Optical Switching

5Acousto‐Optic Switches

Sudipta Ghosh¹, Chandan Kumar Sarkar¹, and Manash Chanda²

¹ Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata, West Bengal, India

² Department of Electronics and Communication Engineering, Meghnad Saha Institute of Technology, Kolkata, West Bengal, India

5.1 Introduction

Acoustic‐optic switches are made based on the principles of diffraction of light through a propagating medium having periodical variation of refractive index. This index variation could formulate moving index grating or standing index grating, through the medium, caused by moving or standing acoustic wave respectively. The period and degree of modulation of index grating can be tuned by the frequency and amplitude of the acoustic wave through a transducer, controlled by electronic signals. A radio frequency (RF) electric field is applied across the electrodes of an acoustic transducer to generate an acoustic wave by piezoelectric effect. This acoustic wave induces a cyclical strain in the desired medium either on its surface to create surface acoustic wave (SAW) or in the bulk of that medium to create a bulk acoustic wave. Optical switches, couplers, frequency shifters, beam deflectors, and modulators have widely emerged as applications of acoustic‐optic devices in recent times.

Compound semiconductors using III‐V materials [1], like indium gallium arsenide or gallium phosphide, are desired candidates to construct acousto‐optic devices as these ...