Photonics inverse-designed compact dual-mode 3 dB power splitter for on-chip MDM systems

Abstract

Optical power splitters are fundamental devices in on-chip optical systems, enabling coherent optical modulation through beam splitting and combining. Despite many mature theories and devices for power splitting in the single-mode scenario, achieving compact 3 dB power splitters in the multimode regime remains challenging. Here we present a compact dual-mode 3 dB power splitter for mode-division multiplexing (MDM) systems. The device supports both TE0 and TE1 modes of power splitting and maintains the mode order invariant. Our design incorporates the adjoint variable method (AVM) and level-set method to create a device structure that is compact and single-connected. The device features a footprint of 10 μm × 3.4 μm, with a minimum feature size larger than 200 nm to ensure compatibility with standard silicon on insulator (SOI) processes. Experimental results show that the insertion loss is 0.7 dB for the TE0 mode and 1.1 dB for the TE1 mode at the wavelength of 1550 nm. The proposed device may hold potential in on-chip MDM technology, such as multimode optical attenuators and switches, with compact size and high performance.