Highly efficient generation of single-mode photon pairs from a crystalline whispering-gallery-mode resonator source

Abstract

We report a highly efficient source of narrow-band photon pairs based on parametric down-conversion in a crystalline whispering-gallery-mode resonator. Remarkably, each photon of a pair is detected in a single spatial and temporal mode, as witnessed by Glauber’s autocorrelation function. We explore the phase-matching conditions in spherical geometries, and determine the requirements for single-mode operation. Understanding these conditions has allowed us to experimentally demonstrate a single-mode pair-detection efficiency of 1.13×106 pairs/s per mW pump power per 26.8 MHz bandwidth.