Side-mode suppressed filter based on anangular grating-subwavelength grating microring resonator with high flexibility in wavelength design

The subwavelength grating microring resonator (SWGMRR)-based filter is a promising device in optical sensing and communication. However, its comb spectrum nature is not suitable for the track or extraction of a single wavelength of a broadband light source. In this paper, we propose a silicon-photonic side-mode suppressed filter based on angular grating-SWGMRR (AG-SWGMRR) with high flexibility in wavelength design in the silicon-on-insulator (SOI) waveguide for the first time. With the periodical arrangement of the silicon pillars in three different widths, the effective index along the inner sidewall of the SWGMRR will be engineered and, finally, the characteristic of wavelength selection can be realized. The impacts of several key parameters on the center wavelength, side-mode suppressed ratio, and quality factor of this filter, as well as the process of optimization, are investigated and presented, giving a constructive direction in the design of this kind of structure. The simulated results in bulk sensing application indicate that this AG-SWGMRR obtains a high sensitivity of 672.8 nm/RIU and a low limit of detection of 6.69×10-5, which is not restricted by the free spectral range for its side-mode suppression. Additionally, a cascaded system for wavelength multiplexing applications comprising six AG-SWGMRRs with different center wavelengths by tuning the widths of silicon pillars is also demonstrated. The good performance, compact volume, compatibility with other SWG waveguide-based devices, and flexibility in design of our proposed structure guarantee its great potential in both compact biomedical sensing and optical communication systems.