Abstract: A method of wavelength tuning in a silicon photonics circuit includes receiving a bus waveguide, a ring resonator optically coupled to the bus waveguide, and a dielectric layer over the bus waveguide and over the ring resonator. The method further includes performing a first heat process at a first temperature to heat up the dielectric layer, where the first heat process shifts an initial resonance wavelength of the ring resonator to a first resonance wavelength shorter than the initial resonance wavelength. The first heat process permanently shifts the initial resonance wavelength to the first resonance wavelength, the first resonance wavelength being a wavelength when no heat is being applied to the ring resonator.