arXiv subjects

Danilo Gomes Pires

Publications and source records attributed to Danilo Gomes Pires.

4 recordsLinked to original sources

arXiv2026

Particle-like topologies of light in turbulent complex media

The basic building blocks of many forms of optical topologies are particle-like singularities in phase and polarisation, giving rise to lines of darkness that weave complex threads in 3D space. Although known for half a century since seminal work on dislocations in wave trains, their behaviour in complex media remains under debate, especially with respect to their relative stability. Here we show that polarisation and phase vortices behave identically in one-sided turbulent complex channels. We perform complementary numerical and experimental studies using atmospheric turbulence as a test case, demonstrating agreement and equivalent dynamics. Our work addresses open questions on optical topologies and will be relevant to their harnessing for applications such as sensing, communication, imaging, and information transfer in noisy or complex environments.

physics.optics↗

arXiv2025

Deep Learning Driven Enhancement of Optical Vortex Line Robustness in Atmospheric Turbulence

The stability of optical vortex structures in turbulent environments is critical for their applications in optical communication, quantum information, and structured light technologies. Although topological invariants, such as crossings and linking numbers, are fundamentally invariant, recent studies reveal that their observed values deteriorate considerably in turbulent conditions due to environmental effects. In this study, we introduce an alternative approach based on the geometric stability of three-dimensional singularity line shapes, demonstrating that shape-based tracing of singularities outperforms both topological and spectral methods in turbulence. To test this concept, we propose Flower Beams, a novel class of structured optical fields featuring controllable petal-like singularity morphologies. We construct an 81-element optical alphabet and classify these structures after turbulence using deep learning. Our findings reveal that shape-based tracing achieves classification accuracy exceeding 90% in the weaker turbulence regimes and remains highly competitive even in stronger turbulence, significantly outperforming spectral and topology-based approaches. Experimental results confirm that the predicted shape stability holds in real-world conditions. This study stablishes the shape of the singularities' lines as a scalable and resilient alternative for structured light tracing and transmission, opening new avenues for turbulence-robust-applications.

physics.optics↗

arXiv2025

Structuring Polarization States of Light in Space and Time

The spatiotemporal sculpturing of light beams with arbitrary phase and polarization topologies has garnered significant attention in recent years due to its potential to advance optical technologies and reveal novel physical phenomena. Examples of spatiotemporal beams include space-time wave packets, flying donuts, tilted pulse fronts, X-waves, Airy pulses, and spatiotemporal optical vortices. Here, we introduce and demonstrate a new class of spatiotemporal polarization states of light. We propose a generalized spatiotemporal higher-order Poincaré sphere and show that these polarization states emerge from the superposition of two orthogonal circular polarization states, each carrying a spatiotemporal optical vortex. Such a choice of the basis enables simultaneous control of the spatial and temporal degrees of freedom of light. Theoretical predictions are experimentally validated using ultrafast femtosecond pulses, revealing how the resulting polarization distributions evolve in both space and time. Finally, we further extend this approach to construct a family of spatiotemporal skyrmionic textures that are localized, topologically nontrivial configurations of the electromagnetic field vector, offering a versatile framework for generating and controlling multidimensional (space and time) structured polarization fields. The ability to create and manipulate diverse forms of spatiotemporal skyrmionic textures opens up new opportunities for studying complex light-matter interaction phenomena, advanced imaging and micromanipulation, and encoding information across both space and time, with potential implications for advanced optical communication and information processing in classical and quantum domains

physics.optics↗

arXiv2025

Nonlinear Nonlocal Metasurface for Harmonic Generation and Manipulation

The discovery of second harmonic generation in 1961 marked the birth of nonlinear optics, unlocking a range of applications from frequency conversion to quantum light generation. Yet, phase matching in bulk nonlinear crystals remains a key bottleneck. Thinning nonlinear media eases this constraint but severely reduces nonlinear efficiency due to limited interaction length. Photonic metasurfaces, planar arrays of subwavelength meta atoms, offer a compelling alternative by supporting resonant modes that enhance local fields. However, existing designs suffer from a trade off between the high efficiency of nonlocal metasurfaces and the precise wavefront control enabled by local ones. These two capabilities have remained decoupled due to their fundamentally different mechanisms. Here, we design a nonlinear nonlocal metasurface supporting quasi trapped modes (QTM), enabling efficient third harmonic generation and meta atom level phase manipulation. Using topologically asymmetric all-dielectric meta-atoms, we achieve strong field confinement and demonstrate THG enhancement exceeding three orders of magnitude compared to unstructured films. By exploiting symmetry and Pancharatnam-Berry (PB) phase via meta atom rotation, we realize helicity dependent wavefront control at both the fundamental and TH wavelengths. A slight boundary perturbation yields geometric phase accumulation only at resonance, a behavior absent in conventional PB based metasurfaces. This selectivity arises from QTM field profiles that maintain global symmetry off resonance while enabling local geometric phase encoding at resonance. Our results advance silicon photonics and reveal new mechanisms for nonlinear geometric phase control at the nanoscale.

physics.optics↗