An optical device includes a semiconductor layer and a polysilicon coupler. The semiconductor layer includes at least one etched portion between first and second unetched portions. A first optical waveguide includes the first unetched portion and a first total internal reflection (TIR) boundary between the first unetched portion and the at least one etched portion. A second optical waveguide includes the second unetched portion and a second TIR boundary between the at least one unetched portion and the second etched portion. A polysilicon coupler at least partially overlaps the etched portion of the semiconductor layer. The polysilicon coupler optically couples the first optical waveguide and the second optical waveguide, wherein light can flow from the first optical waveguide via the polysilicon coupler portion to the second optical waveguide.