Observation of linear and nonlinear light localization at the edges of moiré arrays

We observe linear and nonlinear light localization at the edges and in the corners of truncated moiré arrays created by the superposition of periodic mutually twisted at Pythagorean angles square sublattices. Experimentally exciting corner linear modes in the femtosecond-laser written moiré arrays we find drastic differences in their localization properties in comparison with the bulk excitations. We also address the impact of nonlinearity on the corner and bulk modes and experimentally observe the crossover from linear quasilocalized states to the surface solitons emerging at the higher input powers. Our results constitute the first experimental demonstration of localization phenomena induced by truncation of periodic moiré structures in photonic systems.This research is funded by the research Project No. FFUU- 2021-0003 of the Institute of Spectroscopy of the Russian Academy of Sciences and partially funded by the RSF Grant No. 21-12-00096. F. Y. acknowledges support from Shanghai Outstanding Academic Leaders Plan (Grant No. 20XD1402000) and the NSFC (Grant No. 91950120). S. K. I. and L. T. acknowledge support by Grants No. CEX2019-000910-S and No. PGC2018-097035-B-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER, Fundació Cellex, Fundació Mir-Puig, and Generalitat de Catalunya (CERCA).Peer ReviewedPostprint (published version

Observation of π\pi solitons in oscillating waveguide arrays

Floquet systems with periodically varying in time parameters enable realization of unconventional topological phases that do not exist in static systems with constant parameters and that are frequently accompanied by appearance of novel types of the topological states. Among such Floquet systems are the Su-Schrieffer-Heeger lattices with periodically-modulated couplings that can support at their edges anomalous $\pi$ modes of topological origin despite the fact that the lattice spends only half of the evolution period in topologically nontrivial phase, while during other half-period it is topologically trivial. Here, using Su-Schrieffer-Heeger arrays composed from periodically oscillating waveguides inscribed in transparent nonlinear optical medium, we report experimental observation of photonic anomalous $\pi$ modes residing at the edge or in the corner of the one- or two-dimensional arrays, respectively, and demonstrate a new class of topological $\pi$ solitons bifurcating from such modes in the topological gap of the Floquet spectrum at high powers. $\pi$ solitons reported here are strongly oscillating nonlinear Floquet states exactly reproducing their profiles after each longitudinal period of the structure. They can be dynamically stable in both one- and two-dimensional oscillating waveguide arrays, the latter ones representing the first realization of the Floquet photonic higher-order topological insulator, while localization properties of such $\pi$ solitons are determined by their power.Comment: 10 pages, 6 figures, to appear in Science Bulleti

Self-reconstruction of single-cycle light bullet in linear (free-space) propagation regime

The results of investigation of extremely compressed wave packets penetration of air gap under single femtosecond laser pulse filamentation in LiF at anomalous group velocity dispersion are presented. It is revealed by laser coloration method that a single cycle light bullet formed before the gap up to 0.5 mm was recovered after passing some distance behind the gap which increased nonlinearly with the gap length

Self-reconstruction of single-cycle light bullet in linear (free-space) propagation regime

The results of investigation of extremely compressed wave packets penetration of air gap under single femtosecond laser pulse filamentation in LiF at anomalous group velocity dispersion are presented. It is revealed by laser coloration method that a single cycle light bullet formed before the gap up to 0.5 mm was recovered after passing some distance behind the gap which increased nonlinearly with the gap length

Light bullets in transparent dielectrics

The state of research of the light bullets (LB) formation in the process of femtosecond laser pulse filamentation is presented. LB is a near single-cycle wave packet that is formed in the result of the light field self-organization in a nonlinear dispersive medium under matched spatiotemporal radiation self-compression in the regime of anomalous group-velocity dispersion (GVD). The formation of each LB is accompanied by the generation of a discrete portion of supercontinuum (SC) in the anti-Stokes region. LB is a short-lived robust object with parameters determined by fundamental properties of the medium and the laser pulse central wavelength

Light bullets in transparent dielectrics

The state of research of the light bullets (LB) formation in the process of femtosecond laser pulse filamentation is presented. LB is a near single-cycle wave packet that is formed in the result of the light field self-organization in a nonlinear dispersive medium under matched spatiotemporal radiation self-compression in the regime of anomalous group-velocity dispersion (GVD). The formation of each LB is accompanied by the generation of a discrete portion of supercontinuum (SC) in the anti-Stokes region. LB is a short-lived robust object with parameters determined by fundamental properties of the medium and the laser pulse central wavelength

Direct measuring of single-cycle mid-IR light bullets path length in LiF by the laser coloration method

A colour-centre structure formed in a LiF crystal under filamentation of a femtosecond mid-IR laser pulse with a power slightly exceeding the critical power for self-focusing has been experimentally and theoretically investigated. A single-cycle light bullet was recorded for the first time by observation of strictly periodic oscillations for the density of the color centers induced in an isotropic LiF crystal under filamentation of a laser beam with a wavelength tuned in the range from 2600 to 3900 nm, which is due to the periodic change in the light field amplitude in the light bullet formed under filamentation under propagation in dispersive medium. The light bullet path length was not more than one millimeter

Recent selection of candidate genes for mammal domestication in Europeans and language change in Europe: a hypothesis

Background and aim: Human evolution resulted from changes in our biology, behaviour, and culture. One source of these changes has been hypothesised to be our self-domestication (that is, the development in humans of features commonly found in domesticated strains of mammals, seemingly as a result of selection for reduced aggression). Signals of domestication, notably brain size reduction, have increased in recent times. Methods: In this paper, we compare whole-genome data between the Late Neolithic/Bronze Age individuals and modern Europeans. Results: We show that genes associated with mammal domestication and with neural crest development and function are significantly differently enriched in nonsynonymous single nucleotide polymorphisms between these two groups. Conclusion: We hypothesise that these changes might account for the increased features of self-domestication in modern humans and, ultimately, for subtle recent changes in human cognition and behaviour, including language. Keywords: Late Neolithic/Bronze Age; Self-domestication; language change; nonsynonymous SNPs