Detection of mid-IR radiation by sum frequency generation for free space optical communication

We present an experiment where mid-infrared radiation is detected indirectly via the second-order non-linear process of sum frequency generation. The mid-infrared sources used for the experiment are quantum cascade lasers, and we use a pump wavelength that yields an up-converted wavelength within the detection window of Silicon avalanche photo diodes. Compared with direct detection using state-of-the-art mid-infrared semiconductor detectors, the detection scheme we propose in this paper has the advantages of greater bandwidth and lower noise equivalent power.