Optimum overlap of electric and optical fields in semiconductor waveguide devices

Abstract
The effect of an applied field on the propagation constant of a mode in a semiconductor slab waveguide is examined theoretically. A figure of merit defined as the change of propagation constant with voltage is related to the relative widths of the electrical and optical fields. It is shown that the figure of merit is maximized when the region over which the electric field is applied is minimized, rather than when the two fields have similar profiles. The constraint of electrical breakdown is also discussed with respect to the maximum change in propagation constant.