Guided-Wave Acousto-Optic Interaction in a ZnO Thin Film on a Nonpiezoelectric Substrate

Abstract

The possibility of Surface Acousto-Optic (SAO) devices such as deflectors, modulators, and mode converters playing an important role in integrated optics led to the extensive study of the Bragg diffraction of Guided Optical Waves (GOW) by Surface Acoustic Waves (SAW). Since Kuhn et al. [6.1] first demonstrated SAW-GOW deflectors and modulators, numerous experiments have been carried out on various thin-film configurations. An extensive list of references on prior works has been provided in [6.2] and Chap. 5. All the experiments performed thus far are classified by device structure into two categories, i.e., if the substrate on which the optical waveguide is constructed is a piezoelectric material, it is in the first category, while if it is a nonpiezoelectric material, it is in the second category. Since many kinds of devices in integrated optics must be constructed on nonpiezoelectric substrates, it is desirable to construct SAO devices with the second category. With this category a SAW can be launched by means of a piezoelectric thin film such as ZnO deposited on the substrate. ZnO, a memeber of the hexagonal wurtzite class, has a low dielectric constant and a high electromechanical coupling factor making it a useful material for SAW device technology. Moreover, ZnO is an interesting material for GOW because it is transparent from 0.4 to 2 µm and should be an optically low-loss material.