Broadband dual-mode 3 dB power splitter using bricked subwavelength gratings

The multimode power splitter plays an essential role in on-chip mode-division multiplexing systems. In this work, a broadband dual-mode optical power splitter based on the self-imaging effect in the multimode interference (MMI) engineered by bricked subwavelength gratings (BSWGs) is proposed. The dual-mode power splitter is optimized by combining the 3D finite difference time domain (FDTD) and the particle swarm optimization (PSO) method. For the input T E 0 mode, the insertion loss (IL) and the imbalance (IB) are lower than 0.55 dB and 0.65 dB, while the IL and IB for the input T E 1 mode are, respectively, lower than 0.7 dB and 0.37 dB over 150 nm bandwidth in the wavelength range of 1.5–1.65 µm. In addition, the cross talk (CT) is lower than − 25 d B for the two modes over this wavelength range. Furthermore, the minimum feature size of the gratings is as large as 135 nm, and only a single etch step is required, which is beneficial for the fabrication.