Fano-resonance Characteristics Of Two-dimensional Photonic Crystal Microcavity And Its Sensing Application

In order to meet the miniaturization and high performance requirements of the sensing platform in the biochemical field,the use of the local mode resonance effect of the two-dimensional photonic crystal microcavity to develop new photoelectric sensing technology has attracted extensive attention from scholars at home and abroad.At present,the commonly used microcavity resonance is Lorentz resonance,the transmission spectrum has a symmetrical Lorentz line shape,and the sensitivity of the resonance peak to the change of the refractive index is low,which restricts the sensing performance.This graduation thesis focuses on the research of the two-dimensional photonic crystal double microcavity coupling structure and the microcavity air slot asymmetric coupling structure,and uses the plane wave expansion method combined with the time-domain finite difference method to study the Fano resonance of the structure under different coupling methods characteristic.Use the asymmetric Fano resonance line shape to replace the symmetrical Lorentz line shape,explore the application of the structure in realizing high-performance single-parameter sensing and dualparameter sensing,and provide new theoretical basis and technology for improving the sensing performance of photonic crystals support.The specific research contents are as follows:1.A high-sensitivity temperature sensor based on the Fano resonance of a two-dimensional photonic crystal double-microcavity coupling structure is proposed.Two half-open microcavities are symmetrically placed on both sides of the photonic crystal waveguide.The analysis results of the coupled mode theory and the simulation results of the time-domain finite difference method show that due to the direct and indirect coupling effects between the two microcavities,the transmission spectrum produces an asymmetric Fano resonance line shape.By optimizing the structural parameters,the maximum quality factor of the Fano resonance is about 10672,and the modulation depth is more than 90%.The dual-microcavity coupling structure is applied to temperature sensing,and its detection sensitivity is 91.9 pm/°C in the temperature range from 0°C to 360°C.2.A dual-parameter Fano resonance sensor based on the asymmetric coupling structure of twodimensional photonic crystal microcavity air slots is proposed.By placing the microcavity asymmetrically with the air slot,two Fano resonance modes can be excited in the waveguide structure,namely the air mode and the medium mode.By optimizing the structural parameters,the obtained Fano resonance quality factor can reach 5805 and 867.The temperature and refractive index dualparameter sensor based on the structure has a refractive index sensing range of 1-1.002,and a temperature sensing range of 0°C-90°C.The refractive index sensitivities of air mode and medium mode are 230 nm/RIU and 0 nm/RIU respectively,and the temperature sensitivities are 18 pm/℃ and83.8 pm/℃ respectively.In addition,the relative deviation rates of the two parameters of the sensor are 2.9% and 2.7%,respectively,which proves that the detection accuracy of the sensor is high.In conclusion,based on the two-dimensional photonic crystal double microcavity coupling structure and the microcavity air slot asymmetric coupling structure,this thesis realizes the highsensitivity temperature sensing as well as the high-precision temperature and refractive index dualparameter sensing,which provides theoretical and technical support for the application of photonic crystal sensors in biochemical fields.