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1.
We consider the nonlinear terahertz emission by the system of cavity polaritons in the regime of polariton lasing. To account for the quantum nature of terahertz-polariton coupling, we use the Lindblad master equation approach and demonstrate that quantum microcavities reveal a rich variety of nonlinear phenomena in the terahertz range, including bistability, short terahertz pulse generation, and terahertz switching. 相似文献
2.
We review our recent results concerning surface-enhanced Raman scattering (SERS) by confined optical and surface optical phonons in semiconductor nanostructures including CdS, CuS, GaN, and ZnO nanocrystals, GaN and ZnO nanorods, and AlN nanowires. Enhancement of Raman scattering by confined optical phonons as well as appearance of new Raman modes with the frequencies different from those in ZnO bulk attributed to surface optical modes is observed in a series of nanostructures having different morphology located in the vicinity of metal nanoclusters (Ag, Au, and Pt). Assignment of surface optical modes is based on calculations performed in the frame of the dielectric continuum model. It is established that SERS by phonons has a resonant character. A maximal enhancement by optical phonons as high as 730 is achieved for CdS nanocrystals in double resonant conditions at the coincidence of laser energy with that of electronic transitions in semiconductor nanocrystals and localized surface plasmon resonance in metal nanoclusters. Even a higher enhancement is observed for SERS by surface optical modes in ZnO nanocrystals (above 104). Surface enhanced Raman scattering is used for studying phonon spectrum in nanocrystal ensembles with an ultra-low areal density on metal plasmonic nanostructures. 相似文献
3.
《Physics Reports》1999,321(6):253-305
Infrared spectroscopy on ultrafast time scales represents a powerful technique to investigate the nonequilibrium dynamics of elementary excitations in bulk and nanostructured semiconductors. In this article, recent progress in this field is reviewed. After a brief introduction into electronic excitations below the fundamental bandgap and ultrafast processes in semiconductors, infrared pulse generation and the methodology of time-resolved infrared spectroscopy are reviewed. The main part of this paper is devoted to coherent optical polarizations and nonequilibrium excitations of the electronic system in the spectral range below the fundamental band gap. The focus is on the physics of single component plasmas, i.e. electrons or holes. In particular, intraband, inter-valence and intersubband transitions are considered. Processes of phase relaxation, carrier and energy redistribution are analyzed. The potential of ultrafast infrared technology and spectroscopy for future applications is discussed in the final part. 相似文献
4.
Acoustic wave excitation of semiconductor quantum dots generates resonance fluorescence of electronic intersublevel excitations. Our theoretical analysis predicts acoustoluminescence, in particular, a conversion of acoustic into electromagnetic THz waves over a broad spectral range. 相似文献
5.
Received: 20 September 1998 / Revised version: 11 January 1999 相似文献
6.
A. M. Malyarevich K. V. Yumashev N. N. Posnov V. P. Mikhailov V. S. Gurin 《Journal of Applied Spectroscopy》2000,67(3):494-501
An investigation of the properties of CuFeS2 and CuFe2S3 nanoparticles with a different degree of surface oxidation was carried out. Oxidation leads to the appearance of an additional
absorption band with a maximum near 1.1 μm, which is assigned to metal-ligand-type transitions with charge transfer between
Cu atoms and their surroundings. Excitation of samples by picosecond laser pulses causes brightening of the additional absorption
band and induced absorption, associated with the absorption of their excited states, with two characteristic times of relaxation
of nonlinear-optical effects: τ1 = 70 ± 10 and 25 ± 5 psec for CuFeS2 and CuFe2S3 nanoparticles, respectively, and τ2>500 psec for both types of samples. The excitation and relaxation processes are explained on the basis of the proposed scheme
of energy levels.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 359–363, May–June, 2000. 相似文献
7.
Ultrafast electromagnetic waves radiated from semiconductor material under high electric fields and photoexcited by femtosecond laser pulses have been recorded by using terahertz time domain spectroscopy (THz-TDS).The waveforms of these electromagnetic waves reflect the dynamics of the photoexcited carriers in the semiconductor material,thus,THz-TDS provides a unique opportunity to observe directly the temporal and spatial evolutions of non-equilibrium transport of carriers within sub-picosecond time scale.... 相似文献
8.
Impurities play a pivotal role in semiconductors. One part in a million of phosphorous in silicon alters the conductivity
of the latter by several orders of magnitude. Indeed, the information age is possible only because of the unique role of shallow
impurities in semiconductors. Although work in semiconductor nanostructures (SN) has been in progress for the past two decades,
the role of impurities in them has been only sketchily studied. We outline theoretical approaches to the electronic structure
of shallow impurities in SN and discuss their limitations. We find that shallow levels undergo a SHADES (SHAllow-DEep-Shallow)
transition as the SN size is decreased. This occurs because of the combined effect of quantum confinement and reduced dielectric
constant in SN. Level splitting is pronounced and this can perhaps be probed by ESR and ENDOR techniques. Finally, we suggest
that a perusal of literature on (semiconductor) cluster calculations carried out 30 years ago would be useful.
相似文献
9.
范文慧 《中国光学快报(英文版)》2011,(11):40-45
An overview of the major techniques to generate and detect THz radiation so far,especially the major approaches to generate and detect coherent ultra-short THz pulses using ultra-short pulsed laser,has been presented.And also,this paper,in particularly,focuses on broadband THz spectroscopy and addresses on a number of issues relevant to generation and detection of broadband pulsed THz radiation as well as broadband time-domain THz spectroscopy (THz-TDS) with the help of ultra-short pulsed laser.The time-dom... 相似文献
10.
V. A. Gaisler 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(1):77-79
Single-photon emitters based on semiconductor quantum dots are briefly reviewed. A design of an single-photon electrically
driven emitter containing a single InAs quantum dot and a Bragg microcavity is analyzed. It is shown that the external quantum
efficiency of such emitters can be as high as 78%.
Original Russian Text ? V.A. Gaisler, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol.
73, No. 1, pp. 83–86. 相似文献
11.
We discuss near-field wave function imaging, introducing a model for high spatial resolution photoluminescence imaging of
semiconductor nanostructures. The model is applied to optically bright and dark exciton and biexciton states in different
quantum dot systems, explicitly taking the experimental imaging configuration into account. Our results show that direct imaging
of the exciton density is only possible in collection mode experiments with nonresonant excitation in the high-resolution
limit. For other geometries and for biexcitonic states, the images reflect not only the size and shape of the wave function
and the spatial resolution of the near-field probe but also in particular the inherent optical nonlinearity of the imaging
process. Different examples for the effects of this nonlinearity are discussed, providing new insight into the interpretation
of existing experiments, and guidelines for designing novel experiments.
PACS 78.67-n; 71.35.-y; 07.79.Fc 相似文献
12.
We theoretically show that spontaneously interlayer-coherent bilayer quantum Hall droplets should allow robust and fault-tolerant pseudospin quantum computation in semiconductor nanostructures with voltage-tuned external gates providing qubit control and a quantum Ising Hamiltonian providing qubit entanglement. Using a spin-boson model, we estimate decoherence to be small (approximately 10(-5)). 相似文献
13.
Soft chemistry has emerged as an important means of generating nanocrystals, nanowires and other nanostructures of semiconducting
materials. We describe the synthesis of CdS and other metal chalcogenide nanocrystals by a solvothermal route. We also describe
the synthesis of nanocrystals of AlN, GaN and InN by the reaction of hexamethyldisilazane with the corresponding metal chloride
or metal cupferronate under solvothermal conditions. Nanowires of Se and Te have been obtained by a self-seeding solution-based
method. A single source precursor based on urea complexes of metal chlorides gives rise to metal nitride nanocrystals, nanowires
and nanotubes. The liquidliquid interface provides an excellent medium for preparing single-crystalline films of metal chalcogenides. 相似文献
14.
The studies of the magnetic and electrical transport properties of ordered magnetic semiconductor nanostructures have been generalized. This new area lies at the intersection of nanotechnologies and fundamental problems of magnetism. The prospects for application of ferromagnetic semiconductors in spintronics have been discussed. A comparative analysis of the magnetic and electrical transport properties of nanowires, thin films, and bulk elemental semiconductors doped with transition metals has been performed. The influence of size effects on the spin dynamics, magnetization, and magnetoresistance of nanostructures has been considered. 相似文献
15.
We developed a Cherenkov phase-matching method for monochromatic THz-wave generation using the DFG, process with a lithium
niobate crystal, which resulted in both high conversion efficiency and wide tunability. Although THz-wave generation by Cherenkov
phase matching has been demonstrated using femtosecond pumping pulses, producing very high peak power, these THz-wave sources
are not monochromatic. Our method generates monochromatic and tunable THz, waves using a nanosecond pulsed laser source. We
also show that Cherenkov radiation with waveguide structure is an effective strategy for achieving extremely wide tunable
THz-wave source. We fabricated MgO-doped lithium niobate slab waveguide and demonstrated difference frequency generation of
THz-wave generation with Cherenkov phase matching. Extremely frequency-widened THz-wave generation, from 0.1 to 7 THz was
observed. 相似文献
16.
17.
Received: 14 April 1998/Accepted: 23 October 1998 相似文献
18.
Excitation of an n-type GaAs layer by intense ultrashort terahertz pulses causes coherent emission at 2 THz. Phase-resolved nonlinear propagation experiments show a picosecond decay of the emitted field, despite the ultrafast carrier-carrier scattering at a sample temperature of 300 K. While the linear THz response is in agreement with the Drude response of free electrons, the nonlinear response is dominated by the super-radiant decay of optically inverted impurity transitions. A quantum mechanical discrete state model using the potential of the disordered impurities accounts for all experimental observations. 相似文献
19.
We report Raman scattering results of wurtzite ZnS nanowires, nanocombs, and nanobelts. The Raman spectrum obtained from ZnS nanowires exhibits first‐order phonon modes at 272, 284, and 350 cm−1, corresponding to A1/E1 transverse optical, E2 transverse optical, and A1/E1 longitudinal optical phonons, respectively. Several multiphonon modes are also observed. The longitudinal optical phonon mode varies in wavenumber for nanocombs and nanobelts, indicating that the residual strain varies during the morphological change from ZnS nanowires to nanocombs and ultimately to nanobelts. Interestingly, a surface optical (SO) phonon mode varies in wavenumber depending on the shape and surface roughness of the ZnS nanostructures. The surface modulation wavelengths of the ZnS nanowires, nanocombs, and nanobelts are estimated using the SO phonon dispersion relations and the observed SO phonon wavenumbers. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
20.
K. Unterrainer R. Kersting R. Bratschitsch G. Strasser J. N. Heyman K. D. Maranowski A. C. Gossard 《Physica E: Low-dimensional Systems and Nanostructures》2000,7(3-4)
Optically excited plasma oscillations in n-doped GaAs epilayers emit intense THz pulses. Using a THz-pump and THz-probe technique we observe the response of the intersubband polarization in semiconductor quantum structures. THz Cross-correlation measurements of modulation doped semiconductor quantum structures allow to determine the absorption, the dispersion, and the dephasing times of the quantized electrons. 相似文献