arXiv subjects

Ricardo Martin Abraham-Ekeroth

Publications and source records attributed to Ricardo Martin Abraham-Ekeroth.

5 recordsLinked to original sources

arXiv2026

Near-Field Mechanical Fingerprints for THz Sensing of 'Hidden' Nanoparticles in Complex Media

Terahertz (THz) spectroscopy holds transformative potential for non-invasive sensing, yet characterizing individual nanoparticles in complex biological environments remains challenging due to the far-field diffraction limit. While near-field dipolar theory is well established, its application to characterizing/identifying nanoparticles immersed in complex media at THz frequencies is largely unexplored. This work utilizes numerical simulations of magneto-optical (MO) heterodimers -- comprising n-doped Indium Antimonide (n-InSb) and isotropic or birefringent particles (e.g., SiO2, GaSe) -- under counter-propagating, circularly polarized THz illumination. We demonstrate that while far-field observables like absorption cross-sections are often dominated by the MO-active particle, mechanical variables-specifically induced binding forces and spin/orbital torques-exhibit superior sensitivity for detecting "hidden" neighboring components. Because these mechanical signatures depend directly on near-field interactions, they provide higher information density regarding interparticle coupling. Key findings reveal material-specific spectral "hotspots" and "zeros" that serve as robust calibration markers even within dispersive biological surrogates. We show that the spin torque on non-MO particles is significantly modified by MO-neighbor proximity, a phenomenon controllable via static magnetic fields. Furthermore, these variables exhibit high angular sensitivity in perpendicular configurations. Our results provide a roadmap for using optomechanical signatures as high-resolution detectors for in-vivo diagnostics, signal transduction, and low-energy nanocircuit control.

physics.app-ph↗

arXiv2025

Modeling Realistic Dynamics of Nanoparticle Dimers for Magneto-Optical Matter

Traditional approaches to optical matter often involve complex illumination fields with costly and unstable setups, requiring strong gradient forces, high-intensity laser spots that could harm samples, and substrate support. For binding, attractive inter-particle forces may not be sufficient to assemble systems due to unbalanced components such as centrifugal forces or collisions. In previous work, magneto-optical nanoparticles illuminated with two counter-propagating circularly polarized waves were optically bound under quasi-static conditions. However, the dynamics of such nano systems were not thoroughly considered. Here, a general framework to study magneto-optical (MO) matter is introduced, controllable by static magnetic fields. Dynamic binding between two n-doped InSb nanoparticles, which exhibit surface plasmons at THz frequencies, is recreated. Additionally, the reported examples may represent a novel approach of low-energy illumination sources without gradient components. This numerical framework, grounded in Langevin dynamics and realistic collision phenomena, serves as a robust and universal tool for exploring various optomechanical designs. The impact of thermal noise, collision types, initial conditions, and resonance excitation on a dimer system is examined. Dimers tuned initially at magneto-optical resonance can bind in stable, average positions even when particle-particle collisions are present. The current methodology provides essential knowledge for studying optical binding and the dynamics of any small-scale cluster of interacting sub-units.

physics.optics↗

arXiv2023

Control and sorting of eccentric all-dielectric core-shell nanoparticles using two counter-propagating plane waves

Many typical nanoscale structures consist of dielectric nanoparticles with an inevitable oxide-generated coating around them. Depending on the fabrication techniques, these coatings may not be homogeneous, and their distortion can cause problems in the applications of such systems. Based on finite element simulations, inhomogeneous core-shell nanoparticle systems are numerically studied when illuminated with two counter-propagating plane waves in the optical range. It is found that the electromagnetic field distortions caused by the inhomogeneous system under Mie resonance conditions allow the system to exhibit controllable one-directional impulsion and rotation, which mainly depends on the offset between the core and shell. The overall geometry and composition of the system also dictate the type of resonance being excited. Overall, this "photonic thruster" effect consisting of an accelerating and spinning projectile would provide stability to particle movement and additionally establish a method to distinguish inhomogeneous from homogeneous particles. The method can be scaled to a wide range of nanoscale dielectric particles. Thus, the results are useful for detecting defects in nanosystems with a simple concept and may open avenues for improving nanoparticle synthesis methods.

physics.optics↗

arXiv2023

Numerical study of magneto-optical binding between two dipolar particles under illumination by two counter-propagating waves

The formation of a stable magneto plasmonic dimer with THz resonances is theoretically studied for the principal directions of the system. Unlike a recent report, our work provides a complete description of the full photonic coupling for arbitrary magnetic fields as, for instance, unbalanced particle spins. As an illustration, we consider two small, n-doped InSb nanoparticles under illumination by two counter-propagating plane waves. Remarkably, when an external magnetic field exists, the symmetry in the system is broken, and a resonant radiation pressure for the dimer appears. Similarly, tunable inter-particle forces and spins are exerted on the non-reciprocal dimer. The system is also characterized when the magnetic field is absent. Moreover, we show how the mechanical observables truly characterize the dimer since their resonance dependency contains detailed information about the system. Unlike far-field observables like absorption, mechanical magnitudes depend on the system's near-field. In addition, the nature of the particle spins is originally explained by the energy flow's behavior around the dimer. This work constitutes a generalization of any previous approach to optical binding between small nanoparticles. It paves the way for fully controlling optical matter and nano factory designs based on surface plasmon polaritons.

physics.optics↗

arXiv2021

Radioplasmonics: design of plasmonic milli-particles in air and absorbing media for antenna communication and human-body in-vivo applications

Surface plasmons with MHz-GHz energies are predicted by using milliparticles made of metamaterials that behave like metals in the radiofrequency range. In this work, the so-called Radioplasmonics is exploited to design scatterers embedded in different realistic media with tunable absorption or scattering properties. High-quality scattering/absorption based on plasmon excitation is demonstrated through a few simple examples, useful to build antennas with better performance than conventional ones. Systems embedded in absorbing media as saline solutions or biological tissues are also considered to improve biomedical applications and contribute with real-time, in-vivo monitoring tools in body tissues. In this regard, any possible implementation is criticized by calculating the radiofrequency heating with full thermal simulations. As proof of the versatility offered by radioplasmonic systems, plasmon "hybridization" is used to enhance near-fields to unprecedented values or to tune resonances as in optical spectra, minimizing the heating effects. Finally, a monitorable drug-delivery in human tissue is illustrated with a hypothetical example. This study has remarkable consequences on the conception of plasmonics at macroscales. The recently-developed concept of "spoof" plasmons achieved by complicated structures is simplified in Radioplasmonics since bulk materials with elemental geometries are considered.

physics.app-ph↗