To address the issue of decreased signal-to-noise ratio in Doppler signals when using a laser Doppler velocimeter for high-speed carrier velocity measurements, this study analyzes the impact of pre-amplifier circuit output noise on Doppler signal quality. Theoretical analysis and simulation results indicate that the noise gain peak in the pre-amplifier circuit significantly affects the signal-to-noise ratio of Doppler signals, particularly at high frequencies, leading to a reduction in signal-to-noise ratio. Two types of operational amplifiers are selected to design the pre-amplifier circuit, and their respective output noise and signal-to-noise ratio are analyzed. Experimental validation of the simulation results demonstrates that selecting appropriate electronic component parameters can mitigate the effect of the noise gain peak on the signal-to-noise ratio of Doppler signals. This provides theoretical support for optimizing the pre-amplification circuit design of laser Doppler velocimeters, enhancing their suitability for high-speed carrier velocity measurements.

With the widespread deployment of high-performance sensing systems in applications such as remote sensing monitoring, intelligent surveillance, and urban management, increasingly stringent requirements have been placed on imaging systems in terms of spatial coverage and image detail resolution. However, traditional optical imaging systems are fundamentally limited by the optical system's space-bandwidth product, which defines the trade-off between field of view and resolution. To address this limitation, wide-area high-resolution imaging systems have become a major research focus in modern optical imaging research. This paper focuses on the inherent trade-off between field of view and resolution in conventional systems and presents a systematic review of four representative imaging architectures: single-device scanning systems, multi-chip mosaic systems, multi-camera array systems, and multi-scale imaging systems. Each architecture is examined in terms of imaging principles, system configuration, technical challenges, and application suitability, along with a comparative evaluation of its respective strengths and limitations. Furthermore, by grounding the discussion in the theories of space-bandwidth product and lens scaling laws, the paper reveals the physical constraints of traditional systems and explores the future potential of multi-camera architectures in areas such as multidimensional imaging, high-speed video, large dynamic range, and multimodal sensing. These insights provide theoretical guidance and strategic direction for the development of next-generation intelligent imaging systems.

A 1.3 μm high-speed, double-junction cascaded quantum-dot (QD) active-region vertical-cavity surface-emitting laser (VCSEL) is designed using PICS 3D simulation software. The impact of the tunnel-junction cascaded QD active region on the high-speed performance of the VCSEL is investigated. The tunnel-junction cascade structure effectively enhances both the output power and the small-signal modulation bandwidth of the QD VCSEL. Under continuous-wave conditions, a double-junction cascaded VCSEL not only reduces the threshold carrier density but also improves the quantum-well differential gain compared with a single-junction QD VCSEL. The results show that doubling the number of active regions increases the modulation bandwidth, decreases the threshold current, and exponentially enhances the output power and slope efficiency. For a double-junction cascaded QD VCSEL with a 12 μm oxide aperture at a current of 10 mA, the small-signal modulation bandwidths at 25 °C and 85 °C are 28.0 GHz and 17.8 GHz, respectively. This represents improvements of 16.67 % and 22.76% over single-junction QD VCSEL. The output power of the double-junction cascaded QD VCSEL reaches 17.3 mW at room temperature with an injection current of 10 mA. Further reduction of the number of logarithmic DBRs on top of the double-junction cascaded QD VCSEL increases the small-signal modulation bandwidths to 29.6 GHz and 18.0 GHz at 25 ℃ and 85 ℃, respectively. The designed double-junction cascaded 1.3 μm QD VCSEL provides data and theoretical support for epitaxial-material preparation.

We propose a phase difference measurement method based on digital holographic microscopy. The three-dimensional topography characterization of highly transparent phase-type samples is achieved through digital holographic reconstruction. The environmental refractive index is calculated in combination with the phase difference, and the solution mass concentration is inverted based on the refractive index?mass concentration model. Under ideal conditions, this method achieves a refractive index measurement resolution of 10-6 level and has the capability for non-contact and real-time dynamic measurement. In addition, the phase difference method features a simple device and low cost, and has unique advantages in engineering applications. Through comparative experiments, it is verified that the mass concentration measurement results of the phase difference method and the fluorescence spectrophotometer have consistent trends, and the former has a higher signal-to-noise ratio. This method is applied to the study of the adsorption mechanism of microplastics on polycyclic aromatic hydrocarbons. Focusing on the adsorption processes of polypropylene (PP), polyethylene (PE), and polystyrene (PS) in the typical polycyclic aromatic hydrocarbon naphthalene solution, the morphologies of the three microplastic particles and the mass concentrations of the naphthalene solution that changed with adsorption time are quantitatively measured. The adsorption effect is studied based on the parameters of the adsorption dynamic equation. The experimental results show that there is a significant correlation between microplastic particles with different three-dimensional morphologies and adsorption performance, confirming the application value of the proposed method in the multi-dimensional characterization of complex liquid phase systems.

This study proposes a simple and effective method for generating digital speckle patterns. Speckle coordinates are generated based on pixel occupancy, which in turn produces densely distributed Gaussian speckles. A systematic discussion of speckle parameters is provided, and the analysis indicates that the optimal expected minimum speckle distance is 5 pixel, while the optimal speckle radius is 2 pixel. A comparison is made between four speckle patterns generated by different methods. Numerical simulations show that the proposed method helps reduce systematic and random errors and is better suited for smaller subsets. The applicability of the proposed method in different scenarios is verified through rigid-body translation experiments and specular surface shape measurement experiments.

An ultraviolet metamaterial absorber is designed in this paper, consisting of a titanium nitride (TiN) substrate, a silicon dioxide (SiO2) dielectric layer, and a TiN patterned layer. The absorption characteristics of the absorber are analyzed using the finite element method (FEM), and a dataset is established. A deep learning model based on a tandem neural network is employed for the inverse optimization design of the absorber, significantly accelerating the design process. It is demonstrated that with the optimized structural parameters, an absorptivity greater than 94.3% is achieved in the 200?400 nm range under normal incidence, with absorptivity of 97.0% in the 265?375 nm range. Under a 50° angle of incidence, an average absorptivity of 82.6% is obtained for transverse magnetic (TM) wave incidence, while an average absorptivity of 83.0% is observed for transverse electric (TE) wave incidence. The absorption mechanism of the absorber is attributed to cavity resonance effects. When compared to absorbers reported in existing literature, the ultraviolet metamaterial absorber proposed in this study is not only simpler in structure and easier to fabricate but also exhibits higher absorptivity in the ultraviolet band. Additionally, it is characterized by stability at large incident angles and polarization independence.

To fill the gap in ground-based solar radiation observations in the existing meteorological business station network in China, we conducted two field experiments in Ewenki Autonomous Banner, Hulunbuir, Inner Mongolia in 2019 and 2022, using a domestic self-calibrating hyperspectral radiometer system. The results show that the monthly missing data rate of the system is less than 1%, and the mean time between failures reaches 96.5% of the effective working time, demonstrating its good stability in harsh outdoor environments. Compared with the corresponding products of broadband radiometers, the linear fitting coefficients of ultraviolet radiation, photosynthetically active radiation, total radiation, and direct radiation are 0.95, 0.97, 0.75, and 0.80, respectively. The linear fitting coefficient of hyperspectral direct irradiance of the proposed hyperspectral radiometer system is 97% compared with the products of the Japanese EKO hyperspectral radiometer, and the deviation of hyperspectral reflectance from the reference reflectance is less than 0.5%. These results indicate that the domestic hyperspectral radiometer system operates stably, and its data product accuracy is comparable to that of international advanced solar hyperspectral observation products. It can provide strong support for improving China's ground-based solar radiation observation network and validating the products of meteorological satellite optical payloads, thereby significantly enhancing regional meteorological detection capabilities.