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.
Replica Symmetry Breaking paper in Nature Communications !
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Last Updated (Saturday, 24 January 2015 14:25)
Replica Symmetry Breaking in Random Lasers
N. Ghofraniha, I. Viola, F. Di Maria, G. Barbarella, G. Gigli, L. Leuzzi and C. Conti reported on the first evidence of Replica Symmetry Breaking in Random Lasers by the direct measurement of the Parisi overlap distribution function (arXiv:1407.5428, Nature Communications 2015)
Spin-glass theory is one of the leading paradigms of complex physics and describes condensed matter, neural networks and biological systems, ultracold atoms, random photonics, and many other research fields. According to this theory, identical systems under identical conditions may reach different states and provide different values for observable quantities. This effect is known as Replica Symmetry Breaking and is revealed by the shape of the probability distribution function of an order parameter named the Parisi overlap. However, a direct experimental evidence in any field of research is still missing. Here we investigate pulse-to-pulse fluctuations in random lasers, we introduce and measure the analogue of the Parisi overlap in independent experimental realizations of the same disordered sample, and we find that the distribution function yields evidence of atransition to a glassy light phase compatible with a replica symmetry breaking.
Last Updated (Saturday, 17 January 2015 09:04)
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."
Last Updated (Sunday, 14 December 2014 10:37)
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 this manuscript (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.
Last Updated (Saturday, 03 January 2015 09:51)