Acousto‐optic modulation at gHz frequencies using integrated optic technology

Abstract

Phase modulation of light guided in a thin film optical waveguide is produced by bulk acoustic waves propagating through the waveguide perpendicular to the optical wave. The principal advantages of this interaction for high frequency modulation are: (1) A wide choice of waveguide materials may be used and (2) Acoustic propagation takes place through a thin waveguide, thus attenuation does not limit performance until very high frequencies are reached. We describe the acoustic effect then show how it may be used to construct an integrated optic device which converts the phase modulation to amplitude modulation. This device integrates an interferometer structure with the thin film acoustic transducer on a silicon substrate. We have built the device and tested it.