Observation of edge solitons in topological trimer arrays

We report the experimental observation of nonlinear light localization and edge soliton formation at the edges of fs-laser written trimer waveguide arrays, where transition from nontopological to topological phases is controlled by the spacing between neighboring trimers. We found that, in the former regime, edge solitons occur only above a considerable power threshold, whereas in the latter one they bifurcate from linear states. Edge solitons are observed in a broad power range where their propagation constant falls into one of the topological gaps of the system, while partial delocalization is observed when considerable nonlinearity drives the propagation constant into an allowed band, causing coupling with bulk modes. Our results provide direct experimental evidence of the coexistence and selective excitation in the same or in different topological gaps of two types of topological edge solitons with different internal structures, which can rarely be observed even in nontopological systems. This also constitutes the first experimental evidence of formation of topological solitons in a nonlinear system with more than one topological gap.The authors acknowledge funding of this study by RSF (grant 21‐12‐00096). Also, support by CEX2019‐000910‐S [funded by MCIN/AEI/10.13039/501100011033], Fundació Cellex, Fundació Mir‐Puig, and Generalitat de Catalunya (CERCA) is acknowledged.Peer ReviewedPostprint (author's final draft

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

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

La Olimpiada Pedagógica como herramienta para evaluar la calidad de la formación profesional de los estudiantes

Este artículo aborda el problema de la evaluación de la calidad de la formación profesional de los estudiantes que terminan los cursos de educación superior. Las autoras analizan las características esenciales del control y la evaluación de calidad del proceso educativo en una universidad, así como los criterios, las herramientas y los métodos de la evaluación de la calidad de la educación. Las autoras creen que la Olimpíada Pedagógica es una de las herramientas más eficientes para evaluar la calidad de la formación profesional. El artículo describe las prácticas en la evaluación de la calidad de la educación entre los estudiantes durante las Olimpiadas Estudiantiles en la etapa “All-Russian” de la Olimpiada Estudiantil Rusa (ARSO) en terapia del habla (Saransk, 2015), así como los aspectos de contenido y procedimiento para aplicar esta herramienta de evaluación; los resultados obtenidos a partir de esta evaluación nos permiten concluir que la calidad del desarrollo de la competencia profesional y la educación personal de los estudiantes se analizan cualitativa y cuantitativamente

Observation of rotation-induced light localization in waveguide arrays

We study both, experimentally and theoretically, propagation of light in the fs-laser written rotating square waveguide arrays and present the first experimental evidence of light localization induced by the rotation of periodic structure in the direction of light propagation. Such linear light localization occurs either in the corners of truncated square array, where it results from the interplay between the centrifugal effect and total internal reflection at the borders of truncated array, or in the center of array, where rotation creates effective attractive optical potential. The degree of localization of linear bulk and corner modes emerging due to the rotation increases with the increase of rotation frequency. Consequently, corner and bulk solitons in rotating wave-guide arrays become thresholdless for sufficiently large rotation frequencies, in contrast to solitons in non-rotating arrays that exist only above power threshold. Focusing nonlinearity enhances localization degree of corner modes, but surprising initially it leads to broadening of bulk nonlinear states, followed by their re-localization at high input powers. Our results open new prospects for control of evolution of nonlinear multidimensional excitations by dynamically varying potentials.Comment: 7 pages, 5 figures, to be appear on ACS Photonic

A novel bacteriochlorin–styrylnaphthalimide conjugate for simultaneous photodynamic therapy and fluorescence imaging

Propargyl-15 2 ,17 3-dimethoxy-13 1-amide of bacteriochlorin e (BChl) and a 4-(4-N,N-dimethylaminostyryl)-N-alkyl-1,8-naphthalimide bearing azide group in the N-alkyl fragment were conjugated by the copper(I)-catalyzed 1,3-dipolar cycloaddition to produce a novel dyad compound BChl–NI for anticancer photodynamic therapy (PDT) combining the modalities of a photosensitizer (PS) and a fluorescence imaging agent. A precise photo-physical investigation of the conjugate in solution using steady-state and time-resolved optical spectroscopy revealed that the presence of the naphthalimide (NI) fragment does not decrease the photosensitizing ability of the bacteriochlorin (BChl) core as compared with BChl; however, the fluorescence of naphthalimide is completely quenched due to resonance energy transfer (RET) to BChl. It has been shown that the BChl–NI conjugate penetrates into human lung adenocarcinoma A549 cells, and accumulates in the cytoplasm where it has a mixed granular-diffuse distribution. Both NI and BChl fluorescence in vitro provides registration of bright images showing perfectly intracellular distribution of BChl–NI. The ability of NI to emit light upon excitation in imaging experiments has been found to be due to hampering of RET as a result of photodestruction of the energy acceptor BChl unit. Phototoxicity studies have shown that the BChl–NI conjugate is not toxic for A549 cells at tested concentrations (o8 mM) without light-induced activation. At the same time, the concentration-dependent killing of cells is observed upon the excitation of the bacteriochlorin moiety with red light that occurs due to reactive oxygen species formation. The presented data demonstrate that the BChl–NI conjugate is a promissing dual function agent for cancer diagnostics and therapy