The special whispering wall structure of the optical micro-ring resonator with high Q value and small size is widely used in integrated photonics.In optical communication,it is often used as optical switch,optical delay device,optical filter,and optical sensor can be used for biochemical sensing,ultrasonic imaging.Polymers have many advantages that common semiconductor materials do not have,such as low cost and simple process,and are becoming more and more popular in optical waveguide materials.This paper introduces the development of microring resonators and the current research status at home and abroad.combined with simulation,the optical transmission characteristics of microring resonators are analyzed,and a through-type polystyrene microring resonator is designed and fabricated.Its Q value can reach 10~5.Finally,the micro-ring resonant cavity is applied to underwater ultrasonic detection,which lays a theoretical foundation for the research of micro-ring ultrasonic imaging.The main work of this paper is as follows:Firstly,with the aid of the directional coupling transmission matrix,the transmission characteristics of the light field in the microring resonator are deduced,and the influence of the physical structure of the microring resonator on the transmission line of the microring is analyzed.Based on theoretical knowledge combined with analysis methods,such as finite element method and finite difference time domain method,with the aid of simulation software analysis and verification of its laws,the optical performance(Q value,free spectral range,coupling depth,etc.)and structural parameters(The relationship between the radius of the microring,the size of the waveguide cross-section,and the coupling distance).With the help of COMSOL simulation software,a straight-through polystyrene microring resonator is designed.Then,according to the designed polystyrene microring resonant cavity structure,a high aspect ratio silicon mold with the same pattern as the microring resonant cavity is produced through EBL,ICP pseudo-Bosch etching and other processes,and then transferred by nanoimprint technology with the help of PDMS soft mold.Printing transferred the pattern on the silicon mold to the polystyrene film,and finally realized a polystyrene microring resonator with a microring radius of 100μm,a height of 1.4μm,and a width of 1.5μm,a Q value of up to 2.19×10~5(@1310 nm),and connect the polymer waveguide with the ordinary optical fiber through flat-end coupling,and make the micro-ring resonator into an applicable sensor.Finally,a set of microring spectral line deviation amplitude measurement system based on the photoelastic effect was built.The above polystyrene microring sensor was placed in water,and the amplitude change of the working point on the microring transmission spectrum line was collected to monitor external ultrasonic changes.The polystyrene microring resonant cavity produced in this paper has a sound pressure sensitivity of-228 d B under the action of 1MHz sound waves,and the close relationship between its sound pressure sensitivity and the Q value of the microring,coupling depth,and output power has been studied. |