SWG-based compact broadband two-mode multiplexer on SOI platform

This paper reports a compact two-mode silicon optical multiplexer using subwavelength grating (SWG) structures. The coupler section in the proposed device consists of an SWG-based access waveguide and a multimode strip bus waveguide. Tapers have been employed for adiabatic transition of the fundamental TM modes of the input strip waveguides to the respective fundamental TM modes of the SWG-based waveguide and multimode strip waveguide. The duty cycle and grating period are tailored to couple the first-order TM mode of the strip waveguide and the fundamental TM mode of the SWGbased waveguide. A 3D finite-difference time-domain simulation is performed to study the device performance. The multiplexer is very compact with a device length of 26 µm, which exhibits a return loss of >35.62 dB, crosstalk of <–33.60 dB, and insertion loss of <0.29 dB, at 1550 nm.