Optical directional couples with variable spacing

Abstract

The directional coupler switch provides for the modulation of light in a waveguide by the transfer of the guided light to a similar adjacent guide. Complete power transfer occurs when the phase velocities in the two guides are perfectly synchronized and the interaction length is precisely the coupling length, Lc. this stringent tolerance is overcome by using a technique called stepped ?ß reversal [1][2]. In GaAs, Leonburger et al [3] reported up to 99.7% cross-over using a metal-gap structure with two electrode pairs. Directional couplers with variable spacing [4] are directional coupler structures in which the channel separation varies the sample length. For telecommunication applications the device can be made to function as alternative to Y function [4] for variable power splitters and switches. The increased guide spacing gives benefit such as ease of fibre coupling and possible integration with other components.