Physical mechanism of two-photon response in semi-insulating GaAs

The physical mechanism of two-photon response (TPR) in semi-insulating GaAs is studied. The measured photocurrent generated from the fabricated hemispherical GaAs sample responding to 1.3μm continuous wave laser shows a quadratic dependence on the coupled optical power and no saturation with the bias. The angular dependence of the photocurrent on the azimuth is in agreement with the anisotropy of double-frequency absorption
(DFA) in GaAs single crystals. These results demonstrate DFA is the dominant mechanism of TPR in GaAs.