Nanophotonics (Jun 2024)

Entangled photon-pair generation in nonlinear thin-films

  • Santos Elkin A.,
  • Weissflog Maximilian A.,
  • Pertsch Thomas,
  • Setzpfandt Frank,
  • Saravi Sina

DOI
https://doi.org/10.1515/nanoph-2024-0111
Journal volume & issue
Vol. 13, no. 18
pp. 3545 – 3561

Abstract

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We develop a fully vectorial and non-paraxial formalism to describe spontaneous parametric down-conversion in nonlinear thin films. The formalism is capable of treating slabs with a sub-wavelength thickness, describe the associated Fabry–Pérot effects, and even treat absorptive nonlinear materials. With this formalism, we perform an in-depth study of the dynamics of entangled photon-pair generation in nonlinear thin films, to provide a needed theoretical understanding for such systems that have recently attracted much experimental attention as sources of photon pairs. As an important example, we study the far-field radiation properties of photon pairs generated from a high-refractive-index nonlinear thin-film with zinc-blende structure that is deposited on a linear low-refractive-index substrate. In particular, we study the thickness-dependent effect of Fabry–Pérot interferences on the far-field radiation pattern of the photon pairs. We also pay special attention to study of entanglement generation, and find the conditions under which maximally polarization-entangled photon pairs can be generated and detected in such nonlinear thin-films.

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