13 research outputs found
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 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 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 modes
residing at the edge or in the corner of the one- or two-dimensional arrays,
respectively, and demonstrate a new class of topological solitons
bifurcating from such modes in the topological gap of the Floquet spectrum at
high powers. 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 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
Effect of intense chirped pulses on the coherent phonon generation in Te
The authors have studied the influence of chirped laser pulses on the coherent phonon generation in single crystal Te. They have shown that the pulse chirp affects the amplitude of coherent phonons with A1 symmetry in the case of intense excitation only. By varying the chirp of an intense exciting pulse, the authors demonstrated that negatively chirped pulses are almost twice more effective in the creation of lattice coherence than positively chirped pulses
Effect of phase modulation of a laser pulse on the generation of a coherent totally symmetric phonon in a tellurium single crystal
The effect of phase modulation (resulting in a chirp of an ultrashort laser pulse) on the generation of a coherent A1 phonon in Te was studied. The amplitude of coherent oscillations was found to depend on the sign and value of the pulse chirp: the oscillation amplitude decreases as the chirp increases. For a positive chirp, this effect is twofold stronger than for a negative one. The frequency-resolved response of a bandwidth-limited pulse was studied, which revealed the difference of oscillations and the relaxation response for the Stokes and anti-Stokes frequencies. The detected phenomena can be used for coherent control of lattice dynamics
Intra-cluster dynamics induced in molecular clusters by femtosecond UV radiation
Dynamics of intra-cluster processes induced by femtosecond UV laser radiation in molecular clusters of CF3I and ICF2COF molecules is studied. The measured time constants of the observed reactions are within the range from 1 ps to dozens of picoseconds
Intra-cluster dynamics induced in molecular clusters by femtosecond UV radiation
Dynamics of intra-cluster processes induced by femtosecond UV laser radiation in molecular clusters of CF3I and ICF2COF molecules is studied. The measured time constants of the observed reactions are within the range from 1 ps to dozens of picoseconds
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
Split Hole Resonator: A Nanoscale UV Light Source
Because of strong light absorption
by metals, it is believed that plasmonic nanostructures cannot be
used for generating intensive radiation harmonics in the ultraviolet
(UV) spectral range. This work presents results of investigation of
nonlinear optical interaction with a single gold nanostructure, the
split-hole resonator (SHR) under the state-of-the-art experimentally
realized conditions. To realize interaction with all spectral components
of a 6 fs laser pulse several multipole plasmon resonances were simultaneously
excited in the SHR nanostructure. To the best of our knowledge, this
paper reports for the first time a strong nonlinear optical interaction
at the frequencies of these resonances that leads to (i) the second
harmonic generation, (ii) the third harmonic generation (THG), and
(iii) the light generation at mixed frequencies. The THG near field
amplitude reaches 0.6% of the fundamental frequency field amplitude,
which enables the creation of UV radiation sources with a record high
intensity. The UV THG may find many important applications including
biomedical ones (such as cancer therapy)
Fluorescence Lifetime and Intensity of Thioflavin T as Reporters of Different Fibrillation Stages: Insights Obtained from Fluorescence Up-Conversion and Particle Size Distribution Measurements
Thioflavin T (ThT) assay is extensively used for studying fibrillation kinetics in vitro. However, the differences in the time course of ThT fluorescence intensity and lifetime and other physical parameters of the system, such as particle size distribution, raise questions about the correct interpretation of the aggregation kinetics. In this work, we focused on the investigation of the mechanisms, which underlay the difference in sensitivity of ThT fluorescence intensity and lifetime to the formation of protein aggregates during fibrillation by the example of insulin and during binding to globular proteins. The assessment of aggregate sizes and heterogeneity was performed using dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA). Using the sub-nanosecond resolution measurements, it was shown that the ThT lifetime is sensitive to the appearance of as much as a few percent of ThT bound to the high-affinity sites that occur simultaneously with an abrupt increase of the average particle size, particles concentration, and size heterogeneity. The discrepancy between ThT fluorescence intensity and a lifetime can be explained as the consequence of a ThT molecule fraction with ultrafast decay and weak fluorescence. These ThT molecules can only be detected using time-resolved fluorescence measurements in the sub-picosecond time domain. The presence of a bound ThT subpopulation with similar photophysical properties was also demonstrated for globular proteins that were attributed to non-specifically bound ThT molecules with a non-rigid microenvironment