Acousto-Optic Modulator Driven by Surface Acoustic Waves

In this paper, an introduction to the design, fabrication, evaluation, and application of acousto-optic modulators using the Bragg diraction of an optical guided wave in a channel optical waveguide due to a surface acoustic wave is provided.First, the surface acoustic wave mode dependence in the acousto-optic Bragg diraction was discussed by considering the surface acoustic wave power required for the maximum diraction P100 calculated using coupled mode theory and the measured P100 in Ti-diused planar optical waveguides fabricated on LiNbO3 substrates.Next, performances of several devices that the author and the coworkers developed are reviewed.These include a waveguide-type acousto-optic modulator using a tapered crossed-channel proton-exchanged optical waveguide on a 128 • -rotated Y -cut LiNbO3 substrate for an optical wavelength of 1.55 µm, a monolithically integrated tandem acousto-optic modulator in which several waveguide-type acousto-optic modulators are connected in tandem on the same substrate, and a waveguide-type acousto-optic modulator in which laser lights of the three primary colors, red, green, and blue, can be modulated by the same modulator at the same driving frequency.