A liquid crystal lens array with a hexagonal arrangement is investigated experimentally. The uniqueness of this study exists in the fact that using convex-ring electrode provides a smooth and controllable applied potential profile across the aperture to manage the phase profile. We observed considerable differences between flat electrode and convex-ring electrode; in particular the lens focal length is variable in a wider range from 2.5cm to infinity. This study presents several noteworthy characteristics such as low driving voltage; 30 μm cell gap and the lens is electrically switchable between 2D/3D modes. We demonstrate a hexagonal LC-lens array for capturing 3D images by using single sensor using integral imaging.

No abstract

Metasurface operating in the transmission scheme has shown a promising scenario for flat optics applications. Nevertheless, the inherently low working efficiency of transmissive plasmonic metasurfaces at optical frequencies severely hinders them from future technology development. This work reports on a hybrid plasmonic meta‐atom (HPMA) with a simple fabrication and cost‐effective single‐lithographic process featuring a toroidal‐assisted generalized Huygens’ source with a state‐of‐the‐art circular polarization conversion efficiency beyond 50%. The HPMA representsa new upper limit for transmission efficiency in the near‐infrared. The high transmission is realized via balanced multipoles of different orders including toroidal dipole that satisfies the generalized Kerker condition. The introduction of toroidal dipole provides an additional degree of freedom to tailor the wave interference and radiation symmetry rather than the use of a conventional electric and magnetic multipolar coupling. In addition, two high‐performance metasurfaces by combining the HPMAs with the geometric phase method are highlighted. The highly‐transmissive beam deflection metasurface and plasmonic metalens respectively yield anomalous refraction with 38.2% optical efficiency and 46.56% focusing efficiency, both experimentally showing a record transmission level. The findings may open new ways to design highly‐efficient plasmonic metasurfaces and to take one step forward to facilitate nearly optimal and practical nanophotonic devices.

In this paper, we demonstrate a multi-functional liquid-crystal lens (MFLC-lens) based on dual-layer electrode design. Compared with the previous 3D endoscopes, which use double fixed lens capturing, the proposed LC lens is not only switchable between 2D and 3D modes, but also is able to adjust focus in both modes. The diameter of the MFLC-lens is only 1.42mm, which is much smaller than the available 3D endoscopes with double fixed lenses. To achieve the MFLC-lens, a high-resistance layer needs to be coated on the electrode to generate an ideal gradient electric-field distribution, which can induce a lens-like form of LC molecules. The parameters of high-resistive layer are investigated and discussed with an aim to optimize the performance of the MFLC-lens.

The recent progress in plasmonic metasurfaces gives rise to an intense evolution of controlling light properties such as phase, amplitude, polarization, and frequency. In this work, a new paradigm is established to control the light properties centered on low‐loss toroidal multipoles with high field enhancement in contrast to most of the previous plasmonic metasurfaces that are optimized through electric and magnetic multipolar resonances. Through a proof‐of‐concept demonstration, a linear cross‐polarization conversion efficiency reaching 22.9%, remarked as the optimal value that can exist in a single‐layer plasmonic metasurface in the near‐infrared spectrum, is experimentally realized. A polarization‐insensitive toroidal response, that previously was accessible only in isotropic high‐index metasurfaces, is also observed. Furthermore, a giant anisotropic (polarization‐sensitive) generation of the second‐harmonic frequency is demonstrated with the proposed polarization‐independent toroidal metasurface that provides different levels of electric energy storage within the metasurface. These findings open a new path for keeping low‐efficiency plasmonic components on track when one engineers a metasurface based on the toroidal multipole family.