Integrated Bragg Grating Filter With Reflection Light Dropped via Two Mode Conversions

We propose an integrated Bragg grating (BG) filter with reflection light dropped in a silicon-on-insulator platform. Most of the light reflected by the BG is coupled to a branch waveguide, while some residual reflected light radiates rather than propagating back to the input port. The structure is mainly composed of an antisymmetric BG and an asymmetric directional coupler. Two mode conversions between the fundamental transverse electric mode and the first higher order transverse electric mode are applied to control the on-chip light route. The proposed structure is investigated via simulation and experiment. Two integrated BGs-a π phase-shifted grating and a chirped grating-are successfully fabricated. The proposed structure is expected to aid practical applications of BGs to various photonic integrated devices.