Experimental observation of wave modulation and Dirac cone in acoustic double zero refractive index metamaterials (Conference Presentation)

2017 ◽  
Author(s):  
Chengzhi Shi ◽  
Marc Dubois ◽  
Xuefeng Zhu ◽  
Yuan Wang ◽  
Xiang Zhang
Keyword(s):  
Refractive Index ◽  
Experimental Observation ◽  
Dirac Cone ◽  
Double Zero ◽  
Wave Modulation

Strong Exciton Polariton Dispersion in Multimode GaN Microcavity

2009 ◽  
Vol 1182 ◽  
Author(s):  
Mei-Chun Liu ◽  
Yuh-Jen Cheng ◽  
Shih-Hsin Hsu ◽  
Hao-Chung Kuo ◽  
Tien-Chang Lu ◽  
...  
Keyword(s):  
Refractive Index ◽  
Experimental Observation ◽  
Interaction Constant ◽  
Axial Mode ◽  
Photon Interaction ◽  
Frequency Spacing ◽  
Order Of Magnitude ◽  
Pl Spectrum

AbstractWe report the experimental observation of a very strong cavity polariton dispersion in a multi-axial mode GaN microcavity. The linewidth of photoluminescent (PL) spectrum covers a few cavity axial modes. The resonant photoluminescent peaks have a strong dispersion. The frequency spacing between adjacent peaks decreases by almost a factor of five from 470nm to 370nm. The strong dispersion can be well described by cavity polariton dispersion, but not by the dispersion of the refractive index of GaN. The measured exciton-photon interaction constant is 260 meV. It is an order of magnitude higher than the typically reported values for GaN microcavities

scholarly journals Structural, Electronic and Optical Properties of Stanene Doped Beryllium: A First Principle Study

2021 ◽  
pp. 32-40
Author(s):  
L. S. Taura ◽  
Isah Abdulmalik ◽  
A. S. Gidado ◽  
Abdullahi Lawal
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Fermi Level ◽  
Band Gap ◽  
Density Functional ◽  
Earth Metal ◽  
Dirac Cone ◽  
Electronic Band ◽  
Electronic And Optical Properties ◽  
Optical Applications

Stanene is a 2D hexagonal layer of tin with exceptional electronic and optical properties. However, the semiconductor applications of stanene are limited due to its zero band-gap. However, doping stanene could lead to a band gap opening, which could be a promising material for electronic and optical applications. In this work, optimized structure, electronic band structure, real and imaginary parts of the frequency-dependent dielectric function, electron loss function, and refractive index of stanene substitutionally doped with alkaline earth metal (beryllium) were analyzed using density functional theory (DFT) calculations as implemented in the quantum espresso and yambo suites. A pure stanene has a zero band gap energy, but with the inclusion of spin-orbit coupling in the electronic calculation of pure stanene, the band-gap is observed to open up by 0.1eV. Doping stanene with beryllium opens the band-gap and shifts the Dirac cone from the Fermi level, the band gap opens by 0.25eV, 0.55eV, and 0.8eV when the concentration of Beryllium is 12.5%, 25%, and 37.5% respectively. The Dirac cone vanished when the concentration of the dopant was increased to 50%.  The Fermi level is shifted towards the valence band edge indicating a p-type material. The material absorption shows that SnBe absorption ranges in the visible to the ultraviolet region, The refractive index in stanene doped beryllium (SnBe) was found to be higher than that of pristine stanene, the highest refractive index was 9.2 at SnBe25%. In a nutshell, the results indicate that stanene can be a good material for electronic and optical applications if doped with beryllium.

On the Modulation of Origami Phononic Structure for Adaptive Wave Transmission in Brillouin Zone

2020 ◽  
Author(s):  
Megan Hathcock ◽  
Bogdan-Ioan Popa ◽  
K. W. Wang
Keyword(s):  
Refractive Index ◽  
Band Structure ◽  
Brillouin Zone ◽  
Environmental Changes ◽  
Phononic Crystals ◽  
Wave Transmission ◽  
Geometric Constraints ◽  
Dirac Cone ◽  
Tunable Frequency ◽  
Lattice Perturbation

Abstract Recently the presence of a Dirac cone within the band structure of graphene has inspired research on phononic crystals with Dirac-like behaviors — including structures mimicking zero refractive index materials. The interesting phenomena produced by these structures occur at fixed frequencies and cannot be adaptive to needs and environmental changes. To address this constraint, researchers have designed tunable phononic structures; however, the tunable frequency ranges from the studies reported to date are limited by geometric constraints. Using a reconfigurable origami structure to modulate between different classes of phononic Bravais lattices, this research numerically investigates the effects of phononic lattice perturbation to produce drastic changes in the frequency of useful accidental degeneracies.

scholarly journals Observation of acoustic Dirac-like cone and double zero refractive index

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Marc Dubois ◽  
Chengzhi Shi ◽  
Xuefeng Zhu ◽  
Yuan Wang ◽  
Xiang Zhang
Keyword(s):  
Refractive Index ◽  
Double Zero

Dirac cone and double zero materials

2011 ◽  
Author(s):  
C. T. Chan ◽  
Xueqin Huang ◽  
Yun Lai ◽  
Zhi Hong Hang ◽  
Huihuo Zheng ◽  
...  
Keyword(s):  
Dirac Cone ◽  
Double Zero

TEM characterization of proton-exchanged LiNbO3 optical waveguides

1986 ◽  
Vol 44 ◽  
pp. 480-481
Author(s):  
W. E. Lee
Keyword(s):  
Refractive Index ◽  
Benzoic Acid ◽  
Optical Waveguides ◽  
Total Internal Reflection ◽  
Index Of Refraction ◽  
Optical Measurements ◽  
Lithium Ions ◽  
Wide Channel ◽  
Tem Characterization

An optical waveguide consists of a several-micron wide channel with a slightly different index of refraction than the host substrate; light can be trapped in the channel by total internal reflection.Optical waveguides can be formed from single-crystal LiNbO3 using the proton exhange technique. In this technique, polished specimens are masked with polycrystal1ine chromium in such a way as to leave 3-13 μm wide channels. These are held in benzoic acid at 249°C for 5 minutes allowing protons to exchange for lithium ions within the channels causing an increase in the refractive index of the channel and creating the waveguide. Unfortunately, optical measurements often reveal a loss in waveguiding ability up to several weeks after exchange.

Light microscopy of ceramics

1993 ◽  
Vol 51 ◽  
pp. 908-909
Author(s):  
Walter C. McCrone
Keyword(s):  
Refractive Index ◽  
Light Microscopy ◽  
Light Microscope ◽  
Polarized Light ◽  
Refractive Indices ◽  
Complete Coverage ◽  
The Subject ◽  
Lower Refractive Index

An excellent chapter on this subject by V.D. Fréchette appeared in a book edited by L.L. Hench and R.W. Gould in 1971 (1). That chapter with the references cited there provides a very complete coverage of the subject. I will add a more complete coverage of an important polarized light microscope (PLM) technique developed more recently (2). Dispersion staining is based on refractive index and its variation with wavelength (dispersion of index). A particle of, say almandite, a garnet, has refractive indices of nF = 1.789 nm, nD = 1.780 nm and nC = 1.775 nm. A Cargille refractive index liquid having nD = 1.780 nm will have nF = 1.810 and nC = 1.768 nm. Almandite grains will disappear in that liquid when observed with a beam of 589 nm light (D-line), but it will have a lower refractive index than that liquid with 486 nm light (F-line), and a higher index than that liquid with 656 nm light (C-line).

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