Tunable Optical Hooks in the Visible Band Based on Ultra-Thin Metalenses

Optical hook, a kind of curved high-intensity light beam, has aroused tremendous interests during the past several years, and its experimental observation has been reported in the terahertz band. The existing approaches to generate such beams depend on the effect of "curved photonic nanojet" stemming from transparent and symmetry breaking high-index dielectric slab, and thus are restricted by the limited material selection, large device footprint, and fixed trajectory. Herein, the generation of photonic hooks in the visible band based on ultra-thin metalenses is reported. The strategy can overcome the limitations mentioned above and the photonic hook can be easily tuned by changing the incidence angle or wavelength. Such flexibility is likely to widen the future applications of such unique beam in particle trapping, optical tweezers, and superresolution imaging.