Reduction in the diffraction loss of an arrayed-waveguide grating by use of an interference fringe between slab and arrayed waveguides

We propose a novel method for reducing the diffraction loss in an arrayed-waveguide grating. Our method introduces an interference fringe at the interface between slab and arrayed waveguides to relax the mode mismatch between them. We achieved a loss reduction of more than 0.42 dB with this method. Moreover, we provide an explanation of the loss-reduction mechanism of our method in terms of the point of imaging property of light.