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 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.

The polarization characteristics of optical systems enable to change the polarization state of incident light, thereby affecting the imaging quality and detection accuracy, and other aspects. For optical instruments such as telescopes and lithography lenses, polarization characteristics are important factors that determine the performance of these systems. Therefore, suppressing the adverse effects of polarization characteristics in optical systems holds significant importance for achieving high-performance modern optical systems. This paper summarizes the current research status of methods for suppressing the impacts of polarization characteristics in optical systems,categorizing the existing approaches into three types: polarization calibration, polarization compensation, and low polarization optimization design. The fundamental principles of these three methods are introduced, and the classification and discussion of each method with practical application examples are provided. Finally, the paper analyzes the connections among the three types of methods and their synergistic applications, as well as discusses and provides prospects for the future development of methods to suppress the impacts of polarization characteristics in optical systems.

In the field of image processing, the analysis of Synthetic Aperture Radar (SAR) images is crucial due to its broad range of applications. However, SAR images are often affected by coherent speckle noise, which significantly degrades image quality. Traditional denoising methods, typically based on filter-based techniques, often face challenges related to inefficiency and limited adaptability. To address these limitations, this study proposes a novel SAR image denoising algorithm based on an enhanced residual network architecture, with the objective of enhancing the utility of SAR imagery in complex electromagnetic environments. The proposed algorithm integrates residual network modules, which directly process the noisy input images to generate denoised outputs. This approach not only reduces computational complexity but also mitigates the difficulties associated with model training. By combining the Transformer module with the residual block, the algorithm enhances the network's ability to extract global features, offering superior feature extraction capabilities compared to CNN-based residual modules. Additionally, the algorithm employs the adaptive activation function Meta-ACON, which dynamically adjusts the activation patterns of neurons, thereby improving the network's feature extraction efficiency. The effectiveness of the proposed denoising method was empirically validated using real SAR images from the RSOD dataset. The proposed algorithm exhibited remarkable performance in terms of EPI, SSIM, and ENL, while achieving a substantial enhancement in PSNR when compared to traditional and deep learning-based algorithms. The PSNR performance was enhanced by over twofold. Moreover, the evaluation of the MSTAR SAR dataset substantiated the algorithm's robustness and applicability in SAR denoising tasks, with a PSNR of 25.2021 being attained. These findings underscore the efficacy of the proposed algorithm in mitigating speckle noise while preserving critical features in SAR imagery, thereby enhancing its quality and usability in practical scenarios.

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 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, confirm the long-distance measurement capability of the system, and off-line measurements were conducted on a dismantled divertor from a tokamak device. Which proves the system can be applied to the topography measurements of the divertor.

In order to minimize misalignment angle errors in laser-guided seekers, we have optimized the quality of energy signals through advanced optical design techniques. The initial design parameters were derived by integrating aberration theory with sophisticated optical design software. We then employed an iterative design process for the optical system, focusing on both the optimization of the optical structure and the balance of aberrations. To enhance angular measurement precision, we improved the symmetry of the light spot by carefully controlling the image-side telecentric condition. Furthermore, a comprehensive performance analysis of optical plastic materials demonstrated the viability of using these materials in the manufacture of the seeker’s optical structure. Our final optical system design boasts a focal length of 71.6mm and an F/# of 1, with the edge field chief ray telecentric maintained below 6mrad. In the operating temperature range, the stability of spot size is better than 0.4% and the maximum distortion of the full field of view is less than 0.5%. Notably, within a ±2° field of view, both the light spot linearity and energy response consistency meet the stringent requirements for precision guidance. The structural design methodology we employed, which focuses on minimizing primary aberrations, can be effectively applied to the optimization of catadioptric systems, thus serving as a valuable reference for the optical structure design of similar seekers.

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 splicing polarization-maintaining fibers (PMFs) of different lengths with a 90° rotation, while the FPI is constructed using a hollow-core photonic crystal fiber (HCPCF) as the Fabry-Pérot cavity. The results of theoretical analysis demonstrates that the Lyot-Sagnac structure fabricated via the 90° rotated splicing method exhibits a well-defined output spectral envelope. When cascaded with an FPI, it can significantly improve temperature detection sensitivity through the Vernier effect. The experimental results show that the temperature sensitivity of the cascaded sensor is 12.56 nm/°C and 92.77 nm/°C when utilizing PMFs of different lengths in the Lyot-Sagnac sensor structure as the sensing regions. Compared to the standalone Lyot-Sagnac interferometeric structure, the sensitivity of the proposed sensor is improved by approximately 57 times. In addition, under the same measurement bandwidth, the measurement range of PMF₁ mode is 9.3 times that of PMF₂ mode. Therefore, compared to the traditional vernier-effect-based fiber-optic temperature sensors, the dual-response-mode temperature sensor proposed in this paper not only exhibits superior detection sensitivity, but also enables effective adaptation to application scenarios requiring different detection ranges and sensitivity levels using the same spectral detection equipment, providing a new idea for developing tunable-performance fiber-optic temperature sensors.

The Fringe Projection Profilometry (FPP) system with a single exposure time or a single projection intensity is limited by the dynamic range of the camera, which can lead to overexposure and underexposure of the image, resulting in point cloud loss or reduced accuracy. To address this issue, unlike the pixel modulation method of projectors, we utilize the characteristics of color projectors where the intensity of the three-channel LED can be controlled independently. We propose a method for separating the projector's three-channel light intensity, combined with a color camera, to achieve single exposure and multi-intensity image acquisition. Further, the crosstalk coefficient is applied to predict the three-channel reflectance of the measured object. By integrating clustering and channel mapping, we establish a pixel-level mapping model between the projector's three-channel current and the camera's three-channel image intensity, which realizes the optimal projection current prediction and the high dynamic range (HDR) image acquisition. The proposed method allows for high-precision three-dimensional (3D) data acquisition of HDR scenes with a single exposure. The effectiveness of this method has been validated through experiments with standard planes and standard steps, showing a significant reduction in mean absolute error (44.6%) compared to existing single-exposure HDR methods. Additionally, the number of images required for acquisition is significantly reduced (by 70.8%) compared to multi-exposure fusion methods. This proposed method has great potential in various FPP-related fields.

We develop a single-molecule immunoassay detection system for flow-phase samples to enable early diagnosis of tumor biomarkers. The system includes an optical fluorescence imaging platform and an image processing algorithm. First, we developed a flow-phase single-molecule immunoassay detection method suitable for real-time detection of low-concentration, high-throughput samples. Second, we designed a set of fluorescence imaging detection platform compatible with microfluidic chips. Through the rational configuration of optical filters and beam splitters, high-resolution fluorescence imaging was achieved hyutilizing multi-module integration. Finally, based on the image detection and counting algorithm for out-of-foas particles, 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 immunoassay detection, showing promising potential for early cancer screening.

Soft polymer optical fiber (SPOF) has shown great potential in optical based wearable and implantable biosensors due to its excellent mechanical properties and optical guiding characteristics. However, the multimodality characteristics of SPOF limit their integration with traditional fiber optic sensors. This article introduces for the first time a flexible fiber optic vibration sensor based on laser interference technology, which can be applied to vibration measurement under high stretch conditions. This sensor utilizes elastic optical fibers made of polydimethylsiloxane (PDMS) as sensing elements, combined with phase generating carrier technology, to achieve vibration measurement at 50−260 Hz within the stretch range of 0−42%.

By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integral, where the effect of noncanonical strength, off-axis distance and vortex sign on spatial correlation singularities in far field is stressed. Furthermore, far-field OAM spectra and densities are also investigated, where the OAM detection and crosstalk probabilities are discussed. The results show that the number of dislocations of SCS always equals the sum of absolute values of topological charges for canonical or noncanonical vortex pairs. Although the sum of the product of each OAM mode and its power weight equals the algebraic sum of topological charges for canonical vortex pairs, the relationship no longer holds in the noncanonical case except for opposite-charge vortex pairs. The change of off-axis distance, noncanonical strength or coherence length can lead to a more dominant power of adjacent mode than the center detection mode, which also indicates that crosstalk probabilities of adjacent modes exceed the center detection probability. This work may provide potential applications in OAM-based optical communication, imaging, sensing and computing.

This paper proposes a high-speed measurement method of Mueller matrix 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 measurement frequency of Mueller matrix 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.

As an advanced tissue optical imaging technology, time-domain diffuse optical imaging (TD-DOI) enables quantitative reconstruction of absorption and reduced scattering coefficients in biological tissues through time-correlated single photon counting (TCSPC) systems, thereby allowing precise assessment of critical physiological parameters such as tissue oxygen metabolism and blood perfusion. However, constrained by the inherent hardware complexity and high cost of TCSPC systems, current implementations face challenges in achieving scalable clinical applications requiring in-vivo multichannel dynamic monitoring. This study innovatively proposes a dual-channel differential hybrid trigger reference signal strategy. By integrating differential time-to-digital converter (TDC) devices with photon counting techniques, we have established a stable and reliable time point spread function (TPSF) measurement system that achieves sub-nanosecond precision (±50 ps) in calibrating the temporal delay between laser synchronization signals and emitted photon events. Experimental validation demonstrates that the developed system attains a temporal resolution of 55 ps. Under photon counting rates of 2.3×10⁴ photons/s, the TPSF fluctuation coefficient remains consistently below 1.35% (1 s integration time). Optical properties inversion on tissue phantoms reveal mean reconstruction errors of 5.39% for absorption coefficient and 4.34% for reduced scattering coefficient. This technological advancement significantly enhances the feasibility of multichannel parallel detection in TD-DOI systems. Particularly suited for biomedical applications, such as dynamic monitoring of cerebral cortical oxygen saturation, it establishes a technical foundation for developing next-generation wearable optical brain function imaging devices.

With the breakthrough progress of mid-wave and long-wave infrared hyperspectral imaging technology, the military hyperspectral imaging system, with its unique feature recognition capability and covert reconnaissance advantages, has demonstrated significant strategic value in the field of modern battlefield situational awareness, e.g., real-time target identification, anti-camouflage reconnaissance, and dynamic monitoring of global military targets. In this study, a dual-band Offner-type spectral imaging system operating in the mid-wave infrared (3.7−4.8 μm) and long-wave infrared (7.7−9.5 μm) is designed for aerial detection applications based on a 320×240-pixel dual-color cooled infrared detector. The system adopts a hybrid refractive and refractive-reflective optical structure, and realizes a three-field-of-view switching zoom function of 32 mm, 200 mm and 800 mm. The optical system adopts the Offner spectroscopic structure, which effectively suppresses the primary aberration of the system; secondly, through the introduction of the secondary imaging relay system, it achieves 100% cold diaphragm matching and significantly reduces the cold reflection effect. Experimental tests show that the system exhibits excellent imaging performance in all bands and at different focal lengths: at a characteristic frequency of 17 lp/mm, the modulation transfer function approaches the diffraction limit, and temperature changes have little effect on imaging quality; optical image quality meets design specifications. The optical system is characterized by wide spectral response, large magnification ratio (25×) and fast field of view switching. The spectral resolution reaches 25 nm, and its imaging quality and spectral resolution meet the technical requirements of aviation photoelectric reconnaissance, which has important application value in military reconnaissance, security monitoring and environmental monitoring.

Stray light interference in vehicular LiDAR systems can reduce the signal-to-noise ratio and degrade detection efficiency. To mitigate this issue, this paper proposed a surface scattering modeling method based on the spectral power density function and total integrated scattering, which fits the bidirectional reflectance distribution function (BRDF) for various material surfaces. The model calculation results were highly consistent with the measured BRDF data, verifying the effectiveness of the method. Based on this model, the study systematically analyzed the sources and propagation paths of stray light in the long-focal-length receiving optics of vehicular LiDAR, with specific attention to scattering from the housing's inner walls, lens edges, and spacer ring surfaces. According to the simulation results, this paper put forward a number of stray light suppression measures, such as using structural components made of low-scattering materials, coating anti-reflection films on lens surfaces, and applying light-absorbing ink to the non-optical areas of lenses, etc. Furthermore, from optical design, signal processing and engineering optimization, the stray light suppression level of this LiDAR receiving optical system was evaluated in multiple dimensions. The results of the experiment showed that the level of stray radiation in the optimized system was significantly reduced: the point source transmittance (PST) outside the imaging field of view was reduced from 1e+0 to 1e-5, the PST in the field of view was reduced from 1e+2 to 1e-1, and the stray light contrast with the target signal was controlled below 10e-4. Additionally, the intensity of the detected echo signal is significantly improved, thereby effectively enhancing the detection performance of the LiDAR. This study provides a theoretical model and practical solutions for stray light suppression in vehicle-mounted LiDAR, offering valuable references for the design and optimization of high-sensitivity optical systems.

To address the demand for large field-of-view and high compactness in lightweight AR glasses equipped with cameras, this study proposes an optical design method incorporating a curved image plane. First, based on Gaussian optics theory, the curved image plane imaging system is theoretically analyzed. The Petzval surface curvature characteristics of various optical configurations are derived, and the performance advantages of the curved image plane are highlighted through comparative simulations of dual systems. Then, a wide-angle and compact optical system is designed using a segmented multi-objective optimization strategy. Finally, image quality evaluation and tolerance analysis are performed on the designed system. The compact optical system comprises five aspheric plastic lenses and a rear-mounted filter. It features a focal length of 3.1 mm, a field of view (FOV) up to 80°, and a total system length of only 4.07 mm. The design results show that at 223 lp/mm, the modulation transfer function (MTF) exceeds 0.32 across all fields. The maximum RMS spot radius is 2.41 μm, with a distortion of only 2.5%, and the relative illumination remains above 45% across the entire field. This work lays a foundation for the application of curved sensors and offers a technical reference for the design of wide-angle compact lenses.

To evaluate the laser-induced damage effects on visible-light imaging systems under realistic operational conditions, a detector module comprising a filter and a back-illuminated CMOS sensor was employed as the target. This study investigates the damage mechanisms induced by nanosecond pulsed lasers at wavelengths of 532 nm and 1064 nm. Initially, a series of experiments were conducted to characterize the typical damage behaviors resulting from laser irradiation. To address the limitations in observing internal thermal and mechanical responses during the experiments, a finite element simulation model was developed to analyze the interaction between the laser and the detector. The simulation enabled visualization of temperature and stress concentration phenomena that are difficult to capture through direct observation, thus providing valuable reference data for damage thresholds. The results from both the experiments and simulations indicate that the dominant damage mechanism is coupled thermo-mechanical failure. The measured multi-stage damage thresholds were 30.06 mJ/cm², 38.93 mJ/cm², 56.20 mJ/cm², and 102.17 mJ/cm² for 532 nm laser irradiation, and 38.62 mJ/cm², 50.09 mJ/cm², 116.31 mJ/cm², and 137.73 mJ/cm² for 1064 nm irradiation.

During the research and development process of the scientific research project, it was found that the beam deviation angle formula of a Rochon Prism in classical optical literature (for negative crystals) was incorrect. Therefore, an accurate expression for the beam deviation angle of a Rochon Prism was derived (distributed for negative and positive crystals), and the problem of design in the optical systems containing a Rochon Prism in the scientific research projects was solved. In response to the problem of small angles between the output two beams of light in general a Rochon Prism products, the expressions for the deviation angles of a Rochon Prism composed of negative and positive crystals were analyzed and derived. In addition, the deviation angles of a Rochon Prism composed of different crystal materials were analyzed and the expression was derived. By calculating and comparing with actual data, it is known that the beam deviation angle of a Rochon Prism made of different crystal materials is significantly higher than that of a Rochon Prism made of the same crystal material. For applications in the ultraviolet band, provide a specific design example of a large beam deviation angle for a Rochon Prism composed of heterogeneous crystal materials. This type of a Rochon Prism is composed of heterogeneous crystal materials, and according to the appropriate crystal arrangement order, a relatively large beam deviation angle can be obtained under the limitation of reasonable crystal thickness, which is obviously beneficial for the structural design of the polarization instruments and equipments.

This study addresses the urgent demand for 1018 nm single-frequency seed sources in the field of Rydberg microwave measurements by developing a widely tunable 1018 nm single-frequency fiber laser with a linewidth of 810 Hz and a relative intensity noise below −140 dB/Hz.The laser employs a distributed Bragg reflector (DBR) structure with an 8-mm-long ytterbium-doped fiber and incorporates a high-stability active temperature control system and a piezoelectric ceramic (PZT)-based fast frequency tuning device. The temperature control range was from 10 °C to 80 °C, and the temperature fluctuation of the DBR resonance cavity was only ±0.0005 °C within 2 hours at 25 °C temperature control. After experimental testing, the laser maintains a single longitudinal mode output at 25°C, with a linewidth of 810Hz, a temperature tuning range of more than 0.9 nm, and a fast tuning range of the PZT up to 10 GHz, there is no mode-hopping phenomenon in the tuning process. The relative intensity noise of a single-frequency laser is −150 dB/Hz in the low frequency band of 1 kHz, and below −140 dB/Hz when the frequency is greater than 1.5 MHz. This result shows that the laser output is low noise while achieving wide tuning.

Catadioptric space cameras are widely used in space exploration, However, temperature variations can degrade their imaging performance. To address this issue, this paper presents an athermal design for a catadioptric space camera operating over a wide temperature range. Initially, the temperature effects on optical elements, mechanical structures, and other components were analyzed, and convenient methods for thermal aberration compensation are summarized. Subsequently, taking a camera with a spectral range of 400–1000 nm, a focal length of 525 mm, and an F-number of 3.5 as the design case, an athermal solution is developed. By selecting appropriate materials for the mirror substrates and support structures, and using fused silica as the single lens material to correct aberrations, the optical system maintains stable performance in space environments. Final simulation results confirm that the optimized camera maintains a Modulation Transfer Function (MTF) value above 0.4 at 77 lp/mm (Nyquist frequency) over a temperature range of –60°C to 150°C. The camera exhibits stable material properties, excellent imaging quality, and consistent performance under extreme temperatures. This design demonstrates significant potential for applications in space exploration and related fields.

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 linear 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. Secondly, 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.

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 the relationship between the phase error and the direction of texture edge. Thus, a correction method for complex texture errors based on bidirectional fringe projection point cloud fitting is proposed. Theoretically, the bidirectional phase information obtained by projecting horizontal and vertical fringe patterns should yield perfect consistent point clouds. Thus, the method corrects the phase by minimizing the Euclidean distance between the corresponding points in the horizontal and vertical point clouds, ultimately obtain 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.

Addressing limitations in existing data processing methods for large-aperture flat mirror figure measurement – specifically low generality and susceptibility to environmental instabilities, this paper proposes a novel data processing approach. This method integrates ray tracing to generate a sensitivity matrix and applies it to process and analyze data obtained via the Ritchey-Common test. Consequently, high-precision figure detection of large-aperture flat mirrors is achieved. 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.

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 integrate enhanced 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.

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 using a monochrome camera avoids color crosstalk interference common in 3D reconstruction of colored objects.

This paper addresses the challenges of low overlap and mismatched point pairs in Geiger-mode avalanche photodiode (GM-APD) LiDAR point clouds under dynamic scanning conditions. To improve registration accuracy and robustness, an enhanced Iterative Closest Point (ICP) algorithm is proposed, integrating a bidirectional matching scheme and multi-resolution neighborhood expansion. First, a K-D tree-based bidirectional search identifies overlapping regions between consecutive frames, enabling accurate initial alignment. Then, a high-resolution neighborhood expansion approach, weighted by local curvature similarity, is applied to refine the transformation matrix and suppress mismatched correspondences. Finally, a cascaded compensation mechanism ensures global consistency across frames. Experiments demonstrate that our method achieves average distance errors of 0.21 m (2 km scene) and 0.10 m (400 m scene), effectively improving registration precision in dynamic scenarios and offering valuable support for 3D reconstruction.

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.

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.

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.

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.

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.

本文设计了一种由两个一端封堵的金属-绝缘体-金属（MIM）波导与一个的D形腔耦合组成表等离激元波导结构。使用有限元方法（FEM）模拟了该结构的传输特性、磁场分布以及折射率传感特性。在透射光谱中可以明显观察到多Fano共振现象。这些Fano共振是由于D形谐振腔的产生的共振离散态与一端封堵的MIM波导产生的连续状态之间相互耦合产生。通过系统地调整结构参数，研究了其对Fano共振调制的影响。此外，通过改变MIM波导中绝缘层的折射率研究了基于Fano共振折射率传感特性。结果表明，在第一个Fano共振峰处实现了最大1155 RIU/nm的灵敏度。这些研究对高灵敏度光子器件、微型传感器、未来新型片上传感的设计和研究提供了新的途径。

Metalens technology has been applied extensively in miniaturized and integrated infrared imaging systems. However, due to the high phase dispersion of unit structures, metalens often exhibits chromatic aberration, making broadband achromatic infrared imaging challenging to achieve. In this paper, six different unit structures based on chalcogenide glass are constructed, and their phase-dispersion parameters are analyzed to establish a database. On this basis, using chromatic aberration compensation and parameterized adjoint topology optimization, a broadband achromatic metalens with a numerical aperture of 0.5 is designed by arranging these six unit structures in the far-infrared band. Simulation results show that the metalens achieves near diffraction-limited focusing within the operating wavelength range of 9-11 µm, demonstrating the good performance of achromatic aberration with flat focusing efficiency of 54% - 58% across all wavelengths.

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.