Functional characteristics of optical waves in transverse acousto-optic waveguide and active coupler using SAW

Collinear waveguide-type A-O devices use collinear interaction with mode coupling based on Bragg condition between optical waves and SAW. Collinear A-O devices of waveguide-type show excellent performance for wavelength selective filtering with narrow bandwidths. However, interaction time in collinear A-O devices is several micro seconds for a few mm waveguide device length. A-O devices of optical waveguides using transverse A-O interaction where SAW propagates transversely to optical wave propagation direction, yield high speed functional characteristics because SAW propagation lengths are a few μm and interaction time is several nano seconds. In this paper, fundamental dynamic characteristics of transverse A-O interaction are studied. Refractive indexes induced by A-O effects of SAW are shown by sine functions in the transverse x direction. Wave field characteristics in inhomogeneous media of periodic structures for transverse directions are discussed by Mathieu functions. Dispersion characteristics of A-O eigen modes are studied for several wavelengths of optical waves and SAW. Mode coupling, modulation and switching in transverse A-O waveguide devices controlled by SAW are shown. Transverse A-O devices as couplers and separators are also discussed.