ABSTRACT Recent advancements in ferroelectric domain engineering have provided a promising avenue for nonlinear beam shaping. However, a device enabling continuous manipulation of spatial modes in a parametric way, akin to waveplates used for polarization control, remains absent. In this work, we introduce and demonstrate a novel nonlinear photonic crystal (NPC) capable of simultaneously converting the frequency and orbital angular momentum (OAM) states of structured light. Instead of constructing a nonlinear spiral phase plate, the NPC was designed to perform a nonlinear unitary transformation on the OAM state of the parametric generation, with the resultant state being contingent upon the relative angle between the input state and the crystal. The NPC facilitates a parametric modal interface that enables access to all possible states on the same modal sphere of the input beam. This nonlinear toolkit shows great potential in diverse applications with structured light.
Zhang et al. (Sat,) studied this question.
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