Performance improvement of three-body radiative diodes driven by graphene surface plasmon polaritons.

As an analogue to an electrical diode, a radiative thermal diode allows radiation to transfer more efficiently in one direction than in the opposite direction by operating in a contactless mode. In this study, we demonstrated that within the framework of three-body photon thermal tunneling, the rectification performance of a three-body radiative diode can be greatly improved by bringing graphene into the system. The system is composed of three parallel slabs, with the hot and cold terminals of the diode coated with graphene films and the intermediate body made of vanadium dioxide (VO).

Lattice Boltzmann modeling of two-phase electrohydrodynamic flows under unipolar charge injection.

In this work, a two-dimensional droplet confined between two parallel electrodes under the combined effects of a nonuniform electric field and unipolar charge injection is numerically investigated using the lattice Boltzmann method (LBM). Under the non-Ohmic regime, the interfacial tension and electric forces at the droplet surface cooperate with the volumetric Coulomb force, leading to complex deformation and motion of the droplet while at the same time inducing a bulk electroconvective flow. After we validate the model by comparing with analytical solutions at the hydrostatic state, we perform a quantitative analysis on the droplet deformation factor D and bulk flow stability criteria T_{c} under different parameters, including the electric capillary number Ca, the electric Rayleigh number T, the permittivity ratio ɛ_{r}, and the mobility ratio K_{r}.

Efficient lattice Boltzmann method for electrohydrodynamic solid-liquid phase change.

Melting in the presence of electrohydrodynamic (EHD) flow driven by the Coulomb force in dielectric phase change material is numerically studied. A model is developed for the EHD flow in the solid-liquid phase change process. The fully coupled equations including mechanical equations, electrical equations, energy equations, and the continuity equations in the solid-liquid interface are solved using a unified lattice Boltzmann model (LBM).

Multiscale solutions of radiative heat transfer by the discrete unified gas kinetic scheme.

The radiative transfer equation (RTE) has two asymptotic regimes characterized by the optical thickness, namely, optically thin and optically thick regimes. In the optically thin regime, a ballistic or kinetic transport is dominant. In the optically thick regime, energy transport is totally dominated by multiple collisions between photons; that is, the photons propagate by means of diffusion.

First-principles investigations of manganese oxide (MnO ) complex-sandwiched bilayer graphene systems.

In this paper, we calculate the structural, electronic, magnetic and optical parameters of MnO ( = 0-4), cluster-sandwiched bilayer graphene (Gr) systems, utilizing first-principles calculations with van der Waals corrections implemented with density functional theory (DFT). Charge transfer is observed from the graphene layers to the MnO clusters, thus producing a hole doping phenomenon in the graphene layers. The MnO clusters' electronegative nature greatly modifies the electronic structure of bilayer graphene.

Responses transition in a monolayer Al-AlO nanoparticle-crystal due to oxidation.

Nanoparticle is a promising candidate for large scale fabrication of metamaterial. However, optical responses for metamaterial made of abound metal like Al can be thoroughly changed due to oxidization. Especially for nanoparticle whose aspect ratio is extremely high, oxidation usually occurs.

Graphene plasmonics for surface enhancement near-infrared absorptivity.

Monolayer graphene has poor absorption in the near-infrared region. Its layer is only as thick as a single atom so it cannot have a high absorptivity. In this paper, in order to form a hybrid system, the absorption characteristics of monolayer graphene covering a metal/dielectric/metal substrate has been theoretically analyzed.

Transient/time-dependent radiative transfer in a two-dimensional scattering medium considering the polarization effect.

Transient/time-dependent radiative transfer in a two-dimensional scattering medium is numerically solved by the discontinuous finite element method (DFEM). The time-dependent term of the transient vector radiative transfer equation is discretized by the second-order central difference scheme and the space domain is discretized into non-overlapping quadrilateral elements by using the discontinuous finite element approach. The accuracy of the transient DFEM model for the radiative transfer equation considering the polarization effect is verified by comparing the time-resolved Stokes vector component distributions against the steady solutions for a polarized radiative transfer problem in a two-dimensional rectangular enclosure filled with a scattering medium.

Nanoparticle-crystal towards an absorbing meta-coating.

In this paper, a double layer nanoparticle-crystal has been proposed, which shown incident and polarization angle, substrate independences for spectral absorptivity. Such phenomenon originates from the near-field light redistribution and excitation of internal collective oscillating. This kind of nanoparticle-crystal can be made of various types of metal with similar optical responses.

Multi-focused microlens array optimization and light field imaging study based on Monte Carlo method.

Plenoptic cameras are used for capturing flames in studies of high-temperature phenomena. However, simulations of plenoptic camera models can be used prior to the experiment improve experimental efficiency and reduce cost. In this work, microlens arrays, which are based on the established light field camera model, are optimized into a hexagonal structure with three types of microlenses.

Transient polarized radiative transfer analysis in a scattering medium by a discontinuous finite element method.

Transient (time-dependent) polarized radiative transfer in a scattering medium exposed to an external collimated beam illumination is conducted based on the time-dependent polarized radiative transfer theory. The transient term, which persists the nanosecond order time and cannot be ignored for the time-dependent radiative transfer problems induced by a short-pulsed beam, is considered as well as the polarization effect of the radiation. A discontinuous finite element method (DFEM) is developed for the transient vector radiative transfer problem and the derivation of the discrete form of the governing equation is presented.

Direct wavefront manipulating for a transverse electric wave microlens.

Due to the polarization nature of the transverse electric electromagnetic wave, manipulating it has been a difficult task and can be even more challenging for integrated on-chip optics. In this Letter, a transverse electric wave manipulating method based on direct wavefront bending and its physical picture have been proposed. Even with only five cells, the microlens can exhibit a focusing pattern and retrieve sub-wavelength spatial features.

Correction model for microlens array assembly error in light field camera.

In a light field camera, a microlens array (MLA) assembly error can affect the quality of the image. In this study, aiming to ensure corrective imaging using a light field camera, we accurately evaluate and eliminate the assembly error. We used an error image and a standard image to confirm the MLA assembly error, and we developed an assembly error correction model combined with an image quality evaluation index to correct the error.

Lattice Boltzmann model for a steady radiative transfer equation.

A complete lattice Boltzmann model (LBM) is proposed for the steady radiative transfer equation (RTE). The RTE can be regarded as a pure convection equation with a source term. To derive the expressions for the equilibrium distribution function and the relaxation time, an artificial isotropic diffusion term is introduced to form a convection-diffusion equation.

Vector radiative transfer in a multilayer medium by natural element method.

The vector radiative transfer problem in a vertically multilayer scattering medium with spatial changes in the index of refraction is solved by the natural element method (NEM). The top boundary of the multilayer medium is irradiated by a collimated beam. In our model, the angular space is discretized by the discrete ordinates approach, and the spatial discretization is conducted by the Galerkin weighted residuals approach.

Lattice Boltzmann model for Coulomb-driven flows in dielectric liquids.

In this paper, we developed a unified lattice Boltzmann model (LBM) to simulate electroconvection in a dielectric liquid induced by unipolar charge injection. Instead of solving the complex set of coupled Navier-Stokes equations, the charge conservation equation, and the Poisson equation of electric potential, three consistent lattice Boltzmann equations are formulated. Numerical results are presented for both strong and weak injection regimes, and different scenarios for the onset and evolution of instability, bifurcation, and chaos are tracked.

Local radial basis function meshless scheme for vector radiative transfer in participating media with randomly oriented axisymmetric particles.

A local radial basis function meshless scheme (LRBFM) is developed to solve polarized radiative transfer in participating media containing randomly oriented axisymmetric particles in which radial basis functions augmented with polynomial basis are employed to construct the trial functions, and the vector radiative-transfer equation based on the discrete-ordinates approach is discretized directly by collocation method. The LRBFM belongs to a class of truly meshless methods that do not need any mesh or any numerical integration scheme. Performances of the LRBFM are verified with analytical solutions and other numerical results reported earlier in the literature via five various test cases.

Optical coherent thermal emission by excitation of magnetic polariton in multilayer nanoshell trimer.

A theoretical demonstration is given of coherent thermal emission via the visible region by exciting magnetic polaritons in isolated metal-dielectric-metal multilayer nanoshells and the collective behavior in a trimer comprising multilayer nanoshells. The dipolar metallic core induces magnetic polaritons in the dielectric shell creating a large enhancement of the emissivity, whose mechanism is different from that of film-coupled metamaterials. The coupling effect of the magnetic polaritons and the electric/magnetic modes of symmetric nanoparticle trimers is discussed to understand the collective behavior in self-assembled nanoparticle clusters with potential solar energy utilizations.

Short-pulsed laser transport in two-dimensional scattering media by natural element method.

The natural element method (NEM) is extended to solve transient radiative transfer (TRT) in two-dimensional semitransparent media subjected to a collimated short laser irradiation. The least-squares (LS) weighted residuals approach is employed to spatially discretize the transient radiative heat transfer equation. First, for the case of the refractive index matched boundary, LSNEM solutions to TRT are validated by comparison with results reported in the literature.

Polarized radiative transfer in an arbitrary multilayer semitransparent medium.

Polarized radiative transfer in a multilayer system is an important problem and has wide applications in various fields. In this work, a Monte Carlo (MC) model is developed to simulate polarized radiative transfer in a semitransparent arbitrary multilayer medium with different refractive indices in each layer. Two kinds of polarization mechanisms are considered: scattering by particles and reflection and refraction at the Fresnel surfaces or interfaces.

Approximate solution to vector radiative transfer in gradient-index medium.

Within a gradient-index medium, the radiative rays propagate in curved paths, which makes polarized states change continuously and the solution to the radiative transfer be thus more complex and difficult. In this paper, an arbitrary multilayer model is developed to approximately simulate vector (polarized) radiative transfer in a gradient-index plane-parallel medium. The gradient-index medium is divided into an arbitrary number of sublayers, and each sublayer has a uniform refractive index and two virtual Fresnel's interfaces where only transmission (refraction) is considered.

Lattice Boltzmann method for one-dimensional radiation transfer.

The macroscopic conservation equations of radiation energy and radiation momentum are derived on the basis of radiation hydrodynamics. Based on the Chapman-Enskog method, the lattice Boltzmann model for one-dimensional radiative transfer is proposed from the Boltzmann equation. The numerical simulation results agree well with the exact solution and show that the lattice Boltzmann method developed in this paper has good accuracy and stability for solving one-dimensional radiative transfer problems.