经网络(OCNN)通过结合光子元件的并行线性计算能力和电子元件的非线性处理优势,在分类任务中展现了巨大的潜力。然而,光子元件的制备误差即不精确性和执行后向传播的FPGA中电路噪声显著影响了网络性能。本文搭建了光电混合的OCNN,其中的线性计算由基于马赫-曾德尔干涉仪的光学计算层完成,而池化计算及训练过程在FPGA中完成。本文着重研究了在FPGA上的片上训练方案,分析了噪声对片上训练效果的影响,并提出了增强OCNN抗噪能力的网络优化策略。具体地,通过调整池化方式和尺寸以增强OCNN的抗噪性能,并在池化层后引入Dropout正则化以进一步提升模型的识别准确率。实验结果表明,本文采用的片上训练方案能够有效修正光子元件的不精确性带来的误差,但电路噪声是限制OCNN性能的主要因素。此外,当电路噪声较大时,例如当电路噪声造成的MZI相位误差标准差为0.003,最大池化方式与Dropout正则化的结合可以显著提升OCNN的测试准确率(最高达78%)。本研究为实现OCNN的片上训练提供了重要的参考依据,同时为光电混合架构在高噪声环境下的实际应用探索提供了新的思路。
As a potential alternative for energy in quantum regime, a quantum battery inevitably undergoes the process where the extracted work deteriorates due to the environmental decoherence. To inhibit the energy dissipation, we have put forward a scheme of a moving atom battery in a lossy cavity coupled to a structured environment. We investigate the dynamics of the maximally extracted work called the ergotropy by the open quantum system approach. It is found out that the decay of quantum work is significantly retarded in the non-Markovian environment. In contrast to the static case, the storage performance of the quantum battery is improved when the atom is in motion. The effect of energy preservation becomes more pronounced at higher velocities. Both the momery effect and motion control can play a positive role in extending the discharge lifetime. In addition, we have investigated the effects of environmental temperature, random noises, and quantum entanglement. These present results provides a feasible protocol for the open quantum battery.
Diffractive waveguides have emerged as a particularly promising solution for augmented reality (AR) near-eye display technologies. These waveguides are characterized by their light weight, wide field of view, and large eyebox. However, most commercially available AR waveguide simulation software has been developed by foreign companies, and there has been little advancement in domestic 3D visualization software for optical waveguide design and simulation. The present study is, to the best of our knowledge, the first to develop 3D visualization module for optical waveguide design and simulation based on ray-field tracing. Using this module, a two-dimensional exit-pupil-expansion diffractive waveguide has been designed, and a systematic design workflow is demonstrated. The workflow integrates
In order to achieve real-time 3D measurement of dynamic objects and to overcome the measurement accuracy limitations caused by spectral aliasing of different carrier frequencies in traditional Fourier demodulation methods, as well as the color coupling problem in color composite stripe projection techniques, this paper proposes a three-frequency color stripe projection profilometry method based on fast iterative filtering. The method first captures a color image using a CCD camera, where the red, green, and blue channels carry gray stripe images with different carrier frequencies. Background interference is then reduced by component subtraction, followed by carrier frequency separation and color decoupling using fast iterative filtering. The subsequent application of the Fourier transform is applied to the carrier-frequency stripe images in the red, green, and blue channels enables the extraction of wrapped phase information. To achieve accurate phase unwrapping, a spatial domain unwrapping algorithm is employed. The low-frequency phase is first unwrapped, followed by the middle and high-frequency phases, which are unwrapped sequentially to complete the entire phase unwrapping process. The simulation and experimental results demonstrates that the proposed method exhibits a phase unwrapping accuracy that is 7 times higher than that of traditional Fourier methods. In comparison with other single-frame demodulation methods, the proposed method demonstrates superior accuracy and robust noise resistance, thus providing an effective technical solution for high-precision, dynamic real-time 3D measurement.
The purpose of this study is to solve the problem of optical waveguide shape defects. These defects occur during the process of vertical end face waveguide bridging in photonic chips. The obstruction of the laser beam by the surface of the chip is the root cause of these defects. The present study investigates the light intensity distribution based on the focusing light field of high numerical aperture (NA) lenses. The study focuses on the laser focus at different
In order to quantitatively assess the solar stray light suppression capability of the heliospheric imager, a testing approach and experimental validation of the solar stray light suppression capability of the heliospheric imager were investigated. In this paper, we propose a method to test the solar stray light suppression capability of the heliospheric imager under laboratory circumstances by conducting segmented tests of the front-end baffle and the camera. This approach circumvented the issue that the structural scattering caused by the test under vacuum conditions would be overly large and influence the accuracy of the test results. The proposed method was then employed to assess the effectiveness of a heliospheric imager in suppressing solar stray light under laboratory conditions. The experimental results indicated that the PST of the heliospheric imager was 1.4×10−8 at WACH1 and 4.3×10−9 at WACH2. The error analysis of the test results revealed that the random error was 21.6%, and the PST resulting from the sum of system errors was 1.1×10−8 at WACH1 and 4.2×10−9 at WACH2. The test accuracy met the requirements, demonstrating the feasibility and accuracy of the test method. The study presented in this paper offers a novel means to test the solar stray light suppression capability of heliospheric imager.
Most of the current visual training products available on the market use electronic screens to display objects of varying dimensions and distances, thereby stimulating the ciliary muscle through looking at the screen for visual function training. However, this method involves blue light radiation, which poses a potential hazard to the human eye. To address this issue, a visual optical system based on a Varifocal zoom structure has been designed. The system achieves continuous magnification of optical power by manipulating the lateral movement of two sets of lenses perpendicular to the optical axis. This simulates changes in object distance and stimulating ciliary muscle regulation training. This paper first derives the surface shape limits of variable focal length lenses, incorporates the variable focal length spherical effect equation to optimize the basic surface shape of Alvarez lenses, and uses Zemax software for design. The designed lens surface is characterized by a third-order XY polynomial free-form surface, with a maximum relative vertical axis offset of 5.6 mm between the two groups of lenses, achieving continuous magnification of refractive power between +4D and −8D. The design results indicate that the full-field modulation transfer function exceeds 0.3 at a Nyquist frequency of 30lp/mm, with root mean square (RMS) radius values approaching the Airy spot radius value and distortion below 2%. The imaging quality of this optical system is satisfactory.
In this paper, a method for vortex beam OAM detection using crosshair diffraction is proposed. The OAM-related main bright spot in the far-field distribution contains most of the energy of the incident beam (50%~84%) and there is no secondary bright spot that interferes with the detection. In contrast, the energy proportion of the main bright spot in the conventional small-hole diffraction method is extremely low, particularly in the far-field main bright spot above the 7th-order topological charge, which contains less than 1% of the energy of the incident beam. Furthermore, as the topological charge level increases, the secondary bright spot becomes more intrusive. Consequently, crosshair measurements are particularly applicable to the detection of weak vortex beams, which has potentially important implications for the development of long-range free-space optical communications.
A new type of 785 nm semiconductor laser device has been proposed. The thin cladding and mode expansion layer structure incorporated into the epitaxy on the p-side significantly impacts the regulation of grating etching depth. Thinning of the P-side waveguide layer makes the light field bias to the N-side cladding layer. By coordinating the confinement effect of the cladding layer, the light confinement factor on the p-side is regulated. On the other hand, the introduction of a mode expansion layer facilitates the expansion of the mode profile on the P side cladding layer. Both these factors contribute positively to reducing the grating etching depth. Compared to the reported epitaxial structures of symmetric waveguides, the new structure significantly reduces the etching depth of the grating while ensuring adequate reflection intensity and maintaining resonance. Moreover, to improve the output performance of the device, a new epitaxial structure has been optimized. Based on the traditional epitaxial structure, an energy release layer and an electron blocking layer are added to improve the electronic recombination efficiency. This improved structure has an output performance comparable to that of a symmetric waveguide, despite being able to have a smaller gain area.
To improve the processing efficiency of large-aperture optical components, a multi-robot, multi-tool collaborative processing method was proposed. A collaborative layout that has been tailored to the optical components was designed, and three feasible trajectories were simulated for analysis. The discrete simulation results were then used to establish principles for selecting trajectory parameters. To address the limitation of discrete simulation in capturing the influence of trajectory continuity on the surface map, an integral removal function model adapted to the motion mode was introduced. Furthermore, a collaborative machining obstacle avoidance strategy was developed. The experimental results obtained using the optimal trajectory demonstrated that with an initial surface shape of PV=18.310λ (λ=632.8 nm) and RMS=1.788λ, the final surface achieved PV=4.873λ and RMS=1.113λ. In addition, within the effective range of 120 mm diameter, PV=4.661 λ, RMS=0.857λ, converged to PV=2.465λ and RMS=0.622λ after processing. The total execution time was 3.943 hours, with the maximum execution time for a single processing unit being 2.041 hours, representing a 1.93-fold improvement over single-tool processing. This method significantly enhances processing efficiency, ensures surface shape accuracy, and holds great potential for the manufacturing of large-aperture optical components.
The Bi2O3/Bi2S3 heterojunction composite was prepared by thermal polymerization combined with room temperature solution method, and its micromorphology, crystal structure and elemental composition were characterized. The results demonstrate that the Bi2O3/Bi2S3 heterojunction composite exhibits a bulk morphology, accompanied by the presence of pores and a relatively rough surface. Based on the Bi2O3/Bi2S3 heterojunction composite, the photodetector was fabricated and its photodetection performance was measured under zero bias voltage. When exposed to ultraviolet (UV) light, the maximum photocurrent (0.32 μA) and response speed (65.65/80.56 ms) of the Bi2O3/Bi2S3 photodetector are significantly enhanced compared to those of the Bi2O3 photodetector. In addition, the device exhibits a wide photodetection band from the ultraviolet (UV) to the visible (Vis) spectrum, as well as fast and stable self-driven photodetection capability. This is mainly attributed the successful coupling of Bi2O3 and Bi2S3 with a narrow band gap, resulting in the formation of a heterojunction composite that exhibits a type II band structure. It is noteworthy that the photodetection performance of the device was measured by continuously alternating between blue light on and off for 100 times. This indicates that the Bi2O3/Bi2S3 photodetector exhibits excellent cycle stability.
A folding off-axis three mirror telescope has been used as the common optical path component in the design of an optical system suitable for a new airborne multispectral common aperture targeting pod. The optical system is characterized by miniaturization, high transmittance, multispectral, long focal length, and low difficulty of installation and adjustment. The designed multispectral common aperture optical system has an effective optical aperture of 220 mm, a near-infrared focal length of
With the wide application of holographic head-up display system and virtual reality augmented display technology, holographic reproduced images are required to be virtual images with higher quality, more realistic reproduction image size and more in line with human visual characteristics. Based on the principle of computer-generated holograms reproduction imaging, this paper used the Gerchberg-Saxton (GS) algorithm to iteratively solve the phase distribution of the original simulation images under different characteristic parameters (line width, ring diameter) and different calculated sampling intervals by performing direct and inverse Fourier transforms on the optical field distributions of the input and output planes, and the corresponding reproduced images were obtained by simulation calculation. The optical path of the holographic reproduction experiment was constructed by using the liquid crystal spatial light modulator, and the reproduction experiment was carried out by loading the phase distribution maps of different original simulation images, the holographic reproduction images of far-field diffraction were taken by the camera, and the actual feature size of the reproduced images was obtained by image processing. The experimental results show that the feature size of the reproduced images is basically linear with the characteristic size of the original simulation images. Furthermore, the reproduction image size shows a non-linear change relationship with the sampling intervals of the simulation calculation, which is consistent with the derived theoretical calculation relationship curve. In order to further verify the correctness of the conclusion, when the size of the expected reproduced image is designed as the ring diameter of 0.943mm and the line width of the central cross of 0.015mm. The characteristic size and sampling interval of the original simulation image of the expected target are obtained by the simulation calculation as the line width of 3pixel, the ring diameter of 594pixel and the sampling interval of 25μm, respectively. The ring diameter and line width of the holographic reproduction image, as measured by the reproduction experiment, are 0.93mm and 0.017mm, respectively. The error accuracy is within 0.02mm. The findings of this study provide an effective reference for application scenarios such as holographic display and AR/VR display to improve the authenticity of virtual display image size.
Soft polymer optical fiber (SPOF) has shown great potential in optical based wearable and implantable biosensors due to its excellent mechanical properties and optical guiding characteristics. However, the multimodality characteristics of SPOF limit their integration with traditional fiber optic sensors. This article introduces for the first time a flexible fiber optic vibration sensor based on laser interference technology, which can be applied to vibration measurement under high strain conditions. This sensor utilizes elastic optical fibers made of polydimethylsiloxane (PDMS) as sensing elements, combined with phase generating carrier technology, to achieve vibration measurement at 50~400 Hz within the strain range of 0~42%. 软聚合物光纤(SPOF)因其优异的机械性能和光导特性,在基于光学的可穿戴和可植入生物传感器中显示出巨大的潜力。然而,单点光纤的多模态特性限制了它们与传统光纤传感器的集成。本文首次介绍了一种基于激光干涉技术的柔性光纤振动传感器,可应用于高应变条件下的振动测量。该传感器利用聚二甲基硅氧烷(PDMS)制成的弹性光纤作为传感元件,结合相位发生载体技术,在0~42%的应变范围内实现50~260 Hz的振动测量。
Optical field manipulation, as an emerging frontier in photonics, demonstrates significant potential in biomedical microscopy, quantum state engineering, and micro-nano fabrication. Addressing the critical limitation of current optical modulation technologies in achieving full-parameter precision control, this study proposes a novel approach for dynamic azimuthal light field modulation using dual spiral arrays. By designing spatially interleaved spiral structures with differential initial radii while maintaining identical periodic parameters, we achieved continuous optical modulation spanning the full 0 - 2π range in azimuthal field distribution. Through rigorous numerical simulations, we systematically established the quantitative correlation between structural parameters and azimuthal light field patterns, revealing for the first time a quasi-linear relationship between radius difference and resultant optical distribution. This theoretical framework not only advances fundamental unde
为了减轻大气湍流对相干自由空间光通信的影响,本文提出了一种基于改进模拟退火算法的自适应光学系统,旨在优化系统的混频效率和降低误码率,从而提升整体系统性能。首先,介绍了含有无波前自适应光学部分的相干光通信系统的组成,并重点分析了混频效率和误码率等关键参数。随后,详细阐述了改进模拟退火算法的工作原理及其在自适应光学系统中的应用。为了验证算法的有效性,进行了数值模拟分析,并与传统算法进行了对比分析。最后,在实验平台上收集实际数据以进一步评估算法性能。实验结果表明改进模拟退火算法相比于普通模拟退火算法,迭代次数减少50%的情况下,误码率降低到10-9,混频效率提高到0.9。改进模拟退火算法可以减少传统自适应光学系统的迭代次数,提高波前校正的精度,满足通信系统的需求。
为实现光学传递函数的低成本、实时测量,本文提出基于哈特曼探测器的光学传递函数测量方法。首先,基于哈特曼探测器的测量波面,给出光学传递函数的测量方法。然后,设计传函测量光路,并给出焦深、像差和焦距测量的方法。同时,设计了物镜像差的标定光路,给出标定方法。最后,搭建实验光路,实现了单透镜的调制传递函数(MTF)、像差、焦距、焦深及色差的测量。结果显示,该方法实现了0-1° 视场透镜的MTF测量;透镜的像散、慧差及球差分别为0.114 λ、0.128 λ和0.02 λ;0°视场下透镜的色差在红、绿、蓝三个波长下分别为0.047 λ、0.055 λ、0.048 λ,1°视场下增长到0.117 λ、0.176 λ和0.154 λ;焦深为0.454 mm,误差2 %,焦距为74.6 mm,误差0.8 %。结果表明,该测量方法能够实现透镜的传函测量,为光学系统传函的低成本、实时测量提供技术途径。
光谱技术可以从大量的原始信号中提取有用的特征信息,直接用来分析和识别被观测样品的物质成分,在生物医药、食品安全、军事侦察中具有极高的应用价值。由于预处理目的与效果的不同,目前存在多种光谱预处理方法。根据目前方法使用时存在的问题,本文提出了一种基于多尺度小波变换的光谱数据预处理方法,并通过仿真光谱和实测光谱对提出算法和设计软件的性能进行了测试。仿真信号信噪比为0.5dB,经本文算法处理后,信噪比可达8.978dB;仿真中加入5种不同类型的基线,包括线型、高斯型、多项式型、e指数型、sigmoidal函数型,使用本文算法进行基线估计,估计值的均方根误差RMSE分别为0.3759、0.2883、0.6631、0.3489、0.4520;使用共聚焦显微拉曼光谱仪测量了聚四氟乙烯光谱,并用本文算法进行了预处理,结果表明证明该算法具有良好的可操作性,能够有效去除噪声和校正基线,并完整的保留谱峰信息,该算法为光谱数据预处理方法提供了新思路。
Diffractive waveguide, known for their lightweight, wide field of view, and large eyebox, have emerged as one of the most promising solutions for augmented reality (AR) near-eye display technologies. However, most commercially available AR waveguide simulation software is developed by foreign companies, and domestic advancements in 3D visualization software for optical waveguide design and simulation remain notably absent. To our knowledge, this work introduces the first domestically developed 3D visualization module for optical waveguide design and simulation based on ray-field tracing. Using this module, we engineered a two-dimensional exit-pupil-expansion diffractive waveguide, demonstrating a systematic design workflow. The workflow integrates
This paper investigates optical transport in metamaterial waveguide arrays (MMWAs) exhibiting Bloch-like oscillations (BLOs). The MMWAs is fabricated by laterally combining metal and dielectric layers in a Fibonacci sequence. By mapping the field distribution of Gaussian wave packets in these arrays, we directly visualize the mechanical evolution in a classical wave environment. Three distinct oscillation modes are observed at different incident positions in the ninth-generation Fibonacci structure, without introducing thickness or refractive index gradient in any layer. Additionally, the propagation period of BLOs increases with a redshift of the incident wavelength for both ninth- and tenth-generation Fibonacci MMWAs. These findings provide a valuable method for manipulating BLOs and offer new insights into optical transport in metamaterials, with potential applications in optical device and wave control technologies.
Atmospheric coherence length is a critical indicator of the impact of atmospheric turbulence on free-space optical communication links. This paper proposes a novel strategy for measuring atmospheric coherence length by utilizing extended targets as the information source. Specifically, the method integrates the wavefront structure function approach with the extended target offset algorithm to directly estimate the atmospheric coherence length. Traditional methods, such as the Differential Image Motion Monitor (DIMM), typically rely on guide star targets, which are difficult to set appropriately in horizontal communication links, thereby limiting their effectiveness in practical applications. In contrast, employing extended targets as direct detection targets provides a feasible solution for measuring atmospheric coherence length. The paper first reviews the principles and current research status of mainstream algorithms, emphasizing the reliance of existing algorithms on guide star targets and their limitations in horizontal links. Subsequently, we propose a new measurement scheme that combines the improved normalized cross-correlation algorithm with the wavefront structure function method to estimate atmospheric coherence length under extended targets scenarios. In comparison to traditional measurement methods, our approach enables coherence length measurement based on extended targets in horizontal links, thereby significantly reducing system complexity and equipment costs. To validate the effectiveness and measurement accuracy of the proposed method, both simulations and experiments were designed and conducted. The results demonstrate that the coherence length values measured by this method are highly consistent with those obtained using the DIMM method and the wavefront phase variance method, with a measurement accuracy error of approximately 4%. This indicates that the proposed method can effectively assess atmospheric coherence length, thereby providing a valuable reference for enhancing the reliability of free-space laser communication systems.
将非正则涡旋对引入部分相干光领域,利用Fraunhofer衍射积分公式研究了该光束在远场的空间相关奇点(SCS)和轨道角动量(OAM),详细探讨了非正则因子、离轴距离和涡旋符号对空间相关奇点的影响,研究了远场OAM谱、密度、检测与串扰几率。结果表明:不论是正则还是非正则涡旋对,SCS的位错数量总是等于拓扑荷的绝对值之和。尽管OAM模式与其功率权重的乘积之和等于拓扑荷的代数和,但是该关系对于非正则情况却不再成立。离轴距离、非正则因子或相干长度的变化会导致毗邻模相比于探测模具有更大功率,这也意味着串扰几率会大于中心探测几率。本文结果对基于OAM的光通信、光成像、光传感、光计算具有潜在的应用价值。
Division of Focal Plane (DoFP) polarization camera is a widely used integrated polarization imaging system. Crosstalk between pixels of Micro-Polarizer Arrays (MPAs) is a unique interference factor in such system, and its intensity varies with the polarization characteristics of incident light, thereby introducing errors into the measurement of the target's polarization information. This paper reviews the development of polarization crosstalk models and summarizes the factors affecting crosstalk identified in relevant research. Focusing on sensor parameters and optical system parameters as key factors, this study discusses the cause-effect model of crosstalk in cameras and its relation to temporal noise. It analyzes the results of the parameter changes caused by crosstalk, primarily summarizing the crosstalk's factor correlation, experimental repeatability, error randomness, and parameter calibration. Finally, this study prospects the future development trends of crosstalk models.
To achieve wide-area detection of space targets, this study designs an optical system design with a broad spectrum range (400 nm−
With the rapid development of bioluminescence technology, the demand for high-precision signal transmission has increased significantly. The spectral characteristic of the filter film, as the core component of the system, directly affects the accuracy of signal transmission. In this study, Nb2O5 and SiO2 were selected as high and low refractive index materials, respectively. A multi-channel negative filter was optimized using the Gaussian apodization function and Optilayer software. The filter film was deposited on a D263T substrate using an inductively coupled magnetron sputtering technique. The effect of thickness control errors on spectral shift and passband transmittance was addressed through inverse film sensitivity analysis. The effect of process parameters on film roughness was investigated, and it was found that adjusting the ICP power could effectively improve film roughness. When the developed multi-channel negative filter was tested at a 45° angle of incidence, the reflectance half-bandwidths of the center wavelengths of 576 nm, 639 nm, and 690 nm were 5 nm, 6 nm and 7 nm, respectively, with an average reflectance of about 98%. The average transmittance in the transmission ranges of 545−562 nm, 597−624 nm, 655−675 nm, and 708−755 nm was 92%. The multi-channel negative filter successfully passed both the environmental resistance test and the spectral stability test, thus meeting the application requirements of the multi-channel negative filter in the bioluminescence system.
Compared to traditional single-frequency bound states in the continuum (BIC), dual-band BIC offers higher degrees of freedom and functionality. Therefore, implementing independent control of dual-band BICs can further enhance their advantages and maximize their performance. This study presents a design for a dielectric metasurface that achieves dual-band BICs in the terahertz (THz) range. By adjusting two asymmetry parameters of the structure, independent control of the two symmetry-protected BICs is achieved. Furthermore, by varying the shape of the silicon holes, the design's robustness to geometric variations is demonstrated. Finally, the test results show that the figures of merit (FOMs) for both BICs reach 109. This work provides a new approach for realizing and tuning dual-frequency BICs, offering expanded possibilities for applications in multimode lasers, nonlinear optics, multi-channel filtering, and optical sensing.
Organic-inorganic hybrid lead-free perovskites have garnered significant attention due to their non-biotoxicity and environmental sustainability. Among these materials, MA3Sb2I9, with its stable zero-dimensional (0D) structure and lead-free nature, shows great promise for stable and efficient photodetection applications. In this study, we employ a MACl post-treatment to enhance the quality of MA3Sb2I9 perovskite thin films fabricated through antisolvent processing. This treatment facilitated the formation of Cl-Sb bond interactions between MACl and the perovskite thin films, effectively passivating the I− vacancies and grain boundary defects on the MA3Sb2I9 thin-film surface. This process not only improve the surface morphology and crystallinity of the thin film but also reduced the defect states density of the surface, thereby enhancing carrier extraction and transport efficiency. Consequently, the sensitivity of self-powered photodetectors based on the optimized thin-film preparation increased from 3.89 × 107 Jones to 5.72 × 108 Jones, representing an improvement by one order of magnitude. Furthermore, the rise and fall times were shortened from 37/76 ms to 31/37 ms, respectively, indicating an enhancement in the response speed of the devices.
The counter-rotating prisms Atmospheric Dispersion Corrector (ADC) has been widely used for the calibration of large-aperture astronomical telescopes. To achieve an optimal design method for the counter-rotating prism ADC, effectively compensate for dispersion, and suppress optical axis drift introduced by the ADC, this study establishes a vector model for ray tracing of the counter-rotating prism ADC based on traditional atmospheric dispersion compensation theory. The vector models of dispersion compensation and optical axis drift are then derived. Using this mathematical model, the impacts of ADCs with different parameters on the dispersion compensation, prism rotation angle, and optical axis drift are simulated and analyzed. The simulation results show that when compensating for the same atmospheric dispersion with different material combinations and bonding types, the rotation angle of the prism group remains relatively consistent, with differences increasing as the zenith angle increases. Choosing materials with similar refractive indices near the central wavelength reduces chromatic aberration in the ADC output light and improves dispersion compensation. When compensating for large dispersions at different zenith angles, the optical axis offset angle of the system decreases as the number of bonded surfaces increases. Specifically, each additional bonded surface can reduce the optical axis drift angle by one order of magnitude. In practical ADC design, dispersion can be effectively compensated, and optical axis drift can be suppressed by controlling the number of bonded surfaces and material selection.
Stripe projection technology is widely used in 3D measurement and surface morphology reconstruction, where phase quality is a critical determinant of measurement accuracy. However, the nonlinear relationship between input and output light intensity is a major source of phase error. To address this issue, this paper introduces a novel system nonlinear active correction method. This method captures the variation pattern between input and output light intensity by projecting a small number of uniform gray-scale images onto a standard plane. This pattern is then integrated with active system nonlinear correction to construct a system nonlinear model based on the input-output light intensity variation. Genetic algorithms are used to optimize the coding values, which are then used to actively correct the projected fringes via fringe coding. The corrected fringes effectively reduce the influence of nonlinear effects, thereby significantly improving the quality of phase acquisition. To validate the proposed method, computer simulations were performed using three-step phase shifting. The results showed an 88% reduction in the standard error and an 85.5% reduction in the maximum error. In actual standard plane experiments, the corrected standard phase error decreased from
In comparison with traditional photoelectric displacement measurement technologies, displacement measurement methods based on digital image processing methods exhibit superior fault tolerance and flexibility, making them a current research hotspot. To achieve high-precision and high-reliability angular displacement measurement, an image-based angular displacement measurement system based on Manchester coding is proposed. First, a single code-channel raster code disc was designed using Manchester coding based on M-sequence pseudo-random coding. A digital image sensor was then used to construct an optical path for capturing patterns on the raster code disc. Subsequently, a decoding recognition algorithm tailored to the coded patterns was developed. Additionally, edge positioning and sub-pixel subdivision algorithms for coded marker edge pattern fitting were proposed to further enhance the system’s resolution. The proposed method was then experimentally validated. The experimental results demonstrated that the system achieved a resolving power of 21 bits and an accuracy of 1.73 arcseconds with a 100 mm grating code disc. This research provides a foundation for the development of highly reliable and high-performance photoelectric angular displacement measurement technologies. Image-based angular displacement measurement system based on Manchester coding
Terahertz molecular fingerprinting is a promising method for label-free detection, particularly for micro or trace amount samples in practical applications. However, the wavelength of terahertz waves is much larger than the size of the molecules to be tested, resulting in a weak interaction between the waves and the matter. To address this challenge, additional structures are needed to enhance the absorption of electromagnetic waves by trace amount samples. In this study, we constructed an inverted asymmetric dielectric grating structure on a metal substrate. By utilizing guided-mode resonance (GMR) and a bound state in the continuum (BIC) effect, the terahertz absorption spectrum of thin film samples was significantly enhanced. The enhanced absorption spectra can be easily obtained by measuring the reflected absorption signal. The samples are coated on the flat back of the inverted dielectric grating, which simplifies the preparation process. For instance, when the thickness of an α-lactose film is 0.2 μm, the absorption enhancement factor reaches 236. This study provides a new method for detecting trace analytes in the terahertz band.
单一曝光时间或单一投影强度的条纹投影轮廓术(FPP)系统方法受限于相机的动态范围,会导致图像的过饱和和欠饱和,从而造成点云缺失或精度降低。为了解决这一问题,有别于投影仪像素调制方法,我们利用彩色投影仪三通道LED投影强度可单独控制的特点,提出了投影仪三通道光强分离的方法,结合彩色相机,实现了单曝光、多光强图像采集。进一步地,将串扰系数应用到被测物体三通道反射率预测中,结合聚类与通道映射,建立了投影仪三通道电流与相机三通道图像光强的像素级映射模型,实现了最佳投影电流预测和高动态范围图像获取。我们所提出的方法只需一次曝光就能实现高动态范围场景的高精度三维数据获取,该方法的有效性已通过标准平面和标准台阶的实验进行了验证,相比于现有单曝光高动态方法显著降低了平均绝对误差(44.6%), 相比于多曝光融合方法所需要的采集图像数量显著减小(文中场景下图片数量减小70.8%),提出的方法在各种 FPP 相关领域具有巨大潜力。
Multiple functional metasurfaces with high information capacity have attracted considerable attention from researchers. This study proposes a 2-bit tunable decoupled coded metasurface designed for the terahertz band, which utilizes the tunable properties of Dirac semimetals (DSM) to create a novel multilayer structure. By incorporating both geometric and propagating phases into the metasurface design, we can effectively control the electromagnetic wave. When the Fermi energy level of the DSM is set at 6 meV with 80 meV, the electromagnetic wave is manipulated by the DSM patch with the gold patch embedded in the DSM film, operating at a frequency of 1.3 THz and 1.4 THz. Both modes enable independent control of beam splitting under left-rotating circularly polarized (LCP) and right-rotating circularly polarized (RCP) wave excitation, resulting in the generation of vortex beams with distinct orbital angular momentum (OAM) modes. The findings of this study hold significant potential for enhancing information capacity and polarization multiplexing techniques in wireless communications.
在图像处理领域,合成孔径雷达(SAR)图像的分析因其广泛的应用而具有重要的作用。然而,这些图像往往受到相干斑点噪声的影响,严重降低了图像质量。传统的去噪技术通常依赖于滤波器设计,存在效率低下和适应性有限的问题。为应对这些挑战,本研究提出了一种基于增强残差网络架构的SAR图像去噪算法,旨在提高SAR图像在复杂电磁环境中的实用性。该算法集成了残差网络模块,直接利用噪声输入图像生成去噪输出,从而显著降低了计算复杂性以及模型训练的难度。此外,算法引入了自适应激活函数Meta-ACON,通过动态调整神经元的激活模式,增强了网络的特征提取能力。该去噪方法的有效性通过使用来自RSOD数据集的真实SAR图像进行实证验证,在EPI, SSIM, ENL保持优秀性能的同时,PSNR有了显著提升,相比于传统算法及深度学习算法,PSNR提高两倍性能以上。结果表明,该算法在减轻斑点噪声的同时,能够很好地保留图像中的重要特征。
Restoration of phase aberrations are crucial for addressing atmospheric turbulence involved light propagation.Traditional Zernike polynomial methods face high computational complexity and poor capture of high-frequency components, so we propose a Principal Component Analysis-based representation method. This paper analyzes factors affecting restoration accuracy, focusing on the size of sample space and sampling interval of D/r0 ,with r0 being the atmospheric coherence length and D being the pupil diameter, Results show PCA outperforms Zernike methods, especially in strong turbulence, and larger sampling intervals improve accuracy with less data.These findings pave a way to use PCs of phase aberrations with less orders than traditional ZPs to achieve data dimensionality reduction, and offer a reference to accelerate and stabilize the model based and deep learning based adaptive optics correction.
This study presents a sensitivity-enhanced tilt sensor based on femtosecond fiber Bragg gratings (FBGs). The sensor design follows static mechanics principles, where strain increases when displaced from the neutral axis. The novel use of femtosecond FBGs further enhances the sensor’s sensitivity and reliability compared to conventional FBGs. Finite element analysis (FEA) identified the optimal distance of 4.4 mm for maximum strain. A prototype sensor was manufactured and tested within a tilt range of -30° to 30°. Experimental results show an improved sensitivity of 129.95 pm/° and linearity of 0.9997. The sensor demonstrated repeatability (error < 0.94%), creep resistance (error < 0.30%), and temperature stability (error < 0.90%). Deployed in an underground pipeline project, it successfully monitored tilt highlighting its potential for structural health monitoring (SHM).
In order to solve the problem of RF discharge impedance matching of high-power fast axial flow CO2 lasers, an impedance matching network with low reflectivity and high dynamic matching range was designed to realize the efficient utilization of RF excited fast axial flow CO2 lasers under different discharge structures. Based on the impedance matching theory of RF circuits, a multi-electrode equivalent circuit model was constructed, a method of introducing tunable high-voltage ceramic capacitors into the matching network was proposed, and a dynamic L-type matching network suitable for high-power RF excited fast axial flow CO2 lasers was designed. The simulated dynamic L-type matching network can inject 60 kW RF power into 16 discharge tubes and achieve a reflectivity of less than 1% in the range of total load impedance of 12.81 Ω~49.94 Ω. A single-tube RF discharge experimental device was built, and the reflectivity of the dynamic L-type matching network was measured as less than 1% at 4 kW injection power, which was consistent with the simulation results. It is proved that the dynamic L-type matching network with adjustable high-voltage ceramic capacitors can achieve impedance matching in the high dynamic range, which meets the design requirements of high-power RF excited fast axial flow CO2 laser matching circuits.
Microdefects in cavity mirrors utilized in cavity ring-down spectroscopy (CRDS) adversely affect measurement accuracy. This paper establishes a microdefect scattering model grounded in Bobbert and Vlieger's Bidirectional Reflectance Distribution Function (BRDF) theory to analyze the characteristics of scattered light from microdefects under varying wavelengths, incident angles, defect sizes, types, densities, and substrate coatings. Studying the cavity mirror microdefect scattering model shows that defects in the micrometer to submicron range (100 um to 0.1 um) affect the ring-down absorption accuracy. Aiming at detecting microdefects of this order, this paper’s authors constructed analytical models of microdefect scattering and dark field detection of microdefects in cavity mirrors. Establishing and analyzing the scattering light model of CRDS mirror microdefects is critical to realizing the high-precision detection of CRDS mirror microdefects and recovering CRDS measurement accuracy.
For segmented detectors, surface flatness is critical as it directly influences both energy resolution and image clarity. Additionally, the limited adjustment range of the segmented detectors necessitates precise benchmark construction. This paper proposes an architecture for detecting detector flatness based on optical fiber interconnection. By measuring the dispersion fringes for coplanar adjustment, the final adjustment residual is improved to better than 300 nm. This result validates the feasibility of the proposed technology and provides significant technical support for the development of next-generation large-aperture sky survey equipment.
The Terahertz wave possesses characteristics of high penetration, low energy, and fingerprint spectrum, etc., making it widely used in the detection field. Therefore, developing a Terahertz wave detection optical imaging system holds substantial significance and wide application prospects. Firstly, we refer to the structure of Tessar objective lens, which consists four lenses. The balance equations of aberration for the system were established through the application of the aberration theory of the paraxial optical system. Subsequently, we provide a solution function and method of the initial structure parameters of the system. Then, we combine it with optical design software to further correct the aberration of the system. Finally, we design a Terahertz wave detection optical imaging system with a large aperture. The optical system consists of four coaxial refractive lenses with a total focal length of 70 mm, an F-number of 1.4, and a full field of view angle of 8°. The value of modulation transfer function (MTF) in the range of full field of view angle is greater than 0.32 at the Nyquist frequency of 10 lp/mm, and the root mean square (RMS) radius of the diffused spot in each field of view is less than the airy disk radius. Finally, the paper analyzes and discusses the various tolerance types of the system. The results indicate that the Terahertz wave detection optical imaging system, designed in this paper, has a large aperture, a simple, compact form, a lightweight structure, excellent imaging performance and simple processing, which meets the design requirements, and it has important applications in the field of high-resolution detection and other fields within the Terahertz wave band.
The optical frequency standard based on two-photon transition is expected to become a practical miniaturized optical frequency standard due to its significant advantages such as high stability, good reproducibility and easy miniaturization. In this paper, the basic principle of two-photon transition is briefly described, and the research status and progress of rubidium atomic optical frequency standards based on two-photon transition at home and abroad are introduced. Finally, it is concluded that the future development trends of rubidium atomic optical frequency standards based on two-photon transition are system miniaturization, performance improvement, integrated application and engineering.
Laser communication utilizes light waves as the transmission medium. It offers many advantages, including high data rates, expansive bandwidth, compactness, robust interference resistance, and superior confidentiality. It has the critical capability to enable high-speed transmission and secure operation of space information networks. Prominent research institutions have committed to studying a series of challenges that need to be solved in the process of networking laser communication technology, including point-to-multipoint simultaneous laser communication, all-optical switching and forwarding of multi-channel signals within nodes, node dynamic random access, and network topology design. Numerous demonstration and verification experiments have been conducted, with a subset of these research results finding practical applications. Based on the analysis and discussion of space laser communication networking technology, this paper summarizes the development of laser communication networking technology both domestically and internationally, focusing on the application of laser communication networking technology in the fields of satellite constellations, satellite relays, and aviation networks. Furthermore, it presents a review of pertinent domestic research methodologies, experimental validations, and technical solutions. Finally, it predicts the development trend of laser communication networking technology and applications.
This paper proposes a fiber-optic Fabry-Perot pressure sensor based on microelectromechanical systems (MEMS) technology for the measurement of transient pressures, including shock waves. The sensitive unit is composed of etched silicon wafers and BF33 glass wafers by anodic bonding, and the adhesive-free integration of the optical fiber and the sensitive unit is realized by laser fusion bonding technology. A signal demodulation experiment platform was constructed to comprehensively evaluate the pressure sensing characteristics of the sensors in static and dynamic pressure environments. The experimental findings demonstrate that the sensor exhibits a satisfactory linear response within the pressure range of 0−10 MPa, with a full-scale non-linear error of 0.41% and a hysteresis of 0.37%. Furthermore, the sensor demonstrated a rise time of 8.5 μs during dynamic pressure measurements. The sensor has the advantages of anti-electromagnetic interference, high consistency, low cost, and has a theoretical resonant frequency of 1.39 MHz, demonstrating the prospect of its wide application for dynamic pressure measurement in harsh environments such as explosion fields.
In order to simplify the support method of the mirror of a ground-based telescope and ensure the imaging quality and accuracy of the telescope, the optimization design of a uniaxial supported SiC mirror with 460 mm aperture was studied. First, a uniaxial support scheme for materials with similar linear expansion coefficients and a fan-shaped mirror back structure were determined. Advanced SiC sintering technology was used to prepare anisotropic structures according to the support structure and the material characteristics. Combined with optimization design theory, the mirror was designed to be lightweight while meeting the required accuracy. The optimized mirror weighs only 4.82 kg, and the RMS of the horizontal simulation analysis of the mirror is λ/51.4. After actual engineering verification, the accuracy detection results of the horizontal state under the mirror support are found to be better than λ/42. The lightweight effect is significant and meets the requirements of practical use. This research provides a theoretical foundation and technical reserve for engineering projects.
To address issues related to the accurate control of infrared band film thickness and precise wavelength positioning, we employ the LabVIEW programming language to develop a dynamic monitoring and compensation technology for optical film thickness, based on an optical film thickness monitoring system. Based on the principles of light interference and optical thin film design, a mathematical model is constructed using the photoelectric polarimetric method. We focus on resolving stopping errors and filtering noise at extremum points, thereby accurately restoring the real-time monitoring data of light intensity. The system achieves real-time and synchronous fitting of the film’s transmittance curve, calculates and fits the stopping point corresponding to the extremum of the film thickness. To validate the reliability and stability of the optical control system, a
In this paper, we investigate the transmission loss characteristics of gallium nitride (GaN) planar optical waveguides using a finite element simulation model based on the beam propagation method (BPM). To address the high transmission loss in conventional GaN waveguides, we propose process optimization solutions. By constructing a comprehensive transmission loss model, we systematically analyze the impact of waveguide geometric parameters on the transmission characteristics, with a particular focus on investigating the improvement effects of two optimization processes: top etching and back thinning. The experiment results indicate that both processes significantly reduce the waveguide transmission loss, with the top etching process reducing loss from 2.29 dB/mm to 0.19 dB/mm and the back thinning process reducing it to 0.24 dB/mm. Additionally, we analyze the impact of manufacturing defects, such as sidewall angles and surface roughness, on transmission loss. Through parameter optimization, we identify the key dimensions necessary for single mode light transmission. This study provides a theoretical basis and process guidance for the development of low-loss GaN waveguides.
This paper proposes a novel metric that integrates confidence scores of correspondences, obtained through a Triangle Voting (TV) method, with correspondence-based metrics. The proposed metric assumes that a good hypothesis aligns correspondences with high-confidence scores very closely, thereby yielding higher score contributions. We further introduce two enhancement to improve the effectiveness of inlier-based metrics with confidence scores: (1) ignoring the distance of inliers with minor transformation errors, and (2) suppressing the erroneous high-score contributions caused by numerous low-confidence correspondences. Comparative experiments conducted on three datasets demonstrate the superiority of the proposed metric over all previously known correspondence-based metrics. The proposed metric achieves registration performance enhancements ranging from 1% to 16.95% and time savings ranging from 1.67% to 10.79% under default parameter settings. Moreover, it strikes a better balance among time consumption, robustness, and registration performance. Specifically, the improved inlier count metric exhibits highly robust and accurate performance. In conclusion, the proposed metric can accurately identify the more correct hypothesis during the hypothesis evaluation stage of RANSAC, thereby enabling precise point cloud registration.
Owing to the low p-type doping efficiency in the hole injection layers (HILs) of GaN-based ultraviolet (UV) vertical-cavity surface-emitting laser (VCSEL), effective hole injection in multi-quantum wells (MQW) is not achieved, significantly limiting the photoelectric performance of UV VCSELs. We developed a slope-shaped HIL and an EBL structure in AlGaN-based UV VCSELs. In this study, by improving hole injection efficiency, the hole concentration in the HIL is increased, and the hole barrier at the electron barrier layer (EBL)/HIL interface is decreased. This minimises the hindering effect of hole injection. A mathematical model of this structure was established using a commercial software, photonic integrated circuit simulator in three-dimension (PICS3D). We conducted simulations and theoretical analyses of the band structure and carrier concentration. Introducing polarisation doping through the Al composition gradient in the HIL enhanced the hole concentration, thereby improving the hole injection efficiency. Furthermore, modifying the EBL eliminated the abrupt potential barrier for holes at the HIL/EBL interface, smoothing the valence band. This improved the stimulated radiative recombination rate in the MQW, increasing the laser power. Therefore, the sloped p-type layer can enhance the optoelectronic performance of UV VCSELs.
In this paper, a conventional soliton (CS) mode-locked erbium-doped fiber (EDF) laser was developed using MAX phase material (MAX-PM) Nb4AlC3 as a saturable absorber (SA). First, the liquid phase exfoliation (LPE) method was utilized to prepare Nb4AlC3 nanosheets, and then a piece of tapered fiber was adopted to fabricate Nb4AlC3-SA. It was found that the saturation intensity and modulation depth of the Nb4AlC3-SA are 2.02 MW/cm2 and 1.88 %. Based on the Nb4AlC3-SA, a conventional soliton (CS) mode-locked EDF laser was achieved. The central wavelength, pulse duration, and pulse repetition rate were found to be
During the propagation of high-power lasers within internal channels, the laser beam heats the propagation medium, causing the thermal blooming effect that degrades the beam quality at the output. The intricate configuration of the optical path within the internal channel necessitates complex and time-consuming efforts to assess the impact of thermal blooming effect on the optical path. To meet the engineering need for rapid evaluation of thermal blooming effect in optical paths, this study proposed a rapid simulation method for the thermal blooming effect in internal optical paths based on the finite element method. This method discretized the fluid region into infinitesimal elements and employed finite element method for flow field analysis. A simplified analytical model of the flow field region in complex internal channels was established, and regions with similar thermal blooming effect were divided within this model. Based on the calculated optical path differences within these regions, numerical simulations of phase distortion caused by thermal blooming were conducted. The calculated result were compared with those obtained using the existing methods. The findings reveal that for complex optical paths, the discrepancy between the two approaches is less than 3.6%, with similar phase distortion patterns observed. For L-type units, this method and the existing methods identify the same primary factors influencing aberrations and exhibit consistent trends in their variation. This method was used to analyze the impact of thermal blooming effect in a straight channel under different gravity directions. The results show that phase distortion varies with changes in the direction of gravity, and the magnitude of the phase difference is strongly correlated with the component of gravity perpendicular to the optical axis. Compared to the existing methods, this approach offers greater flexibility, obviates the need for complex custom analysis programming. The analytical results of this method enable a rapid assessment of the thermal blooming effect in optical paths within the internal channel. This is especially useful during the engineering design. These results also provide crucial references for developing strategies to suppress thermal blooming effect.
To address the high sensitivity measurement requirement of the test mass’s displacement in spaceborne gravitational wave detection, a ground-based simulation system using laser heterodyne interferometry has been established, initiating research into picometer-level displacement measurement techniques. Initially, the translational sensitivity of the designed laser heterodyne interferometer is tested under vacuum conditions. Subsequently, based on the sensitivity outcomes, noise source tracing research for the laser heterodyne interferometric system is conducted, including the development of a system noise model, analysis of various noise source mechanisms, and investigation of strategies to reduce the predominant noise sources. Ultimately, upon completion of the noise source tracing, the interferometric system is optimized, with tests indicating a displacement measurement sensitivity better than 1 pm/Hz1/2 in the range of 30 mHz to 1 Hz. This paper is expected to provide a reliable ground-based test platform for noise source tracing, facilitating the advancement of picometer-level laser interferometry technologies for spaceborne gravitational wave detection.
The Taiji program aims to achieve inter-satellite laser communication and absolute distance measurement using spread spectrum phase modulation technology based on the interferometric laser link. The selection of pseudo-random codes is the initial step in the design and implementation of the ranging and communication system, which requires comprehensive research and comparison of various aspects, including the implementation principles, correlation properties, and ranging error functions associated with different pseudo-random codes. This paper first elucidates the generation principles of m-sequences, Gold sequences, and Weil sequences. Pseudo-random sequences are generated using different hardware structures such as Fibonacci, Galois, and register addressing. The hardware circuits for Gold and Weil sequence generation are implemented on an FPGA development platform. The GPS C/A code is used as the Gold sequence, which facilitates its comparison and analysis with the Weil sequence. An analysis of the resource consumption and complexity of different hardware implementation methods is performed. Then, correlation values and root mean square errors are calculated to compare the pseudorandom noise performance of the Gold and Weil sequences. Finally, an error function for ranging is constructed based on the ranging principles and the intersymbol interference phenomenon after laser interference. This function is then compared with the ideal error function to evaluate the advantages and disadvantages of using different pseudorandom codes for ranging. The analysis reveals that Weil sequences demonstrate superior performance, exhibiting a sidelobe range of −60.27 dB to −24.01 dB, an autocorrelation rms of 0.303, and a cross-correlation rms of 0.307, outperforming Gold sequences in all metrics. Additionally, Weil sequences require only 30% of the hardware resources of Gold sequences and have a smaller error function deviation. Weil sequences are better suited to the laser ranging and data communication requirements of the Taiji program.
The traditional Pound-Drever-Hall (PDH) technique utilizes analog devices to actively stabilize the frequency of lasers. However, this results in a bulky system and a rigid control process, making it difficult to meet the requirements of miniaturization and automation of the frequency stabilization system for new applications such as space gravitational wave detection. In this paper, an automatic peak-finding algorithm based on backward difference is specifically designed for frequency discrimination signal peak search, which effectively reduces human intervention in the frequency stabilization process. This method identifies the main signal peak and controls state switching by comparing the time width of consecutive signal peaks. Moreover, it avoids the inherent drawbacks of the conventional thresholding method. We have also designed and built a digital frequency stabilization system based on a field-programmable gate array (FPGA). This system digitizes and integrates the discrete components of the stabilization servo feedback control into a single FPGA, forming a fast servo feedback loop with a piezoelectric actuator. The digital frequency stabilization system first obtains the frequency discrimination signal locally through an amplitude demodulation, and then achieves automatic peak-finding through the designed backward difference algorithm. Finally, the servo controller is activated at the lock-in point, and an incremental digital PID algorithm is used to successfully lock the frequency of a commercial Nd:YAG laser to a resonance of a 10 cm Fabry-Pérot cavity with a finesse of
To meet the picometer-level ranging accuracy requirements for space-based gravitational wave detection, this paper proposes an optimization method for the inter-spacecraft optical metrology noise link metrics. The method optimizes the design parameter to ensure the inter-spacecraft ranging accuracy while improving the technical feasibility of the spacecraft design. Firstly, the design parameters and objective functions of the optimization problem are clearly defined, and Sobol sensitivity analysis is used to effectively identify the key parameters. Subsequently, the optimization problem is solved using the Non-dominated Sorting Genetic Algorithm II (NSGA-II), from which the optimal solution is selected from the Pareto front based on the requirements. On this basis, the design metrics for each parameter are determined, and an initial metric tree is constructed. Simulation experiments verify the feasibility of the method. The results show that by optimizing the noise link metrics in accordance with the proposed approach, it is possible to achieve an optical metrology noise level of 8 pm/
The Taiji space gravitational wave detection mission employs laser interferometry to measure picometer-level distance variations induced by gravitational waves. Attitude jitter in both satellites and movable optical subassemblies (MOSA) generates tilt-to-length (TTL) coupling noise that critically degrades detection sensitivity. Therefore, it is necessary to fit and subtract TTL noise during the data processing stage. To address this challenge, we propose an iterative TTL noise suppression algorithm for post-processing. First, a first-order linear approximation model of TTL noise is established and incorporated into the time-delay interferometry (TDI) combinations to derive its expression in TDI outputs. We subsequently perform initial maximum likelihood estimation of the TTL coupling coefficients, subtract the preliminary TTL noise estimate from the TDI data to characterize the residual baseline noise statistics, and reincorporate these statistics into the updated likelihood function for subsequent TTL coefficient estimation. Through ten iterative cycles, we achieve a refined baseline noise model. Finally, The posterior distribution of the TTL coefficients is obtained via the Markov Chain Monte Carlo (MCMC) method, thereby accomplishing the precise fitting of the TTL noise and consequently achieving effective noise suppression. Results demonstrate that over 80% of estimated coefficients fall within three standard deviations, and more than 80% of the coefficient estimates deviate from the true values by less than 0.1 mm/rad. For various levels of TTL coefficients, the residual TTL noise after suppression is one order of magnitude lower than the secondary noise, demonstrating a certain degree of robustness. This is particularly applicable to real detection scenarios where the noise floor model is unknown, meeting the requirements for space-based gravitational wave detection.
To precisely evaluate the noise induced by magnetic field and magnetic field gradient fluctuations acting on the test masses in space gravitational wave detection missions, a Multi-stage Bias Correction Model (MSBCM) is proposed for the accurate reconstruction of the magnetic fields at the test mass. Based on the ensemble learning method, the standard fully connected neural network modules and residual fully connected neural network modules are constructed as weak predictors for the MSBCM. Each weak predictor sequentially corrects the prediction biases from the preceding model, cumulatively forming a robust predictive model to realize precise magnetic field reconstruction at test mass locations. Magnetic field reconstruction experiments conducts on the LISA Pathfinder, eLISA, and Taiji-2 space gravitational wave detection spacecraft, and the proposed MSBCM method demonstrates the lowest mean relative errors along sensitive axes in comparison with other interpolation or estimation methods. In simulating on-orbit experiments, the MSBCM method achieves the root mean square error of magnetic field fluctuations and gradient fluctuations in acceleration noise on the sensitive axis of test mass 1 of 1.68×10−17 (m/s2/Hz1/2) and 4.00×10−17 (m/s2/Hz1/2), respectively. Additionally, MSBCM closely only to the distance weighted method in minimizing the root mean square error for magnetic field fluctuations and gradient acceleration noise on the sensitive axis of test mass 2, records at 1.72×10−16 (m/s2/Hz1/2) and 2.93×10−16 (m/s2/Hz1/2), further validating the advantages of the proposed method in assessing magnetic fields around test masses in space-based gravitational wave detection missions.
High-precision inertial sensors have broad application prospects in fields such as aerospace, navigation, and precision measurement. However, the accurate evaluation of noise in these sensors is imperative for optimal performance, with residual gas noise being a significant source of noise in inertial sensors. The current methods for calculating the level of residual gas noise lack numerical simulations based on the actual structure of inertial sensors, which hinders the ability to meet the demands of high-precision noise analysis. This paper proposes a novel residual gas noise simulation method based on ray tracing technology. Firstly, the method simulates the trajectories of residual gas inside the electrode cage of the inertial sensor under orbital conditions using a real inertial sensor model to obtain the statistical characteristics of the residual gas acceleration noise. Secondly, the influence of different pressures and temperatures on the residual gas noise is investigated. Finally, the dependence of the residual gas noise on the gap size of the non-sensitive axis is analyzed. The simulation results demonstrate the efficacy of Ray Tracing technology in simulating and tracking the interaction between the residual gas and the sensitive structures, achieving a high-precision simulation of residual gas acceleration noise at the level of 10−15. Temperature and pressure have been shown to significantly affect the level of residual gas acceleration noise, and reducing the gap between the electrode cage and the test mass will increase the power spectrum of the residual gas noise in the inertial sensor.
Deep Frequency Modulation (DFM) interferometry is an effective approach for simplifying laser interferometry systems in space gravitational wave detection. However, the conventional use of kHz-level modulation frequencies in current DFM techniques introduces coupling of laser power noise into the system, which increases background noise and limits the ability to meet the stringent requirements of high-precision space measurements. This paper proposes to increase the DFM modulation frequency to the MHz range to mitigate the effects of laser power noise. Through an in-depth analysis of the DFM technique, we developed a phase signal extraction method for DFM interferometry using Bessel function expansion, orthogonal demodulation, and promotion of J1···J4 method. Based on the signal processing requirements at the MHz-level, the hardware and software architecture of a phase measurement system was developed, followed by extensive testing and evaluation under various operating conditions. The results demonstrate that the phase measurement system exhibits excellent linearity and accuracy, with phase noise in the frequency band from 2 mHz to 1 Hz consistently below 2π µrad/
The coupling noise between test mass stiffness and displacement, as a significant component of the residual acceleration noise, critically impacts the performance of space gravitational wave detection, making stiffness identification essential for validating and optimizing control strategies and meeting the noise suppression requirements. For non-coaxial test mass configurations, this paper proposes a novel identification method based on dual sensitive axis decomposition. First, a relative dynamic model between the test mass and the spacecraft is constructed, and the model parameters are decomposed along the dual sensitive axis to isolate the influence of spacecraft acceleration disturbances and predominant angular acceleration disturbances on the on-orbit identification. Second, utilizing on-board laser interferometers, inertial sensors, and associated control loops, an on-orbit identification scheme is designed and a stiffness identification method using recursive least squares is proposed. Finally, numerical simulations are performed to verify the performance of the method. The experimental results demonstrate that the proposed stiffness identification method can effectively identify the stiffness of the test mass on the sensitive axis. Under the given simulation conditions, the mean absolute error is less than 5×10−9 s−2, the root mean square error is less than 1.5×10−8 s−2, and the maximum steady-state error is less than 2×10−9 s−2. These findings suggest that the method can be applied to future gravitational wave science missions.
As a follow-on mission to the GRACE low-low satellite-to-satellite tracking gravity mission, one of the twin satellites of laser ranging interferometer gravity mission GRACE Follow-On experienced an anomaly in its accelerometer payload after one month of operation. This anomaly resulted in the loss of scientific measurement data, a situation similar to the final phase of the GRACE. Therefore, research on accelerometer data recovery is important to achieve the detection objectives of both GRACE and GRACE Follow-On. This paper proposes a novel method for accelerometer data recovery and reconstruction based on the Echo State Network in machine learning. By constructing a mapping relationship of accelerometer data between the twin satellites using the Echo State Network and improving the network performance through Bayesian optimization, this method can achieve high-precision and high-efficiency reconstruction of missing accelerometer data. Through experimental comparison with measured data, in the frequency band of gravity field detection, the prediction results in the along-track and radial directions have been shown to reach the level of
The space-based gravitational wave detection need to use laser acquisition technique to construct the inter-satellite laser link, and the spot center positioning is the core technique for measurement in the laser acquisition phase. Taking the Taiji program for example, the spot center positioning precision should be less than 0.1 pixel. However, the receiving laser intensity is nearly 100 pW at the detector surface due to the long-distance propagation. The precision of most of the conventional positioning methods is significant degraded under low signal-to-noise ratio conditions, so it is crucial to study how detector noise affects the spot center positioning precision. To address these challenges, we first elucidate the operational principles of laser acquisition and pointing technique, then theoretically analyze the mechanism by which the background noise of CMOS affects the spot center positioning precision and introduce an improved spot center positioning algorithm. Finally, the coupling relationship between different system parameters and the background noise of CMOS is measured through the experiment. The experimental results agree with the theoretical analysis, validating the correctness of the noise model and proving that this algorithm can achieve the measurement precision of 0.018 pixel under weak light conditions.
A space laser interferometric gravitational wave observatory requires spaceborne clocks with ultralow phase noise in the millihertz frequency band. Such noise can be suppressed using a sideband multiplication transfer scheme and pilot tone techniques. To meet the requirements of the clock noise suppression technique, ultralow residual phase noise synthesizers are required to generate the microwave (2.4 GHz) for electro-optic modulator modulation and the pilot tone signal (75 MHz). To this end, two different structures of microwave chains have been designed, implemented and compared. The application of low phase noise phase-locked dielectric resonator oscillators (PDROs) and frequency division techniques enabled the development of a frequency synthesis chain with ultralow residual phase noise. The residual phase noise of the 75 MHz pilot signal is measured to be
To address the measurement errors introduced by laser linewidth in the traditional swept-frequency methods, a signal analysis approach based on convolution fitting is proposed, leveraging the convolutional characteristics of Guassian-shaped laser spectrum and Lorentzian-type Fabry-Perot (F-P) cavity. An swept-frequency optical fiber experimental platform is constructed to verify the performance of the two F-P cavities (one is custom-built (Cavity 1) and another is commercial (Cavity 2)) . Firstly, the impact of laser linewidth on the signal profile is quantified through simulations, and the main process of the fitting algorithm is introduced. Secondly, the spectrum of the incident laser is measured via beat-frequency analysis. The experimental results indicated that the spectrum exhibited a Gaussian shape with a linewidth of (11.59 ± 1.23) kHz. Subsequently, the frequency modulation error of the swept-frequency platform is evaluated. Linewidth measurements are conducted on the cavity 1 and cavity 2 using the swept-frequency method. For Cavity 1, the results of Lorentzian fitting and convolutional fitting are (204.1 ± 11.2) kHz and (203.9 ± 11.2) kHz, respectively, showing no significant difference. For Cavity 2, which had a calibrated linewidth of 4.17 kHz, the result of Lorentzian fitting is (8.97 ± 0.42) kHz, while the result of convolutional fitting is (4.42 ± 0.50) kHz. The experimental results demonstrate that when the laser linewidth is comparable to the cavity’s linewidth, this method can accurately measure the true linewidth of the cavity. When the laser linewidth (11.59 kHz) is significantly smaller than the cavity’s linewidth (204.1 kHz), the results obtained using this method are similar to those from the Lorentzian fitting approach. This work broadens the range of options for selecting linewidth measurement equipment for narrow-linewidth Fabry-Pérot (F-P) cavities.
Addressing the issue of beam alignment with Fabry-Pérot cavities, this paper proposes an adaptive dual-mirror step adjustment method based on the gradient ascent of transmitted resonant mode energy to achieve cavity coupling. First, leveraging the relationship between the reflection angles of the dual mirrors and the beam pointing, independent adjustment of the incident beam position and angle was proposed. Second, the EfficientNet neural network was used to classify resonant mode images, enabling identification of different mode images. Third, the energy gradient of the cavity mode was utilized for adaptively dual mirrors step adjustment, enabling low-cost and efficient cavity coupling of both fundamental and higher-order modes. The beam pointing adjustment method proposed will offer a novel solution for coupling lasers with Fabry-Pérot cavities in ultra-stable lasers and gravitational wave detection.
To achieve high-precision residual stress detection in key components in precision manufacturing, an electro-optic modulated ellipsometric stress sensing system has been established. This study focused on the ellipsometric signal response of common 304 stainless-steel materials in engineering under uniaxial tensile stress conditions. Firstly, based on the fundamental principles of reflection ellipsometry, the relationship between the ellipsometric signal and the ordinary and extraordinary refractive indices was established for different optical axis directions. Secondly, the working point of ellipsometric stress sensing was optimized for stainless steel materials. By comparing the ellipsometric signals at the extinction point and the non-zero linear working point, it was demonstrated that the non-zero linear condition is suitable for stress signal sensing. Finally, the stress-induced ellipsometric signals were measured under different optical axis directions. The experimental results indicate that for 304 stainless steel, the system's minimum stress detection limit is 7.84 kPa, and the stress detection accuracy of the system is better than 7.84 kPa. This system can be utilized for high-precision stress detection requirements in metal workpieces in precision manufacturing.
Quantum noise is one of the main noises affecting the laser interferometric gravitational wave detection. To cope with quantum noise and further improve detection sensitivity, this paper applies the quantum transfer function method to rederive the source attribution of quantum noise in conventional Michelson interferometers. The findings reveal that for two types of quantum noise-radiation pressure noise and shot noise-radiation pressure noise can be directly attributed to the amplitude quadrature fluctuations of vacuum fluctuations at the unused port of the interferometer, while shot noise can be completely attributed to the phase quadrature fluctuations at the unused port only under certain conditions. Provided that the source attribution of the quantum noise is clearly known, the squeezed light technique can improve the sensitivity of detectors. However, when adopting unequal arm interference detection schemes, attention must be paid to the length difference between the two unequal arm lengths.
For space-borne gravitational wave detection missions based on the heterodyne interferometry principle, tilt-to-length (TTL) coupling noise is an important optical noise source, significantly influencing the accuracy of the measurement system. We present a method for analyzing TTL coupling noise under the joint influence of multiple factors. An equivalent simulated optical bench for the test mass interferometer was designed, and Gaussian beam tracing was adopted to simulate beam propagation. By simulating the interference signal, it can analyze the impact of various factors on the TTL coupling noise, including positional, beam parameters, detector parameters, and signal definition factors. On this basis, a random parameter space composed of multiple influential factors was constructed within a range satisfying the analysis requirement, and the corresponding simulation results from random sampling were evaluated via variance-based global sensitivity analysis. The calculated results of the main and total effect indexes show that the test mass rotation angle and the piston effect (lateral) significantly influence the TTL coupling noise in the test mass interferometer. The analysis provides a qualitative reference for designing and optimizing space-borne laser interferometry systems.
To detect space gravitational waves in the extremely low-frequency band, the telescope and optical platform require high stability and reliability. However, the cantilevered design presents challenges, especially in the glass-metal hetero-bonding process. This study focuses on the analysis and experimental research of the bonding layer in the integrated structure. By optimizing the structural configuration and selecting suitable bonding processes, the reliability of the telescope system is enhanced. The research indicates that using J-133 adhesive achieves the best performance, with a bonding layer thickness of 0.30 mm and a metal substrate surface roughness of Ra 0.8. These findings significantly enhance the reliability of the optical system while minimizing potential risks.
The optical frequency standard based on two-photon transition is expected to become a practical miniaturized optical frequency standard due to its significant advantages such as high stability, good reproducibility and easy miniaturization. In this paper, the basic principle of two-photon transition is briefly described, and the research status and progress of rubidium atomic optical frequency standards based on two-photon transition at home and abroad are introduced. Finally, it is concluded that the future development trends of rubidium atomic optical frequency standards based on two-photon transition are system miniaturization, performance improvement, integrated application and engineering.
Laser communication utilizes light waves as the transmission medium. It offers many advantages, including high data rates, expansive bandwidth, compactness, robust interference resistance, and superior confidentiality. It has the critical capability to enable high-speed transmission and secure operation of space information networks. Prominent research institutions have committed to studying a series of challenges that need to be solved in the process of networking laser communication technology, including point-to-multipoint simultaneous laser communication, all-optical switching and forwarding of multi-channel signals within nodes, node dynamic random access, and network topology design. Numerous demonstration and verification experiments have been conducted, with a subset of these research results finding practical applications. Based on the analysis and discussion of space laser communication networking technology, this paper summarizes the development of laser communication networking technology both domestically and internationally, focusing on the application of laser communication networking technology in the fields of satellite constellations, satellite relays, and aviation networks. Furthermore, it presents a review of pertinent domestic research methodologies, experimental validations, and technical solutions. Finally, it predicts the development trend of laser communication networking technology and applications.
This paper presents various aspects of atmospheric refraction to gain insight into the advances in this field. It divides the effects of atmospheric refraction into two categories: the visible-to-infrared bands used in research fields such as optical imaging, laser transmission, and optoelectronic tracking and the radio band used in radar measurements and satellite detection. The calculation formulas for these two bands are different in their practical treatment. This paper introduces the refractive index formulas according to the refractive index formula's development history and points out the limitations of each formula. The current best choice for the former formula is the one summarized by Rüeger scholars; for the latter, it is recommended to choose the radio refractive index formula in the Rec. ITU-R P.453-14. In addition, the relationship between the refractive index of the Earth's surface and altitude, reference data for the refractive index on a global scale, and statistical distributions for the calculation of the refractive index gradient are given in the recommendation. Finally, traditional calculation methods for obtaining atmospheric refraction and optical observation methods are presented. The former study is based on the modeling of atmospheric patterns or meteorological data, formulae for refractive indices in specific regions, or model fitting to satisfy accuracy in a single environment or on an average scale. The optical measurement method does not need an atmospheric model as a basis, nor does it rely on meteorological parameters. The measurement results of the data are real-time and more representative of the path. It can make up for some of shortcomings of the traditional methods, and is more in line with future development trend of the future.
In non-Hermitian systems, controlling the gain or loss of the system can enable the system state transition from PT-symmetry to broken PT-symmetry. This transition leads to a special point known as the exceptional point, where the system eigenvalues and eigenstates become simultaneously degenerate. When combined with metasurfaces, the exceptional point leads to various intriguing optical phenomena, such as asymmetric transmission, exceptional topological phase, and the non-Hermitian skinning effect. However, active metasurfaces introducing gains are difficult to realize experimentally. Therefore, designing passive metasurfaces using equivalent gains through loss becomes a powerful tool in non-Hermitian research. In this paper, we review the theoretical models, research progress, specific applications, and experimental design in the study of the exceptional point on passive non-Hermitian metasurfaces and look forward to the future direction of this field.
The data simulation for Space Situational Awareness (SSA) can provide critical data support for the development, testing, and validation of space surveillance equipment and situational awareness algorithms (including detection, tracking, recognition, and characterization of space object), playing a significant role in building SSA capabilities. Taking the optical data simulation for space-based situational awareness as the research subject, the purpose and main research content of SSA data simulation are presented, and the typical research methods and processes of SSA optical imaging simulation are set forth. The current research status and progress in domestic and foreign related research are introduced, covering the imaging modeling and simulation achievements of different optical sensing systems such as binocular vision sensors, LiDAR, infrared sensors, visible light telescopes, and star trackers. The development trend of SSA data simulation research is analyzed, providing reference for future research ideas and approaches of SSA data simulation.
Fringe structured light technology is a non-contact measurement method, which has developed rapidly in recent years and provides a new solution for on-machine detection in mechanical processing. However, the accuracy of structured light for on-machine detection is compromised by the convoluted lighting in machining environments and metal parts’ high reflectivity, leading to inaccurate measurements. Applying high dynamic range (HDR) technology to structured light detection can reduce the effect of high reflectivity, achieving the measurement of metal parts in complex scenes. This paper introduces the measurement principle of structured light and summarizes the challenges of on-machine detection for HDR structured light. Subsequently, this paper provides a comprehensive review of HDR structured light technology. In the context of on-machine detection of mechanical processing, the HDR technology based on hardware equipment and the HDR technology based on stripe algorithm are discussed and analyzed, respectively. Following this, different technologies are summarized according to the requirements of on-machine detection. The advantages and disadvantages of various methods are presented, and the applicability of on-machine detection is compared. Finally, the potential applications are analyzed, and the technological prospects will be proposed in combination with the research hotspots of advanced manufacturing technology and precision measurement in recent years.
Laser Induced Breakdown Spectroscopy (LIBS) is a new method for qualitative and quantitative analysis of the constituents of a material using plasma spectra produced by the interaction of a strong pulsed laser with the material. In the process of pulsed laser-induced plasma, different laser parameters (energy, pulse width, wavelength), environmental conditions during the detection process and the properties of the material itself have different degrees of influence on the physical mechanism of laser-induced plasma, which in turn affects the results of LIBS quantitative analysis. We review the physical mechanisms of LIBS technology in the current state, including the basic principles of LIBS, the differences in laser parameters, and the physical mechanisms involved in the differences in environmental and material properties. It provides a basis for a deeper understanding of laser-matter interactions and for improving the detection capabilities of LIBS.
Narrow linewidth fiber lasers, based on the multi-longitudinal-mode oscillator seed source, have obvious advantages in engineering applications and space-limited loading platforms. Additionally, they are considered ideal sub-modules for high-power spectral combinations. The time domain of this type of seed is unstable due to the self-pulse effect, causing significant spectral broadening and stimulated Raman scattering effects during the amplification process, which limits their further improvement in output power and affects the purity of laser spectra. In this paper, we introduce four commonly used narrow linewidth seeds. The mechanism and suppression methods of the self-pulse effect in multi-longitudinal mode oscillator seeds are analyzed. Critical technologies essential for the optimization and relevant progress of the multi-longitudinal-mode oscillator seed source and amplifier stages are discussed in detail. A future development outlook is also presented. This paper serves as a useful reference for the design of narrow linewidth fiber lasers based on the multi-longitudinal-mode oscillator seed source.
Optical path absorption spectroscopy is an important branch of absorption spectroscopy. In recent years, there has been a proliferation of optical path absorption spectroscopy techniques based on different light source technologies, absorption cavity technologies, and detection methods. As the demands on detection sensitivity and absorption optical path length increased, optical path absorption spectroscopy techniques based on the principle of enhanced absorption emerged, including integrated cavity spectroscopy (ICOS), cavity-enhanced absorption spectroscopy (CEAS) and cavity ring-down spectroscopy (CRDS). Enhanced absorption spectroscopy is advantageous for its high spectral resolution, high sensitivity, fast response time, and portability, but it presently lacks a unified concept and clear classification criteria. This paper compares the development history of absorption spectroscopy techniques and clarifies the concept of their multi-optical path. Based on whether resonant absorption occurs in the absorption cavity, the concept of absorption spectroscopy techniques based on resonance is proposed, and the current research status of resonant absorption spectroscopy techniques is analyzed and summarized, and the applications of this technique in various fields are outlined. Finally, the future development of key technologies in resonance absorption spectroscopy is envisioned.
Optical fiber tweezers are widely used in biochemical analysis, life sciences, and other fields due to their simple structure, flexible operation, and compact size. The hetero-core structure of the optical fiber probe possesses inherent advantages in near-field evanescent wave optical trapping force, core beam coupling transmission, and cross-synergistic application of microfluidic technology, which can realize the functions of cell and subcellular particle collection and transportation, and can significantly improve the three-dimensional particle trapping capability as well as dynamic manipulation level. In this paper, the structural characteristics and application technology research progress of optical fiber tweezers based on different core structures are reviewed. This paper sorts and compares key technologies, including probe preparation, laser source, and coupling mode, in hetero-core optical fiber tweezers systems. It also summarizes and provides a perspective on the role and development of hetero-core fibers with different structures in optical fiber tweezers.
Micro-LEDs offers the benefits of high brightness, high response frequency, and low power consumption, making them an attractive candidate for future display technologies and Visible Light Communication (VLC) systems. Nonetheless, their low External Quantum Efficiency (EQE) currently impedes their scaled mass production and further applications. In order to break through the bottleneck of low EQE, we conducted an analysis of Micro-LED external quantum efficiency’s contributing factors. The influencing factors for EQE are analyzed. It is concluded that the carrier loss and non-radiative recombination caused by sidewall defects are the main reasons for the decrease in EQE. In addition, we summarized the impact of sidewall defects on carrier transport and composites, and we also reviewed the commonly used sidewall treatment technology and repair methods, and pointed out that the existing sidewall treatment methods are helpful but insufficient for improving EQE, and the mechanism of carrier interaction with sidewall defects is not very clear. It is suggested to carry out a thorough and systematic study on the types and distribution of sidewall defects, the mechanism of carrier and sidewall defects, and the defect repair mode in the sidewall treatment process. Finally, future development trends are projected. This paper offers design ideas and theoretical foundations to enhance the external quantum efficiency and accelerate the process of commercialization and mass production of Micro-LEDs.
Polarization imaging, a novel photoelectric detection technology, can simultaneously acquire the contour information and polarization features of a scene. For specific application scenarios, polarization imaging has the excellent ability to distinguish different objects and highlight their outlines. Therefore, polarization imaging has been widely applied in the fields of object detection, underwater imaging, life science, environmental monitoring, 3D imaging, etc. Polarization splitting or the filtering device is the core element in a polarization imaging system. The traditional counterpart suffers from a bulky size, poor optical performance, and being sensitive to external disturbances, and can hardly meet the requirements of a highly integrated, highly functional, and highly stable polarization imaging system. A metasurface is a two-dimensional planar photonic device whose comprising units are arranged quasi-periodically at subwavelength intervals, and can finely regulate the amplitude and phase of the light field in different polarization directions. Polarization devices based on metasurface are featured with compactness, lightweight and multi-degree freedom, offering an original solution to ultracompact polarization imaging systems. Targeted at the field of polarization imaging, this paper illustrates the functional theory, developmental process and future tendency of related metasurfaces. We discuss the challenges and prospect on the future of imaging applications and systematic integrations with metasurfaces.
In order to clarify the cavity design methods of thin-disk multi-pass amplifiers, we summarize the different types of thin-disk multi-pass amplifiers and concludes that there are four fundamental design concepts: (1) 4
Miniature head-mounted single-photon fluorescence microscopy is a breakthrough approach for neuroscience research that has emerged in recent years. It can image the neural activity of freely moving vivo animals in real time, providing an unprecedented way to access neural signals and rapidly enhancing the understanding of how the brain works. Driven by the needs of brain science research, there have been many types of miniature head-mounted single-photon fluorescence microscopes, such as high-resolution imaging, wireless recording, 3D imaging, two-region imaging and two-color imaging. In order to have a more comprehensive understanding of this new optical neuroimaging technology, we classify its technologies according to the imaging field of view, introduce the characteristics of different types of micro-head-mounted single-photon fluorescence microscopes reported so far, and focus on the optical system scheme and optical performance parameters used. The advantages and disadvantages of different schemes are analyzed and compared and the future direction of development is described to provide reference for the practical application of brain science researchers.
Non-line-of-sight (NLoS) imaging is a promising technique developed in recent years, which can reconstruct hidden scenes by analyzing the information in the intermediate surface, and "see around the corner", and has strong application value in many fields. In this paper, we review the reconstruction algorithm for NLoS imaging tasks. Firstly, considering the crossover and non-independent phenomena existing in the NLoS imaging classification, we use the different features of physical imaging models and algorithm models to reclassify them. Secondly, according to the proposed classification criteria, we respectively review the traditional and deep learning-based NLoS imaging reconstruction algorithms, summarize the state-of-the-art algorithms, and derive the implement principle. We also compare the results of deep learning-based and traditional NLoS imaging reconstruction algorithms for reconstruction tasks. Finally, the current challenges and the future development of NLoS imaging are summarized. Different types of NLoS imaging reconstruction algorithms are comprehensively analyzed in this review, which provides important support for the further development of NLoS imaging reconstruction algorithms.
Laser-Induced Thermo-Elastic Spectroscopy (LITES) is a new developed gas detection technology based on the thermoelastic effect of Quartz Tuning Forks (QTF). The QTF has the advantages of low cost, small volume, high sensitivity and wide spectral response range, and the LITES is becoming a vital method for trace gas detection. In this paper, the basic principle of gas concentration measuring based on LITES is firstly analyzed. Secondly, from the perspective of various technical methods, this paper introduces the methods for improving the sensitivity of QTF detectors, and reviews the research progress of LITES system in recent years. The performance of these systems is evaluated by the signal amplitude, Signal-to-Noise Ratio (SNR), minimum detection limit, and Normalized Noise Equivalent Absorption (NNEA) coefficient. Finally, the practical application of LITES in the field of gas detection technology is briefly reviewed, and the methods for further improving its sensitivity are summarized and prospected.
Atmospheric temperature, humidity and pressure are deemed important atmospheric parameters. Quickly and accurately understanding the temperature, humidity and pressure information of the atmosphere and their changing trends is of great significance to research on meteorology, climatology, and artificial weather research. Raman lidar can obtain various atmospheric environment-related parameters by separating Raman scattering signal inversion, which can achieve high accuracy detection of atmospheric parameter profile information. Raman lidar has unique advantages and potential in atmospheric temperature, humidity and pressure detection. With an introduction to the principle and inverse analysis algorithm of Raman lidar for atmospheric temperature, humidity and pressure detection, this paper also highlights the advantages and disadvantages along with related advances of spectral devices such as filters, etalons and gratings commonly used in Raman lidar. The detection techniques involved in Raman lidar are also included. Finally, typical applications of meteorological parameter measurements by Raman lidar are shown.
With the continuous development of optical imaging technology and the growing demand for remote sensing applications, cross-scale high-resolution optical technology has been widely used in the field of remote sensing. In order to obtain more detailed information on the target, domestic and foreign researchers have carried out relevant research in different technical directions. In this paper, through the technical classification of remote sensing imaging, we introduce a representative aerospace optical remote sensing high-resolution imaging system. It focuses on monomer structure, block expandable imaging, optical interference synthesis aperture imaging, diffraction main mirror imaging, optical synthetic aperture and other technologies. It provides a new idea for the development of high-resolution optical remote sensing loads on the ground.
With the rapid development of laser technology, the application of laser in the medical field has gained growing attention. Due to its advantages of non-contact, high precision, low damage, portability and operational flexibility, laser treatment significantly enriches the clinical treatment toolkit. Moreover, it has substituted traditional methods for certain diseases and improved the overall medical treatment capability. Currently, laser treatment has gained increasing market share and has a great potential for even more widespread applications. Here, we introduce the laser treatment technique and the requirements of medical laser systems, expound the current status of the applications of laser treatment in clinical departments in a comprehensive manner, and give suggestions regarding to the problems in the laser treatment field in China.
Periodic optical systems, such as photonic crystals and optical metamaterials, can localize high-density electromagnetic field energy at subwavelength scales and obtain extremely small mode volumes, so they have great application potential in the field of light manipulation. In recent years, a strong interaction between light and matter in periodic optical systems has been discovered, which is called Bound States in Continuum (BIC). Optics BICs are special electromagnetic eigenstates whose frequencies lie in the radiation continuum but are completely localized, and have shown interesting physics and rich application scenarios. This paper systematically reviews the classification and theory of BICs in periodic optical systems, and summarizes their basic physical properties and the latest application development. BICs in periodic optical systems are injecting new impetus into the fields of integrated optics, information optics, bio-optics, topological optics, and nonlinear optics.
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Supervisor: Chinese Academy of Sciences
Sponsors: the Changchun Institute of Optics, Fine Mechanics, and Physics (CIOMP), CAS
Editor-in-Chief: Wang Jiaqi, Academician
ISSN 2097-1842
CN 22-1431/O4
CODEN ZGHUC8
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