Symmetric and asymmetric perturbations of the index of refraction in three-waveguide optical planar couplers

Abstract

A study is presented on the behavior of modes propagating in three coupled, dielectric slab waveguides with a perturbation to the index of refraction. In an electro-optic crystal, an applied electric field changes the index of refraction. A voltage applied to a given electrode configuration generates the electric field. For various initial excitations of the three guides, the optical power in each waveguide is calculated as a function of the voltage applied to the electrodes. The amount of optical power coupled from one outside waveguide to the other is calculated as a function of the applied voltage. The calculation is done for both asymmetric and symmetric perturbations to the index of refraction. For an initial excitation of the center waveguide, the optical power coupled to the two outside waveguides is calculated as a function of the applied voltage. It is calculated for both asymmetric and symmetric perturbations of the index of refraction. It is shown that, in general, the applied voltage that is necessary to transfer optical power from one outside waveguide to the other is lower for an asymmetric perturbation of the index of refraction. However, for transfer of optical power from the center waveguide to the two outside waveguides, the necessary applied voltage is lower for a symmetric perturbation.