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

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

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

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

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

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

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

To address the interference and dazzling threats posed by high-power lasers to the imaging performance photoelectric of detectors, this paper proposes and validates a dynamic laser interference suppression method based on regional flipping of digital micromirror device (DMD). This method employs a secondary imaging optical path, placing the DMD at the primary image plane. Through real-time identification and flipping of micromirrors corresponding to the laser interference region, high-power interference energy is deflected out of the main optical path, thereby protecting the detector while retaining effective image information of most of the field of view. First, we verified the feasibility of this scheme through optical simulations, and subsequently built an experimental platform for systematic testing. Furthermore, this study quantitavily analyzes the influence of the mask radius, which controls the flipping of the DMD, on the suppression effect. It verifies that the optimal suppression effect is achieved when the flipped region is larger than the interference spot. Experimental results demonstrate that DMD regional flipping nethod can effectively suppress laser interference with different laser powers and incident angles. Compared with the scenario without suppression, the interference power received by the detector is significantly reduced: when the laser is incident off-axis, the laser interference resistance threshold is increased by more than 28.5 dB; when the laser interference is incident parallel to the optical axis, the laser interference resistance threshold can be enhanced by over 30 dB. In comparison with traditional image processing methods, this method can retain as much image information as possible under scenarios of strong light interference. This technology provides an efficient and concise solution for photoelectric systems to maintain stable imaging in strong light interference environments.

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. 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, meeting design specifications for optical image quality. 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.

In order to investigate the imaging function of metasurface based on geometric phase theory, this article deduces the imaging formulation of arbitrary curve with the theory of geometric phase imaging on metalens, and its feasibility and correctness is verified by scalar diffraction theory. The imaging formulation is further applied in polarization detection of the incident beam. The results show that phase manipulation of metasurface based on geometric phase can achieve the functions of arbitrary curve imaging and polarization detection of the incident beam, which is of great significance in the field of holographic imaging, optical communication and quantum science.

Time-domain diffuse optical imaging (TD-DOI) is an advanced tissue optical imaging technique. Utilizing a time-correlated single-photon counting (TCSPC) system, it enables the quantitative reconstruction of tissue absorption and scattering coefficients. This facilitates the precise assessment of key physiological parameters, such as tissue oxygen metabolism and blood perfusion. However, due to the inherent hardware complexity and high cost of TCSPC systems, it is currently challenging to meet the requirements for scaled, multichannel, dynamic in vivo monitoring in clinical settings. This paper develops a dual-channel differential hybrid trigger and reference signal strategy. By integrating a differential time-to-digital converter (TDC) device with photon counting technology, we construct a stable and reliable time point spread function (TPSF) measurement system. This system achieves sub-nanosecond precision in calibrating the time delay between the laser synchronization signal and emitted photon signals. Experimental validation demonstrates a system temporal resolution of 55 ps. At a photon count rate of 2.3 × 10⁴ photons per second, the TPSF fluctuation coefficient remains below 1.35% (with an integration time of 1 s). Optical parameter inversion tests on tissue-simulating phantoms demonstrate average inversion errors of 5.39% for the absorption coefficient and 4.34% for the reduced scattering coefficient. This technological approach significantly advances the feasibility of multichannel parallel detection for TD-DOI. It is particularly suitable for biomedical applications demanding dynamic monitoring, such as cerebral cortical hemoglobin oxygen saturation, and lays the technical groundwork for developing next-generation wearable optical brain functional imaging devices.

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, typical damage effect data of CMOS components caused by 532-nm and 1064-nm nanosecond pulsed lasers are obtained through a series of experiments. 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.

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, we 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 experiment results 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 1×10⁰ to 1×10⁻⁵, the PST in the field of view was reduced from 1×10² to 1×10⁻¹, and the stray light contrast with the target signal was controlled below 1×10⁻⁴. 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.

Addressing the urgent demand for 1018 nm single-frequency seed sources in Rydberg microwave measurements, we have developed a wide tuning 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, with the temperature fluctuation of the DBR resonance cavity was only ±0.0005 °C within 2 hours at a controlled temperature of 25 °C. Through experimental testing, the laser maintains single-longitudinal-mode output at 25°C, with a linewidth of 810 Hz, a temperature tuning range exceeding 0.9 nm, and a PZT-based fast-tuning range of up to 10 GHz, without any mode-hopping during 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 remains below −140 dB/Hz for frequencies greater than 1.5 MHz. This result shows that the laser achieves both low-noise output and wide tuning.

Catadioptric space cameras are widely used in space exploration. However, temperature variations can degrade their imaging performance. To address this issue, we present 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 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, the curved image plane imaging system is theoretically analyzed according to Gaussian optics theory. 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-field 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 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 at 223 lp/mm. This work lays a foundation for the application of curved sensors and offers a technical reference for the design of wide-field compact lenses.

Laser absorption spectroscopy (LAS) has been widely applied in atmospheric monitoring, industrial production, medical diagnostics, and other fields due to its high sensitivity, rapid response, and real-time online detection capabilities. However, spectral overlap interference remains a major challenge in LAS. In this study, a multispectral line spectral analysis approach based on cavity ring-down spectroscopy (CRDS) is proposed. A CRDS gas detection system was developed using a custom-designed cage-type Fabry-Pérot cavity, and seven acetylene (C₂H₂) absorption lines in the range of 6452 cm⁻¹ to 6453 cm⁻¹ were selected for investigation. Experimental results demonstrate that the system is capable of accurately measuring and filling the multi-line absorption spectra of C₂H₂ with a minimum detection limit of 3.517×10⁻⁸ cm⁻¹, corresponding to a minimum detection volume fraction of 4.37 ×10⁻⁶. Additionally, the intracavity pressure was precisely measured using a calibrated high-precision vacuum gauge. By analyzing the pressure-broadening effects observed in the absorption spectra, we calculated the pressure-broadening coefficients for three absorption lines, achieving a relative deviation below 0.04. This study provides a novel method for multispectral line spectral analysis in LAS, improving measurement accuracy and broadening its applicability.

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 for an optical component 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=4.661λ and RMS=0.857λ converged to PV=2.465λ and RMS=0.622λ after processing. The total execution time was 3.943 h, with the maximum execution time for a single processing unit being 2.041 h, 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.

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 phase acquisition accuracy, but also offers significant advantages in terms of required data volume and operational convenience, demonstrating broad application potential.

The morphological description of wear particles in lubricating oil is crucial for wear state monitoring and fault diagnosis in aero-engines. Accurately and comprehensively acquiring three-dimensional (3D) morphological data of these particles has became a key focus in wear debris analysis. Herein, we develop a novel multi-view polarization-sensitive optical coherence tomography (PS-OCT) method to achieve accurate 3D morphology detection and reconstruction of aero-engine lubricant wear particles, effectively resolving occlusion-induced information loss while enabling material-specific characterization. The particle morphology is captured by multi-view imaging, followed by filtering, sharpening, and contour recognition. The method integrates advanced registration algorithms with Poisson reconstruction to generate high-precision 3D models. This approach not only provides accurate 3D morphological reconstruction but also mitigates information loss caused by particle occlusion, ensuring model completeness. Furthermore, by collecting polarization characteristics of typical metals and their oxides in aero-engine lubricants, this work comprehensively characterizes and comparatively analyzes particle polarization properties using Stokes vectors, polarization uniformity, and cumulative phase retardation, and obtains a three-dimensional model containing polarization information. Ultimately, the proposed method enables multidimensional information acquisition for the reliable identification of abrasive particle types.

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 significant advantages for its applications around the 1 μm wavelength band.

A plasmonics waveguide structure that consist of a non-through metal–insulator–metal (MIM) waveguide coupled with a D-shaped cavity was designed. And the transmission properties, magnetic field distribution, and refractive index sensing functionality were simulated using the finite element method (FEM). A multi-Fano resonance phenomenon was clearly observable in the transmission spectra. The Fano resonances observed in the proposed structure arise from the interaction between the discrete states of the D-shaped resonant cavity and the continuum state of the non-through MIM waveguide. The influence of structural parameters on Fano resonance modulation was investigated through systematic parameter adjustments. Additionally, the refractive index sensing properties, based on the Fano resonance, were investigated by varying the refractive index of the MIM waveguide's insulator layer. A maximum sensitivity and FOM of 1155 RIU/nm and 40 were achieved, respectively. This research opens up new possibilities for designing and exploring high-sensitivity photonic devices, micro-sensors, and innovative on-chip sensing architectures for future applications.

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. By 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), and 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.

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 fabrication method of femtosecond laser element-doping microstructuring to achieve inorganic superhydrophobic aluminum alloys surfaces through simultaneously modifying the surface profile and compositions of aluminum alloys. 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.

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 energy source in the quantum regime, a quantum battery inevitably experiences a process where the extracted work decreases 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.

In order to minimize misalignment angle errors in laser-guided seekers, it is necessary to optimize the quality of energy signals through advanced optical design techniques. The initial design parameters were obtained through the integration of aberration theory and state-of-the-art optical design software. The optical system is progressively designed through iterative processes from the perspectives of the optical structural forms and optimization of aberration balancing. 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 6 mrad. 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 achieve the recognition and 3D reconstruction of space target components in complex, low-texture environments for space situational awareness tasks, this paper proposes an end-to-end intelligent perception framework for space targets based on deep learning. This framework enables intelligent recognition and high-precision 3D reconstruction of key space target components. The current space target sensing task is facing great challenges, the surface of on-orbit targets are mostly low-texture metal materials, traditional feature matching methods are ineffective, and the geometrical structure of the components is complex and there is occlusion, so it is necessary to take into account the global semantics and local accuracy. First, based on the lightweight YOLOv11s network, an attention mechanism is introduced to focus features, achieving precise localization and recognition of space targets and their key components while ensuring real-time performance. This facilitates the extraction of target regions for accurate 3D reconstruction. Subsequently, a novel 3D reconstruction algorithm named Sat-TransMVSNet, specifically designed for low-texture space targets, is proposed. This algorithm employs a multi-scale feature enhancement network for feature extraction and utilizes a novel cost volume regularization method to strengthen geometric constraints at space target edges. It incorporates a background-suppression and foreground-enhancement module, combined with a dynamic depth sampling strategy, to accurately reconstruct space targets. Finally, the overall framework is tested using a self-built multi-angle space target dataset comprising various types. Experimental results indicate that the component recognition algorithm achieves an mAP50 of 0.95, and the comprehensive 3D reconstruction error is 0.2886 mm. This demonstrates the framework’s capability to meet the requirements for high-precision 3D reconstruction of space targets and intelligent recognition of key components.

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.

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

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

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

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

Off-axis reflective optical systems are widely employed in Earth observation and mapping owing to their advantages of wide field of view (FOV), high image quality, and stable interior orientation elements. However, conventional designs based on the point-by-point (PW) method often suffer from degraded off-axis imaging performance and thermally induced pointing drift. In this study, the third-order aberration coefficients of a three-mirror optical system are analytically derived under the condition that the aperture stop is located at the secondary mirror and that the primary and tertiary mirrors are equally spaced along the optical axis. To further enhance imaging performance, fourth-order aspheric terms are introduced on both the primary and tertiary mirrors, thereby increasing the degrees of freedom for optimization. A comprehensive image-quality evaluation function incorporating quasi-telecentric constraints is constructed, and a hybrid genetic algorithm-sequential quadratic programming (GA-SQP) approach is employed to obtain an optimized initial configuration. The resulting system achieves a focal length of 260 mm, an F-number of 10, and a 7° × 30° FOV, with a modulation transfer function (MTF) above 0.25 at 77 lp/mm, a maximum distortion of 2%, and a maximum chief-ray angle of 2.3°. Microcrystalline glass and titanium alloy are adopted as the mirror substrate and structural materials, respectively. Finite-element thermal analysis is performed under a 6.8 °C temperature gradient, and the optical axis rotation, evaluated using the TRIAD algorithm, is −0.728″ about the X-axis, 1.0816″ about the Y-axis, and 11.045″ about the Z-axis. These results confirm the excellent thermal stability of the proposed design and underscore its potential for reducing in-orbit mapping errors under uncontrolled thermal environments.

Conventional microwave antennas are constrained by the diffraction limit, making it challenging to breakthrough the constraint of wavelength-scale, which hinders their application in high-resolution microwave sensing and detection. To overcome this limitation, this study designs an all-dielectric integrated meta-antenna with super diffraction-limited performance. First, the antenna surface is functionalized using an asymmetric scattering meta-grating array based on the generalized Snell's law, enabling efficient subwavelength beam focusing through precise electromagnetic wavefront manipulation. Then, the geometrical structural of the metagrating is optimized to achieve high-efficiency wavefront control. Finally, the electric field intensity distribution and size of the generated focal spot are analyzed. The simulation results demonstrate that the highest manipulation and diffraction efficiencies reach 98.50% and 72.56%. The achieved focal spot exhibits a subwavelength dimension below 0.73λ with a focal depth of approximately 15.11λ. The designed meta-antenna simultaneously achieves long focal depth and high-efficiency, with its subwavelength focusing capability remarkably enhancing spatial resolution. It provides a novel solution for high-precision sensing and detection in fields such as microwave imaging, non-destructive testing, and biomedical diagnosis, demonstrating substantial potential for practical applications.

With the rapid development of space laser communication technology, the demand for high-speed inter-satellite networking has been growing significantly. However, existing research on inter-satellite laser communication payload is still primarily experimental, featuring complex optical system designs that require lengthy and costly processes for manufacturing, alignment, and testing—posing challenges for low-cost and rapid mass production. To address this issue, a transmissive optical antenna with single-band achromatic design is proposed in this paper, along with a rapid alignment method for measuring the magnification of the optical antenna based on a collimator. By narrowing the chromatic aberration correction range, the length of the optical antenna was reduced by 15.83%, the number of lenses was decreased from six to four, and the manufacturing cost of a single optical antenna was reduced by 33.33%. Simulation results indicate that the alignment tolerance range for magnification is 4.37 to 5.08. After actual alignment, the measured magnification is 4.82, with a beam divergence of 67.53 μrad on the transmission path and a coupling efficiency of 51.42% on the receiving path. The self-calibration spot size is within 12×12 pixels. A comparative experiment is also conducted, and the alignment time of the proposed method is within 10% of that required by the interferometer method. The alignment and test results demonstrate that the proposed method not only enables a lightweight and compact design of the optical antenna, but also significantly reduces the alignment time. Simultaneous focal alignment of signal transmission, acquisition-pointing-tracking, and self-calibration optical paths is also achieved.

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

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

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

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

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

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.

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.

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.

Diffractive waveguides have emerged as a particularly promising solution for augmented reality (AR) near-eye display technologies. These waveguides are characterized by their light weight, wide field of view, and large eyebox. However, most commercially available AR waveguide simulation software has been developed by foreign companies, and there has been little advancement in domestic 3D visualization software for optical waveguide design and simulation. The present study is, to the best of our knowledge, the first to develop 3D visualization module for optical waveguide design and simulation based on ray-field tracing. Using this module, a two-dimensional exit-pupil-expansion diffractive waveguide has been designed, and a systematic design workflow is demonstrated. The workflow integrates k-domain analysis, automated layout generation of grating regions within the optical waveguide, waveguide optimization, and ray-field tracing simulations, thereby establishing a cohesive methodology for device development. The module extends beyond single-waveguide simulations to system-level analyses of near-eye displays, including micro-displays, micro-projectors, and human eye models. By bridging the microscopic and macroscopic scales, it enables holistic performance evaluation of AR optical systems, highlighting their capabilities and technical advantages. This module provides a robust and efficient platform for domestic optical engineers to advance the design and simulation of optical waveguides, thereby accelerating the industrialization and technological advancement of AR optics in China.

Atmospheric coherence length is a critical indicator of the impact of atmospheric turbulence on free-space optical communication links. This paper proposes a novel strategy for measuring atmospheric coherence length by utilizing extended targets as the information source. Specifically, the method integrates the wavefront structure function approach with the extended target offset algorithm to directly estimate the atmospheric coherence length. Traditional methods, such as the Differential Image Motion Monitor (DIMM), typically rely on guide star targets, which are difficult to set appropriately in horizontal communication links, thereby limiting their effectiveness in practical applications. In contrast, employing extended targets as direct detection targets provides a feasible solution for measuring atmospheric coherence length. The paper first reviews the principles and current research status of mainstream algorithms, emphasizing the reliance of existing algorithms on guide star targets and their limitations in horizontal links. Subsequently, we propose a new measurement scheme that combines the improved normalized cross-correlation algorithm with the wavefront structure function method to estimate atmospheric coherence length under extended targets scenarios. In comparison to traditional measurement methods, our approach enables coherence length measurement based on extended targets in horizontal links, thereby significantly reducing system complexity and equipment costs. To validate the effectiveness and measurement accuracy of the proposed method, both simulations and experiments were designed and conducted. The results demonstrate that the coherence length values measured by this method are highly consistent with those obtained using the DIMM method and the wavefront phase variance method, with a measurement accuracy error of approximately 4%. This indicates that the proposed method can effectively assess atmospheric coherence length, thereby providing a valuable reference for enhancing the reliability of free-space laser communication systems.

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 literatures (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 two output 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, respectively, 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, a specific design example of a large beam deviation angle for a Rochon prism composed of heterogeneous crystal materials is provided. 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.