BUSCADOR RECOLECTA

Functionalization of metallic surfaces by molecular monolayers is a key process in fields such as nanophotonics or biotechnology. To strongly enhance light-matter interaction in such monolayers, nanoparticle-on-a-mirror (NPoM) cavities can be formed by placing metal nanoparticles on such chemically functionalized metallic monolayers. In this work, we present a novel functionalization process of gold surfaces using 5-amino-2-mercaptobenzimidazole (5-A-2MBI) molecules, which can be used for upconversion from THz to visible frequencies. The synthesized surfaces and NPoM cavities are characterized by Raman spectroscopy, atomic force microscopy (AFM), and advancing-receding contact angle measurements. Moreover, we show that NPoM cavities can be efficiently integrated on a silicon-based photonic chip performing pump injection and Raman-signal extraction via silicon nitride waveguides. Our results open the way for the use of 5-A-2MBI monolayers in different applications, showing that NPoM cavities can be effectively integrated with photonic waveguides, enabling on-chip enhanced Raman spectroscopy or detection of infrared and THz radiation., We acknowledge funding from the European Commission (THOR project, Grant Agreement No. 829067, and 'NextGenerationEU' /PRTR and 'ERDF A way of making Europe'), Generalitat Valenciana under grant CIPROM/2022/14, and the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) under project grant PID2021-124618NB-C21.

[EN] Optomechanical cavities can be used as highly sensitive mass sensors actuated by an optical field. In this work, we introduce and numerically demonstrate a new design for an optomechanical cavity consisting of a series of asymmetrically distributed rectangular silicon nanobricks, with each brick acting as an independent mechanical resonator but all coupled to the same optical field. Each silicon brick is placed on top of a thin silica pillar that ensures mechanical support whilst providing enough acoustic isolation between the individual mechanical resonances - at GHz frequencies - of each brick. The mass sensing capabilities of this cavity are studied through numerical simulations, proving that a point mass approximation can be used for silica nanoparticles with a radius smaller than 100 nm and that different nanoparticles can be measured independently but simultaneously and in real-time., HORIZON EUROPE Framework Programme (101091968 (MAGNIFIC)); Generalitat Valenciana (CIGE/
2023/126); Universitat Politècnica de València (PAID-06-22); Agencia Estatal de Investigación (PID2021-124618NB-C21
(ALLEGRO)).

[EN] Gallium Phosphide (GaP) has recently received considerable attention as a suitable material for building photonic integrated circuits due to its remarkable optical and piezoelectric properties. Usually, GaP is grown epitaxially on III-V substrates to keep its crystallinity and later transferred to silicon wafers for further processing. Here, an alternative promising route for the fabrication of optomechanical (OM) cavities on GaP epitaxially grown on nominally (001)-oriented Si is introduced by using a two-step process consisting of a low-temperature etching of GaP followed by selective etching of the underneath silicon. The low-temperature (-30 degrees C) during the dry-etching of GaP hinders the lateral etching rate, preserving the pattern with a deviation between the design and the pattern in the GaP layer lower than 5%, avoiding the complex process of transferring and bonding a GaP wafer to a silicon-on-insulator wafer. To demonstrate the quality and feasibility of the proposed fabrication route, suspended OM cavities are fabricated and experimentally characterized. The cavities exhibit optical quality factors between 103 and 104 at telecom wavelengths, and localized mechanical resonances approximate to 3.1 GHz with quality factors approximate to 63 when measured at room temperature. These results suggest a simple and low-cost way to build GaP-based photonic devices directly integrated on industry-standard Si(001) photonic wafers.; Here, optomechanical (OM) cavities on Gallium Phosphide (GaP) epitaxially grown on exact (001)-Si are fabricated following a novel two-step dry-etching process. The suspended OM cavities showed optical Q-factors up to 104 at telecom wavelengths, and mechanical resonances at approximate to 3.1 GHz at room temperature, suggesting a simple and low-cost way to build GaP-based photonic devices directly integrated on Si(001) photonic wafers. image, P.M. and L.M. contributed equally to this work. V.J.G., P.M, and R.R acknowledge financial support from the Generalitat Valenciana (Project: INVEST/2022/170). M.S.L. acknowledges financial support from the Generalitat Valenciana (Project: CIAPOS/2021/293). V.J.G. acknowledges financial support from the Generalitat Valenciana (CDEIGENT/2020/009), partial funding from the Conselleria de Educacion, Universidades y Empleo under the NIRVANA Grant (PROMETEO Program, CIPROM/2022/14), and to the AGENCIA ESTATAL DE INVESTIGACION of Ministerio de Ciencia, Innovacion y Universidades Grant CNS2023-145093 funded by MICIU/AEI/10.13039/501100011033 and by "European Union NextGenerationEU/PRTR". S.F.G. acknowledges the financial support received through the program Ramon y Cajal (co-financed by the European Social Fund) under Grant No. RYC-2016-19509. All authors acknowledge financial support from The AGENCIA ESTATAL DE INVESTIGACION of Ministerio de Ciencia e Innovacion (PID2020-118855RB-I00, PID2020-114280RB-I00, and PID2021-124618NB-C21) and to the European Regional Development Fund (ERDF) (IDIFEDER/2020/041, IDIFEDER/2021/061). This study formed part of the Quantum Communications program and was supported by Ministerio de Ciencia e Innovacion (MCIN) with funding from European Union NextGenerationEU (PRTR-C17.I1) and by Generalitat Valenciana (COMCUANTICA/003 and COMCUANTICA/004).

[EN] Functionalization of metallic surfaces by molecular
monolayers is a key process in fields such as nanophotonics or
biotechnology. To strongly enhance light¿matter interaction in
such monolayers, nanoparticle-on-a-mirror (NPoM) cavities can
be formed by placing metal nanoparticles on such chemically
functionalized metallic monolayers. In this work, we present a
novel functionalization process of gold surfaces using 5-amino-2-
mercaptobenzimidazole (5-A-2MBI) molecules, which can be used
for upconversion from THz to visible frequencies. The synthesized
surfaces and NPoM cavities are characterized by Raman spectroscopy, atomic force microscopy (AFM), and advancing¿receding
contact angle measurements. Moreover, we show that NPoM
cavities can be efficiently integrated on a silicon-based photonic
chip performing pump injection and Raman-signal extraction via silicon nitride waveguides. Our results open the way for the use of
5-A-2MBI monolayers in different applications, showing that NPoM cavities can be effectively integrated with photonic waveguides,
enabling on-chip enhanced Raman spectroscopy or detection of infrared and THz radiation., We acknowledge funding from the European Commission (THOR project, Grant Agreement No. 829067, and NextGenerationEU /PRTR and ERDF A way of making Europe ), Generalitat Valenciana under grant CIPROM/2022/14, and the Spanish Ministry of Science and Innovation
(MCIN/AEI/10.13039/501100011033) under project grant PID2021-124618NB-C21. E.P.-C gratefully acknowledges funding from Generalitat Valenciana (Grant No. SEJIGENT/2021/039), AGENCIA ESTATAL DE INVESTIGACIÓN of Ministerio de Ciencia e Innovacion (PID2021-128442NA-I00) and to the European Regional Development Fund (ERDF)
(IDIFEDER/2020/041, IDIFEDER/2021/061). J.E.V.-L. acknowledges support from Juan de la Cierva−Formación fellowship FJC2021-047776-I. M.S.L. acknowledges support
from the Generalitat Valenciana (Project: CIAPOS/2021/293) and AGENCIA ESTATAL DE INVESTIGACIÓN of Ministerio de Ciencia e Innovacion (PID2020-118855RB-I00). J.R. acknowledges funding from Universitat Politecnica ̀ de Valencia ̀ (Grant No. FPI 20-10253).

[EN] Vortices are topologically distinctive objects appearing as phase twists in coherent fields of optical beams and Bose-Einstein condensates. Structured networks and artificial lattices of coupled vortices could offer a powerful platform to study and simulate interaction mechanisms between constituents of condensed matter systems, such as antiferromagnetic interactions, by replacement of spin angular momentum with orbital angular momentum. Here, we realize such a platform using a macroscopic quantum fluid of light based on exciton-polariton condensates. We imprint all-optical hexagonal lattice that results into a triangular vortex lattice, with each cell having a vortex of charge l = +/- 1. We reveal that pairs of coupled condensates spontaneously arrange their orbital angular momentum antiparallel, implying a form of artificial orbital "antiferromagnetism." We discover that correlation exists between the emergent vortex patterns in triangular condensate lattices and the low-energy solutions of the corresponding antiferromagnetic Ising system. Our study offers a path toward spontaneously ordered vortex arrays with nearly arbitrary configurations and controlled couplings., This work was supported by Russian Science Foundation (RSF) grant no. 21- 72- 00088. H.S. acknowledges Icelandic Research Fund (Rannis) grant no. 239552- 051. C.M. acknowledges support from the Spanish government via grant PID2021- 124618NB- C21 by MCIN/AEI/10.13039/501100011033 and "ERDF: a way of making Europe" of the European Union and the Generalitat Valenciana PROMETEO/2021/082. Y.V.K. acknowledges funding by the research project FFUU- 2024- 0003 of the Institute of Spectroscopy of the Russian Academy of Sciences.

[EN] Optomechanical crystal cavities (OMCCs) allow the
interaction between localized optical and mechanical modes
through the radiation-pressure force. Driving such cavities with
blue-detuned lasers relative to the optical resonance can induce
a phonon lasing regime where the OMCC supports self-sustained
mechanical oscillations. This dynamic state results in a narrow and
stable microwave tone that modulates the laser at integer multiples of the mechanical resonance frequency, creating an optomechanical (OM) frequency comb suitable for microwave photonics applications. OMCCs enable compact, low-cost power-efficient
all-photonic processing of multiple microwave signals, crucial for
current and future beyond-5G systems, whilst being compatible
with silicon integrated photonic circuits. This work reports the
demonstration of all-optical up- and down-conversion of 3GPP 5G
new-radio (NR) signals from the low- to mid- and extended-mid
bands using the first and second harmonics of the frequency comb
generated in a silicon OMCC. The OM comb generates up to 6
harmonics in the K-band, which is suitable for microwave photonic
applications. The experimental demonstration also evaluates the
impact of the phase-noise and the signal-to-noise ratio (SNR) in
the frequency-converted 5G NR signals when the first and second
OMCC harmonics are employed for frequency conversion., The work of Vicente Fito and Raul Ortiz were supported under Grant PAID-01-20 UPV and Grant GVACIACIF/2021/006. This work was supported in part by Generalitat Valenciana CIAICO/2021/201 TERAFLEX Project under Grant IDIFEDER/2021/061, in part by Spanish Ministry of Science and Innovation ALLEGRO under Grant PID2021-124618NB-C21, in part by SLOMO under Grant PDC2022-133267-C21, in part by MUSICIAN (CHISTERA IV Cofund 2021), and in part by the European Commission through MAGNIFIC under Grant HORIZON-CL4-2022-RESILIENCE-01-10 101091968.

[EN] Locking of oscillators to ultra-stable external sources is of paramount importance for improving close-to-carrier phase noise in free running oscillators. In most of them, such as Micro-Electro-Mechanical-Systems or LC circuit-based oscillators, the locking frequency range is limited by the robustness of their natural frequency, which comes explicitly related with intrinsic parameters of the system. In this work we report the synchronization of an optically-driven self-pulsing limit-cycle taking place in a silicon optomechanical crystal cavity to an external harmonic signal that modulates the driving laser. Because of the extreme ductility of the natural self-pulsing frequency (several tens of MHz), the injection-locking mechanism is highly efficient and displays giant relative bandwidths exceeding 60%. The external modulation reveals itself as a knob to explore dynamical attractors that are otherwise elusive and, in particular, as a means to initialize a mechanical resonator into a state of self-sustained oscillations driven by radiation pressure forces. Moreover, we exploit the large anharmonicity of the studied limit-cycle to induce injection-locking to integer multiples and fractions of the frequency of the external reference, which can be used for frequency conversion purposes in nano-electro-opto-mechanical systems., This work was supported by the MICINN project ALLEGRO (PID2021-124618NB-C21 and PID2021-124618NB-C22).

[EN] Optomechanical (OM) cavities simultaneously localize photons and phonons, thus enhancing their mutual interaction through radiation-pressure force. This acousto-optic interaction can be quantified by means of the optical-frequency shift per mechanical displacement
G
. The aforesaid frequency shift can also be related to the vacuum OM coupling rate
g
0
, where only photoelastic and moving-boundary effects are commonly taken into account. However, the thermo-optic and thermal-expansion effects may also play a role since the material forming the OM cavity could be heated by the presence of photons, which should naturally affect the mechanical properties of the cavity. In this work, we introduce a theoretical approach to determine how thermal effects change the canonical OM coupling rate. To test the model, a complete set of optical-thermal-mechanical simulations was performed in two OM crystal cavities fabricated from two different materials: silicon and diamond. Our results lead us to conclude that there is a non-negligible thermal correction that is always present as a negative shift to the OM coupling rate that should be considered in order to predict more accurately the strength of the OM interaction., The authors thank J. Maire, N. Capuj, C. Milian,
and E. Verhagen for useful discussions. The authors
acknowledge funding from Generalitat Valenciana
(GVA, CIACIF/2021/006), the European Union
( NextGenerationEU /PRTR and ERDF A way of making
Europe ), and the Spanish Ministry of Science and Innovation
(MCIN/AEI/10.13039/501100011033) under project
Grants No. PID2021-124618NB-C21 (ALLEGRO) and
No. PCI2022-135003-2 (MUSICIAN).

[EN] Optomechanical oscillators stand out as high-performance and versatile candidates for serving as reference clocks in sequential photonic integrated circuits. Indeed, they have the unique capability of simultaneously generating mechanical tones and optical signal modulations at frequencies determined by their geometrical design. In this context, the concept of synchronization introduces a powerful means to precisely coordinate the dynamics of multiple oscillators in a controlled manner, therefore increasing efficiency and preventing errors in signal processing photonic systems or communication interfaces. In this work, we demonstrate the cascaded injection locking of a pair of silicon-based optomechanical crystal cavities acting as optomechanical oscillators to an external reference signal that subtly modulates the laser driving only one of them. In contrast to most previous implementations, both cavities support isolated optical resonances and interact by a weak mechanical interconnection. This configuration allows one cavity to be used for probing the mechanical perturbation generated by the oscillator that receives the external forcing. The combination of the obtained results, supported by a numerical model, with remote optical injection locking schemes discussed in the literature lays the groundwork for the distribution of reference signals within large networks of processing elements in future phonon¿photon hybrid circuits., This work was supported by the MICINN projects ALLEGRO (Grants Nos. PID2021-124618NB-C22 and PID2021-124618NB-C21) and MOCCASIN-2D (Grant No. TED2021-132040B-C21). D.A.-T. acknowledges the financial support of the Generalitat de Catalunya through Grant No. AGAUR FI-SDUR 2023.

[EN] Bimodal interferometry can be implemented in a photonic
integrated waveguide by inserting structures supporting¿at
least¿two modes to connect an input and an output singlemode waveguide. The length of the bimodal section is
inversely proportional to the index difference between the
involved modes, which can be quite small in multimode
dielectric waveguides. We propose and numerically demonstrate an ultrashort bimodal interferometer by embedding
a multilayer hyperbolic metamaterial in a subwavelength
gap separating two dielectric waveguides. We use the large
index difference (>1.5) between the bulk and the plasmonicguided modes of the metamaterial to reduce the total length
of the interferometer to less than 1 µm. Our system, which is
potentially fabricable with standard nanofabrication tools,
could be used to build ultra-compact integrated bimodal
interferometers for signal processing and biosensing., Agencia Estatal de Investigación (PID2021-124618NB-C21);
Universitat Politècnica de València (PAID-01-2023); Generalitat Valenciana
(CIBEST/2023/252, CIPROM/2022/14).

[EN] We study the accuracy of machine learning methods for inferring the parameters of noisy
fractional Wu¿Baleanu trajectories with some missing initial terms. Our model is based on
a combination of convolutional and recurrent neural networks (LSTM), which permits the
extraction of characteristics from trajectories while preserving time dependency. We show that
these approach exhibit good accuracy results despite the poor quality of the data., JAC acknowledges funding from the Spanish Ministry of Science and Innovation (MICINN), grant PID2021-124618NB-C21 funded
by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe , by the European Union .
CL is partially funded by Agencia Nacional para la Innovación y del Desarrollo (ANID), under FONDECYT grant number 1220036.
We also acknowledge funding for open access charge: CRUE-Universitat Politècnica de València.

[EN] 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 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 toward the observation of dissipative light bullets and three-dimensional breathers., This work was supported by European Research Council (740355) , Marie Sklodowska-Curie Actions (101064614, 101023717) , Ministero dell'Istruzione, dell'Universita e della Ricerca (R18SPB8227) . C. M. acknowledges support from PROMETEO/2021/082 and from the Spanish government via the Grant PID2021-124618NB-C21 funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe". Y. V. K. is supported by the research Project No. FFUU-2021-0003 of the Institute of Spectroscopy of the Russian Academy of Sciences.

[EN] We infer the parameters of fractional discrete Wu Baleanu time series by using machine learning architectures based on recurrent neural networks. Our results shed light on howclearly one can determine that a given trajectory comes from a specific fractional discrete dynamical system by estimating the fractional exponent and the growth parameter mu. With this example, we also show how machine learning methods can be incorporated into the study of fractional dynamical systems., JAC acknowledges funding from grant PID2021-124618NB-C21 funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe," by the "European Union." We also thank funding for the open-access charges from CRUE-Universitat Politecnica de Valencia.CL was partially supported by ANID under FONDECYT Grant Number 1220036.

[EN] Optomechanical crystal cavities (OMCCs) are fundamental nanostructures for a wide range of phenomena and applications. Usually, optomechanical interaction in such OMCCs is limited to a single optical mode and a unique mechanical mode. In this sense, eliminating the single-mode constraint¿for instance, by adding more mechanical modes¿should enable more complex physical phenomena, giving rise to a context of multimode optomechanical interaction. However, a general method to produce in a controlled way multiple mechanical modes with large coupling rates in OMCCs is still missing. In this work, we present a route to confine multiple GHz mechanical modes coupled to the same optical field with similar optomechanical coupling rates¿up to 400 kHz¿by OMCC engineering. In essence, we increase the number of unit cells (consisting of a silicon nanobrick perforated by circular holes with corrugations at both its sides) in the adiabatic transition between the cavity center and the mirror region. Remarkably, the mechanical modes in our cavities are located within a full phononic band gap, which is a key requirement to achieve ultrahigh mechanical
Q factors at cryogenic temperatures. The multimode behavior in a full phononic band gap and the easiness of realization using standard silicon nanotechnology make our OMCCs highly appealing for applications in the classical and quantum realms., The authors acknowledge funding from the Spanish State Research Agency (Grants No. PID2021- 124618NB-C21 and No. PID2021-124618NB-C22) ; Generalitat Valenciana (Grants No. BEST/2020/178, No. PROMETEO/2019/123, No. IDIFEDER/2020/041, and No. IDIFEDER/2021/061). L.M. is grateful for financial support from the Next Generation EU program, Ministerio de Universidades (Gobierno de Espana).

[EN] We show how machine learning methods can unveil the fractional and delayed nature of discrete dynamical systems. In particular, we study the case of the fractional delayed logistic map. We show that given a trajectory, we can detect if it has some delay effect or not and also to characterize the fractional component of the underlying generation model., Ministerio de Ciencia e Innovacion-Agencia Estatal de Investigacion, Grant/Award Number: PID2021-124618NB-C21; European Union

[EN] Algorithms that use tensors are increasingly important due to the goodness of this operation when performing calculations with large amounts of data. Among them, we find the algorithms that search for the solution of a linear system in separated form, where the Greedy Rank-One Update method stands out, the starting point of the famous PGD family (from its acronym, Proper Generalized Decomposition).

When the matrices of these systems have the particular structure of a Laplacian-type matrix, the convergence of the previous methods is faster and more accurate. The Laplacian Decomposition Algorithm calculates the Laplacian matrix that best approximates a given square matrix. When the residue of this approximation is small, we will be able to solve the linear system associated with a Laplacian-type matrix and thus obtain an approximation of the solution of the original system, with a lower computational cost.

In this paper we prove that the discretization of a general Partial Differential Equation of the second order can be written as a linear system with a Laplacian-type matrix., J. A. Conejero acknowledges funding from grant PID2021-124618NB-C21, funded by MCIN/AEI/ 10.13039/501100011033, and by ERDF: A way of making Europe , by the European Union ; M. Mora-Jimenez was supported by the Generalitat Valenciana and the European Social ¿ Fund under grant number ACIF/2020/269; A. Falco was supported by the MICIN grant number ¿
RTI2018-093521-B-C32 and Universidad CEU Cardenal Herrera under grant number INDI22/15

[EN] Extended connectivity in graphs can be analyzed through k-path Laplacian matrices, which permit the capture of long-range interactions in various real-world networked systems such as social, transportation, and multi-agent networks. In this work, we present several alternative methods based on machine learning methods (LSTM, xLSTM, Transformer, XGBoost, and ConvLSTM) to predict the final consensus value based on directed networks (Erd & ouml;s-Renyi, Watts-Strogatz, and Barab & aacute;si-Albert) and on the initial state. We highlight how different k-hop interactions affect the performance of the tested methods. This framework opens new avenues for analyzing multi-scale diffusion processes in large-scale, complex networks., This research was funded by the European Union - NextGenerationEU, ANDHI project CPP2021-008994 and PID2021-124618NB-C21, by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe", from the European Union.

[EN] We present a method to study the dynamics of a quasi-two dimensional Bose-Einstein condensate which initially contains several vortices at arbitrary locations. The method allows one to find the analytical solution for the dynamics of the Bose-Einstein condensate in a homogeneous medium and in a parabolic trap, for the ideal non-interacting case. Secondly, the method allows one to obtain algebraic equations for the trajectories of the position of phase singularities present in the initial condensate along with time (the vortex lines). With these equations, one can predict quantities of interest, such as the time at which a vortex and an antivortex contained in the initial condensate will merge. For the homogeneous case, this method was introduced in the context of photonics. Here, we adapt it to the context of Bose-Einstein condensates, and we extend it to the trapped case for the first time. Also, we offer numerical simulations in the non-linear case, for repulsive and attractive interactions. We use a numerical split-step simulation of the non-linear Gross-Pitaevskii equation to determine how these trajectories and quantities of interest are changed by the interactions. We illustrate the method with several simple cases of interest, both in the homogeneous and parabolically trapped systems., M.A.G.-M. acknowledges funding from the Spanish Ministry of Education and Professional Training (MEFP) through the Beatriz Galindo program 2018 (BEAGAL18/00203), Spanish Ministry MINECO (FIDEUA PID2019-106901GBI00/10.13039/501100011033), QuantERA II Cofund 2021 PCI2022-133004, Project of MCIN with funding from European Union NextGenerationEU (PRTR-C17.I1) and by Generalitat Valenciana, with Ref. 20220883 (PerovsQuTe). P.F.D.C. acknowledges the grant PID2021-128676OB-I00 funded by FEDER/MCIN. J.A.C. acknowledges funding from the Spanish Ministry of Science and Innovation (MICINN), grant PID2021-124618NB-C21. A.F. thanks the support of MCIN of Spain through the Project No. PID2020-120484RB-I00 and Generalitat Valenciana, Spain (Grant No. PROMETEO/2021/082).

[EN] 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., J.A.C. and C.M. acknowledge support from the Spanish government via grant PID2021-124618NB-C21, which was funded by MCIN/AEI/10.13039/501100011033 and ERDF: a way of making Europe' of the European Union. C.M. acknowledges support from Generalitat Valenciana PROMETEO/2021/082. P.F.d.C. acknowledges partial support from the Spanish government via project PID2021-128676OB-I00 (MICINN). L.T. acknowledges support by CEX2019-000910-S (MCIN/AEI/10.13039/501100011033), F. Cellex, F. M. Puig and Generalitat de Catalunya (CERCA). Y.V.K.'s academic research has been supported by the research project FFUU-2021-0003 of the Institute of Spectroscopy of the Russian Academy of Sciences.

[EN] Anomalous diffusion is present at all scales, from atomic to large ones. Some exemplary systems are ultracold atoms, telomeres in the nucleus of cells, moisture transport in cement-based materials, arthropods' free movement, and birds' migration patterns. The characterization of the diffusion gives critical information about the dynamics of these systems and provides an interdisciplinary framework with which to study diffusive transport. Thus, the problem of identifying underlying diffusive regimes and inferring the anomalous diffu-sion exponent alpha with high confidence is critical to physics, chemistry, biology, and ecology. Classification and analysis of raw trajectories combining machine learning techniques with statistics extracted from them have widely been studied in the Anomalous Diffusion Challenge [Munoz-Gil et al. , Nat. Commun. 12 , 6253 (2021)]. Here we present a new data-driven method for working with diffusive trajectories. This method utilizes Gramian angular fields (GAF) to encode one-dimensional trajectories as images (Gramian matrices), while preserving their spatiotemporal structure for input to computer-vision models. This allows us to leverage two well-established pretrained computer-vision models, ResNet and MobileNet, to characterize the underlying diffusive regime and infer the anomalous diffusion exponent alpha. Short raw trajectories of lengths between 10 and 50 are commonly encountered in single-particle tracking experiments and are the most difficult ones to characterize. We show that GAF images can outperform the current state-of-the-art while increasing accessibility to machine learning methods in an applied setting., We thank M. A. Garcia-March for helpful comments and discussions on the topic. N.F. is supported by the National University of Singapore through the Singapore International Graduate Student Award (SINGA) program. O.G.O. and L.S. also acknolwedges support from European Comission, project EU ICT-48 2020 project TAILOR (No. 952215) funding from MINECO project, Grant No. TIN2017-88476-C2-1-R. J.A.C. acknowledges funding from Grant No. PID2021-124618NB-C21 funded by MCIN/AEI/10.13039/501100011033 and by "ERDF A way of making Europe," by the "European Union."

[EN] We unveil a new scenario for the formation of dissipative localized structures in nonlinear systems. Commonly, the formation of such structures arises from the connection of a homogeneous steady state with either another homogeneous solution or a pattern. Both scenarios, typically found in cavities with normal and anomalous dispersion, respectively, exhibit unique fingerprints and particular features that characterize their behavior. However, we show that the introduction of a periodic non-Hermitian modulation in Kerr cavities hybridizes the two established soliton formation mechanisms, embodying the particular fingerprints of both. In the resulting novel scenario, the stationary states acquire a dual behavior, playing the role that was unambiguously attributed to either homogeneous states or patterns. These fundamental findings have profound practical implications for frequency comb generation, introducing unprecedented reversible mechanisms for real-time manipulation., This work was supported by the Spanish government via PID2022-138321NB-C21 and Generalitat de Catalunya via 2021 SGR 00606; C. M. acknowledges PID2021-124618NB-C21, funded by MCIN/AEI/10.13039/501100011033 and " ERDF: a way of making Europe " of the European Union, and Generalitat Valenciana via PROMETEO/2021/082.

We show that the introduction of non-Hermitian modulations in a Kerr optical ring cavity induces a hybridisation of the two known formation mechanisms of solitonic solutions. This blends the properties of anomalous and normal dispersion regimes and allows the stabilisation of new families of frequency combs associated to stable solitons, molecules and patterns. The resultant new scenario greatly diversifies the possible generated frequency combs in Kerr cavities and can wide the application range of frequency combs., This work was supported by the Spanish government via PID2022-138321NB-C21 and Generalitat de Catalunya via 2021 SGR 00606; C.M. acknowledges PID2021-124618NB-C21, funded by MCIN/ AEI/10.13039/501100011033 and ‘ERDF: a way of making Europe’ of the European Union, and Generalitat Valenciana via PROMETEO/2021/082.