Low-threshold Optical Parametric Oscillations in a Whispering Gallery Mode Resonator

TL;DR

This paper demonstrates a low-threshold optical parametric oscillator using a whispering gallery mode resonator made of Lithium Niobate, achieving efficient frequency conversion and potential applications in quantum optics.

Contribution

It provides a theoretical analysis linking phase matching in WGM resonators to angular momentum sum rules and experimentally realizes a low-threshold, single-mode OPO.

Findings

Achieved a 6.7 micro-W threshold for the OPO.

Demonstrated linewidth under 10 MHz.

Validated the theoretical phase matching analysis.

Abstract

In whispering gallery mode (WGM) resonators light is guided by continuous total internal reflection along a curved surface. Fabricating such resonators from an optically nonlinear material one takes advantage of their exceptionally high quality factors and small mode volumes to achieve extremely efficient optical frequency conversion. Our analysis of the phase matching conditions for optical parametric down conversion (PDC) in a spherical WGM resonator shows their direct relation to the sum rules for photons' angular momenta and predicts a very low parametric oscillations threshold. We realized such an optical parametric oscillator (OPO) based on naturally phase-matched PDC in Lithium Niobate. We demonstrated a single-mode, strongly non-degenerate OPO with a threshold of 6.7 micro-W and linewidth under 10 MHz. This work demonstrates the remarkable capabilities of WGM-based OPOs and opens the perspectives for their applications in quantum and nonlinear optics, particularly for the generation of squeezed light.