Measurement of spectral response of photocathodes and its application

Spectral response is an important parameter of photocathodes. By analyzing measured spectral response curves, much information about the photocathodes can be obtained which is useful to investigation of photocathodes. The principle measuring the spectral response of photocathodes is expounded in this paper. The on-line measurement system was developed, which can measure the spectral response of optoelectronic devices within range of 400nm~1800nm. It can also measure the reflectance of monochromatic light, the monochromatic photocurrent, and integral sensitivity of photocathodes. The measurement system was used to on-line measure spectral response of multi-alkali photocathodes(Na2KSb:Cs) when they are being prepared. Combining measurement of reflectance of monochromatic light, by which the thickness of photocathodes can be timely obtained, the optimum thickness of photocathode is looked for. The measurement system also used in the investigation of GaAs:Cs-O NEA photocathodes. Surface escape probability, electron diffusion length and back-interface recombination velocity are the factors that influence the quantum yield of NEA photocathode. It is difficult to directly measure these parameters. But they can be obtained by simulation of measured spectral response. The reflective GaAs samples were activated and evaluated. The results were given and analyzed.