Enhanced Coupling Strength Gratings for Couplers in III–V Compound Dielectric Waveguides

The use of a thin, low-index liner layer over a surface grating covered by a high-index cover layer in a III-V alloy waveguide significantly improves the coupling efficiency of grating couplers, and therefore, reduces the length of such couplers by an order of magnitude. The same low-index liner and high-index cover layer can also reduce losses between transition sections of photonic integrated circuits or between a laser region and a distributed Bragg reflector or grating coupler region.