3,165 research outputs found
Quantum electromagnetic X waves
No full textWe provide a quantum description of X waves by considering two different kinds of quantum states of the electromagnetic field whose field amplitude expectation value coincides with a propagation-invariant solution of the Maxwell equation. The difference between the two states is of pure quantum mechanical origin since they are internally entangled and disentangled and can be generated by different linear or nonlinear processes. (c) 2007 Optical Society of America
Spontaneous photonic lattices and nonlinear waves in nanodisordered ferroelectrics
No full textIn this Thesis we deal with nanodisordered ferroelectric perovskite crystals. These material have been demonstrated to be a good test-bed to study nonlinear optical phenomena due to their strong optical properties. In fact, their embedded disorder enhances their response at the phase transition and makes these materials suitable to sustain solitons and rogue waves also with low optical power.
We first use self-focusing at the paraelectric phase to study nonlinear wave propagation. Our experiments are conceived to investigate the evolution of structured waves in time and in space. We make three beams to interfere to optically observe the Fermi-Pasta-Ulam-Tsingou recurrence. We experimentally verify its analytic solution provided by Grinevich-Santini that allows us to predict the exact position of each recurrence. Moreover, we demonstrate that the periodic behavior is lost if the system ceases to be integrable. We study the appropriate interference pattern in the form of nondiffractive Bessel beams to investigate what happens to such waves in a self-focusing medium. We identify two regimes: a Bessel beam selftrapping and a breathing soliton. Furthermore, we demonstrate the feasibility of Bessel beam writing to build a scalable and rewritable network of waveguides inside the bulk ferroelectric medium.
We also studied the unique properties of the ferroelectric phase. The most evident outcome is the so-called super-crystal that is a spontaneous photonic 3D lattice that emerges from the interplay between material order and disorder. We study the super-crystal in different ways and we recover the periodic behavior for linear and nonlinear propagation. In detail we report a periodic pattern for birefringence and second harmonic generation. The main result is that we have observed the highest value of the refractive index reported in literature for visible light and we have connected the effect to the super-crystal. This material allows, in theory, to transmit light without any information loss, that is without diffraction and chromatic dispersion.
The physics of diffraction is also investigated with the introduction of an innovative method to achieve super-resolution. We exploit a confocal microscope and a remote knifeedge technique. This allows us to directly study the role of evanescent waves in superresolution imaging forming, i.e. they are filtered out as the super-resolved image approaches to the diffraction-limited one. Experiments here are performed with a terahertz frequency, λ ∼ 1.00 mm, to easily accede the near field and capture the information carried by the evanescent wave
All-optical modulation in wavelength-sized epsilon-near-zero media
No full textWe investigate the interaction of two pulses (pump and probe) scattered by a nonlinear epsilon-near-zero (ENZ) slab whose thickness is comparable with the ENZ wavelength. We show that when the probe has a narrow spectrum localized around the ENZ wavelength, its transmission is dramatically affected by the intensity of the pump. Conversely, if the probe is not in the ENZ regime, its propagation is not noticeably affected by the pump. Such all-optical modulation is due to the oversensitive character of the ENZ regime, and it is so efficient that it even occurs in a wavelength thick slab
Extreme nonlinear optical regime supported by metamaterials: Beam transverse power flow reversing
No full textEfficient Vortex Generation in Subwavelength Epsilon-Near-Zero Slabs
No full textWe show that a homogeneous and isotropic slab, illuminated by a circularly polarized beam with no topological charge, produces vortices of order 2 in the opposite circularly polarized components of the reflected and transmitted fields, as a consequence of the transverse magnetic and transverse electric asymmetric response of the rotationally invariant system. In addition, in the epsilon-near-zero regime, we find that vortex generation is remarkably efficient in subwavelength thick slabs up to the paraxial regime. This physically stems from the fact that a vacuum paraxial field can excite a nonparaxial field inside an epsilon-near-zero slab since it hosts slowly varying fields over physically large portions of the bulk. Our theoretical predictions indicate that epsilon-near-zero media hold great potential as nanophotonic elements for manipulating the angular momentum of the radiation, since they are available without resorting to complicated micro- or nanofabrication processes and can operate even at very small (ultraviolet) wavelengths
Universal space-time properties of X waves
No full textExact results concerning spatiotemporal universal features of three-dimensional propagation-invariant solutions of the wave equation (X waves) are derived. In particular, relations connecting the pulse transverse extension to the longitudinal coordinate and the propagation velocity to the spatial field distribution are obtained for the whole class of X waves. (C) 2004 Optical Society of America
Out-of-equilibrium electron dynamics of silver driven by ultrafast electromagnetic fields–a novel hydrodynamical approach
No full textA imagem de Alessandro Baricco no Brasil
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Estudos da Tradução, Florianópolis, 2013.Com a intenção de delinear o modo pelo qual o escritor italiano Alessandro Baricco se inseriu no sistema literário brasileiro e os caminhos percorridos pelos seus livros traduzidos, esta dissertação dá voz às experiências tradutórias de seus tradutores. A inserção de Bariccono Brasil tem seu início em 1997, através de uma proposição da Profa. Dra. Roberta Barni à editora Iluminuras da tradução de Oceano Mare. A partir daí, outras sete obras foram publicadas no Brasil, sendo três delas traduzidas por Roberta Barni e as outras quatro por quatro tradutores diferentes. De um lado, considera-se o tradutor como figura principal namediação entre culturas, e, de outro, se analisa a realidade desta figuradentro do sistema literário, sua invisibilidade, seus limites e o exercíciode sua profissão. A pesquisa conta, ainda, com críticas e resenhas referentes ao autor italiano publicadas em jornais consagrados no Brasil, considerando estas como parte constituinte da imagem de Baricco refletida em território nacional. Abstract : Intending to delineate the way the Italian writer Alessandro Baricco has been inserted in the Brazilian literary system and the paths his translated books have followed, this thesis gives voice to the translating experiences of his translators. Baricco's insertion in Brazil began in 1997, through a personal project of Dr. Roberta Barni, with her translation of Oceano Mare. Since then, seven other of his works have been published in Brazil, three of which were translated by Roberta Barni and the other four by four different translators. On the one hand,the translator is considered as the main figure in mediation betweencultures and, on the other, this figure's reality is analyzed within theliterary system: its invisibility, its limits and its professional practice. Criticisms and reviews of this Italian author published in well established Brazilian newspapers are also considered, with the understanding that they are part of Baricco's image reflected here
Approach to space-charge field description in photorefractive crystals
No full textRecent analytical results in the frame of photorefractive spatial-soliton propagation are exploited to derive a novel scheme for the investigation of space-charge field formation in photorefractive crystals. The procedure is specialized to describe a two-wave mixing configuration. To test our predictions, we have performed an experiment in a sample of BaTiO3. © 1998 Optical Society of America
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