共查询到20条相似文献,搜索用时 31 毫秒
1.
C. Voisin D. Christofilos N. Del Fatti F. Vallée 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):139-144
Femtosecond excitation and relaxation of nonequilibrium electrons are investigated in silver clusters using a two color pump-probe
technique with resonant excitation of the surface plasmon resonance and off resonant probing. The excitation process is shown
to be identical to that in metal films, and permits creation of a strongly athermal single electron excitation in a time scale
shorter than the duration of the pulses (25-30 fs), in agreement with the free-electron absorption model. Following the time
evolution of the nonequilibrium distribution yields information on the internal energy redistribution dynamics of the conduction
electrons and of its modification by confinement in metal clusters.
Received 1st December 2000 相似文献
2.
M.L. Ramón R. Meucci E. Allaria S. Boccaletti 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,12(2):329-337
Competition among modes in an annular CO2 laser has been experimentally and numerically analyzed. During the coexistence of different patterns, each of them resulting
from the interaction of two transverse modes with opposite angular momentum, chaos has been experimentally detected. A numerical
model, derived from the Maxwell-Bloch equations and including symmetry breaking terms, enables the interpretation of the main
experimental features.
Received 10 March 2000 相似文献
3.
Yu-Lin Gao Yi-Jun Lu Jian-Sheng Zheng Zhi-Gang Cai Hai-Yu Sang Xue-Ran Zeng 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):145-148
The time-resolved photoluminescence spectra of ordered and disordered Ga0.52In0.48P alloys were studied at room temperature and at 77 K liquid nitrogen, respectively. The ordered samples have well fitted
two exponential processes decay curves and the time constants are sample dependent and have little relationship with the ordering
degree. The decay curve of disordered sample shows that it has single exponential process and its lifetime has a tendency
of reduction with the decrease of excitation intensity. The photoluminescence spectra with different delay time at 77 K show
that the ordered samples exhibit about 6 ∼ 10 meV blue-shift of PL peak energy with the delay time.
Received 13 December 2001 Published online 19 July 2002 相似文献
4.
M.L. Ramón R. Meucci M. Ciofini A. Labate L. Calero 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(1):137-141
The formation and stabilization of spatio-temporal patterns in an annular CO2 laser is studied. We give experimental and numerical evidence of the role of a small spatial perturbation (consisting of
a thin metallic wire inserted in the optical cavity) in the selection and stabilization of patterns.
Received 15 December 1999 相似文献
5.
S. Zhu J. Fang X. Luo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):123-128
A linear array of three lasers that are coupled mutually in space is investigated. It is shown that the phase of the laser
fields is locked with intermediate coupling while the laser intensities are totally chaotic and chaotically synchronized.
When the intensities of lasers reenter the regime of chaotic synchronization at smaller coupling constant, the laser fields
show low degree of phase locking. The phase differences in the fields between three lasers show rich patterns when the coupling
is changed.
Received 3 August 2001 and Received in final form 27 September 2001 相似文献
6.
7.
We study theoretically the dynamical reorientation phenomena when a long-pitch cholesteric liquid-crystal film with homeotropic alignment is illuminated by a circularly polarized lightwave. In the present case, the natural cholesteric pitch is of the order of (or larger than) the film thickness. The helical cholesteric structure is thus frustrated by the boundary conditions without illumination. However, above a light intensity threshold reorientation occurs and the bifurcation scenario depends strongly on the natural cholesteric pitch. Recalling that a long-pitch cholesteric is achieved in practice by adding a small amount of chiral agents in a nematic liquid crystal, the observed dynamics can be viewed as the result of the competition between intrinsic and extrinsic unidimensional helical patterns. The intrinsic part consists of the helical deformations induced by the chirality of the dopant, whereas the extrinsic part is related to the chirality induced by the optical field through the non-uniform angular momentum transfer of light to a nematic. The all-optical analog in the case of a pure nematic (without chiral dopant), is also discussed. 相似文献
8.
M. Darwish 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(3):547-556
Theoretical investigations of dynamical behavior in optical
parametric oscillators (OPO) have generally assumed that the cavity
detunings of the interacting fields are controllable parameters.
However, OPOs are known to experience mode hops, where the system
jumps to the mode of lowest cavity detuning. We note that this
phenomenon significantly limits the range of accessible detunings
and thus may prevent instabilities predicted to occur above a
minimum detuning from being evidenced experimentally. As a simple
example among a number of instability mechanisms possibly affected
by this limitation, we discuss the Hopf bifurcation leading to
periodic behavior in the monomode mean-field model of a triply
resonant OPO and show that it probably can be observed only in very
specific setups. 相似文献
9.
L. K. Jha S. Kumar B. N. Roy 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(1):101-106
Stable two-mode, and three-mode oscillations due to the spatial hole burning
effect were observed experimentally with the increase of the pump power
ratio in a laser-diode pumped sub-nanosecond microchip Cr,Yb:YAG
self-Q-switched multimode laser. The stability of the output pulse trains
was attributed to the mode coupling through antiphase dynamics between
different modes. Modified multimode rate equations including the spatial
hole-burning effect in the active medium and the non-linear absorption of
the saturable absorber were proposed. Numerical simulations of the antiphase
dynamics of such a laser were in good agreement with the experimental data,
and the antiphase dynamics were explained by the evolution of the inversion
population and the bleaching and recovery of the inversion population of the
saturable absorber. 相似文献
10.
We show theoretically that thermomechanical effects in dye-doped nematic liquid crystals when illuminated by laser beams,
can become important and lead to molecular reorientation at intensities substantially lower than that needed for optical Fréedericksz
transition. We propose a 1D model that assumes homogenous intensity distribution in the plane of the layer and is capable
to describe such a thermally induced threshold lowering. We consider a particular geometry, with a linearly polarized light
incident perpendicularly on a layer of homeotropically aligned dye-doped nematics. 相似文献
11.
C. Giannetti G. Ferrini S. Pagliara G. Galimberti F. Banfi E. Pedersoli F. Parmigiani 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):121-125
The non-linear photoelectron spectra obtained by short
laser pulses from a Ag(100) surface show a high-energy electron
emission due to an athermal electron distribution created by the
laser pulse. By comparing the photoemission at normal and
non-normal emission geometry it is possible to evidence the
independence of the hot electron photoemission on the parallel
momentum and on different final-state configurations. A
photoemission correlation measurement evidences that
non-photoelectric effects, as tunneling or thermally assisted
photoemission, do not contribute to the electron yield. Various
theoretical models are discussed on the basis of the present
data. 相似文献
12.
M.W. Wu C.Z. Ning 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):373-376
A new spin dephasing mechanism is proposed for semiconductors with carrier momentum-dependent transition energies (inhomogeneous
broadening) between spin states. In the presence of this inhomogeneous broadening of the spin transitions, spin-conserving
(SC) scatterings lead to irreversible spin dephasing in a complete analogy to the optical dephasing of inhomogeneously broadened
optical transitions. This phenomenon is demonstrated for the case when the g-factor becomes electron-energy dependent.
Received 29 June 2000 相似文献
13.
S. S. Hassan H. A. Batarfi R. Saunders R. K. Bullough 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(3):403-416
A time-independent theoretical and numerical analysis of an optical bistable model of two-level atoms in a ring cavity, driven
by a coherent field and in contact with a squeezed vacuum field is presented in the two cases of absorptive and dispersive
optical bistability (OB). In the former case, a suitable choice of the phase of the squeezed vacuum field reduces the threshold
for OB to occur compared with the normal vacuum case. In the latter case, regions of OB are identified as one or two disconnected
simple closed curves depending on the cooperation parameter [0pt] : is the maximum possible value of the critical value of C at fixed values of the squeezed vacuum field parameters. Phase switching effects between different (output) states of the
system is investigated in detail. In the absorptive case, one- or two-way optical switching is possible depending on [0pt]
. We also present results which demonstrate more complicated switching behaviour in the dispersive case.
Received 12 March 1999 and Received in final form 20 August 1999 相似文献
14.
K. Mahmoud Aghdami F. Prati P. Caccia G. Tissoni L. A. Lugiato R. Kheradmand H. Tajalli 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(3):447-455
We compare three different switching techniques for the control of cavity solitons in a VCSEL-based cavity soliton laser,
one
incoherent and the other two semicoherent with different injection
frequencies. We show that the switching dynamics and energies can be
very different depending on the type of injection. 相似文献
15.
P. Foggi P. Bartolini M. Bellini M.G. Giorgini A. Morresi P. Sassi R.S. Cataliotti 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):143-151
The relaxation dynamics of pure acetonitrile isotopomers has been investigated in the temperature range 8 to 75 °
C. The overall response of the liquid is measured either recording directly the decay of the optical Kerr signal with heterodyne
detection (OHD-OKE) and Fourier transforming the depolarized Rayleigh scattering spectra (DRS). The OHD-OKE signals show a
decay that can be described by a bi-exponential law. At some temperatures, stressing to a maximum level the sensitivity of
the OHD-OKE experimental set-up, a damped oscillation is observed on top of the fast decay component. The two techniques provide
same results with a high level of reproducibility, as far as the slow component is concerned. This latter is described by
an exponential law with the time constants ranging in the interval 2.0 to 0.85 ps in the light and approximately in the same
interval in the deuterated molecule. The decays are, at all temperatures, well reproduced by the extended diffusion J-model. The fast component, better observed with the OHD-OKE experiments in a restricted temperature range, has time constants
ranging from 550 to 350 fs. After the subtraction of the curve due to the slower decay component, the data have also been
analyzed by Fourier transforming the fast part of the decay. The spectrum then consists of a broad (approximately 80 cm-1 wide) band centered at 50 cm-1. This band is interpreted as the manifestation of intermolecular vibrational motions.
Received 21 July 2002 Published online 1st October 2002
RID="a"
ID="a"e-mail: foggi@colonnello.lens.unifi.it 相似文献
16.
The pulse shape of a passively Q-switched microchip laser 总被引:2,自引:0,他引:2
T. Erneux P. Peterson A. Gavrielides 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(3):423-431
The shape of the intensity pulse of a passively Q-switched microchip laser is investigated numerically and analytically. Our
analysis is motivated by independent microchip laser experiments exhibiting nearly symmetric pulses in the case of a semiconductor
saturable absorber and asymmetric pulses in the case of a solid state saturable absorber. Asymptotic methods are used to determine
limiting behaviors of the pulse shape for both symmetric and asymmetric pulses. In the first case, we determine a sech2 solution parametrized by one parameter which can be determined by solving two coupled nonlinear algebraic equations. In the
second case, the pulse solution is decomposed into two distinct approximations exhibiting different amplitude and time scales
properties. We review earlier approximations of the repetition rate and the pulse width.
Received 2 August 1999 相似文献
17.
J. Bellessa V. Voliotis T. Guillet D. Roditchev R. Grousson X.L. Wang M. Ogura 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(4):499-505
We report on time-resolved microphotoluminescence experiments in a single GaAs/GaAlAs V-shaped quantum wire as a function
of optical excitation intensity. At low pump power we observe that excitons are localized in quantum boxes formed by the local
potential minima existing along the wire axis. As the pump power is increased, state filling of the lowest lying levels of
the boxes appears. When two carriers occupy the first excited level of the box, a very efficient Auger scattering occurs,
leading to a transfer of carriers from one box to another neighbouring one. The intradot Auger scattering time has been measured
and is of the same order of magnitude as the LA-phonon emission rate.
Received 5 February 2001 相似文献
18.
U. Hohenester P. Kocevar N.E. Hecker R. Rodrigues-Herzog 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(1):143-152
We present a systematic study of the dependence of the energy relaxation of photo-excited minority electrons on the doping
concentration in highly p-doped GaAs. A nonmonotonic dependence is found in the region where the characteristics of the carrier-carrier interaction
changes from plasmon-mediated to quasistatically screened. Using a detailed Monte-Carlo study we are able to attribute this
observation to a general property of plasmas at high density.
Received: 1st April 1998 / Revised: 6 May 1998 /
Accepted: 18 May 1998 相似文献
19.
M. Hoyuelos G.-L. Oppo P. Colet M. San Miguel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):441-451
We analyze the quantum fluctuations of the degenerate optical parametric oscillator close to an instability for the formation
of a square pattern. While strong correlations between the fluctuations of the signal modes emitted at the critical wave number
and with opposite wave vector are present both below and above threshold, no features signaling the square character of the
pattern forming above threshold have been identified below threshold in the spatio-temporal second-order coherence. We also
explore in which regimes a reduced few mode model gives meaningful results.
Received 17 September 2002 / Received in final form 11 November 2002 Published online 26 February 2003 相似文献
20.
L. Wu S. Zhu Y. Ni 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):349-354
Combination of two basic types of synchronization, anticipatory
synchronization and lagged synchronization, is investigated
numerically between two coupled semiconductor lasers. It is found
that lagged synchronization produced by a backward coupling with a
suitable delay can combine with the originally hidden anticipatory
synchronization and produce a type of synchronization overcoming the
original lagged synchronization produced by a forward coupling. We
study the combination synchronization phenomenon when the delay of
the backward coupling is different from that of the original
anticipatory synchronization. Our results suggest that the
synchronization combination phenomenon might allow an interpretation
of an experimental observation by Sivaprakasam et al. [Phys.
Rev. Lett. 87, 154101 (2001)] that the anticipating time is
irrespective of the external-cavity round trip time, which to date remains to be understood. 相似文献