Naturally-phasematched second harmonic generation in a whispering gallery mode resonator

TL;DR

This paper reports the first demonstration of natural phase matching for second harmonic generation in a high-Q Lithium Niobate whispering gallery mode resonator, achieving high efficiency at very low pump power, with potential quantum optics applications.

Contribution

It introduces a novel natural phase matching technique in whispering gallery mode resonators, enabling efficient frequency doubling at significantly lower pump power than previous methods.

Findings

Achieved 9% conversion efficiency at 30 μW pump power

Saturation pump power of 3.2 mW is nearly two orders lower than state-of-the-art

Theoretical analysis provides relative efficiencies for various modes

Abstract

We demonstrate for the first time natural phase matching for optical frequency doubling in a high-Q whispering gallery mode resonator made of Lithium Niobate. A conversion efficiency of 9% is achieved at 30 micro Watt in-coupled continuous wave pump power. The observed saturation pump power of 3.2 mW is almost two orders of magnitude lower than the state-of-the-art. This suggests an application of our frequency doubler as a source of non-classical light requiring only a low-power pump, which easily can be quantum noise limited. Our theoretical analysis of the three-wave mixing in a whispering gallery mode resonator provides the relative conversion efficiencies for frequency doubling in various modes.