The Key Technology Of The High-Q Microresonator And Its Coupling Structure For Angular Rate Sensing Researches

Silica optical microresonantors can obtain the highest Q-factor as yet, and are of greatpotential in the high-Q resonator angular rate sensing researches.The optical microresonator angular rate sensing principles are analyzed theoreticallyaccording to the Sagnac Effect, which indicates that the stable resonant model is theprecondition for sensing research. However, as its discrete coupling structure, the traditionalmicroresonator coupling structure faces varies challenges during angular rate sensingresearches. The challenges include the difficulty in guaranteeing the selectivity of the angularrate sensing, maintaining the Q-factor, and improving the stability of the opticalmicroresonator coupling structure. All these challenges point to the noise which can interferewith the stability of the resonant mode. Generally, the noise includes the mechanical noise,ambient refractive index noise, thermal noise and laser frequency noise. In this paper, wefocused on the key technology of high-Q microresonator and its coupling structure to solvethe problems addressed above. The related work can be concluded as aspects below.1. The manufacture platform of the microresonator, the taper coupler and the test systemare constructed.The fabrication and post-processing platforms are built for three kinds of Silicon Dioxidemicroresonator (microsphere, microdisk and microtoroid), which enables the optimizedmanufacture of the optical micro resonators. Also, the taper fabrication system is constructed,which realizes the low loss taper (-0.15^-0.29dB) with the waist diameter of 1³Î¼m. Thecoupling structure of the microresonator with its taper is established and the test system isbuilt. The test result is that the microresonator can obtain the Q¹0^6-8.2. The packaging structure of the microresonator is designed, fabricated and tested.Aiming at the limiting factors in the microresonator based angular rate sensingapplication, for the first time, we propose the idea of improving the discrete coupling structureto realize an integrated structure, by using low refractive index, solidifiable optical material inthe packaging manner. Then, what the packaged structure requires from the packagingmaterial is analyzed, why the optical loss mechanism of the packaged optical micro cavitycoupling system differs from that unpackaged is discussed. Also, we demonstrate therelationship between the Q-factor of the packaged and the non-packaged coupling structure,as well as the dependence of the Q-factor on the characteristics (refractive index, absorptioncoefficient) of the package materials.Two physical structure models (spot-package and wholly-package) and the manufactureplatform of the two packaged structures are built. The Tested Q-factors of the two packaged structure both can reach as high as 10^6-7. Additionally, we point out that the wholly-packagedstructure is promising in the angular rate sensing application. Through improving thefabrication technology, the portable microresonator functional module is realized for the firsttime, which breaks the rule that there must be a huge position servo platform in traditionalmicroresonator coupling structure.3. The test platform for the wholly-packaged structure is designed and built. The testedperformance is demonstrated as below:1) Excellent robustness is shown in the structure. The favorable resonances are verifiedin low speed rotary test. Moreover, greater than 1g overloads can be tolerated in thewholly-packaged structure. The structure's outstanding mechanical vibration-resistanceperformance helps us to get rid of the trouble that traditional optical microresonator couplingstructure can't work under vibration.2) The isolation of the microresonator and the surroundings is realized in the packagedstructure, which solves the problem of decoupling between the"non-evanescent sensing"andthe"evanescent sensing"in the angular rate sensing application.4. The influence of the water molecule and dust in the surroundings on the resonantanceis analyzed theoretically and experimentally. Then, the Q-factor model, with the interventionof the practical environment related factor, is established. This Q-factor model breaks theregular model under ideal situation. The wholly-packaged structure eliminates the Q spoilingfactors, and for the first time, fulfills a long period Q-maintenance in the complicated, harshenvironment.5. The frequency reference unit based on the wholly-packaged structure is proposed.Additionally, the test system with such reference unit is built.The thermal noise model of the optical microresonantors is built. According to thismodel, the ice-water-mixture is used as the test environment to suppress the thermal noise.For the first time, by using the wholly-packaged microresonator, we construct a frequencyreference unit, which can be used in microresonator sensing test. Then, the opticalmicroresonator test system with frequency reference unit is proposed and constructed.Through the researches addressed above, the stable optical resonant unit is realized,which can meet the demand for microresonator angular rate sensing researches. In addition,these works can promote other microresonator-based practical sensing researches, forexample, pressure sensors, micro displacement sensors, biochemical sensors, etc.