Photodetectors Based on Micro-nano Structure Material.

Photodetectors converting optical signals into electrical signals have been widely utilized and have received more and more attention in scientific research and industrial fields including optical interconnection, optical communication, and environmental monitoring. Herein, we summarize the latest development of photodetectors with different micro-nano structures and different materials and the performance indicators of photodetectors. Several photodetectors, such as flexible, ultraviolet two-dimensional (2D) microscale, and dual-band photodetectors, are listed in this minireview. Meanwhile, the current bottleneck and future development prospects of the photodetector are discussed.

Using the spatial light modulator as a binary optical element: application to spatial beam shaping for high-power lasers.

The liquid crystal spatial light modulator (SLM) is an effective active beam-shaping device through adjusting each pixel transmittance to improve the spatial beam quality of the output laser, which can also be used as a binary optical element (BOE) with each pixel transmittance 0 or 1 to realize spatial beam shaping for high-power lasers. We present and demonstrate an efficient shaping method of the SLM used as BOE based on diffraction principle. The method can be used to control the output nearfield actively by compensating the spatial nonuniformity of transmission and amplification in the high-power laser system. Results show the output nearfield beam quality improves significantly after shaping by using this method with the fluence contrast changing from 22% to 11.3% within only two shots in the single-shot operation laser.

Application of two oriented partial differential equation filtering models on speckle fringes with poor quality and their numerically fast algorithms.

In this paper, we are concerned with denoising in experimentally obtained electronic speckle pattern interferometry (ESPI) speckle fringe patterns with poor quality. We extend the application of two existing oriented partial differential equation (PDE) filters, including the second-order single oriented PDE filter and the double oriented PDE filter, to two experimentally obtained ESPI speckle fringe patterns with very poor quality, and compare them with other efficient filtering methods, including the adaptive weighted filter, the improved nonlinear complex diffusion PDE, and the windowed Fourier transform method. All of the five filters have been illustrated to be efficient denoising methods through previous comparative analyses in published papers. The experimental results have demonstrated that the two oriented PDE models are applicable to low-quality ESPI speckle fringe patterns. Then for solving the main shortcoming of the two oriented PDE models, we develop the numerically fast algorithms based on Gauss-Seidel strategy for the two oriented PDE models. The proposed numerical algorithms are capable of accelerating the convergence greatly, and perform significantly better in terms of computational efficiency. Our numerically fast algorithms are extended automatically to some other PDE filtering models.