Clusters of cavity solitons bounded by conical radiation

We introduce a new class of self-sustained states, which may exist as single solitons or form multisoliton clusters, in driven passive cylindrical microresonators. Remarkably, such states are stabilized by the radiation they emit, which strongly breaks spatial symmetry and leads to the appearance of long polychromatic conical tails. The latter induce long-range soliton interactions that make possible the formation of clusters, which can be stable if their spatial arrangement is non-collinear with the soliton rotation direction in the microcavity. The clusters are intrinsically two-dimensional and, also, spatially rich. The mechanism behind the formation of the clusters is explained using soliton clustering theory. Our results bring fundamental understanding of a new class of multidimensional cavity solitons and may lead to the development of monolithic multi-soliton sources.Comment: 12 pages, 9 figures, to appear in Physical Review Letter

Laser beam self-symmetrization in air in the multifilamentation regime

We show experimental and numerical evidence of spontaneous self-symmetrization of focused laser beams experiencing multi-filamentation in air. The symmetrization effect is observed as the multiple filaments generated prior to focus approach the focal volume. This phenomenon is attributed to the nonlinear interactions amongst the different parts of the beam mediated by the optical Kerr effect, which leads to a symmetric redistribution of the wave vectors even when the beam consists of a bundle of many filaments.Comment: 9 pages, 7 figure

Bound states in the continuum in a two-dimensional PT - symmetric system

© 2018 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved.We address a 2D parity-time (¿¿)-symmetric structure built as a chain of waveguides, where all waveguides except for the central one are conservative, while the central one is divided into two halves with gain and losses. We show that such a system admits bound states in the continuum (BICs) whose properties vary drastically with the orientation of the line separating amplifying and absorbing domains, which sets the direction of internal energy flow. When the flow is perpendicular to the chain of the waveguides, narrow BICs emerge when the standard defect mode, which is initially located in the finite gap, collides with another mode in a standard symmetry breaking scenario, and its propagation constant enters the continuous spectrum upon increase of the strength of gain/losses. In contrast, when the energy flow is parallel to the chain of the waveguides, the symmetry gets broken even for a small strength of the gain/losses. In that case, the most rapidly growing mode emerges inside the continuous spectrum and realizes a weakly localized BIC. All BICs found here are the most rapidly growing modes; therefore, they can be excited from noisy inputs and, importantly, should dominate the beam dynamics in experiments.Peer ReviewedPostprint (author's final draft

Anomalous effects of radioactive decay rates and capacitance values measured inside a modified Faraday cage: Correlations with space weather

[EN] Recently we reported (Mili¿an-S¿anchez V. et al., Nucl. Instrum. Methods A, 828 (2016) 210) our experimental results involving 226Ra decay rate and capacitance measurements inside a modified Faraday cage. Our measurements exhibited anomalous effects of unknown origin. In this letter we report new results regarding our investigation into the origins of the observed effects. We report preliminary findings of a correlation analysis between the radioactive decay rates and capacitance time series and space weather related variables (geomagnetic field disturbances and cosmic-ray neutron counts). A significant correlation was observed for specific data sets. The results are presented and possible implications for future work discussed.Scholkmann, F.; Milian Sanchez, V.; Mocholí Salcedo, A.; Milián Enrique, C.; Kolombet, V.; Verdú Martín, GJ. (2017). Anomalous effects of radioactive decay rates and capacitance values measured inside a modified Faraday cage: Correlations with space weather. EPL (Europhysics Letters). 117(6):62002-1-62002-3. doi:10.1209/0295-5075/117/62002S62002-162002-3117

Robust three-dimensional high-order solitons and breathers in driven dissipative systems: a Kerr cavity realization

We present a general approach to excite robust dissipative three-dimensional and high-order solitons and breathers in passively driven nonlinear cavities. Our findings are illustrated in the paradigmatic example provided by an optical Kerr cavity with diffraction and anomalous dispersion, with the addition of an attractive three-dimensional parabolic potential. The potential breaks the translational symmetry along all directions, and impacts the system in a qualitatively unexpected manner: three-dimensional solitons, or light-bullets, are the only existing and stable states for a given set of parameters. This property is extremely rare, if not unknown, in passive nonlinear physical systems. As a result, the excitation of the cavity with any input field leads to the deterministic formation of a target soliton or breather, with a spatiotemporal profile that unambiguously corresponds to the given cavity and pumping conditions. In addition, the tuning of the potential width along the temporal direction results in the existence of a plethora of stable asymmetric solitons. Our results may provide a solid route towards the observation of dissipative light bullets and three-dimensional breathers

Social Violence, Structural Violence, Hate, and the Trauma Surgeon

Violence can be committed against oneself or against another person or group. As trauma surgeons, we are often required to administer urgent surgical interventions on patients who have sustained life-threatening injuries, including from violence. The roots of such violence, nationally and globally, are related to structures of discrimination and alienation, termed “structural violence.” This is embedded in ubiquitous social structures and normalized by stable institutions and regular experience while “normalizing the abnormal.” Surgeons and physicians have a long history of critical analysis of the upstream “causes of the causes” to understand and prevent further harm. Hate can be well adapted to the classic public health model of the spread of “disease,” with hate speech as the vector leading to direct violence. Social medicine views social inequality as the cause of disease, with political action required to protect and improve population health. It acknowledges the need to address and end structural violence, through political solutions. It is our responsibility to create the dignified environments of growth and progress for our patients and to challenge the agents of harm such as hate and discrimination. As Dr. Norman Bethune, the father of social surgery stated, “Charity should be abolished, and replaced by justice.

Bound states in the continuum in a two-dimensional PT - symmetric system

© 2018 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved.We address a 2D parity-time (¿¿)-symmetric structure built as a chain of waveguides, where all waveguides except for the central one are conservative, while the central one is divided into two halves with gain and losses. We show that such a system admits bound states in the continuum (BICs) whose properties vary drastically with the orientation of the line separating amplifying and absorbing domains, which sets the direction of internal energy flow. When the flow is perpendicular to the chain of the waveguides, narrow BICs emerge when the standard defect mode, which is initially located in the finite gap, collides with another mode in a standard symmetry breaking scenario, and its propagation constant enters the continuous spectrum upon increase of the strength of gain/losses. In contrast, when the energy flow is parallel to the chain of the waveguides, the symmetry gets broken even for a small strength of the gain/losses. In that case, the most rapidly growing mode emerges inside the continuous spectrum and realizes a weakly localized BIC. All BICs found here are the most rapidly growing modes; therefore, they can be excited from noisy inputs and, importantly, should dominate the beam dynamics in experiments.Peer Reviewe

Photonic snake states in two-dimensional frequency combs

Taming the instabilities inherent to many nonlinear optical phenomena is of paramount importance for modern photonics. In particular, the so-called snake instability is universally known to severely distort localized wave stripes, leading to the occurrence of transient, short-lived dynamical states that eventually decay. This phenomenon is ubiquitous in nonlinear science—from river meandering to superfluids—and so far it apparently remains uncontrollable; however, here we show that optical snake instabilities can be harnessed by a process that leads to the formation of stationary and robust two-dimensional zigzag states. We find that such a new type of nonlinear waves exists in the hyperbolic regime of cylindrical microresonators, and that it naturally corresponds to two-dimensional frequency combs featuring spectral heterogeneity and intrinsic synchronization. We uncover the conditions of the existence of such spatiotemporal photonic snakes and confirm their remarkable robustness against perturbations. Our findings represent a new paradigm for frequency comb generation, thus opening the door to a whole range of applications in communications, metrology and spectroscopy.Peer ReviewedPostprint (author's final draft

Reversible self-replication of spatiotemporal Kerr cavity patterns

We uncover a novel and robust phenomenon that causes the gradual self-replication of spatiotemporal Kerr cavity patterns in cylindrical microresonators. These patterns are inherently synchronized multifrequency combs. Under proper conditions, the axially localized nature of the patterns leads to a fundamental drift instability that induces transitions among patterns with a different number of rows. Self-replications, thus, result in the stepwise addition or removal of individual combs along the cylinder’s axis. Transitions occur in a fully reversible and, consequently, deterministic way. The phenomenon puts forward a novel paradigm for Kerr frequency comb formation and reveals important insights into the physics of multidimensional nonlinear patterns.Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

Bessel Vortex Filaments for Laser Material Processing

International audienceThe field of femtosecond beam shaping is undergoing rapid expansion for numerous applications since intense-light-matter interactions are used in both fundamental and applied science. Laser processing of transparent materials is currently an important technological topic, because transparent materials have an increasing number of applications in consumer electronics, microelectronics, photonic chips or next-generation displays. Single-shot machining by structured beams is attractive for such applications, but only void nanochannel fabrication has so far been demonstrated from Bessel beams [1]. The challenge in laser structuring of dielectrics is that the high intensities required (&gt1013W/cm2) are associated with strong spatio-temporal nonlinear distorsions of the laser pulses