4 research outputs found
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 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 21â12â00096). Also, support by CEX2019â000910âS [funded by MCIN/AEI/10.13039/501100011033], FundaciĂł Cellex, FundaciĂł MirâPuig, and Generalitat de Catalunya (CERCA) is acknowledged.Peer ReviewedPostprint (author's final draft
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 bacteriochlorinâstyrylnaphthalimide 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 BChlâNI 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 BChlâNI 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 BChlâNI. 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 BChlâNI 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 BChlâNI conjugate is a promissing dual function agent for cancer diagnostics and therapy