Planar beam-steered acousto-optic light deflectors

A theoretical and experimental study has been made of planar acousto-optic light deflectors with particular emphasis on acoustic beam steering as a means of improving device performance. The theoretical model takes into account the electrical drive characteristics of beam-steered interdigital surface acoustic wave (SAW) transducers, anisotropic diffraction of acoustic waves and the rigorous theory of the interaction between guided optical waves and high frequency surface acoustic waves. The experiments were carried out on nickel indiffused waveguides on Y-cut LiNbO₃ substrates. A four-section, three finger pair transducer array was used to launch acoustic waves with propagation direction centered at 21.8° from the Z axis. A center frequency of 200 MHz was chosen as a compromise between high acousto-optic bandwidth and ease of fabrication. The deflector had a bandwidth of more than 60 MHz and gave 44 resolvable spots with an optical wave 2.5 mm wide. The observed frequency response of the diffraction efficiency was in excellent agreement with the theory. It was concluded that beam steering is an advantageous technique for devices requiring large bandwidth and high diffraction efficiency.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat