Freiburg 2024 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 39: Poster V
Q 39.6: Poster
Wednesday, March 13, 2024, 17:00–19:00, Aula Foyer
Spectral purification of spontaneous parametric down-conversion photons via spatial filtering — •Michael Schlosser1, Ria G. Krämer2, Julian Münzberg1, Daniel Richter2, Stefan Nolte2,3, Gregor Weihs1, and Robert Keil1 — 1Institut für Experimentalphysik, Universität Innsbruck, Austria — 2Institute of Applied Physics, Abbe Center of Photonics, Friedrich Schiller University Jena, Albert-Einstein-Str. 15, D-07745 Jena, Germany — 3Fraunhofer Institute for Applied optics and Precision Engineering IOF, Center of Excellence in Photonics, Albert-Einstein-Str. 7, D-07745 Jena, Germany
The application of photonic quantum technologies on a larger scale typically requires photons from independent sources to be indistinguishable. We report on a spontaneous parametric down-conversion (SPDC) source, which can simultaneously emit two photon pairs with a wavelength of 795nm. The joint spectral intensity of the pairs is measured via time-of-flight spectroscopy utilising femtosecond-laser inscribed fiber Bragg gratings as dispersive elements. The spectral purity extracted from this substantially exceeds the measured Hong-Ou-Mandel (HOM) interference visibility of 39(2)%, which suggests the presence of spatial-spectral correlations in the pump. To counter these, spatial filtering is investigated. A short single-mode fiber inserted into the pump indeed removes these correlations, increasing the HOM visibility to 79(15)%. Alternatively, inserting a 15μm-diameter pinhole in the Fourier plane of a telescope increases the indistinguishability to 48(2)%, while providing a steady power transmission.
Keywords: spontaneous parametric down-conversion; fiber Bragg grating; time-of-flight spectroscopy; spatial mode filtering