Configurations for an optical system with phase shifting elements are disclosed. The optical system may include a first waveguide that provides light to a second waveguide, which may be a slab waveguide. A phase shifting element may be disposed on the slab waveguide and may be heated to induce a temperature change in the slab waveguide. By increasing the temperature of the propagation region of the slab waveguide, the index of refraction of the propagation region of the slab waveguide may shift, thus causing the index of refraction of light propagating through the propagation region to shift, thus shifting the phase of the light. This may result in an optical component capable of phase shifting light for reducing coherent noise while being energy efficient and maintaining a small form factor.