As a non-contact ultra-precision machining method, abrasive water jet polishing (AWJP) has significant application in optical elements processing due to its stable tool influence function (TIF), no subsurface damage and strong adaptability to workpiece shapes. In this study, the effects of jet pressure, nozzle diameter and impinging angle on the distribution of pressure, velocity and wall shear stress in the polishing flow field were systematically analyzed by computational fluid dynamics (CFD) simulation. Based on the Box-Behnken experimental design, a response surface regression model was constructed to investigate the influence mechanism of process parameters on material removal rate (MRR) and surface roughness (Ra) of fused silica. And experimental results showed that increasing jet pressure and nozzle diameter significantly improved MRR, consistent with shear stress distribution revealed by CFD simulations. However, increasing jet pressure and impinging angle caused higher Ra values, which was unfavorable for surface quality improvement. Genetic algorithm (GA) was used for multi-objective optimization to establish Pareto solutions, achieving concurrent optimization of polishing efficiency and surface quality. A parameter combination of 2 MPa jet pressure, 0.3 mm nozzle diameter, and 30° impinging angle achieved MRR of 169.05 μm³/s and Ra of 0.50 nm. Experimental verification showed prediction errors of 4.4% (MRR) and 3.8% (Ra), confirming model reliability. This parameter optimization system provides theoretical basis and technical support for ultra-precision polishing of complex curved optical components.

In structured light 3D measurement systems, defocusing of the camera is inevitable. Because of camera defocus, the object’s complex surface texture introduces substantial phase errors, degrading measurement accuracy. To address this issue, this paper analyzes and formulates an error model for phase distortions arising from complex textures, and elucidates how these phase errors quantitatively depend on the relative orientation between fringe patterns and surface texture. Thus, a correction method for complex texture errors based on bidirectional fringe projection point cloud fitting is proposed. Theoretically, the point clouds obtained in both directions should coincide. Thus, the method corrects the phase by minimizing the Euclidean distance between the corresponding points in the two point clouds, ultimately yielding the corrected point cloud. To remove global shifts from calibration parameter errors, a pre-correction process is applied through point cloud matching. In comparative experiments, our method achieves up to 33.6% reduction in the mean absolute error (MAE) and 39.1% reduction in the root mean square error (RMSE) versus conventional approaches. These results demonstrate its superior accuracy for reconstructing objects with complex texture.

This study develops a single-molecule immunoassay system for flow-phase samples to enable early tumor biomarker detection. The system includes an optical fluorescence imaging platform and an image processing algorithm. First, we developed a flow-phase single-molecule immunoassay method suitable for real-time detection of low-concentration, high-throughput samples. Second, we designed a fluorescence imaging platform compatible with microfluidic chips, incorporating optical filters and beam splitters to achieve high-resolution fluorescence imaging. Third, we optimized a feature-matching algorithm to effectively detect out-of-focus fluorescent particles. Experimental results demonstrate a detection limit of 0.001 pg/mL within a linear range of 0.001−1 pg/mL, with coefficient of variation below 10%. The system can process up to 10 samples per hour. These findings indicate that our system meets the requirements for stable, sensitive, and high-throughput single-molecule detection, showing promising potential for early cancer screening.

To solve the problem of existing metasurface displacement measurement techniques unable to measure multiple physical quantities simultaneously, this paper proposes a metasurface cascade structure that can measure radial angular displacement and longitudinal line displacement simultaneously. First, the working principle of displacement measurement is described according to the joint phase modulation of circular polarized light by a cascade metasurface. Second, the displacement information carried by the phase delay is analyzed using the Jones transport matrix, and the angular and linear displacements are mathematically characterized. Then, the design objective is used as a constraint to optimize unit structure parameters and create metasurface models. Finally, the finite-difference time-domain method is used to simulate the metasurface structures, validate the method's feasibility, and evaluate the device's measurement performance. The results show that the angular displacement sensitivity was 0.9716 with a theoretical resolution of 34.27 μrad, and the linear displacement sensitivity was 0.0041 with a theoretical resolution of 8.12 nm at the working wavelength of 633 nm. The measurement freedom of metasurface displacement measurement technology is improved by this method. It is hoped that it can be further expanded to six dimensions so that the measured target's entire attitude can be determined.

A Yb:CaGd_0.33Y_0.625AlO₄ (Yb:CGYA) laser crystal of high optical quality has been successfully synthesized via the Czochralski method. The introduction of Gd³⁺ ions preserves the original structure and efficiently generates inhomogeneous broadening of the Yb³⁺ ion emission spectra. The fluorescence emission peak wavelength of the Yb:CGYA crystal is 1053 nm, and the corresponding measured full width at half-maximum is 93 nm. A tunable laser output ranging from 1017 nm to 1073 nm is achieved by using a birefringent filter, which represents the broadest tuning range reported in a short cavity to date. The compact laser offers great advantages for its applications around 1 μm.

The improved cross-correlation algorithm for the strain demodulation of Vernier-effect-based optical fiber sensor (VE-OFS) is proposed in this article. The algorithm identifies the most similar spectrum to the measured one from the database of the collected spectra by employing the cross-correlation operation, subsequently deriving the predicted value via weighted calculation. As the algorithm uses the complete information in the measured raw spectrum, more accurate results and larger measurement range can be obtained. Additionally, the improved cross-correlation algorithm also has the potential to improve the measurement speed compared to current standards due to the possibility for the collection using low sampling rate. This work presents an important algorithm towards a simpler, faster way to improve the demodulation performance of VE-OFS.

As an efficient passive anti-icing method, the superhydrophobic surface can reduce icing process on metals in low temperatures. However, the usual organic low-surface-energy decorations are often prone to age especially in harsh environments, leading to a decrease or complete failure of the anti-icing performance. Here, we adopt a method of femtosecond laser microstructuring to achieve inorganic superhydrophobic aluminum alloys through simultaneously modifying the surface profile and compositions. The obtained bionic anthill tribe structure with the low thermal conductivity, exhibits the superior delayed freezing time (803.3 s) and the low ice adhesion (16 μN) in comparison to the fluorosilane modified and bare Al surfaces. Moreover, such an inherently superhydrophobic metal surface also shows the exceptional environmental durability in anti-icing performance, which confirms the effectiveness of our superhydrophobic surface without the need for organic coatings.

The polarization properties of optical systems enable to change the polarization state of incident light, thus imaging quality and detection accuracy would be affected. For optical instruments such as telescopes and lithography lenses, polarization properties are important factors that determine the performance of these systems. Therefore, suppressing the unfavorable impacts of polarization properties on optical systems is key to achieve optical systems with good performance. This paper summarizes the current research status on methods to suppress the impacts of polarization properties on optical systems. The existing approaches are divided into three groups: polarization calibration, polarization compensation, and low polarization optimization design. The basic principles of these three methods are introduced, and the methods are classified and discussed with application examples. Finally, the relationship among the three methods and their cooperative applications is analyzed, and the future development of methods to suppress the impacts of polarization properties on optical systems is discussed.

To enhance measurement stability and accuracy for ultra-close-range target docking, this study proposes a monocular camera-based relative position and attitude measurement system with cooperative targets, enabling high-precision position and attitude determination between CubeSats. Through co-designed vision cameras on the chaser satellite and LED targets on the target satellite, precise relative pose measurement is achieved within 0.4−50 meters. First, the collaborative camera-target operation across far/near fields ensures clear imaging throughout the range from 50 meters to 0.4 meters. Second, a multi-scale centroid extraction algorithm incorporating slope consistency constraints and spacing ratio screening reliably acquires features under complex lighting conditions. Finally, combined with the initial pose estimation of the target satellite relative to the chaser, nonlinear optimization iteratively refines pose results to minimize errors. Experimental results demonstrate progressive accuracy improvement with proximity. At 0.4 m distance, the position measurement accuracy is better than 1 millimeter, and the attitude measurement accuracy is better than 0.2 degrees, satisfying ultra-close docking requirements. This solution provides high-precision, high-stability technical support for on-orbit space target relative navigation with important engineering application value.

To effectively enhance detection sensitivity and practicality, this paper proposes a fiber-optic temperature sensor based on a cascaded Lyot-Sagnac sensing structure sensitized by the Vernier effect and a Fabry-Pérot interferometer (FPI). The Lyot-Sagnac structure is fabricated by 90° rotated splicing of polarization-maintaining fibers (PMFs) with different lengths, while the FPI is constructed using a hollow-core photonic crystal fiber (HCPCF) as the Fabry-Pérot cavity. Theoretical analysis demonstrates that the Lyot-Sagnac structure fabricated via the 90° rotated splicing method exhibits a well-defined spectral envelope, and its cascading with the FPI significantly improves temperature sensitivity through the Vernier effect. The experimental results show that the temperature sensitivity of the cascade sensor is 12.56 nm/°C and 92.77 nm/°C when the PMF of different lengths in the Lyot-Sagnac sensor structure is used as the sensing location. Compared to a standalone Lyot-Sagnac interferometer, the proposed sensor achieves a sensitivity enhancement factor of approximately 57 times. In addition, the measurement range of PMF₁ mode is 9.3 times that of PMF₂ mode for the same measurement bandwidth. Therefore, compared with the traditional vernier effect fiber optic temperature sensor, the dual-response mode temperature sensor proposed in this paper not only has good detection sensitivity, but also can effectively adapt to the application scenarios with different detection ranges and sensitivity requirements by using the same spectral detection equipment, providing a new idea for the development of performance adjustable fiber optic temperature sensors.

To address the limitations of conventional data processing approaches in Ritchey-Common method-based inspection of large-aperture planar mirrors, particularly their restricted applicability and environmental sensitivity, this study presents a novel hybrid analytical methodology integrating sensitivity matrix decomposition with rigorous ray tracing simulations. The proposed framework establishes a comprehensive solution for high-precision surface figure characterization through systematic error decoupling and numerical optimization. The investigation commences with the development of a Zemax-based Ritchey-Common optical model, from which a sensitivity matrix is rigorously derived through advanced ray tracing algorithms. This matrix enables precise separation of systematic errors inherent in the measurement process, demonstrating superior accuracy compared to conventional Zernike polynomial aberration correction methods while eliminating approximation-induced artifacts in data interpretation. Subsequent numerical verification of the sensitivity matrix algorithm confirms its theoretical validity and computational robustness. Experimental validation encompasses dual-scale implementation: Primary verification employs a 200-mm aperture test mirror, where cross-comparative analysis with direct interferometric measurements achieves sub-wavelength consistency (RMS < λ/40). Full-scale application in the manufacturing process of a 2.2-meter class planar mirror demonstrates exceptional surface figure control, attaining final surface accuracy better than λ/50 RMS. The methodology exhibits significant improvements in measurement repeatability and environmental stability. This research establishes a generalized computational framework that effectively addresses the scalability challenges in ultra-precision optical testing, providing both theoretical advancement and practical engineering solutions for next-generation large-aperture optical systems fabrication.

Metalenses are subject to off-axis aberrations and material dispersion, which fundamentally limit their ability to achieve both wide field-of-view (FOV) and broad operational bandwidth in imaging detection systems. In this paper, an achromatic monolayer metalens with an elongated FOV in a continuous waveband is constructed using an elaborately designed metasurface. Leveraging a quadratic phase profile for large-field-of-view (FOV) detection, the metasurface unit structure transmission phase is subsequently optimized via particle swarm optimization (PSO) to achieve continuous band dispersion tuning. This approach consequently enables expanded operational bandwidth under wide-FOV conditions. For a monolayer metalens with a numerical aperture of 0.351, an achromatic focusing field covering a ±20° FOV is obtained within the continuous waveband from 0.55 μm to 0.65 μm. The maximum focal length deviation along the optical axis is 3.2 μm (~0.08 f₀), the incident angle detection deviation ≤ 1.34°. The proposed method can realize an achromatic monolayer metalens with an elongated FOV within a continuous waveband, which will have potential applications in lightweight and integrated optical imaging systems.

The impact of atmospheric background radiation on imaging quality in Doppler Asymmetric Spatial Heterodyne (DASH) interferometers for wind field detection is investigated, and a stray light suppression structure is designed. Utilizing orbital parameters and observation geometry, the influence of atmospheric background radiation on the signal-to-noise ratio (SNR) at varying altitudes is analyzed. Subsequently, a baffle is designed considering system parameters and SNR variation patterns, with its suppression efficacy evaluated via point source transmittance (PST). Results demonstrate that atmospheric background radiation intensifies with decreasing altitude, leading to progressive SNR degradation. PST curves indicate stable in-field PST unaffected by the baffle, preserving target light detection capability. Out-of-field PST decreases with increasing off-axis angle, dropping below 10⁻⁸ near the critical stray light suppression angle of 1.07°. The proposed suppression design fulfills system requirements for atmospheric background radiation mitigation.

This paper proposes a high-speed Mueller matrix measurement method based on an overdriving technique exerted on a liquid crystal variable retarder. First, a liquid crystal-based simulation model of the Mueller matrix measurement system is established, which helps to confirm the feasibility of the system. Next, an overdriving scheme for the liquid crystal variable retarder is introduced to shorten the polarization-state switching time. Finally, the Mueller matrices of air, a polarizer, and a quarter-wave plate are measured experimentally. The results show that the generation frequency of six polarization states increases from 71 Hz to 417 Hz, and the Mueller matrix measurement frequency increases from 10 Hz to 60 Hz, representing approximately a sixfold improvement. Furthermore, the mean squared error (MSE) of the measurements is below 0.0004. The extinction ratio exceeds 750:1. And the ellipsometric error is below 1.06%. These results demonstrate that the overdriving method enables high-speed Mueller matrix measurements, thereby facilitating applications in real-time inspection fields such as dynamic polarization analysis, online quality inspection of optical components, and biomedical imaging.

The hybrid optical-electronic optical convolutional neural network (OCNN) combines the parallel linear computation capabilities of photonic devices with the nonlinear processing advantages of electronic components, demonstrating significant potential in classification tasks. However, the fabrication inaccuracies of photonic devices and the circuit noise in FPGA-based backpropagation notably degrade the network performance. In this work, the hybrid OCNN is constructed, where the linear computations are performed by optical computing layers based on Mach-Zehnder interferometers (MZIs), while the pooling operations and the training process are implemented on the FPGA. This study focuses on the feasibility of on-chip training on FPGA, analyzing the impact of noise on training performance and proposing the network optimization strategies to enhance the noise immunity of OCNN. Specifically, the noise immunity is improved by adjusting the pooling method and pooling size, and the Dropout regularization is introduced after the pooling layer to further enhance the model's recognition accuracy. Experimental results indicate that the proposed on-chip training scheme effectively mitigates errors caused by the fabrication inaccuracy in the photonic devices. However, the circuit noise remains the primary factor limiting the OCNN performance. Notably, under the high circuit noise conditions, e.g. when the standard deviation of MZI phase error caused by circuit noise reaches 0.003, the combination of maximum pooling and Dropout regularization significantly improves the recognition accuracy of OCNN, which achieves a maximum of 78%. This research provides valuable insights for implementing on-chip training in OCNNs and explores new approaches for deploying hybrid optical-electronic architectures in high-noise environments.

A metal-sensitive diaphragm fiber optic pressure sensor with temperature compensation is proposed to address pressure monitoring in high-temperature environments, such as engine fuel systems, oil and gas wells, and aviation hydraulic systems. The sensor combines a metal-sensitive diaphragm and a sapphire wafer to form a temperature-pressure dual Fabry-Perot (FP) interference cavity. A cross-correlation signal demodulation algorithm and a temperature decoupling method are utilized to reduce the influence of temperature crosstalk on pressure measurement. Experimental results show that the maximum nonlinear error of the accuracy of the sensor pressure measurement is 0.75% FS and 0.99% FS at room temperature and 300 °C, respectively, in a pressure range of 0−10 MPa and 0−1.5 MPa. The sensor’s pressure measurement accuracy is 1.7% full scale (FS) when using the temperature decoupling method. The sensor exhibits good static pressure characteristics, stability, and reliability, providing an effective solution for high-temperature pressure monitoring applications.

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 k-domain analysis, automated layout generation of grating regions within the optical waveguide, waveguide optimization, and ray-field tracing simulations, thereby establishing a cohesive methodology for device development. The module extends beyond single-waveguide simulations to system-level analyses of near-eye displays, including micro-displays, micro-projectors, and human eye models. By bridging the microscopic and macroscopic scales, it enables holistic performance evaluation of AR optical systems, highlighting their capabilities and technical advantages. This module provides a robust and efficient platform for domestic optical engineers to advance the design and simulation of optical waveguides, thereby accelerating the industrialization and technological advancement of AR optics in China.

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.

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.

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.

To achieve wide-area detection of space targets, this study designs an optical system design with a broad spectrum range (400 nm−1000 nm), a large field of view (61°), a small F-number (1.38), and low distortion. This optical system is capable of detecting space targets with a magnitude of 6, enabling wide-area detection. Initially, a mapping between the radiation model of space target detection and the optical system parameters is established. The optical design is then theoretically analyzed using a reverse telephoto layout as the starting point. The design is optimized to balance and correct severe chromatic aberration resulting from the large field of view and wide spectral range, while improving enclosed energy and considering the roundness of scattered spots. The detection capability is verified through space optical simulation experiments. Results show that the optical system meets the wide-area detection requirements for space targets with a magnitude of 6. Finally, the physical detection capability of the optical system is experimentally verified. The results indicate that the optical system is capable of wide-area detection of space targets with a magnitude of 6. The overall design of the optical system is reasonable and compact, meeting the requirements of wide-area detection of space targets.

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.

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 0.0706 rad to 0.0168 rad, and the maximum phase error decreased from 0.4129 rad to 0.0960 rad. In the face plaster model experiments, the corrected standard phase error decreased from 0.0472 rad to 0.0102 rad, and the maximum phase error decreased from 0.2990 rad to 0.2408 rad. In 3D reconstruction of complex morphology plaster models of human faces, the surface quality was significantly improved, and the water ripple effect, which affects the phase quality, was significantly reduced. Compared with existing large-step phase-shifting methods, the proposed method not only achieves high-quality phase acquisition accuracy, but also offers clear advantages in terms of required data volume and operational convenience, demonstrating broad application potential.

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.