Waveguide-based single-pixel up-conversion infrared spectrometer
  A periodically poled lithium niobate (PPLN) waveguide-based single-pixel up-conversion infrared spectrometer was demonstrated. Sum-frequency generation between a 1.5 micrometer band scanning pump laser and a 1.3 micrometer band signal generated visible radiation which was detected by a silicon single-photon detector. The noise equivalent power of the upconversion spectrometer was two-orders-of-magnitude lower than that of a commercial optical spectrum analyzer. 
Qiang Zhang, Carsten Langrock, M. M. Fejer, Yoshihisa Yamamoto