Probing the spectral and temporal structures of high-order harmonic generation in intense laser pulses

We present an ab initio three-dimensional quantum study of high-order harmonic generation (HHG) of atomic H in intense pulsed laser fields. Accurate time-dependent wave functions are obtained by means of the time-dependent generalized pseudospectral method recently developed and wavelet transform is used to perform time-frequency analysis of the resulting HHG power spectra. The results reveal striking details of the spectral and temporal fine structures of HHG, providing insights regarding HHG mechanisms in different energy regimes and benchmark data for testing the validity of existing HHG models.