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Frontiers in Optics

Bi-Photon Correlation Time Measurements with a Two-Colour Broadband SU(1,1) Interferometer

Franz Roeder, Michael Stefszky, René Pollmann, Matteo Santandrea, Victor Quiring, Raimund Ricken, Christof Eigner, Benjamin Brecht, Christine Silberhorn

Published Jan 1, 2022• 2 citations
Publisher

Abstract

We demonstrate spectral and temporal interferometry using a SU(1,1) interferometer based on ultra-broadband, non-degenerate dispersion-engineered parametric down-conversion in nonlinear waveguides. We extract the ultra-short biphoton correlation time and realise dispersion sensitive spectroscopy.
DOI
10.1364/fio.2022.fw1b.3

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The spectral-temporal correlation and the correlation time of a biphoton wavepacket generated in the process of parametric down-conversion (PDC), is of great importance for a broad range of quantum experiments. We utilise an integrated PDC source to generate biphotons with different types of spectral-temporal correlations and probe their respective correlation times. The outcomes confirms that the correlation time is independent of the coherence time of the pump light, and it is only determined by the waveguide length and its dispersion properties. Furthermore, we investigate the properties of the PDC biphoton wavepacket exhibiting different types of spectral-temporal correlations and their suitability for quantum-enhanced applications.
The visibility of nonlinear SU(1,1) interference directly reflects the nonclassical properties of entangled bi-photons and squeezed light with practically unlimited bandwidth, high efficiency and ultra-high photon flux, orders of magnitude beyond the abilities of standard photo-detectors. We study experimentally the dependence of the SU(1,1) visibility on the phase matching conditions and beam parameters in a free-space configuration, and show that maximal SU(1,1) visibility requires extreme collinear conditions, which deviate from the conditions for maximal nonlinear conversion. We demonstrate near-ideal visibility of ∼95% (limited only by internal loss) in an ultra-broadband SU(1,1), interferometer with over 120 THz of squeezed light bandwidth. Utilizing this analysis we demonstrate efficient detection of the spectral phase of single-cycle bi-photons and precise compensation of the dispersion over a full octave of bandwidth.
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Broadband photon-pairs from a parametric down-conversion (PDC) source are essential for quantum optics experiments in the context of spectroscopy, quantum optical coherence tomography and entangled two-photon absorption [1]–[2]. Entangled two-photon absorption benefits from the ultra-short correlation time of a highly time-frequency entangled photon-pair which increases the absorption cross-section while in spectroscopy, broad spectral coverage in the mid-infrared allows one to enter the regime of life science applications.