Ultra sensitive NIR spectrometer based on frequency up-conversion detector

We developed a spectrometer for signals at single photon levels in the near infrared (NIR) region based on a tunable upconversion detector. This detector uses a 5-cm periodically poled lithium niobate (PPLN) waveguide to convert NIR photons to a shorter wavelength that are then detected by a silicon avalanche photodiode. The sensitivity of this spectrometer is -126 dBm, which is three orders-of-magnitude higher than any commercial optical spectrum analyzer in this wavelength range. Additionally, we use two PPLN waveguides to implement a polarization-independent upconversion spectrometer, and use it to study a fiber-based quantum communication system.