A device and method for post-fabrication trimming of an optical ring resonator using a dopant-based heater is provided. An optical ring resonator at the device can be heated using heaters in an optical slab from which the optical ring resonator extends, the heater including a non-uniform doping profile. A controller determines an initial resonance frequency and a target resonance frequency of the optical ring resonator. The controller applies predetermined electrical parameters to the heater using electrical connections to shift a resonance frequency of the optical ring resonator from the initial resonance frequency to the target resonance frequency by causing the dopant in the heater to migrate.