共查询到20条相似文献,搜索用时 646 毫秒
1.
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
2.
Distribution of eigenfrequencies for vibrating plates 总被引:2,自引:0,他引:2
P. Bertelsen C. Ellegaard E. Hugues 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):87-96
Acoustic spectra of free plates with a chaotic billiard shape have been measured, and all resonance frequencies in the range
0-500 kHz have been identified. The spectral fluctuations are analyzed and compared to predictions of the Gaussian Orthogonal
Ensemble (GOE) of random matrices. The best agreement is found with a superposition of two independent GOE spectra with equal
density which indicates that two types of eigenmodes contribute to the same extent. To explain and predict these results a
detailed theoretical analysis is carried out below the first cut-off frequency where only flexural and in-plane vibrations
are possible. Using three-dimensional plate dispersion relations and two-dimensional models for flexural and in-plane vibrations
we obtained two first terms of the asymptotic expansion of the counting function of these eigenmodes. The contribution of
edge modes is also discussed. The results are in a very good agreement with the experimentally measured number of modes. The
analysis shows that the two types of modes have almost equal level density in the measured frequency interval, and this explains
the observed spectral statistics. For a plate with broken symmetry in the up-down direction (where flexural and in-plane modes
are strongly coupled) experimentally observed spectral fluctuations correspond to a single GOE spectrum. Above the first cut-off
frequency a greater complexity of the spectral fluctuations is expected since a larger number of types of modes will contribute
to the spectrum.
Received 5 January 1999 and Received in final form 5 September 1999 相似文献
3.
J. Peřina Jr. 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(2):235-242
The dependence of one- and two-photon characteristics of pulsed entangled two-photon fields generated in spontaneous parametric
down-conversion on the pump-pulse properties (shape of the pump-pulse spectrum and its internal structure) is examined. It
is shown that entangled two-photon fields with defined properties can be generated. A general relation between the spectra
of the down-converted fields is established. As a special case the interference of two partially overlapping pulsed two-photon
fields is studied. The fourth-order interference pattern of entangled two-photon fields is investigated in the polarization
analog of the Hong-Ou-Mandel interferometer.
Received: 23 December 1998 / Received in final form: 14 April 1999 相似文献
4.
E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(3):423-431
Several examples of photon entanglement are studied in the Q representation of quantum optics. In particular, the entangled states produced in parametric downconversion are studied in
detail, and we determine the conditions for the violation of Bell's inequality. Our approach shows that photon entanglement
is related to the existence of correlations between the quantum fluctuations of the electromagnetic field associated to different
modes.
Received 10 August 2002 / Received in final form 7 November 2002 Published online 4 February 2003 相似文献
5.
C. Szwaj G.-L. Oppo A. Gatti L.A. Lugiato 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(3):433-448
Quantum images, that is inhomogeneous field distributions purely generated by quantum fluctuations, persist when passing from
the degenerate to the non-degenerate case of optical parametric oscillators (OPO). Below the threshold for parametric oscillation
where the near-field distributions are homogeneous both in intensity and phase, appropriate spatial correlation functions
anticipate the transverse spatial pattern that appears above threshold. In particular, the angular dependence of the far field
spatial correlation function is able to reveal the travelling-wave nature of the phase pattern above threshold typical of
nondegenerate OPOs. Cross-correlation functions between signal and idler intensities show clear evidence of the non-classical
nature of the output light.
Received 8 October 1999 相似文献
6.
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
7.
Consecutive nonlinear optical interactions consisting of two coupled parametric processes, namely, the nondegenerate spontaneous parametric down-conversion and up-conversion, are analyzed. The vacuum state of the input light is considered to be an unstable state decaying into a reservoir of down-converted modes, with one of the modes generated being continuously measured using the up-conversion process. Mean photon numbers at interacting frequencies are studied. Special attention is paid to the case where the nonlinear coupling coefficient for the up-conversion process is much larger than that for the nondegenerate spontaneous parametric down-conversion. It is shown that in this case the result of such consecutive interactions can be interpreted from the viewpoint of the quantum Zeno effect. 相似文献
8.
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
9.
G. Brida M. Genovese C. Novero 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(2):273-275
We report the measurement of the photons flux produced in parametric down-conversion, performed in photon counting regime
with actively quenched silicon avalanche photodiodes as single photon detectors. Measurements are done with the detector in
a well defined geometrical and spectral situation. By comparison of the experimental data with the theory, a value for the
second order susceptibilities of the non linear crystal can be inferred.
Received 2 July 1999 and Received in final form 2 August 1999 相似文献
10.
E. Lantz F. Devaux 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,17(1):93-98
We study the properties of the spatial fluctuations in the far-field parametric fluorescence output of a type 1 degenerate
traveling-wave parametric amplifier. Results of a semi-classical simulation are compared with experiments in a LBO crystal.
This simulation is then used to predict amplified images of a continuous background, in a phase-sensitive as well as in a
phase-insensitive configuration.
Received 12 March 2001 相似文献
11.
Ken-Ichiro Imura 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):155-160
Effects of backward scattering between fractional quantum Hall (FQH) edge modes are studied. Based on the edge-state picture
for hierarchical FQH liquids, we discuss the possibility of the transitions between different plateaux of the tunneling conductance
G. We find a selection rule for the sequence which begins with a conductance (m: integer, p: even integer) in units of e
2/h. The shot-noise spectrum as well as the scaling behavior of the tunneling current is calculated explicitly.
Received 5 October 1999 and Received in final form 19 November 1999 相似文献
12.
W.M. Steffens S. Heisig U.D. Keil E. Oesterschulze 《Applied physics. B, Lasers and optics》1999,69(5-6):455-458
We report on the fabrication process of a scanning force microscopy (SFM) cantilever probe suitable for the investigation
of ultrafast transient signals in microwave integrated circuits. High temporal resolution is achieved by integrating a laser-gated
photoconductive switch within a coplanar waveguide structure onto a low-temperature GaAs cantilever. This is demonstrated
by temporal and spatio-temporal measurements performed on a coplanar strip line.
Received: 17 February 1999 / Revised version: 22 April 1999 / Published online: 29 July 1999 相似文献
13.
F. Grassia J. -M. Courty S. Reynaud P. Touboul 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(1):101-110
We present a quantum network approach to real high sensitivity measurements. Thermal and quantum fluctuations due to active
as well as passive elements are taken into account. The method is applied to the analysis of the capacitive accelerometer
using the cold damping technique, developed for fundamental physics in space by ONERA and the ultimate limits of this instrument
are discussed. It is confirmed in this quantum analysis that the cold damping technique allows one to control efficiently
the test mass motion without degrading the noise level.
Received 20 April 1999 and Received in final form 2 July 1999 相似文献
14.
K.Ø. Rasmussen S. Aubry A.R. Bishop G.P. Tsironis 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(1):169-175
We study the dynamics of the discrete nonlinear Schr?dinger lattice initialized such that a very long transitory period of
time in which standard Boltzmann statistics is insufficient is reached. Our study of the nonlinear system locked in this non-Gibbsian state focuses on the dynamics of discrete breathers (also called intrinsic localized modes). It is found that part of the
energy spontaneously condenses into several discrete breathers. Although these discrete breathers are extremely long lived,
their total number is found to decrease as the evolution progresses. Even though the total number of discrete breathers decreases
we report the surprising observation that the energy content in the discrete breather population increases. We interpret these
observations in the perspective of discrete breather creation and annihilation and find that the death of a discrete breather
cause effective energy transfer to a spatially nearby discrete breather. It is found that the concepts of a multi-frequency
discrete breather and of internal modes is crucial for this process. Finally, we find that the existence of a discrete breather
tends to soften the lattice in its immediate neighborhood, resulting in high amplitude thermal fluctuation close to an existing
discrete breather. This in turn nucleates discrete breather creation close to a already existing discrete breather.
Received 21 January 1999 and Received in final form 20 September 1999 相似文献
15.
The Thomas-Fermi equation, in conjunction with the Poisson equation is solved exactly for the problem of the two-dimensional
circular parabolic quantum dot in the presence of a weak magnetic field, in the framework of the local spin-density approximation.
The total energy, chemical potential, differential capacitance, degree of polarization, and diamagnetic susceptibility were
calculated. Asymptotic solutions were obtained for the limits of strong and weak confinement.
Received 19 February 1999 and Received in final form 26 July 1999 相似文献
16.
M. Sassetti F. Napoli B. Kramer 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(4):643-654
Using the bosonization technique, a theory for the collective excitations of the interacting electrons in quantum wires with
two subbands occupied is developed. The dispersion relations for the inter-subband charge and spin density excitations are
determined. The results are used to interpret the features observed in recent measurements of the Raman spectra of AlGaAs/GaAs
quantum wires, particularly for photon energies near band gap resonance. It is shown that peaks previously identified as “single
particle excitations” are signatures of higher order collective spin density excitations. Predictions about the observability
of the interband modes are made.
Received 8 February 1999 相似文献
17.
A. Goharzadeh I. Mutabazi 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(1):157-162
We investigate experimentally the properties of spatio-temporal intermittency states (turbulent bursts and spiral turbulence)
in the counter-rotating Couette-Taylor system. The mean turbulent fraction increases continuously from turbulent bursts to
spiral turbulence and depends on the angular velocity of both cylinders. The axial velocity of turbulent spirals, which depends
only on the outer cylinder, is smaller than the azimuthal component.
Received 15 December 1999 and Received in final form 19 October 2000 相似文献
18.
A. Sinatra Y. Castin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,8(3):319-332
We investigate the relative phase coherence properties and the occurrence of demixing instabilities for two mutually interacting
and time evolving Bose-Einstein condensates in traps. Our treatment naturally includes the additional decoherence effect due
to fluctuations in the total number of particles. Analytical results are presented for the breathe-together solution, an extension
of previously known scaling solution to the case of a binary mixture of condensates. When the three coupling constants describing
the elastic interactions among the atoms in the two states are close to each other, a dramatic increase of the phase coherence
time is predicted. Numerical results are presented for the parameters of the recent JILA experiments.
Received 23 April 1999 and Received in final form 21 September 1999 相似文献
19.
T. Golubeva Yu. Golubev C. Fabre N. Treps 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):179-193
In this paper, we investigate several properties of the
full signal-idler-pump mode quantum state generated by a triply
resonant non-degenerate Optical Parametric Oscillator operating
above threshold, with an injected wave on the signal and idler
modes in order to lock the phase diffusion process. We determine
and discuss the spectral purity of this state, which turns out not
to be always equal to 1 even though the three interacting modes
have been taken into account at the quantum level. We have seen
that the purity is essentially dependent on the weak
intensity of the injected light and on an asymmetry of the
synchronization. We then derive the expression of its total
three-mode Glauber P-function, and calculate the joint
signal-idler photon number probability distribution and
investigate their dependence on the injection. 相似文献