Photo Ionization of Excited Atoms in Gas-Filled Photodiodes: Improved Detectivity with Microsecond-Order Risetime

Photoionization of excited atoms and resonant absorption effects, which can decrease gas breakdown thresholds by high-power lasers at decreasing wavelengths, also improve low intensity detection sensitivities of gas-filled photodiodes when such devices are biased with dc fields close to gas breakdown. Spectral results indicate very promising potential sensitivity for detecting ultra-violet raidation. D* even in the visible is comparible to that of silicon photodiodes. The "relatively" large dc bias fields employed here improve speed of response significantly. Over moderate (10 -7 - 10-8W) received signal powers response is non-linear with ¿ varying inversely with wavelength.