Research On Integrated Guided-wave Acousto-optic Modulator Based On Surface Acoustic Wave

Integrated guided-wave acousto-optic modulator based on surface acoustic wave(SAW) is expected to be used in fiber lasers as Q-switch for its fast switching time and high diffraction efficiency. And the inherent characteristic of the device, including good integration, small size, low drive power, broadband, multi-wavelength operation, can contribute to the development of optical communication and laser display field.In this dissertation, the overall structure and output characteristics of modulator are studied theoretically and experimentally. The main contents of the paper are listed as follows:1.The background, research status, trends and research significance of SAW-based guided-wave acousto-optic modulator are introduced.2.Double-tapered waveguides with different transition boundary are analyzed by using OptiBPM software. Three reference structures for guided-wave acousto-optic modulator are proposed.The result shows that the diffraction efficiency can be improved 7% to 8% and the structure loss can be reduced 0.2 to 0.3dB.3.Impedance mismatch during the process of loading high-frequency signals has been studied. Several L-shaped matching circuits for achieving impedance matching are designed. Their voltage transfer coefficient is calculated and compared through the transfer matrix method. And the optimum L-shaped matching circuit has been given.4.Using an improved light approximation method, the single-mode working condition of titanium diffusion optical waveguides has been analyzed. The relationship between initial production conditions of different-cut titanium diffusion lithium niobate waveguides and the fiber-waveguide coupling loss is discussed through the above conclusions and the approximate solution based on the effective refractive index method which is proposed by E. Stake, G. P. Bava et al.5.Using the fourth-order Runge-Kutta method, coupled mode equations based on the simplified multiple plane-wave scattering theory derived by Chatterjee, Chee et al are solved. Distribution of diffracted light at all levels in the same diffraction device, which is working at different wavelengths, has been simulated by Matlab software. The results provide a preliminary theoretical basis for the development of multi-wavelength broadband acoustic waveguide modulator.