Optimization of crystal high-order harmonic generation by tailoring the nonuniform irradiations

High-order harmonic generation (HHG) is expected to produce high-quality coherent ultrashort light sources. We propose a scheme similar to laser mode locking to selectively enhance and compress HHG in crystals through nonuniform illuminations and phase matching. The selective enhancement of harmonics reflects attosecond-resolved electron dynamics. And these harmonic characteristics originate from the interference of harmonics from different lattices. It paves the way for the practical application of solid HHG with high conversion efficiencies and the detection of electron-hole dynamics with ultrahigh spatial-temporal resolution.