Nonlinear power dependence of the spectral properties of an optical parametric oscillator below threshold in the quantum regime

TL;DR

This paper investigates the nonlinear spectral properties of an optical parametric oscillator below threshold, revealing phenomena like frequency pulling and broadening that differ from traditional linear models, especially in high-rate photon generation regimes.

Contribution

It provides a detailed analysis of the nonlinear effects in cavity-assisted parametric down-conversion below threshold, highlighting deviations from linear approximations in the intermediate regime.

Findings

Frequency pulling observed in spectral properties

Broadening of temporal correlations in photon pairs

Significant differences from linear cavity models in high-rate regimes

Abstract

Photon pairs and heralded single photons, obtained from cavity-assisted parametric down-conversion (PDC), play an important role in quantum communications and technology. This motivated a thorough study of the spectral and temporal properties of parametric light, both above the Optical Parametric Oscillator (OPO) threshold, where the semiclassical approach is justified, and deeply below it, where the linear cavity approximation is applicable. The pursuit of a higher two-photon emission rate leads into an interesting intermediate regime where the OPO still operates considerably below the threshold but the nonlinear cavity phenomena cannot be neglected anymore. Here, we investigate this intermediate regime and show that the spectral and temporal properties of the photon pairs, as well as their emission rate, may significantly differ from the widely accepted linear model. The observed phenomena include frequency pulling and broadening in the temporal correlation for the down-converted optical fields. These factors need to be taken into account when devising practical applications of the high-rate cavity-assisted SPDC sources.