Photonic Hook Initiated Using an Air–Liquid Interface

In this paper, we demonstrate a novel photonic hook being initiated using an air–liquid interface (ALI). This bent light focus is produced by immersing a dielectric micro-cylinder partially at the edge of a thin liquid film whose thickness is smaller than the diameter of the micro-cylinder. Unlike the well-known properties of normal near-field focuses, this photonic hook propagates horizontally in the liquid along the ALI at specific depths and does not require the material processing of microscopic particles or the modulation of light irradiation for initiation. A morphological analysis indicates that the contrast in the refractive indexes of the ALI causes this phenomenon at the shadow end of the micro-cylinder with a transverse dimension smaller than the diffraction limit. Compared to previously discovered photonic hooks, the unique setup of this photonic hook can generate a force field that enables optical trapping in the region slightly beneath the ALI, and the related optical pressures have been simulated.