Photorefraction-induced Bragg scattering in cryogenic lithium niobate ring resonators

TL;DR

This paper demonstrates how photorefractive effects in cryogenic lithium niobate ring resonators induce Bragg scattering, enabling optically programmable photonic components through reconfigurable mode splitting.

Contribution

It reveals the mechanism of photorefraction-induced Bragg scattering in high-Q cryogenic lithium niobate resonators and explores its potential for reconfigurable photonic devices.

Findings

Photorefractive effect creates a long-lived space-charge field.

Refractive index modulation enhances back scattering.

Mode splitting can be reconfigured optically.

Abstract

We report intracavity Bragg scattering induced by photorefractive (PR) effect in high-Q lithium niobate (LN) ring resonators at cryogenic temperatures. We show that, when a cavity mode is strongly excited, the PR effect imprints a long-lived periodic space-charge field. This residual field in turn creates a refractive index modulation pattern that dramatically enhances the back scattering of an incoming probe light, and results in selective and reconfigurable mode splittings. This PR-induced Bragg scattering effect, despite being undesired for many applications, could be utilized to enable optically programmable photonic components.