Optical medium

Abstract: This paper deals with electromagnetic wave propagation through dielectric media whose propagation constants vary as a function of time. If the parameters of the medium cannot respond to changes in the electric and magnetic fields of the propagating wave, the fields within such media will be linear. Maxwell's equations are solved for cases in which the scalar permittivity and permeability vary independently with time. When the impedance is constant, an exact solution is obtained. When the impedance varies, a closed form approximation is found since an exact solution is not always possible. The field energy and electromagnetic momentum are derived for a velocity transient and it is seen that, in general, the energy changes and the momentum remains constant. The frequency deviation that results when a monochromatic wave is passed through a section of dielectric with nonconstant velocity of propagation is discussed in detail. An approximate solution is obtained for the case in which the electrical length of such a section is small; it is found that essentially linear phase modulation occurs. The general solution is found for the case in wtilch the electrical length of section is long and the permittivity of the medium sinusoidally modulated. The optimum length found to give the greatest frequency deviation is shown to be generally impracticable. It appears that ferroelectric or ferrimagnetic velocity-modulated dielectrics are feasible, at least for low-power modulators.

Abstract: In most wave phenomena, the interplay between the spatial and temporal features of a wave is influenced by the medium in which the wave propagates. For example, the wavelength λ (a spatial feature) and the frequency f (a temporal feature) of a propagating signal are related via the phase velocity v of the wave in the medium as v = f λ. For electromagnetic waves such as radio, microwave, and optical waves, the phase velocity is determined by the medium's electromagnetic parameters of permittivity e and permeability µ, which is then given as √eμ. When a wave interacts with a structure embedded in a host medium, both these temporal and spatial features play key roles in determining the scattering response of the structure. The recent development of a class of metamaterials in which the electric (e) and magnetic (µ) properties can be tuned by design is providing a platform to engineer optical devices with unconventional properties.

Abstract: Aspects of the subject disclosure may include, for example, an apparatus including a waveguide, an antenna, and a transmitter. The transmitter can facilitate transmission of first electromagnetic waves via the antenna, the first electromagnetic waves having a fundamental mode. The waveguide can facilitate propagation of the first electromagnetic waves at least in part on a surface of the waveguide. The waveguide can be positioned at a location that enables the first electromagnetic waves to induce second electromagnetic waves having fundamental and non-fundamental modes that propagate on a surface of a transmission medium. Other embodiments are disclosed.

Abstract: Super-resolution imaging beyond Abbe’s diffraction limit can be achieved by utilizing an optical medium or “metamaterial” that can either amplify or transport the decaying near-field evanescent waves that carry subwavelength features of objects. Earlier approaches at optical frequencies mostly utilized the amplification of evanescent waves in thin metallic films or metal-dielectric multilayers, but were restricted to very small thicknesses (⪡λ, wavelength) and accordingly short object-image distances, due to losses in the material. Here, we present an experimental demonstration of super-resolution imaging by a low-loss three-dimensional metamaterial nanolens consisting of aligned gold nanowires embedded in a porous alumina matrix. This composite medium possesses strongly anisotropic optical properties with negative permittivity in the nanowire axis direction, which enables the transport of both far-field and near-field components with low-loss over significant distances (>6λ), and over a broad spectral range. We demonstrate the imaging of large objects, having subwavelength features, with a resolution of at least λ/4 at near-infrared wavelengths. The results are in good agreement with a theoretical model of wave propagation in anisotropic media.