DOI: 10.1117/1.JNP.10.012513
WoS: WOS:000374239400013
Résumé:

Semiconducting carbon nanotubes are an emerging material for photonics. We report on the enhancement of semiconducting carbon nanotubes photoluminescence with silicon microring resonators. Polyfluorene extracted semiconducting carbon nanotubes, deposited on such resonators, display sharp emission peaks superposed to nanotube emission, which is attributed to the interaction with the cavity modes of the microring resonators. Ring resonators with radii of 5 and 10  μm were used, to demonstrate the tuning of the spectral distance between two successive emission resonances. Quality factors ranged between 3000 and 4000 in emission. These are among the highest values reported so far for carbon nanotubes coupled with optical microcavity on the silicon platform, highlighting the bright perspectives for carbon nanotube photonics.

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Ref Arxiv: 1512.02877
DOI: 10.1007/s10955-016-1507-y
WoS: WOS:000375579300009
Ref. & Cit.: NASA ADS
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3 Citations
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We prove the existence as well as regularity of a finite range decomposition for the resolvent $G_{\alpha} (x-y,m^2) = ((-\Delta)^{\alpha\over 2} + m^{2})^{-1} (x-y) $, for $0<\alpha<2$ and all real $m$, in the lattice ${\mathbf Z}^{d}$ as well as in the continuum ${\mathbf R}^{d}$ for dimension $d\ge 2$. This resolvent occurs as the covariance of the Gaussian measure underlying weakly self- avoiding walks with long range jumps (stable L\'evy walks) as well as continuous spin ferromagnets with long range interactions in the long wavelength or field theoretic approximation. The finite range decomposition should be useful for the rigorous analysis of both critical and off-critical renormalisation group trajectories. The decomposition for the special case $m=0$ was known and used earlier in the renormalisation group analysis of critical trajectories for the above models below the critical dimension $d_c =2\alpha$.

Commentaires: 16 pages, 1 figure, typos corrected, corrected, reference added, one sentence added

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DOI: 10.1103/PhysRevB.93.224303
WoS: 000378104200007
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13 Citations
Résumé:

High-pressure polarized Raman spectra of vitreous silica are measured up to 8 GPa in a diamond-anvil cell atroom temperature. The combined use of either a nonpenetrating pressurizing medium—argon—or a penetrating one—helium, allows one to separate density from stress effects on the Raman frequencies. In the framework of a simple central force model, the results emphasize the distinct role played by the shrinkage of the intertetrahedral angle Si-O-Si and the force-constant stiffening during the compression. The polarization analysis further reveals the existence of an additional isotropic component in the high-frequency wing of the boson peak. The pressure dependence of the genuine boson peak frequency is found to be much weaker than previously reported and even goes through a minimum around 2 GPa in remarkable coincidence with the anomalous compressibility maximum of silica.

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DOI: 10.1016/j.jnoncrysol.2016.06.023
WoS: 000381841200040
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17 Citations
Résumé:

Brillouin spectroscopy is used to investigate the elastic properties of XAlSiO4 aluminosilicate glasses where X =Li, Na, K, Mg0.5, Ca0.5, Sr0.5, Ba0.5, and Zn0.5. The Brillouin frequency shifts obtained in two different scattering geometries allow the calculation of the refractive index, the two sound velocities and Poisson's ratio.Measurements of the mass density give in turn the elastic moduli and the Debye temperature.We find that the elastic properties scale with the atomic density of the glassy network or the charge-balancing cation field strengthwhile they negatively correlate with the glass transition temperature. Further, Poisson's ratio depends on the nature of the non-framework cations in this glass series.