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Research On Integrated Optic Gyro By Acousto-Optic Frequency Shift And Acousto-Optic Technique In Silica-on-Silicon Waveguide

Posted on:2013-12-30Degree:DoctorType:Dissertation
Country:ChinaCandidate:C ChenFull Text:PDF
GTID:1228330377455486Subject:Optics
Abstract/Summary:PDF Full Text Request
Integrated Optical Gyro (IOG) based on Sagnac effect is a type of inertial angular rate sensor and plays an important role in modern inertial navigation system. In this dissertation, a Resonator IOG (R-IOG) is studied theoretically and experimentally and the integrated-optic acousto-optic (AO) frequency shifting technology which is the critical technology in closed-loop control scheme for the monolithic IOG is emphatically investigated. The main research results are as follows:The open-loop and closed-loop detection schemes based on AO frequency shifting technology are projected using the reflection-type resonate The overall design, the signal testing and the system experiment of an AO frequency shifting IOG system is accomplished. The influence of spectral linewidth of laser on resonance characteristics in resonator and the IOG resolution limited by the photodetector shot noise are investigated theoretically. The spectral linewidth of laser, resonator parameters, optimal modulation frequency and modulation index are obtained. In order to achieve the resolution of1°/h, the necessary conditions for the AO frequency shifting technology are analyzed.The optical and acoustic field distributions are numerically calculated in silica waveguide (planar and rectangular) AO Bragg devices. Then the characteristics of AO interactions are studied in detail. For silica planar waveguide AO Bragg device, the influences of acoustic frequency, waveguide mode and thickness on overlap integral and the impacts of waveguide mode, acoustic power and acoustic aperture on diffraction efficiency are discussed. For silica rectangular waveguide AO Bragg device, the calculating model of AO overlap integral of rectangular waveguide is constructed and then the influences of acoustic frequency, waveguide thickness and width on overlap integral are calculated and analyzed.The basic equations and boundary conditions of Rayleigh SAW are derived theoretically for the layered IDT structure, and then the frequency diffusion curve and the electromechanical coupling coefficient are respectively calculated, furthermore, the frequency diffusion effects on center frequency and frequency width of the layered IDT structure are discussed. The higher the acoustic frequency, the more obvious the secondary electrode effect is, so the finite element model with electrodes is constructed to analyze the effects of electrode mass and reflection quantitatively.The overall structure of the integrated SAW-AOFS is designed optimizely. In order to make the driven acoustic frequency smaller and the AO interaction region larger, the tapered waveguide is used to widen the waveguide width of AO interaction region. With the intention of achieving high electromechanical coupling coefficient, choose the bottom-electrode layered IDT structure (ZnO/IDE/SiO2/Si) in which the designed optimal thicknesses of SiO2and ZnO are2A and0.4A, respectively. The diffraction characteristics are analyzed by finite difference beam propagation method, thus the optimal waveguide width of50μm of AO interaction region and the corresponding optimal acoustic aperture of2500μm are obtained. The resulting diffraction efficiency is85%and the required acoustic power is approximately0.28W.R-IOG experimental system based on AO frequency shifting technology is constructed and a lot of experimental research has been done:the resonance curve of the resonator is tested in which the free spectral range, the full width at half maximum and the fineness are3179.23MHz,42MHz and74.4, respectively; the two linear regions of the demodulation curves of the CW and CCW lightwaves overlap nicely indicating the good reciprocity of the resonator; the open-loop output signal of the gyro is tested at different angular rates, then the linear relationship between gyro signal and angular rate is fitted by the least square method, thus the scale factor and fitted null position are obtained that are5.1699mV/(°/s) and-2.2331mV, respectively; the testing peak to peak value of null drift is approximately3.87°/s in6or12seconds on condition that the gyro is kept stationary; finally, the frequency difference between the two AOFS is equivalent to the Sagnac frequency shift in which way the open-loop output signal of the gyro is also obtained.
Keywords/Search Tags:Resonator integrated optic gyro, SiO2waveguide, surface acousticwave, acousto-optic interaction, interdigital transducer, acousto-opticfrequency shifter
PDF Full Text Request
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