Ultra-broadband on-chip multimode power splitter with an arbitrary splitting ratio

Abstract

The multimode power splitter is a basic component in mode-division multiplexing systems. In this paper, we propose an ultra-broadband silicon multimode power splitter enabling arbitrary power splitting ratios. The proposed multimode splitter is designed based on a waveguide crossing with an obliquely embedded subwavelength grating (SWG) transflector. The incident multiple guided-modes can be split into two beams with low excess losses and low crosstalk by the SWG transflector where the thin-film interference effect happens. As an example, a silicon multimode power splitter is designed to work with the three lowest-order modes of TE polarization. Any desired splitting ratio ranging from 0% to 100% can be achieved by engineering the structural parameters of the SWG. Moreover, the desired splitting ratio can be very uniform over an extremely broad bandwidth of ≥ 415 nm, covering O-, E-, S-, C-, L- and U-bands. The intermodal crosstalk is < −20 dB for all the input modes in theory. To the best of our knowledge, the proposed structure is the first multimode power splitter enabling any desired power splitting ratios in all the optical communication bands.