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TT: Fachverband Tiefe Temperaturen

TT 18: Superconductivity: Poster

TT 18.56: Poster

Montag, 18. März 2024, 15:00–18:00, Poster C

Pyroelectricity in a Lithium Niobate Phase Modulator During Thermal Transition to and from Cryogenic Temperatures — Frederik Thiele, •Thomas Hummel, Nina A. Lange, Felix Dreher, Maximilian Protte, Felix vom Bruch, Sebastian Lengeling, Harald Herrmann, Christof Eigner, Christine Silberhorn, and Tim J. Bartley — Department of Physics & Institute for Photonic Quantum Systems, Paderborn University, Warburger Straße 100, 33098 Paderborn, Germany

Lithium niobate (LiNbO₃) is a promising platform for quantum optics, due to the high nonlinearity, electro-optic effect, and low loss waveguiding. Integrating superconducting nanowire single-photon detectors requires operation at cryogenic temperatures. The transition to and from cryogenic temperatures creates free charge carriers due to the pyroelectric effect. These charge carriers are distributed in the material, inducing electric fields. The electric fields affect the refractive index inside, and the electrical structures on top of the LiNbO₃. When the electric fields are too strong, charge carriers recombine causing a local electrical discharge. We measure the electrical discharges and changes in birefringence with a phase-modulator in bulk Z-cut LiNbO₃ with titanium in diffused waveguides. For this we connect a current meter across the electrodes to measure the electrical discharges, and put the phase modulator in the Sénarmont configuration to measure changes in the birefringence. Monitoring these properties during thermal transition shows correlations between electrical discharges and optical discontinuities, where the rate of events depends on the temperature.

Keywords: Lithium Niobate; Pyroelectricity; Cryogenics; Electro-optic modulator