Highly tunable low-threshold optical parametric oscillation in radially poled whispering gallery resonators

TL;DR

This paper demonstrates highly tunable, low-threshold optical parametric oscillation in radially poled whispering gallery resonators made of lithium niobate, with broad wavelength tuning achieved via temperature control and structural adjustments.

Contribution

It introduces a novel radially poled WGR design enabling extensive tunability and low-threshold operation for optical parametric oscillation.

Findings

Tuning range from 1.78 to 2.5 micrometers for signal and idler waves.

Oscillation threshold in the milliwatt power range.

Enhanced tuning capabilities with slight off-centering of the radial domain structure.

Abstract

Whispering gallery resonators (WGR's), based on total internal reflection, possess high quality factors in a broad spectral range. Thus, nonlinear optical processes in such cavities are ideally suited for the generation of broadband or tunable electromagnetic radiation. Experimentally and theoretically, we investigate the tunability of optical parametric oscillation in a radially structured WGR made of lithium niobate. With a 1.04 /mum pump wave, the signal and idler waves are tuned from 1.78 to 2.5 \mum - including the point of degeneracy - by varying the temperature between 20 and 62 {\deg}C. A weak off-centering of the radial domain structure extends considerably the tuning capabilities. The oscillation threshold lies in the mW-power range.