A phenomenon of LT-GaAs photoconductive switch triggered by 800 nm femtosecond laser

Abstract

The Ti oxide is used as insulator between the electrodes to substitute the air gap of photoconductive semiconductive switch (PCSS). The width of the oxide is smaller than 100 nm, the electrodes and substrate's materials are Ti and LT-GaAs respectively. The simulation result indicated that the LT-GaAs photoconductive semiconductive switch doesn't work in the linear mode absolutely when it is triggered by femtosecond laser with about 10 voltages electric field bias. The pulse width of the femtosecond laser is about several tens of fs, the central wavelength is 800 nm, and the pulse energy is about 1mJ. In the tail of the voltage or current output characteristic of the photoconductive switch, another little positive peak appeared with a short time delay after the main linear pulse. This phenomenon is different from the normal switch witch uses several tens μm width's air gap. In this paper, this phenomenon is analyzed and the method to avoid such kind of non-linearity output is discussed.