Optical Introduction and Manipulation of Plasmon–Exciton–Trion Coupling in a Si/WS₂/Au Nanocavity

Abstract

Strong plasmon–exciton coupling, which has potential applications in nanophotonics, plasmonics, and quantum electrodynamics, has been successfully demonstrated by using metallic nanocavities and two-dimensional materials. Dynamical control of plasmon–exciton coupling strength, especially by using optical methods, remains a big challenge although it is highly desirable. Here, we report the optical introduction and manipulation of plasmon–exciton–trion coupling realized in a dielectric–metal hybrid nanocavity, which is composed of a silicon (Si) nanoparticle and a thin gold (Au) film, with an embedded tungsten disulfide (WS2) monolayer. We employ scattering and photoluminescence spectra to characterize the coupling strength between plasmons and excitons in Si/WS2/Au nanocavities constructed by using Si nanoparticles with different diameters. We enhance the plasmon–exciton and plasmon–trion coupling strength by injecting excitons and trions into the WS2 monolayer with a 488 nm laser beam. It is revealed that the emission intensities of excitons and trions with respect to the reference WS2 monolayer can be modified through the change in the coupling strength induced by the laser light. Interestingly, the coupling strength between the plasmons and the excitons/trions can be manipulated from weak to strong coupling regime by simply increasing the laser power, which is clearly resolved in the scattering spectra of Si/WS2/Au nanocavities. More importantly, the plasmon–exciton–trion coupling induced by the laser light is confirmed by the energy exchange between excitons and trions. Our findings indicate the possibility for optically manipulating plasmon–exciton interaction and suggest the practical applications of dielectric–metal hybrid nanocavities in nanoscale plasmonic devices.

All-optical control of high-purity trions in nanoscale waveguide

“…The TRPL traces are fitted by a biexponential function with fast (τ 1 ) and slow (τ 2 ) components 23 . Unlike previously reported plasmon-coupled platforms, exhibiting significant decreases in decay time [24][25][26] , both components derived from lateral MIM waveguide show minimal changes in decay time compared to the ones from silicon. Specifically, the strain gradient geometry exploits the funneling of electrons and high exciton-to-trion conversion efficiency 6 , resulting in the smaller number of injected electrons to achieve complete exciton-to-trion coversion.…”

Tunable Kerker Scattering in a Self‐Coupled Polaritonic Metasurface

“…Although here we only discuss the simple condition where the excitons are solely coupled to MD mode (which is valid since the ED and MD resonances are far detuned for this case), the tunable Kerker scattering by tailoring the polaritonic properties still holds even for a more sophisticated condition when the formation of polaritons involves more Mie modes or material transitions. [53,54,55] As an experimental demonstration, we consider a MoS 2 metasurface with constituent nanodisks arranged in a lattice. As schematically shown in Figure 2a, disk arrays were transferred to the glass substrate after the fabrication process (more details about the fabrication process can be seen in our previous work [56] ).…”

All-optical control of high-purity trions in nanoscale waveguide

“…The TRPL traces are fitted by a biexponential function with fast (τ 1 ) and slow (τ 2 ) components [8]. Unlike previously reported plasmon-coupled platforms, which demonstrated dramatic decreases in lifetime [21][22][23], both components derived from the waveguide exhibit minimal changes in decay time compared with the ones from silicon. This is attributed to the strain gradient geometry, which can have higher electron densities even without being strongly coupled to the plasmon.…”