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1.
W. Nomura T. Yatsui T. Kawazoe M. Naruse M. Ohtsu 《Applied physics. B, Lasers and optics》2010,100(1):181-187
The distribution dependency of quantum dots was theoretically and experimentally investigated with respect to the basic properties
optical excitation transfer via optical near-field interactions between quantum dots. The effects of three-dimensional structure
and arraying precision of quantum dots on the signal transfer performance were analyzed. In addition, the quantum dot distribution
dependency of the signal transfer performance was experimentally evaluated by using stacked CdSe quantum dots and an optical
near-field fiber probe tip laminated with quantum dots serving as an output terminal, showing good agreement with theory.
These results demonstrate the basic properties of signal transfer via optical near-field interactions and serve as guidelines
for a nanostructure design optimized to attain the desired signal transfer performances. 相似文献
2.
《Superlattices and Microstructures》1999,25(1-2):361-365
We present a theoretical study of optical second-harmonic generation(SHG) of symmetric semiconductor quantum dots (QDs) excited by the near field of the tip in a near-field scanning optical microscope. We show that the usual optical transition selection rules for the SH nonlinear interaction between the tip field and the QD are broken when the tip is scanned over the QD, because the tip field varies rapidly over the QD domain. It is also demonstrated that the tip-position dependence of the SH signal essentially maps the spatial distribution of the tip field. 相似文献
3.
J. Kolehmainen S.M. Reimann M. Koskinen M. Manninen 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):731-736
We study the magnetic coupling in artificial molecules composed of two and four laterally coupled quantum dots. The electronic
ground-state configurations of such systems are determined by applying current spin density functional theory which allows
to include effects of magnetic fields. While the ground-state of a two-dot molecule with strong enough inter-dot coupling
tends to be antiferromagnetic with respect to the spins of the single dot components, we find that a square lattice of four
dots has a ferromagnetic ground state.
Received 17 February 1999 and Received in final form 1 June 1999 相似文献
4.
We model the resonant excitation transfer between semiconductor quantum dots, accounting for the radiative nature of the electromagnetic field. The model based on Maxwell equations and on a non-local linear susceptibility accounts both for the instantaneous dipole–dipole coupling, decaying as R−3, and for retardation effects, decaying as R−1. The coupling is strongly resonant and its spatial range is of the order of the wavelength, due to the radiative nature of the retarded contribution. 相似文献
5.
Guenther T Lienau C Elsaesser T Glanemann M Axt VM Kuhn T Eshlaghi S Wieck AD 《Physical review letters》2002,89(5):057401
The nonlinear response of single GaAs quantum dots is studied in femtosecond near-field pump-probe experiments. At negative time delays, transient reflectivity spectra show pronounced oscillatory structure around the quantum dot exciton line, providing the first evidence for a perturbed free induction decay of the excitonic polarization. Phase-disturbing Coulomb interactions between the excitonic polarization and continuum excitations dominate the optical nonlinearity on ultrafast time scales. A theoretical analysis based on the semiconductor Bloch equations accounts for this behavior. 相似文献
6.
We performed time-resolved spectroscopy of ZnO quantum dots (QD), and observed exciton energy transfer and dissipation between
QD via an optical near-field interaction. Two different sizes of ZnO QD with resonant energy levels were mixed to test the
energy transfer and dissipation using time-resolved photoluminescence spectroscopy. The estimated energy transfer time was
144 ps. Furthermore, we demonstrated that the ratio of energy transfer between the resonant energy states could be controlled. 相似文献
7.
W. Nomura T. Yatsui T. Kawazoe M. Naruse E. Runge C. Lienau M. Ohtsu 《Applied physics. B, Lasers and optics》2012,107(2):257-262
This article reports the direct observation of long-distance optical excitation transfer based on resonant optical near-field interactions in randomly distributed quantum dots (QDs). We fabricated optical excitation transfer paths based on randomly distributed QDs by using CdSe/ZnS core?Cshell QDs and succeeded for the first time in obtaining output signals resulting from a unidirectional optical excitation transfer length of 2.4???m. Furthermore, we demonstrate that the optical excitation transfer occurs via the resonant excited levels of the QDs with a comparative experiment using non-resonant QDs. This excitation-transfer mechanism allows for intersecting, non-interacting nano-optical wires. 相似文献
8.
We show how a spin interaction between electrons localized in neighboring quantum dots can be induced and controlled optically. The coupling is generated via virtual excitation of delocalized excitons and provides an efficient coherent control of the spins. This quantum manipulation can be realized in the adiabatic limit and is robust against decoherence by spontaneous emission. Applications to the realization of quantum gates, scalable quantum computers, and to the control of magnetization in an array of charged dots are proposed. 相似文献
9.
K. Matsuda T. Matsumoto H. Saito K. Nishi T. Saiki 《Physica E: Low-dimensional Systems and Nanostructures》2000,7(3-4)
We study the variations of optical properties of self-assembled In0.5Ga0.5As single quantum dots (QDs) in the spatial and time domains by combining a near-field scanning optical microscope with an ultrafast pulsed laser. Through the examinations of several tens of QDs, we find that the variations of photoluminescence (PL) intensity strongly depend on the condition of the initial carrier creation. The differences in quantum efficiency and those in the carrier flow rate into QDs cause the large distribution of PL intensity when the carriers are excited in the barrier layers. From the results of time-resolved PL decay measurements, we find that there are two types of QDs exhibiting quite different PL decay profiles. 相似文献
10.
Joffre M 《Physical review letters》2003,90(13):139701; author reply 139702
11.
A. Chavez-Pirson J. Temmyo H. Ando 《Physica E: Low-dimensional Systems and Nanostructures》2000,7(3-4)
Near-field optical probing, or nanoprobing, achieves spatial resolution that surpasses the diffraction limit of light and makes possible the luminescence imaging and spectroscopy of single quantum dots in dense arrays of dots. We use optical nanoprobing to study self-organized InGaAs quantum dots grown on (3 1 1)B oriented GaAs substrates. Here, we emphasize a new feature of nanoprobing: pressure-induced strain modulation near the surface. Operating in near-field optical excitation–collection mode, the probe makes contact with the surface and exerts direct pressure whose main effect is a compressive uniaxial strain under the probe. By adjusting the applied pressure, we modulate the local strain environment in and around a quantum dot, but still preserve the capability to capture its near-field luminescence. Nanoprobe pressure effects modify the confinement potential and radiative emission of single quantum dots, and the coupling strength between dots. This opens new possibilities for the study and control of the optical and electronic properties of single- and coupled-quantum dots. 相似文献
12.
Network protocols are formulated for the phase-coding and correlated-photon-pairs quantum cryptosystems. These protocols are
free of the restriction imposed on the distance between the two legitimate users by the transmission loss in the optical fiber.
A single-photon source and a source of correlated photon pairs based on quantum dots are proposed.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 646–651 (25 April 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
13.
Semiconductor quantum dots are promising hosts for qubits to build a quantum processor. In the last twenty years, intensive researches have been carried out and diverse kinds of qubits based on different types of semiconductor quantum dots were developed. Recent advances prove high fidelity single and two qubit gates, and even prototype quantum algorithms.These breakthroughs motivate further research on realizing a fault tolerant quantum computer. In this paper we review the main principles of various semiconductor quantum dot based qubits and the latest associated experimental results. Finally the future trends of those qubits will be discussed. 相似文献
14.
Charge noise acting on graphene double quantum dots in circuit quantum electrodynamics architecture
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We investigate the dephasing mechanisms induced by the charge noise and microwave heating effect acting on a graphene double quantum dot(DQD) capacitively coupled to a microwave resonator. The charge noise is obtained from DC transport current, and its contribution to dephasing is simultaneously determined by the amplitude response of the microwave resonator. A lowfrequency 1/f-type noise is demonstrated to be the dominant factor of the dephasing of graphene DQD. Furthermore, when the applied microwave power is larger than-90 d Bm, the dephasing rate of graphene DQD increases rapidly with the increase of microwave power, and fluctuates slightly with the applied microwave power smaller than-90 d Bm. Our results can be applied to suppress the impeditive influence on the dephasing of graphene-based devices associated with microwave input in the perspective investigations. 相似文献
15.
T. Kawazoe K. Kobayashi K. Akahane M. Naruse N. Yamamoto M. Ohtsu 《Applied physics. B, Lasers and optics》2006,84(1-2):243-246
We propose and demonstrate the operation of a nanometric optical NOT gate using CuCl quantum dots coupled via an optical near-field
interaction. The device was smaller than 20 nm and its repeated operation was verified. The operating energy of this device
was much lower than that of a conventional photonic device. We also introduce all-optical NAND and NOR gates using coupled
quantum dots. Toward an actual nanophotonic device, we discuss the possibility of coupled InAlAs quantum dots. A double layer
of InAlAs quantum dots for nanophotonic device operation was prepared using molecular beam epitaxial growth. We obtained a
near-field spectroscopy signal, indicating that the InAlAs quantum dots coupled with the optical near field acted as a NOT
gate. The experimental results show that the sample has great potential as an actual nanophotonic device.
PACS 78.67.Hc; 07.79.Fc; 42.79.Ta 相似文献
16.
Zhi-Hai Zhang Bin Chen Rui-Zhen Wang Min-Wu Kang 《Physica B: Condensed Matter》2009,404(16):2332-2335
The optical rectification (OR) coefficient for cubical quantum dots (CQDs), with an applied electric field is theoretically investigated in the framework of the compact-density-matrix approach and an iterative method. The confined wave functions and energies of electrons in the CQDs are calculated in the effective-mass approximation. Numerical calculations are presented for typical GaAs/AlAs CQDs. The results show that the calculation for OR coefficient in the CQDs system can reach a magnitude of , two orders higher than that in the spherical quantum dots system. The OR coefficient strongly depends on the length of CQDs and the magnitude of electric field. And the peak shifts to the aspect of high energy when considering the electric field. 相似文献
17.
18.
U. Banin J.C. Lee A.A. Guzelian A.V. Kadavanich A.P. Alivisatos 《Superlattices and Microstructures》1997,22(4):559-568
The near band-gap level structure in high-quality colloidal InAs nanocrystal quantum dots within the very strong confinement regime is investigated. Size-selective photoluminescence excitation and fluorescence line narrowing measurements reveal a size-dependent splitting between the absorbing and the emitting states. The splitting is assigned to the confinement-enhanced electron–hole exchange interaction. The size dependence of the splitting significantly deviates from the idealized 1/r3scaling law for the exchange splitting. A model incorporating a finite barrier which allows for wavefunction leakage is introduced. The model reproduces the observed 1/r2dependence of the splitting and good agreement with the experimental data is obtained. The smaller barriers for embedded InAs dots grown by molecular-beam epitaxy, are predicted to result in smaller exchange splitting as compared with colloidal dots with a similar number of atoms. 相似文献
19.
20.
The exciton-longitudinal optical phonon interaction is theoretically investigated for the case of polar semiconductor cylindrical quantum dots embedded in semiconductor matrix. The theory is developed within the dielectric continuum model considering the Fröhlich interaction between electrons and confined bulk longitudinal optical phonons for a configurational interaction model of quantum dot. Representative longitudinal optical phonon mode for the exciton-phonon interaction is predicted for cylindrical InAs/GaAs quantum dots. 相似文献