Bonn 2025 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 49: Poster – Photonics, Lasers, and Applications

Q 49.11: Poster

Wednesday, March 12, 2025, 17:00–19:00, Tent

Towards Accurate Group Index Measurement in Lithium Niobate Waveguide Resonator — •Stefan Kazmaier and Kaisa Laiho — German Aerospace Center (DLR e.V.), Institute of Quantum Technologies, Wilhelm-Runge-Str. 10, 89081 Ulm, Germany

Lithium niobate (LN) is one of the most used materials in nonlinear quantum optics for the generation of quantum light. The spectral properties of the generated states are influenced by the group indices of the interacting modes, since they ultimately dictate the so-called joined spectral amplitude. However, the group index is often only simulated instead of measured accurately, which may lead to wrong conclusions. Therefore, we show a linear optical measurement of the group index and the optical losses in a peridodically-poled LN waveguide (WG). For that purpose, we measure the transmission spectrum of a LN WG resonator, allowing us to determine the birefringence of the group index for varying wavelengths and temperatures [1]. Altogether, our results help in interpreting the spectral properties of quantum states more accurately.

[1] Hofstetter and Thornton Opt. Lett. 22 1831-1833 (1997)

Keywords: Spectrum analysis; Group index measurement; Fabry-Perot resonator; Lithium niobate waveguide