Abstract
Cusp beams are one type of complex structured beams with unique multiple self-accelerating channels and needle-like field structures owning great potentials to advance applications such as particle micromanipulation and super-resolution imaging. The traditional method to generate optical catastrophe is based on cumbrous reflective diffraction optical elements, which makes optical system complicated and hinders the nanophotonics integration. Here we design geometric phase based ultrathin plasmonic metasurfaces made of nanoslit antennas to produce three-dimensional (3D) optical cusp beams with variable numbers of self-accelerating channels in a broadband wavelength range. The entire beam propagation profiles of the cusp beams generated from the metasurfaces are mapped theoretically and experimentally. The special self-accelerating behavior and caustics concentration property of the cups beams are also demonstrated. Our results provide great potentials for promoting metasurface-enabled compact photonic devices used in wide applications of light-matter interactions.
Highlights
Catastrophe theory mathematically describes the formation and dramatic change of bifurcations as geometrically stable structures in nonlinear potential functions under the perturbations of external control parameters[1,2]
Different from bulky optical components with the phase shift depending on the optical path, metasurfaces can introduce the Pancharatnam-Berry geometric phase accompanied with polarization conversion, which can overcome narrow bandwidth limitation and make the optical device compact[22,23,24,25,26,27]
We investigate and analyze the generated 3D cusp beams with geometric phase based ultrathin plasmonic metasurfaces constructed from nanoslit antennas
Summary
Catastrophe theory mathematically describes the formation and dramatic change of bifurcations as geometrically stable structures in nonlinear potential functions under the perturbations of external control parameters[1,2]. In contrast to the fold caustics, this kind of cusp caustics owns the simultaneous self-healing and self-bending propagation properties and has the remarkable caustics concentration property which leads to the generation of needle-like field structure[8,12,13,14]. Such novel beam properties of cusp beams will enable many spectacular applications such as optical particle micromanipulation and transportation[15,16], super-resolution imaging[17,18] and curved plasma channels[19]. Our demonstrated results will provide promising possibilities for building metasurface-enabled ultrathin photonic devices used in many applications of light-matter interactions such as complex light field conversion, optical particle manipulation, and super-resolution imaging
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