Efficient parametric generation of counterpropagating two-photon states

Abstract

Guided-wave parametric downconversion with a transverse pump is a versatile means to generate a wide range of two-photon states. We propose and compare some microcavity-based schemes for the generation of counterpropagating photon pairs, and we experimentally demonstrate a bright source emitting 1.2×10−11 pairs/pump photon for a 1.8 mm long waveguide. These results are promising for integrated quantum information technology.