Influence of fluctuations of a laser pump on the intensity correlation of resonance fluorescence radiation

The influence of fluctuations of a relatively weak laser pump on the intensity correlation of resonance fluorescence radiation is studied for a laser acting both below and above the threshold. Below the threshold the radiation of the laser is characterized by Gaussian properties causing non-factorization of the intensity correlation function. Above the threshold the laser shows non-linear filter properties and, therefore, the deviation of the exact intensity correlation function from its factorized value is small.     

Intensity correlation of the resonance fluorescence radiation from an atom driven by a laser pump with amplitude and phase fluctuations

The influence of the phase and amplitude fluctuations of a relatively weak laser pump on the intensity correlations of the resonance fluorescence light from a single atom is studied. It is found that the contributions due to a non-Markovian dephasing of the laser light can be neglected in many cases. The amplitude fluctuations and the attendant non-factorizability of the intensity correlation function are shown to lead to a stronger correlation of the intensities of the resonance fluorescence light considered.     

Antibunching,sub-poissonian photon statistics and finite bandwidth effects in resonance fluorescence

It is demonstrated that, although the fluorescent photons from a driven two-level atom always exhibit antibunching, they need not obey sub-poissonian statistics. The maximum sub-poissonian excursion of the normalized second factorial moment (〈(Δn)²〉 ? 〈n〉)/〈n〉 occurs in the transient regime where it can approach the value -1. Effect s of finite bandwidth of excitation on photon statistics are also investigated and it is shown that the photon number distribution may be narrower with finite bandwidth excitation than with coherent excitation.     

The effects of intensity in resonance fluorescence

The probability of resonance fluorescence with account of intensity influence is calculated on the basis of the semiclassical radiation theory. In the case of a monochromatic external field the results confirm those of Mollow. Scattering probabilities in the case of a bichromatic external field are also obtained.     

Time development of the light intensity in resonance fluorescence

The time evolution of the fluorescent light emitted by a two-level atom that is driven by an external quantum field close to resonance, has been calculated. Although the treatment lies within the framework of QED, it is found that the answer in no way depends on any quantum properties of the field.     

Influence of low intensity noise on assemblies of diffusively coupled chaotic cells

The effect of time-correlated and white Gaussian noises of low intensity on one-dimensional arrays consisting of diffusively coupled chaotic cells is analyzed. An improvement or worsening of the synchronization between cells of the array driven by low-intensity colored noise is observed for a resonant interval of time correlation values. A comparison between colored and white noise and additive and multiplicative contribution has been carried out investigating the nonlinear cooperative effects of noise strength, correlation time, and coupling strength to control spatiotemporal chaos in coupled arrays of chaotic cells. The possibility to distinguish highly correlated areas of a diffusively coupled network of cells by using low-intensity time correlated noise is discussed. (c) 2001 American Institute of Physics.     

Intensity correlation spectroscopy of the resonance fluorescence light of two-atomic molecules

The spectroscopic application of intensity correlation measurements of the resonance fluorescence light from two-atomic molecules is proposed. It is shown that from the intensity correlation function not only the natural line width of the electronic transition and the electron-vibration coupling strength but also very narrow homogeneous vibrational line widths can be determined without any use of a spectral apparatus.     

Narrow resonances with excitation of finite bandwidth field

The effect of the laser linewidth on the resonance fluorescence spectrum of a two-level atom is revisited. The novel spectral features, such as hole-burning and dispersive profiles at line centre of the fluorescence spectrum are predicted when the laser linewidth is much greater than its intensity. The unique features result from quantum interference between different dressed-state transition channels.     

Conductance of inhomogeneous Luttinger liquids with a finite bandwidth

The finite-bandwidth conductance of a Luttinger liquid (LL) with a cluster of impurities is studied and its variation with respect to temperature is shown. The calculations are done using the correlation functions obtained using the powerful non-chiral bosonization technique (NCBT). The results are compared with those obtained by Matveev, Yue and Glazman [K. Matveev et al., Phys. Rev. Lett. 71, 3351 (1993)] who deal with a weakly interacting LL. By contrast, NCBT correctly provides the conductance for all values of the interaction strength (as well as the sign). In addition to finding perfect agreement with the results of Matveev et al. for both weakly repulsive and weakly attractive mutual interactions, we are also able to probe novel physics seen when the repulsion is strong - in the form of a weakly temperature dependent conductance when there is a definite relationship between the transmission amplitude of the non-interacting system and the holon velocity. Secondly, an unusual high conductance for strongly repulsive mutual interactions is observed for a weak barrier at low temperatures. Lastly, inclusion of backward scattering leads to the non-monotonic temperature dependence of conductance when dealing with fermions with spin. This work is also important as a validation of the NCBT itself.     

Ablation effects on weakly nonlinear Rayleigh-Taylor instability with a finite bandwidth

A weakly nonlinear but numerically tractable model (to third order in amplitude and including bandwidth effects) has been developed for the ablative Rayleigh-Taylor (RT) instability. Model results clearly show growth reduction from linear ablative RT values and even amplitude saturation in some realistic cases. For excitation of a band of wave numbers near the cutoff for growth, the behavior is dominated by the mode with the largest linear growth rate, and not by the mode with the largest initial amplitude. This type of model is likely to be important for the future assessment of the RT effects on specific target designs of the inertial confinement fusion.     

Influence of the degree if dispersion of uranine in solutions on the fluorescence light intensity

From scattering measurements of light which does not excite fluorescence, it is found that acetone, dioxan or ethanol in low concentrations reduce the aggregates in an aqueous solution of uranine. In contrast, concentrated solutions of acetone, dioxan and ethanol enhance these aggregates. A correlation is found between the intensity of the light scattered by the aggregates and the fluorescence light intensity.     

噪声间关联程度的时间周期调制对单模激光随机共振的影响

用线性化近似的方法研究了噪声间关联程度λ受时间周期性调制的单模激光增益模型的光强功率谱及信噪比.具体讨论信噪比R受加法噪声强度D,乘法噪声强度Q及噪声间关联程度λ的影响,以及受周期调制频率Ω_λ,输入信号频率Ω的影响.发现了一些新颖的现象. 关键词： 时间周期调制频率 噪声间关联程度 随机共振 信噪比     

Simulation study of the two-time intensity correlation function of a two-mode laser system with both pump and quantum noises

This paper investigates the two-time intensity correlation function of a two-mode ring laser system subjected to both pump and quantum noises by stochastic simulation. It finds that the decay rate of the intensity correlation function of one mode gets faster with decreasing values of relevant parameters, i.e., the coupling constant ξ, the cross-correlation coefficient λ , the difference of the pump parameters Δa and the pump parameter a₁; however, its variations get complex in the other mode when relevant parameters are changed. The investigating results also show that the effects of the mode competition on intensity correlation function are obvious.     

Sensitive measurement of radiation trapping in cold-atom clouds by intensity correlation detection

We present experimental evidence that the intensity correlations of light scattered from a cold-atom cloud are sensitive to the presence of small amounts of radiation trapping in an atomic sample of density 6 x 10(8)/cm3, with an optical depth (for a resonant light beam) of 0.4. This density and optical depth are approximately an order of magnitude less than the density and on-resonance optical depth at which effects of multiple scattering in cold-atom clouds have been previously observed [Phys. Rev. Lett. 64, 408 (1990)].     

Influence of speech stimuli intensity on the activation of auditory cortex investigated with functional magnetic resonance imaging.

Understanding the impact of variations in the acoustic signal is critical for the development of auditory and language fMRI as an experimental tool. We describe the dependence of the BOLD signal and speech intelligibility on the intensity of auditory stimuli. Eighteen subjects were imaged on a 1.5-T MRI scanner. Speech stimuli were English monosyllabic words played at five intensity levels. Intrasubject reproducibility was measured on one subject by presenting the stimulus five times at the same intensity level. Intelligibility was measured during data acquisition as subjects signaled when hearing two targets. Each functional trial consisted of four cycles (30 s off-30 s on). Five oblique slices covering primary and association auditory areas were imaged. Activated voxels were identified by cross-correlation analysis and their percent signal change (delta S) was measured. Intersubject differences in activation extent, asymmetry, and dependence on intensity were striking. Volume of activation was significantly greater in the left than in the right hemisphere. Intrasubject reproducibility for delta S was higher than for volume of activation. delta S and intelligibility showed a similar dependence on intensity suggesting that not only intensity but also intelligibility affect the fMRI signal.