Design of Metamaterial Surfaces with Broad-band Absorbance

A simple design paradigm for making broad-band ultra-thin plasmonic absorbers is introduced. The absorber's unit cell is composed of sub-units of various sizes, resulting in nearly 100% absorbance at multiple adjacent frequencies and high absorbance over a broad frequency range. A simple theoretical model for designing broad-band absorbers is presented. It uses a single-resonance model to describe the optical response of each sub-unit and employs the series circuit model to predict the overall response. Validity of the circuit model relies on short propagation lengths of the surface plasmons

Perfect absorption and giant magnification with a thin metamaterial layer

It is shown that perfect absorption and giant amplification can be realized when a wave impinges on a special metamaterial layer with zero real parts of the permittivity and permeability. The imaginary parts of the permittivity and permeability remain nonzero, corresponding to finite loss or gain. Perfect absorption and giant magnification can still be achieved even if the thickness of the metamaterial layer is arbitrarily thin and the absolute imaginary parts of the permittivity and permeability are very small. The metamaterial layer needs a total-reflection substrate for perfect absorption, while this is not required for giant magnification.Comment: 15 pages, 4 figure

A terahertz polarization insensitive dual band metamaterial absorber

Metamaterial absorbers have attracted considerable attention for applications in the terahertz range. In this Letter, we report the design, fabrication, and characterization of a terahertz dual band metamaterial absorber that shows two distinct absorption peaks with high absorption. By manipulating the periodic patterned structures as well as the dielectric layer thickness of the metal–dielectric–metal structure, significantly high absorption can be obtained at specific resonance frequencies. Finite-difference time-domain modeling is used to design the structure of the absorber. The fabricated devices have been characterized using a Fourier transform IR spectrometer. The experimental results show two distinct absorption peaks at 2.7 and 5.2 THz, which are in good agreement with the simulation. The absorption magnitudes at 2.7 and 5.2 THz are 0.68 and 0.74, respectively

A Simple Separable Exact C*-Algebra not Anti-isomorphic to Itself

We give an example of an exact, stably finite, simple. separable C*-algebra D which is not isomorphic to its opposite algebra. Moreover, D has the following additional properties. It is stably finite, approximately divisible, has real rank zero and stable rank one, has a unique tracial state, and the order on projections over D is determined by traces. It also absorbs the Jiang-Su algebra Z, and in fact absorbs the 3^{\infty} UHF algebra. We can also explicitly compute the K-theory of D, namely K_0 (D) = Z[1/3] with the standard order, and K_1 (D) = 0, as well as the Cuntz semigroup of D.Comment: 16 pages; AMSLaTeX. The material on other possible K-groups for such an algebra has been moved to a separate paper (1309.4142 [math.OA]

Magnetized Plasma-Filled Waveguide: A New High-Gradient Accelerating Structure

Electromagnetic waves confined between the metal plates of a plasma-filled waveguide are investigated. It is demonstrated that when the plasma is magnetized along the metallic plates., there exists a luminous accelerating wave propagating with a very slow group velocity. It is shown that the magnetized plasma >isolates> the metal wall from the transverse electric field, thereby reducing potential breakdown problems. Applications of the metallic plasma-filled waveguide to particle accelerations and microwave pulse manipulation are described.Physic

Reaching the nonlinear regime of Raman amplification of ultrashort laser pulses

The intensity of a subpicosecond laser pulse was amplified by a factor of up to 1000 using the Raman backscatter interaction in a 2 mm long gas jet plasma. The process of Raman amplification reached the nonlinear regime, with the intensity of the amplified pulse exceeding that of the pump pulse by more than an order of magnitude. Features unique to the nonlinear regime such as gain saturation, bandwidth broadening, and pulse shortening were observed. Simulation and theory are in qualitative agreement with the measurements.open695

Ultra-broadband Light Absorption by a Sawtooth Anisotropic Metamaterial Slab

We present an ultra broadband thin-film infrared absorber made of saw-toothed anisotropic metamaterial. Absorbtivity of higher than 95% at normal incidence is supported in a wide range of frequencies, where the full absorption width at half maximum is about 86%. Such property is retained well at a very wide range of incident angles too. Light of shorter wavelengths are harvested at upper parts of the sawteeth of smaller widths, while light of longer wavelengths are trapped at lower parts of larger tooth widths. This phenomenon is explained by the slowlight modes in anisotropic metamaterial waveguide. Our study can be applied in the field of designing photovoltaic devices and thermal emitters.Comment: 12 pages, 4 picture

Past Achievements and Future Challenges in 3D Photonic Metamaterials

Photonic metamaterials are man-made structures composed of tailored micro- or nanostructured metallo-dielectric sub-wavelength building blocks that are densely packed into an effective material. This deceptively simple, yet powerful, truly revolutionary concept allows for achieving novel, unusual, and sometimes even unheard-of optical properties, such as magnetism at optical frequencies, negative refractive indices, large positive refractive indices, zero reflection via impedance matching, perfect absorption, giant circular dichroism, or enhanced nonlinear optical properties. Possible applications of metamaterials comprise ultrahigh-resolution imaging systems, compact polarization optics, and cloaking devices. This review describes the experimental progress recently made fabricating three-dimensional metamaterial structures and discusses some remaining future challenges

Wide-angle infrared absorber based on negative index plasmonic metamaterial

A metamaterials-based approach to making a wide-angle absorber of infrared radiation is described. The technique is based on an anisotropic Perfectly Impedance Matched Negative Index Material (PIMNIM). It is shown analytically that a sub-wavelength in all three dimensions PIMNIM enables absorption of close to 100% for incidence angles up to $45\deg$ to the normal. A specific implementation of such frequency-tunable PIMNIM based on plasmonic metamaterials is presented. Applications to infrared imaging and coherent thermal sources are described.Comment: To be published in Phys. Rev.

Interference theory of metamaterial perfect absorbers

The impedance matching in metamaterial perfect absorbers has been believed to involve and rely on magnetic resonant response, with a direct evidence from the anti-parallel directions of surface currents in the metal structures. Here we present a different theoretical interpretation based on interferences, which shows that the two layers of metal structure in metamaterial absorbers are linked only by multiple reflections with negligible near-field interactions or magnetic resonances. This is further supported by the out-of-phase surface currents derived at the interfaces of resonator array and ground plane through multiple reflections and superpositions. The theory developed here explains all features observed in narrowband metamaterial absorbers and therefore provides a profound understanding of the underlying physics.Comment: 8 pages, 4 figures, submitted to Optics Expres