Off-resonant emission of photon pairs in nonlinear optical cavities

TL;DR

This paper investigates how off-resonant frequency mismatches affect the generation and properties of entangled photon pairs in nonlinear optical cavities, providing models and experimental validation to enhance control over photon pair characteristics.

Contribution

It introduces a generic model for off-resonant cavity-assisted SPDC and SFWM and experimentally demonstrates the impact of frequency mismatch on photon generation in a WGMR.

Findings

Frequency mismatch reduces photon generation rate.

Mismatch distorts the spectral and temporal properties of photons.

Control of frequency mismatch enables tailored photon pair properties.

Abstract

Cavity-assisted spontaneous parametric down-conversion (SPDC) and spontaneous four-wave mixing (SFWM) in nonlinear optical materials are practical and versatile methods to generate narrowband time-energy entangled photon pairs. Time-energy entangled photons with tailored spectro-temporal properties are particularly useful for efficient quantum optical interfaces. In this work we study the generation of photon pairs in cavity-assisted SPDC and SFWM for the general case of off-resonant conversion, namely, when the frequencies of the generated photons do not match the cavity resonances. Such a frequency mismatch in particular depends on temperature and requires an additional control in the experiment. First, we propose a generic model, for description of cavity-assisted SPDC and SFWM. We show that in both processes the mismatch reduces the generation rate of photons, distorts the spectrum and the auto-correlation function of the generated fields, as well as affects the photon generation dynamics. Second, we verify the results experimentally using parametric generation of photon pairs in a nonlinear whispering gallery mode resonator (WGMR) as an experimental platform with controlled frequency mismatch. Our work reveals the role of the frequency mismatch in the photon generation process and shows a way to control it. Obtained results constitute one more step in the direction of full control over the spectro-temporal properties of entangled photon pairs and the heralded generation of single-photon pulses with a tailored temporal mode.