Low loss GaInNAs/GaAs gain waveguides with U-bend geometry for single-facet coupling in hybrid photonic integration

We report a low loss U-bend waveguide for realization of GaAs-based gain elements employed in hybrid photonic integration. This architecture allows us to position the input and output ports of the gain waveguide on the same facet and thus alleviates the geometrical constrains in hybrid integration, i.e., the need for precise alignment with silicon photonic waveguides on both ends of the III-V chip. As an exemplary demonstration, we report the loss and gain characteristics of GaInNAs/GaAs U-bend waveguides operating at 1.3 μm. In particular, we demonstrate a bending loss as low as 1.1 dB for an 83 μm bending radius. Efficient laser diode operation is also demonstrated.