基于声光调制的倾斜光纤光栅的研制与特性分析

发布时间：2019-01-12 07:45

【摘要】：声光器件由于其体积小、损耗小、易于实现动态调制等优点,被广泛应用于光纤通信系统中。采用磁控溅射的方法,实验在倾斜的YAG晶体上蒸镀了基于ZnO薄膜压电特性的体声波超声换能器,并通过将体声波机械耦合进入光纤中,利用声光调制实现了倾斜的光纤光栅结构,在研究声光相互作用的基础上,分析了体声波倾斜光纤光栅的特性。通过对体声波在一般声学层的传输、在介质界面的入射以及晶体的弹性性质进行分析,为光纤中体声波的传输和倾斜光纤光栅结构的形成作铺垫。基于声光效应,研究了布拉格衍射效率以及声光耦合理论,对体声波换能器的结构设计提出要求。分析了基于声光调制的倾斜光纤光栅的结构,对倾斜角度和高阶模式对倾斜光纤光栅的模式耦合系数进行模拟分析,为体声波倾斜光纤光栅的倾斜角度的选择和测试提供理论指导。根据材料的压电特性,设计了夹心式结构的体声波超声换能器。采用磁控溅射的方式,在倾斜的YAG晶体上依次蒸镀了Ag底电极、ZnO压电层、Ag顶电极,并通过台阶仪检测了薄膜的生长质量。通过分析换能器的Mason等效电路模型,计算了换能器的最佳匹配阻抗,实验测试体声波换能器的谐频特性和双面结构的电声-声电转换特性,证实了基于Zn O的体声波换能器具有较好的电声转换特性。通过将去除涂敷层的光纤固定于YAG晶体的凹槽中,使体声波斜入射耦合进入光纤中,形成基于声光调制的倾斜光纤光栅。根据对倾斜光纤光栅的衍射与模式耦合理论,实验测试了不同倾角和不同超声功率下体声波倾斜光纤光栅的透射损耗并设计实验在光纤外探测接收了光纤逸出光信号。实验结果表明,应用基于声光调制的倾斜光纤光栅能够应用于光纤通信系统的选择性滤波和实时监测。
[Abstract]:Acoustooptic devices are widely used in optical fiber communication systems because of their small size, small loss and easy to realize dynamic modulation. An experimental bulk acoustic ultrasonic transducer based on the piezoelectric characteristics of ZnO thin films was deposited on the tilted YAG crystal by magnetron sputtering, and the bulk acoustic wave was mechanically coupled into the fiber. The structure of tilted fiber grating is realized by acousto-optic modulation. Based on the study of acousto-optic interaction, the characteristics of bulk acoustic wave tilted fiber grating are analyzed. By analyzing the transmission of bulk acoustic wave in the general acoustic layer, the incidence of the dielectric interface and the elastic properties of the crystal, the transmission of bulk acoustic wave in the fiber and the formation of the structure of the tilted fiber grating are prepared. Based on acousto-optic effect, Bragg diffraction efficiency and acousto-optic coupling theory are studied. The structure of tilted fiber grating based on acousto-optic modulation is analyzed. It provides theoretical guidance for the selection and measurement of tilt angle of bulk acoustic fiber grating. Based on the piezoelectric characteristics of the material, a bulk acoustic ultrasonic transducer with sandwich structure is designed. The Ag bottom electrode, ZnO piezoelectric layer and Ag top electrode were deposited on the tilted YAG crystal by magnetron sputtering in turn. The growth quality of the films was measured by a step meter. By analyzing the Mason equivalent circuit model of the transducer, the optimum matching impedance of the transducer, the harmonic and frequency characteristics of the bulk acoustic transducer and the electroacoustic to acoustic electrical conversion characteristics of the dual structure are calculated. It is proved that the bulk acoustic transducer based on Zn O has better electroacoustic conversion characteristics. An inclined fiber grating based on acousto-optic modulation is formed by fixing the coated fiber in the grooves of the YAG crystal so that the bulk acoustic wave is diagonally incident into the fiber. According to the theory of diffraction and mode coupling to tilted fiber grating, the transmission loss of bulk acoustic fiber grating with different inclination angle and different ultrasonic power is measured experimentally, and the optical escape signal of the fiber is detected and received by the experiment outside the fiber. The experimental results show that the tilted fiber grating based on acousto-optic modulation can be applied to the selective filtering and real-time monitoring of optical fiber communication systems.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN253

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