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Alerstam E.,Lund University | Svensson T.,Lund University | Svensson T.,European Laboratory for Non linear Spectroscopy LENS
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

By analyzing spatio-temporal characteristics of short optical pulses diffusively transmitted through compacted granular materials, we reveal that powder compaction can give rise to strongly anisotropic light diffusion. Our disclosure represents a revision of the understanding of optics of powder compacts. Routes to material characterization and investigation of compression-induced structural anisotropy are opened, and the falsification of isotropic models have implications for quantitative spectroscopy of powder compacts (e.g., pharmaceutical tablets). © 2012 American Physical Society. Source

Sgrignuoli F.,University of Florence | Sgrignuoli F.,European Laboratory for Non linear Spectroscopy LENS | Bettotti P.,University of Trento
Journal of the Optical Society of America B: Optical Physics

The effect of surface roughness on the optical absorption of a porous material is numerically investigated. We performed a comparative study among different porous geometries and we demonstrate that the presence of the roughness significantly increases the optical absorption of light. This effect is optimized by using a proper matching layer that minimizes losses and maximizes absorption. Enhanced absorption is achieved over a broad range of wavelengths in these simple bilayered structures. The results of this work can be used to design more effective light trapping devices, e.g., third-generation photovoltaic back reflector exploiting the band gap incident radiation. © 2016 Optical Society of America. Source

Belenchia A.,International School for Advanced Studies | Belenchia A.,National Institute of Nuclear Physics, Italy | Benincasa D.M.T.,International School for Advanced Studies | Liberati S.,International School for Advanced Studies | And 5 more authors.
Physical Review Letters

Several quantum gravity scenarios lead to physics below the Planck scale characterized by nonlocal, Lorentz invariant equations of motion. We show that such nonlocal effective field theories lead to a modified Schrödinger evolution in the nonrelativistic limit. In particular, the nonlocal evolution of optomechanical quantum oscillators is characterized by a spontaneous periodic squeezing that cannot be generated by environmental effects. We discuss constraints on the nonlocality obtained by past experiments, and show how future experiments (already under construction) will either see such effects or otherwise cast severe bounds on the nonlocality scale (well beyond the current limits set by the Large Hadron Collider). This paves the way for table top, high precision experiments on massive quantum objects as a promising new avenue for testing some quantum gravity phenomenology. © 2016 American Physical Society. Source

Eramo R.,CNR Institute of Neuroscience | Eramo R.,European Laboratory for Non linear Spectroscopy LENS | Cavalieri S.,European Laboratory for Non linear Spectroscopy LENS | Cavalieri S.,University of Florence | And 4 more authors.
Physical Review Letters

Ramsey-like schemes have been recently introduced in combination with high-order laser harmonic sources for high-resolution spectroscopic studies in the extreme ultraviolet (XUV). Here we demonstrate a novel method, combining measurements only in a limited subset of randomly chosen time-sampling intervals, which lead us to perform the first high-resolution XUV spectroscopy of atomic argon with a simple split-pulse setup. Providing an experimentally simple and convenient solution to the problem of performing high-resolution absolute frequency measurements in the XUV, our approach will help paving new roads into this challenging spectral territory. © 2011 American Physical Society. Source

Marin F.,University of Florence | Marin F.,National Institute of Nuclear Physics, Italy | Marin F.,European Laboratory for Non linear Spectroscopy LENS | Marino F.,European Laboratory for Non linear Spectroscopy LENS | And 17 more authors.
Nature Physics

Different approaches to quantum gravity, such as string theory 1,2 and loop quantum gravity, as well as doubly special relativity3 and gedanken experiments in black-hole physics4-6, all indicate the existence of a minimal measurable length7,8 of the order of the Planck length, Lp=/NG/c3= 1.6×10-35 m. This observation has motivated the proposal of generalized uncertainty relations, which imply changes in the energy spectrum of quantum systems. As a consequence, quantum gravitational effects could be revealed by experiments able to test deviations from standard quantum mechanics9-11, such as those recently proposed on macroscopic mechanical oscillators12. Here we exploit the sub-millikelvin cooling of the normal modes of the ton-scale gravitational wave detector AURIGA, to place an upper limit for possible Planck-scale modifications on the ground-state energy of an oscillator. Our analysis calls for the development of a satisfactory treatment of multi-particle states in the framework of quantum gravity models. © 2013 Macmillan Publishers Limited. All rights reserved. Source

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