Mid-infrared single-photon counting.
We report a procedure to detect mid-infrared single photons at 4.65 microm by means of a two-stage scheme based on sum-frequency generation, by using a periodically poled lithium niobate nonlinear crystal and a silicon avalanche photodiode. An experimental investigation shows that, in addition to a high timing resolution, this technique yields a detection sensitivity of 1.24 pW with 63 mW of net pump power.
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