We theoretically and experimentally investigate the spectral response of an upconversion detector and discuss implications for its use as an infrared spectrometer. Upconversion detection is based on high-conversion-efficiency sum-frequency generation (SFG). The spectral selectivity of an upconversion spectrometer is determined by the SFG spectral response function. This function changes with varying pump power. Working at maximum internal conversion efficiency is desirable for high sensitivity of the system, but the spectral response function is different at this pump power compared to the response function at low power. We calculate the theoretical spectral response of the upconversion detector as a function of pump power and obtain excellent agreement with upconversion spectra measured in a periodically poled LiNbO3 waveguide.
Citation: Optics Express
Pub Type: Journals
infrared spectroscopy, nonlinear optics, sum-frequency generation