Probing spectral and temporal fine structures of high-order harmonic generation in laser-driven electron-rescattering

We present an ab initio precision investigation of the subtle details of the spectral and temporal fine structures of high-order harmonic generation (HHG) in laser-driven electron-rescattering by using a new synchrosqueezing transform method (SST). The SST time-frequency analysis allows us to explore the in depth dynamics and contributions of the quantum trajectories in HHG associated with the electron-rescattering. Particularly it uncovers the subtle details of the spectral and temporal fine structures of the HHG and provides novel insights regarding the dynamical origin of the HHG in below-threshold harmonic regimes.