Infrared spectroscopy assisted by entangled photons
Anna V. Paterova, Shaun Lung, Dmitry A. Kalashnikov, S. P. Kulik, Leonid A. Krivitsky · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2016
We describe a proof-of-concept of a method for measurement of both real (refraction) and imaginary (absorption) part of the refractive index in the infrared (IR) range by measuring an interference pattern in the visible range without the need for any spectral and spatial selection. The concept is based on nonlinear interference of entangled photons, generated via Spontaneous Parametric Down Conversion (SPDC). In our interferometer, the phase of the signal photon in the visible range depends on the phase of an entangled IR photon. When the IR photon is traveling through the media of interest, its properties can be found from the observations of the visible photon.