Multifunctional grating couplers for bidirectional incoupling into planar waveguides

A novel type of grating coupler for coupling light from free space into a planar waveguide was designed. Compared to a conventional grating coupler which can couple light into one main direction, this new design enables simultaneous coupling into two opposite main directions. This leads to increased flexibility in integrated optics design and may also increase the overall coupling efficiency. We demonstrate experimentally devices for bidirectional incoupling with additional beam splitting and focusing capabilities.