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 distribution induced inside a waveguide by voltage applied to two systems of interdigitated electrodes that are shifted with respect to each other are calculated rigorously on the basis of an original technique. The model accounts for 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 capacitance and consequently its time response. The refractive-index distributions are calculated for various schemes for application of electric potential and electrode position that demonstrate the possibility of switching the direction of the grating wave vector. It is shown how the concept can be use to build electro-optically controllable transmissive (long-period) and reflective (short-period) tilted gratings and couplers in both multilayered (transverse) and planar (lateral) configurations. (C) 2001 Optical Society of America.