Low-loss arrayed-waveguide grating with high index regions at slab-to-array interface

A novel structure is proposed to reduce transition loss of an arrayed-waveg uide grating. The structure comprises high refractive-index regions formed at the core of slab waveguides in the vicinity of an array with ultraviolet UV) irradiation. The insertion loss was reduced by 3.0 dB after UV irradia tion. The minimum insertion loss became 2.1 dB, which includes fibre-to-chi p loss of similar to0.8 dB.