A wavelength variable visible-infrared photon pair source using a LiNbO3 crystal in the mid-infrared region

Visible-infrared photon pair sources working in broadband mid-infrared region are useful for applications such as heralded mid-infrared single photon sources. Here, we demonstrate experimentally a wavelength variable visible-infrared photon pair source in the mid-infrared region over a wide spectral range of 2 to 5 μm. By changing the angle of the nonlinear crystal in the source, the observed wavelengths of the signal photons change from 600 to 965 nm, corresponding to the idler wavelengths in 1186-4694 nm.