In order to simulate dynamic scenes with high accuracy and high reliability, a short-wave infrared (SWIR) and mid-wave infrared (MWIR) multiband catadioptric common-aperture optical system is designed. The system combines the advantages of reflection, refraction and common-aperture optical paths, The system includes a main optical system, a short-wave optical systems and a midwave optical system, all designed independently. The initial structure of the optical system is obtained according to theoretical calculation, and the optical parameters are further detailed by optical design software. Finally, the sub-systems are combined according to the principle of pupil matching. The systems is image quality is further optimized, and the system design's rationality is verified by the simulation of the modulation transfer function (MTF) and distortion. The designed short-wave optical system has a field angle of ±0.107°, a focal length of 2500 mm, an entry pupil size of 300 mm, an MTF that reaches the diffraction limit, and less than 0.3% distortion. The mid-wave optical system has a field angle of ±0.65°, a focal length of 750 mm, an entry pupil size of 300 mm, an MTF close to the diffraction limit, and less than 1% distortion. The system has good image quality, small size and strong practicability. It has great application potential in the field of photoelectric tracking and space detection.

Aiming at the problems in existing infrared and visible image fusion methods, such as the difficulty in fully extracting and preserving the source image details, contrast, and blurred texture details, this paper proposes an infrared and visible image fusion method guided by cross-domain interactive attention and contrastive learning. First, a dual-branch skip connection detail enhancement network was designed to separately extract and enhance detail information from infrared and visible images, using skip connections to prevent information loss and generate enhanced detail images. Next, a fusion network combining a dual-branch encoder and cross-domain interactive attention module was constructed to ensure sufficient feature interaction during fusion, and the decoder was used to reconstruct the final fused image. Then, a contrastive learning network was introduced, performing shallow and deep attribute and content contrastive learning from the contrastive learning block, optimizing feature representation, and further improving the performance of the fusion network. Finally, to constrain network training and retain the inherent features of the source images, a contrast-based loss function was designed to assist in preserving source image information during fusion. The proposed method is qualitatively and quantitatively compared with current state-of-the-art fusion methods. Experimental results show that the eight objective evaluation metrics of the proposed method significantly outperform the comparison methods on the TNO, MSRS, and RoadSence datasets. The fused images produced by the proposed method have rich detail textures, enhanced sharpness, and contrast, effectively improving target recognition and environmental perception in real-world applications such as road traffic and security surveillance.

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.

As an advanced device for observing atmospheric winds, the spaceborne Doppler Asymmetric Spatial Heterodyne (DASH) interferometer also encounters challenges associated with phase distortion, particularly in limb sounding scenarios. This paper discusses interferogram modeling and phase distortion correction techniques for spaceborne DASH interferometers. The modeling of phase distortion interferograms with and without Doppler shift for limb observation was conducted, and the effectiveness of the analytical expression was verified through numerical simulation. The simulation results indicate that errors propagate layer by layer while using the onion-peeling inversion algorithm to handle phase-distorted interferograms. In contrast, the phase distortion correction algorithm can achieve effective correction. This phase correction method can be successfully applied to correct phase distortions in the interferograms of the spaceborne DASH interferometer, providing a feasible solution to enhance its measurement accuracy.

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.

To address issues related to the accurate control of infrared band film thickness and precise wavelength positioning, this study employs the LabVIEW programming language to develop a dynamic monitoring and compensation technology for optical film thickness, based on an optical film thickness monitoring system. Based on the principles of light interference and optical thin film design, a mathematical model is constructed using the photoelectric polarimetric method. This study focuses on resolving stopping errors and filtering noise at extremum points, thereby accurately restoring the real-time monitoring data of light intensity. The system achieves real-time and synchronous fitting of the film’s transmittance curve, calculates and fits the stopping point corresponding to the extremum of the film thickness. To validate the reliability and stability of the optical control system, a 1064 nm narrow-band filter film was fabricated. The results indicate that the peak transmittance of the 1064 nm narrow-band filter film reached 91.5%, with a pass-band half-width of 5 nm. The error of the monitoring system was calculated to be less than 0.01%.

To identify the vortex beams orbital angular momentum (OAM) with imbalanced labels, this paper proposes a derived model based on global cost SMOTE and deep extreme learning machine (DELM). Unlike typical machine learning methods, the proposed model can obtain the analytical expression of the mapping model. It avoids repeated parameter optimization, thus building a suitable model for time-varying engineering applications. In the data generation stage, the inverse matrix of covariance was used to remove the influence of dimensions, and the differences among samples with in the same category were effectively measured. In the model selection stage, considering the transmission characteristics of light signals in atmospheric turbulence, the DELM was adopted to quantify the mapping relationship between light spots and labels. Then the FISTA algorithm was used to calculate the model’s analytical expression. Experiments were carried out on different intensity atmospheric turbulence data sets. The representative comparative methods include WELM and K-nearest neighbor. Experimental results show that the proposed method’s root mean square error (RMSE) achieves 0.2049 and 0.0894, which are superior to the comparison methods under different turbulence intensities. This proves that the proposed method can fully explore the characteristics of OAM spot collection and has a better recognition effect.

This paper provides a theoretical model for studying typical airport ground materials’ polarization characteristics. This model is required for the development of polarization imaging instruments. First, serious shadow masking effects were analyzed based on the P-G model. These effects occur when light is incident at a large angle. Then, the shadow masking function was optimized using the spherical trigonometry formula. This optimization equates the specular reflection point to a three-dimensional sphere. Due to the unique dispersion characteristics of different targets, a new bidirectional polarization distribution function (BPDF) model was introduced to replace the traditional BRDF parameter affected by wavelength and body scattering. The new BPDF model integrates diffuse reflection and body scattering. In the experimental stage, the accuracy of the line polarization degree was calibrated. The line polarization degree of typical airport ground material was fitted with model parameters. This fitting was based on the dynamic TS algorithm through multi-angle BRDF experiments. The fitting model's six parameters were used to obtain the root mean square roughness parameter. This process verified the validity of the modified BPDF model. In the simulation stage, the root mean square error (RMSE) was used as the accuracy index. The modified BPDF model, control model, and experimental results were compared to analyze the effects of detection, azimuth, and incidence angles on polarization characteristics. The accuracies of the four experimental targets improved by 4.39%, 4.00%, 4.17%, and 5.26% compared with the control model. The RMSE was less than 0.05 for large detection angles. This allows the modified model to study polarization characteristics of rough materials like airport ground targets. Finally, the effect of fitting parameters on polarization characteristics was simulated. Results show that line polarization is positively related to the refractive index and inversely related to the surface roughness. The accuracy of the modified BPDF model is thus proved. This provides ideas for studying polarization characteristics of airport ground targets.

Organic-inorganic hybrid lead-free perovskites have garnered significant attention due to their non-biotoxicity and environmental sustainability. Among these materials, MA₃Sb₂I₉, with its stable zero-dimensional (0D) structure and lead-free nature, shows great promise for stable and efficient photodetection applications. In this study, we employ a MACl post-treatment to enhance the quality of MA₃Sb₂I₉ perovskite thin films fabricated through antisolvent processing. This treatment facilitated the formation of Cl-Sb bond interactions between MACl and the perovskite thin films, effectively passivating the I⁻ vacancies and grain boundary defects on the MA₃Sb₂I₉ thin-film surface. This process not only improve the surface morphology and crystallinity of the thin film but also reduced the defect states density of the surface, thereby enhancing carrier extraction and transport efficiency. Consequently, the sensitivity of self-powered photodetectors based on the optimized thin-film preparation increased from 3.89 × 10⁷ Jones to 5.72 × 10⁸ Jones, representing an improvement by one order of magnitude. Furthermore, the rise and fall times were shortened from 37/76 ms to 31/37 ms, respectively, indicating an enhancement in the response speed of the devices.

Accurate hypothesis evaluation metrics are crucial for point cloud registration, as they facilitate the identification of correct hypotheses during the evaluation process. However, existing metrics often short in this regard. Traditional metrics, such as inlier count, are highly sensitive to parameter changes and vary significantly across different application scenarios. Recent correspondence-based metrics perform inadequately under low-parameter settings, while point-cloud-based metrics are computationally expensive. To address these limitations, this paper proposes a novel metric that integrates confidence scores of correspondences, obtained through a Triangle Voting (TV) method, with correspondence-based metrics. The proposed metric assumes that a good hypothesis aligns correspondences with high-confidence scores very closely, thereby yielding higher score contributions. We further introduce two enhancement to improve the effectiveness of inlier-based metrics with confidence scores: (1) ignoring the distance of inliers with minor transformation errors, and (2) suppressing the erroneous high-score contributions caused by numerous low-confidence correspondences. Comparative experiments conducted on three datasets demonstrate the superiority of the proposed metric over all previously known correspondence-based metrics. The proposed metric achieves registration performance enhancements ranging from 1% to 16.95% and time savings ranging from 1.67% to 10.79% under default parameter settings. Moreover, it strikes a better balance among time consumption, robustness, and registration performance. Specifically, the improved inlier count metric exhibits highly robust and accurate performance. In conclusion, the proposed metric can accurately identify the more correct hypothesis during the hypothesis evaluation stage of RANSAC, thereby enabling precise point cloud registration.

The sensitivity of the phase-sensitive optical time-domain reflecting (Φ-OTDR) system is limited by the system’s intrinsic noise, such as the laser’s phase noise, the erbium-doped fiber amplifier’s spontaneous emission noise, and the photodetector’s shot and thermal noise, as well as random environment of noise. Therefore, we investigate the noise reduction algorithm based on the optical time-domain reflecting data to improve the system’s signal-to-noise ratio (SNR) without degrading its frequency response range. Turthermore, we propose a Savitzky-Golay smoothing algorithm by selecting a slidable fixed-length window to process OTDR data for the SNR improvement while maintaining the system sampling frequency. Then, we built the experimental system to demonstrate the results. The experimental results show that by using the Savitzky-Golay smoothing algorithm, the SNR of the system is improved by 5.41 dB relative to the difference method with the original data, and the SNR is improved by 3.39 dB and 5.05 dB, compared to the commonly used cumulative averaging method and sliding averaging method, respectively. It is demonstrated that the Savitzky-Golay smoothing algorithm can improve the sensitivity and accuracy of the Φ-OTDR system, which helps to sense weak vibration events accurately and reduce false alarm rates.

The counter-rotating prisms Atmospheric Dispersion Corrector (ADC) has been widely used for the calibration of large-aperture astronomical telescopes. To achieve an optimal design method for the counter-rotating prism ADC, effectively compensate for dispersion, and suppress optical axis drift introduced by the ADC, this study establishes a vector model for ray tracing of the counter-rotating prism ADC based on traditional atmospheric dispersion compensation theory. The vector models of dispersion compensation and optical axis drift are then derived. Using this mathematical model, the impacts of ADCs with different parameters on the dispersion compensation, prism rotation angle, and optical axis drift are simulated and analyzed. The simulation results show that when compensating for the same atmospheric dispersion with different material combinations and bonding types, the rotation angle of the prism group remains relatively consistent, with differences increasing as the zenith angle increases. Choosing materials with similar refractive indices near the central wavelength reduces chromatic aberration in the ADC output light and improves dispersion compensation. When compensating for large dispersions at different zenith angles, the optical axis offset angle of the system decreases as the number of bonded surfaces increases. Specifically, each additional bonded surface can reduce the optical axis drift angle by one order of magnitude. In practical ADC design, dispersion can be effectively compensated, and optical axis drift can be suppressed by controlling the number of bonded surfaces and material selection.

Stripe projection technology is widely used in 3D measurement and surface morphology reconstruction, where phase quality is a critical determinant of measurement accuracy. However, the nonlinear relationship between input and output light intensity is a major source of phase error. To address this issue, this paper introduces a novel system nonlinear active correction method. This method captures the variation pattern between input and output light intensity by projecting a small number of uniform gray-scale images onto a standard plane. This pattern is then integrated with active system nonlinear correction to construct a system nonlinear model based on the input-output light intensity variation. Genetic algorithms are used to optimize the coding values, which are then used to actively correct the projected fringes via fringe coding. The corrected fringes effectively reduce the influence of nonlinear effects, thereby significantly improving the quality of phase acquisition. To validate the proposed method, computer simulations were performed using three-step phase shifting. The results showed an 88% reduction in the standard error and an 85.5% reduction in the maximum error. In actual standard plane experiments, the corrected standard phase error decreased from 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.

This study investigates the transmission loss characteristics of gallium nitride (GaN) planar optical waveguides using a finite element simulation model based on the Beam Propagation Method (BPM). To address the high transmission loss in conventional GaN waveguides, we propose process optimization solutions and develop a comprehensive transmission loss model for systematic analysis. Our investigation focuses on comparing the effects of top etching and back thinning processes on waveguide optimization. Both processes significantly reduce the waveguide transmission loss, with the top etching process reducing loss from 2.29 dB/mm to 0.19 dB/mm and the back thinning process reducing it to 0.24 dB/mm. Additionally, we analyze the impact of manufacturing defects, such as sidewall angles and surface roughness, on transmission loss. Through parameter optimization, we identify the key dimensions necessary for single mode light transmission. This study provides a theoretical basis and process guidance for the development of low-loss GaN waveguides.

In comparison with traditional photoelectric displacement measurement technologies, displacement measurement methods based on digital image processing methods exhibit superior fault tolerance and flexibility, making them a current research hotspot. To achieve high-precision and high-reliability angular displacement measurement, an image-based angular displacement measurement system based on Manchester coding is proposed. First, a single code-channel raster code disc was designed using Manchester coding based on M-sequence pseudo-random coding. A digital image sensor was then used to construct an optical path for capturing patterns on the raster code disc. Subsequently, a decoding recognition algorithm tailored to the coded patterns was developed. Additionally, edge positioning and sub-pixel subdivision algorithms for coded marker edge pattern fitting were proposed to further enhance the system’s resolution. The proposed method was then experimentally validated. The experimental results demonstrated that the system achieved a resolving power of 21 bits and an accuracy of 1.73 arcseconds with a 100 mm grating code disc. This research provides a foundation for the development of highly reliable and high-performance photoelectric angular displacement measurement technologies. Image-based angular displacement measurement system based on Manchester coding

Terahertz molecular fingerprinting is a promising method for label-free detection, particularly for micro or trace amount samples in practical applications. However, the wavelength of terahertz waves is much larger than the size of the molecules to be tested, resulting in a weak interaction between the waves and the matter. To address this challenge, additional structures are needed to enhance the absorption of electromagnetic waves by trace amount samples. In this study, we constructed an inverted asymmetric dielectric grating structure on a metal substrate. By utilizing guided-mode resonance (GMR) and a bound state in the continuum (BIC) effect, the terahertz absorption spectrum of thin film samples was significantly enhanced. The enhanced absorption spectra can be easily obtained by measuring the reflected absorption signal. The samples are coated on the flat back of the inverted dielectric grating, which simplifies the preparation process. For instance, when the thickness of an α-lactose film is 0.2 μm, the absorption enhancement factor reaches 236. This study provides a new method for detecting trace analytes in the terahertz band.

To realize effective co-phasing adjustment in large-aperture sparse-aperture telescopes, a multichannel stripe tracking approach is employed, allowing simultaneous interferometric measurements of multiple optical paths and circumventing the need for pairwise measurements along the mirror boundaries in traditional interferometric methods. This approach enhances detection efficiency and reduces system complexity. Here, the principles of the multibeam interference process and construction of a co-phasing detection module based on direct optical fiber connections were analyzed using wavefront optics theory. Error analysis was conducted on the system surface obtained through multipath interference. Potential applications of the interferometric method were explored. Finally, the principle is verified by experiment, and interferometric fringe contrast better than 0.4 is achieved through that field calibration and incoherent digital synthesis. The dynamic range of the measurement exceeds 10 times of the center wavelength of the working band (1550 nm). Moreover, a resolution better than one-tenth of the working center wavelength (1550 nm) was achieved. Simultaneous three-beam interference can be achieved, leading to a 50% improvement in detection efficiency. This method can effectively enhance the efficiency of sparse aperture telescope co-phasing, meeting the requirements for observations of 8–10 m telescopes. This study provides a technological foundation for observing distant and faint celestial objects.

The CMOS image sensor is one of the most widely used in aerospace, medical imaging, industrial detection, military reconnaissance, and other fields. The laser interference and damage to CMOS image sensors have also become a research hotspot in related fields at home and abroad. To investigate the impact of pulsed laser on back-illuminated CMOS image sensors, we select the Sony IMX178 back-illuminated CMOS image sensor as the target material. Based on the heat conduction equation, the finite element simulation software COMSOL Multiphysics was used to compare and calculate the temperature distribution of the CMOS image sensor under the irradiation of single-pulse lasers with different parameters. The calculation results indicate that the point damage thresholds of the sensor under the effects of single-pulse lasers at 532 nm (1 ns), 1064 nm (1 ns), 532 nm (30 ps), and 1064 nm (30 ps) are respectively 61.12 mJ/cm², 75.76 mJ/cm^2, 31.83 mJ/cm², and 37.43 mJ/cm². Subsequently, an experimental study is conducted on the laser irradiation effects of back-illuminated CMOS image sensors. The experimental results demonstrate that the image sensor exhibits a lower damage threshold under the influence of 532 nm pulsed lasers compared to 1064 nm pulsed lasers; picosecond pulsed lasers, with higher peak power compared to nanosecond pulsed lasers, are more prone to causing point damage. The calculated point damage thresholds are highly consistent with the experimental results.

Scanning interference field exposure (SBIL) is an effective way to fabricate monomeric large-area high-precision gratings. Using dual-frequency laser interferometer feedback table position to splice interference fringes accurately, the measurement error will inevitably introduce grating engraving error and reduce the diffraction wavefront quality of grating. The intrinsic error caused by the laser interferometer’s structure was analyzed, and the evaluation method of the intrinsic error index of the laser interferometer in complex environments was proposed. The theoretical models of dead path error and measuring optical path variation error combined with actual working conditions and empirical formulas were established. The coupling relationship between rotation and displacement of any table point was deduced by constructing translation and rotation operators, and the measurement errors under different table attitude roll angles were simulated. The displacement error experiment and grating scanning exposure experiment were carried out. The experimental results show that the displacement error is consistent with the theoretical calculation results. The diffraction wavefront of the 200 mm×200 mm grating is 0.278λ@632.8 nm. The analytical method in this paper connects the transmission link between the grating diffraction wavefront and the measurement error, laying a theoretical and experimental foundation for the fabrication of meter-size nano-precision holographic gratings.

Third-order Raman fiber amplifiers are used in long-haul unrepeated optical transmission due to their higher gain and lower noise figure. Third-order Raman fiber amplifiers are advanced Raman amplification technology. There is currently very limited research on it in China. The relationship between the pump configuration and the amplifier’s performance remains unclear. Therefore, this paper analyzes the influence of second-order pump seed light on third-order Raman fiber amplifiers through experiments. First, the feasibility of not using second-order pump seed light was qualitatively analyzed. Then, it was experimentally verified that in the absence of second-order pump seed light, the third-order Raman fiber amplifier can still achieve signal light gain but at decreased efficiency. A 47-channel 200 km wavelength division multiplexing transmission system was constructed. The experimental results show that the third-order Raman fiber amplifier can amplify the signal light without the second-order pump seed light. However, introducing the second-order pump seed light can significantly improve its performance. A second-order pump seed light with only 25 mW can achieve a minimum signal power gain of 3.7 dB, an average gain of 6 dB, and an average signal-to-noise ratio gain of 1.6 dB. Eliminating second-order pump seed light can reduce costs, but introducing a second-order pump seed light brings significant performance improvements to third-order Raman amplifiers.

Due to spacecraft’s volume and weight constraints, it is challenging to simultaneously obtain large aperture, high resolution, and hyperspectral information in spaceborne remote sensing systems. We propose a novel hyperspectral imaging system that utilizes a shared primary and secondary mirror design and a coaxial five-mirror optical path for multi-channel separation. By integrating Offner convex grating spectroscopy, the system enables hyperspectral detection from the visible to the long-wave infrared spectrum. Design results indicate that with a primary mirror diameter of 1000 mm at an altitude of 500 km, the spatial resolution in the visible and short-wave bands exceeds 2 m, in the mid-wave band exceeds 3 m, in the long-wave band exceeds 6 m, and the panchromatic resolution is better than 1 m. The system achieves a full field of view of 2.3°, accommodating a swath width of 20 km for detection. To enhance the system's aberration and distortion correction capabilities, high-order aspheric elements were incorporated to create a telecentric optical path, ensuring optimal matching between the telescope and the spectrometer. Furthermore, we propose housing the spectrometer module in a cooling chamber to effectively mitigate the impact of background radiation from the optical structure on image quality. The final design demonstrates excellent imaging quality, a simple layout, and a compact structure, enabling the simultaneous acquisition of high spectral information across the entire spectrum. This system has broad applications in satellite-based earth observation and imaging.

We present a topological charge difference detection technique for the orbital angular momentum of vortex beams. In this technique, by utilizing two vortex beams with distinct topological charges, first a periodic difference pattern is generated. The orbital angular momentum of the vortex beam to be measured can then be quickly and accurately calculated by reading the number of spots in one period. Traditional interference and diffraction methods require the reception of the complete vortex beam. In contrast, the topological charge difference method only requires the reception of a small amount of vortex beam to measure. This has significant advantages in the measurement of high-order and large-scale vortex beams. It has potential applications in long-distance free-space optical communication of vortex beams.

Multiple functional metasurfaces with high information capacity have attracted considerable attention from researchers. This study proposes a 2-bit tunable decoupled coded metasurface designed for the terahertz band, which utilizes the tunable properties of Dirac semimetals (DSM) to create a novel multilayer structure. By incorporating both geometric and propagating phases into the metasurface design, we can effectively control the electromagnetic wave. When the Fermi energy level of the DSM is set at 6 meV with 80 meV, the electromagnetic wave is manipulated by the DSM patch with the gold patch embedded in the DSM film, operating at a frequency of 1.3 THz and 1.4 THz. Both modes enable independent control of beam splitting under left-rotating circularly polarized (LCP) and right-rotating circularly polarized (RCP) wave excitation, resulting in the generation of vortex beams with distinct orbital angular momentum (OAM) modes. The findings of this study hold significant potential for enhancing information capacity and polarization multiplexing techniques in wireless communications.

In traditional multi-line laser 3D reconstruction technology, due to the inevitable noise affecting the multi-line laser lines, the extracted laser center coordinates often contain specific errors. These errors can lead to the inability to obtain high-precision 3D data when using matching points found based on epipolar constraints for 3D reconstruction directly. To address this issue, we propose a method based on geometric estimation to achieve 3D reconstruction of multi-line lasers. First, by calibrating the quadratic surface equations of the multi-line laser, combined with the binocular epipolar constraint method, the initial matching points of the multi-line laser can be calculated. After finding the correct initial matching points, a geometric distance minimization estimation model can be established using the distance constraint from points to epipolar lines. This geometric distance refers to the distance from the laser center points in the left and right images to their corresponding epipolar lines. New matching points that better conform to the epipolar constraints can be recalculated through this geometric distance minimization optimization estimation. Finally, these new matching points can be used to complete the 3D reconstruction of the multi-line laser. Compared to the traditional method based on epipolar constraints, the algorithm proposed in this paper performs better in matching and accuracy. The accuracy of the final 3D reconstruction can reach about 0.02 mm. This method can significantly improve the overall accuracy of binocular multi-line laser reconstruction, thereby obtaining more accurate and reliable 3D data.

In order to solve problems involved in high-precision surface map testing of coaxial high-order aspherical surfaces, this paper proposes a null compensation testing method based on CGH. Based on this method, the separation of the diffraction order in the coaxial aspherical compensation design can be effectively realized, and the null compensation design of the mirror to be measured can also be realized. Combined with engineering examples, this paper realizes a null compensation testing design for a coaxial high-order aspherical mirror with a 260 mm aperture. The CGH design results show that the theoretical design testing residual can reach 0 nm RMS value based on the design method described in this paper. The practical testing of the coaxial high-order aspherical mirror was also completed. To further analyze the testing results, error analysis was carried out on the error source in the testing process, to verify the reliability and accuracy of the method.

This paper proposes a novel modified uni-traveling-carrier photodiode (MUTC-PD) featuring an electric field regulation layer: a p-type doped thin layer inserted behind the PD’s n-doped cliff layer. This electric field regulation layer enhances the PD’s performance by not only reducing and smoothing the electric field intensity in the collector layer, allowing photo-generated electrons to transit at peak drift velocity, but also improving the electric field intensity in the depleted absorber layer and optimizing the photo-generated carriers’ saturated transit performance. Additionally, the proposed design improves the PD’s parasitic capacitance effect by incorporating a long collector layer designed to reduce the PD’s junction capacitance. The electron’s peak drift velocity compensates for the lost transit time. Thus optimizing the 3 dB bandwidth of the PD’s photo response. The final performance optimization obtains a MUTC-PD with a 3 dB bandwidth of 68 GHz at a responsivity of 0.502 A/W, making it suitable for 100 Gbit/s optical receivers.

Precise timing plays a vital roel in national economic development, scientific and technological progress, national defense and military security. The optical frequency standard based on two-photon transition is expected to become a practical miniaturized optical frequency standard due to its significant advantages such as high stability, good reproducibility and easy miniaturization. In this paper, the basic principle of two-photon transition is briefly described, and the research status and progress of rubidium atomic optical frequency standards based on two-photon transition at home and abroad are introduced. Finally, it is concluded that the future development trends of rubidium atomic optical frequency standards based on two-photon transition is system miniaturization, performance improvement, integrated application and engineering.

In phase-shifting profilometry, the non-standard phase-shifting profilometry combined with the temporal phase unwrapping algorithm requires fewer fringe patterns, thereby achieving higher measurement efficiency. Given that fringe frequency has a significant effect on measurement accuracy, this paper analyzes phase errors in the temporal phase unwrapping of the non-standard phase-shifting profilometry and further evaluates its reliability. It is found that the reliability of phase unwrapping is closely related to the allocation of fringe frequencies. Consequently, an optimal fringe frequency allocation strategy is proposed. Based on this strategy, this paper conducts comparative experiments on different frequency combinations of non-standard phase-shifting profilometry, and the experimental results show that compared with the non-optimal frequency combinations of the 3f_h1+2f_h2+2f_h3 heterodyne algorithm, the average error rate of the frequency combination proposed in this paper is reduced by 62.96%; compared with the non-optimal frequency combinations of the 2f_h+2f_m+3f_l hierarchical algorithm, the average error rate of the frequency combination proposed in this paper is reduced by 49.23%.

In order to explore the effect of titanium dioxide (TiO₂)/poly(sodium 4-styrenesulfonate) (PSS) nanofilms on the Kretschmann-type surface plasmon resonance sensor, the spectral changes of the sensor after depositing TiO₂/PSS nanofilms of different thicknesses were systematically studied. The reasons for the spectral changes were further explained and discussed theoretically. First, TiO₂/PSS multilayer films were deposited in situ on the surface of the glass chip sputtered with a gold layer via electrostatic layer-by-layer self-assembly technology, and the corresponding reflection spectra of the sensor were recorded in real time. Then, the original reflectance spectrum data was processed to make the spectral curve clearer and more visible. Finally, the experimental results were simulated and analyzed using MATLAB software programming. The results show that as the number of TiO₂/PSS bilayers increased, four different types of reflection peaks successively appeared in the sensor’s spectra in the 450−900 nm wavelength range. The four types of reflection peaks correspond to the surface plasmon resonance mode, the first-order mode, the second-order mode, and the third-order mode of the transverse magnetic mode of the sensor, respectively. This indicates that the Kretschmann-type sensor’s sensing mode and reflection spectrum type can be modulated by controlling the thickness of TiO₂/PSS thin films.

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.

In this paper, a coal pyrolysis HCN gas concentration detection system based on thermogravimetry-tunable diode laser absorption spectroscopy (TG-TDLAS) was successfully constructed, and the stability and sensitivity of the system were further improved by combining wavelength modulation technology. Taking advantage of the characteristics of HCN with high absorption intensity at wavelength 1531 nm and less interference by common gases in the atmosphere, the HCN concentration information was obtained by second harmonic signal processing. A high-precision flow controller is used to obtain HCN from 5×10^-6 mol/mol to 20×10^-6 mol/mol using a 99% standard nitrogen dilution ratio, and the measurement data is calibrated. The experimental results show that the linear correlation coefficient R2 of HCN reaches 0.9978. Then, the effects of different coal types, heating rate, and coal particle size on pyrolysis were discussed, as well as the relationship between the coal samples’ weight loss rate and the amount of HCN concentration released. The release characteristics of HCN and the nonisothermal pyrolysis kinetics in the volatile matter of three coal types with different coalification degrees were analyzed. A pyrolysis kinetic model was established by dividing the pyrolysis temperature stages, and the activation energy and frequency factors of varying coal types at different heating rates were calculated. The results show that the HCN emission is closely related to the degree of coalification and nitrogen content of coal types. The lower the degree of coalification, the higher the nitrogen content and the more HCN emitted. Under the fixed pyrolysis final temperature, an increase in the heating rate will increase the amount of HCN released. With the decrease in coal particle size, the time of HCN release from the pyrolysis reaction will be delayed, and the HCN concentration will decrease. There was a different correspondence between the release of HCN concentration and the coal samples’ weight loss rate in different pyrolysis stages. The more intense the pyrolysis reaction, the greater the proportion of HCN concentration released to the coal samples’ weight loss rate. This study provides an important experimental basis for further evaluation of the toxicity of HCN during coal pyrolysis reactions.

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.

Rapid determination of rare earth elements (REEs) in liquid-phase samples is of great significance in the fields of ion-adsorption rare earth resource exploration and exploitation, quality control of extraction processes, recycling of rare earth resources, and nuclear industry wastewater monitoring. In order to reduce the detection limit of REEs in liquid samples by laser-induced breakdown spectroscopy (LIBS), superhydrophobic array-assisted spark-enhanced laser-induced breakdown spectroscopy (SHA-SD-LIBS) was used in this study to determine the REEs in liquid-phase samples. Optimal experimental conditions were chosen to measure the REEs with the parameters of La II 394.91 nm, Er 402.051 nm, Ce II 418.66 nm, Nd II 424.738 nm, Gd II 443.063 nm, and Pr 492.46 nm as the characteristic spectral lines, and the calibration curves were established for the quantitative analysis of the solutions of six rare earth elements (La, Er, Ce, Nd, Gd and Pr) with different concentrations. The results show that the fit coefficients R² of the calibration curves were above 0.99. The corresponding detection limits were 0.007 μg/mL, 0.045 μg/mL, 0.011 μg/mL, 0.019 μg/mL, 0.041 μg/mL, and 0.008 μg/mL. The proposed method is a simple, low-cost, and highly efficient way to improve the quality of the liquid-phase sample. Compared with the conventional LIBS method, the proposed method can significantly reduce the detection limit of REEs in liquid phase samples with simple sample preparation and low cost. It can serve as a basis for new rapid and accurate methods of measuring rare earth element types and contents in liquid phase samples.

For segmented detectors, surface flatness is critical as it directly influences both energy resolution and image clarity. Additionally, the limited adjustment range of the segmented detectors necessitates precise benchmark construction. This paper proposes an architecture for detecting detector flatness based on optical fiber interconnection. By measuring the dispersion fringes for coplanar adjustment, the final adjustment residual is improved to better than 300 nm. This result validates the feasibility of the proposed technology and provides significant technical support for the development of next-generation large-aperture sky survey equipment.

To detect gravitational waves in space, the telescope and optical platform require high stability and reliability. However, the cantilevered design presents challenges, especially in the glass-metal hetero-bonding process. This study focuses on the analysis and experimental research of the bonding layer in the integrated structure. By optimizing the structural configuration and selecting suitable bonding processes, the reliability of the telescope system is enhanced. The research indicates that the use of J-133 adhesive achieves the best performance, with a bonding layer thickness of 0.30 mm and a metal substrate surface roughness of Ra 0.8. These findings significantly enhance the reliability of the optical system while minimizing potential risks.

Owing to the low p-type doping efficiency of GaN-based ultraviolet (UV) vertical-cavity surface-emitting laser (VCSEL) hole injection layers (HILs), effective hole injection in multi-quantum wells (MQW) is not achieved, significantly limiting the photoelectric performance of UV VCSELs. By improving hole injection efficiency, the hole concentration in the HIL is increased, and the hole barrier at the electron barrier layer (EBL)/HIL interface is decreased. This minimises the hindering effect of hole injection. In this study, we developed a slope-shaped HIL and an EBL structure in AlGaN-based UV VCSELs. A mathematical model of this structure was established using a commercial software, photonic integrated circuit simulator in three-dimension (PICS3D). We conducted simulations and theoretical analyses of the band structure and carrier concentration. Introducing polarisation doping through the Al composition gradient in the HIL enhanced the hole concentration, thereby improving the hole injection efficiency. Furthermore, modifying the EBL eliminated the abrupt potential barrier for holes at the HIL/EBL interface, smoothing the valence band. This improved the stimulated radiative recombination rate in the MQW, increasing the laser power. Therefore, the sloped p-type layer can enhance the optoelectronic performance of UV VCSELs.

This paper describes what is thought to be the first generation of a continuous wave deep ultraviolet laser at 275 nm by efficient frequency doubling of a blue-diode-pumped Pr:YLF laser at 550 nm. A TEM₀₀ mode deep UV laser radiation at 275 nm with an output power of 351 mW was obtained through the use of novel methods of coating and LD collimating. The authors could not find any prior reports on a Pr:YLF laser operating at 275 nm and believe this paper is the first.

Laser communication utilizes light waves as the transmission medium. It offers many advantages, including high data rates, expansive bandwidth, compactness, robust interference resistance, and superior confidentiality. It has the critical capability to enable high-speed transmission and secure operation of space information networks. Prominent research institutions have committed to studying a series of challenges that need to be solved in the process of networking laser communication technology, including point-to-multipoint simultaneous laser communication, all-optical switching and forwarding of multi-channel signals within nodes, node dynamic random access, and network topology design. Numerous demonstration and verification experiments have been conducted, with a subset of these research results finding practical applications. Based on the analysis and discussion of space laser communication networking technology, this paper summarizes the development of laser communication networking technology both domestically and internationally, focusing on the application of laser communication networking technology in the fields of satellite constellations, satellite relays, and aviation networks; furthermore, it presents a review of pertinent domestic research methodologies, experimental validations, and technical solutions; finally, it predicts the development trend of laser communication networking technology and applications.

The Terahertz wave possesses characteristics of high penetration, low energy, and fingerprint spectrum, etc., making it widely used in the detection field. Therefore, developing a Terahertz wave detection optical imaging system holds substantial significance and wide application prospects. Firstly, we refer to the structure of Tessar objective lens, which consists four lenses. The balance equations of aberration for the system were established through the application of the aberration theory of the paraxial optical system. Subsequently, we provide a solution function and method of the initial structure parameters of the system. Then, we combine it with optical design software to further correct the aberration of the system. Finally, we design a Terahertz wave detection optical imaging system with a large aperture. The optical system consists of four coaxial refractive lenses with a total focal length of 70 mm, an F-number of 1.4, and a full field of view angle of 8°. The value of modulation transfer function (MTF) in the range of full field of view angle is greater than 0.32 at the Nyquist frequency of 10 lp/mm, and the root mean square (RMS) radius of the diffused spot in each field of view is less than the airy disk radius. Finally, the paper analyzes and discusses the various tolerance types of the system. The results indicate that the Terahertz wave detection optical imaging system, designed in this paper, has a large aperture, a simple, compact form, a lightweight structure, excellent imaging performance and simple processing, which meets the design requirements, and it has important applications in the field of high-resolution detection and other fields within the Terahertz wave band.