Design And Analysis Of High Performance Dual-Parameter Sensor Based Side-Coupled Structure Photonic Crystal Nanobeam Cavities

With the continuous development of Internet technology,information has become an important resource,so the acquisition of information has become very important.As the key technology of information acquisition and collection,sensor technology has attracted the attention of researchers.The photonic crystal material is composed of a dielectric material whose dielectric constant changes periodically.Photonic crystals can be divided into one-dimensional photonic crystals,two-dimensional photonic crystals and three-dimensional photonic crystals.This classification is based on the direction of periodic changes in dielectric constant.The photonic crystal material has the characteristic of photonic band gap due to the periodic change of its dielectric constant,that is,light in certain wavelength bands cannot pass through the photonic crystal structure.Due to the advantages of small structure,good light controlled ability,and easy integration,photonic crystal has been applied to the manufacture of optical devices with various structures in recent years.The research of photonic crystal sensors has also attracted more and more attention from researchers.With the continuous enrichment of sensor application scenarios and the increasingly complex detection environment,traditional single-parameter sensing detection has been unable to meet the demand,and multi-parameter sensing detection has become a problem that needs to be overcome in the next research of sensors.In this thesis,an one-dimensional photonic crystal nanobeam microcavity based on a side-cavity coupling structure is designed to achieve simultaneous detection of multiple parameters.The main research contents of the thesis include:First,by designing an one-dimensional photonic crystal nanobeam microcavity sensor based on a side-cavity cascade coupling structure,it is used to simultaneously detect refractive index and temperature.The sensor is composed of an air mode microcavity and a dielectric mode microcavity cascaded by a bus waveguide,in which the dielectric mode microcavity is coated with a SU-8 layer.Due to the difference of electric field localization between the air mode microcavity and the dielectric mode microcavity,the interaction strength between the two microcavities and the object to be detected is different.This design makes the sensitivity of the two microcavities greatly different.In addition,since the thermo-optical coefficient of the SU-8 material is negative,a higher temperature sensitivity can be obtained by the dielectric mold microcavity covering the SU-8 layer,thus further increasing the temperature sensitivity difference of the two microcavities.This feature of large sensitivity difference enables the sensor to realize dual-parameter sensing even with slight interference.In this thesis,physical modeling of the proposed sensing structure is carried out and the transmission expression of the sensing structure is derived,and the coupling principle of the coupled sensing system is explained.Finally,through the simulation calculation of the simulation software,the refractive index sensitivity of the air mode microcavity of the proposed sensor is 210 nm/RIU,the temperature sensitivity is 53 pm/K,the refractive index sensitivity of the medium mode microcavity is 0nm/RIU,and the temperature sensitivity is-90 pm/K.In addition,this paper introduces the anti-external performance indicators aRI and ar to evaluate the sensor's anti-external interference performance.The smaller these two indicators are,the better the sensor has the ability to resist external interference.The proposed sensor structure not only has competitive sensitivity,but also has strong anti-interference ability through calculation and analysis.Secondly,by designing an one-dimensional photonic crystal nano-beam microcavity sensor based on a double-sided cavity coupling structure,it is used to simultaneously detect methane concentration and temperature.The structure consists of an air mode microcavity and a dielectric mode microcavity distributed on both sides of the waveguide.Methane-sensitive material is injected into the air hole of the air mode microcavity,while the air hole of the dielectric mode microcavity is not filled with any material.When the methane-sensitive material interacts with methane,the refractive index of the sensitive material will change,and the change of the refractive index of the sensitive material has a linear relationship with the change of methane concentration.There are three steps in the research of the double-sided cavity coupling sensing structure.Firstly,physical modeling is carried out for the double-sided cavity coupling sensing structure and the transmission formula of the structure is derived.Secondly,use simulation software to design and optimize the double-sided cavity coupling structure.Finally,through the simulation and calculation of the simulation software,the methane concentration sensitivity and temperature sensitivity of the air mode microcavity of the proposed sensor are:-0.56nm/%,64pm/K;the methane concentration sensitivity and temperature sensitivity of the dielectric mode microcavity are respectively It is:0nm/%,75pm/K.Therefore,the proposed sensor can simultaneously detect the methane concentration and temperature of the surrounding environment,and the design of the sensor provides innovative ideas for the design of multi-parameter chemical sensors in the future.In summary,this article focuses on a high-performance dual-parameter sensing model based on photonic crystal nanobeam side-cavity coupling structure.Firstly,an one-dimensional photonic crystal nanobeam microcavity sensor based on a side cavity cascade coupling structure is designed to resist external interference,which is used to simultaneously detect refractive index and temperature in a water environment;secondly,an one-dimensional photonic crystal nanobeam microcavity sensor based on a double-sided cavity coupling structure is designed to simultaneously detect methane concentration and temperature.In addition,the two proposed sensor structures are physically modeled,the coupling principle is analyzed,and the transmission formula is derived,which provides ideas and references for the design of the side cavity coupling structure.