lithium niobate 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 …