Method for wavelength control of silicon photonic external cavity tunable laser

A tunable solid state laser device comprising:

• a semiconductor-based gain chip;
• and
• a silicon photonic filter chip with tuning capability, wherein the silicon photonic filter chip comprises:
• an input waveguide;
• a Sagnac interferometer optically connected to the input waveguide, comprising:
• at least two waveguide branches, and
• at least two ring resonators each coupled to a separate waveguide branch;
• at least two resistance heaters, each associated with one of the at least two ring resonators;
• and
• at least two resistance temperature sensors, each associated with one of the at least two resistance heaters,
• wherein a controller is connected to receive a signal from each of the at least two resistance temperature sensors to account for one or more temperature measurements in a feedback loop, and
• wherein a ring resonator, of the at least two ring resonators, is associated with a thermal isolation trench such that a corresponding resistance heater, a corresponding resistance temperature sensor, and the ring resonator are within a thermally isolated region from other components of the silicon photonic filter chip.