Impossibility of negative group velocities in a periodic layer structure with or without loss

2005 ◽  
Vol 250 (4-6) ◽  
pp. 258-265 ◽  
Author(s):  
Louis Poirier ◽  
Robert I. Thompson ◽  
Alain Haché
Keyword(s):  
Layer Structure ◽  
Negative Group ◽  
Periodic Layer ◽  
Group Velocities

X-Ray Reflectivity Studies of Pt/AlN Multilayered Films

2007 ◽  
Vol 561-565 ◽  
pp. 2095-2098
Author(s):  
Takashi Harumoto ◽  
Ji Shi ◽  
Yoshio Nakamura
Keyword(s):  
Layer Structure ◽  
Bragg Reflection ◽  
X Ray Diffraction ◽  
Multilayered Films ◽  
Sputtering Deposition ◽  
X Ray ◽  
First Order ◽  
Periodic Layer ◽  
Deposited Films ◽  
Very High

Pt/AlN multilayered films fabricated by alternative sputtering deposition were characterized by X-Ray Reflectometry and X-Ray Diffraction. As-deposited films have (111) and (001) preferred orientation for Pt and AlN, respectively. The X-Ray Reflectivity profiles are assigned to the total reflection and Bragg reflections due to periodic layer structure. The Bragg peaks are observed at the 2Theta range beyond 15 degree and the peak intensities increase after annealing. The reflectivity of the first order Bragg reflection is approximately 65% and is stable after annealing at 873K. Simulation of the reflectivity profile has shown roughnesses of the Pt/AlN interfaces are below 0.4nm. X-Ray Diffraction revealed the development of film texture and formation of superlattice by annealing. The latter indicates periodicity of film is very high.

Negative Group Velocities in Continuous Structures

1957 ◽  
Vol 24 (4) ◽  
pp. 622-623
Author(s):  
S. H. Crandall
Keyword(s):  
Negative Group ◽  
Group Velocities

Quasi-periodic layer structure of die-upset NdFeB magnets

2013 ◽  
Vol 31 (7) ◽  
pp. 679-684 ◽  
Author(s):  
Bin LAI ◽  
Yanfeng LI ◽  
Huijie WANG ◽  
Anhua LI ◽  
Minggang ZHU ◽  
...  
Keyword(s):  
Layer Structure ◽  
Ndfeb Magnets ◽  
Periodic Layer

scholarly journals Pulsed light beams in vacuum with superluminal and negative group velocities

2003 ◽  
Vol 67 (6) ◽  
Author(s):  
Miguel A. Porras ◽  
Isabel Gonzalo ◽  
Alessia Mondello
Keyword(s):  
Negative Group ◽  
Pulsed Light ◽  
Light Beams ◽  
Group Velocities

NEGATIVE REFRACTION IN A ONE-DIMENSIONAL BIAXIALLY ANISOTROPIC CHIRAL PHOTONIC CRYSTAL

2010 ◽  
Vol 24 (11) ◽  
pp. 1079-1090 ◽  
Author(s):  
YUAN YOU
Keyword(s):  
Photonic Crystal ◽  
Significant Influence ◽  
Negative Refraction ◽  
Dielectric Material ◽  
Negative Group ◽  
One Dimensional ◽  
Polarized Waves ◽  
Potential Applications ◽  
Electromagnetic Transport ◽  
Group Velocities

In the transfer matrix framework of electromagnetic transport, we calculate the group velocities in a one-dimensional photonic crystal composed of a biaxially anisotropic chiral material and dielectric material. According to the isofrequency curves, it is unravelled that two polarized waves possess negative group velocities. As a result, negative refraction can be achieved in the present configuration. In addition, the chirality has a significant influence on the group velocities in the biaxially anisotropic chiral photonic crystal, which even causes the group velocities to change from positive to negative. Our investigations may have potential applications in the chiral-based negative refraction devices.

Subwavelength Terahertz Waveguide Using Negative Permeability Metamaterial

2009 ◽  
Vol 1182 ◽  
Author(s):  
Atsushi Ishikawa ◽  
Shuang Zhang ◽  
Dentcho A Genov ◽  
Guy Bartal ◽  
Xiang Zhang
Keyword(s):  
Optical Constants ◽  
Propagation Loss ◽  
Negative Permeability ◽  
Narrow Gap ◽  
Negative Group ◽  
Guided Mode ◽  
Core Width ◽  
Terahertz Waveguide ◽  
Device Applications ◽  
Group Velocities

AbstractWe propose a novel subwavelength terahertz (THz) waveguide using the magnetic plasmon polariton (MPP) mode guided by a narrow gap in a negative permeability metamaterial. Deep subwavelength wave-guiding (< λ/10) with a modest propagation loss (2.5 dB/λ) and group velocities down to c/21.8 is demonstrated in a straight waveguide, a 90-degree bend, and a splitter. The distinctive dispersions of the guided mode with positive and negative group velocities are explained analytically by considering the dispersive effective optical constants of the metamaterial. The proposed waveguiding system inherently has no cutoff for any core width and height, paving the way toward the deep subwavelength transport of THz waves for integrated THz device applications.

Electromagnetically-induced transparency, slow light, and negative group velocities in a room temperature vapor of 4He∗

2009 ◽  
Vol 10 (10) ◽  
pp. 919-926 ◽  
Author(s):  
F. Goldfarb ◽  
T. Lauprêtre ◽  
J. Ruggiero ◽  
F. Bretenaker ◽  
J. Ghosh ◽  
...  
Keyword(s):  
Room Temperature ◽  
Slow Light ◽  
Electromagnetically Induced Transparency ◽  
Negative Group ◽  
Induced Transparency ◽  
Group Velocities
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