發(fā)布時間：2019-01-12 07:45

【摘要】：聲光器件由于其體積小、損耗小、易于實現(xiàn)動態(tài)調(diào)制等優(yōu)點,被廣泛應(yīng)用于光纖通信系統(tǒng)中。采用磁控濺射的方法,實驗在傾斜的YAG晶體上蒸鍍了基于ZnO薄膜壓電特性的體聲波超聲換能器,并通過將體聲波機械耦合進入光纖中,利用聲光調(diào)制實現(xiàn)了傾斜的光纖光柵結(jié)構(gòu),在研究聲光相互作用的基礎(chǔ)上,分析了體聲波傾斜光纖光柵的特性。通過對體聲波在一般聲學層的傳輸、在介質(zhì)界面的入射以及晶體的彈性性質(zhì)進行分析,為光纖中體聲波的傳輸和傾斜光纖光柵結(jié)構(gòu)的形成作鋪墊。基于聲光效應(yīng),研究了布拉格衍射效率以及聲光耦合理論,對體聲波換能器的結(jié)構(gòu)設(shè)計提出要求。分析了基于聲光調(diào)制的傾斜光纖光柵的結(jié)構(gòu),對傾斜角度和高階模式對傾斜光纖光柵的模式耦合系數(shù)進行模擬分析,為體聲波傾斜光纖光柵的傾斜角度的選擇和測試提供理論指導。根據(jù)材料的壓電特性,設(shè)計了夾心式結(jié)構(gòu)的體聲波超聲換能器。采用磁控濺射的方式,在傾斜的YAG晶體上依次蒸鍍了Ag底電極、ZnO壓電層、Ag頂電極,并通過臺階儀檢測了薄膜的生長質(zhì)量。通過分析換能器的Mason等效電路模型,計算了換能器的最佳匹配阻抗,實驗測試體聲波換能器的諧頻特性和雙面結(jié)構(gòu)的電聲-聲電轉(zhuǎn)換特性,證實了基于Zn O的體聲波換能器具有較好的電聲轉(zhuǎn)換特性。通過將去除涂敷層的光纖固定于YAG晶體的凹槽中,使體聲波斜入射耦合進入光纖中,形成基于聲光調(diào)制的傾斜光纖光柵。根據(jù)對傾斜光纖光柵的衍射與模式耦合理論,實驗測試了不同傾角和不同超聲功率下體聲波傾斜光纖光柵的透射損耗并設(shè)計實驗在光纖外探測接收了光纖逸出光信號。實驗結(jié)果表明,應(yīng)用基于聲光調(diào)制的傾斜光纖光柵能夠應(yīng)用于光纖通信系統(tǒng)的選擇性濾波和實時監(jiān)測。
[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.
【學位授予單位】：華中科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TN253

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