Controlling visibility in nonlinear interferometry for spectroscopy with undetected photons

Quantum nonlinear interferometers play an important role in quantum imaging and sensing applications. Here, we demonstrate the tailoring of the frequency-angular spectrum of such a device, where we use a linear dispersive medium as a phase corrector. By changing the thickness of the dispersive medium, we tune the phase of the interferometer, enabling control over the frequency-angular spectrum and visibility of the interference fringes. Utilizing the enhanced visibility achieved through our proposed technique, we show the application of a simple interferometer in spectroscopy with an undetected photon scheme. We distinguish different polymers by measuring their characteristic absorption features in the mid-infrared spectral range above 6 μm while detecting only photons in the visible range.