Abstract: In one aspect, an integrated photonic device is disclosed, which comprises a waveguide through which radiation having one or more wavelengths within a wavelength band can propagate, a phase shifter optically coupled to said waveguide. The phase shifter comprises a heat-actuable phase change material (PCM) optically coupled to the waveguide, and a heater having a layer of a two-dimensional material in thermal communication with the PCM and configured to receive a reset voltage pulse for causing heating of the graphene layer followed by cooling thereof, wherein the thermal communication between the heated graphene layer and the PCM causes at least a portion of the PCM to undergo a phase transition from a crystalline state to an amorphous state, thereby causing a change in a refractive index of the PCM and a resultant phase shift in the radiation propagating through the waveguide.