Fig. 3: Overview of non-cascade high-harmonic random walks in α-quartz.
From: Non-cascade random walks in solid-state high harmonic generation
a Spatial and polarization profiles of the fundamental vector laser beam. The chirality of the elliptical (circular) polarization is colored with blue and purple. b Scheme of the interaction for HHG in three-fold rotational symmetric \(\alpha\)-quartz driven by a strong vector laser pulse. c–e Illustration of non-cascade random walks in the \(s\otimes \ell\) Hilbert space for the (c) fundamental wave, (d) second harmonic, and (e) third harmonic, respectively. Hollow circles illustrate the positions of the previous step, while solid circles illustrate the positions of the present step. Upper insets denote the SAM selection rule of the harmonic emission via diverse multiphoton absorption pathways. Left insets denote the OAM population of the harmonic emission.
