Optical Tunable Switched Directional Couplers Consisting of Two Thin-Film Waveguides Using Surface Acoustic Waves

Abstract

Control methods of the fraction of optical power transferred between two waveguides using a collinear acousto-optic interaction is theoretically investigated. The effect of a surface acoustic wave (a SAW) on the mode coupling between the fundamental even and odd eigenmodes of a directional coupler system is analysed and two control methods of optical power transferred are proposed. The required SAW powers of the switched couplers using SAW's and thin-film acousto-optic devices such as optical beam deflectors and optical mode convertors are comparable to one another. The efficiently controllable bandwidth of the optical wavelength λ0 are approximately 100 Å and 40 Å at λ0≃0.63 µm for the symmetric and asymmetric switched couplers with the SAW wavelength of 25 µm and the interaction length of 8 mm. The optical center wavelength of the controllable range can be tuned by the SAW frequency.