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Spectral and temporal properties of type-II parametric down-conversion: The impact of losses during state generation

Denis A. Kopylov1,2,*, Michael Stefszky2,3, Torsten Meier1,2, Christine Silberhorn2,3, and Polina R. Sharapova1

  • 1Department of Physics, Paderborn University, Warburger Str. 100, D-33098 Paderborn, Germany
  • 2Institute for Photonic Quantum Systems (PhoQS), Paderborn University, Warburger Str. 100, D-33098 Paderborn, Germany
  • 3Integrated Quantum Optics, Paderborn University, Warburger Str. 100, D-33098 Paderborn, Germany

  • *Contact author: denis.kopylov@uni-paderborn.de
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Phys. Rev. Research 7, 033122 – Published 5 August, 2025

DOI: https://doi.org/10.1103/zp72-7qwl

Abstract

In this paper, we theoretically study the spectral and temporal properties of pulsed spontaneous parametric down-conversion (SPDC) generated in lossy waveguides. Our theoretical approach is based on the formalism of Gaussian states and the Langevin equation, which is elaborated for weak parametric down-conversion and photon-number-unresolved click detection. Using the example of frequency-degenerate type-II SPDC generated under the pump-idler group-velocity-matching condition, we show how the joint-spectral intensity, mode structure, normalized second-order correlation function, and Hong-Ou-Mandel interference pattern depend on internal losses of the SPDC process. We found that the joint-spectral intensity is almost insensitive to internal losses, while the second-order correlation function shows a strong dependence on them, being different for the signal and idler beams in the presence of internal losses. Based on the sensitivity of the normalized second-order correlation function, we show how its measurement can be used to experimentally determine internal losses.

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Phys. Rev. Research 7, 033122– Published 5 August, 2025
  • Received 28 January 2025
  • Accepted 18 June 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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