A leaky-mode directional coupler for waveguide grating lens

A leaky-mode directional coupler, based on a multi-layered slab waveguide, was designed to obtain an output beam with single radiation angle emerging from the waveguide for the sake of highly efficient focusing waveguide grating coupler (FWGC). An inner cladding in the waveguide was adopted to facilitate the effective power leakage of the propagating leaky mode. The ratio of the output to the input beam that was analyzed using the beam propagation method was estimated to be 99% for 1 mm coupler length. Eventually, we obtained a Gaussian-like intensity profile of the output beam.