Collective dynamics in a laser-pumped mixture of two atomic ensembles

We investigate the quantum dynamics of an atomic mixture composed of two multi-atom ensembles. Each ensemble is driven separately by a coherent laser field, respectively, and dampens via the interactions with the environmental vacuum electromagnetic field reservoir. We find that, due to the photon exchange among the two components, long-time excitation oscillations appear, which may be significantly longer than the inverse lifetime of a single emitter. Furthermore, few-atom "jumps" to the excited state occur as a function of the parameter characterizing the inter-component interactions around a certain working point.Comment: 6 pages, 5 figure

Phase control of spatial interference from two duplicated two-level atoms

We report the phase control of spatial interference of resonance fluorescence from two duplicated two-level atoms, driving by two orthogonally polarized fields. In this closed-loop system, the relative phase is of crucial importance to the recovery of the interference patten in the fluorescence light even with strong driving.In order to improve the experimental realizability, we propose a scheme to recover the visibility with fixed relative phase by adjusting the relative intensities between the two driving fields or alternatively by using a standing-wave field.Comment: 5 pages, 3 figure

Photon scattering from strongly driven atomic ensembles

The second order correlation function for light emitted from a strongly and near-resonantly driven dilute cloud of atoms is discussed. Because of the strong driving, the fluorescence spectrum separates into distinct peaks, for which the spectral properties can be defined individually. It is shown that the second-order correlations for various combinations of photons from different spectral lines exhibit bunching together with super- or sub-Poissonian photon statistics, tunable by the choice of the detector positions. Additionally, a Cauchy-Schwarz inequality is violated for photons emitted from particular spectral bands. The emitted light intensity is proportional to the square of the number of particles, and thus can potentially be intense. Three different averaging procedures to model ensemble disorder are compared.Comment: 7 pages, 4 figure

Tunable ultranarrow linewidth of cavity induced by interacting dark resonances

A scheme for getting a tunable ultranarrow linewidth of a cavity due to an embedded four-level atomic medium with double-dark resonances is proposed. It is shown that the steep dispersion induced by double-dark resonances in the transparency window leads to the ultranarrow transmission peak. Compared with the case of a single-dark-resonance system, the linewidth can be narrowed even by one order under proper conditions. Furthermore, the position of the ultranarrow peak can be engineered by varying the intensity and detuning of the control field.Comment: 4 pages, 5 figure

Spin polarized proton beam generation from gas-jet targets by intense laser pulses

A method of generating spin polarized proton beams from a gas jet by using a multi-petawatt laser is put forward. With currently available techniques of producing pre-polarized monatomic gases from photodissociated hydrogen halide molecules and petawatt lasers, proton beams with energy ~ 50 MeV and ~ 80 % polarization are proved to be obtained. Two-stage acceleration and spin dynamics of protons are investigated theoretically and by means of fully self-consistent three dimensional particle-in-cell simulations. Our results predict the dependence of the beam polarization on the intensity of the driving laser pulse. Generation of bright energetic polarized proton beams would open a domain of polarization studies with laser driven accelerators, and have potential application to enable effective detection in explorations of quantum chromodynamics

Infrared and Visible Image Fusion Based on Spatial Convolution Sparse representation

Abstract In the traditional sparse representation based infrared and visible image fusion method, the detail information is not able to be effectively extracted, resulting in the decrease of infrared target intensity and the blurry of visible background information. In order to solve the above issue, a new image fusion method based on spatial convolution sparse representation is proposed. Firstly, a spatial convolution sparse representation is used to perform two-scale decomposition of infrared and visible images by introducing a gradient regularization, and the detail and intensity information are extracted effectively from the source images. Then, the weighted average rule and the maximum selection rule are used to fuse the base layer and detail layer images, respectively. Finally, the fusion image is constructed. Experimental results illustrate that the proposed method is superior to the traditional fusion method based on sparse representation.</jats:p

Nanocontrol of single dense energetic electron sheet in a chirped pulse with critical relativistic intensity

We investigate the effect of laser frequency chirp on the generation of a dense energetic electron sheet. The direct acceleration regime of laser driven dense electron sheet requires high laser intensity to function efficiently. We demonstrate this requirement can be relaxed by applying chirped lasers. The acceleration becomes more efficient while driven by a pulse with a proper linear chirp, leading to a dense energetic electron sheet in nanoscale, and therefore requires lower laser intensity

Nanocontrol of single dense energetic electron sheet in a chirped pulse with critical relativistic intensity

We investigate the effect of laser frequency chirp on the generation of a dense energetic electron sheet. The direct acceleration regime of laser driven dense electron sheet requires high laser intensity to function efficiently. We demonstrate this requirement can be relaxed by applying chirped lasers. The acceleration becomes more efficient while driven by a pulse with a proper linear chirp, leading to a dense energetic electron sheet in nanoscale, and therefore requires lower laser intensity