Search results for "plane wave"
showing 10 items of 67 documents
Control of Space-Time Trajectories of Noise-Driven Optical Extreme Events in Metamaterial Waveguides
2019
Metamaterials offer the potential to precisely manipulate electromagnetic wave propagation in ways that cannot be achieved with materials found in nature. The formation and propagation of optical spatial solitons in metamaterials has been already investigated [1]. Here we report the theoretical and numerical investigations on temporal-spectral dynamics of nonlinear extreme events arising from the initial noise-perturbed plane wave in metamaterial waveguides. A typical waveguide structure used here is a planar structure with a metamaterial core and a part of the structure, in the form of the substrate, is replaced with a magnetooptic material. We assume that the core material is isotropic an…
Small Angular Scale Simulations of the Microwave Sky
1996
We describe and compare two types of microwave sky simulations which are good for small angular scales. The first type uses expansions in spherical harmonics, and the second one is based on plane waves and the Fast Fourier Transform. The angular power spectrum is extracted from maps corresponding to both types of simulations, and the resulting spectra are appropriately compared. In this way, the features and usefulness of Fourier simulations are pointed out. For $\ell \geq 100$, all the simulations lead to similar accuracies; however, the CPU cost of Fourier simulations is $\sim 10$ times smaller than that for spherical harmonic simulations. For $\ell \leq 100$, the simulations based on sph…
Rigorous analysis of three-dimensional beam transmission through a dielectric slab
1997
The plane-wave-spectrum technique is applied to study the transmission of a three-dimensional beam through a dielectric slab. The electromagnetic beam radiated from an aperture antenna is represented by an angular spectrum of plane waves. The use of three different co-ordinate systems using rectangular co-ordinates allows a rigorous formulation to be obtained. The near field transmitted through a dielectric slab is obtained and compared with measurements.
Electronic structure of triangular, hexagonal and round graphene flakes near the Fermi level
2008
The electronic shell structure of triangular, hexagonal and round graphene quantum dots (flakes) near the Fermi level has been studied using a tight-binding method. The results show that close to the Fermi level the shell structure of a triangular flake is that of free massless particles, and that triangles with an armchair edge show an additional sequence of levels ("ghost states"). These levels result from the graphene band structure and the plane wave solution of the wave equation, and they are absent for triangles with an zigzag edge. All zigzag triangles exhibit a prominent edge state at the Fermi level, and few low-energy conduction electron states occur both in triangular and hexagon…
Comparison of first-principles methods to extract magnetic parameters in ultra-thin films: Co/Pt(111)
2019
We compare three distinct computational approaches based on first-principles calculations within density functional theory to explore the magnetic exchange and the Dzyaloshinskii-Moriya interactions (DMI) of a Co monolayer on Pt(111), namely, (i) the method of infinitesimal rotations of magnetic moments based on the Korringa-Kohn-Rostoker (KKR) Green function method, (ii) the generalized Bloch theorem applied to spiraling magnetic structures and (iii) supercell calculations with noncollinear magnetic moments, the latter two being based on the full-potential linearized augmented plane wave (FLAPW) method. In particular, we show that the magnetic interaction parameters entering micromagnetic …
Coupled plasmonic graphene wires: theoretical study including complex frequencies and field distributions of bright and dark surface plasmons
2020
Theoretical research on localized surface plasmons (LSPs) supported by a structure formed by two parallel dielectric wires with a circular cross section wrapped with a graphene sheet has an impact in the practical realm. Here, LSPs are represented in the form of an infinite series of cylindrical multipole partial waves linked to each of the graphene wires. To obtain the kinematics (complex eigenfrequencies) and dynamic characteristics (field distributions) of the LSPs, we consider the analytic extension to the complex plane of the solution to the boundary value problem. The lower frequency LSP group is formed by four branches, two of them corresponding to bright modes and the others to dark…
Lasing condition for trapped modes in subwavelength--wired PT--symmetric resonators
2021
The ability to control the laser modes within a subwavelength resonator is of key relevance in modern optoelectronics. This work deals with the theoretical research on optical properties of a PT-symmetric nano-scaled dimer formed by two dielectric wires, one is with loss and the other with gain, wrapped with graphene sheets. We show the existence of two non-radiating trapped modes which transform into radiating modes by increasing the gain–loss parameter. Moreover, these modes reach the lasing condition for suitable values of this parameter, a fact that makes these modes achieve an ultra high quality factor that is manifested on the response of the structure when it is excited by a plane wa…
Space-time analogy for partially coherent plane-wave-type pulses.
2005
In this Letter we extend the well-known space-time duality to partially coherent wave fields and, as a limit case, to incoherent sources. We show that there is a general analogy between the paraxial diffraction of quasi-monochromatic beams of limited spatial coherence and the temporal distortion of partially coherent plane-wave pulses in parabolic dispersive media. Next, coherence-dependent effects in the propagation of Gaussian Schell-model pulses are retrieved from that of their spatial counterpart, the Gaussian Schell-model beam. Finally, the last result allows us to present a source linewidth analysis in an optical fiber communication system operating around the 1.55 microm wavelength w…
Plasmon-driven nondiffracting surface beaming
2011
We introduce diffraction-free plasmonic waves in metal-dielectric surfaces which are the analogue to nondiffracting Bessel beams in free space. By interfering multiple converging plane waves with controlled phase matching, we generate a subwavelength transverse spot located at the boundaries of a 1D plasmonic lattice. The diffraction-free beam is resonantly transmitted through the stratiform medium leading not only to light confinement but also to wave enhancement assisted by surface plasmons polaritons. To conclude, we briefly analyze other types of localized surface modes which were proposed recently.
Modeling of photonic crystal fibers from the scalar wave equation with a purely transverse linearly polarized vector potential
2011
In this work, we propose a new technique for modeling light propagation in photonic crystal fibers where the electric field is evaluated from a purely transverse linearly polarized vector potential. The vector potential in a nonuniform dielectric obeys a wave equation coupled to the scalar potential, but it can be reduced to a scalar wave equation when the coupling term is ignored to the lowest order approximation. We show that this method gives reliable results for photonic crystal fibers when the scalar analysis is improved by a perturbational correction.