Spontaneously generated X-shaped light bullets

We observe the formation of an intense optical wavepacket fully localized in all dimensions, i.e. both longitudinally (in time) and in the transverse plane, with an extension of a few tens of fsec and microns, respectively. Our measurements show that the self-trapped wave is a X-shaped light bullet spontaneously generated from a standard laser wavepacket via the nonlinear material response (i.e., second-harmonic generation), which extend the soliton concept to a new realm, where the main hump coexists with conical tails which reflect the symmetry of linear dispersion relationship.Comment: 5 pages, 4 figures, submitted for publicatio

Optimal frequency conversion in the nonlinear stage of modulation instability

We investigate multi-wave mixing associated with the strongly pump depleted regime of induced modulation instability (MI) in optical fibers. For a complete transfer of pump power into the sideband modes, we theoretically and experimentally demonstrate that it is necessary to use a much lower seeding modulation frequency than the peak MI gain value. Our analysis shows that a record 95 % of the input pump power is frequency converted into the comb of sidebands, in good quantitative agreement with analytical predictions based on the simplest exact breather solution of the nonlinear Schr\"odinger equation

Quantum supremacy in mechanical tasks: projectiles, rockets and quantum backflow

We consider a scenario where a non-relativistic one-dimensional quantum particle is prepared in some bounded region of space and left to propagate freely. After a certain amount of time, we check if the particle has reached some distant target region. We find that there exist "ultrafast" ("ultraslow") quantum states, whose probability of arrival is greater (smaller) than that of any classical system prepared in the same region with the same momentum distribution. We prove that the maximum possible difference between quantum and optimal classical arrival probabilities for projectiles, as well as for self-propelling particles or rockets, is limited by the Bracken-Melloy constant $c_{bm}$, introduced in $1969$ to characterize the maximum expression of the phenomenon known as quantum backflow. This mathematical correspondence extends to other examples of mechanical effects with a quantum advantage, whose study we advance by deriving the first rigorous upper bound $c_{bm} \leq 0.0725$. We also prove that the hard limit given by $c_{bm}$ can be overcome in a variant of the original projectile scenario: if the classical particle is required to possess, not just the same momentum distribution as the quantum particle, but also the same position distribution, then the difference between arrival probabilities can reach $0.1228$

Tunneling mediated by conical waves in a 1D lattice

The nonlinear propagation of 3D wave-packets in a 1D Bragg-induced band-gap system, shows that tranverse effects (free space diffraction) affect the interplay of periodicity and nonlinearity, leading to the spontaneous formation of fast and slow conical localized waves. Such excitation corresponds to enhanced nonlinear transmission (tunneling) in the gap, with peculiar features which differ on the two edges of the band-gap, as dictated by the full dispersion relationship of the localized waves.Comment: 5 pages, 6 figure

Transient Propagation and Scattering of Quasi-Rayleigh Waves in Plates: Quantitative comparison between Pulsed TV-Holography Measurements and FC(Gram) elastodynamic simulations

We study the scattering of transient, high-frequency, narrow-band quasi-Rayleigh elastic waves by through-thickness holes in aluminum plates, in the framework of ultrasonic nondestructive testing (NDT) based on full-field optical detection. Sequences of the instantaneous two-dimensional (2-D) out-of-plane displacement scattering maps are measured with a self-developed PTVH system. The corresponding simulated sequences are obtained by means of an FC(Gram) elastodynamic solver introduced recently, which implements a full three-dimensional (3D) vector formulation of the direct linear-elasticity scattering problem. A detailed quantitative comparison between these experimental and numerical sequences, which is presented here for the first time, shows very good agreement both in the amplitude and the phase of the acoustic field in the forward, lateral and backscattering areas. It is thus suggested that the combination of the PTVH system and the FC(Gram) elastodynamic solver provides an effective ultrasonic inspection tool for plate-like structures, with a significant potential for ultrasonic NDT applications.Comment: 46 pages, 16 figures, corresponding author Jos\'e Carlos L\'opez-V\'azquez, [email protected]. Changes: 1st, 4th, 5th paragraphs (intro), 3rd, 4th paragraphs (sec. 4); [59-60] cited only in appendixes; old ref. [52] removed; misprints corrected in the uncertainty of c_L (subsec. 3.1), citation to fig. 10 (sec. 4), size of images (caption fig.15); reference to Lam\'e constants removed in subsec. 3.

Numerical modeling and measurement by pulsed television holography of ultrasonic displacement maps in plates with through-thickness defects

We present a novel numerical modeling of ultrasonic Lamb and Rayleigh wave propagation and scattering by through-thickness defects like holes and slots in homogeneous plates, and its experimental verification in both near and far field by a self-developed pulsed TV holography system. In contrast to rigorous vectorial formulation of elasticity theory, our model is based on the 2-D scalar wave equation over the plate surface, with specific boundary conditions in the defects and plate edges. The experimental data include complex amplitude maps of the out-of-plane displacements of the plate surface, obtained by a two-step spatiotemporal Fourier transform method. We find a fair match between the numerical and experimental results, which allows for quantitative characterization of the defects

Comercialización informal de Cactáceas en las cercanías de Loreto, provincia de Santiago del Estero, Argentina

Fil: Demaio, P. Universidad Nacional de Córdoba. Museo Botánico de Córdoba; Argentina.Fil: Demaio, P. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal; Argentina.Fil: Demaio, P. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Vegetal ll; Argentina.Fil: Trillo, C. Universidad Nacional de Córdoba. Museo Botánico de Córdoba; Argentina.Fil: Trillo, C. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal; Argentina.Fil: Trillo, C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Vegetal ll; Argentina.El comercio de cactus silvestres podría representar una actividad económica sustentable para pobladores de zonas áridas, aunque ha sido mencionado como un factor que podría afectar a las poblaciones naturales.Fil: Demaio, P. Universidad Nacional de Córdoba. Museo Botánico de Córdoba; Argentina.Fil: Demaio, P. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal; Argentina.Fil: Demaio, P. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Vegetal ll; Argentina.Fil: Trillo, C. Universidad Nacional de Córdoba. Museo Botánico de Córdoba; Argentina.Fil: Trillo, C. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal; Argentina.Fil: Trillo, C. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Diversidad Vegetal ll; Argentina.Conservación de la Biodiversida

Nonlocal description of X waves in quadratic nonlinear materials

We study localized light bullets and X waves in quadratic media and show how the notion of nonlocality can provide an alternative simple physical picture of both types of multidimensional nonlinear waves. For X waves we show that a local cascading limit in terms of a nonlinear Schrödinger equation does not exist—one needs to use the nonlocal description, because the nonlocal response function does not converge toward a δ function. Also, we use the nonlocal theory to show that the coupling to the second harmonic is able to generate an X shape in the fundamental field despite having anomalous dispersion, in contrast to the predictions of the cascading limit