arXiv subjects

Rosario Martínez-Herrero

Publications and source records attributed to Rosario Martínez-Herrero.

5 recordsLinked to original sources

arXiv2026

Super-pupil beam engineering for enhanced confinement of azimuthally polarized depletion beams

Fluorescence depletion microscopy techniques require optical fields with a well-defined and spatially confined central intensity minimum to achieve sub-diffraction lateral resolution. Here, we present the design and experimental implementation of an azimuthally polarized, doughnut-shaped depletion beam based on super-pupil engineering principles. By tailoring the radial amplitude distribution at the entrance pupil to approximate a Bessel-type target function, the resulting focal field exhibits a tighter central doughnut compared to conventional circularly or azimuthally polarized beams. The designed pupil field distribution is implemented using a phase-only spatial light modulator operated in a double-pass configuration, enabling independent modulation of orthogonal polarization components via complex-field holographic encoding. Analytical modeling of the designed field predicts an estimated resolution gain of approximately 24% and a reduction in required depletion power of approximately 42% relative to a canonical circularly polarized Laguerre-Gaussian beam. Although the engineered field exhibits pronounced sidelobes, these do not preclude its use as a depletion beam, since lateral resolution is strongly influenced by the spatial confinement and effective suppression of the central intensity minimum for a given depletion intensity.

physics.optics↗

arXiv2026

Hidden transverse-flow topology in partially coherent structured light

Partial coherence is commonly viewed as a mechanism that reduces contrast or smooths intensity structure. Here we show that it can also encode hidden transverse-flow topology. Starting from the cross-spectral density, we formulate a generalized transverse flux, an effective velocity field, and the associated flux trajectories for quasi-monochromatic partially coherent paraxial beams. This construction converts two-point correlation phases into local transport information and reduces to the usual coherent energy-flow picture in the single-mode limit. Because the generalized flux is obtained through a local differential operation on the cross-spectral density, the proposed trajectories can, in principle, be reconstructed from measurements of the complex second-order coherence function, without requiring direct measurement of individual optical paths. Two analytical beam families expose this hidden topology. In twisted Gaussian Schell-model beams, a Gaussian intensity hides a distributed rotational flow with nonzero vorticity. In Laguerre-Christoffel-Darboux beams, sources with identical intensity profiles can have different flux topology, producing either spiral or purely radial trajectories. Thus, intensity and coherence magnitude do not exhaust the physical information contained in the cross-spectral density: partial coherence can reorganize the hidden topology of transverse optical transport.

physics.optics↗

arXiv2026

Effective skyrmion number for mixed polarization states of light

Polarization skyrmions are usually characterized through a unit Stokes vector field, which defines a map from the transverse plane to the Poincaré (Bloch) sphere and allows one to assign a skyrmion number under appropriate boundary conditions. This description assumes complete polarization. In many optical situations, however, the local polarization state is partially polarized and is therefore described by a spectral polarization matrix rather than by a single Jones vector. We formulate a density-matrix-based effective extension of the skyrmion-number construction for statistically stationary, quasi-monochromatic paraxial fields in terms of the normalized spectral polarization matrix. Its eigenvectors define two orthogonal polarization eigenstates, corresponding to antipodal points on the sphere, while the eigenvalue imbalance is fixed by the local degree of polarization $P({\bf r})$. Averaging the opposite skyrmion-density contributions of these two eigenpolarizations leads to an effective skyrmion number in which the usual pure-state density is weighted by $P({\bf r})$. The resulting quantity reduces to the conventional skyrmion number for fully polarized fields and vanishes in locally unpolarized regions. In general it is not an integer topological invariant; rather, it is an integrated effective measure, constructed from local Stokes parameters, of the skyrmionic content associated with the polarized part of a mixed optical field. We illustrate the construction with an analytic Gaussian-beam example in which a degree-one polarization texture is combined with a radially varying degree of polarization.

physics.optics↗

arXiv2025

Tailored Hotspots from Airy-Based Surface Plasmon Polaritons

Surface plasmons have attracted growing interest from the photonics community due to their inherent ability to controllably confine light below the diffraction limit and their direct application in trapping and transporting matter at the nanoscale. This method, known as plasmonic tweezers, employs confined fields generated by either localized plasmons or surface plasmon polaritons (SPP), which originate in the vicinity of nanostructure-based traps or across structureless platforms, respectively. Herein, we present a new theoretical method for generating intense light hotspots and engineering their features by overlapping Airy SPPs (ASPP) at a smooth dielectric-metal interface. We coherently add pairs of Hermite-Gauss modes that belong to a novel complete basis set of finite-energy ASPPs, which yield highly confined plasmonic hotspots ($\approx λ$/10) without the need of using any nanostructured platform. Mode order and relative spacing parameters can be used to tailor the intensity and quality factor of said hotspots, largely outperforming their Gaussian-only-based counterparts. Our method opens a promising venue to confine light at the nanoscale using ASPP-based structured light, which helps to advance the development of structureless plasmonic tweezers and holds promising potential for its application in optical signal processing and plasmonic circuitry.

physics.optics↗

arXiv2018

Partially Coherent Sources with Inhomogeneous Azimuth

A new model of physically realizable electromagnetic source is proposed. The source is partially coherent and non-uniformly totally polarized. The coherence and polarization characteristics of this new source are analyzed. The spatial coherence area of the source can be easily modified at will. The state of polarization is linear across the transverse plane of the source with an azimuth that varies from point to point in a different way depending on the selected values of the parameters that define the source.

physics.optics↗