Ultra-sensitive Mid-Wavelength-infrared Upconversion Detector

We have proposed and experimentally demonstrated an efficient ultra-sensitive mid-wavelength-infrared (MWIR) detector using a periodically poled lithium niobate nonlinear crystal and a silicon single-photon counting module. The involved frequency upconversion technique can spectrally convert the MWIR signal photons to the short-wavelength-infrared (SWIR) region. The internal quantum efficiency (QE) of the upconversion detector (UPD) reaches 8.87% at an average pump power of 10.67 W. The noise equivalent power of the UPD is measured as 3.24 x 10-15 W/Hz1/2 at the MWIR wavelength of 4.6 mu m. In addition, the long-term stability is manifested by at least 12 h of operation with a relative fluctuation in the count rates as low as 0.35%.