Study On The Guided-wave Acousto-optic Modulator Of Q-switched All-fiber Laser

High-speed guided-wave acousto-optic modulator will be one of the best switching devices of the Q-switched all-fiber laser for their high speed, compact size, low insertion loss, excellent design flexibility, high mechanical stability, low driver power requirement and good integration. At the same time, it can be used in the high -speed optical communications.The paper is mainly focused on the research about the high-speed guided-wave acousto-optic modulator. And, the paper does the experimental research about the Yb³⁺- doped double-clad fiber laser.The main emphasis and innovation of the paper are as follows:1. The design theory of the waveguide acousto-optic modulator is presented. The research is investigated about the design parameters of the acousto-optic devices, the overlap integral, the acoustic waveguide, the optical waveguide, the whole structure design and the coupling between the fiber and the waveguide. A novel high-speed guided-wave acousto-optic modulator is designed and fabricated. The switching speed is within 70ns, which takes the lead in the world.2. The first analysis is presented, based on the diffraction of surface acoustic waves, of the relationship between the Bragg bandwidth and the diffraction efficiency in guided acousto-optic interactions. It has been found that the Bragg band width is not always inversely proportional to the acoustic aperture. It is possible to simultaneously get high diffraction efficiencies and large bandwidths for guided acousto-optic devices.3. A novel method is proposed to analyze optical waveguide, which we call the improved ray approximation method. The method is developed based on the ray- approximation method and the effective index method to design the single-mode 3-D optical waveguide. The method is simple and effective compared with other methods.4. A new method is provided to the taper waveguide. The method can be used to analyze and design the taper waveguide with the different form functions. The method is simple and practical compared with other methods.5. A detailed analysis is presented, about the coupling loss dependence on the waveguide mode eccentricity and symmetry between single-mode fibers and waveguides. A new conclusion is obtained that more symmetric waveguide mode leads to lower coupling loss, but less eccentric waveguide mode does not always mean low coupling loss, which depends on the waveguide mode depth.6. The experimental research of the Yb³⁺-doped double-clad fiber lasers. We do the experimental research about the CW Yb³⁺-doped double-clad fiber lasers, Q- switched Yb³⁺-doped double-clad fiber lasers, the active and passive Q-switched Yb³⁺ -doped double-clad fiber lasers and self-Q-switched Yb³⁺-doped double-clad fiber lasers, respectively.