Effect of pulse duration on generation of attosecond pulse with coherent wake emission

High-order harmonics and attosecond pulse generation with coherent wake emission are theoretically investigated for the effect of pulse duration and carrier envelope phase(CEP)of few-cycle laser pulse.We find that short pulse duration will cause the negative chirp for the high harmonics.When the laser pulse is shortened to a few cycles,the influence of the laser CEP on the chirp of the harmonics will also become more prominent.

Analyses of multi-pion Bose-Einstein correlations for granular sources with coherent pion-emission droplets

The ALICE Collaboration measured three-and four-pion Bose-Einstein correlations(BECs)for Pb-Pb collisions at the Large Hadron Collider(LHC).It is speculated that the observed significant suppression of multi-pion BECs is owing to a considerable degree of coherent pion emission in these collisions.Here,we study multi-pion BEC functions for granular sources with coherent pion-emission droplets.We find that the intercepts of the multi-pion correlation functions at the relative momenta near zero are sensitive to the number of droplets in the granular source.They decrease with the droplet number.The three-pion correlation functions for evolving granular sources with momentum-dependent partially coherent pion-emission droplets basically agree with the experimental data for Pb-Pb collisions at √SNN=2.76 TeV at the LHC.However,the model results for the four-pion correlation function are inconsistent with the experimental data.Investigations into normalized multi-pion correlation functions of granular sources suggest an interesting enhancement of the normalized four-pion correlation function in the moderate relative-momentum region.

Directional coherent light via intensity-induced sideband emission

We introduce a unique technique for generating directional coherent emissions that could be utilized to create coherent sources in a wide range of frequencies from the extreme ultraviolet(XUV)to the deep infrared.This is accomplished without population inversion by pumping a two-level system with a far-detuned strong optical field that induces the splitting of the two-level system.A nonlinear process of four-wave mixing then occurs across the split system,driving coherent emission at sidebands both redand blue-detuned from the pump frequency,and propagates both forward and backward along the pump beam path.We observed this phenomenon in dense rubidium vapor along both the D_(1) and D_(2) transitions.The sideband emission exhibits a short pulse duration(o1 ns)with threshold-like behavior dependent on both the pump intensity and Rb vapor density.This technique offers a new capability for manipulating the emission frequency simply through intensity-induced atomic modulation that can be scaled to most frequency regimes using various atomic/molecular ensembles and pump energies.