Designing photonic devices making use of periodic structures has become an essential and powerful tool in silicon photonics and specifically on the SOI platform. Subwavelength gratings enable performance enhancements of photonic devices and also new functionalities without needing more complex fabrication processes that increase manufacturing expenses. In addition, weak Bragg gratings stand as an attractive solution to implement narrowband filters with applications in communications and sensing. In this thesis, significant advances have been made in both SWG metamaterials and Bragg filtering fields. Enhanced modelling and simulation tools have been introduced. Novel SWG topologies and design methods have been developed and applied to the following devices: (i) polarization insensitive MMI couplers, (ii) a Bragg refractive index sensor, (iii) a tunable Bragg filter and (iv) an ultra-short and ultra-broadband spot-size converter. Rigorous electromagnetic simulations have been conducted for all devices, and most have undergone experimental characterization. The findings from these contributions have been disseminated through publications in high-impact peer-reviewed journals and international conferences.