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FM: Fall Meeting

FM 57: Quantum Sensing: Spectroscopy I

FM 57.7: Talk

Mittwoch, 25. September 2019, 15:45–16:00, 2006

Mid-Infrared Spectroscopy with Nonlinear Interferometers — •Chiara Lindner, Sebastian Wolf, Jens Kießling, and Frank Kühnemann — Fraunhofer Institute for Physical Measurement Techniques IPM, Heidenhofstraße 8, 79110 Freiburg, Germany

Spontaneous parametric down-conversion (SPDC) is one of the most important sources for entangled photon pairs in quantum optics. Its application in nonlinear interferometers is the foundation of quantum imaging and spectroscopy. Nonlinear interferometers rely on a quantum effect: The signal photons of two SPDC-sources show interference if the corresponding idler photons are indistinguishable. Any absorption of the idler photons in between the sources lowers the visibility of both signal and idler interference contrast. This allows measuring the absorption and dispersion of samples in the mid-IR range by detecting the interference pattern of the visible photon counterparts.

In our work, we present a nonlinear interferometer for mid-infrared spectroscopy in Michelson-configuration. Hereby, we infer the spectral information on the mid-infrared light directly from the visible interference pattern without the need for spectral selection. Using non-collinear broadband SPDC created in a periodically poled lithium niobate crystal, our interferometer covers a large spectral bandwidth (>100 cm⁻¹ in mid-infrared) in one single measurement. With different poling periods and crystal temperatures, an infrared spectrum ranging from 3.2-3.8 µm wavelength is demonstrated. Our experimental results are discussed and compared to other works in our field.