Ultrathin WS₂ Polariton Waveguide for Efficient Light Guiding

Abstract

Light confinement to sub‐wavelength scales is actively studied for nanophotonic applications because it gives rise to intriguing optical properties with enhanced light‐matter interaction. Herein, an ultrathin exciton–polariton waveguide based on a WS2 multilayer is proposed for sub‐wavelength light guiding. A WS2 waveguide supports guided exciton–polariton modes even with a few tens of nanometers of thickness. It is theoretically confirmed that the WS2 waveguide has significantly lower propagation loss than a plasmonic mode, although its thickness may be similar to that of a plasmonic waveguide. By injecting white light into a fabricated WS2 waveguide, light guiding is experimentally demonstrated through a 20 nm thick WS2 waveguide. Notably, this study integrated the WS2 waveguide with a WSe2 monolayer to demonstrate the coupling of monolayer emission to the polariton waveguide. The results suggest that WS2 multilayers provide a novel material platform with potential for nanophotonic applications, including ultrathin optical integrated circuits.

Recent progress of exciton transport in two-dimensional semiconductors

“…The exciton transport as a coupled form with SPP exhibits the potential for the development of plasmonic optical interconnects and circuits [81][82][83][84][85]. The plasmon-exciton coupling enables the long-range transport of exciton emission [78,81,[86][87][88][89] while maintaining intriguing optical characteristics of 2D TMDs, such as valley degree of freedom and indirect bandgap lasing [64,82,84,[90][91][92][93]. In addition, coupling to plasmon leads to the concentration of the electromagnetic fields down to the sub-diffraction-limit, enhancing the degree of integration in circuit applications [78,[81][82][83][94][95][96][97].…”