Inversion of optical constants and thickness of multialkali photocathodes

Yun Wang; Jinneng Zeng; Yanni Gong; Bingxiang Gao; Yaobin Li; Heng Zhao; Yijin Wang; Tingtao Li; Xiaofeng Li

doi:10.1117/12.2666324

4 April 2023 Inversion of optical constants and thickness of multialkali photocathodes

Yun Wang, Jinneng Zeng, Yanni Gong, Bingxiang Gao, Yaobin Li, Heng Zhao, Yijin Wang, Tingtao Li, Xiaofeng Li

Proceedings Volume 12617, Ninth Symposium on Novel Photoelectronic Detection Technology and Applications; 126174F (2023) https://doi.org/10.1117/12.2666324
Event: 9th Symposium on Novel Photoelectronic Detection Technology and Applications (NDTA 2022), 2022, Hefei, China

Abstract

The image intensifier is the core component of all kinds of low-light-level night vision devices, which are widely used in security, medicine, biology, and other fields of detection and imaging devices. Multialkali photocathode is one of the important parts of the image intensifier photoelectric conversion. Its optical constant and thickness will affect the sensitivity of the image intensifier. The photocathode material is a chemically active alkali metal (Na₂KSb (Cs)). When the photocathode is removed from the high-vacuum alkali source environment of the image enhancement tube, its properties will change. Therefore, it has been impossible to directly measure the optical constant and thickness of the photocathode. In this paper, we established the photocathode optical model with the help of the Snellmeier dispersion model. The optical constants and thickness of the photocathode in the visible band 380nm-780nm are obtained for the first time by the full-spectrum fitting method. The deviation between the fitted value and the measured value is 0.03%, which is in good agreement. The optical constants and thickness of the photocathode obtained in this paper can provide more accurate guidance for the optical system design of image intensifiers. In addition, the method can be extended to the analysis of optical properties of other easily oxidized thin film materials by changing the dispersion formula, which has practical significance in the fields of vacuum optoelectronics and optical thin films.

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Yun Wang, Jinneng Zeng, Yanni Gong, Bingxiang Gao, Yaobin Li, Heng Zhao, Yijin Wang, Tingtao Li, and Xiaofeng Li "Inversion of optical constants and thickness of multialkali photocathodes", Proc. SPIE 12617, Ninth Symposium on Novel Photoelectronic Detection Technology and Applications, 126174F (4 April 2023); https://doi.org/10.1117/12.2666324

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KEYWORDS

Refractive index

Image intensifiers

Reflectivity

Thin films

Transmittance

Film thickness

Night vision

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