Refractive index engineered Bragg grating filters in wide SOI waveguides

Refractive index engineering represents a powerful technique to design devices with advanced characteristics in the silicon-on-insulator platform. The use of subwavelength grating waveguides (SWG), in which subwavelength periodicities in both longitudinal direction and transversal direction are exploited, has shown to be a simple way to tune the desired refractive index. In this work is theoretically carried out the design of different SWG based Bragg grating filters for TE and TM polarization optimized at wavelength 1550 nm and assuming a minimum feature size of 100 nm. The main novelty of the proposed topology is the utilization of wide waveguides, which allow us to effectively control the size of the band gap. Additionally, the resultant quasi-2D structure can be efficiently analyzed by using simpler 2D simulators. Bragg grating filter optimized for TE polarization achieves a band-gap of 100 nm and radiation losses below -20 dB. In contrast, TM polarized waves are able to achieve radiation losses as low as -35 dB and band gap of 18 nm.