RESUMEN
Mie-resonant dielectric metasurfaces offer comprehensive opportunities for the manipulation of light fields with high efficiency. Additionally, various strategies for the dynamic tuning of the optical response of such metasurfaces were demonstrated, making them important candidates for reconfigurable optical devices. However, dynamic control of the light-emission properties of active Mie-resonant dielectric metasurfaces by an external control parameter has not been demonstrated so far. Here, we experimentally demonstrate the dynamic tuning of spontaneous emission from a Mie-resonant dielectric metasurface that is situated on a fluorescent substrate and embedded into a liquid crystal cell. By switching the liquid crystal from the nematic state to the isotropic state via control of the cell temperature, we induce a shift of the spectral position of the metasurface resonances. This results in a change of the local photonic density of states, which, in turn, governs the enhancement of spontaneous emission from the substrate. Specifically, we observe spectral tuning of both the electric and magnetic dipole resonances, resulting in a 2-fold increase of the emission intensity at λ ≈ 900 nm. Our results demonstrate a viable strategy to realize flat tunable light sources based on dielectric metasurfaces.
RESUMEN
The peculiarities of the linearly polarized light beam reflection at the interface within the bulk of a nematic liquid crystal (NLC) cell with different orientations of the director are analyzed. Two methods to create the interface are considered. Combination of the planar and homeotropic orientations of the NLC director is realized by means of a spatially structured electrode under the applied voltage. In-plane patterned azimuthal alignment of the NLC director is created by the patterned rubbing alignment technique. All possible orthogonal orientations of the LC director are considered; the configurations for realization of total internal reflection are determined. The revealed relationship between the propagation of optical beams in a liquid crystal material and polarization of laser radiation has enabled realization of the spatial separation for the orthogonally polarized light beams at the interface between two regions of NLC with different director orientations (domains). Owing to variations in the applied voltage and, hence, in the refractive index gradient, the light beam propagation directions may be controlled electrically.
RESUMEN
The development of a miniaturised device that provides efficient beam manipulation with high transmittance is extremely desirable for the broad range of applications including holography, metalens, and imaging. Recently, the potential of dielectric metasurfaces has been unleashed to efficiently manipulate the beam with full 2π-phase control by overlapping the electric and magnetic dipole resonances. However, in the visible range for available materials, it comes with the price of higher absorption that reduces efficiency. Here, we have considered dielectric amorphous silicon (a-Si) nanodisk and engineered them in such a way which provides minimal absorption loss in the visible range. We have experimentally demonstrated meta-deflector with high transmittance which operates in the visible wavelengths. The supercell of proposed meta-deflector consists of 15 amorphous silicon nanodisks numerically shows the transmission efficiency of 95% and deflection efficiency of 95% at operating wavelength of 715 nm. However, experimentally measured transmission and deflection efficiencies are 83% and 71%, respectively, having the experimental deflection angle of 8.40°. Nevertheless, by reducing the supercell length, the deflection angle can be controlled, and the value 15.50° was experimentally achieved using eight disks supercell. Our results suggest a new way to realise the highly transmittance metadevice with full 2π-phase control operating with the visible light which could be applicable in the imaging, metalens, holography, and display applications.