Sensitive Infrared Photon Counting Detection by Nondegenerate Two-Photon Absorption in Si APD

We report on the sensitive detection of photons at broadband infrared wavelengths based on the nondegenerate twophoton absorption in the Si avalanche photodiodes. The detected 1700 1850 nm infrared photon energy is lower than Si band gap and the energy difference is complemented by a high intensity pump laser field at 1550 nm. It is thus possible to capitalize on the low noise property of large band gap materials for detecting low energy photons. And the linear intensity response of the detector to the incident infrared photons was observed when the power of pump laser was about 12.42 µW, indicating the dominance of nondegenerate two-photon absorption in the infrared photon detection. An enhancement factor of 20 was observed for the incident signal photon numbers of ∼0.14X106 photons per pulse. We offer an alternative to sensitive detection of infrared light. This may also provide new ideas for broadband infrared photon detection in different applications such as optical comb laser ranging, infrared bio-image and so forth.