Photonic analogue of topological insulator was recently predicted by arranging e/m (permittivity/permeability)-matched bianisotropic metamaterials into two-dimensional superlattices. However, the experimental observation of such photonic topological insulator is challenging as bianisotropic metamaterial is usually highly dispersive, so that the e/mmatching condition can only be satisfied in a narrow frequency range. Here we experimentally realize a photonic topological insulator by embedding non-bianisotropic and non-resonant metacrystal into a waveguide. The cross coupling between transverse electric and transverse magnetic modes exists in metacrystal waveguide. Using this approach, the e/m-matching condition is satisfied in a broad frequency range which facilitates experimental observation. The topologically non-trivial bandgap is confirmed by experimentally measured transmission spectra and calculated non-zero spin Chern numbers. Gapless spin-filtered edge states are demonstrated experimentally by measuring the magnitude and phase of the fields. The transport robustness of the edge states is also observed when an obstacle was introduced near the edge.

A mononuclear iron(II) complex has been isolated in two polymorphs. Polymorph 1b remains high-spin over all temperatures, whereas polymorph 1a undergoes a cooperative two-step spin crossover accompanied by symmetry breaking, showing an ordered 2:1 high-spin-low-spin intermediate phase.

Optical image encryption, especially double-random-phase-based, is of great interest in information security. In this work, we experimentally demonstrate the security and feasibility of optical image encryption with asymmetric double random phase and computer-generated hologram (CGH) by using spatial light modulator. First of all, the encrypted image modulated by asymmetric double random phase is numerically encoded into real-value CGH. Then, the encoded real-value CGH is loaded on the spatial light modulator and optically decrypted in self-designed experimental system. Experimental decryption results are in agreement with numerical calculations under the prober/mistaken phase keys condition. This optical decryption technology opens a window of optical encryption practical application and shows great potential for digital multimedia product copyright protection and holographic false trademark.

Based on a mode-expansion theory under single-mode approximation, we derived the scatterings parameters for a general one-dimensional photonic grating composed of two different materials, and then established an effective-medium theory for such a composite by equating the obtained scattering parameters to those of a homogeneous medium. Our effective-medium theory well describes the grating structures with general material and geometrical parameters, and recovers two previous formulas, which are valid only at certain limiting conditions. The theory is justified by full-wave simulations and microwave experiments.

With quasi-periodic microstructures, great enhancement of infrared light absorption of Au film over a broad wavelength band (2.7~15.1 μm) was realized experimentally for the first time. The microstructured Au film was prepared by replica molding of the surface of femtosecond (fs) laser microstructured silicon (black silicon). This unique absorption characteristic is mainly ascribed to good impedance match from free space to Au film. The surface of the sample was examined by X-ray photoelectron spectroscopy (XPS) and the four peaks of absorptance were ascribed to residual polydimethylsiloxane (PDMS), H2SO4, adsorbed water and CO2 in the air, respectively.