Using dynamical Hartree-Fock mean-field theory, we study the high harmonic generation (HHG) in fullerene molecules ${\mathrm{C}}_{60}$ and ${\mathrm{C}}_{70}$ under strong pump wave driving. We consider a strong-field regime show that output radiation exhibits multiple plateaus, whose borders are defined by molecular excitonic lines cutoff energies within each plateau scale linearly with field ...

We study third-harmonic generation (THG) in an excitonic insulator (EI) described a two-band correlated electron model. Employing the perturbative expansion with respect to external electric field, we derive THG susceptibility taking into account collective dynamics of order parameter. In inversion-symmetric EI, parameter motion is activated at second field and its effects arise THG. find three...

We present a theoretical study of second-harmonic generation from singular metasurface. The metasurfaces strongly interact with the incident light, where large field enhancement forms an intense surface polarization that generates field. By using transformation optics, calculation nonlinear optical response is converted metasurface frame to simple slab geometry, largely reducing complexity prob...