Compact and broadband design of an 850 nm 2 × 2 3-dB directional coupler with a shallowly etched SWG gap

On-Chip Design of a Broadband 850 nm TM-Pass/TE-Stop Polarizer with Tilted Subwavelength Gratings

An integrated TM-pass/TE-stop polarizer centered at 850 nm is designed in this paper. The proposed polarizer is designed on a Si3N4 on insulator platform with tilted subwavelength gratings (SWG). Since the tilted SWGs have much more of an impact on the effective index of the TE polarization state than that of the TM polarization state, they help to achieve high TM and low TE transmission simultaneously. After geometries optimization, the polarizer’s working bandwidth, which is defined as the wavelength region with an extinction ratio higher than 20 dB, is determined to be 185 nm under a SWG tilting angle of 30 degrees. At the same time, the insertion loss is always less than 0.45 dB over the entire working wavelength band. Finally, the results of fabrication tolerance analysis show that the SWG ridge width jitter only degrades the polarizer’s working bandwidth by 16 nm.