This paper compares the signal-to-noise ratio obtained using an InSb photodiode for infrared (IR) polarization spectroscopy to that obtained using an upconversion detector, and shows a factor 64 improvement by the change. Upconversion detection is based on using sum frequency generation to move the IR optical signal to near-visible wavelengths to improve the sensitivity.
Keywords: PPLN; Polarization spectroscopy; SNR; periodically poled lithium niobate; signal-to-noise ratio; upconversion.