Research On Sensing Characteristics Based On Subwavelength Structure Microring Resonator

With the development of science and technology,many integrated optical devices have been realized on silicon-on-insulator platform.As one of the basic components of integrated optical devices,microring resonators are widely used in the field of integrated optical sensors because of their advantages such as simple structure,excellent resonance performance,and cascading ability.The integrated,miniaturized and high-performance silicon based microring sensors cater to the development trend of on-chip sensing systems in the future.The sensing sensitivity and detection range of the silicon-based microring sensor are always important indicators to measure its sensing performance.Improving the sensing sensitivity can increase the accuracy of detection,and broadening the detection range can improve the applicability of the sensor.In order to meet the increasing needs of the accuracy and applicability,this paper proposes two sensor schemes that simultaneously achieve high sensing sensitivity and wide detection range.A racetrack microring sensor based on subwavelength grating waveguide is proposed,and the sensing sensitivity and detection range are verified by experiments.In addition,a racetrack microring sensor based on subwavelength grating slot waveguide is presented.The main work includes the following:(1)By using the plane-wave expansion method,this paper study the transmission and dispersion characteristics of the subwavelength grating waveguide.By using the finite-difference time-domain method,we calculate and analyze the dispersion characteristics of the round-trip amplitude transfer factor and the amplitude self-coupling coefficient of the subwavelength grating waveguide microring resonator.The transmission matrix method is used to realize the envelope transmission line of the microring.We simulate the drift of the envelope line of the microring under different refractive indices.We achieve a sensing sensitivity of 758.8 nm/RIU,and the detection range are no longer limited by the free spectrum range of the microring resonator.(2)According to the above theoretical simulation and simulation results,we design the structural parameters of subwavelength grating waveguide racetrack microring resonator We use electron beam lithography and coupled plasma etching to fabricate subwavelength grating waveguide racetrack microring resonators on SOI platform.The morphology and size of the device are measured by scanning electron microscope.We measure the envelope lines of subwavelength grating waveguide racetrack microring resonators with different glycerol concentrations,and the sensing sensitivity of the resonators is up to 790.79nm/RIU.We compare and analyze the differences between theoretical and experimental results.(3)By using the plane-wave expansion method,this paper study the transmission and dispersion characteristics of the subwavelength grating slot waveguide.By using the finite-difference time-domain method,we calculate and analyze the dispersion characteristics of the round-trip amplitude transfer factor and the amplitude self-coupling coefficient of the subwavelength grating slot waveguide microring resonator.The transmission matrix method is used to realize the envelope transmission line of the microring.We simulate the drift of the envelope line of the microring under different refractive indices.We achieve a sensitivity of 758.8 nm/RIU,and the detection range are no longer limited by the free spectrum range of the microring resonator.The subwavelength grating structure microring resonator proposed in this paper can improve the sensing sensitivity and broaden the detection range,which can provide a theoretical reference for the design of subwavelength grating structure microring resonator,lay a foundation for the optimization of the performance of key components in the refractive index sensing technology,and contribute to the development of on-chip sensing systems.