Influence of deformed window glass for GaAs photocathode on light transmission

To enhance the spatial resolution capability of transmission-mode NEA GaAs photocathodes, this study employed a white-light interferometer to measure the surface configurations of photocathode components post thermal compression bonding. Precise fitting of the surface configurations was achieved using Zernike polynomials, successfully deriving the Zernike polynomial coefficients. Further, these calculated results were integrated into optical design software for modeling, aiming to elucidate the relationship between the photocathode's transfer function and surface configurations. The findings clearly indicate that the MTF value corresponding to 60lp/mm remains stable within the 0° and 5° field angles. However, as the field angle extends to 20°, there is a significant decline in the MTF value. Among them, the transfer performance of the plano-concave photocathode decreases most prominently, followed by the flat structure, while the plano-convex structure exhibits the least decline. Overall, this research provides invaluable references for the further advancement of photocathode technology.