Wavefront and group velocity in relaxing and bubbly fluids

1999 ◽  
Vol 105 (6) ◽  
pp. 3044-3048 ◽  
Author(s):  
Johan L. Leander
Keyword(s):  
Group Velocity ◽  
Bubbly Fluids

Interferometric (Fourier-Spectroscopic) Measurement of Electron Energy Distributions

1990 ◽  
Vol 48 (2) ◽  
pp. 110-111 ◽  
Author(s):  
F. Hasselbach ◽  
A. Schäfer
Keyword(s):  
Group Velocity ◽  
Wave Packets ◽  
Index Of Refraction ◽  
Electron Wave ◽  
Fringe Contrast ◽  
Faraday Cage ◽  
Optical Index ◽  
Wien Filter ◽  
Coherent Wave ◽  
Electric And Magnetic Fields

Möllenstedt and Wohland proposed in 1980 two methods for measuring the coherence lengths of electron wave packets interferometrically by observing interference fringe contrast in dependence on the longitudinal shift of the wave packets. In both cases an electron beam is split by an electron optical biprism into two coherent wave packets, and subsequently both packets travel part of their way to the interference plane in regions of different electric potential, either in a Faraday cage (Fig. 1a) or in a Wien filter (crossed electric and magnetic fields, Fig. 1b). In the Faraday cage the phase and group velocity of the upper beam (Fig.1a) is retarded or accelerated according to the cage potential. In the Wien filter the group velocity of both beams varies with its excitation while the phase velocity remains unchanged. The phase of the electron wave is not affected at all in the compensated state of the Wien filter since the electron optical index of refraction in this state equals 1 inside and outside of the Wien filter.

The four-dimensional group velocity

1978 ◽  
Vol 125 (7) ◽  
pp. 549-565 ◽  
Author(s):  
V.G. Polevoi ◽  
S.M. Rytov
Keyword(s):  
Group Velocity ◽  
Dimensional Group

ESTIMATION OF THOMSEN'S EPSILON AND DELTA IN A SINGLE CORE USING ULTRASONIC PHASE AND GROUP VELOCITY MEASUREMENTS

2019 ◽  
Author(s):  
Gabriel Gallardo-Giozza ◽  
D. Nicolás Espinoza ◽  
Carlos Torres-Verdín ◽  
Elsa Maalouf
Keyword(s):  
Group Velocity ◽  
Velocity Measurements

Negative Group Velocity of Surface Polaritons in Metal Foil Nanostructure

2017 ◽  
Vol 9 (3) ◽  
pp. 03039-1-03039-4 ◽  
Author(s):  
Y. M. Aleksandrov ◽  
◽  
V. V. Yatsishen ◽  
Keyword(s):  
Group Velocity ◽  
Metal Foil ◽  
Negative Group ◽  
Surface Polaritons ◽  
Negative Group Velocity

scholarly journals Group Velocity Modulation and Light Field Focusing of the Edge States in Chirped Valley Graphene Plasmonic Metamaterials

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1808
Author(s):  
Liqiang Zhuo ◽  
Huiru He ◽  
Ruimin Huang ◽  
Shaojian Su ◽  
Zhili Lin ◽  
...  
Keyword(s):  
Group Velocity ◽  
Light Field ◽  
Slow Light ◽  
Dielectric Materials ◽  
Degree Of Freedom ◽  
Geometrical Parameters ◽  
Edge States ◽  
Velocity Modulation ◽  
Plasmonic Metamaterials ◽  
On Chip

The valley degree of freedom, like the spin degree of freedom in spintronics, is regarded as a new information carrier, promoting the emerging valley photonics. Although there exist topologically protected valley edge states which are immune to optical backscattering caused by defects and sharp edges at the inverse valley Hall phase interfaces composed of ordinary optical dielectric materials, the dispersion and the frequency range of the edge states cannot be tuned once the geometrical parameters of the materials are determined. In this paper, we propose a chirped valley graphene plasmonic metamaterial waveguide composed of the valley graphene plasmonic metamaterials (VGPMs) with regularly varying chemical potentials while keeping the geometrical parameters constant. Due to the excellent tunability of graphene, the proposed waveguide supports group velocity modulation and zero group velocity of the edge states, where the light field of different frequencies focuses at different specific locations. The proposed structures may find significant applications in the fields of slow light, micro–nano-optics, topological plasmonics, and on-chip light manipulation.

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