Research On The Optical Waveguide For Guided-wave Acousto-optic Modulator

High-speed guided-wave acousto-optic modulator can be used in optical communication, optical information processing, optical sensing and display field by using the control of SAW to light, such as modulation, switch and the control to the light propagation direction. And the inherent characteristic of acousto-optic devices, include high speed, broadband and working with multi-wavelength, can contribute to the development of fiber laser and optical communication field.In this dissertation, some theoretic and experimental research on the optical waveguide for high-speed guided-wave acousto-optic modulator has been done. The main contents of the paper are listed as follows:1. The background and development trend of high-speed guided-wave acousto-optic modulator have been reviewed. The status of optical waveguide in acousto-optic modulator is introduced.2. Based on the basic theories about guided-wave acousto-optic modulator, the device performance, such as the coupling efficiency between device and fiber, transmission loss of optical waveguide and diffraction efficiency, has been studied. The Ti-diffused optical waveguide and the proton-exchanged waveguide are introduced separately, and the performances of two waveguides are compared. The performance of 128°Y cut LiNbO3 waveguide has been analyzed.3. The optimum production parameters of Ti-diffused optical waveguide in acousto-optic modulator are designed. The insertion loss, mode selection of optical waveguide and the diffraction efficiency of acousto-optic modulator are researched. The influences of diffused depth, diffusion width-depth ratio and width of Ti strip on modulator performance are analyzed. The method used to design the diffused depth and width of Ti strip is obtained.4. The transmission loss of device caused by the waveguide structure is analyzed by use of OptiBPM software. The performance of the new type high-speed guided-wave acousto-optic modulator has been tested experimentally. The results show that the insertion loss of device is 6dB, polarization dependent loss is 1.9dB, the diffraction efficiency of 18% was obtained. According to results, the ideas for improving the modulator are provided.