Abstract

High-order harmonic generation (HHG) induced by intense ultrashort pulsed laser has been studied in gaseous media for decades. In the various studies on HHG, the orbital angular momentum (OAM) of light has been attracting much attention from the perspective of controlling the spatio-temporal structure of harmonics [1]. In parallel, research on HHG has been extended to solids, and rich physical phenomena exhibited by their material properties have been intensively studied [2]. However, it is still unclear how the properties of solids, such as crystal symmetry, appear in the macroscopic optical response associated with the OAM. Interestingly, birefringence in anisotropic crystals can allow the spin angular momentum (corresponds to circular polarization) and OAM of light to couple during light propagation, which is called the spin-orbit interaction (SOI) of light [3]. This coupling brings intriguing phenomena in HHG beyond the conventional framework of spin and orbital angular momentum conservation rules [1,4].

© 2023 IEEE