Design of tapered SAW waveguide for wavelength‐selective optical switches using weighted acoustooptic interaction

Optical wavelength‐selectivity in optical switches using waveguide‐type collinear acoustooptic interaction is studied from the viewpoint of sidelobe suppression. It is found that the sidelobe level can be reduced from −9.3 dB to −20 dB by weighting the coupling coefficient over the interaction region. A method to realize the sidelobe suppression by means of modifying the surface acoustic wave (SAW) waveguide is proposed and theoretically analyzed to design the SAW waveguide. A sidelobe suppression at −20 dB is realized with a SAW waveguide of a dense‐flint glass strip whose width and thickness are varied accordingly in the ranges of 700 to 26 µm, and 0.4 to 1.0 µm, respectively, on a Y‐X LiNbO 3 substrate. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(1): 36–46, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20251