Micro-channel Plate (MCP) with Ion Barrier Film(IBF) is one of the main technical indicators that restrict the performance of the third generations of Low Light Level Image Intensifier(LLLII). IBF with inferior quality can be a direct impact on the performance of the third generations of LLLII or even makes it not work, and it’s very unfavorable in the tube mass production and promotion. In response to this urgent requirement, in order to improve the quality and preparation of the finished product of the Al2O3 on the input side of MCP prepared by magnetron sputtering, the paper carries out the process optimization of magnetron sputtering used for image intensifier. By simulation of Ar ion bombarding Al2O3 target, while under the guidance of the working principles of the magnetron sputtering and thin film growth theory, we change the working pressure、 sputtering power、 argon flow and other process parameters by using magnetron sputtering machine developed in China, to change the coating deposition rate of Al2O3, and to increase the lateral migration of the film-forming process of Al2O3. Finally we prepare a uniform、 continuous and compact Al2O3 Ion Barrier Film. At last the optimal technique is obtained: Sputtering pressure is 2.6×10-1Pa, Ar2 flux is 90sccm, sputtering power is 170W, and the thickness of film is 80Å. We test the performance of MCP with optimized films by using the MCP performance testing devices, contrasting with pre-fabricated thin-film quality, and the results show that the average gain decline is dropped, the dead volt is lower, and the quality of the films prepared by this process is significantly better, yield and view pass rate is as high as 90%, meeting the dual demands of high electronic transmittance and high ion blocking rate of IBF.
Abstract The main challenge in designing broadband achromatic metalenses is to achieve the desired phase distribution at different wavelengths and positions. Finding the exact relationship between phase modulation and the size or shape of individual nanopillars is a critical but time-consuming step. This paper presents a novel joint design framework predictive neural networks and particle swarm optimization-genetic algorithms, which combines predictive neural network (PNN) and particle swarm optimization-genetic algorithm (PSO-GA). The proposed framework aims to accurately predict the phase response of nanopillars using PNN, increase the number of phase data points to establish a one-to-one correspondence between the phase and nanopillar parameters in the design of broadband achromatic metalenses, and optimize the parameters of an individual nanostructure of the metalens using PSO-GA. To validate the efficacy of the proposed method, a broadband achromatic metalens for line polarization light in the range of 260–350 nm is designed. Numerical simulations demonstrate that the designed metalens exhibits achromatic focusing. The method proposed in this paper may find wider application in the design of more complex metasurface devices.
To establish a methode for predicting the integral sensitivity of transmission-mode GaAs photocathodes, the relationship between X-ray relative diffraction intensity and integral sensitivity of GaAlAs/GaAs photocathode material is researched. After thermocompression bonding Si 3 N 4 /GaAlAs/GaAs/GaAlAs/GaAs epitaxial material to glass window in the vacuum condition, and chemically etching the GaAlAs buffer-layer and GaAs substrate, the glass/Si 3 N 4 /GaAlAs/GaAs photocathode module is formed. The X-ray relative diffraction intensity of the photocathode module is tested and calculated respectively, then the photocathode surface was activated in the ultrahigh vacuum chamber using the Cs-O activation technique. Following that, the integral sensitivity of the transmission-mode GaAs photocathode is measured by the spectral response measurement instrument in situ. It is found that the GaAlAs/GaAs photocathode material and photocathode module have similar X-ray relative diffraction shapes. The higher the similar degree of X-ray relative diffraction shape is, the bigger the X-ray relative diffraction intensity of photocathode module is, which results in the better photoemission capability and higher photocathode integral sensitivity. This method can be used as an evaluation criterion for the quality of transmission-mode GaAs photocathode module material.
Abstract The main problem faced by traditional three-dimensional (3D) holographic displays is the time-consuming and poor flexibility of the hologram generation process. To address this issue, this paper proposes a non-iterative 3D computer-generated hologram (SFS-ORAP-PC-3D) method based on single full-support optimized random phase and phase compensation. Combining the full-support optimized random phase (FS-ORAP) method and the 3D layer-based idea to efficiently and non-iteratively generate the phase-only hologram of a 3D object with arbitrary positions and sizes using single FS-ORAP, thus overcoming the limitations of the original ORAP method in target position and size. Meanwhile, using a Fresnel lens for phase compensation allows for free selection of reconstruction planes. Numerical and optical experiments validate the feasibility of our proposed method.
Abstract Label‐free biological cell imaging relies on rapid multimode phase imaging of biological samples in natural settings. To improve image contrast, phase is encoded into intensity information using the differential interference contrast (DIC) and Zernike phase contrast (ZPC) techniques. To enable multimode contrast‐enhanced observation of unstained specimens, this paper proposes an improved multimode phase imaging method based on the transport of intensity equation (TIE), which combines conventional microscopy with computational imaging. The ZPC imaging module based on adaptive aperture adjustment is applied when the quantitative phase results of biological samples have been obtained by solving the TIE. Simultaneously, a rotationally symmetric shear‐based technique is used that can yield isotropic DIC. In this paper, we describe numerical simulation and optical experiments carried out to validate the accuracy and viability of this technology. The calculated Michelson contrast of the ZPC image in the resolution plate experiment increased from 0.196 to 0.394.
In order to precisely predict the sensitivity of Ф18 mm transmission-mode GaAs photocathode, a concept of integral diffraction intensity is proposed based on X-ray diffraction principle after analyzing the predecessors′ limitations of testing the micro-area of such photocathode and GaAs photocathode of image intensifier tube is plane electron source in this paper. The integral diffraction intensity on the entire photocathode surface was obtained by multi-points detection in the effective area of the photocathode with integral method. The crystal quality of entire photocathode surface will be taken with the integral diffraction intensity. According to the principle, X-ray diffraction testing for 4 samples of GaAs photocathode modules was executed with high-resolution four-wafer X-ray Diffractometer whose test spot size is 4 mm×5 mm. The diffraction curves were obtained and the integral diffraction intensity was calculated. Subsequently the 4 photocathode modules was activation processed with Cs-O in ultra-high vacuum system simultaneity the photocurrent of photocathode modules was measured. Comparing the variation of diffraction curve with integral diffraction vs photocathode photocurrent curve, they show that the greater the integral diffraction intensity of is, the more photocurrent is in the photocathode module. The variation relation curve between X-ray integral diffraction intensity and photocurrent in the photocathode was fitted with least square method. The curve, which accords with logarithm curve and whose fitting degree is 0.878, was achieved. Since photocathode sensitivity is direct proportion to photocathode photocurrent. The above results prove that A Practicality Φ18mm photocathode of image intensifier tube is plane electron source, GaAs photocathode sensitivity and other photoelectric performance lies on entire photocathode surface crystal quality, the photocathode module integrality reflected by the integral diffraction intensity plays crucial role of GaAs photocathode sensitivity. So integral sensitivity of Ф18 mm transmission-mode GaAs photocathode can be precisely predicted with X-ray integral diffraction intensity, some feasible ideas for further research of GaAs photocathode was obtained in this paper.
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