Structural Design And Optimization Of SOI-based Microring

As a new kind of transmission medium, the size of optical.waveguide is smaller than micrometer range, which is one of the cross application between information technology and nano technology, and it has low transmission loss and strong evanescent field. Some related devices have been applied to information and communications, industrial control, biomedical, resource investigation and other fields that have a great influence on people’s lives. As a kind of important optical component, optical microring structure possesses a series of advantages, such as high quality factor, good filtering properties and optical storage ability. It has been widely used to make filters, light switches, sensors, optical gyro and other important optical devices.Besides the features mentioned above, microring structure based on silicon on insulator (SOI) is compatible with CMOS process, which is beneficial to mass production, and it has smaller bending loss. With the further development of MEMS Packaging Technology, optoelectronic integration will be realized, which can support the development of low cost, chip optical waveguide devices, leading to achieve portable ring sensors, chip light source, etc. Therefore, research on microring structure plays a significant role in development of optical waveguide devices.In this paper, the mode transmissions of different SOI waveguide structures, including slab optical waveguide, strip waveguide, rib waveguide and cylinder waveguide were studied based on optical waveguide transmission theory, and the microring transmission models with different cross sections were proposed to analyze principle of the microring resonator and its sensing performance. The calculation formula is derived based on transmission model and the main sensor parameters of the microring were explored. At the same time, optiFDTD software was used to investigate the mode field distribution of straight waveguide. The impact on the output spectrum, including the radius of the microring, waveguide width, coupling gap and other key parameters were analyzed, and the optimum structure parameters were determined, In addition, the change of sensitive factors, Q factors and the other sensing characteristics such as measuring ranges were compared under the same structure parameters. According to the theory of hydrogen annealing smooth process, the model of annealed waveguide structures is set up and the effects of annealing process on microring sensing performances were analyzed. The optimized microring was realized by using MEMS process. Some preliminary experiments were started to investigate the hydrogen annealing effect on waveguide surface roughness. Simulation results demonstrate that hydrogen annealing process is the main factor which affect the sensing characteristics of microring structure. After smooth process, the microring structure with cylinder cross section has the maximum sensitive coefficient and the measuring range and Q factor is basically constant. This will provide a theoretical basis for annealing tests and it will offer data support for the optimization of microring sensor performance in the future.