Spectral transmittance and module structure fitting for transmission-mode GaAs photocathodes  

作　　者：赵静 常本康 熊雅娟 张益军 

机构地区：[1]Institute of Electronic Engineering and Optoelectronic Technology,Nanjing University of Science and Technology

出　　处：《Chinese Physics B》2011年第4期496-502,共7页中国物理B（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 60678043);the Research and Innovation Plan for Graduate Students of Jiangsu Higher Education Institutions of China (Grant No. CX09B-096Z)

摘　　要：A transmission-mode GaAs photocathode includes four layers of glass, Si3N4, Gal-xAlxAs and GaAs. A gradientdoping photocathode sample was obtained by molecular beam epitaxy and its transmittance was measured by spectrophotometer from 600 nm to 1100 nm. The theoretical transmittance is derived and simulated based on the matrix formula for thin film optics. The simulation results indicate the influence of the transition layers and the three thin-film layers except glass on the transmittance spectra. In addition, a fitting coefficient needed for error modification enters into the fitted formula. The fitting results show that the relative error in the full spectrum reduces from 19.51% to 4.35% after the formula is modified. The coefficient and the thicknesses are gained corresponding to the minimum relative error, meanwhile each layer and total thin-film thickness deviation in the module can be controlled within 73. The presence of glass layer roughness, layer interface effects and surface oxides is interpreted on the modification.A transmission-mode GaAs photocathode includes four layers of glass, Si3N4, Gal-xAlxAs and GaAs. A gradientdoping photocathode sample was obtained by molecular beam epitaxy and its transmittance was measured by spectrophotometer from 600 nm to 1100 nm. The theoretical transmittance is derived and simulated based on the matrix formula for thin film optics. The simulation results indicate the influence of the transition layers and the three thin-film layers except glass on the transmittance spectra. In addition, a fitting coefficient needed for error modification enters into the fitted formula. The fitting results show that the relative error in the full spectrum reduces from 19.51% to 4.35% after the formula is modified. The coefficient and the thicknesses are gained corresponding to the minimum relative error, meanwhile each layer and total thin-film thickness deviation in the module can be controlled within 73. The presence of glass layer roughness, layer interface effects and surface oxides is interpreted on the modification.

关 键 词：GaAs photocathode transmission-mode optical properties matrix formula 

分 类 号：TN383.4[电子电信—物理电子学]