Design and simulation of a compact three-mode (de)multiplexer based on a subwavelength grating multimode interference coupler

Abstract

This paper reports, for the first time to the best of our knowledge, the design of a compact three-mode converter/(de)multiplexer (DE/MUX) based on a 3 × 3 subwavelength grating (SWG) multimode interference (MMI) coupler. The device uses a π/2 phase shifter and an asymmetric tri-junction coupler built in a silicon/silicon-on-insulator (SOI) platform. The inherent dispersion and anisotropy properties of the SWG structure are employed to increase the traditional MMI coupler operation bandwidth and reduce the overall dimensions of the DE/MUX. The proposed device can realize mode order converting and (de)multiplexing of the fundamental transverse electric mode TE0, the first-order transverse electric mode TE1, and the second-order transverse electric mode TE2 to three uniform TE0 with good performance and compact size compared with the conventional ones. The designed device's overall area is 4.5 × 120 µm2, and its performance is simulated using Rsoft photonics CAD suit 3D-BPM. The simulation results show that the device exhibits a maximum insertion loss of 1.3 dB, maximum crosstalk of − 15 dB, and 120 nm (3 dB-bandwidth) over the entire C-band.