Broadband three-mode converter and multiplexer based on cascaded symmetric Y-junctions and subwavelength engineered MMI and phase shifters

Mode-division multiplexing has emerged as a promising route for increasing transmission capacity while maintaining the same level of on-chip integration. Despite large number mode converters and multiplexers reported silicon-on-insulator platform, scaling multiplexed modes is still critical challenge. In this paper, we present novel three-mode architecture based on multimode interference couplers, passive phase shifters cascaded symmetric Y-junctions. This can readily operate up to third-order by including single switchable shifter. Moreover, exploit subwavelength grating metamaterials overcome bandwidth limitations couplers shifters, resulting in simulated 161 nm with insertion loss crosstalk below 1.18 dB -20 dB, respectively.