Fig. 2. Mitigation of the photorefractive effect.

a Illustration of the PR-induced resonance instability resulting from a combination of absolute frequency shift and cancellation of voltage tunability after illumination. b The measured resonance frequency drift at zero-bias voltage after light illumination of oxide-clad (blue) and air-clad (green) architecture. The drift rate of the measured air-clad device is $~0.28\mathrm{pm/min}$ under 0.5 mW optical power in the waveguide. c The optical supermode splitting Δf as a function of DC bias for oxide-clad (blue) and air-clad (green) devices. The target microwave frequency is marked as a dashed line.