Excitonic Resonant Emission-Absorption of Surface Plasmon in Transition Metal Dichalcogenides for Chip-level Electronic-Photonic Circuits Integrated Circuits

The monolithic integration of electronics and photonics has attracted enormous attention due to its potential applications. However, the realization of such hybrid circuits has remained a challenge because it requires optical communication on the nanometer scale. Using photoexcitation, direct optical imaging, spectral analysis and numerical simulations, we show the perfect spectral overlap between absorption and photoluminescence in WS2 monolayers; we then show the resonant coupling of WS2 photoluminescence to surface plasmons of silver nanowire waveguides; finally, we prove the resonant absorption of the surface plasmons by the same WS2 monolayers. This strong absorption by WS2 is distinguished from that of the Ohmic propagation loss of silver nanowires and is further confirmed by numerical calculations. Such emission-absorption resonance is a manifestation of a unique excitonic transition in WS2. The demonstration of optical generation and detection of surface plasmons at the same wavelength paves the way for on-chip optical communication and electronic- photonics integrated circuits.