Based on an integrated array of refractory titanium nitride (TiN), a metasurface perfect absorber (MPA) in the visible-to-near infrared (NIR) band is reported. The systematic and detailed simulation study of the absorption of the MPA is performed with the finite-different time-domain (FDTD) method. Tailoring the structure, the MPA realizes as high an average as 99.6% broadband absorption, ranging from 400 nm to 1500 nm. The broadband perfect absorption can be attributed to localized surface plasmonic resonance (LSPR), excited by the continuous diameter evolution from the apex to the base of the nanocone, and the gap plasmons excited among the nanocones, as well as in the spacer layer at longer wavelengths. Particularly, the coupling of the resonances is essentially behind the broadening of the absorption spectrum. We also evaluated the electric field intensity and polarization-dependence of the nanocone MPA to offer further physical insight into light trapping capability. The MPA shows about 90% average absorption even at an oblique incidence up to 50°, which improves the acceptance capability of light-harvesting system applications. This unique design with the TiN nanocone array/aluminium oxide (Al2O3)/TiN structure shows potential in imminent applications in light trapping and thermophotovoltaics.
The present study provides a deeply analysis of the flow
behavior of bubbling fluidized beds with fine particles in two- (2D)
and three-dimensional (3D) conditions, and computational fluid dynamics
(CFD) simulations of agglomerates fluidization are carried out coupled
with the modified agglomerate-force balance model, correspondingly.
The experimental results indicate that the fluidized bed can be divided
into bottom unfluidized, middle ascending fluidized, and upper descending
back-mixing sections. The local solids volume fraction value ranges
from 0.11 to 0.30, which depends on the interaction between bubble
phase (εs = 0–0.04) and emulsion phase (εs = 0.26–0.30). The wall effect appears to be weakened,
and the cohesive particles fluidize more uniformly in 3D fluidized
beds. The simulations are in reasonable agreement with the experimental
findings. However, at the top region of the bed the predicted solids
holdup slightly deviates from experimental measurement. The vector
plots of computed agglomerates velocity support the central and wall
falling down-both sides rising up flow pattern of solids, two core-annular
flows exist in the bed, which can be also observed experimentally.
Two-dimensional electron gases (2DEGs) were demonstrated in indium–tin–oxide (ITO)-coated lithium niobate (LN) slabs by monitoring the very first reflection (VFR). Being dictated by light–matter interaction within the half-a-wavelength range, two-fold enhancement of the VFR was observed at one incidence angle, while two-and-half-fold reduction was obtained at another angle, when illuminating a Z-cut ITO–LN slab with two laser beams at 532 nm from the same side. In terms of exponential gain coefficient, such VFR enhancement/reduction corresponds to a range from −7.416 × 104 cm−1 to +4.68 × 104 cm−1, three orders of magnitude higher than that expected from the conventional photorefractive (PR) theory. The nanometer-thick 2DEG and the coupling role played by the evanescent field of the surface plasmon polaritons (SPPs) impose a much looser coherency requirement for the interacting light beams, which was verified by the solid energy coupling observed while rotating the polarization state of one laser beam. As much as 18.4 mW of the side diffraction mode associated with the light track formed on the slab surface, which sheds some light on the dramatic coupling dynamics. All these findings above were far beyond the reach of conventional PR theory, yet well consistent with the physical picture of 2DEG-supported SPPs and their interactions at the ITO–LN interface, offering a good opportunity to conceive and design future photonic/electronic devices for optical modulators.
The surfaces of some IIB-VI semiconductors (ZnX, X=O, S, Se) were metallized by neighboring highly polar and atomically vertically aligned (VA) liquid crystal (LC) molecules. Due to polar catastrophe, the...
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