Simulation analysis of micro-ring resonator based on diamond multilayer waveguide structure

With the development of the technology for fabricating high-quality synthetic diamond and diamond waveguide structures, more and more researchers are being involved in exploring the particular optical properties of diamond for different applications. Because of its high refractive index and nontoxicity to biological species, diamond can be used to make micro-ring resonator to detect the concentration of liquid or gas. In this paper, a single micro-ring resonator model with diamond serving as the core layer is proposed. In the model, the vertical-section of the waveguide adopts a five-layer ridge-type waveguide structure based on As2S3, SiO2 and diamond, i.e. As2S3-SiO2-Diamond-SiO2-As2S3. To investigate the optical properties of the resonator, the vertical-section of the single straight waveguide, the coupling region of the direct waveguide, and the ring waveguide are simulated with the adopted operating wavelength =1550 nm based on the coupling mode theory and micro-ring resonance theory. In addition, the distribution of the field strength for the micro-ring is described at a resonant wavelength of 1543 nm. It is very important to explore the field intensity distribution of the micro-ring for understanding how the light transmits. The transmission characteristics of the micro-ring with the change of the distance between the straight waveguide and the ring waveguide in the coupling region are also simulated. The quality factor and the influence of the coupling coefficient change on the output spectrum are studied by the transfer matrix method and the micro-ring loss is discussed. It is shown that the micro-ring resonator designed with the diamond material has good transmission characteristics. When the resonant wavelength is 1543 nm, the resonant peak reaches more than -12 dB. The quality factor is about 1.54105. When the coupling coefficient k is 0.01, the free spectral range is about 40 nm. The coupling coefficient k is determined by the distance S of the coupling region. The results show that when S is equal to 50 nm, the output spectrum has a good extinction ratio and is better compared with the other values. The error of material processing is mainly affected by size, so the output spectrum near the distance S=50 nm is studied. The result shows that in the tiny change scope, the spectral output peak is linearly related to S. The structure we suggested in this paper expands the application scope of diamond in the field of optics, and provides some guiding significance for developing the optical integrated chips.