SAMOP 2023 – scientific programme

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QI: Fachverband Quanteninformation

QI 23: Poster II (joint session QI/Q)

QI 23.27: Poster

Wednesday, March 8, 2023, 16:30–19:00, Empore Lichthof

Predicting coupling efficiency of KTP waveguides and fibers by mode measurement — •Florian Lütkewitte, Jan-Lucas Eickmann, Kai Hong Luo, Michael Stefszky, Laura Padberg, Harald Herrmann, and Christine Silberhorn — Paderborn University, Integrated Quantum Optics, Institute of Photonic Quantum Systems (PhoQS), Warburger Str. 100, 33098, Paderborn, Germany

Reliable generation of photonic quantum states is of high importance for fundamental physics and quantum networks. Due to its unique dispersion properties, spontaneous parametric downconversion (SPDC) in potassium titanyl phosphate (KTP) has gathered extensive research attention as a source of heralded single photons in the telecom range. Fiber-based devices allow for plug-and-play usage omitting time-intensive free-space coupling. Integration of SPDC sources in fiber networks can be achieved with fiber-pigtailed KTP waveguides. However, single-mode waveguides in KTP show imperfect overlap with single-mode fibers due to their asymmetry and a size-mismatch between modes. Thus, optimized mode-adapted fibers are required to obtain a plug-and-play heralded photon source in KTP. In this work, we measured the mode profile of waveguides and several tapered fibers. Comparing the mode overlap, the optimal waveguide-fiber combination has been determined with upper-bound coupling efficiency of (90 ± 1)%, based on the mode overlap integral over their measured mode profile.