An optical device, comprising: a substrate; an intermediate layer deposited on the substrate; a semiconductor layer, deposited on the intermediate layer, that includes a tunable optical waveguide; a top layer, deposited on the semiconductor layer, which includes vias from an upper surface of the top layer to a bottom surface of the top layer which is proximate to the semiconductor layer; and electrodes (418, 612), deposited on the top layer and in the vias, which electrically couple to the semiconductor layer, wherein the electrodes are configured to reduce heat flow in a plane of the optical waveguide along a direction approximately perpendicular to an axis of the optical waveguide, wherein the electrodes are thermally coupled to the optical waveguide by multiple regions in the semiconductor layer which have a lower thermal conductivity than additional regions that are interdigited with the regions, wherein a given region has an axis that is approximately perpendicular to an axis of the optical waveguide in a plane of the semiconductor layer, wherein doping of the semiconductor layer in the given region exceeds doping of the semiconductor layer in the optical waveguide, the optical device being characterised in that the doping of the semiconductor layer in the optical waveguide defines a heater that facilitates thermal tuning of the optical waveguide, wherein the doping of the semiconductor layer in the optical waveguide alternates between a first type of region and a second type of region along the axis of the optical waveguide, and wherein the first type of region has a lower doping of the semiconductor layer than the second type of region, thereby reducing optical losses in the optical waveguide, and wherein the power consumption associated with thermal tuning of the waveguide is reduced by reducing thermal coupling from an external environment to the optical waveguide by said doping of the semiconductor layer in the given regions to said exceeding the doping of the semiconductor layer in the optical waveguide. a substrate; an intermediate layer deposited on the substrate; a semiconductor layer, deposited on the intermediate layer, that includes a tunable optical waveguide; a top layer, deposited on the semiconductor layer, which includes vias from an upper surface of the top layer to a bottom surface of the top layer which is proximate to the semiconductor layer; and electrodes (418, 612), deposited on the top layer and in the vias, which electrically couple to the semiconductor layer, wherein the electrodes are configured to reduce heat flow in a plane of the optical waveguide along a direction approximately perpendicular to an axis of the optical waveguide, wherein the electrodes are thermally coupled to the optical waveguide by multiple regions in the semiconductor layer which have a lower thermal conductivity than additional regions that are interdigited with the regions, wherein a given region has an axis that is approximately perpendicular to an axis of the optical waveguide in a plane of the semiconductor layer, wherein doping of the semiconductor layer in the given region exceeds doping of the semiconductor layer in the optical waveguide, the optical device being characterised in that the doping of the semiconductor layer in the optical waveguide defines a heater that facilitates thermal tuning of the optical waveguide, wherein the doping of the semiconductor layer in the optical waveguide alternates between a first type of region and a second type of region along the axis of the optical waveguide, and wherein the first type of region has a lower doping of the semiconductor layer than the second type of region, thereby reducing optical losses in the optical waveguide, and wherein the power consumption associated with thermal tuning of the waveguide is reduced by reducing thermal coupling from an external environment to the optical waveguide by said doping of the semiconductor layer in the given regions to said exceeding the doping of the semiconductor layer in the optical waveguide.