Electro-optically induced tilted phase gratings in waveguides

A new design for an electro-optically induced tilted phase grating inside a waveguide is proposed. The electric field and the refractive-index distrib ution induced inside a waveguide by voltage applied to two systems of inter digitated electrodes that are shifted with respect to each other are calcul ated rigorously on the basis of an original technique. The model accounts f or the arbitrary electrode shift distance d (0 less than or equal to d less than or equal to 2l), where l is the electrode spatial period. It is shown that the proper choice of the shift can minimize the structure's capacitan ce and consequently its time response. The refractive-index distributions a re calculated for various schemes for application of electric potential and electrode position that demonstrate the possibility of switching the direc tion of the grating wave vector. It is shown how the concept can be use to build electro-optically controllable transmissive (long-period) and reflect ive (short-period) tilted gratings and couplers in both multilayered (trans verse) and planar (lateral) configurations. (C) 2001 Optical Society of Ame rica.