Polarized resonant emission of monolayer WS2 coupled with plasmonic sawtooth nanoslit array

Abstract

Transition metal dichalcogenide (TMDC) monolayers have enabled important applications in light emitting devices and integrated nanophotonics because of the direct bandgap, spinvalley locking and highly tunable excitonic properties. Nevertheless, the photoluminescence polarization is almost random at room temperature due to the valley decoherence. Here, we show the room temperature control of the polarization states of the excitonic emission by integrating WS 2 monolayers with a delicately designed metasurface, i.e. a silver sawtooth nanoslit array. The random polarization is transformed to linear when WS 2 excitons couple with the anisotropic resonant transmission modes that arise from the surface plasmon resonance in the metallic nanostructure. The coupling is found to enhance the valley coherence that contributes to~30% of the total linear dichroism. Further modulating the transmission modes by optimizing metasurfaces, the total linear dichroism of the plasmonexciton hybrid system can approach 80%, which prompts the development of photonic devices based on TMDCs.

Deep subwavelength control of valley polarized cathodoluminescence in h-BN/WSe2/h-BN heterostructure

“…Furthermore, the Au nanoantenna placed in the vicinity of WSe 2 monolayer can induce the Purcell effect and lead to a faster recombination rate of valley excitons, which also contributes to the observed valley polarized signals at room temperature. Intriguingly, besides valley polarization, the valley coherence 21 , 22 may also be generated by linearly polarized dipole mode, excited by electron-beam impinging at the middle left and the top middle positions of Au nanoantenna, with the dipole oscillated horizontally along the long side and vertically along the short side. The emitted CL signal of WSe 2 monolayer may be linearly polarized, paralleled to the orientation of linearly polarized excitation.…”

“…Moreover, WSe 2 monolayer has stronger spin–orbit coupling (~0.46 eV) compared with MoS 2 (~0.15 eV) 19 , namely it has potential to possess long-lived valley polarization, demonstrating that WSe 2 is a prominent material for valleytronics and quantum information transport. Valley-dependent photonics phenomena in WSe 2 have also been studied, such as spin–layer locking effect 20 , valley coherence 21 , 22 , and holes valley polarization 23 . Recently, the lightwave valleytronics in WSe 2 monolayer is reported 24 , showing the lightwave-induced change of the valley pseudospin which provides a method for fast control of electrons at the fundamental quantum level.…”

Linearly Polarized Electroluminescence from MoS2 Monolayers Deposited on Metal Nanoparticles: Toward Tunable Room‐Temperature Single‐Photon Sources

“…This process is quite distinct from previous approaches based merely on enhancing the radiative rate of the A‐exciton, that is, on lowering τ A , to generate signatures of valley coherence in PL under resonant optical excitation. [ 20,54,55 ]…”

Modified Absorption and Emission Properties Leading to Intriguing Applications in Plasmonic–Excitonic Nanostructures

“…WS 2 nanostructures also shows highly polarization‐controlled PL enhancement when coupled to silver nanoarrays resulting from strong plasmon–exciton coupling. [ 309 ] Additionally, various substrates can also significantly influence fluorescence intensity. The plasmonic properties of Au nanostructures on various metal oxide surfaces covered with CdSe/ZnS QDs has been studied and PL response is shown in Figure 15g.…”