SiO2波导布拉格器件中声表面波及声光相互作用分析

针对SiO2光波导声光布拉格器件,计算了SiO2非对称平板波导TE模式的横向场分布;给出了SiO2/ZnO/Air层状介质结构的性能方程、运动方程和麦克斯韦方程,推导出这种层状结构的特征方程,并结合所满足的边界条件,得到了各层介质的位移及电磁场分布;计算了声表面波所引起的光学相对介质隔离率张量的变化,最后讨论了声光衍射效率和光场与声场的重叠积分、声功率、声频率、声孔径和光波导参数之间的关系。结果表明,在低频范围内光场与声表面波场重叠良好;低阶模的重叠积分始终大于高阶模重叠积分,最低阶模与声表面波相互作用最强,所需声功率最小;当声功率一定时,增加声孔径可以提高衍射效率。

Analysis on Acoustic Surface Wave and Acousto-Optic Interactions in Silica Waveguide Bragg Devices

The properties of silica waveguide Bragg devices are analyzed. The field distribution of the transverse electric (TE) mode is given for the silica asymmetric slab waveguide. The characteristic equations for SiO2/ZnO/Air multilayered structures are obtained after writing the equations of state, equations of motion and Maxwell′s equations, then the displacement and the electromagnetic field in each region are found with the appropriate boundary conditions. The change of the relative dielectric permeability tensor by the acoustic surface wave is calculated. The relationships among acousto-optic diffraction efficiency, overlap integral between the optical and acoustic fields, acoustic power, acoustic frequency, acoustic aperture and waveguide parameters are discussed. The results show that there is a good overlap of the optical and surface acoustic wave fields in the low surface acoustic wave frequency range; the overlap integral of the lower-order mode is always larger than that of the higher-order; the lowest-order waveguide mode exhibits the strongest acousto-optic interaction and requires the lowest acoustic power; at the same acoustic power, increasing acoustic aperture results in an increase in the diffraction efficiency.