Strain effects on high-order harmonic generation in solids

Laser-induced high harmonic generation (HHG) in solids strongly depends on the band structure of the target. In this work, we studied the band structure of bulk wurtzite ZnO under different strains. The changes of band structure induced by shear, uniaxial, biaxial, and isotropic strains are compared. It is found that the band gap can be narrowed or widen by modulating the external conditions, which offers an efficient way to engineer the wide-gap crystals to produce HHG. The strain effects on HHG are investigated by numerically solving the semiconductor Bloch equations. Our calculations show that the HHG yield depends sensitively on the change of band structure caused by stress- and temperature-induced strains. In addition, we found that the emission times of HHG and the ratio between inter and intraband contributions to the total solid HHG spectra can be controlled by the magnitude of strain imposed on the solid targets.