In integrated optics circuits, grating couplers are used to insert or extract the optical energy. In this thesis, the grating coupler is treated as a perturbed waveguide interface. Because of the imperfect interface, one guided mode is converted to a radiation mode. The coupling efficiency is calculated for the conversion of the guided mode to a substrate radiation mode and computer programs are developed to optimize the coupling efficiency. Computer languages FORTRAN and MATHEMATICA are used to calculate the coupling efficiency. |