Abstract

In this work, we theoretically study the transduction of orbital angular momentum (OAM) $l$ for infrared pump lasers into the THz domain. In the case of optical rectification, the transduction of OAM occurs only through a spin–orbit interaction, with the selection rule on the OAM $l = 0$ valid for any kind of polarization of the pump, which means that there is no transfer of OAM along the propagation axis. In difference frequency generation, the selection rule for the difference $\Delta l$ between the OAM of the pump fields with linear or circular polarization is $l = \Delta l$, whereas $l$ ranges from $\Delta l - 2$ to $\Delta l + 2$ in cases of both radial and azimuthal polarization. Moreover, for THz generation in the latter case, the high diffraction obtained with tightly focused pumps yields $l$ tending to $\Delta l \pm 2$, while $l$ tends to zero in the opposite case of large pump beams.

© 2021 Optical Society of America