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Study On Biosensor Of Optical Waveguide Ring Cavity

Posted on:2016-05-30Degree:MasterType:Thesis
Country:ChinaCandidate:T R BuFull Text:PDF
GTID:2308330464970028Subject:Radio Physics
Abstract/Summary:PDF Full Text Request
The optical waveguide ring cavity sensor has become the one of hot research in sensors for its advantages of high sensitivity, strong resistance to electromagnetic interference, and miniaturization. It measures the change of the refractive index of medium for biological detection by using optical evanescent field. In this thesis, two new type sensors of micro-ring resonators are proposed, which respectively based on methods of intensity detection and wavelength detection. The device structures and their sensing characteristics are analyzed and the optimizing designs are studied. Under the optimal designs, the two new type sensors have achieved excellent performance. The main research work is as follows:First of all, for the biological sensing detection with miniaturization, good stability and high sensitivity, we designed a new tpye of optical microring resonation transducer with racetrack and feedback stuctures. The sensor made up of a U feedback waveguide, a racetrack cavity and a sensitive ring. The normalized transmission formula of the sensor was derived by the transfer matrix method. The effects of the transmission loss factor, the coupling factor and the sensitive ring size of sensor on the properties of sensing sensitivity were numerically analyzed. Based to the results of simulation analysis, the device structure is optimized. The optimization of microring structure can not only output sharp steep asymmetric Fano resonance spectral lines, but also obtain a high Fano resonance spectral slope, which is better to enhance the sensor sensitivity. In a measurement system of 30 dB signal-to-noise ratio, a detection limit can reach to 4.48×10-8 refractive index units by using the optimized microring sensor of feedback racetrack.The second, aiming at the wavelength detection of wide spectrum in biological sensing applications, a sensor of double micro-ring resonator based on Mach-Zehnder interference (MZI) which produced the Vernier effect was designed. It mainly consisted of two 3dB couplers, two pairs of straight waveguides, a sensitive ring and a reference ring. Using the Coupled-Mode theory, a normalized transmission formula of the sensor was derived and its output spectrum properties were analyzed. The simulation analysis showed that the sensor can generate a major peak of spectral line with high amplitude, and the major peak shifted digitally. When the change of effective refractive index was equal to integer times of detection limit, the position of major peak shifted with integer multiple of km. In this optimal design, the detection limit of sensor lowed to 6.732×10-5RIU, and the sensitivity reached to 3.730×104nm/RIU, which was 52 times higher than the traditional micro-ring resonator of double waveguide. When using light source, whose bandwidth is 310 nm, it can detect the change of substance’s effective refractive index ranging in 0.0083. The sensor has advantages of a wide dynamic range, low detection limit, insensitivity to the free spectral range.
Keywords/Search Tags:Microring resonator, Sensor, Mach-Zehn interference, Vernier effect, Sensitivity, Detection limit
PDF Full Text Request
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