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Novel Microring Resonators And Sensing Properties

Posted on:2016-02-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:X LiFull Text:PDF
GTID:1108330503469727Subject:Control Science and Engineering
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Sensing technology is a essential component of automatic control technology, information technology and automatic detection technology. Optical sensing technology which make use of optical waveguide as a media and optica wavel as a carrier get a opportunity on account of the traditional electronic sensors are usually large and can not work under harsh environments like electromagnetic interference. The concept of "system on a chip" is presented to meet the requirements for sensors’ miniaturization, integration and so on. The micro-nano optical sensors, which use evanescent field on optical waveguide surface to perceive changes in the external environment, have become a research focus, especially the micro-ring resonator with high Q, low-cost in the sensing area. The research of micro-ring resonator in the area of temperature, refractive index, acceleration, biochemical sensing field has been widely reported. Nevertheless, the problem of how to enhance the sensitivity and measurement range of the micro-ring sensor remains unsolved. Theoretical analysis and experiment are presented in this thesis to study these two key issues. The main research contents are organized as follows:We propose a micro-ring resonator structure having phase modulator with double inputs to replace the traditional model, whose limitations include the untunable wavelength, narrow free spectral range and inflexibility of architectures. The mathematical model of micro-ring is derived and the transmission function of micro-ring with double inputs is obtained by transfer matrix method. On this basis, the spectral property is analyzed and the critical coupling condition is calculated. The relation between phase shift of two input ports and resonance characteristics of micro-ring demonstrated that wider FSR and tunablity of resonance wavelength in some range can be achieved by contrast of single input micro-ring with the counterpart of identical parameters. All these lay a solid foundation for the research of wider measurement range of micro-ring.The transmission characteristics of U-type feedback micro-ring resonator in the weak coupling and strong coupling conditions was researched so as to improve the measurement range of micro-ring sensor further. On this basis, The transmission characteristics of U-type feedback micro-ring resonator are analyzed when overall structure being heated and part of the structure being heated. The results demonstrate that regular spectral shift occurred as the feedback waveguide length is integral multiples to perimeter of the micro-ring and both of them are heated. In addition, the pseudo-norm was absent and a higher measurement range of the temperature sensor was reached.An experiment platform was made to produce micro/nano optical fiber and optical fiber micro-ring resonator. Optical micro/nano fiber meeting the experimental conditions has been manufactured successfully, and a single micro-ring with different radius of the optical fiber was also produced. Optical fiber feedback U-type micro ring resonator was made on this basis. This structure is suit for designing micro-ring resonator with large FSR. At the same time, a track-type micro-ring resonator was made through the improvement of coupling regional structure. This micro-ring resonator is more stable compared with Knot-type micro-ring resonator using the same structural parameters. By adjusting the coupling region length can make the system closer to the critical coupling state and derive a resonate spectrum with high Q and extinction ratio. Greater detection sensitivity was obtained when using intensity detection method.We propose two structures by combining of Mach-Zehnder interferometer and micro-ring resonator. Firstly, based on a single micro-ring resonator and Mach-Zehnder interferometer can be coupled to produce asymmetric Fano line shape, we proposed a U-type feedback micro-ring resonator coupled to the Mach-Zehnder interferometer sensor arm, and analyzed the transmission characteristics of the composite structure in different resonance case. It showed the steepest Fano line can be obtained at both end of the resonance points when the feedback waveguide length is three times of the micro-ring perimeter and with no additional phase shift in the reference arm as well as the use of U-type feedback ring having a tunable resonance wavelength, by adjusting the transmission coefficient. When using the intensity detection method to sense, we can get the sensing characteristics with high detection sensitivity. Next, using the micro/nano fiber we produced a micro ring resonator and Mach-Zehnder interferometer optical device in series. Simulation and experimental results showed that the structure can combine the interference characteristics and resonance characteristics effectively and has a higher extinction ratio.The theory of micro-ring resonator and experiments performed show that the proposed micro ring structures can improve the sensing performance of the traditional micro ring sensors and give an insight in designing micro ring resonator.
Keywords/Search Tags:optical sensor, micro-ring resonator, detection sensitivity, Mach-Zehnder interferometer, Fano line shape
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