This paper presents comprehensive theoretical and experimental investigations on the transmission spectral characteristics of an integrated photonic structure consisting of a microring resonator coupled with a Fabry–Perot (FP) cavity. The FP cavity is realized by introducing a grating reflector into the straight waveguide of a single-side-coupled microring. Within this dual-resonator configuration, novel multi-cavity coupled transmission spectra are achieved. A systematic theoretical model is established to analyze the conditions under which these multi-cavity coupled spectral profiles appear, and the structural parameters are subsequently optimized. A grating-type Fabry–Perot–microring coupled resonator device was successfully fabricated on a silicon-on-insulator (SOI) platform. For the first time, multi-cavity coupled transmission spectra consistent with theoretical predictions were experimentally observed, including nested electromagnetically induced transparency (EIT)-like and double Fano resonance line shapes. Experimental measurements indicate that, under a waveguide loss of 3.43 dB/cm, the EIT central peak exhibits a quality factor of 1.40×10⁴, while the slope of the double Fano resonance reaches 37.70 dB/nm. These results provide new insight into the underlying mechanisms of integrated photonic coupled resonator systems and demonstrate a viable approach toward highly integrated, high-performance photonic device platforms. The proposed structure shows strong potential for applications in high-sensitivity optical sensing, narrowband filtering, and high-speed modulation.

To An all-silica fiber-optic Fabry-Perot (F-P) high-temperature vibration sensor is proposed to address sensor failure and signal distortion in extreme environments. A collimated coupling structure based on a silica ball lens enables integrated, non-contact signal transmission between the fiber and the sensitive structure. The sensitive units are batch-fabricated using MEMS and thermal pressure bonding technologies. By combining three-wavelength dynamic demodulation with spectral cross-correlation, precise vibration signal extraction and temperature compensation are achieved, effectively eliminating thermal cross-sensitivity. Experimental results indicate that as the temperature increases from room temperature (23 °C) to 800 °C, the sensitivity of the sensor decreases from 1.051 nm/g to 0.8915 nm/g. After temperature compensation, the maximum residual sum of squares (RSS) of the sensor is 0.168, and the full-scale nonlinearity error does not exceed 1.033%. In dynamic response tests, the characteristic frequency of the sensor is considerably higher than 6000 Hz. The sensor exhibits high flatness within the frequency response range of 100−2000 Hz, and its sensitivity gradually increases between 2000 Hz and 6000 Hz, with a maximum increment of only 0.177 nm/g. Featuring high consistency, adhesive-free integration, and electromagnetic immunity, this sensor provides a robust solution for vibration measurement in high-temperature environments.

To address the issues of structural complexity and high cost in high-performance optical systems, this study proposes an optical system simplification and aberration correction method oriented towards computational correction. On the optical design side, a simplification design criterion based on aberration correctability analysis is constructed: priority is given to suppressing aberrations that are difficult for neural networks to compensate, while retaining portions amenable to computational correction, thereby simplifying the optical system structure while ensuring imaging quality. On the computational processing side, a multi-module progressive collaborative correction network is designed, comprising four modules: distortion correction, chromatic aberration compensation, monochromatic aberration correction based on physically-constrained Point Spread Function, and frequency-domain enhancement. This network is driven by a Temporal Stage Controller (TSC), which utilizes its dynamic weight scheduling mechanism for progressive stage-wise processing, effectively suppressing the mutual interference between different aberration types. Experimental results demonstrate that images from a simplified dual-lens system corrected by this network achieve a Peak Signal-to-Noise Ratio (PSNR) of 31.47 dB and Structural Similarity (SSIM) of 0.95, with imaging quality comparable to conventional six-lens double-Gauss systems, while significantly reducing optical system complexity. Ablation studies validate the effectiveness of the TSC and multi-module correction architecture. This research provides a novel technical pathway for achieving high-quality imaging with simplified optical systems.

To address the challenge of achieving high-precision registration between visible light (RGB) and photoluminescence (PL) images in Micro LED defect inspection, which arises from substantial modality differences, this study introduces a robust multimodal image registration approach capable of attaining sub-pixel accuracy, aiming to establish a direct mapping between the physical structure and electrical characteristics of the chips. We propose a registration method that integrates structural feature constraints with bidirectional residual optimization. First, leveraging the geometric regularity of Micro LED arrays, a tailored feature detection strategy is employed: electrode centers in RGB images are accurately extracted via ellipse fitting and Density-Based Spatial Clustering of Applications with Noise (DBSCAN), while chip centers in PL images are localized using an enhanced watershed algorithm with sub-pixel refinement. Second, during the registration optimization stage, a bidirectional residual constraint framework is constructed, incorporating a confidence weighting mechanism derived from residual distribution analysis. The optimal affine transformation parameters are then estimated using an iterative reweighted least squares method. Experimental results demonstrate that the proposed method achieves sub-pixel-level accuracy, with a mean absolute error (MAE) of 0.823 pixels, representing a 94.2% reduction compared to baseline methods. The root mean square error (RMSE) is 0.996 pixels, the maximum error remains below 2.839 pixels, and the inlier rate attains 75.0%. Each registration process takes only 0.036 seconds on average, achieving an order-of-magnitude improvement in computational efficiency over traditional mutual information (MI) methods. By effectively mitigating feature mismatch and outlier interference in multimodal images, the proposed method outperforms conventional approaches in terms of registration accuracy, robustness, and efficiency, thereby providing a reliable technical foundation for precise defect detection and multimodal analysis of Micro LED chips.

This study investigates the performance degradation and underlying damage mechanisms of silicon PIN photodiodes under xenon lamp irradiation. To this end, detectivity is defined and operationalized. A 50 kW xenon lamp irradiation test platform was developed, with the S5106-type silicon PIN photodiodes selected as the representative test device. Real-time monitoring of output photocurrent and surface temperature enabled systematic analysis of the factors governing detectivity degradation, as well as characterization of the damage threshold. A damage threshold model for silicon PIN photodiodes was developed based on the one-dimensional heat diffusion equation. Model accuracy was validated against the experimentally measured threshold data. Silicon PIN photodiode damage was categorized into two regimes—soft damage and hard damage—based on the recoverability of detectivity. Under soft damage conditions, the detectivity of the device exhibited a nonlinear negative correlation with both irradiation time and surface temperature. The hard damage irradiance thresholds followed an inverse-square-root dependence on irradiation time, a trend fully consistent with the damage threshold model. Hard damage was observed at a minimum irradiance of approximately 6.6 W/cm², corresponding to an irradiation time of about 382 s. Under this threshold condition, the surface temperature ranged within 385.77±4.16°C. Theoretical analysis indicated that soft damage primarily arose from thermally induced degradation of carrier mobility and increased leakage current. Conversely, hard damage resulted from melting and cracking of the silicone rubber optical window, as well as thermally induced functional failure of the PN junction. The findings provide a quantitative basis for performance evaluation and protection design of silicon PIN photodiodes employed in broad-spectrum high-intensity optical detection scenarios.

The mirror is one of the great significance components of the space camera, and the aluminum alloy mirror is becoming one of the development directions of space camera mirrors with its excellent processability. Objective: To reduce the difficulty of installing and adjusting space cameras, an monolithic aluminum alloy mirror structure design was carried out. Method: First, based on the concept of integrating multiple functions such as mirror surface, flexible support, installation reference and so on, the structure design of an monolithic mirror was carried out. Besides, while designing the structure, co-reference process design was conducted simultaneously. This design was informed by establishing an error transmission model and a corresponding precision allocation scheme. Finally, simulation analysis and processing were carried out on the designed mirror. Result: The results show that the surface accuracy variation of the monolithic mirror was less than RMS 0.01λ@632.8 nm under typical working conditions, and the precision of the processed mirror could reached up to RMS 0.016λ@ 632.8 nm, and the deviation between the mechanical and optical references was better than 2". Conclusion: The monolithic aluminum alloy mirrors designed in this study can satisfy the space mirror requirements of stability, high precision and excellent consistency.

During downward laser transmission across the air–sea domain, beam propagation is influenced by a range of complex, multi-source and multi-scale perturbations, including atmospheric turbulence, fluctuations at the air–sea interface, and oceanic turbulence. This study investigates the evolution of beam spatial coherence and introduces an analytical approach based on a composite perturbation model. The composite model integrates Kolmogorov turbulence theory, the Pierson–Moskowitz (P–M) sea-surface wave spectrum, and the slant-path oceanic refractive-index power spectrum. By employing the Rytov approximation, analytical expressions for the mutual coherence function and wave structure function are derived, with particular focus on the wave structure function of a Gaussian beam propagating through slant-path oceanic turbulence. Each component of the model has been individually validated. Experimental results demonstrate that variations in turbulence intensity, propagation distance, and environmental parameters significantly affect beam spatial coherence, thereby exerting a substantial impact on the performance of cross-domain optical communication systems. Compared to single-turbulence approximation models, the proposed composite perturbation model effectively reduces the spatial coherence bias by approximately 20%-30%, revealing the influence mechanisms of multi-source perturbations on coherence evolution. This model provides an effective theoretical foundation for the performance evaluation and optimization of air–sea optical communication links and enhances the stability and reliability of optical communication systems under realistic conditions.

Addressing the critical challenge of thermal radiation noise suppression in infrared systems for long-range dim target detection, we present 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.

In order to achieve comprehensive, highly efficient, and multi-objective precise optimization of fiber structural parameters and further enhance the transmission capacity of optical communication systems, a homogeneous weakly coupled seven-core fiber based on trench-assisted structures is designed. Particle Swarm Optimization (PSO) is introduced to replace traditional empirical designs or local scanning methods. First, a multi-objective fitness function incorporating constraints such as dispersion, cutoff wavelength, effective mode field area, and coating loss is established. Then, the algorithm performs a global search to precisely determine the optimal structural parameters under standard dimensional constraints. Simulation results demonstrate that with a fiber core pitch of 45 μm, the optimized fiber achieves an ultra-low inter-core crosstalk of below −90 dB/km at a wavelength of 1550 nm. This design scheme not only effectively resolves the conflict between crosstalk suppression and spatial utilization in multi-core fibers but also proves the efficiency and reliability of the PSO algorithm in complex fiber structural design, providing an important theoretical basis and technical support for the research and manufacturing of ultra-large-capacity optical communication systems.

Objective: To retrieve the pulse information from the dispersion scanning (d-scan) trace, a differential evolution (DE) algorithm is used. Methods: A partially coherent pulse train is generated and then test by traditional DE algorithm and its improved version. Results: The errors retrieved using the traditional and improved DE algorithms are 7% and 1%, respectively. Conclusion: The improved algorithm can more accurately retrieve the d-scan trace of partially coherent pulse train.

Due to the nonlinear effects produced by the actual defocusing projection system, which affect the accuracy of phase measurement, the phase error of binary fringe defocusing projection was studied. Based on the analysis of the current study status in the field, an expression for the intensity distribution of deformed fringe pattern signal in nonlinear systems is given, and the reasons for both high-order spectra components occurrence and their mixing with the fundamental frequency components, resulting in spectra overlapping, are analyzed. The method of defocusing the projector was employed to remove the higher-order harmonic components in the spectra domain and filter out one of the fundamental frequency components. An inverse Fourier transform was then performed on the spectra to obtain the expression of fringe intensity in the spatial domain. The continuous phase containing continuous signals was obtained using the phase-shift algorithm and phase unwrapping, and the expression for phase error after unwrapping in actual measurement systems was derived. The correct analysis of the basic principles has been verified through simulation and experiments. The simulation results indicate that the errors value obtained by the method mentioned in this paper are 34.51% for the binary fringe defocusing method, 44.83% for method of reference [1], and 67.83% for method of reference [10], respectively. The experiment results indicate that the phase recovered by using our method has good effects, and the corresponding phase error is relatively small.

To achieve simultaneous lightweight design and high-energy output under special environmental conditions, a compact, water-cooling-free high-energy pulsed laser system based on high-temperature laser diode array (LDAs) side-pumped zigzag Nd:YAG crystals is demonstrated for operation in demanding environments. The zigzag beam propagation increases the effective gain length, while symmetric LDAs pumping of two Nd:YAG crystals improves gain uniformity. Thermal isolation between the crystals and LDAs is implemented, with independent temperature control achieved using thermoelectric coolers (TEC) for the Nd:YAG crystals and forced air cooling for the LDAs. A potassium dideuterium phosphate (DKDP) crystal is employed for electro-optic Q-switching. At a repetition rate of 100 Hz without water cooling, a maximum pulse energy of 129.2 mJ with a pulse duration of 9.0 ns is obtained, corresponding to an optical-to-optical efficiency of 9.6% and a slope efficiency of 13.1%, with energy stability better than 2.26%. An output energy of 87.6 mJ is achieved at 150 Hz. This system provides a compact and environmentally robust light source for laser ranging and illumination applications.

This paper presents a continuously fine-tunable terahertz radiation source based on L-band laser difference frequency generation, with a frequency tuning range of 0.1 to 2.7 THz and a tuning accuracy of 1 GHz. A fully polarization-maintaining fiber link, including polarization-maintaining isolators, polarization-maintaining couplers, and polarization-maintaining erbium-doped fiber amplifiers, was designed to keep the polarization states of the two beams consistent. By using the difference frequency of L-band dual lasers to excite the InGaAs high-performance photoconductive antenna, continuous terahertz radiation ranging from 0.1 to 2.7 THz was generated within the wavelength range of 1568.8 to 1589.6 nm. The power and frequency of the terahertz waves were respectively tested using a Golay cell detector and a terahertz scanning Fabry-Perot interferometer. The results show that the power instability of the terahertz wave within 25 minutes is within 4%, and the frequency measurement results at 0.5 THz and 1 THz are highly consistent with the frequency interval of the L-band dual lasers. Additionally, within the range of 0.9 to 1 THz, a high-precision tuning of 1 GHz was achieved, corresponding to a wavelength interval of 0.008 nm. This continuously fine-tunable terahertz radiation source has high application potential in high-precision spectral detection and other fields.

Chiral metasurfaces play critical role in physics, materials science, pharmacognosy, and communications. To achieve high-performance chiral responses, such as high circular dichroism (CD) and high-quality factors (Q-factors), BIC-based metasurfaces have been extensively studied as a promising platform. However, most realized BIC metasurfaces rely on metallic constituents whose high electromagnetic losses and absence of dynamic chirality tuning together impose a severe limit on their practical potential. This paper presents an all-dielectric chiral BIC metasurface. By illumination symmetry breaking, the metasurface exhibits a CD value of 0.93. Additionally, dynamic tuning of CD is enabled by external optical pumping. This scheme provides a new avenue for dynamically manipulating the chiral metasurface, which can be used to achieve more complex dynamic chiral characterization and applications.

To address the challenge of temperature rise control during the coating process for thermally sensitive substrates (e.g., epoxy adhesive-bonded structural components), this paper proposes a low-temperature electron beam evaporation coating process. Through a dynamic thermal management strategy featuring segmented deposition-cooling cycles, the performance of this process in terms of the core properties (i.e., stress, adhesion, and optical performance) of metallic reflective films-with silver films as the research subject-was systematically investigated, and the deposition process was optimized by integrating the thermal failure threshold of the epoxy adhesive. Experimental results demonstrate that under strictly controlled substrate temperature conditions, this process not only significantly reduces the residual stress of the reflective film, but also ensures that the interfacial adhesion meets the strictest Class 03 severity level specified in the national standard (GB/T 26332.4-2015/ISO 9211-4:2012), the average reflectivity in the visible wavelength range is comparable to that of the traditional continuous coating process (>99%@450−900 nm), and the substrate temperature rise remains consistently below the critical threshold of the epoxy adhesive. Through the synergistic effect of Ion-Assisted Deposition (IAD) and dielectric encapsulation, the oxidation resistance and environmental durability of the silver film are significantly improved, satisfying the long-term service requirements of aerospace optical devices under extreme multi-physics field coupled environments. Further theoretical analysis reveals that the thermal relaxation mechanisms and structural regulation principles of this process exhibit cross-scenario applicability, providing an innovative solution for high-performance coating of low-temperature-sensitive substrates that balances aerospace reliability and industrial universality.

To enhance the imaging performance of arthroscopes in clinical surgery and broaden their potential for clinical applications, a wide-spectrum arthroscopic optical system featuring a large field of view, high resolution, and parfocal imaging capability in both visible and near-infrared bands was designed. The objective lens use a high optical power negative lens to compress the chief-ray angle and reduce the optical path difference between off-axis and on-axis rays. Through conjugate aperture imaging, an equivalent virtual stop is formed inside the turning prism, which allows the system to maintain both high transmission efficiency and high image quality under a limited aperture. The relay lens adopts a near-symmetric structure, and by distributing optical power and Abbe numbers appropriately, it effectively suppresses the accumulation of axial chromatic aberration across the broad spectral range, thereby achieving parfocal imaging. Tolerance analysis shows that the system has good manufacturability and assembly feasibility. Experimental results verify that the designed wide-spectrum arthroscope achieves parfocal imaging in the visible and near-infrared bands with a 95° field of view, and angular resolutions of 4.34 C/(°) and 2.74 C/(°), respectively. The optical system provides a feasible solution for achieving low-cost, high-performance fluorescence arthroscopy and has significant application value.

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

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

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

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

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

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.