Abstract

The digital optical switch recently reported by Silberberg, et. al.¹ has reactivated interest in devices that achieve switching via the evolution of normal mode shape in a waveguide branch, rather than the interference of normal modes in a directional coupler or a Mach-Zehnder interferometer. The active element of the digital switch, an active waveguide branch, was demonstrated by Burns, et. al.² in a three port configuration. Our interest here is to develop an expression for the voltage-length product of an active waveguide branch, so that performance comparisons between the modal evolution devices and modal interference devices can be made. To do this we will utilize the analytic solution for normal mode coupling in specifically shaped waveguide branches³. This approach has two advantages: 1) It is an analytic solution and does not require computer analysis, and 2) the shaped branch assumed represents the optimum shape in that it is a minimum length structure for a given amount of mode conversion, i.e. it is the best you can do for a minimum voltage-length product. Finally we will compare the calculated V-L product with experiment.

© 1989 Optical Society of America