| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 100 === Photonic crystals which possess the photonic bandgap due to their periodic structures have attracted intensive interests in science and technologies. Similar to electrons in solids, photons with some specific energy are forbidden within the photonic bandgap. In this study, we explore an ultrasensitive refractive index sensor using a magnetic photonic crystal (MPC) composed of a triangular lattice array of air holes with a Si background. Consider a microcavity created by altering the radius of an air hole in the middle of the photonic crystal. The defect filled with gyrotropic materials can serve as a refractive index sensor. By applying the external magnetic field in the y direction to the gyrotropic magnetic medium, we observe different refractive indices of the right-hand circular polarization mode and left-hand circular polarization mode. When the external magnetic field is applied in the y direction, the sensor has a better quality factor and the sensitivity. Furthermore we optimize the sensor by modulating the gyrotropic factor, which varies with the magnetic field applied in the y direction. Numerical results reveals that the proposed sensor has obtained the better quality factor, sensitivity and resolution of the sensor than preview ones. Finally, we show the characteristics of high resolution in the gyrotropic sensor by measuring the common gases.
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