This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by optimising the chirping parameters. The time-frequency characteristics of high-order harmonics with different chirping parameters are analysed by means of wavelet transform of the dipole acceleration. It also gives out the classical three-step model pictures of electron. By superposing a properly selected range of the harmonic spectrum, it obtains an isolated 65as pulse.
We have studied the dynamics of Bose-Einstein condensate by solving numerically the Gross-Pitaevskii (GP) equation.We examined the periodic behaviour of the condensate in a shifted harmonic potential,and further demonstrated the tunneling effect of a condensate through a Gaussian energy barrier,which is inserted after the condensate has been excited by shifting the harmonic trapping potential to a side.Moreover,it is shown that the initial condensate evolves dynamically into two separate moving condensates after the tunneling time under certain conditions.
The tunneling effect of Bose-Einstein condensate (BEC) in a harmonic trap with a Gaussian energy barrier is studied in this paper. The initial condensate evolves into two separate moving condensates after the tunneling time under certain conditions. The interference pattern between the two moving condensates is given as a comparison and as a further demonstration of the existence of the global phase.
