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THU: Thursday Contributed Sessions

THU 13: Poster Session: Applications

THU 13.39: Poster

Thursday, September 11, 2025, 16:30–18:30, ZHG Foyer 1. OG

Towards an integrated sensor for optimized OCT with undetected photons — •Franz Roeder, René Pollmann, Viktor Quiring, Christof Eigner, Benjamin Brecht, and Christine Silberhorn — Paderborn University, Integrated Quantum Optics, Institute for Photonic Quantum Systems (PhoQS), Warburger Straße 100, 33098 Paderborn, Germany

Quantum nonlinear interferometers, which can be constructed from cascaded parametric down-conversion (PDC) sources, are used for the realization of so-called measurements with undetected photons. These employ photons generated at non-degenerate wavelengths and allow to probe an object under test at a long wavelength, e.g., in the mid-IR, while detecting in a technically more accessible wavelength regime such as the near-IR. While many such systems rely on bulk nonlinear optics, integration is necessary for the development of practical quantum sensors.
Here, we realize a quantum nonlinear interferometer with a broadband, non-degenerate type-II PDC source based on a dispersion engineered periodically poled lithium niobate waveguide. We identify both the best interferometer configuration as well as the best operation mode for optimum performance in optical coherence tomography (OCT) with undetected photons. Our measurements show that practical OCT sensors are best realized in the so-called induced coherence configuration while employing temporal interferometry and photon counting, allowing for measurements at pump powers as low as 50 µW, orders of magnitude less than in other realizations.

Keywords: Quantum Sensing; Quantum Spectroscopy; Integrated Optics