Analysis of spatially resolved solid-state high-harmonic generation using two-color noncollinear laser beams

We theoretically investigate spatially resolved high-harmonic generation (HHG) from a single layer of wurtzite ZnO driven by two-color noncollinear laser fields. This is done by solving two-band semiconductor Bloch equations (SBEs) on the microscopic level and using the Fraunhofer diffraction integral for calculating the macroscopic angle-resolved HHG spectra, from which wave-mixing channels are identified and resolved. In the two-color noncollinear scheme, we treat the two laser fields as the generation and control fields for the HHG, and systematically analyze how the high-harmonic yield in different wave-mixing channels varies with the control-field amplitude. We find that the control-field amplitude can cause monotonic and non-monotonic changes of the yield in different channels,depending on the net number of photons exchanged with the control field,which can be interpreted with a photon-pathway model. Furthermore,when adopting a longer dephasing time in the SBEs, the contributions from electron–hole trajectories with longer excursion times are progressively retained, leading to stronger trajectory interference and broader far-field spatial distributions. The harmonic yield ratio between difference-frequency and sum-frequency channels exhibits a pronounced channel-dependent sensitivity to the dephasing time,particularly for large-divergence channels, indicating that the spatially resolved wave-mixing HHG spectra contain some information of the interband coherence dynamics .