Strong anisotropic enhancement of photoluminescence in WS2 integrated with plasmonic nanowire array

Abstract

Layered transition metal dichalcogenides (TMDCs) have shown great potential for a wide range of applications in photonics and optoelectronics. Nevertheless, valley decoherence severely randomizes its polarization which is important to a light emitter. Plasmonic metasurface with a unique way to manipulate the light-matter interaction may provide an effective and practical solution. Here by integrating TMDCs with plasmonic nanowire arrays, we demonstrate strong anisotropic enhancement of the excitonic emission at different spectral positions. For the indirect bandgap transition in bilayer WS2, multifold enhancement can be achieved with the photoluminescence (PL) polarization either perpendicular or parallel to the long axis of nanowires, which arises from the coupling of WS2 with localized or guided plasmon modes, respectively. Moreover, PL of high linearity is obtained in the direct bandgap transition benefiting from, in addition to the plasmonic enhancement, the directional diffraction scattering of nanowire arrays. Our method with enhanced PL intensity contrasts to the conventional form-birefringence based on the aspect ratio of nanowire arrays where the intensity loss is remarkable. Our results provide a prototypical plasmon-exciton hybrid system for anisotropic enhancement of the PL at the nanoscale, enabling simultaneous control of the intensity, polarization and wavelength toward practical ultrathin photonic devices based on TMDCs.

Strong Linearly Polarized Emission from Monolayer WS2 Coupled with Plasmonic Nanocavity Array

“…For the CdSe‐NGs structure in the weak coupling regime, the exciton relaxation path γ x dominates the coherent relaxation process. Plasmon‐induced Purcell effect increases the electron–hole recombination rate but their phase relation still does not cohere before they decay to photons since γ co = γ x ≪ γ de , [ 48 ] as a result their valley coherence will diminish at room temperature and linear polarization is contributed just from anisotropic plasmon‐enhanced excitation. However, by the formation of polariton in the WS 2 ‐NGs structure, the coherent relaxation process can be significantly accelerated because it will obtain an extra plasmon relaxation path γ p which is comparable with the decoherence rate.…”

Multilayer WS2 for low-power visible and near-infrared phototransistors

“…The 1.3 eV bandgap of the bulk widens up to 2.1 eV in the monolayer [ 32 ] and a transition from indirect to direct bandgap is observed [ 33 ]. The direct bandgap enhances the photoluminescence (PL) that in the monolayer is more than three orders of magnitude stronger than in the bulk [ 34 , 35 ]. Conversely, multilayer WS 2 is advantageous for photodetection due to increased optical absorption and carrier mobility [ 36 ].…”

Probing the chirality and optical activity of organic molecules through the anisotropic photoluminescence of porous silicon

“…23 This technique has been used in the development of new applications for chiral molecules, such as in novel drugs, analytical chemistry, and materials science. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] The importance of studying the PL anisotropy of porous silicon (PSi) has been highlighted in previous research studies. [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] The heterogeneous nature of the mesoporous structure of PSi causes variations in its optical characteristics along different directions; these variations are manifested in FA.…”

“…23 This technique has been used in the development of new applications for chiral molecules, such as in novel drugs, analytical chemistry, and materials science. 24–38…”