  We demonstrate upconversion single-photon detection for the 1550-nm band
using a PPLN waveguide, long-wavelength pump, and narrowband filtering using a
volume Bragg grating. We achieve total-system detection efficiency of around
30% with noise at the dark-count level of a silicon APD. Based on the new
detector, a single-pixel up-conversion infrared spectrometer with a noise
equivalent power of -142 dBm was demonstrated, which was better than liquid
nitrogen cooled InGaAs arrary.
