The Study Of Refractive Index Sensor Based On Multi-micro-ring Resonators

As one of the three pillars in information technology,sensing technology has influenced important aspects of our society,such as scientific research,food safety,environmental monitoring,disease detection,chemistry and chemical engineering.However,with the progress of information society,the requirements on sensing devices have been raised in various fields.Because of the"bottleneck effect"caused by electrical interconnection,it is difficult for electronic devices to realize high-speed processing of large capacity information.While optical signals,with the advantages of large bandwidth,ultra-high speed and parallel processing capability,can solve this problem well.The technology to use photons instead of electrons for information loading has developed dramatically in the field of optical communication so far,effectively improving the speed and capacity of information processing,which has a promising future.The development of optical sensors is particularly crucial in the background that traditional electronic sensors can no longer meet the market demand.The structures and materials of optical waveguide based sensors are diversified and flexible.These sensors inherit the advantages of traditional optical sensors such as high sensitivity and strong anti-electromagnetic interference,and are more suitable for functional integration,compact packaging and mass production as well.However,the common micro-ring resonator based sensors often have the defects of low sensitivity and large full width at half maximum,degrading the device performance.The purpose of this paper is to improve the sensitivity of the micro-ring based sensor on the basis of optimizing the output line shape.In this paper,the spectrum narrowing theory is proposed innovatively based on the basic theory of optical waveguide and micro-ring resonator,and a multi-ring spectrum narrowing refractive index sensor based on silicon-on-insulator(SOI)material is designed.By distributing the absorption peaks of two micro-rings on both sides of the transmission peak of another micro-ring,the width of the transmission peaks is narrowed,and the full width at half maximum is reduced,improving the figure of merit.The full width at half maximum of the sensor output is only 0.54 nm.Compared with the output spectrum before spectrum narrowing,the full width at half maximum is reduced by 1.102 nm.In order to improve the sensitivity of the device,a grating structure is introduced based on the theory of spectrum narrowing,and an all grating structure spectrum narrowing refractive index sensor is proposed.Through more ingenious structure design,the sensor not only achieves the effect of spectrum narrowing,but also expands the wavelength range of absorption peak by cascading multiple micro-rings,thus suppressing the sidelobes of the output line shape.Moreover,grating structure waveguide enhances the interactions between the analyte and the light field,greatly improving the sensitivity of the sensor.The simulation results show that the sensitivity of the device is as high as536.67 nm/RIU,with the full width at half maximum of only 0.29 nm,and the figure of merit as high as 1850.57 RIU^-1.In order to further improve the performance of the sensor,Fano resonance is introduced,and a multi ring resonant Fano sensor based on all grating structure is proposed.The optical signal passes through multiple grating structure based micro-rings,and an expected Fano line shape is finally obtained due to the interaction of micro-ring resonators and the coherent superposition of light in multiple transmission paths.Since the sensor is based on grating structure,high sensitivity can be achieved simultaneously.According to the simulation results,the sensitivity of the sensor is as high as 500 nm/RIU,with the full width at half maximum of merely 0.25 nm,and the figure of merit as high as 2000 RIU^-1.