Abstract
Traditionally, optical vortices (OVs) were generated with diffractive optical elements (DOEs) such as spiral phase plate (SPP), fork grating, spatial light modulator (SLM), and liquid crystal display (LCD). Here, a method was proposed for generating OVs by employing all-dielectric polarization-insensitive metasurfaces with cylinder arrays, which have high transmission efficiency. The polarization insensitivity of the metasurfaces was illustrated with the incidence of two pairs of orthogonal polarization, both the phase and transmission efficiency were consistent for the cylinder unit cell, and similar OVs were generated with the cylinder array. The topological charges of the generated OVs can be adjusted through the design of the metasurfaces. OVs with additional characteristics as vector beams, focused beams and Bessel beams were further generated. This work has potential applications in beam shaping, optical tweezers, and optical communication.
Highlights
Optical vortex (OV) is a light field with a helical wavefront possessing orbital angular momentum (OAM) [1]
The polarization insensitivity of the metasurfaces was illustrated with the incidence of two pairs of orthogonal polarization, both the phase and transmission efficiency were consistent for the cylinder unit cell, and similar OVs were generated with the cylinder array
OAM is associated with the topological charge l, which has unlimited number of eigenmodes (1, 2, 3 ...), offers additional freedom besides wavelength, amplitude and polarization, provides much more information capacity, and finds optical communication applications in both classical and quantum optics [3], [4]
Summary
Optical vortex (OV) is a light field with a helical wavefront possessing orbital angular momentum (OAM) [1]. The helical phase distribution of OV is determined by its phase factor exp(ilθ ) [2], where l and θ are topological charge and azimuthal angle, respectively. The applications of OV mainly rely on two distinct characteristics, the OAM related the spiral phase and the central darkness. OAM is associated with the topological charge l, which has unlimited number of eigenmodes (1, 2, 3 ...), offers additional freedom besides wavelength, amplitude and polarization, provides much more information capacity, and finds optical communication applications in both classical and quantum optics [3], [4]. The central darkness of the intensity distribution of OV has been proved to be more suitable for trapping non-transparent or low-refractive-index objects [5], [6]. The generation, modulation, and application of OV have been widely concerned
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