Experimental investigation on two-photon absorption in silicon avalanche photodiode

Two-photon absorption (TPA) in Si avalanche photodiode (APD) was investigated for infrared photon in 1550-nm telecom band with different frequencies, intensities, under different bias voltage. By measurement of the TPA efficiency for photon frequency from 186.3 to 196.1 THz in detail, it was found that it decreases when the photon frequency goes up while a certain optimal TPA efficiency is around 190.5 THz for the APD under test. It can be observed from the experiments that the TPA efficiency increases until a certain intensity (The peak value of light intensity in this experiment is less than 10 mW) and then it decreases.