Quantum correlations across two octaves from combined up and down conversion

TL;DR

This paper introduces a cascaded optical system combining OPO and SHG to generate and control quantum correlations across two octaves of frequency, enhancing entanglement and squeezing at multiple frequencies.

Contribution

It presents a novel cascaded system integrating OPO and SHG, analyzing its quantum correlations, threshold behavior, and control mechanisms for EPR entanglement.

Findings

Quantum correlations are tunable via damping rates and nonlinearities.

The system's threshold is modified by SHG interactions.

EPR correlations can be controlled with seed fields.

Abstract

We propose and analyse a cascaded optical parametric system which involves three interacting modes across two octaves of frequency difference. Our system, combining degenerate optical parametric oscillation (OPO) with second harmonic generation (SHG), promises to be a useful source of squeezed and entangled light at three differing frequencies. We show how changes in damping rates and the ratio of the two concurrent nonlinearities affect the quantum correlations in the output fields. We analyse the threshold behaviour, showing how the normal OPO threshold is changed by the addition of the SHG interactions. We also find that the inclusion of the OPO interaction removes the self-pulsing behaviour found in normal SHG. Finally, we show how the Einstein-Podolsky-Rosen correlations can be controlled by the injection of a coherent seed field at the lower frequency.