Study On The Transfer Mechanisms And Sensing Properties Of Microring Resonator

Optical sensing technology is a synthesis of many subjects and is of great scientificand practical value. With the increasing requirement of miniaturization, portability andhigh sensitivity to the sensors for disease diagnosis, military weapons and environmentmonitor, optical micro sensor becomes a hot spot. The micro-ring resonator is widelyapplied in sensing fields such as temperature, humidity and refractivity due to the highquality factor, narrow bandwidth and highly integration. This paper describes thetransmission characteristics of the different structure of the micro-ring under thebackground of sensing application. Deep analysis of the sensitivity and dynamic range ofmicro-ring sensor is presented theoretically and experimentally, striving to use smallervolume,higher sensitivity and lower cost for the measurement of environmentalparameters.The coupled mode theory and transfer matrix method were used to analyze thetransmission characteristics of the double micro-ring resonator. The output spectralcharacteristics of conjugated series coupled double micro-ring were researched on thebasis of the traditional series coupled double micro-ring. Compared with single micro-ringresonators with ‘Through’ port using the same structural parameters, the double micro-ringhas higher resonant depth and Q value and achieves a better band-stop filter performance.The transmission characteristics of all-pass double micro-ring resonator structure wereanalyzed, and it will lead to significantly increasing resonant depth with the same radiusand the steeper maximum slope of the output spectrum. All these provide a theoreticalbasis for further study of micro-ring sensing experiments.The sensitivity and dynamic range of the micro-ring sensor were researched at length.Series coupled double micro-ring resonator based on SOI waveguide with different radiiwas used for temperature sensing. Thermo-optical effect and thermal expansion effect ofSOI will cause the refractive index and length of the waveguide being changed. Spectraldrift detection methods were used to analyze the temperature sensing properties ofmicro-ring, proving that the structure is suitable for large dynamic range temperature sensor design.Mach-Zehnder arm embedded micro-ring structure using polyimide as humiditysensor was used to design the temperature sensing system. Optical field distribution of thepolyimide polymer ridge waveguides and the effective refractive index of opticalwaveguide were obtained by numerical computing. After polyimide’s moisture absorption,the effective refractive index of waveguide will change. The humidity sensing propertiesof micro ring was analyzed. Simulation results showed that when U-feedback waveguideand micro-ring both feel wet, the dynamic range of the humidity sensor was three timescompared with single micro-ring.Micro-fiber waveguide line and fiber micro-ring platforms were built. Micro-fiberwas produced using fusion method. A variety of single fiber ring resonator with differentradii, all-pass series coupled double micro-ring with same or different radii were produced.The spectral characteristics of micro-fiber ring resonator were researched experimentally.The experimental results showed that all pass series coupled double micro-ring had agreater resonance depth and spectral slope compared with a single micro-ring using sameradius. Thus, it shows double ring resonators have high extinction ratio filtering propertiesand high sensitivity characteristics.