First demonstration of a temporal coherence analysis through a parametric interferometer

We analyze the temporal coherence of an optical infrared radiation in the visible domain by using a Mach–Zehnder interferometer and a wavelength conversion stage in each arm. We exploit a sum frequency generation process in bulk PPLN crystal to convert the infrared radiation at 1.55 μm into 0.63 μm before the interferometric mixing. The applicability of the Wiener–Kintchine theorem through up-conversion processes is here demonstrated by direct comparisons among visible and infrared measurements.