Search

The black phosphorus (BP)/hexagonal boron nitride (hBN) Van der Waals heterostructure has great potential application in BP-based devices due to its higher stability than monolayer BP film. The near-field thermal radiation (NFTR) between two identical BP/hBN heterostructures with high electron density is studied to promote the application of BP-based devices. The BP/hBN heterostructures show a higher heat transfer coefficient (HTC) at a 10 nm gap distance compared to BP films with electron density n larger than 1 × 1013 cm−2, due to the coupling of surface plasmon polaritons (SPPs) and hyperbolic phonon polaritons (HPPs). Especially at n ≥ 3 × 1013 cm−2, the improvement is more than 100%. The SPPs and the HPPs couple into surface plasmon-phonon polaritons (SPPPs) out of the hyperbolic region and hyperbolic plasmon-phonon polaritons (HPPPs) inside. The SPPPs can achieve photon tunneling in the broader wavevector region than SPPs, making most of the contribution to heat transfer. The influences of the thickness of the hBN sheet and gap distance are also discussed. This scheme only effectively enhances NFTR for BP with high electron density at small nanogaps. After structural optimization, h = 2 nm is the optimal thickness for BP/hBN configuration with low electron density, such as n = 1 × 1013 cm−2. In contrast, large thickness h = 500 nm is optimal for BP with high electron density. At high electron density, a thick hBN sheet is prominent in enhancing the SPPPs in the frequencies below the type-I region and the HPPPs inside the type-II region. We further propose BP/hBN/BP heterostructures and find that HTC is further enhanced by 4.4% ~ 30.8% due to the more robust surface modes. Our work may contribute to developing BP-based near-field thermal devices and promote understanding the NFTR mechanism of BP/hBN heterostructure. [ABSTRACT FROM AUTHOR]

Modes have steadily influenced the understanding of physical systems through time. At least since the prediction of the Casimir effect, they also play a very important role in Casimir physics and in the understanding of the different phenomena typical of this research field. At equilibrium modes provide a direct connection between the zero-point energy and the existence of irreducible fluctuations in a quantum system, offering an anatomic view into the physics of the interaction. In nonequilibrium systems, modes can be decisive to understand the behavior of quantum fluctuation-induced phenomena, highlighting key aspects which determine their strength and their functional dependence. In this article we review some recent studies and results that highlight how modes impact Casimir physics and the central role they play in shaping our understanding of this area of research. [ABSTRACT FROM AUTHOR]

Abstract The Gent–McWilliams parameterization is commonly used in global ocean models to model the advective component of tracer transport effected by unresolved mesoscale eddies. The vertical structure of the transfer coefficient in this parameterization is studied using data from a 0.1° resolution global ocean‐ice simulation. The vertical structure is found to be well approximated by a baroclinic mode structure with no flow at the bottom, though horizontal anisotropy is crucial for obtaining a good fit. This vertical structure is motivated by reference to the vertical structure of mesoscale eddy velocity and density anomalies, which are also diagnosed from the data.

The authors solve the problem of estimating the best rotation aligning two sets of corresponding vectors (also known as Wahba's problem or point cloud registration). The proposed method is among the fastest methods reported in recent literatures, moreover it is robust to noise, accurate and simpler than most other methods. It is based on solving the linear equations derived from the formulation of the problem in Euclidean Geometric Algebra. The authors show its efficiency in two applications: the as-rigid-as-possible (ARAP) surface modelling and the more smooth rotation enhanced ARAP mesh animation which is the only method capable of deforming surface modes with quality of tetrahedral models. Mesh deformation is a key technique in games, automated construction and robotics. The ARAP technique along with its improved variants, although have been extensively studied, can still not be achieved efficiently. Linear geometric algebra based rotor solution proposed in this study gives another perspective of the kernel problem. This, however, not only improves the real performance of the three-dimensional mesh deformation, but also provides a brand new computationally efficient solution to the Wahba's problem and point cloud registration, which has been closely related to the automation science and engineering.

This article reports refractometric sensing using two optical resonances of different types supported by TiO2 nanopillar arrays on a gold film, which can be exposed to aqueous or organic environments. One lattice resonance, with enhanced electric fields extending into the surrounding environment, can maintain a quality factor Q > 200 when the bulk refractive index of the surrounding environment varies in a large range from 1.33 to 1.58. This lattice resonance exhibits not only sharp transitions of reflected light intensity but also rapid phase changes. The other resonance is of plasmonic nature with electric fields localized on the metal surface. Small changes in the bulk refractive index or the adsorbate layer (thickness and index) can be detected, with sensitivity comparable to that of plasmonic counterparts. The present hybrid metal–dielectric platform is promising for applications requiring dielectric instead of metallic sensing surfaces. [ABSTRACT FROM AUTHOR]

We investigate both theoretically and experimentally the properties of electromagnetic waves propagation and localization in periodic and quasi-periodic stub structures of Fibonacci type. Each block constituting the Fibonacci sequence (FS) is composed of an horizontal segment and a vertical stub. The origin of the primary and secondary gaps shown in such systems is discussed. The behaviors and scattering properties of the electromagnetic modes are studied in two geometries, when the FS is inserted horizontally between two semi-infinite waveguides or grafted vertically along a guide. Typical properties of the Fibonacci systems such as the fragmentation of the frequency spectrum, the self-similarity following a scaling law are analyzed and discussed. It is found that certain modes inside these two geometries decrease according to a power law rather than an exponential law and the localization of these modes displays the property of self-similarity around the central gap frequency of the periodic structure where the quasi-periodicity is most effective. Also, the eigenmodes of the FS of different generation order are studied depending on the boundary conditions imposed on its extremities. It is shown that both geometries provide complementary information on the localization of the different modes inside the FS. In particular, in addition to bulk modes, some localized modes induced by both extremities of the system exhibit different behaviors depending on which surface they are localized. The theory is carried out using the Green's function approach through an analysis of the dispersion relation, transmission coefficient and electric field distribution through such finite structures. The theoretical findings are in good agreement with the experimental results performed by measuring in the radio-frequency range the transmission along a waveguide in which the FS is inserted horizontally or grafted vertically. [ABSTRACT FROM AUTHOR]

The Gent–McWilliams parameterization is commonly used in global ocean models to model the advective component of tracer transport effected by unresolved mesoscale eddies. The vertical structure of the transfer coefficient in this parameterization is studied using data from a 0.1° resolution global ocean‐ice simulation. The vertical structure is found to be well approximated by a baroclinic mode structure with no flow at the bottom, though horizontal anisotropy is crucial for obtaining a good fit. This vertical structure is motivated by reference to the vertical structure of mesoscale eddy velocity and density anomalies, which are also diagnosed from the data. Plain Language Summary: Ocean mesoscale eddies transport tracers like heat, salt, and dissolved carbon dioxide, inter alia. In numerical models where these eddies are not resolved, their effects need to be parameterized. This research addresses the vertical structure of a widely used parameterization, and connects the results to vertical structure of the eddies themselves. Key Points: The Gent–McWilliams (GM) coefficient matrix is diagnosed from an eddy‐resolving simulationThe vertical structure of GM is well modeled by a surface modeHorizontal anisotropy is crucial for obtaining a good fit [ABSTRACT FROM AUTHOR]

A state-of-the-art fiber optic gyroscope (FOG) using a 250-m quadrupolar-wound coil of polarization-maintaining hollow-core fiber (HCF) interrogated by a broadened laser is demonstrated. The fiber coil is directly connected to the multi-function integrated optics chip (MIOC) to reduce instabilities and reflections. The HCF FOG is first driven with a broadband source, yielding an angular random walk (ARW) of 2.12  μrad/√Hz and a drift of 0.375 μrad. This drift is 3.4 times lower than reported in any previous HCF FOG. Measuring the loss and ARW versus wavelength of the HCF FOG driven by a tunable narrow-linewidth laser reveals that the HCF supports a dense spectrum of high-scattering surface modes (∼70 modes/nm). The HCF FOG was also interrogated with a 22.5-GHz broadened-laser source, yielding an ARW of 6 μrad/√Hz. This ARW is most likely limited by backscattering mediated by coupling to the high-scattering surface modes. The drift of the HCF FOG driven by the broadened laser was 0.88 μrad. This drift is limited by polarization coupling, and confirms the holding parameter given by the fiber provider for this fiber (10−3 m−1). [ABSTRACT FROM AUTHOR]

A novel interferometric technique for studies of exothermal chemical reactions at the water surface is presented. The key feature of the technique is the use of an air bubble as the interface which hosts coating molecules and at the same time acts as a subnanometer-sensitive Fabry-Perot interferometer which follows the bubble radius change after a chemical reaction with coating molecules. As an example we report measurements of a protonation reaction with dodecyl-amine (DA). A monolayer of the DA surfactant is formed at the gas-liquid interface of a millimeter-sized bubble immersed in a 10.6 pH solution. After the monolayer formation, the residual DA is removed from the bulk by gentle rinsing. Interference with the DA bulk reaction is avoided. Protonation is induced by HCl injection. The reaction in the thin DA coating layer generates a non-trivial evolution of the bubble radius with amplitude oscillations of the order of 10−3 of the bubble radius with persisting time of a few hundred seconds. Measurements are performed at different DA coverages of the bubble surface, always below the maximum coverage. Control experiments with non-coated bubble show no amplitude radius oscillations. Formation and stability of the DA monolayer are precisely monitored by measurements of the lowest-frequency bubble capillary mode. A possible interpretation of the experiments is given in terms of heat effects, vapor production and surface modification. Molecular Dynamics simulations provide a mechanistic understanding of surface effects triggered by the protonation reaction which promotes desorption of positively charged DA micelles. [Display omitted] [ABSTRACT FROM AUTHOR]

We investigate both theoretically and experimentally the properties of electromagnetic waves propagation and localization in periodic and quasi-periodic stub structures of Fibonacci type. Each block constituting the Fibonacci sequence (FS) is composed of an horizontal segment and a vertical stub. The origin of the primary and secondary gaps shown in such systems is discussed. The behaviors and scattering properties of the electromagnetic modes are studied in two geometries, when the FS is inserted horizontally between two semi-infinite waveguides or grafted vertically along a guide. Typical properties of the Fibonacci systems such as the fragmentation of the frequency spectrum, the self-similarity following a scaling law are analyzed and discussed. It is found that certain modes inside these two geometries decrease according to a power law rather than an exponential law and the localization of these modes displays the property of self-similarity around the central gap frequency of the periodic structure where the quasi-periodicity is most effective. Also, the eigenmodes of the FS of different generation order are studied depending on the boundary conditions imposed on its extremities. It is shown that both geometries provide complementary information on the localization of the different modes inside the FS. In particular, in addition to bulk modes, some localized modes induced by both extremities of the system exhibit different behaviors depending on which surface they are localized. The theory is carried out using the Green’s function approach through an analysis of the dispersion relation, transmission coefficient and electric field distribution through such finite structures. The theoretical findings are in good agreement with the experimental results performed by measuring in the radio-frequency range the transmission along a waveguide in which the FS is inserted horizontally or grafted vertically.

Abstract Radiative heat transfer in systems with core-shell nanoparticles may exhibit not only a combination of disparate physical properties of its components but also further enhanced properties that arise from the synergistic properties of the core and shell components. We study the thermal conductance between two core-shell nanoparticles (CSNPs). The contribution of electric and magnetic dipole moments to the thermal conductance depend sensitively on the core and shell materials, and adjustable by core size and shell thickness. We predict that the radiative heat transfer in a dimer of Au@SiO 2 CSNPs (i.e., silica-coated gold nanoparticles) could be enhanced several order of magnitude compared to bare Au nanoparticles. However, the reduction of several orders of magnitude in the heat transfer is possible between SiO 2 @Au CSNPs (i.e., silica as a core and gold as a shell) than that of uncoated SiO 2 nanoparticles. [ABSTRACT FROM AUTHOR]

The near-field radiative heat flux between two two-dimensional sinusoidal grating surfaces made of doped-silicon is investigated by the finite difference time domain (FDTD) method. The parameter Λ, which is defined as the ratio of the amplitude to the period of the two-dimensional sinusoidal grating surface, is used to characterize the surface feature. When the amplitude is much smaller than the period, the surface effect is not significant to modify the near-field radiative heat flux between two smooth films. However, when the amplitude is comparable with the period, the near-field radiative heat flux between two smooth films can be enhanced remarkably. The coupling of the localized surface modes between the may be responsible for the variation of the near-field radiative heat flux when the parameter Λ is changed. Moreover, the effect of the lateral displacement of the films on the near-field radiative heat flux is also studied. The results indicate that the near-field radiative heat flux will achieve the maximum value when the peaks of the sinusoidal gratings are aligned. This work will be valuable to research on contactless thermal management in nanoscale. [ABSTRACT FROM AUTHOR]

• hBN-based thermal regulation by adjusting its shift frequency is investigated. • Adjustable hyperbolic modes can couple and decouple with surface polaritons. • Regulation ratios reach 159.6 for hBN plates, and > 2 for SiC/hBN and G/hBN plates. Nanoscale thermal regulation plays a vital role in many applications, especially in highly-integrated electronics. In this study, we theoretically analyze the near-field radiation heat transfer within hBN-based planar systems, including bare hBN plates, SiC/hBN plates, graphene/hBN plates and Au/hBN plates. We predict that tailoring the shift frequency of phonon could alter the hyperbolic modes (HMs) of hBN, thus allowing for the coupling and decoupling of HMs with SPhPs of SiC and GSPPs of graphene. Therefore, the radiative heat flux in hBN-based systems except for Au/hBN plates can be greatly regulated, and the regulation ratio can reach 159.6 for bare hBN plates, and above 2 for SiC/hBN plates and for graphene/hBN plates. Results may facilitate understanding of the principles of hBN-based evanescent wave coupling and nanoscale thermal management. [ABSTRACT FROM AUTHOR]

The dynamics of continuous systems that exhibit circular or spherical symmetry like drops, bubbles or some macromolecules, under the influence of some external excitation, develop surface patters that are hard to predict in most practical situations. In the particular case of acoustically driven microbubbles (ultrasound contrast agent), the study of the behavior of the bubble shell requires complex modeling even for describe the most simple oscillation patterns. Furthermore, due to the smallness of the spatio-temporal scale of the problem, an experimental approach requires expensive hardware setup. Despite the complexity of the particular physical problem, the basic dynamical features of some continuous physical systems can be captured by simple models of coupled oscillators. In this work we consider an analogy between a shelled-gas bubble cavitating under the action of an acoustic field and a discrete mechanical system. Thus, we present a theoretical and experimental study of the spatial instabilities of a circular ring of coupled pendulums parametrically driven by a vertical harmonic force. The system is capable of wave propagation and exhibit nonlinearities and dispersion, so manifest rich dynamics: normal oscillation modes (breathing, dipole, quadrupole...) and localized patterns of different types (breathers and kinks) witch are predicted by finite-differences numerical solutions and observed experimentally. On the basis of this analogy, the oscillation patterns and localized modes observed experimentally in acoustically driven bubbles are interpreted and discussed.

Near-field thermophotovoltaics (NFTPV) is of great interest because it can achieve both high power density and high efficiency at medium to high temperature. One key to efficient photovoltaic conversion is an emitter that can selectively emit spectrum. Indium tin oxide (ITO) is considered as the emitter for NFTPV because its plasma frequency is tunable by simple technical means. However, as a typical degenerate semiconductor, the temperature dependence of its dielectric constant is often neglected in studying the performance of NFTPV. Therefore, we propose a NFTPV model considering the temperature-dependent property of ITO. By changing the applied voltage V, the vacuum gap d , and the emitter temperature T 1 , the performance of NFTPV with and without temperature dependence is compared and shows a significant difference. We find that the heat flux is always underestimated as well as the optimal efficiency is overestimated when the temperature dependence is not considered. At d = 10 nm and T 1 = 1000 K, the optimal efficiency is even overestimated by about 270%. Without considering the temperature dependence, the output power is overestimated at d < 20 nm, while the opposite is true at d ≥ 20 nm. We clarify the main reasons for these misjudgments at a small gap originate from the underestimation of the intensity of surface phonon polaritons (SPhPs) below the bandgap and the overestimation of the intensity of surface plasmon polaritons (SPPs) above the bandgap. The main factor affecting the two kinds of surface modes in near-field regime is that high temperatures lead to low electromagnetic local density of states (LDOS) for ITO emitter near the SPPs resonant frequency, but high LDOS in the ultralow frequencies. In a larger gap, it is attributed to the underestimation of the waveguide modes above the bandgap and the nearly-full-band propagation modes. Our work illustrates the necessity of considering temperature dependence, enriches the understanding of NFTPV, and facilitates the development of related applications. [ABSTRACT FROM AUTHOR]

• We derive the formula for radiative heat flux between dipole particles and a multilayer composed of the uniaxial medium. • The multilayered surface modes can be coupled to the particle resonance, enhancing heat flux between the particle and slab. • The phase change feature of VO2 allows the active control of the heat flux by changing the slab's temperature. • We address the role of multilayer parameters on the modulation effect. • We demonstrate that the multilayered structure can also actively tune the heat flux between the nanoparticles array and slab. We derive the formula for the near-field radiative heat flux between dipole particles and a multilayered slab composed of the uniaxial medium. Based on that, the multilayered structure consisting of SiC and VO 2 materials is applied to actively modulate the radiative heat transfer between nanoparticles and slab. Utilizing the modulation feature of the multilayer, surface modes from the multilayer can be strongly coupled to the particle resonance, greatly enhancing the heat flux between the particle and slab. The phase change feature of VO 2 allows the active control of multilayered surface modes by changing the slab's temperature, greatly tuning the heat flux. We address the role of multilayer parameters on the modulation effect. We also demonstrate that the multilayered structure can also actively tune the heat flux between the nanoparticle array and slab. [ABSTRACT FROM AUTHOR]

We present a theoretical study of the surface magnon-polaritons at an interface formed by vacuum and a gyromagnetic medium (that can be either ferromagnetic or antiferromagnetic), when there is a graphene layer deposited between the media at the interface and a magnetic field is applied perpendicular to the interface. The retarded-mode dispersion relations are calculated by considering a superposition of transverse magnetic and transversal electric electromagnetic waves in both media. Our results reveal the appearance of the surface magnon-polariton modes (with frequencies typically of a few GHz) that do not exist in the absence of graphene at the interface. Also, a typical magnon-polariton dispersion relation with damping is revealed, including a resonant frequency that depends on the applied magnetic field. The effects of varying the doping levels, which modify the Fermi energies in the graphene, and varying the perpendicular applied magnetic field are presented, revealing a strong influence exerted by the presence of graphene on the surface magnon-polariton modes. Other effects include the control of the slope of the dispersion curves (with respect to the in-plane wave vector) for the modes as the Fermi energies of the graphene sheet are changed and the distinctive localization properties for the emerging surface modes., (© 2023 IOP Publishing Ltd.)

The TM surface mode propagation properties in a taper slab waveguide with an anisotropic metamaterial core and common material claddings are investigated. Through Maxwell's equations, the dispersion, reflection coefficient, transmission coefficient and power loss were extracted for the TM surface modes. Then, some characteristic curves are plotted for different metal filling ratios or different frequencies. From these curves, it is found that: (1) as waveguide length L = 7.7 μm, the reflection coefficient is near 0.99; (2) the transmission coefficient c t 2 ≤ 0.1 or even c t 2 ≤ 0.05 ; (3) the power loss Δ p / p ≥ 0.98 or even Δ p / p ≥ 0.99, which means extra strong reflection or extra big energy loss can exist in the taper waveguide. These new properties for TM surface modes propagation will benefit us to design extra strong reflectors or novel absorbers in the future. [ABSTRACT FROM AUTHOR]

It is numerically shown that surface modes of two-dimensional phononic crystals, which are Bloch modes bound to the interface between the phononic crystal and the surrounding host, can couple back and forth between the surfaces in a length scale determined by the separation of two surfaces and frequency. Supercell band structure computations through the finite-element method reveal that the surface band of an isolated surface splits into two bands which support either symmetric or antisymmetric hybrid modes. When the surface separation is 3.5 times the lattice constant, a coupling length varying between 30 and 48 periods can be obtained which first increases linearly with frequency and, then, decreases rapidly. In the linear regime, variation of coupling length can be used as a means of measuring speeds of objects on the order of 0.1 m/s by incorporating the Doppler shift. Speed sensitivity can be improved by increasing surface separation at the cost of larger device sizes. [ABSTRACT FROM AUTHOR]

The propagation constant in terms of β / k with function of normalized frequency ( V ) for grounded slab metamaterial waveguides of TE and TM mode is calculated and its graphical results is shown with the help of MATLAB. These results are compared with the three layer metamaterial waveguide structure. The evanescent fields are investigated for various modes in a perfectly grounded metamaterial planer slab waveguide for both cases. The power distribution inside the cover and film region is investigated and distribution of energy flux along the transverse profile of waveguide for different normalized frequency ( V ) is shown properly. Metamaterials show the unusual properties over normal material and due to the grounded slab structure, the evanescent fields are propagated more inside the cover region. This analysis can be useful to enhance the sensitivity of metamaterial optical waveguide sensor. [ABSTRACT FROM AUTHOR]

The dispersion behavior, localization and total energy flow of transverse magnetic surface modes supported at the interface of air and a semi-infinite one dimensional plasma photonic crystals truncated with varying cap layer is analyzed by transfer matrix method. It is observed that properties of surface modes highly depend upon parallel wave vector, thickness of cap layer and plasma frequency. By altering thickness of cap layer from lower to higher values, all of the surface modes shift towards lower band edge, and vice versa. Also, it is found that localization of transverse magnetic surface modes are controlled by plasma frequency, parallel wave vector and thickness of cap layer. [ABSTRACT FROM AUTHOR]

To excite surface modes of photonic crystal for both transverse-electric (TE) and transverse-magnetic (TM) polarizations, we put forward a honeymoon lattice of plasmonic photonic crystal composed of dielectric and metallic rods. We investigate the band dispersions of the photonic crystal by finite element method (FEM) and supercell method. The surface modes for both TE and TM polarizations can be simultaneously excited on the zigzag edge. The surface modes on the metallic edge have near-zero group velocity. By introducing the surface defect into the zigzag metallic edge, the surface modes on the edge can be tuned and have negative group velocity. [ABSTRACT FROM AUTHOR]

We have investigated the existence of surface modes at negative index material (NIM) film for the S-polarized. Our attention is mainly focused in the excitation of surface modes through numerical simulation technique of attenuated total reflection (ATR) and the manner in which the electric field is coupled into the film interfaces at NIM. In the case of the ATR show well defined minima originated by the coupling of the incident light with the symmetric and asymmetric modes. Frequencies at the minima are used to obtain the optical dispersion relations (ODR) as function of the filling factor in the unit cell (vacuum – LHM or LHM –vacuum – LHM). The ODR indicates the behavior of surface modes as the film thickness of the NIM is varied. [ABSTRACT FROM AUTHOR]

The propagation loss of a fiber can be increased by coupling core mode and surface mode which will deteriorate the performance of photonic bandgap fiber (PBGF). In this paper, we presented an aircore PBGF for gas sensing applications. By designing Λ = 2.63 µm, d = 0.95 Λ, and R= 1.13 Λ, where Λ is the distance between the adjacent air holes, the fiber was single-mode, no surface mode was supported with fiber, and more than 90% of the optical power was confined in the core. Furthermore, with optimizing the fiber structural parameters, at wavelength of λ = 1.55 µm that is in acetylene gas absorption line, significant relative sensitivity of 92.5%, and acceptable confinement loss of 0.09 dB/m, were simultaneously achieved. [ABSTRACT FROM AUTHOR]

In this work, we propose a two-dimensional photonic crystal-photonic crystal heterostructure that possesses the requirements for exciting an electromagnetic interface mode and investigate its interaction with photonic crystal waveguide modes. To study the interaction and coupling of both types of modes, the proper conditions to excite them are analyzed. Photonic crystal guided modes can appear in nearly any band gap when the photonic crystal has a line of defects within its lattice. Photonic crystal-photonic crystal surface modes can be excited at the junction of two different photonic crystals that share translation symmetry along the interface direction and have overlapped frequency band gaps. When this condition is met, dispersion relations of photonic crystal-photonic crystal surface modes will lie in the common region of both band gaps. Once the proper conditions are provided to excite these two modes, an interaction between them is possible. In the resulting calculations, a symmetric supercell and a plane wave basis are defined to numerically solve the wave equation. [ABSTRACT FROM AUTHOR]

The efficient and reliable computation of guided modes in photonic crystal wave-guides is of great importance for designing optical devices. Transparent boundary conditions based on Dirichlet-to-Neumann operators allow for an exact computation of well-confined modes and modes close to the band edge in the sense that no modelling error is introduced. The well-known super-cell method, on the other hand, introduces a modelling error which may become prohibitively large for guided modes that are not well-confined. The Dirichlet-to-Neumann transparent boundary conditions are, however, not applicable for all frequencies as they are not uniquely defined and their computation is unstable for a countable set of frequencies that correspond to so called Dirichlet eigenvalues. In this work we describe how to overcome this theoretical difficulty introducing Robin-to-Robin transparent boundary conditions whose construction do not exhibit those forbidden frequencies. They seem, hence, well suited for an exact and reliable computation of guided modes in photonic crystal wave-guides. [ABSTRACT FROM AUTHOR]

Abstract: The structural dispersion characteristics of guided surface modes in a hollow slab waveguide with a left-handed material substrate or cover are investigated. Dispersion relation is derived by using normalized parameters, and universal dispersion curves have been obtained analytically, by solving transcendental dispersion equations in a reverse way. Existence condition, mode degeneracy and other dispersion properties of guided surface modes have been discussed for different ɛ or μ of three layers for this substrate or cover layer. [Copyright &y& Elsevier]

Abstract: A hybrid metal–organic–photonic crystal (PC), a gold film with a SU8 film on its top followed by a three-dimensional (3D) PC, was designed to exercise additional control upon the photon behaviors. Attenuated total reflection measurements demonstrate that the 3D PC plays a crucial role in the formation of significant optical properties of the metal-based hybrid and the reflectivity minimum in its reflectivity curve is, mostly, a result of synergetic action of the coupling of surface plasmon polaritons to surface modes and additional guided modes yielded in the resonant cavity composed of the gold film and the PC. [Copyright &y& Elsevier]

We explain how a surface optical vortex can be created when a Bessel beam is totally reflected internally at the planar surface of a dielectric on which a metallic sheet has been deposited. A two-dimensional patterning on the surface, the strongly localized intensity distribution decays with distance vertical to the surface. The characteristics of this surface optical vortex depend on the incident beam parameters and the dielectric mismatch of the media. [ABSTRACT FROM AUTHOR]

The problem of guided mode reflection from an abruptly terminated planar metamaterial waveguide is studied by the variational technique. The theory is illustrated by examples of abruptly terminated three-layer waveguides with step permittivity and permeability profiles. Differences in the scattering characteristics for systems with metamaterials and usual media are discussed. [ABSTRACT FROM AUTHOR]

Abstract: We present an exact calculation of coherent thermal conductance in 1-D multilayer photonic crystals using the S-matrix method. In particular, we study the thermal conductance in a bilayer structure of Si/vacuum or Al2O3/vacuum slabs by means of the exact radiative heat flux expression. Based on the results obtained for the Al2O3/vacuum structure we show by comparison with previous works that the material losses and (localized) surface modes supported by the inner layers play a fundamental role and cannot be omitted in the definition of thermal conductance. Our results could have significant implications in the conception of efficient thermal barriers. [Copyright &y& Elsevier]

Abstract: We study the electromagnetic surface wave localizing, the so-called surface Tamm states, at an interface separating a left-handed metamaterial (LHM) and a semi-infinite one-dimensional photonic crystal made of alternative left-handed metamaterial and right-handed materials. We show that the existence of metamaterial causes the Tamm states with backward energy flow and allows flexible control of dispersion properties of the surface modes. We study the effect of the physical parameters of the photonic crystal on the dispersion properties and the group velocity of the Tamm states. We also study dispersion properties of the Tamm states in higher order photonic band gaps of the photonic crystal and compare our results with the case when the LHM medium is replaced by a right-handed material (RHM). [Copyright &y& Elsevier]

Abstract: Spectroscopic investigations of individual single-crystalline GaN nanowires with a lateral dimensions of ∼30–90nm were performed using the spatially resolved technique of electron energy-loss spectroscopy in conjunction with scanning transmission electron microscope showing a 2-Å electron probe. Positioning the electron probe upon transmission impact and at aloof setup with respect to the nanomaterials, we explored two types of surface modes intrinsic to GaN, surface exciton polaritons at ∼8.3eV (∼150nm) and surface guided modes at 3.88eV (∼320nm), which are in visible/ultra-violet spectral regime above GaN bandgap of ∼3.3eV (∼375nm) and difficult to access by conventional optical spectroscopies. The explorations of these electromagnetic resonances might expand the current technical interests in GaN nanomaterials from the visible/UV range below ∼3.5eV to the spectral regime further beyond. [ABSTRACT FROM AUTHOR]

Abstract: Newly discovered metamaterials have opened new vistas for better control of light via negative refraction, whereby light refracts in the “wrong” manner. These are dielectric and metallic composite materials structured at subwavelength lengthscales. Their building blocks consist of local resonators such as conducting thin bars and split rings driving the material parameters such as the dielectric permittivity and magnetic permeability to negative (complex) values. Combined together, these structural elements can bring about a (complex valued) negative effective refractive index for the Snell–Descartes law and result in negative refraction of radiation. Negative refractive index materials can support a host of surface plasmon states for both polarizations of light. This makes possible unique effects such as imaging with subwavelength image resolution through the Pendry–Veselago slab lens. Other geometries have also been investigated, such as cylindrical or spherical lenses that enable a magnification of images with subwavelength resolution. Superlenses of three-fold (equilateral triangle), four-fold (square) and six-fold (hexagonal) geometry allow for multiple images, respectively two, three, and five. Generalization to rectangular and triangular checkerboards consisting of alternating cells of positive and negative refractive index represents a very singular situation in which the density of modes diverges at the corners, with an infinity of images. Sine-cosecant anisotropic heterogeneous square and triangular checkerboards can be respectively mapped onto three-dimensional cubic and icosahedral corner lenses consisting of alternating positive and negative refractive regions. All such systems with corners between negative and positive refractive media display very singular behavior with the local density of states becoming infinitely large at the corner, in the limit of no dissipation. We investigate all of these, using the unifying viewpoint of transformation optics. To cite this article: S. Guenneau, S.A. Ramakrishna, C. R. Physique 10 (2009). [Copyright &y& Elsevier]