Fig. 1. High-order harmonic radiation numerically solved from time-dependent Schr?dinger equation. (a) High-order harmonic radiations at different laser intensities; (b) high-order harmonic radiations near photo energy of 16 eV; (c) strength of resonance-enhanced high-order harmonic radiation as a function of laser intensity

Fig. 2. Time-frequency analysis. (a) Time-frequency signal spectrum obtained by wavelet transform of signals in Fig.1 (b); (b) partial amplification at low photon energies range of Fig. 2(a); (c) signal spectrum obtained by short-time Fourier transform of time-dependent dipole moments, which are generated by weak laser intensity in Fig. 1(b)