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.
Highlights
Layered transition metal dichalcogenides (TMDCs) have shown great potential for a wide range of applications in photonics and optoelectronics
Our results demonstrate the unique anisotropic light-matter interactions in a highly confined TMDC-metasurface device, which offer the possibility of manipulating the intensity, polarization, and wavelength of the scattered light in one single device and provide guidelines for establishing the ultrathin optical devices with multi-functionalities
The highly confined metasurface-TMDCs hybrid systems provide a new route toward the emerging flat optics, where the intensity, polarization and wavelength of light can be tuned by tailoring the direction and magnitude of the plasmon-exciton coupling
Summary
Layered transition metal dichalcogenides (TMDCs) have shown great potential for a wide range of applications in photonics and optoelectronics. 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. Two-dimensional semiconducting transition metal dichalcogenides (TMDCs) have recently attracted considerable interest because of tunable bandgap, tightly bound excitons, and highly tunable excitonic p roperties[1], enabling applications in various photonic and optoelectronic devices ranging from infrared to visible spectra, such as light-emitting diodes2–4, photodetectors5,6, photovoltaics7, modulators[8,9], nanoscale quantum d evices[10,11,12], etc. To recover the valley coherence, resonant nanocavities have been proposed to either generate exciton–polariton quasiparticles[21,22] or accelerate the electron–hole recombination rate to surpass quantum decoherence[12] Despite these efforts, it remains difficult to achieve a strong PL signal with high linearity and conventional polarizers that are bulky and of high losses are still in use. Our results demonstrate the unique anisotropic light-matter interactions in a highly confined TMDC-metasurface device, which offer the possibility of manipulating the intensity, polarization, and wavelength of the scattered light in one single device and provide guidelines for establishing the ultrathin optical devices with multi-functionalities
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