Abstract: An optical switch of the switched directional coupler type is provided with an adjustable cross-over state as well as an adjustable straight-through state, in order to provide reduced crosstalk in the cross-over state, for example, when the switches are used in an optical switching system. The improved switch is based on asynchronous or phase-mismatched coupling between two parallel optical strip guides driven by electrodes to which the voltage is applied. In order to use phase-mismatched coupling instead of phase-matched coupling for the cross-over state, in order thereby to obtain electrical adjustability of that state, the driving electrodes are split into two or more sequential sections, thereby defining two sequential coupling sections of the parallel optical strip guides. The cross-over coupling is then achieved by switching the mismatch conditions so that at the point of partial coupling the "nonoriginating" guide appears to the coupled optical waves to be the "originating" guide.

Abstract: Acoustic waveguides, acoustic filters and acoustic reflectors are based upon the discovery of increased acoustic wave velocity in materials such as lithium niobate and lithium tantalate into which a metal such as titanium, nickel or chromium has been diffused. Velocity increases larger than 1 percent have been obtained; and negligible effect on acoustic loss is incurred thereby. The technique and the resulting devices result in a simpler structure than provided by the metallic strips or the ion beam etched surface regions of prior acoustic devices in which velocity perturbations of comparable magnitude have been desired.