Mechanism Research And Design Of Photonic Crystal Sensing Sensor Based On Band Gap And Light Constraint Characteristics

Micro-and nano-sensors occupy an important position in the current micro-and nano-detection field,among which photonic crystal sensors have the potential advantages of flexible design and on-chip integration,attracting wide attention in theory and practice respectively.Based on the unique photonic band gap and optical local characteristics of photonic crystal,it is possible to design the photonic crystal sensor and realize micro-nano-detection.Although considerable progress has been made in the research of photonic crystal sensors,there are still several problems that need to be solved:low detection sensitivity,high scattering loss and poor anti-interference performance of photonic crystal refractive index sensors,which seriously restrict the practical application of this type of sensor;As the measured parameters such as gas and nano particles have little influence on refractive index,high sensitivity detection cannot be achieved,which further limits the application range of photonic crystal sensors.Therefore,aiming at the above key problems to be solved,this paper designed photonic crystal sensors with multiple application prospects,explored their sensing mechanism,and deeply analyzed the optical sensing characteristics of photonic crystal sensors,aiming to improve their detection sensitivity and anti-interference and other performance indicators.The main research work is as follows:Firstly,considering that the defect mode of photonic crystal is sensitive to the change of refractive index in the environment,three kinds of silicon based photonic crystal refractive index sensors are designed,which can meet the detection requirements of different number of parameters and improve the refractive index sensitivity.A single refractive index sensor with high sensitivity is designed based on the optical local characteristics of point defects and the optical transmission performance of line defects with a sensitivity of 303.65 nm/RIU.In order to overcome the limitation of detection error caused by ignoring temperature in current sensors of the same type,a three-cavity coupled photonic crystal structure was designed based on the Fano resonance mechanism,which realized dual-parameter detection of temperature and refractive index with high sensitivity and low cross talk,reaching 377.2 nm/RIU and 261 pm/K,respectively.In order to improve the integration degree of refractive index sensor,photonic crystal waveguide with wide band width is realized by suppressing Bragg effect,and a micro-cavity array structure with adjustable resonant frequency is proposed to realize high sensitivity up to332 nm/RIU multi-parameter detection.The research provides a new idea for the design of high performance micro-cavity coupled waveguide sensor.Secondly,in order to reduce the scattering loss of photonic crystal refractive index sensor in practical application,and reduce the interference caused by etching error and further improve the refractive index sensitivity,a kind of photonic crystal refractive index sensor based on SOI silicon chip was designed.By exploring the edge state protection mechanism of topological structure,waveguide and micro-cavity structures with topological edge protection characteristics were designed,and the device was fabricated by dry etching technology.The experiment proves that the topological photonic crystal refractive index sensor has the unique advantages of low loss,strong defect immunity and high refractive index sensitivity.The sensitivity was increased to 1228 nm/RIU,which can provide an effective solution for higher performance refractive index sensing.Thirdly,in order to solve the problem that the refractive index sensor cannot be used to achieve high sensitivity detection due to the small change of refractive index of gas,two photonic crystal gas sensors are designed and applied to the detection of SO₂and CO gases.Based on the fluorescence characteristics of SO₂gas molecule and the control mechanism of fluorescence emission in the vertical direction by the photonic crystal array structure,a photonic crystal gas sensor with fluorescence enhancement effect was designed.Experimental results show that the structure can improve the excitation efficiency of SO₂gas fluorescence and achieve high sensitivity measurement of SO₂,and the detection sensitivity was increased by 8-fold.Based on the absorption characteristics of CO gas and the interlocking effect of grooves,a kind of photonic crystal microcavity gas sensor with ultra-high Q/V value was designed,which realized the detection of CO gas with high sensitivity and strong anti-interference and selectivity,with a detection sensitivity of up to 978.5 Hz/ppm.This provides a new method to improve the performance of traditional gas detection technology and expand the application field of photonic crystal.Finally,aiming at the problem that the refractive index sensor can not capture and detect low concentration micro-and nano-particles,the application range of photonic crystal sensor is further broadened.Based on the optical force detection mechanism,a photonic crystal mixed cavity optical tweezers device is designed.Based on the surface plasmon resonance characteristics,the diffraction limit of light is broken and the mode volume V is greatly reduced,thus reducing the detection limit with a minimum measurable particle size as low as 25 nm.By solving the Maxwell surface stress tensor,the relationship between the optical force on the polystyrene particles and the position of the particles was analyzed,and the capture range of the particles in the mixing cavity was determined.The relationship between the offset of the resonant frequency and the intensity of the electric field was deduced,which provided an effective way for the detection of low concentration micro-nano particles.