Spin-Glass Model Governs Laser Multiple Filamentation

Physical Review Letters, 2015

We show that the onset of laser multiple filamentation can be described as a critical phenomenon that we characterize both experimentally and numerically by measuring a set of seven critical exponents. This phase transition deviates from any existing universality class, and offers a unique perspective of conducting two-dimensional experiments of statistical physics at a human scale.

Optics Letters, 2016

Physical Review Letters, 2017

While propagating in transparent media, near-infrared multi-terawatt (TW) laser beams break up in a multitude of filaments of typically 100-200 um diameter with peak intensities as high as 10 to 100 TW/cm 2 . We observe a phase transition at incident beam intensities of 0.4 TW/cm 2 , where the interaction between filaments induce solid-like 2-dimensional crystals with a 2.7 mm lattice constant, independent of the initial beam diameter. Below 0.4 TW/cm 2 , we evidence a mixed phase state in which some filaments are closely packed in localized clusters, nucleated on inhomogeneities (seeds) in the transverse intensity profile of the beam, and other are sparse with almost no interaction with their neighbors, similar to a gas. This analogy with a thermodynamic gas-solid phase transition is confirmed by calculating the interaction Hamiltonian between neighboring filaments, which takes into account the effect of diffraction, Kerr self-focusing and plasma generation. The shape of the effective potential is close to a Morse potential with an equilibrium bond length close to the observed value.

Physica D: Nonlinear Phenomena, 2001

The standard explanation for multiple filamentation of laser beams is that breakup of cylindrical symmetry is initiated by noise in the input beam. In this study we propose an alternative deterministic explanation based on vectorial effects. We derive a scalar equation from the vector Helmholtz equation that describes self-focusing in the presence of vectorial and nonparaxial effects. Numerical simulations of the scalar equation show that when the input beam is sufficiently powerful, vectorial effects lead to multiple filamentation. We compare multiple filamentation due to vectorial effects with the one due to noise, and suggest how to decide which of the two leads to multiple filamentation in experiments. We also show that vectorial effects and nonparaxiality have the same effect on self-focusing of a single filament, leading to the arrest of catastrophic collapse, followed by focusing-defocusing oscillations. The magnitude of vectorial effects is, however, significantly larger than that of nonparaxiality.

Optics Letters, 2001

The standard explanation for multiple filamentation of laser pulses is that it is caused by noise in the input beam. We propose an alternative explanation that is based on deterministic vectorial (polarization) effects. We present numerical simulations in support of the vectorial-effects explanation and suggest a simple experiment for deciding whether multiple filamentation is due to vectorial effects.

2020

Problems of modeling the creation the volume laser-induced structures (filaments) are very interesting [1 – 5]. These structures have various sizes: from nanometetrs in solid [6, 7] to few hundred meters in air [8 – 12]. In whole, we can have various processes and phenomena, which are connected with photochemical, plasmic and thermochemical processes [2 – 5, 13, 14]. It may be various processes, including the cascade and circle processes. Irreversible changes of laser-irradiated volume of matter must be explained as phase transformations. These processes have shock nature and connected with multiphoton scattering processes [15, 16].

arXiv (Cornell University), 2023

We experimentally investigate fluctuations in the spectrum of ultrashort laser pulses propagating in air, close to the critical power for filamentation. Increasing the laser peak power broadens the spectrum while the beam approaches the filamentation regime. We identify two regimes for this transition: In the center of the spectrum, the output spectral intensity increases continuously. In contrast, on the edges of the spectrum the transition implies a bimodal probability distribution function for intermediate incident pulse energies, where a high-intensity mode appears and grows at the expense of the original low-intensity mode. We argue that this dual behavior prevents the definition of a univoquial threshold for filamentation, shedding a new light on the long-standing lack of explicit definition of the boundary of the filamentation regime.

2019

Recent experiments suggest that the onset of lasing in optically active disordered media is related to an ergodicity-breaking transition for the degrees of freedom of the electromagnetic field. We test this hypothesis in numerical simulations of the dynamics of nonlinearly coupled light modes under external pumping. The collective behavior of light mode amplitudes appears to be akin to the one displayed in glass formers around the ergodicity breaking glass transition: a critical pumping exists, beyond which the thermodynamic phase is fragmented into a multitude of states. The probability distribution of the overlap between such states, i.e., the glass order parameter, turns out to be well described by the replica symmetry breaking scheme. The unprecedented observation is that such symmetry breaking occurs at the same pumping power values at which a lack of equipartition among light modes arises. Finally, we show that the mean-field scenario for the glass transition is quite robust f...

2015

At incident powers much higher than the threshold for filamentation a pulse from a high-power laser generates in the transversal plane a complex structure. It consists of randomly meandering stripes defining connected regions where the field intensity is high; and, the complementary regions dominated by diffusive plasma with defocusing property. The pattern is similar to an ensemble of clusters of various extensions. We provide evidence that there is a correlation between this filamentation and the labyrinth instability in reaction-diffusion systems. Besides the similarity of the spatial organization in the two cases, we show that the differential equations that describe these two dynamical processes lead to effects that can be mutually mapped. For the laser beam at high power the Non-linear Schrodinger Equation in a regime of strong self-focusing and ionization of the air leads to multiple filamentation and the structure of clusters. Under the effect of the labyrinth instability a ...

Laser Physics, 2012

We investigated the evolution of femtosecond laser pulses at different wavelengths corresponding to normal, zero, and anomalous regimes of group velocity dispersion (GVD) in fused silica. The laser pulse filamentation in different GVD regimes under the same similarity parameters was first considered. It was established numerically that the scenario of the pulse filamentation depends both on temporal factors, which are determined by pulse GVD and self phase modulation, and spatial factors associated with Kerr self focus ing and plasma defocusing. In presence of strong normal GVD the dispersive stretching causes, a pulse power decrease followed by lowering of the intensity in filament, electron density reduction in plasma channel, and suppressing of the refocusing. For zero GVD the multipeak regime of radiation propagation is realized in the filament as a result of recurring self focusings of powerful pulse tail, which was defocused in laser plasma. When GVD is anomalous a sequence of "light bullets" with duration about 10 fs forms in the filament. And the peak intensity in "light bullet" stays the same ≈ 5 × 10 13 W/cm 2 . In the regime of anomalous GVD power is transferred from the pulse edges to its center, where the repeated self focusings occur and form a "light bul let" sequence.