We have observed a multimode spectrum of magnetoplasmons in the Hall bars processed on a high electron mobility GaAs/AlGaAs heterostructure. We have found that the dispersion relation of these excitation follows square root dependence. Calculated wavelength of the fundamental magnetoplasmon mode fits to the width of sample.
This paper reports a study on the surface plasmon effect of Ag nanoplates on electroluminescent property of polymer light emitting diodes. The diode is a single layer light emitting device made of poly [9,9-di-(2-ethylhexyl)-fluorenyl-2,7-diyl] (PEHF). 5 wt.% of Ag nanoplates were incorporated into the PEHF layer. The results showed that the electroluminescence intensity of the diodes is increased by 51.85%, compared with the device without the Ag nanoplates. The enhancement is due to the coupling process between the Ag surface plasmon with the emission light from the PEHF. The occurrence of the coupling process was proved firstly based on the fact that the exciton lifetime of the PEHF:Ag layer is shorter than that without Ag, as measured by time-resolved photoluminescence spectroscopy. Secondly, the PEHF photoluminescence peak at 425 nm is overlaping with the surface plasmon absorption peak of Ag nanoplates.
The paper deals with investigations concerning the plasmon resonance in an optical planar waveguide structure, applied in the construction of sensors with spectral detection. The surface plasmons in a multi-layer planar structure (with complex refractive indices) have been described, as well as the way of numerical solutions of physical equations describing the propagating electromagnetic field in such structures. The physical interpretation of obtained results has been presented, too.
The paper presents the results of experimental investigations concerning the plasmon resonance in a planar waveguide structure applied in the construction of sensors with spectral detection.
The paper presents the results of numerical investigations of the phenomenon of plasmon resonance in a planar waveguide structure, applied in the construction of sensor with spectral detection.
Field-effect transistors are nowadays considered as possible elements of THz detection and emission systems. Their THz performance is governed by excitations of two-dimensional plasma in the transistor channel. The paper discusses peculiarities of the photon-plasmon coupling mechanism in field-effect transistors and puts it in the perspective of classical investigation of plasma excitations in two-dimensional systems.
Influence of Al concentration on the energy loss spectrum of the substrate was observed. Also the dependences of the loss amplitude and energy on the primary energy and the layer thickness were studied.
A photoresponse at THz frequencies of a quantum point contact fabricated on a CdTe/CdMgTe quantum well was studied at low temperatures as a function of magnetic field. The spectra show a structure which was interpreted as resulting from the cyclotron resonance and magnetoplasmon excitations. The wavelength of the fundamental magnetoplasmon mode was found to be about 2 μm which coincides with one of dimensions of the point contact. We also discuss the possibility of coupling of magnetoplasmon modes to shallow impurity transitions in the quantum well.
Size effect for plasmon resonance in metallic nanoparticles has been studied by finite element method solution of the Maxwell equations (COMSOL), by the Mie approach and microscopic random phase approximation model. Comparison with Au, Ag nanoparticles experimental data for light extinction in colloidal solutions with different particle sizes is presented for the three types of approach.
In the photoluminescence excitation spectra of two-dimensional valence holes with large spin gap and strong disorder we find evidence for quantum Hall ferromagnetism and small skyrmions around the Landau level filling factorν=1. This interpretation is supported by numerical calculations.
Intersubband plasma excitation spectrum of lateral multiwire superlattices is investigated theoretically within the random-phase approximation. We examine the role of an interwire electron-electron interaction in regard to the depolarization shift.
Positively charged excitons in a two-dimensional hole gas in symmetric and asymmetric GaAs/Ga_{1-x}Al_{x}As quantum wells are studied in polarization-resolved photoluminescence experiments in high magnetic fields B (up to 23 T) and low temperatures (down to 300 mK). The experiments are accompanied by numerical calculations of a real structure. The whole family of trions (the singlet and a pair of triplets) are observed. The Coulomb energies crossing of singlet and triplet is found: hidden in symmetric and visible in asymmetric structures.
Terahertz emission from the electron-hole plasma excited by a femtosecond optical pulse in GaAs-based emitters is studied by the Monte Carlo simulations. The THz energy radiated from the n- and p-doped GaAs surface THz emitters, from the contactless p-i-n emitter, and from the photoconductive emitter is evaluated. The obtained results show that the THz energy radiated by the photoconductive emitter exceeds the energy radiated by the surface and p-i-n THz emitters by more than one order of magnitude.
We theoretically investigate dynamics of excitation in a hybrid nanostructure comprising a photosynthetic complex peridinin-chlorophyll-protein (PCP) coupled to a gold spherical nanoparticle. Our model includes the analytical description of radiative and non-radiative relaxation channels of the chlorophylls in PCP, as well as the change of energy transfer rate within the PCP due to the presence of metal scatterer. We show that by measuring the intensity of fluorescence from selectively excited chlorophyll molecules in the PCP complex, elementary geometric properties of the system can be deduced.
Hybrid molecules formed by coupling semiconductor quantum dots to metal nanoparticle nanoantennas provide a new paradigm for directed nanoscale transfer of quantum information. To assess this possibility, we study theoretically the response of these hybrid molecules to applied optical fields. Quantum-coherent time-evolution of the semiconductor quantum dots in the hybrid molecule is found by solving the semiconductor quantum dot density matrix equations. We study hybrid molecules in the weak and strong coupling regimes. In strongly driven, strongly dipole-coupled semiconductor quantum dot-metal nanoparticle hybrids with spherical metal nanoparticles, interference, dispersion near resonance and self interaction define the metal nanoparticle/semiconductor quantum dot coupling and lead to the Fano resonances, exciton induced transparency, suppressed semiconductor quantum dot response and bistability. More complicated response can be tailored by using metal nanoparticle shape and the placement of semiconductor quantum dots to control the local near-fields that couple the metal nanoparticles and semiconductor quantum dots. We describe how coupling to metal nanoparticle dark modes and higher order multipolar modes impact interference and self-interaction effects. The physics of the metal nanoparticle/semiconductor quantum dot coupling is outlined.
In magneto-photoluminescence spectra of a two-dimensional hole gas in a GaAs quantum well we observe coupling of two different radiative states. The pair of coupled states are an acceptor-bound trion AX^{+} and an essentially free (only weakly localized by a shallow lateral potential) trion X^{+}, brought into resonance by an additional cyclotron excitation controlled by the magnetic field. The coupling mechanism is the exciton transfer, and the optical signature is a clear anticrossing of the emission lines of an X^{+} and a cyclotron replica of the AX^{+}.
Plasma excitations in metallic n-type GaAs are studied in high-magnetic fields using the method of inelastic light scattering (the Raman scattering). Experimental data are analyzed using a standard, dielectric function theory. The results obtained for samples with a high electron concentration are well understood in terms of longitudinal excitations. A strong interaction of coupled longitudinal optical-phonon-plasmon modes with the collective cyclotron resonance excitations (the Bernstein modes) is observed. In samples with a lower electron concentration, the unexpected feature in the vicinity of the undressed optical phonon is observed at high magnetic fields. This effect is explained in terms of transverse excitations, which would appear in the Raman spectrum due to disorder-activated selection-rule breaking. A field induced metal-insulator transition and magnetopolaron effect on shallow donors in GaAs is shown to be traced with the Raman scattering experiments in samples with the lowest electron concentration.
Ferromagnetic resonance was employed to study the magnetic anisotropy of the Fe thin film in the MgO/Cu(t_{Cu})/Fe/Cu system. The Fe film showed strong fourfold cubic anisotropy (H_{K_{1}} = 2K_{1}/M = 46.15 kA/m) for t_{Fe} = 23 nm and t_{Cu} = 0. The spread of the crystallographic axes Δβ = 0.5° was evaluated from the angular dependence of the resonance line width ΔH_{pp} (4.4 < ΔH_{pp} < 6.4 kA/m). Such a small mosaicity confirmed the epitaxial growth of the Fe film. The Cu buffer layer destroys this growth of the Fe film which showed only a weak anisotropy.
We have investigated the properties of structures incorporating graded index materials with parabolic permittivity profile. Surface-plasmon-polaritons at the interface of graded index material and semiconductor are studied by means of numerical simulations. We analyze the dependence of the dispersion characteristics on the graded index material profile as well as on the semiconductor concentration via the finite-difference time-domain simulations. Effects of the structure on dielectric and magnetic properties are taken into account by introducing the Drude model in the semiconductor dispersion.
Properties of excitons in quantum well structures of ZnCdSe/ZnSe and ZnSe/ZnMgSSe are compared. In ternary ZnCdSe quantum wells and at low temperature excitons are strongly localised. Weaker localization is observed in quantum well structures of ZnSe/ZnMgSSe. Present studies suggest formation of negatively charged excitons in the latter structures.
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