Quantum properties of counter-propagating two-photon states generated in a planar waveguide

TL;DR

This paper investigates the quantum properties of photon pairs generated in a nonlinear planar waveguide, demonstrating how pump parameters influence entanglement and spectral characteristics, with potential for tunable quantum light sources.

Contribution

It introduces a method to control and analyze the entanglement and spectral properties of photon pairs in a planar waveguide by adjusting pump parameters.

Findings

Spectral widths of signal and idler fields can be tuned by pump parameters.

Degree of entanglement varies with pump-beam characteristics.

Entanglement entropy can be quantified using spectral measurements and Hong-Ou-Mandel interference.

Abstract

A nonlinear planar waveguide pumped by a beam orthogonal to its surface may serve as a versatile source of photon pairs. Changing pump-pulse duration, pump-beam transverse width, and angular decomposition of pump-beam frequencies characteristics of a photon pair including spectral widths of signal and idler fields, their time durations as well as degree of entanglement of two fields can be changed significantly. Using the measured spectral widths of the down-converted fields and width of a coincidence-count dip in a Hong-Ou-Mandel interferometer entropy of entanglement can be determined.