arXiv subjects

Nilo Mata-Cervera

Publications and source records attributed to Nilo Mata-Cervera.

15 recordsLinked to original sources

arXiv2026

Recovering topological information of light by topological learning

The evolution of modern-day communication networks towards optical solutions with enhanced capacity and robustness is driving interest in topological light waves, exploiting their stability against perturbations through a topological invariant, e.g., the skyrmion number. However, detecting the underlying topology remains a computationally intense process even under ideal conditions, becoming intractable after passing through strongly disordered channels, where the degradation into unrecognisable speckle appears to destroy the topology. Here, we propose and demonstrate a topology-enhanced artificial intelligence (AI) approach to recover and classify such apparently lost topological information by computationally leveraging topological invariants in the data across many length scales. By aligning the topological classification of information with the topology of light, our topology-enhanced learning protocol, termed TOPO$^{2}$, achieves highly efficient recognition of the topological states of light, even from speckle, without the need for any prior learning. Our approach outperforms benchmark tests against standard computational algorithms and has the benefit of requiring just a single intensity pattern as the input, facilitating single-shot operation. To demonstrate this, we leverage the skyrmion number as a robust data carrier of images through a disordered channel, using TOPO$^{2}$ to accurately reconstruct the transmitted images. This work synergises topological photonics and topological AI for unravelling hidden topological signatures in light, opening a pathway towards robust communications even in extreme disordered environments.

physics.optics↗

arXiv2026

High-speed electrically driven liquid-crystal compact optical skyrmion encoder

Optical skyrmions possess topological polarization textures that can maintain topological robustness under external perturbations, making them promising carriers for disturbance-resistant optical information transmission. However, existing optical skyrmion generation schemes mostly rely on static optical elements or fixed nanostructures, making high-speed dynamic switching of the topological state difficult. Here, we propose a high-speed switchable optical skyrmion generator based on a patterned liquid-crystal spin-orbit device. The device employs the in-plane orientation of liquid crystals to imprint a fixed Pancharatnam-Berry geometric phase, while an applied voltage rapidly tunes the liquid-crystal retardance, enabling reversible switching between skyrmion and non-skyrmion states. Experimental results show that the device exhibits millisecond electrical response, with bidirectional response times of 1.76 ms and 0.72 ms, corresponding to an ideal cycling rate of approximately 403 Hz, making it the fastest switchable optical skyrmion generator to date. Furthermore, by exploiting this rapid topological refreshing capability, we demonstrate image encoding and decoding, providing a new liquid-crystal device platform for high-speed, refreshable, and disturbance-resistant topological optical information transmission.

physics.optics↗

arXiv2026

Non-diffracting meronic spin defects of light

Optical vortices are singularity lines where the light field intensity vanishes and its phase is undefined. These threads of darkness are adorned by Gauss's law as lines of pure longitudinal polarization where the polarization plane tilts and winds around. We unveil the resulting spin field as a unique structure which unifies both topological textures and defects, as it includes a point defect of undefined spin surrounded by a meronic texture which spans half the spin unit sphere. Moreover, this intricate topological structure of transverse spin does not spread in propagation, is localized arbitrarily below the wavelength of light and presents highly anisotropic features. Here we describe these hidden topologies of transverse spin embedded in simple scalar vortex beams, highlighting the diversity of topological structures that arise in two different spaces -- the spin unit sphere and the transverse-axial Poincar\'e sphere -- and discuss the underlying aspects behind their subwavelength localization.

physics.optics↗

arXiv2026

Unfolding unstable skyrmionic polarization textures

Polarization of light can form skyrmionic textures, akin to nonlinear solitons in condensed matter, yet their disparate physical context has motivated extensive debate regarding their stability. Here we show that the topological charge of such structures (skyrmion number) changes when an arbitrarily small perturbation splits coalescent phase singularities. In a superposition of two vortex beams, the skyrmion number generally only depends on the higher order topological charge $\lrr{Q_{\rm sk}=\max\lr{\ell_2,\ell_1}}$ rather than the difference of charges of the vortices in superposition $\lrr{Q_{\rm sk}=\ell_2-\ell_1}$, which only holds in the absence of perturbation. These results have significant implications for polarization structures with wavelength-scale localization and those experiencing complex aberrations.

physics.optics↗

arXiv2026

High-performance Sources of Multidimensionally Engineered Quantum Light Based on Monolithic Microcavity-metalens Interfaces

The ultimate non-classic light sources for modern photonic quantum technology require on-demand generation of indistinguishable quantum light with high brightness and flexible engineering of quantum emission in multiple degrees of freedom. In this work, we present monolithic microcavity-metalens interfaces consisting of quantum-dot-micropillar single-photon sources and ultra-thin metalenses accurately aligned on opposite sides of an III-V compound semiconductor chip. The pronounced cavity quantum electrodynamics effect enabled by the micropillar cavity facilitates single-photon emission from quantum dots with simultaneous high degrees of single-photon purity, source brightness and photon indistinguishability while the multi-functional metalenses concurrently tailor quantum emission in multiple physical degrees of freedom including radiation divergence, emission directionality, polarization state and orbital angular momentum (OAM). Furthermore, high-fidelity polarization-OAM entanglement and single photons with local spin topologies are successfully generated in our integrated device. In particular, we demonstrate stable propagations of single-photon skrymions in atmospheric turbulence and reveal their topological advantages over the conventional structured quantum light. Our work advances the research fields of integrated quantum photonics and meta-optics, providing integrated high-dimensional quantum light sources for advanced photonic quantum science and technology.

physics.optics↗

arXiv2026

Gouy phase-assisted Zeno effect for protecting light structure in random media

Identifying physical mechanisms that protect the information carried by various forms of structured light is one of the cornerstones of today's classical and quantum communications. Here we show that the purity of orbital angular momentum (OAM) modes can be protected against degradation in random media by leveraging two fundamental features of their own Schr\"odinger Hamiltonian dynamics, namely, Zeno effect -- frequent observations slow down the evolution -- , and Gouy phase -- the back-action of the observation. Repeated, OAM-dependent Gouy phase kicks imparted along the disturbing path by simple imaging systems trigger the optical Zeno effect that protects the input OAM mode against mode cross-talk that would broaden the OAM spectrum. Given the universality of the mechanism, the Gouy phase-assisted Zeno effect would protect propagation modes other than those of OAM, and the diverse forms of structured light built with them.

physics.optics↗

arXiv2025

Topology-guided vortices in a polariton condensate

A major challenge in polariton fluids is achieving deterministic control over the spin texture of the macroscopic condensate wavefunction, which dictates the nucleation and dynamics of topological excitations, such as vortices, solitons, and strings. Existing approaches typically rely on external gauge fields to indirectly access the polariton pseudospin, resulting in configurations that are weakly constrained by the cavity modes and therefore highly sensitive to disorder and fluctuations. Here, we report the generation of spin polaritons constrained to the topology of a bound state in the continuum (BIC) metasurface with broken inversion symmetry carved into a polycrystalline halide-perovskite film. Geometry-induced polariton condensation under spin-momentum locking gives rise to a pair of half-vortices of opposite spin, intrinsically pinned to polarization strings, emerging as topological extensions of the vortex cores. Consequently, varying the excitation density drives a controlled displacement of the half-vortices along the trajectories imposed by the strings, hindering their mutual annihilation across an interposed topological domain wall. This approach establishes cavity geometry as an intrinsic source of spin textures to guide vortex displacement in driven quantum fluids, opening a route toward the generation of robust topological excitations within structurally disordered materials.

physics.app-ph↗

arXiv2025

Diffraction-free natural optical skyrmions and their subwavelength confinement around vortices

Diffraction causes waves to spread out as they propagate freely. The tighter the lateral confinement, the faster the spreading. Past research on how to suppress diffraction has been based on wave engineering and has led so far to idealized waves that, in real settings, eventually diffract. Here, we find a propagating light wave structure naturally present in optical vortices, a natural skyrmion, that is exempt from diffraction. Moreover, diffraction-free propagation occurs with lateral confinement at any scale below the wavelength of light. In our experiments, we observe non-diffraction over a propagation distance above three orders of magnitude greater than expected from the skyrmion subwavelength size. We thus provide a factual, real-world form of ideal non-diffracting propagation. This form substantially differs from previous forms of light propagation, including propagating optical skyrmions known to date, and could open up new perspectives in its various applications.

physics.optics↗

arXiv2025

Topological robustness of classical and quantum optical skyrmions in atmospheric turbulence

The degradation of classical and quantum structured light induced by complex media constitutes a critical barrier to its practical implementation in a range of applications, from communication and energy transport to imaging and sensing. Atmospheric turbulence is an exemplary case due to its complex phase structure and dynamic variations, driving the need to find invariances in light. Here we construct classical and quantum optical skyrmions and pass them through experimentally simulated atmospheric turbulence, revealing the embedded topological resilience of their structure. In the quantum realm, we show that while skyrmions undergo diminished entanglement, their topological characteristics maintain stable. This is paralleled classically, where the vectorial structure is scrambled by the medium yet the skyrmion remains stable by virtue of its intrinsic topological protection mechanism. Our experimental results are supported by rigorous analytical and numerical modelling, validating that the quantum-classical equivalence of the topological behaviour is due to the non-separability of the states and one-sided nature of the channel. Our work blurs the classical-quantum divide in the context of topology and opens a new path to information resilience in noisy channels, such as terrestrial and satellite-to-ground communication networks.

physics.optics↗

arXiv2025

Free-form conformal metasurfaces robustly generating topological skyrmions

Skyrmions are topologically stable vector textures as potential information carriers for high-density data storage and communications, especially boosted by the recently emerging meta-generators of skyrmions in electromagnetic fields. However, these implementations always rely on planar, rigid designs with stringent fabrication requirements. Here, we propose the free-form conformal metasurface generating skyrmions towards future wearable and flexible devises for topological resilience light fields. Furthermore, we experimentally tested the outstanding topological robustness of the skyrmion number under different disorder degrees on the metasurface. This work promotes the development of flexible compact skyrmion-based communication devices and demonstrates their potential to improve the quality of space information transmission.

physics.optics↗

arXiv2025

Optical Skyrmions of Vortex Darkness

We disclose the existence of a type of optical skyrmion, Gauss-Stokes (GS) skyrmions, that is naturally present in an optical vortex around its phase singularity. Contrary to previous research with optical skyrmions, we neither shape vector beams nor superpose different spatial modes and polarizations. In GS skyrmions, the phase singularity in the transversal field of a single monochromatic beam of uniform polarization (a scalar beam) is concealed by the axial field dictated by Gauss's divergence law, giving rise to a polarization singularity of undefined polarization plane. This singularity is enclosed by a rich skyrmionic polarization texture fulfilling a topological map and covering all the states of transverse-axial polarization. In our experiment, we facilitate the observation of a GS skyrmion with the predicted features using focused fields with enhanced axial component.

physics.optics↗

arXiv2025

Observation of helical pulses

Ultrafast spatiotemporal vortex pulses constitute a category within spatiotemporal topological waves. Nevertheless, the experimental realization of helical pulses single or few cycle short vortex pulses characterized by space time nonseparability remains elusive to date. Here, we introduce two complementary methods for experimentally generating such space time nonseparable helical pulses (SNHPs) in the optical and microwave spectral regimes. We achieve few cycle quasi linearly polarized SNHPs by decomposing the optical toroidal pulses into their polarization components. We also generated single cycle nontransverse SNHPs directly from a microwave ultrawideband spiral emitter. These approaches enable the experimental realization of SNHPs and provide a platform for further investigation into their properties and applications, such as nontrivial light-matter interactions and optical communications.

physics.optics↗

arXiv2024

Photonic torons, topological phase transition and tunable spin monopoles

Creation and control of topological complex excitations play crucial roles in both fundamental physics and modern information science. Torons are a sophisticated class of 3D chiral polar topological structures with both skyrmionic quasiparticle textures and monopole point defects, so far only observed in liquid crystal nonpolar models. Here, we experimentally construct torons with the photonic spin of vector structured light and demonstrate the topological phase transitions among diverse topological states: torons, hopfions, skyrmioniums and monopole pairs. We can also continually tune the toron's chirality and the helical spin textures of emerging monopole pairs. The birth of photonic torons and tunable monopoles opens a flexible platform for studying nontrivial light-matter interaction and topological informatics.

physics.optics↗

arXiv2024

Space-Time Hopfion Crystals

Hopfions, higher-dimensional topological quasiparticles with sophisticated 3D knotted spin textures discovered in condensed matter and photonic systems, show promise in high-density data storage and transfer. Here we present crystalline structures of hopfions lying in space-time constructed by spatiotemporally structured light. A practical methodology using bichromatic structured light beams or dipole arrays to assemble 1D and higher dimensional hopfion lattices is proposed and a technique for tailoring topological orders is elucidated. The birth of photonic hopfion crystals heralds a new era in high-dimensional, condensed, and robust topological information processing.

physics.optics↗

arXiv2024

Optical skyrmions from metafibers

Optical skyrmions are an emerging class of structured light with sophisticated particle-like topologies with great potential for revolutionizing modern informatics. However, the current generation of optical skyrmions involves complex or bulky systems, hindering their development of practical applications. Here, exploiting the emergent "lab-on-fiber" technology, we demonstrate the design of a metafiber-integrated photonic skyrmion generator. We not only successfully generated high-quality optical skyrmions from metafibers, but also experimentally verified their remarkable properties, such as regulability and topological stability with deep-subwavelength features beyond the diffraction limits. Our flexible and fiber-integrated optical skyrmions platform paves the avenue for future applications of topologically-enhanced remote super-resolution microscopy and super-robust information transfer.

physics.optics↗