Comparison of high harmonic generation and attosecond pulse from 3D hydrogen atom in three kinds of inhomogeneous fields

The high harmonic generation (HHG) from 3D hydrogen (H) atom in three kinds of inhomogeneous fields are investigated by solving the time-dependent Schrodinger equation (TDSE) accurately with time-dependent generalized pseudospectral method (TDGPS), and compared together. The corresponding time frequency and three-step model is also presented to explain the differences between three cases. We will also calculate the ionization probability and electron wavepacket as functions of time to further illustrate this phenomenon. By superposing a series of properly selected harmonics, the isolated attosecond pulses can be obtained straightforwards the shortest of which is 64 as. (C) 2015 Elsevier B.V. All rights reserved.