Resonant excitation analysis of waveguide grating couplers

We present a new analysis of waveguide grating couplers that is based on the resonant excitation of the structure by an external plane wave. We are able to calculate all of the important grating coupler parameters for beam coupling efficiency calculations: the coupling angle, coupling coefficient and branching ratio. We compare our method with a perturbation theory approach and with the rigorous modal solution of periodic waveguides.