Photorefraction-induced Bragg scattering in cryogenic lithium niobate ring resonators

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