Junhua Wang

Thermal disturbances in ground-based optical alignment and integration environments induce refractive index fluctuations that significantly degrade wavefront measurement accuracy, particularly in large-aperture optical systems. To address this issue, an engineering-oriented active disturbance strategy combined with multi-measurement averaging is proposed to improve wavefront measurement robustness under non-ideal thermal conditions. By intentionally disrupting stable thermal convection structures, systematic thermally induced wavefront drifts are converted into random fluctuations, which can be effectively suppressed through repeated measurements and averaging in practical alignment procedures. The proposed strategy is evaluated using root mean square and peak-to-valley wavefront error metrics to characterize convergence behavior and measurement stability. Simulation results show that increasing the number of averaged measurements significantly reduces both the mean and variance of wavefront errors, thereby improving alignment accuracy and repeatability. The proposed strategy further exhibits robust performance under severe thermal gradient conditions, highlighting its applicability in practical laboratory and integration environments. Overall, we provide a practical, cost-effective, and easily implementable solution for mitigating thermally induced wavefront errors in ground-based alignment of large-aperture optical systems.

Deep learning–based image reconstruction for visible–near infrared cameras relies heavily on the quality and physical realism of simulated training data. However, most existing simulation dataset generation methods based on actual optical systems neglect the influence of multiwavelength weighting on imaging characteristics. To address this limitation, we propose a simulation data generation method that incorporates multiwavelength weighting variables. Based on the actual optical design, differentiable ray tracing is employed to construct a multiwavelength-weighted training data, and a standard nonlinear activation free network model is trained for image reconstruction. Experiments on real-world images demonstrate that the proposed strategy achieves superior restoration performance, yielding an average 18.02% reduction in the BRISQUE score, corresponding to an ∼8% additional improvement compared with the model trained without multiwavelength weighting. These results indicate that incorporating multiwavelength weighting into simulation data generation is effective and feasible for enhancing image reconstruction performance in real-world environments.

With the rapid development of optoelectronic technology, traditional linear optical devices face prominent performance bottlenecks, and materials with excellent nonlinear optical properties are crucial for device upgrading. As a key binary chalcogenide, Sb2Te3 has advantages of low melting point and favorable nonlinear saturable absorption, showing broad potential in ultrafast lasers. However, the intrinsic optical bandgap of Sb2Te3 is approximately 0.86 eV at the 1550 nm wavelength, making it difficult to exhibit excellent nonlinear optical performance in this core communication band. Herein, Al doping is employed to tailor the optical bandgap of Sb2Te3 thin films, as Al can form covalent bonds with Sb and Te, modulate carrier concentration, and tune the bandgap width. We systematically probed the effects of Al dopant on crystallinity, transmittance, optical bandgap, and nonlinear absorption coefficient of Sb2Te3, while elucidating the underlying mechanisms.The findings demonstrate that Al doping enables efficient modulation of the intrinsic optical properties of Sb2Te3. Specifically, the third-order nonlinear absorption coefficient of Al-doped films is 2.55 times that of undoped at the 1550 nm. This work furnishes theoretical and experimental underpinnings for optimizing the nonlinear optical performance of Sb2Te3 at 1550 nm, while offering valuable insights for the development of high-performance nonlinear optical devices.

A series of Bi₂Se₃ thin films, including undoped and aluminum (Al)-doped samples with varying concentrations, were successfully fabricated at room temperature using magnetron co-sputtering. Comprehensive characterization of the film microstructure, elemental composition, and chemical states was performed with scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The optical constants in the visible to near-infrared range were obtained via spectroscopic ellipsometry, enabling a thorough analysis of their linear optical properties. Furthermore, the third-order nonlinear optical absorption behavior of the films under 800 nm femtosecond laser pulse excitation was investigated in detail using open-aperture Z-scan technique. Results found that even the undoped Bi₂Se₃ thin film itself exhibited a distinct reverse saturable absorption effect, and this nonlinear response was remarkably enhanced by Al doping. This enhancement is primarily attributed to the additional defect states introduced by Al doping and the resultant optical bandgap narrowing, which collectively amplify the nonlinear optical response. Quantitative analysis showed that the third-order nonlinear absorption coefficient of the film with an Al doping concentration of 3.49 wt.% was 2.6 times that of the undoped sample. The observed reverse saturable absorption behavior in Bi₂Se₃ thin films and its pronounced enhancement through Al doping provide crucial experimental evidence and a promising material candidate for extending the application of this material to nonlinear photonic devices such as optical limiters and all-optical switches.

This paper presents LONS-Calib, a novel extrinsic calibration framework for light detection and ranging (LiDAR) and omnidirectional cameras, specifically targeting panoramic annular lenses and fisheye lenses capable of capturing negative space information (z < 0). It also supports cameras with narrower fields of view, such as pinhole cameras. To overcome the impact of the significant distortion inherent in omnidirectional images, the framework optimizes chess-board corner extraction, projecting these corners onto a unit sphere for accurate camera pose estimation. Additionally, automatic detection of chessboard point clouds enhances efficiency in LiDAR pose estimation. The sample selection process is automated using the Variability of Quality (VOQ) score, which accounts for sensor measurement errors and the generalizability of calibration results. These features ensure that users, regardless of their calibration expertise, can easily record diverse poses and achieve high-quality calibration results with LONS-Calib. Extensive evaluations on synthetic and real-world datasets demonstrate remarkable calibration accuracy and efficiency, with typical optimization times under 0.3s on consumer-grade laptops. The calibration results also demonstrate applicability to multi-sensor fusion simultaneous localization and mapping (SLAM). Our framework is available at: https://github.com/wwendy233/LONS-Calib.

Bismuth telluride (Bi₂Te₃) has attracted significant attention due to its broadband ultrafast optical response and strong nonlinearity at high laser fluence in the field of optoelectronic materials. The objective of this work is to study the effect of Al doping on the structure, linear optical properties, and nonlinear optical absorption behavior of Bi₂Te₃ thin films. The amorphous Al-doped Bi₂Te₃ thin films with varying Al doping concentrations were prepared using magnetron co-sputtering. The structure and linear optical properties were characterized using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, spectroscopic ellipsometry, and UV/Vis/NIR spectrophotometry. The third-order nonlinear optical absorption properties of Al: Bi₂Te₃ thin films were investigated using the open-aperture Z-scan system with a 100 fs laser pulse width at a wavelength of 800 nm and a repetition rate of 1 kHz. The results indicate that Al dopant reduces both the refractive index and extinction coefficient and induces a redshift in the optical bandgap. The optical properties of the films can be effectively modulated by varying the Al doping concentration. Compared with undoped Bi₂Te₃ thin films, Al-doped Bi₂Te₃ thin films exhibit larger nonlinear optical absorption coefficients and higher damage thresholds and maintaining high transmittance. These findings provide experimental evidence and a reliable approach for the further optimization and design of ultrafast nonlinear optical devices.

High-precision spherical parts are widely used in measurement machines, MEMS devices and other fields, but there are few effective methods for the full annular area measurement of sphere surface. In this paper, an interferometry-based method for the full annular surface measurement of spherical parts is proposed. By adding an off-axis parabolic mirror, the parallel beam was converted into an annular beam, enabling the measurement of sphere surface near the equator. The method was validated using a Zygo interferometer and approximately one-sixth of the surface was measured in one single measurement. The eccentricity error was minimized by error compensation algorithm and the surface error of paraboloid was calibrated using a master ball. A large range of surface near the equator can be efficiently obtained in one single measurement and verification measurement results indicate its efficiency and reliability.