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This is the website of the Laboratory of Nonlinear Photonics and Theoretical Physics at the Department of Physics of the University Sapienza and the Institute for Complex Systems of the National Research Council. Our program is applying paradigms from the science of complex systems to light propagation, and investigating the development of complexity and self-organization in nonlinear waves. We want to test and deepen ideas of fundamental physics by using optics and photonics, and developing experiments, high performance computing approaches, and theory.

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Three-dimensional rogue waves by random media go through obstacles

Formerly considered a myth, the sudden formation of giant waves in a sea of low amplitude wavelets is nowadays an important subject of interdisciplinary research. These “rogue waves” (RW) are studied in different contexts, and their understanding is a challenge characterized by an intense discussion and a number of potential applications. 

It is commonly accepted that the physics underlying the generation of giant oceanic RW is different from that of usual waves and that the triggering mechanism of RWs is not unique: linear effects (such as the focusing of independent wave trains) as well as the nonlinear amplification of noise may produce RWs.

In a paper published in Applied Physics Letters, Marco Leonetti and Claudio Conti use a spatial light modulator (SLM) to explore the possible speckle configurations generated by a random medium  to generate and control a three-dimensional rogue wave.

They demonstrate that the SLM allows to select among all the possible realizations, the RW located at a user defined position in the shadow of the nearly totally reflecting obstacle. Moreover, by tuning the properties of the speckle pattern, the localization along the propagation axis can be controlled.

The picture below show the three-dimensional reconstruction of the observed rogue-wave.

RogueWave3DleonettiAPL2015

Last Updated (Sunday, 19 July 2015 10:13)

 

Relativistic analogue in non-paraxial shock waves

Shock generation and wave-breaking are effects largely investigated in nonlinear optics. They are always occurring in extreme regimes with a variety of fundamental physical implications, and a number of applications, ranging from particle and material manipulation, to supercontinuum and X-ray generation.

In nonlinear optics, one studies shocks in space and time. Concerning the spatial case, shock waves are observed as highly irregular wave-fronts that originate upon the propagation of a smooth Gaussian beam in a strongly nonlinear medium like, for example, a thermal liquid.

So far, the analysis of spatial shock waves has been limited by the paraxial approximation. The validity of this approximation, however, is questioned by the large spatial bandwidth that is observed at the shock formation.

In a manuscript published in Optics Communications (arXiv:1412.8602) Silvia Gentilini, Eugenio Del Re and Claudio Conti study theoretically and computationally the effects of the non-paraxial regime on the shocks. The result is a predicted correction to the maximal spatial bandwidth after the shock generation, which is within experimentally measurable values, and which is also relevant for temporal shock waves.

The analysis is fascinating, as it shows that non-paraxial terms can be mapped to the relativistic corrections that occur when one considers the propagation of particles with velocity comparable with the speed of light. In other words, the mathematical treatment of the non-paraxial shock is analogue to the treatment of the relativistic particle motion. The trajectories of the particles corresponds to the so-called characteristic lines.

This problem is also relevant for mathematical investigations concerning wave-breaking in high-order nonlinear partial differential equations.

The picture below shows an example of  the calculation of the relativistic shock wave front.

nonparaxialshock

Last Updated (Sunday, 19 July 2015 09:45)

 

Geometric explanation of Rogue Solitons featured in the Cover of Optica

The geometrical approach for explaining the origin of Rogue Solitons has been featured in the Cover of OPTICA!

opticacover

 

Optomechanics of random media: towards Photonic Robots

The Brownian motion of photons in a random medium induces a Brownian motion of the medium.

Anderson localization of light enhances the optomechanical interaction.

These effects are considered in a manuscript, by Silvia Gentilini and Claudio Conti, based on massively parallel numerical solutions of the Maxwell equations for random media. The goal is designing micron-sized structured devices that are activated by light and perform a prescribed motion. Understanding the role of light scattering is pivotal in the realization of "Photonic Robots."

Now published in Phys. Rev. A

optomechanicsrandom

Last Updated (Sunday, 12 April 2015 16:11)