Photon-Pair Generation in the Mid-Infrared using AgGaS2 Crystals

Many quantum optics applications, especially in sensing and imaging, are based on correlated photon pairs with non-degenerate wavelengths. Often, one photon in an easily accessible spectral range like the visible is measured, whereas the object under test is probed by the correlated partner photon in a different wavelength range [1] . However, in most typically used crystals, the wavelength range of the long-wavelength photon is limited by absorption in the nonlinear medium which prohibits efficient photon-pair generation. Here, we demonstrate photon-pair generation in silver gallium sulfide AgGaS 2 (AGS), a nonlinear crystal with a transparency range spanning from 0.5 μm to 13 μm, which covers the molecular fingerprint region relevant for many spectroscopy applications.