Filamentation in Kerr media from pulsed Bessel beams

In contrast with filamentation of ultrashort laser pulses with standard Gaussian beams in Kerr media, three different types of Bessel filaments are obtained in air or in water by focusing ultrashort laser pulses with an axicon. We thoroughly investigate the different regimes and show that the beam reshapes as a nonlinear Bessel beam which establishes a conical energy flux from the low intensity tails toward the high intensity peak. This flux efficiently sustains a high contrast long-distance propagation and easily generates a continuous plasma channel in air

Observation of ConicalWaves in Focusing, Dispersive, and Dissipative Kerr Media

Excitation of unbalanced-Bessel beams by a gradual increase of nonlinearity in a water sample outlines the achievement of the first ever observed quasimonochromatic wave packet that propagates stably for hundreds of Rayleigh lengths in a focusing and dispersive Kerr medium, i.e., in the absence of spectral broadening and conical emission. A modulational instability analysis reveals the key role of nonlinear dissipation in quenching the growth of spatiotemporal unstable modes

Observation of ConicalWaves in Focusing, Dispersive, and Dissipative Kerr Media

Excitation of unbalanced-Bessel beams by a gradual increase of nonlinearity in a water sample outlines the achievement of the first ever observed quasimonochromatic wave packet that propagates stably for hundreds of Rayleigh lengths in a focusing and dispersive Kerr medium, i.e., in the absence of spectral broadening and conical emission. A modulational instability analysis reveals the key role of nonlinear dissipation in quenching the growth of spatiotemporal unstable modes

Nonlinear vortex light beams supported and stabilized by dissipation

We describe nonlinear Bessel vortex beams as localized and stationary solutions with embedded vorticity to the nonlinear Schr\"odinger equation with a dissipative term that accounts for the multi-photon absorption processes taking place at high enough powers in common optical media. In these beams, power and orbital angular momentum are permanently transferred to matter in the inner, nonlinear rings, at the same time that they are refueled by spiral inward currents of energy and angular momentum coming from the outer linear rings, acting as an intrinsic reservoir. Unlike vortex solitons and dissipative vortex solitons, the existence of these vortex beams does not critically depend on the precise form of the dispersive nonlinearities, as Kerr self-focusing or self-defocusing, and do not require a balancing gain. They have been shown to play a prominent role in "tubular" filamentation experiments with powerful, vortex-carrying Bessel beams, where they act as attractors in the beam propagation dynamics. Nonlinear Bessel vortex beams provide indeed a new solution to the problem of the stable propagation of ring-shaped vortex light beams in homogeneous self-focusing Kerr media. A stability analysis demonstrates that there exist nonlinear Bessel vortex beams with single or multiple vorticity that are stable against azimuthal breakup and collapse, and that the mechanism that renders these vortexes stable is dissipation. The stability properties of nonlinear Bessel vortex beams explain the experimental observations in the tubular filamentation experiments.Comment: Chapter of boo

Do consumers dream of digital advertising? New communication rules in social media

O objetivo deste artigo é analisar a forma recente de comunicação e as regras retóricas utilizadas atualmente para otimizar o impacto publicitário nas mídias sociais. Depois de ter descrito, com a ajuda da literatura, as principais diretrizes comunicativas para novas mídias e mídias sociais, as recentes regras de comunicação serão testadas com os consumidores. Portanto, para melhor elaborar esses tópicos, faremos uso de uma pesquisa exploratória realizada na Universidade Iulm de Milão, na primavera de 2019. A pesquisa responderá aos gostos e desgostos em relação à comunicação na mídia social e publicidade. Assim, as descobertas da pesquisa sobre o consumidor podem ajudar pesquisadores e profissionais de marketing a entender melhor o nascimento dessas novas formas de comunicação. Outro foco desta pesquisa será analisar se a tecnologia social é um viés e, se for, até que ponto. Por fim, os consumidores adoram a publicidade digital nas mídias sociais? Na verdade, toda nova tecnologia requer novas linguagens e, com efeito, isso deve acontecer quando o impacto tecnológico estiver relacionado à mídia. Em suma, as mídias sociais parecem ser um bom terreno para explorar as mudanças recentes na comunicação e, especificamente, na publicitária. As descobertas da pesquisa exploratória podem levar a outras questões, tais como: a comunicação e a propaganda mudam da mesma forma? No mesmo ritmo? Elas vão na mesma direção? Em que medida? A publicidade simplesmente tem que seguir as novas regras de comunicação ou é forçada a usar e inventar novas formas de comunicação? O presente artigo somente será capaz de delinear e rapidamente esquematizar possíveis respostas para as questões que, de fato, estão destinadas a desenvolver outras considerações e pesquisas adicionais.El presente artículo tiene como objetivo analizar la actual forma de comunicación y las normas retóricas utilizadas para optimizar el impacto de la publicidad en los medios sociales. Con base en la literatura, se describieron las principales directrices comunicativas de los nuevos medios y de los medios sociales, y se sometieron las nuevas normas de comunicación a los consumidores. Para elaborar estos temas, se hizo una investigación exploratoria realizada en la Universidad Iulm de Milán, en la primavera de 2019. En la encuesta tenían que contestar las preferencias y las no preferencias en relación a la comunicación en los medios sociales y la publicidad. Se espera que los hallazgos de la investigación sobre el consumidor puedan aportar más informaciones a los investigadores y profesionales de marketing para mejor entender el surgimiento de esas nuevas formas de comunicación. Otro objetivo de esta investigación es analizar si la tecnología social es una tendencia y hasta qué punto lo es. Y por último es conocer si los consumidores les gusta la publicidad digital en los medios sociales. Cada nueva tecnología requiere nuevos lenguajes, y esto debe suceder cuando se vincule el nuevo impacto tecnológico con los medios. En resumen, los medios sociales parecen ser una buena forma de explorar los recientes cambios en la comunicación, más específicamente en la comunicación publicitaria. Los hallazgos de la investigación exploratoria pueden llevar a nuevos cuestionamientos, tales como: ¿La comunicación y la propaganda pasan por los mismos cambios? ¿En el mismo ritmo? ¿Van hacia la misma dirección? ¿En qué punto? ¿La publicidad simplemente debe seguir las nuevas normas de comunicación o es obligada a utilizar e inventar nuevas formas de comunicarse? El presente artículo solamente puede delinear y esquematizar posibles respuestas a estos cuestionamientos, que pueden desarrollarse en otras consideraciones e investigaciones adicionales.This paper aims to analyze the recent forms of communication and the rhetoric rules that are used nowadays to optimize the advertising impact on social media. After having described, with the help of the literature, the main communicative guidelines for new media and social media, the new communication rules will be tested with the consumers. Therefore, to better elaborate on these topics, we will make use of an exploratory research conducted in the IULM University of Milan in spring 2019. The research will provide answers as to the likes and dislikes regarding the social media communication and advertising. Thus, the consumer research findings can help researchers and marketers to better understand the rise of those new forms of communication. This research will also focus on analyzing whether the social technology is a bias and to what extent. Finally, do consumers love digital advertising on social media? Actually, every new technology requires new languages and, a fortiori, this must happen when the new technology impact is related with the media. In sum, the social media seem to be fertile ground to explore recent changes in communication, and specifically in advertising communication. The findings of the exploratory research can lead to new questions, such as: do communication and advertising change in the same manner? At the same pace? Do they go in the same direction? And to what extent? Does advertising simply have to follow the new communication rules or is it forced to use and invent new forms of communication? This paper will only be able to outline and quickly schematize possible answers to the questions that, indeed, are bound to lead to further considerations and further researches

Ultrafast laser micro-nano structuring of transparent materials with high aspect ratio

Ultrafast lasers are ideal tools to process transparent materials because they spatially confine the deposition of laser energy within the material's bulk via nonlinear photoionization processes. Nonlinear propagation and filamentation were initially regarded as deleterious effects. But in the last decade, they turned out to be benefits to control energy deposition over long distances. These effects create very high aspect ratio structures which have found a number of important applications, particularly for glass separation with non-ablative techniques. This chapter reviews the developments of in-volume ultrafast laser processing of transparent materials. We discuss the basic physics of the processes, characterization means, filamentation of Gaussian and Bessel beams and provide an overview of present applications

Filamentation in Kerr media from pulsed Bessel beams

In contrast with filamentation of ultrashort laser pulses with standard Gaussian beams in Kerr media, three different types of Bessel filaments are obtained in air or in water by focusing ultrashort laser pulses with an axicon. We thoroughly investigate the different regimes and show that the beam reshapes as a nonlinear Bessel beam which establishes a conical energy flux from the low intensity tails toward the high intensity peak. This flux efficiently sustains a high contrast long-distance propagation and easily generates a continuous plasma channel in air

Spatio-temporal reshaping and X wave dynamics in optical filaments

We investigate ultrashort laser pulse filamentation within the framework of spontaneous X Wave formation. After a brief overview of the filamentation process we study the case of an intense filament co-propagating with a weaker seed pulse. The filament is shown to induce strong Cross-Phase-Modulation (XPM) effects on the weak seed pulse: driven by the pump, the seed pulse undergoes pulse splitting with the daughter pulses slaved to their pump counterparts. They undergo strong spatio-temporal reshaping and are transformed into XWaves traveling at the same group velocities as the pump split-off pulses. In the presence of a gain mechanism such as Four-Wave-Mixing or Stimulated Raman Scattering, energy is then transferred from the pump filament leading to amplification of the seed X Wave and formation of a temporally compressed intensity peak

Conical waves in the frontier between linear, nonlinear and quantum optics

Nonlinear conical waves support stationary and localized modes in presence of nonlinear dissipation and/or chromatic dispersion. The virtually unbounded "conical instability" causes interplay between classical and quantum effects in the nonlinear dynamics of extended waves. © 2005 Optical Society of America