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Extreme light confinement observed in periodic photonic structures, such as the vortex singularities in momentum (k) space, has been associated with their topological nature. Consequently, by exploiting and tuning their topological properties, optical metasurfaces have been demonstrated as an attractive platform for active photonics. However, given the fact that most active media under external excitations can only provide limited refractive index change, the potential advancements offered by the topological character of active metasurfaces have remained mostly unexplored. Zinc oxide (ZnO), which has recently exhibited optically-induced extraordinarily large permittivity modulations at visible and near-infrared frequencies, is an excellent active material for dynamic metasurfaces exhibiting strong tuning. This work demonstrates that a hybrid metasurface consisting of an array of ZnO nanodisks on a silver backplane displays broadly tunable topological properties. In particular, by performing k-space scattering simulations using measured pump-fluence-dependent material properties of ZnO, we study in detail the light reflection from the hybrid metasurface. Our results validate that the large k-space topology tuning of the metasurface can result in enormously strong polarization manipulation of near-infrared light in the vicinity of the topological features. The observed polarization switching effect is highly sensitive to the polarization and wavelength of an incident wave, owing to the symmetry and dispersion characteristics of the proposed system. Our study indicates that leveraging a combination of the extraordinary material properties and the k-space topology, hybrid metasurfaces based on ZnO may open new avenues for creating all-optical switchable metadevices.

Optical metasurfaces, planar subwavelength nanoantenna arrays with the singular ability to sculpt wavefront in almost arbitrary manners, are poised to become a powerful tool enabling compact and high-performance optics with novel functionalities. A particularly intriguing research direction within this field is active metasurfaces, whose optical response can be dynamically tuned postfabrication, thus allowing a plurality of applications unattainable with traditional bulk optics. Designing reconfigurable optics based on active metasurfaces is, however, presented with a unique challenge, since the optical quality of the devices must be optimized at multiple optical states. In this article, we provide a critical review on the active meta-optics design principles and algorithms that are applied across structural hierarchies ranging from single meta-atoms to full meta-optical devices. The discussed approaches are illustrated by specific examples of reconfigurable metasurfaces based on optical phase-change materials.

The East Tianshan Mountain is one of the most important gold ore forming zones in northwestern China and central Asia. The Chinese GaoFen-1 (GF-1), the first Chinese high resolution satellite, is characterized by its 2-m resolution PAN data. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), the well-known earth observation satellite, is advanced by its finer spectral resolution owing 9 bands in the visible and near infrared (VNIR) to the short-wave infrared (SWIR) region. In this study, we fused the GF-1 PAN and the ASTER multispectral data using the well-known Gram-Schmidt Pan Sharpening (G-S) method to produce a new data with both high spatial and spectral resolution. Then different lithological units were mapped respectively using the fusion data, the ASTER data and the WorldView-3 data by support vector machine (SVM) method. In order to assess this fusion data, a comparison work was executed among the three mapping results. The comparison work indicated that lithological classification using the new fusion data is an efficient, robust and low cost method, and it could replace the WV-3 data in some large sale geological work.

C27H34N4O3S2, monoclinic, P21/c (no. 14), a = 17.7267(7) Å, b = 10.5415(5) Å, c = 14.1637(4) Å, β = 91.644(3)°, V = 2645.62(18) Å3, Z = 4, Rgt(F) = 0.0620, wRref(F2) = 0.2008, T = 293(2) K.

C27H34N4O3S2, monoclinic, P21/ c (no. 14), a = 17.7267(7) Å, b = 10.5415(5) Å, c = 14.1637(4) Å, β = 91.644(3)°, V = 2645.62(18) Å3, Z = 4, Rgt( F) = 0.0620, wRref( F2) = 0.2008, T = 293(2) K. [ABSTRACT FROM AUTHOR]

C27H34N4O3S2, monoclinic, P21/ c (no. 14), a = 17.7267(7) Å, b = 10.5415(5) Å, c = 14.1637(4) Å, β = 91.644(3)°, V = 2645.62(18) Å3, Z = 4, Rgt( F) = 0.0620, wRref( F2) = 0.2008, T = 293(2) K. [ABSTRACT FROM AUTHOR]