The Study Of Optical Sensor Based On Dual Micro-ring Resonators

At present,traditional sensors have gradually failed to meet the needs of miniaturization,integration,and anti-interference in various industries.Therefore,the study of high-performance sensors has become a hot topic in many countries.The concept of"lab on a chip"has raised people's attention in integrated optics.Sensors based on integrated optics have also attracted great interest from researchers at home and abroad.As a classic structure of integrated optics,the micro-ring resonator has the advantages of compactness,low insertion loss,low crosstalk,etc.What's more,"Whispering Gallery Mode"makes the effective length of the light field propagating in the waveguide much larger than the actual waveguide length.Benefiting from the advantages above,high-sensitivity and high-integration sensors based on micro-ring resonator have been reported in large numbers.Meanwhile,it usually takes an increase in device footprint to enhance the performance of the micro-ring sensor.Therefore,it is meaningful to study high performance,small size micro-ring sensors.The purpose of this paper is to improve the extinction ratio and sensitivity of the micro-ring sensor without increasing the footprint of the device.Based on the analysis of planar waveguide theory,micro-ring resonator theory,coupled-mode theory and transfer matrix method,we propose an embedded-rings structure and designed an embedded-rings sensor based on Silicon-on-Insulator?SOI?.The parameters such as waveguide cross-section size,coupling length and coupling gap were designed and optimized for the purpose of increasing extinction ratio,sensitivity.The preparation of embedded-rings sensor was achieved with CMOS process.Benefiting from the advantages of embedded-rings structure and SOI material,the footprint of the sensor is only 15?m×10?m.The experiment results show that the extinction ratio of the device reaches 30 dB,the sensitivity is 157.16 nm/RIU,and the detection limit is 6.4×10^-5 RIU.The experimental and simulation results are consistent basically.For the purpose of increasing the sensitivity further,the cascaded embedded-rings structure is proposed.The cascaded embedded-rings sensor is realized by polymer materials and corresponding processing techniques to reduce cost.The purpose of introducing embedded-rings to cascaded structure is discussed by analyzing the characteristics of the envelope spectrum.After the process of spin coating,aluminizing,photolithography,etching,cutting and polishing,the cascaded embedded-rings sensor was fabricated successfully in the lab.The experimental results show that the sensitivity of the device reaches 338.96 nm/RIU,and the detection limit is 3.0×10^-5 RIU.The experimental and simulation results are consistent basically.