Enhancement of second harmonic generation in a layered MoS2 nanoresonator

Molybdenum disulfide (MoS2) is a layered material with a high refractive index in the visible and infrared spectral range. In this work, we theoretically and experimentally demonstrate Mie-resonant MoS2 nanodisks. We show enhanced second harmonic generation from MoS2 nanodisk resonators due to the overlap of Mie-type resonances at the fundamental wavelength with the C-exciton resonance at the second-harmonic wavelength.

Giant Photoluminescence Enhancement and Carrier Dynamics in MoS2 Bilayers with Anomalous Interlayer Coupling

Fundamental researches and explorations based on transition metal dichalcogenides (TMDCs) mainly focus on their monolayer counterparts, where optical densities are limited owing to the atomic monolayer thickness. Photoluminescence (PL) yield in bilayer TMDCs is much suppressed owing to indirect-bandgap properties. Here, optical properties are explored in artificially twisted bilayers of molybdenum disulfide (MoS2). Anomalous interlayer coupling and resultant giant PL enhancement are firstly observed in MoS2 bilayers, related to the suspension of the top layer material and independent of twisted angle. Moreover, carrier dynamics in MoS2 bilayers with anomalous interlayer coupling are revealed with pump-probe measurements, and the secondary rising behavior in pump-probe signal of B-exciton resonance, originating from valley depolarization of A-exciton, is firstly reported and discussed in this work. These results lay the groundwork for future advancement and applications beyond TMDCs monolayers.

Study of the Scattering-To-Absorption Ratio in Plasmonic Nanoparicles ‎for‎ Photovoltaic Cells and Sensors Applications

In this paper‎, ‎the scattering-to-absorption ratio that is a measurable factor and defined as the ratio of the scattering cross section to the absorption cross section in plasmonic core-shell nanoparticles with different shapes is investigated‎. ‎The effect of various plasmonic materials on ‎the scattering-to-absorption ratio is presented that can play a key role in plasmonic solar cell efficiency improvement‎. In addition to using plasmonic materials as silver and gold, we use poor metals as bismuth because this type of metals are good materials for UV plasmonics. We also use semiconductor copper chloride (CuCl) in our calculations, because this material exhibits a strong exciton resonance, while the interaction between the plasmon resonance in metals and the exciton resonance in CuCl leads to new plexcitonic modes.

Нетривиальная зависимость спектральных характеристик экситонов в квантовых ямах от мощности резонансного оптического возбуждения

Basic exciton parameters, the energy of exciton transition and the radiative and nonradiative broadenings, are experimentally studied by means of reflectance spectroscopy for a heterostructure with the 14-nm GaAs/AlGaAs quantum well. Particular attention is paid to the nonradiative broadening which is sensitive to optical creation of free carriers and long-lived nonradiative excitons. A sublinear increase of the broadening of the heavy-hole and light-hole exciton resonances is observed when the light-hole exciton resonance is excited with increasing power. A simple model is developed, which allows one to well reproduce the observed dependence.

Топологические моды в неэрмитовых фононных кристаллах, индуцированных оптически в массиве квантовых ям

We study theoretically propagation of acoustic waves in an array of quantum wells, where a spatially modulated amplification and attenuation of sound is realized by optical excitation with a frequency close to the exciton resonance. The dispersion of sound waves near Bragg resonances corresponding to the modulation wave vector is calculated. The appearance of "imaginary" stop bands, where the imaginary parts of the Bloch mode frequencies are split, is described. The emergence of acoustic topological modes at the edge of the structure is demonstrated.

Towards Exciton-Polaritons in an Individual MoS2 Nanotube

We measure low-temperature micro-photoluminescence spectra along a MoS 2 nanotube, which exhibit the peaks of the optical whispering gallery modes below the exciton resonance. The energy fluctuation and width of these peaks are determined by the changes of the nanotube wall thickness and propagation of the optical modes along the nanotube axis, respectively. We demonstrate the potential of the high-quality nanotubes for realization of the strong coupling between exciton and optical modes when the Rabi splitting can reach 400 meV. We show how the formation of exciton-polaritons in such structures will be manifested in the micro-photoluminescence spectra and analyze the conditions needed to realize that.

Свойства микрорезонатора на основе таммовского плазмона с внутрирезонаторными металлическими слоями и органической активной областью

A theoretical study of the properties of a microcavity structure with intracavity metal layers and an organic active region (material CBP(4,4′-Bis(N-carbazolyl)-1,1′-biphenyl)) was done. The structure consisted of a layer of organic material CBP, sandwiched between two silver layers, thin phase matching layers (dph=26 nm) and two quarter-wave Bragg reflectors. It was shown that hybrid modes localized in the central layer of the structure can significantly increase the decay rate of the luminescence of an organic emitter by means of the Purcell effect. A shift in the hybrid modes spectral position was shown upon their interaction with the exciton resonance in CBP. This fact may indicate the appearance of a strong coupling regime.