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When a bulk solid is irradiated by an intense laser pulse, transition dipole moments (TDMs) between different energy bands have an important influence on the ultra-fast dynamic process. In this paper, we propose a new all-optical method to reconstruct the k-dependent TDMs between multi-bands using a crystal high-order harmonic generation (HHG). Taking advantage of an obvious separation of bandgaps between three energy bands of an MgO crystal along the <001 > direction, a continuous harmonic spectrum with two plateaus can be generated by a two-color laser pulse. Furthermore, the first harmonic platform is mainly dominated by the polarization between the first conduction band and the valence band, and the second one is largely attributed to the interband HHG from the second conduction band and the valence band. Therefore, the harmonic spectrum from a single quantum trajectory can be adopted to map TDMs between the first, second conduction bands, and the valence one. Our work is of great significance for understanding the instantaneous properties of solid materials in the strong laser field, and will strongly promote the development of the HHG detection technology.

ZrC and ZrB 2 were prepared by self-propagating high-temperature synthesis in a Cu-Zr-B 4 C system. We explored the influence of B 4 C particle size on the reaction process, phase composition and microstructure of the products. The results show that the production of ZrC and ZrB 2 is mainly controlled by the dissolution of B 4 C in Cu-Zr liquid. Increasing the size of B 4 C will not affect the reaction path, but will retard the formation of the Cu-Zr-B-C liquid. This leads to the incomplete conversion of ZrC and ZrB 2 once the B 4 C exceeds 28 m. In addition, ZrC and ZrB 2 particle sizes greatly decrease from the micrometer dimension with a polyhedral morphology to the nanometer scale with a nearly spherical shape.