Simulation Of Optical Resonator And Its Sensing Properties Base On FDTD

WGM based optical microcavity has the characteristics of high-quality factor and small mode volume,which makes it have great application prospect and important scientific significance in many research fields such as optical sensing and optical communication.Therefore,it has become the focus of researchers’ attention.One of the characteristics of WGM sensors is that their ability to respond to environmental disturbances affects the optical mode distribution.High sensitivity of WGM devices,coupled with the diversity of its structure and is easy to be compatible with existing chip integration technology,WGM resonator is used to detect not only the physical substance,such as nanoparticles,small molecular biological/chemical or gas,liquid,and is also used to detect impact model of optical resonator or around the physical parameters,such as temperature,pressure,electric and magnetic fields.In this paper,combined with the research hotspots at home and abroad,the research on optical resonator in sensing is mainly studied.Firstly,starting from the research background of optical microcavity,the current research hotspots in the field of optical microcavity and several typical types of microcavity are introduced,and its working principle,advantages and disadvantages are also introduced.Then,the research status and development trend of optical microcavities at home and abroad are introduced,and the research level of optical microcavities up to now is summarized.Secondly,the finite-difference time-domain(FDTD)algorithm and the resonant mode theory of echo wall are introduced,and the resonant mode parameters and resonant cavity coupling theory are described.Then the simulation of the sensor is introduced,and the cascade microcavity is used to study and optimize the cursor effect.On the one hand,a single optical resonator is simulated to optimize its Q factor and other characteristics,and then the performance of multiple resonators is evaluated according to the characteristics of a single resonator.Then the cascade resonator is simulated and analyzed to get the optical characteristics better than that of a single resonator.For the structure of the Vernier double-loop sensor,its working principle is analyzed,and the influence of parameters on the spectrum characteristics is discussed.Then,by using the Vernier effect,the structure with higher sensitivity is obtained.On the other hand,based on the previous work of thick-walled capillary microring cavity,a multilayer PE film was designed to capture polystyrene microspheres with carboxyl functional groups,and a kind of echo wall phenomenon was found in the light field of the polystyrene microspheres,and a theoretical resonance model was established for high sensitivity sensing.In addition,we simulate the generation of vortices by using a microring cavity with angular gratings,and the simulation models involved are introduced in detail.Finally,the mechanism of resonant mode splitting is studied by using FDTD combined with optical field distribution and spectrum.The field distributions of the basic and second order radial symmetric and asymmetric modes relative to the position of the nanoparticles are simulated.Then,the splitting of the fundamental modes(～ 0.010THz)due to the backscattering of the particles is distinguished from the separation of the fundamental modes(～ 100nm)from the higher order modes(～1THz)of the same particle.In addition,the size and number of particles are estimated by the method of fundamental mode splitting,and the simulation results are analyzed and summarized.