An optical device including a waveguide grating is disclosed. The optical device may be used as an optical cavity for a laser device, for instance, of an integrated laser device for light detection and ranging (Lidar) applications. In one aspect, the optical device includes a waveguide grating for guiding light, a heating layer provided beneath or above the waveguide grating, and two or more contacts for passing a current through the heating layer, to generate heat in the heating layer. The heating layer is thermally coupled to the waveguide grating and is optically decoupled from the waveguide grating.