Laser cleaning technology, as an efficient and environmentally friendly surface treatment method, plays significant application potential in the field of chip packaging molds cleaning. This research systematically investigated the effects of laser parameters (pulse duration, repetition rate, average power) on the cleaning effect of Epoxy Molding Compound (EMC) contaminates from mold surface coated with chromium on P20 alloy and ASP23 alloy substrates. The experiment employed a 1064 nm Nd-doped pulsed laser, reshaping the Gaussian beam into a flat-top beam, and combining with a "bow" shape scanning path of the galvanometer mirror. The process parameters were optimized using a single-variable method. The experimental results indicate that when the laser energy density is in 0.55−0.77 J/cm², the pulse duration and repetition rate need to be adjusted in coordination to balance the thermal input, enabling complete removal of contaminants without any damage to the substrate. Parameter sensitivity analysis reveals that the optimal duty cycle range is from 0.8% to 1.0%. Furthermore, when the power exceeds the threshold (150 ns@50% average power or 200 ns@50% average power), it may cause damage to the substrate, which indicates that laser parameter matching is crucial for the cleaning effect and material protection. This research provides a high-precision, non-contact and environmentally friendly cleaning solution for chip packaging molds, and verifies the feasibility of laser cleaning technology in the field of integrated circuits.

In recent years, ultrafast fiber laser coherent beam combination (CBC) has developed rapidly, becoming an important technical means for enhancing the average power of ultrafast and ultra-intense lasers. However, due to factors such as spectral gain narrowing in single-channel fiber amplifiers and high-order dispersion mismatch, the output pulse width of high-power ultrafast fiber laser CBC systems is significantly wider compared to that of bulk solid-state laser systems, severely limiting its peak power enhancement. From the perspective of pulse compression in ultrafast fiber laser coherent combining, this review systematically analyzes the following three aspects: pulse shaping technique based on fiber chirped pulse amplification, combining technique based on fiber nonlinear spectral broadening, and coherent spectral combining technique based on partial spectral interference. Additionally, a brief conclusion and outlook on the future development of ultra-short pulse fiber laser CBC is given at the end.

Standard bacterial suspensions play a crucial role in microbiological diagnosis. Traditional preparation methods, which rely heavily on manual operations, face challenges such as poor reproducibility, low efficiency, and biosafety concerns. In this study, we propose a high-precision automated colony extraction and separation system that combines large-field imaging and artificial intelligence (AI) to facilitate intelligent screening and localization of colonies. Firstly, a large-field imaging system was developed to capture high-resolution images of 90 mm Petri dishes, achieving a physical resolution of 13.2 μm and an imaging speed of 13 frames per second. Subsequently, AI technology was employed for the automatic recognition and localization of colonies, enabling the selection of target colonies with diameters ranging from 1.9 to 2.3 mm. Next, a three-axis motion control platform was designed, accompanied by a path planning algorithm for the efficient extraction of colonies. An electronic pipette was employed for accurate colony collection. Additionally, a bacterial suspension concentration measurement module was developed, incorporating a 650 nm laser diode as the light source, achieving a measurement accuracy of 0.01 McFarland concentration (MCF). Finally, the system’s performance was validated through the preparation of an Esckerichia coli (E. coli) suspension. After 17 hours of cultivation, E. coli was extracted four times, achieving the target concentration set by the system. This work is expected to enable rapid and accurate microbial sample preparation, significantly reducing detection cycles and alleviating the workload of healthcare personnel.

Filters, as a key component in the photoelectric detection system, can simplify the optical system and improve detection efficiency. Based on the usage requirements, a visible/near-infrared filter film with up to 5 wavebands needs to be designed and prepared, while simultaneously satisfying high reflection in 2 wavebands and high transmittance in 3 wavebands. Therefore, we have conducted a systematic study on the film design, thin film preparation process, and control accuracy of film layer thickness. In this work, the short-wave pass film system is superimposed with the long-wave pass film system, and the number of cycles and matching coefficient of the film system are tuned to meet the requirements of cut-off band. Additionally, Smith method was used to match bandpass film system to optimize the transmission band and complete the visible/near infrared multiband laser filter film design. In the preparation process, combined with the sensitivity of the film layer, inverse analysis is used to invert the film layer monitored by each optical monitoring chip. The optical control scheme with weak optical signal in the monitoring process is simulated and corrected, and the monitoring wavelength with stronger optical signal is matched, resulting in an improvement of the control accuracy for the film thickness and the transmittance in the specified wavelength range. Ultimately, the actual physical thickness is 9.66 μm, and the error with the theoretical design thickness is less than 0.4%, and the transmittance of the specified 3 wavebands exceeds 99%. The average transmittance of the cut-off bands at the 455−500 nm and 910−1000 nm is 0.45% and 0.16%, respectively.

The Savitzky-Golay (SG) filter, which employs polynomial least-squares approximations to smooth data and estimate derivatives, is widely used for processing noisy data. However, noise suppression by the SG filter is recognized to be limited at data boundaries and high frequencies, which can significantly reduce the signal-to-noise ratio (SNR). To solve this problem, a novel method synergistically integrating Principal Component Analysis (PCA) with SG filtering is proposed in this paper. This approach avoids the issue of excessive smoothing associated with larger window sizes. The proposed PCA-SG filtering algorithm was applied to a CO gas sensing system based on Cavity Ring-Down Spectroscopy (CRDS). The performance of the PCA-SG filtering algorithm is demonstrated through comparison with Moving Average Filtering (MAF), Wavelet Transformation (WT), Kalman Filtering (KF), and the SG filter. The results demonstrate that the proposed algorithm exhibits superior noise reduction capabilities compared to the other algorithms evaluated. The SNR of the ring-down signal was improved from 11.8612 dB to 29.0913 dB, and the standard deviation of the extracted ring-down time constant was reduced from 0.037 µs to 0.018 µs. These results confirm that the proposed PCA-SG filtering algorithm effectively improves the smoothness of the ring-down curve data, demonstrating its feasibility.

Due to the inability of manufacturing a single monolithic mirror at the 10-meter scales, segmented mirrors have become indispensable tools in modern astronomical research. However, to match the imaging performance of the monolithic counterpart, the sub-mirrors must maintain precise co-phasing. Piston error critically degrades segmented mirror imaging quality, necessitating efficient and precise detection. To address the limitations that the conventional circular-aperture diffraction with two-wavelength algorithm is susceptible to decentration errors, and the traditional convolutional neural networks (CNNs) struggle to capture global features under large-range piston errors due to their restricted local receptive fields, this paper proposes a method that integrates extended Young’s interference principles with a Vision Transformer (ViT) to detect piston error. By suppressing decentration error interference through two symmetrically arranged apertures and extending the measurement range to ± 7.95 μm via a two-wavelength (589 nm/600 nm) algorithm. This approach exploits ViT’s self-attention mechanism to model global characteristics of interference fringes. Unlike CNNs constrained by local convolutional kernels, the ViT significantly improves sensitivity to interferogram periodicity. The simulation results demonstrate that the proposed method achieves a measurement accuracy of 5 nm (0.0083λ₀) across the range of ± 7.95 μm, while maintaining an accuracy exceeding 95% in the presence of Gaussian noise (SNR ≥ 15 dB), Poisson noise (λ ≥ 9 photons/pixel), and sub-mirror gap error (E_gap ≤ 0.2) interference. Moreover, the detection speed shows significant improvement compared to the cross-correlation algorithm. This study establishes an accurate, robust framework for segmented mirror error detection, advancing high-precision astronomical observation.

Limited by the diffraction limit, the spatial resolution of traditional microwave antennas is difficult to break through the constraint of the wavelength scale, which hinders their application in high-resolution microwave sensing and detection. In this paper, we design an all-dielectric integrated meta-antenna beyond the physical diffraction limit. Firstly, the meta-antenna is functionalized using asymmetric scattering metagrating array based on the generalized Snell's law. High-efficiency focusing beam in the sub-wavelength scale is obtained by manipulating the electromagnetic wavefront. Then, by optimizing the geometric structure of the metagrating to achieve high manipulation efficiency. Finally, the electric field intensity distribution of the generated focal spot is analyzed. The simulation results demonstrate that the manipulation and diffraction efficiencies of the metalens reach 98.50% and 72.56%. The metalens shows a focal spot with the diameter of 0.73λ and depth of focus (DOF) of 15.11λ. The designed meta-antennas possess the characteristics of long focal depth and high efficiency. Its sub-wavelength focusing property significantly enhances the spatial resolution, which provides a new method for high-precision sensing and detection in the fields such as microwave imaging and non-destructive testing, possessing potential application value.

Image Photoplethysmography (IPPG) signals are easily disturbed by noise during acquisition. To address the issue, this study proposes a denoising diffusion probability model for IPPG (DDPM-IPPG). This model eliminates baseline drift and noise through diffusion and reverse diffusion stages, and improves the signal-to-noise ratio and heart rate accuracy. First, Gaussian noise is gradually added to the photoplethysmography (PPG) signal during the diffusion phase to create a noise sequence. A noise predictor based on a nonlinear fusion module and a bridging module is trained. Subsequently, in the reverse diffusion phase, the well-trained noise predictor is employed to perform step-by-step denoising on the initially extracted IPPG signal. Through this denoising, a signal with high signal-to-noise ratio is recovered. The model proposed in this paper is validated and compared with current mainstream algorithms on the PURE, UBFC-IPPG, UBFC-Phys, and MMPD datasets. The experimental results show that DDPM-IPPG improves the signal-to-noise ratio by 1.06 dB on the PURE dataset comparing with the existing highest-precision extraction method. The mean absolute error of heart rate decreases by 0.24 bpm. The root mean square error of heart rate decreases by 0.41 bpm. On the UBFC-IPPG dataset, the signal-to-noise ratio improved is by 1.50 dB. The proposed DDPM-IPPG model has achieved the current advanced level in eliminating baseline drift and noise from IPPG signals, enabling a more precise approximation of the true signals and providing a more reliable data foundation for physiological health assessment and telemedicine monitoring.

Optical surface particulate contamination detection is critical to maintaining the imaging performance of space telescopes. Conventional approaches typically employ dark-field scattering microscopy to capture particle images, where particle size is estimated from the circumcircle of the particle’s contour. However, this method requires precise focusing during image acquisition and is prone to large errors when dealing with irregularly shaped particles. To address these limitations, this paper introduces a novel sizing method based on defocus-induced blur circles. By exploiting the relationship between particle size and its scattered light energy, the defocused dark-field scattering image of a particle is transformed into a blur circle, whose properties can be analyzed to determine the actual particle size. Unlike conventional contour-based measurements, the blur-circle approach is inherently less sensitive to particle shape irregularities and system defocus. Experimental validation demonstrates that the proposed method achieves high sizing accuracy across varying defocus distances. Compared with traditional dark-field scattering microscopy, the average measurement error for irregularly shaped particles is significantly reduced from 58% to 10.3%. These results confirm both the feasibility and effectiveness of the blur circle method in improving measurement precision for irregular particulate contaminants.

To accurately quantify the attenuation of visible light in urban optoelectronic systems during dust weather, we establish a predictive model that integrates corrections for non-spherical particles, using the Hohhot region as a case study. Utilizing Mie scattering theory alongside scanning electron microscopy and energy-dispersive X-ray spectroscopy data from local dust samples, the extinction characteristics of dust particles in typical red green and blue wavebands were calculated. Scattering parameters for non-spherical particles were corrected via the T-matrix method. Photon multiple scattering was then simulated with the Monte Carlo method to systematically compare attenuation rates between single and multiple scattering models. The results demonstrate that the single-scattering model systematically overestimates the attenuation rate, with a maximum error of 18.3% in the blue band. After multiple scattering correction, the attenuation rate decreased by an average of 12.4%. In this case, when the visibility is 400 meters, the attenuation rate for blue light was approximately 95 dB/km, significantly exceeding the value of 70 dB/km for red light. The hybrid model developed significantly enhances the prediction accuracy for visible light attenuation in dusty environments, elucidating the critical roles of multiple scattering effects. This work provides a reliable theoretical and data-driven foundation for optimizing urban optoelectronic systems in dust-prone conditions.

In the process of 3D scene reconstruction, the spatial resolution of the light field camera (LFC) affects the recoverable spatial details as well as the depth resolution, thereby influencing the accuracy of the 3D reconstruction. Therefore, calculating and analyzing the spatial resolution of the LFC is crucial for identifying the high and low resolution regions. In this paper, a calculation method for the spatial resolution of an LFC is explored based on the forward ray-tracing technique, which has the advantage of high accuracy. The spatial resolutions of LFC 1.0 and LFC 2.0 under different microlens array configurations are quantitatively calculated and compared. In addition, the effects of the inverse magnification (M_l) of the main lens on the depth resolution of the LFC are investigated. The results show that the LFC exhibits higher depth resolution in regions away from the intersection of the object plane and the optical axis. The depth resolution of LFC 2.0 near the region of (0,0,0) is better than that of LFC 1.0. For a microlens array arranged in a square pattern, the lateral resolution of LFC 2.0 shows a slight improvement over that of LFC 1.0. The depth resolution of the LFC 1.0 gradually decreases as M_l increases.

This study investigates the impact of doping the non-fullerene small molecule IEICO-4F into the acceptor component of a planar heterojunction organic photodetector based on the P3HT : PC₇₁BM system on the device's optoelectronic properties. The active layer films with different doping ratios were fabricated using a solution process. Characterization techniques including current-voltage measurements, external quantum efficiency, ultraviolet-visible-near-infrared absorption spectroscopy, and photoluminescence spectroscopy were employed, combined with atomic force microscopy to analyze morphological evolution. Experimental results demonstrate that the introduction of IEICO-4F significantly broadens the absorption spectrum of the active layer into the near-infrared region (700−900 nm) and enhances photon capture efficiency through complementary absorption spectrum. At an optimized doping ratio of 30%, the device's photocurrent density increases from 19.17 mA/cm² to 27.25 mA/cm², and the specific detectivity improves from 0.78×10¹² Jones to 1.45×10¹² Jones. Morphological analysis confirmes that IEICO-4F optimizes the phase distribution of PC₇₁BM, forming a finer interpenetrating network structure that facilitates charge transfer and reduces series resistance. The study also reveales that excessive doping disrupts the phase separation balance, adversely affecting carrier separation and transport, leading to an imbalance in electron-hole transport. This work highlights the multifaceted regulatory effect of non-fullerene acceptor doping on traditional polymer: fullerene systems, effectively enhancing device performance through the synergistic mechanisms of spectral broadening and morphological optimization, thereby providing new insights for the design of organic photodetector material systems.

To achieve high-power and high-beam-quality laser output from a laser-diode (LD) side-pumped solid-state laser, we investigate an unstable resonator incorporating a Gaussian output mirror. The boundary finite element method was utilized to analyze the effects of the resonant cavity length, Gaussian mirror membrane spot radius, and curvature radius on high-order mode suppression. The functional theory of mode loss difference was applied to determine the mode-matching range and the optimal parameters for the spot radius. Furthermore, an output power model was established to derive the theoretical optimal central transmittance for compensating loss. Based on the theoretical and simulation results, the resonator parameters were optimized, and the output beam’s mode distribution and quality were experimentally characterized using different Gaussian mirrors. Under the operational conditions of a 400 mm resonator length, 7.3 A pump current, and 100 Hz repetition frequency, the implementation of a Gaussian mirror with a 3 mm spot radius, 1.5 m curvature radius, and 17% central transmittance produced a high-quality 1064 nm laser output with beam quality factors of M_x²=2.09 and M_y²=2.20.

An alternative elliptical and circle air-hole-assisted Al_0.24Ga_0.76As photonic crystal fiber (PCF) was proposed for generating broadband high-coherence mid-infrared supercontinuum, and the dispersion, effective mode area and nonlinear coefficient were investigated by using finite element method (FEM), the evolution of optical pulses propagating along the fiber was simulated, and the supercontinuum and the coherence were analyzed and evaluated under different pumping conditions. The results show that a supercontinuum spectrum with a spectral width of 4.852 μm can be obtained in the proposed fiber with d₁/Λ of 0.125, d₂/Λ of 0.583 and the zero-dispersion wavelength of 3.228 μm by pumping with a Gaussian pulse with a peak power of 800 W and a full width at half maximum (FWHM) of 20 fs at wavelength of 3.3 μm. When the fiber is pumped by the pulse with the peak power of 2000 W, the FWHM of 80 fs at the wavelength of 4.0 μm in the in the anomalous dispersion region, the modulation instability is obviously suppressed, and the high-coherence supercontinuum spectrum spanning from 1.1 μm to 8.99 μm is observed. A part of the pulse energy is transferred to the anomalous dispersion region when pumped at the wavelength of 2.8 μm in the normal dispersion region and a broadband high-coherence supercontinuum spectrum extending from 0.8 μm to 9.8 μm is generated in the 10 mm proposed fiber. This paper introduces elliptical air holes in the Al_0.24Ga_0.76As photonic crystal fiber, which enhances flexibility for tailoring the performance of supercontinuum, ultimately achieving the broadest supercontinuum spectrum with the shortest fiber length to date.

The dual-wavelength image plane digital holography is employed to achieve the long-distance topography measurements, which is expected for the Examination and Analysis System Technology (EAST) in divertor surface monitoring. The same-path design for the illumination and imaging beams is suitable for the upper diagnosis channel of the tokamak device. By selecting two wavelengths with a gap of 1.02 nm, the measurement range of system is extended to 276.87 µm, allowing for 138.44 µm gradient measurements. Experimental results demonstrate that the measurement error of the system for a step with a nominal high of 80 μm is 7.00%, with a minimum detectable height variation of 10 μm. Furthermore, the long-distance measurement capability of the system was confirmed, and off-line measurements were conducted on a dismantled divertor from a tokamak device, proving that the system can be applied to the topography measurements of the divertor.

In recent years, the demand for synchronous acquisition of three-dimensional (3D) shape and color texture has surged in fields such as cultural heritage preservation and healthcare. Addressing this need, this paper proposes a novel method for simultaneous 3D shape and color texture capture. First, a linear model correlating camera exposure time with grayscale values is established. Through exposure time calibration, the projected red, green and blue (RGB) light and white-light grayscale values captured by a monochrome camera are aligned. Then, three sets of color fringes are projected onto the object to identify optimal pixels for 3D reconstruction. And, three pure-color patterns are projected to synthesize the color texture. Experimental results show that this method effectively achieves synchronous 3D shape and color texture acquisition, offering high speed and precision, and avoids color crosstalk interference common in 3D reconstruction of colored objects using a monochrome camera.

In order to find out performance of the C-point dipole nested in partially coherent stochastic vortex beam in oceanic turbulence, the Gaussian-Schell model vortex (GSMV) beam carrying a C-point dipole is constructed, which is used to research the evolution property of the C-point dipole in oceanic turbulence. According to the definition of the polarization singularities in partially coherent vector beams, the GSMV beam was constructed to realize a partially coherent beam carrying a pair of C-point dipoles with opposite topological charges. According to the extended Huygens–Fresnel principle, the formula of the cross-spectral density (CSD) for the GSMV beam propagating through oceanic turbulence is deduced by using of the integral formula. In accordance with the formula of the CSD derived above, the effects of propagation distance z, the off-axis parameter s and coherent length δ on the evolution behavior of the C-point dipole is illustrated and analyzed. The position of a C point can be determined by the contour lines of phase of Stokes field S₁₂ = S₁ + iS₂. The degree of polarization of a C point can be calculated by spectral Stokes parameters, while its topological charge can be judged by the sign principle which was proposed by Freund. It is shown that, the position and the degree of polarization of the C points may be changed with propagation of the GSMV beam. Though the creation and annihilation of C points may occur with variation of the propagation distance, the total of the topological charges of C points of the beam hold consistent. Besides, as the off-axis parameters are chosen as opposite numbers, the numbers of C points from the optical fields are equal. When the partially coherent vortex beam carrying a C-point dipole propagates in oceanic turbulence, the evolution behavior of the C-point dipole is affected by the propagation distance of the host beam, the off-axis parameter, turbulence intensity as well as the spatial coherent length.

In wide-temperature-range applications, traditional optical systems often struggle to maintain stable imaging quality, primarily because conventional athermal design methods fail to fully account for the differences in the linear expansion coefficients and refractive index temperature coefficient of glass materials at high and low temperatures. To address this issue, this paper proposes an athermal design method for wide temperature ranges. By reconstructing the thermal aberration modeling process, the method accurately characterizes the nonlinear response of thermal aberrations to temperature variation, thereby selecting glass material combinations that minimize the overall thermal optical power within the wide temperature range. In combination with the thermal expansion properties of the housing material, it effectively suppresses system focal shift. To validate the effectiveness of the proposed method, an optical system with a focal length of 100 mm, an F-number of 2.2, and a field of view of 7° was designed. Simulation results show that within the temperature range of −30°C to 270°C, the system consistently maintains high imaging performance. The modulation transfer function (MTF) remains above 0.5 at 56 lp/mm across all fields and temperatures. The spot diameter is less than 9 μm, and more than 90% of the energy is enclosed within an 18 μm circle. The above results fully verify the effectiveness of the proposed method and provide strong support for athermal design of optical systems under wide temperature ranges. Meanwhile, the method demonstrates good engineering adaptability and shows broad application prospects in the design of imaging systems for complex environments.

Terahertz (THz) spectroscopy technology has demonstrated great application value in the field of organic and biological macromolecule detection. However, the traditional sample pressing method cannot be applied in the actual detection of trace analytes, and additional structures are required to enhance the interaction between the analytes and THz waves. To solve this problem, we propose a terahertz absorption spectrum enhancement structure based on stacked one-dimensional photonic crystals (1D-PCs) defect cavities. The structure employs metal parallel-plate waveguides to separate a series of one-dimensional photonic crystals (1D-PCs) with defect cavities of varying widths, and coats the sample film on a substrate that penetrates all defect cavities. The incident broadband terahertz wave can simultaneously excite multiple resonant peaks at different frequencies corresponding to the photonic crystal defect modes in different layers. The enhanced terahertz absorption spectrum of the analyte can be obtained by linking the envelope formed by these resonant absorption peaks. The simulation results show that a 0.1 μm α-lactose sample can accomplish an absorption enhancement factor of approximately 303 times in the frequency range of 0.49 to 0.57 THz. This method offers fast measurement speed and maintains a relatively low sample amount, providing an effective strategy for the enhancement detection of trace analytes by terahertz absorption spectrum.

Off-axis reflective optical systems are widely employed in Earth observation and mapping owing to their advantages of wide field of view (FOV), high image quality, and stable interior orientation elements. To address the degraded off-axis image quality and thermally induced pointing drift of initial designs from conventional aberration-cancellation methods, this study analytically derives the third-order aberration coefficients of a three-mirror system, assuming a stop at the secondary mirror and symmetric axial spacing between the primary and tertiary mirrors. To further enhance imaging performance, fourth-order aspheric terms are introduced on both the primary and tertiary mirrors, thereby increasing the degrees of freedom for optimization. A comprehensive image-quality evaluation function incorporating quasi-telecentric constraints is constructed, and a hybrid genetic algorithm-sequential quadratic programming (GA-SQP) approach is employed to obtain an optimized initial configuration. The resulting system achieves a focal length of 260 mm, an F-number of 10, and a 7° × 30° FOV, with a modulation transfer function (MTF) above 0.25 at 77 lp/mm, a maximum distortion of 2%, and a maximum chief-ray angle of 2.3°. Microcrystalline glass and titanium alloy are adopted as the mirror substrate and structural materials, respectively. Finite-element thermal analysis is performed under a 6.8 °C temperature gradient, and the optical axis rotation, evaluated using the TRIAD algorithm, is −1.3″ around the X-axis, −11.9″ around the Y-axis, and −0.004″ around the Z-axis. These results confirm the excellent thermal stability of the proposed design and underscore its potential for reducing in-orbit mapping errors under uncontrolled thermal environments.

Multi-band infrared detectors can simultaneously capture radiation information across multiple wavelengths, offering significant advantages over single-band infrared detectors in target recognition, classification, temperature measurement, and information extraction. Consequently, they have become a central focus of infrared detector technology research. As a key optical component of multi-band infrared detectors, the performance of the three-band large-aperture wide-angle infrared mirror directly determines detection accuracy. In the design phase, this study selected three materials: Ge, ZnS, and YbF₃, and fabricated a structurally robust infrared reflector coating system through spectral superposition combined with TFCalc software according to high-reflectivity coating design principles. During the preparation stage, ion-source-assisted deposition was employed, and the issue of film delamination was resolved by optimizing the deposition process. During spectral testing, problems related to spectral drift in the samples were addressed through film thickness error experiments and optimization of the YbF₃ process. Test results indicate that, at an incident angle of 45°, the infrared mirror achieves an average reflectance of 96.93% in the 3−5 µm spectral band, 96.54% in the 8−12 µm spectral band, and 94.64% in the 1.064 µm spectral band; the spectral non-uniformity within the 270 mm×270 mm aperture for the 3−5 µm and 8−12 µm spectral bands is 4.83%. In accordance with the national standard GJB 2485A-2019 (Environmental Test Standard), the prepared samples successfully passed adhesion and high and low temperature tests, meeting the application requirements for multi-band infrared detectors.

With the rapid development of space laser communication technology, the demand for high-speed inter-satellite networking has been growing significantly. However, existing research on inter-satellite laser communication payload is still primarily experimental, featuring complex optical system designs that require lengthy and costly processes for manufacturing, alignment, and testing-posing challenges for low-cost and rapid mass production. To address this issue, a transmissive optical antenna with single-band achromatic design is proposed in this paper, along with a rapid alignment method for measuring the magnification of the optical antenna based on a collimator. By narrowing the chromatic aberration correction range, the length of the optical antenna is reduced by 15.83%, the number of lenses is decreased from six to four, and the manufacturing cost of a single optical antenna is reduced. Simulation results indicate that the alignment tolerance range for magnification is 4.37 to 5.08. After actual alignment, the measured magnification is 4.82, with a beam divergence of 67.53 μrad on the transmission path and a coupling efficiency of 51.42% on the receiving path. The self-calibration spot size is within 12×12 pixels. A comparative experiment is also conducted, and the proposed method demonstrates a noticeably shorter alignment time than the interferometer method. The alignment and testing results demonstrate that the proposed method not only enables a lightweight and compact design of the optical antenna, but also significantly reduces the alignment time. Simultaneous focal alignment of signal transmission, acquisition-pointing-tracking, and self-calibration optical paths is also achieved.

The transmission characteristics of rotationally symmetric power-exponent-phase vortex beams (RSPEPVBs) in biological tissues are explored in this study. Based on the extended Huygens-Fresnel principle, a general expression describing the transmission of RSPEPVBs through biological tissues is established. Numerical simulations are performed to explore the influence of the propagation distance z, power exponent n, wavelength λ, and beam waist width w on light intensity, beam width, and beam divergence. The findings reveal that increasing the propagation distance and wavelength results in greater beam diffusion and an enlarged beam width. Conversely, a higher power exponent concentrates the light intensity toward the center and mitigates the broadening of the beam width. Additionally, a longer wavelength and smaller beam waist width lead to a larger beam divergence angle. The evolution of coherence vortices and intensity peak positions with increasing propagation distance is also analyzed, revealing a gradual outward displacement from the beam center, accompanied by angular deviations and positional shifts. Notably, when the topological charge l ≥ 4, the position of the peak point undergo an abrupt shift during the transmission process. As a high-order mode beam, the transmission of RSPEPVBs in biological tissues exhibits diversity and controllability, opening up new possibilities for micro-manipulation technologies in the biomedical field.

In response to the current demand for high-precision planar displacement measurements in advanced manufacturing equipment, this paper proposes an xz dual-axis grating interferometer. The system adopts a biaxial Littrow incident light path structure, established using a biaxial beam splitter mirror and right-angled prism mirror. The relationship between the parallelism of the outgoing beam, the beam spacing, and the position and angle of the incident light is analyzed. Experimental results verify the feasibility and measurement performance of the proposed interferometer. The grating interferometer achieves a displacement resolution of 5 nm along the x-axis and 7 nm along the z-axis. After correction using the Heydemann algorithm, the periodic nonlinear error is reduced to ±5 nm. Over a travel range of 10 mm, the measurement accuracies are ±30 nm along the x-axis and ±100 nm along the z-axis, respectively. Finally, the influence of the surface error introduced by the non-coincident incident structure on the measurement results is discussed.

This paper presents a high-precision temperature sensor based on a high-quality factor thin-film lithium niobate microring resonator integrated with a microwave photonic readout system. The microring resonator, with a narrow linewidth of 2.87 pm and a high Q-factor of 10⁵, functions simultaneously as the temperature-sensing element and the core signal processing component of a microwave photonic filter. Through the thermo-optic effect, temperature variations are converted into shifts in the optical resonance wavelength, which are innovatively mapped to linear changes in the passband center frequency of the microwave photonic filter. A vector network analyzer is employed to accurately detect the microwave frequency response, enabling temperature measurement via high-resolution frequency variations and establishing a quantitative model between temperature and frequency shift. In contrast to conventional methods that directly track optical wavelength shifts, the proposed microwave photonic readout technique linearly converts minute resonance wavelength shifts into changes in the microwave center frequency, thereby overcoming the resolution limitations inherent in conventional optical spectrum analyzers. Experimental results demonstrate a sensitivity of 27 MHz/°C and a resolution of 0.002 °C, with excellent linearity maintained under temperature variations as small as 0.01 °C. This work effectively resolves the trade-off between sensitivity and resolution in traditional optical temperature sensing, offering a novel solution for on-chip integrated high-precision temperature monitoring.

To achieve uniform heat flux distribution on the receiver surface, an optimization method for heliostat aiming strategy in solar power tower plants is proposed. First, the heliostat field is divided into zones based on the calculated instantaneous optical efficiency of heliostats throughout the entire field, with different aiming factors designed for heliostats in different zones. Then, the spot size of each heliostat is calculated according to the aiming factor, and the relative spot size is determined by the ratio of spot size to receiver size, thereby planning the aiming point distribution. Finally, a genetic algorithm is employed to optimize the heliostat aiming point distribution, achieving uniform heat flux distribution on the receiver surface. Taking a hundred-megawatt-scale solar power tower plant as an example, the heliostat aiming strategy is optimized. Under typical spring equinox conditions, the peak heat flux density on the receiver surface is reduced from 1.94 MW/m² with equatorial aiming to 1.01 MW/m², improving uniformity by 53.29% while reducing the spillage factor by 0.86%. This ensures efficient and safe operation of the receiver while maintaining high interception efficiency.

To achieve precise quantification of slag adhesion and process optimization in laser cutting, this study investigates a convolutional neural network (CNN)-based prediction method that integrates both image and frequency-domain features. A dataset of 2160 cross-sectional images of 1 mm thick 304 stainless steel was constructed. From these images, key dross characteristics-area, height, and perimeter were accurately extracted using a combination of image processing techniques including Gaussian blur, adaptive thresholding, and morphological closing operations. To evaluate the predictive potential of different input representations, both RGB images and binarized images transformed via wavelet packet decomposition (WPD) were used as model inputs. The regression performance of three CNN architectures-VGG16, ResNet50, and DenseNet121 was systematically compared. Experimental results demonstrate that VGG16 achieved the highest prediction accuracy for dross area and height using RGB images, with mean absolute errors (MAE) of 0.019 mm² and 0.044 mm, respectively. For predicting the perimeter, which better reflects dynamic process behavior, the WPD frequency-domain input path yielded a significantly improved MAE of 0.094 mm and a normalized MAE (nMAE) of 5.25%. The regression fit between predicted and actual values showed a slope of 0.83 and a coefficient of determination (R²) of 0.86, indicating a strong linear correlation. This study confirms the effectiveness of VGG16 in predicting dross-related features and demonstrates the capability of WPD-derived frequency-domain features in capturing transient process information during laser cutting. The proposed methodology offers a reliable quantitative tool for intelligent process evaluation and closed-loop optimization.

Extending the operational wavelength range of integrated optical devices to cover the entire visible spectrum holds significant importance, as it can enhance the detection accuracy and applicability of miniaturized spectrometers, broaden the bandwidth of visible light communication, and enable biosensors to simultaneously detect multiple biomolecules in complex samples. As the fundamental building block of integrated optical devices, waveguides have not yet been thoroughly investigated for full visible spectrum operation. This work presents a waveguide design supporting the full visible spectrum (435−760 nm). Numerical simulations were employed to analyze the transmission characteristics of various waveguide structures, revealing that single-mode propagation cannot be achieved across the entire visible spectrum. Under multimode propagation conditions, key parameters such as propagation loss and mode distribution were systematically examined to determine the optimal waveguide dimensions, bending radii, and waveguide spacings for low-loss transmission: For slab waveguides, a thickness ≥1 μm ensures polarization insensitivity. For strip waveguides with a thickness of 1 μm, a width ≥2 μm significantly reduces scattering loss induced by sidewall roughness. For strip waveguides with a width of 1 μm and thickness of 2 μm, radiation loss becomes negligible when the bending radius ≥10 μm and waveguide spacing ≥0.4 μm, while maintaining effective isolation from adjacent waveguides. Additionally, the impact of fabrication tolerances on waveguide performance was evaluated. In contrast to previous studies primarily focusing on narrow spectral bands within the visible range, the proposed design enables full visible spectrum transmission in a single waveguide, thereby facilitating bandwidth expansion and performance enhancement for on-chip full visible spectrum devices.

Optical image processing has the advantages of fast and parallel operation. One single-layered metasurface is designed to implement the optical imaging and edge detection of image. The dual-functional image processing is conducted without the aid of 4f system and it is switched only by the handedness of incident circularly polarized light. The designed metasurface consists of silicon nanopillars and the optimized nanopillars are equivalent to half-wave plates with the transmittance of 87%. The simulation and experimental results verify the performance of metasurface. The integrated optical metasurface enables the extremely simple image processing system and it paves the way for the applications of metasurfaces in parallel image processing and optical integrating.

High-precision detection of topological charge is significant for the practical applications of vortex beams. In view of the existing evaluation with low resolution of topological charge and more complexity to judge simultaneously integer and fraction, this paper theoretically proposes and numerically verifies the double judgment method for topological charge based on the designed metasurface. The inner and outer diffraction patterns of metasurface can judge the value and sign of topological charge. The detection precision of the proposed method reaches 0.05. The theoretic and simulated results give the solid verification for the effectiveness of the proposed method. This method has outstanding advantages including planar structure design without additional elements, direct judgment without data processing and high precision over the existing methods. We think this work is beneficial to the detection of topological charge and the applications of optical vortices.

We propose a novel fast numerical calculation method for the Rayleigh–Sommerfeld diffraction integral, which is developed based on the existing scaled convolution method. This approach enables fast calculations for general cases of off-axis scenarios where the sampling intervals and numbers of the input and observation planes are unequal. Additionally, it allows for arbitrary adjustment of the sampling interval of the impulse response function, facilitating a manual trade-off between computational load and accuracy. The errors associated with this method, which is equivalent to interpolation, primarily arise from the discontinuities of the sampling matrix of the impulse response function on its boundaries of periodic extension. To address this issue, we propose the concept of the padding function and its construction method, and we evaluate its effectiveness in enhancing computational accuracy. The feasibility of the proposed method is verified by numerical simulation and compared with the DI-method in a simplified scenario. It shows that the proposed method has good computational accuracy for the general case where the sampling interval of the input and observation plane is not equal under non-near-field diffraction, and when the diffraction distance is large, although the computational accuracy of the proposed method cannot exceed that of the DI-method, the computational amount can be significantly reduced with almost no effect on the computational accuracy. This method provides a general numerical calculation scheme of diffraction in the non-near field case for areas such as computational holography.

We designed and investigated a passive synchronized mode-locked fiber laser. The device utilizes a dual-cavity structure driven by the Nonlinear Polarization Rotation (NPR) mechanism. Stable mode-locking is attained by synergistically controlling gain, polarization state, and optical path length in two symmetric sub-cavities. Experiments proved the sub-cavity repetition frequency's tunability via the time delay line (TDL), thereby enabling synchronized mode-locking. The system stably generates multi-wavelength pulses at a single repetition frequency, evidenced by multiple spectral peaks and equidistant pulse sequences. These findings facilitate the development of high-performance multi-wavelength ultrashort pulse sources, crucial for optical communications, spectral analysis, and remote sensing.

Noise interference is a critical bottleneck that affects the stability of sensing systems and the accuracy of data, and existing suppression strategies are unable to simultaneously reduce both inherent system noise and external environmental noise. To address this problem, this paper proposes a composite denoising method based on ameliorated ellipse fitting algorithm (AEFA) and adaptive successive variational mode decomposition (ASVMD). System noise, which is closely correlated with the direct-current (DC) and alternating-current (AC) components in the interferometric signal, is effectively suppressed in AEFA through the elimination of these components. Environmental noise components, which primarily reside in the demodulated phase signal, can be adaptively extracted by the SVMD technique. In order to automatically obtain the optimal decomposition results, the permutation entropy (PE) criterion is introduced to optimize the decomposition parameters. Correlation coefficient (CC) is used to distinguish between the effective components and noise components in the decomposition results. Experimental results indicate that the combined AEFA and ASVMD algorithm effectively suppresses both system and environmental noise. When applied to 50 Hz vibration signal processing, the proposed scheme achieves noise reduction of 17.81 dB and a phase resolution of 35.14 μrad/√Hz. Given the excellent performance of the noise suppression, the proposed scheme holds great application potential in high-performance interferometric sensing systems.

The two-dimensional grating serves as a critical component in plane grating interferometers for achieving high-precision multidimensional displacement measurements. The calibration of grating groove density and orthogonality error of grating grooves not only improves the positioning accuracy of grating interferometers but also provides essential feedback for optimizing two-dimensional grating fabrication. This study proposes a method for simultaneous calibration of these parameters using orthogonal heterodyne laser interferometry. A two-dimensional grating interferometer is built with the grating to be measured, and a biaxial laser interferometer provides a displacement reference for it. The phase mapping relationship between grating interference and laser interference is established. The interference phase information obtained by any two displacements can simultaneously solve the above three parameters and obtain the grating installation error. The feasibility of the proposed method is verified by using a 1200 gr/mm two-dimensional grating. The standard deviation of the grating groove density in the X and Y directions is 0.012 gr/mm and 0.014 gr/mm, respectively. The standard deviation of the orthogonality error of grating grooves is 0.004°, and the standard deviation of the installation error is 0.002°. Compared with the atomic force microscope method, the consistency of the grating groove density in the X and Y directions is better than 0.03 gr/mm and 0.06 gr/mm, and the orthogonality error of grating grooves is better than 0.008°. The experimental results show that the proposed method can be simply and efficiently applied to the calibration of the grating line parameters of the two-dimensional grating.

Addressing the critical challenge of thermal radiation noise suppression in infrared systems for long-range dim target detection, this paper presents a composite detection system with an optimized cooling-based thermal radiation suppression scheme. A common-aperture optical configuration capable of simultaneous long-wave infrared and laser dual-band detection is achieved through a Ritchey-Chrétien (R-C) optical structure and a dichroic-secondary mirror with a hollow design. To mitigate thermal radiation noise, the thermal emission characteristics within the temperature range of 230 K to 320 K were analyzed using Planck’s law and non-sequential ray tracing. An improved detection range model incorporating noise terms was developed. The cooling strategy was optimized via dynamic programming, leading to an optimal solution where the main mirror and folding mirror baffles are cooled to 220 K. Experimental results demonstrate that the detection range at 300 K ambient temperature increases from 300 km to 430 km, and remains above 400 km across the entire 230−320 K range. The proposed dual-band composite detection scheme and zoned cooling methodology provide a valuable reference for the design of cold optical systems and long-range weak target detection.

This study investigates the reduction in polarization measurement accuracy caused by varying incident angles in a liquid crystal variable retarder (LCVR). The phase delay characteristics of the LCVR were examined, with particular emphasis on the influence of different two-dimensional incident angles on phase delay behavior. Building upon the calibration of phase delay under normal incidence, a phase delay calibration model was developed to account for variations in incident angle and driving voltage. A mathematical relationship was established between phase delay and the azimuth angle (α) and pitch angle (β). Experimental validation was conducted under three conditions: α = 20°, β = 0°; α = 0°, β = 20°; and an arbitrary angle where α = 5°, β = 15°. The results demonstrated that the maximum average deviation between theoretical predictions and experimental measurements did not exceed 0.059 rad. The proposed calibration method proved to be both accurate and practical. This approach offers robust support for LCVR parameter calibration and performance optimization in optical systems, particularly in polarization imaging applications.

To address the challenges of complex metallic film coating processes and low integration in single-parameter detection for existing photonic crystal fiber surface plasmon resonance (PCF-SPR) sensors, a dual-parameter sensor based on gold nanowire-integrated bias-core PCF-SPR is proposed. Unlike conventional in-hole coatings or metallic film structures, the gold nanowires are directly attached to the fiber cladding via chemical vapor deposition (CVD), eliminating uneven coating issues and significantly simplifying fabrication. By optimizing the asymmetric bias-core fiber structure and leveraging the strong localized field enhancement of gold nanowires, the sensor achieves high-sensitivity synchronous detection of temperature (25−60 °C) and refractive index (1.31−1.40) in dual-polarization modes. The simulation results demonstrate that the x-polarization mode can achieve 1.31−1.40 refractive index detection with maximum wavelength sensitivity and amplitude sensitivity of 14800 nm/RIU and −1724.25 RIU⁻¹, and maximum refractive index resolution of 6.75×10⁻⁶ RIU. The y-polarization mode achieves refractive index detection range to 1.34−1.40, and the maximum wavelength sensitivity and amplitude sensitivity are 28400 nm/RIU and -1298.93 RIU⁻¹, and the maximum refractive index resolution is 3.52×10⁻⁶ RIU. For temperature sensing, the sensor exhibits a wavelength sensitivity of 7.8 nm/°C and a high resolution of 1.38×10⁻⁶ °C over the range of 25−60 °C. This design synergizes gold nanowires and the bias-core architecture to simplify fabrication while enabling multi-parameter detection. The proposed sensor offers new insights for integrated applications in biochemical monitoring, environmental sensing, and related fields.

AlGaN-based deep-ultraviolet (DUV) laser diodes (LDs) face performance challenges due to electron leakage and poor hole injection, often worsened by polarization effects from conventional electron blocking layers (EBLs). To overcome these limitations, we propose an EBL-free DUV LD design incorporating a 1-nm undoped Al_0.8Ga_0.2N thin strip layer after the last quantum barrier. Using PICS3D simulations, we evaluate the optical and electrical characteristics. Results show a significant increase in effective electron barrier height (from 158.2 meV to 420.7 meV) and a reduction in hole barrier height (from 149.2 meV to 62.8 meV), which enhance carrier injection and reduce leakage. The optimized structure (LD3) achieves a 14% increase in output power, improved slope efficiency (1.85 W/A), and lower threshold current. This design also reduces the quantum confined Stark effect and forms dual hole accumulation regions, improving recombination efficiency. Our findings present a promising approach for high-performance, EBL-free DUV LDs suitable for high-power applications.

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.

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.