Pendulum-type light beams

Abstract

Nondiffracting and shape-preserving light beams have been extensively studied and were shown to exhibit intriguing wave phenomena, which led to applications including particle manipulation, curved plasma channel generation, and optical superresolution. However, these beams are generated by caustics, i.e., conical superposition of waves. As a result, they tend to propagate along a straight line or accelerate in a plane [(1 + 1)D], and tailoring their propagation trajectories in a higher dimension [(2 + 1]D] is challenging. Here we report both theoretically and experimentally a class of nondiffracting solutions to the paraxial wave equation perturbed by harmonic potential. We demonstrate that the initial wave packets of light can be engineered to accelerate along an arbitrary trajectory centered on an elliptic or a circular orbit in a (2 + 1)D configuration, while maintaining their phase and polarization structures during propagation. Such particle-like features manifested by orbital movements can be attributed to the centripetal force of the underlying potential. We name such oscillating wave packets as pendulum-type beams. We suggest the concept can be generalized to other waves such as quantum waves, matter waves, and acoustic waves, opening possibilities for the study and applications of the pendulum-type wave packet in a wide range, e.g., it may be utilized in the field of laser scanning technology.