Control the orbital angular momentum in third-harmonic generation using quasi-phase-matching

Manipulating photon’s orbital angular momentum (OAM) through nonlinear interactions has drawn increasing research interests in recent years. In this work, we propose a scheme to control the OAM of the third harmonic wave through two cascaded second-order nonlinear processes. A Gaussian beam was frequency doubled at the first stage. Subsequent sum frequency mixing of the Gaussian second harmonic wave and an orthogonal-polarized Laguerre-Gaussian-like fundamental wave generate the third harmonic wave, which carries the same OAM as that of the Laguerre-Gaussian-like fundamental wave. In this experiment, we demonstrated controlling the OAM of the third harmonic wave in a tandem periodically-poled LiTaO3 optical superlattice, and the results are in accordance with theoretical predictions.