Efficient modeling method for emitting focusing grating coupler based on complex mode matching and effective index method.

In this paper, an efficient modeling method for a photonics-focusing grating coupler is proposed and studied. The focusing grating coupler can be divided into two parts: the cylindrical coordinate slab waveguide and the Cartesian coordinate slab waveguide. Using the cylindrical slab modes and the two-dimensional complex mode-matching method, we can obtain the efficient compact model for the focusing grating coupler. This model reduces the three-dimensional structure into a two-dimensional structure by using the effective index method to reduce the computation time as well as the computational resources. The simulation result, which is dependent on the finite-difference time-domain method, demonstrates the accuracy of the advanced compact model. This model can also be integrated into the circuit simulation.