Multiple copies of orbital angular momentum states through second-harmonic generation in a two-dimensional periodically poled LiTaO3 crystal

Abstract

We experimentally demonstrate multiple copies of optical orbital angular momentum (OAM) states through quasi-phase-matched (QPM) second-harmonic (SH) generation in a 2D periodically poled LiTaO3 (PPLT) crystal. Since the QPM condition is satisfied by involving different reciprocal vectors in the 2D PPLT crystal, collinear and noncollinear SH beams carrying OAMs of l2 are simultaneously generated by the input fundamental beam with an OAM of l1. The OAM conservation law (i.e., l2 = 2l1) holds well in the experiment, which can tolerate certain phase-mismatch between the interacting waves. Our results provide an efficient way to obtain multiple copies of the wavelength-converted OAM states, which can be used to enhance the capacity in optical communications.