High-order harmonic generation from hybrid lead halide perovskites*

Nonlinear optical current induced by strong laser fields produces coherent radiation in spectral ranges inaccessible by lasers. Such high-harmonic generation (HHG) in solids is different from that in atomic gases; it has been shown that the intraband current caused by ultrafast acceleration of electron wave packets constitutes the nonlinear current [1,2]. However, how the concurrent field-driven population change in valence band contributes the nonlinear current remains unclear. Here, we studied the crystal orientation dependence of HHG intensity for hybrid organic–inorganic halide perovskites, which is well reproduced by the calculations based on an ab-initio approach. Our picture indicates that the virtual population change in the valence band is responsible for the HHG, which is of vital importance for achieving high generation efficiency and taking a full of information on bandstructure.
[1] S. Ghimire et al., Nat. Phys. 7, 138–141 (2011).
[2] O. Schubert et al., Nat. Photonics 8, 119–123 (2014).