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Research On Temperature And Magnetic Field Sensing Characteristics In Optical Ring Resonators

Posted on:2017-03-21Degree:DoctorType:Dissertation
Country:ChinaCandidate:C Q YuFull Text:PDF
GTID:1108330503469746Subject:Physical Electronics
Abstract/Summary:PDF Full Text Request
Ring resonators have attracted great interest from researchers due to their advantages of high compactness, high resolution and ease of fabrication. They can be used to realize many optical devices, such as optical filter, optical sensor, optical delay line, optical switch and so on. Thermal sensing and magnetic field sensing are two typical applications. The temperature and magnetic field sensing properties of optical ring resonators are investigated in this thesis, the main contents are as follows:Firstly, the research progress on optical and sensing properties of several kinds of resonators are reviewed, including waveguide ring resonators, resonator coupled MachZehnder(M-Z) interferometers and whispering gallery mode(WGM) resonators. Then the research advances on ring resonator based thermal and magnetic field sensors are displayed. On the basis of these studies, we summarize the research that needs to be further supplemented and improved. Then, they were chosen to be the main contents of this thesis.Secondly, transfer matrix theory was displayed by demonstrating the transmission properties of single ring resonator and resonator coupled M-Z interferometer structure.Steps to investigate the sensing properties of those structures are also described. Additionally, we display the method to calculate resonator’s optical and mechanical mode by simulating and evaluating the resonator’s modes. Meanwhile, simplified theory is proposed to demonstrate the magnetic field sensing properties of the WGM resonators.Accordingly, sensitivities of two resonators are determined. To choose appropriate experimental parameters, the angles for prism-resonator coupling system are calculated, and the positions of optical components are therefore fixed. Pound-Drever-Hall(PDH) locking theory is displayed and suitable modulation frequency is selected.Thirdly, the add-drop ring resonator(ADRR) coupled M-Z interferometer structure is studied. First of all, the transmittance and dispersion properties of two output ports in the ADRR are theoretically analyzed. And then those properties are utilized to enhance the sensitivity of interferometer. Through calculating dispersion sensitivity of the ADRR coupled M-Z interferometer, the way to achieve best sensitivity at different coupling regions is determined. Furthermore, a special parameter is chosen to conduct the experiments and those results agree well with theoretical results. At last, temperature sensitivities of both traditional interferometer and ADRR enhanced M-Z interferometer are calculated. The sensitivity comparison is made to reveal the significance of dispersion sensitivity.Fourthly, the single ring nested resonator(SRNR) coupled M-Z interferometer structure is designed to obtain asymmetric Fano resonance. Theoretical analysis is performed to illustrate two output ports’ transmissions for different phase biases on the reference arm, and asymmetric resonances with opposite intensity variation in two output ports can be acquired for chosen parameters. Furthermore, the temperature sensing properties of this structure are demonstrated based on those Fano resonances. And the effects of structure parameters on temperature sensitivity are fully discussed.Fifthly, the optical and magnetic field sensing properties are experimentally studied for two WGM resonators. The frequencies of mechanical modes are determined by COMSOL software so that appropriate resonator’s dimensions are chosen to enhance the magnetic field response at low frequencies. Cavity ring down method and sweeping method are utilized to measure optical quality factors of two resonators, respectively.PDH locking system is built to lock laser frequency to the resonance frequency. On this basis, magnetic field sensing properties are tested for the resonator and sensitivities at low frequencies are obtained. Through optimizing the relative position of calcium fluoride(Ca F2) optical resonator to magnetostrictive material and the height of magnetostrictive material, WGM resonator’s mechanical mode can be improved. Therefore, the structure parameters of improved resonator are determined. Furthermore, the magnetic field sensing properties are tested. The results show that both sensitivity and detection frequency range are enhanced compare to the previous resonator. Both two macro resonators have better sensitivities than the micro ones and direct measurements instead of utilizing material’s nonlinear properties can be made to reduce difficulties of measuring process. The research on those resonators lays the foundation for magnetic resonance imaging studies.Research in this thesis provides a more stable way to enhance the sensitivity of the M-Z interferometer. Thus more choices are made for sensors based on interferometer.Higher sensitivities of resonators based magnetometers are achieved at low frequencies.Therefore, resonator based sensors become more valuably.
Keywords/Search Tags:resonator, Mach-Zehnder interferometer, temperature sensing, magnetometer, whispering gallery mode
PDF Full Text Request
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