Grating-assisted InGaAsP/InP vertical codirectional coupler filter

Abstract
We report a novel wavelength selective coupler based upon grating‐assisted forward coupling between two, nonidentical, vertically stacked InGaAsP/InP waveguides. Using a 14.4 μm period to provide phase matching between the asynchronous waveguides, we achieve a filter bandwidth (full width at half maximum) of 65 Å and coupling efficiency of ∼65% with a device length of only 1.0 mm.