arXiv subjects

Jaime Gómez Rivas

Publications and source records attributed to Jaime Gómez Rivas.

At least 19 recordsLinked to original sources

arXiv2026

Dispersion Control of Chiral Exciton-Polariton Transport with Dielectric Metasurfaces

Exciton-polaritons provide a powerful platform for manipulating hybrid light-matter states with low effective masses and strong nonlinearities. Introducing chirality into these quasiparticles enables selective control over their spin and propagation, opening new opportunities for chiral transport and spin-selective polaritonic devices. We exploit the strong chiral light-matter coupling in silicon metasurfaces composed of tilted nanorod dimers to demonstrate selective transport of organic chiral exciton-polaritons. The metasurface supports surface lattice resonances and quasi-bound states in the continuum that simultaneously provide high photonic confinement and extrinsic chirality, giving rise to chiral exciton-polaritons in the achiral molecules. These exciton-polaritons exhibit a large magnitude of the dissymmetry factor, reaching a value of 0.93. Using photoluminescence Fourier microscopy and real-space imaging, we show that chiral exciton-polaritons propagate over distances exceeding 50 um without significant degradation of their dissymmetry, with characteristic propagation lengths of approximately 6-13 um. These propagation lengths correspond to an enhancement of 3 orders of magnitude compared to bare excitons. This work constitutes the first demonstration of enhanced and selective chiral transport of organic exciton-polaritons, driven by strong light-matter coupling, in achiral metasurfaces, paving the way for spin-selective polaritonic technologies using simple metasurfaces.

physics.optics↗

arXiv2026

Nanoparticle Arrays for Efficient Organic Light-Emitting Diode Emission Management

OLEDs are increasingly applied in illumination and displays because they offer excellent color quality, are mechanically flexible, and are self-emissive. However, their usage is limited by low external quantum efficiency (EQE) and efficiency roll-off at high driving voltages. These limitations, together with demands for smaller pixels and device sizes in emerging technologies, motivate innovations that increase efficiency and allow replacing external optical elements with embedded solutions. Here, we demonstrate enhanced outcoupling as well as directional and polarization control of OLED emission, based on collective surface lattice resonances of plasmonic nanoparticle arrays that are embedded in the active layers of four different state-of-the-art OLED structures. Both square arrays and more complex lattices producing flat bands are demonstrated to guide the light to directions and polarizations determined by their optical modes. We show that by the design of the array geometry and the OLED structure, spectral and angular enhancement of the electroluminescence (EL), up to 30 %, can be achieved. Our results verify that surface lattice resonances of nanoparticle arrays offer a robust and versatile embedded solution for tailoring the OLED emission, as well as exciting prospects for efficiency increase if combined with narrow-spectrum emitters.

physics.optics↗

arXiv2025

Confinement of Polariton Condensates in quasi-Flatband BICs in Plasmonic and Dielectric Metasurfaces

We investigate exciton-polariton condensation in square arrays, composed of either dielectric silicon (Si) or plasmonic silver (Ag) nanodisks, covered with a dye-doped layer. Both arrays support symmetry-protected bound states in the continuum (BICs) at normal incidence, featuring electric quadrupolar ($( Q_{xy} $)) and magnetic dipolar ($( m_z $)) characters. Due to differences in mode coupling, these BICs are split by $(\sim 10$) meV in the Si array, whereas they remain nearly degenerate in the Ag array. Simulations reveal that interference in the Ag array results in hybrid modes, $((m_z + i\tilde{Q}_{xy})$) and $((m_z - i\tilde{Q}_{xy})$), which are polarized along orthogonal directions. Interestingly, this results in similar lasing thresholds in both Si and Ag arrays, regardless of the inherent non-radiative losses of Ag, and also a confinement of the polariton condensates in the Ag array. While condensation in the Si array occurs in the $( Q_{xy} $) BIC, producing a characteristic donut-shaped far-field emission in k-space, condensation in the Ag array populates the hybrid modes, leading to a double-cross emission pattern extending over a broad range of wave vectors due to the quasi-flatband nature of this mode. As a result, the Ag array also exhibits a strong confinement along the polarization axis in real space. However, for unpolarized emission, there is a similar spatial confinement in both Si and Ag arrays. This control over the confinement of condensates could also be exploited to control interactions. Our results highlight a novel mechanism for condensate confinement with potential applications in quantum computing and polaritonic circuitry.

physics.optics↗

arXiv2025

Robust Circularly Polarized Luminescence via Quasi-Bound States in the Continuum in Intrinsic Chiral Silicon Metasurfaces

We demonstrate a circularly polarized photoluminescence emission, with dissymmetry factors $g_\mathrm{PL}$ over 0.1, from achiral organic dye molecules by leveraging quasi-bound states in the continuum (quasi-BICs) and surface lattice resonances (SLRs) in intrinsic silicon chiral metasurfaces. We find that the $g_\mathrm{PL}$ associated with the quasi-BIC mode remains robust against variations in emission angle and dye thickness owing to its strong lateral field confinement. In contrast, the $g_\mathrm{PL}$ of the SLR mode exhibits sign inversion depending on the emission energy and dye layer thickness. The experimental results are supported by mode decomposition analysis, helicity density analysis, and near-field spatial distribution of the electric field. These findings illustrate the relevance of the emitter's layer thickness in optimizing the emission of circularly polarized light. They also elaborate on the robustness of chiral quasi-BICs, offering insights into chiral light-matter interactions and advancing the design of circularly polarized light-emitting devices.

physics.optics↗

arXiv2025

Enhanced Delayed Fluorescence in Non-Local Metasurfaces: The Role of Electronic Strong Coupling

Strong light-matter coupling has garnered significant attention for its potential to optimize optoelectronic responses. In this study, we designed open cavities featuring non-local metasurfaces composed of aluminum nanoparticle arrays. The surface lattice resonances in these metasurfaces exhibit electronic strong coupling with the boron difluoride curcuminoid derivative, known for its highly efficient thermally activated delayed f luorescence in the near-infrared. Our results show that delayed fluorescence induced by triplet-triplet annihilation can be enhanced by a factor of 2.0-2.6 in metasurfaces that are either tuned or detuned to the molecular electronic transition. We demonstrate that delayed fluorescence enhancements in these systems primarily stem from increased absorption in the organic layer caused by the nanoparticle array, while strong coupling has negligible effects on reverse intersystem crossing rates, aligning with previous studies. We support these findings with finite-difference-time-domain simulations. This study elucidates how light-matter interactions affect delayed fluorescence, highlighting the potential applications in optoelectronic devices.

physics.optics↗

arXiv2024

Polaritonic Chemistry Enabled by Non-Local Metasurfaces

Vibrational strong coupling can modify chemical reaction pathways in unconventional ways. Thus far, Fabry-Perot cavities formed by pairs of facing mirrors have been mostly utilized to achieve vibrational strong coupling. In this study, we demonstrate the application of plasmonic microparticle arrays defining non-local metasurfaces that can sustain surface lattice resonances as a novel tool to enable chemical reactions under vibrational strong coupling. We show that the solvolysis kinetics of \textit{para}-nitrophenyl acetate can be accelerated by a factor of 2.7 by strong coupling to the carbonyl bond of the solvent and the solute with a surface lattice resonance. Our work introduces a new platform to investigate and control polaritonic chemical reactions. In contrast to Fabry-Perot cavities, metasurfaces define open optical cavities with single surfaces, which removes alignment hurdles, facilitating polaritonic chemistry across large areas.

physics.chem-ph↗

arXiv2023

Room Temperature Exciton-Polariton Condensation in Silicon Metasurfaces Emerging from Bound States in the Continuum

We show the first experimental demonstration of room-temperature exciton-polariton (EP) condensation from a bound state in the continuum (BIC). This demonstration is achieved by strongly coupling stable excitons in an organic perylene dye with the extremely long-lived BIC in a dielectric metasurface of silicon nanoparticles. The long lifetime of the BIC, mainly due to the suppression of radiation leakage, allows for EP thermalization to the ground state before decaying. This property results in a condensation threshold of less than 5 μJ cm^{-2}, one order of magnitude lower that the lasing threshold reported in similar systems in the weak coupling limit.

cond-mat.mes-hall↗

arXiv2022

Impact of indirect transitions on valley polarization in WS$_2$ and WSe$_2$

Controlling the momentum of carriers in semiconductors, known as valley polarization, is a new resource for optoelectronics and information technologies. Materials exhibiting high polarization are needed for valley-based devices. Few-layer WS$_2$ shows a remarkable spin-valley polarization above 90%, even at room temperature. In stark contrast, polarization is absent for few-layer WSe$_2$ despite the expected material similarities. Here, we explain the origin of valley polarization in both materials based on the interplay between two indirect optical transitions. We show that the relative energy minima at the $Λ$- and K-valleys in the conduction band determine the spin-valley polarization of the direct K-K transition. Polarization appears as the energy of the K-valley rises above the $Λ$-valley as a function of temperature and number of layers. Our results advance the understanding of the high spin-valley polarization in WS$_2$. This insight will impact the design of both passive and tunable valleytronic devices operating at room temperature.

cond-mat.mes-hall↗

arXiv2022

Exciton diffusion and annihilation in nanophotonic Purcell landscapes

Excitons spread through diffusion and interact through exciton-exciton annihilation. Nanophotonics can counteract the resulting decrease in light emission. However, conventional enhancement treats emitters as immobile and noninteracting. Here, we go beyond the localized Purcell effect to exploit exciton dynamics. As interacting excitons diffuse through optical hotspots, the balance of excitonic and nanophotonic properties leads to either enhanced or suppressed photoluminescence. We identify the dominant enhancement mechanisms in the limits of high and low diffusion and annihilation to turn their detrimental impact into additional emission. Our guidelines are relevant for efficient and high-power light-emitting diodes and lasers based on monolayer semiconductors, perovskites, or organic crystals.

physics.optics↗

arXiv2022

Engineering bound states in the continuum at telecom wavelengths with non-Bravais lattices

Various optical phenomena can be induced in periodic arrays of nanoparticles by the radiative coupling of the local dipoles in each particle. Probably the most impressive example is bound states in the continuum (BICs), which are electromagnetic modes with a dispersion inside the light cone but infinite lifetime, i.e., modes that cannot leak to the continuum. Symmetry-protected BICs appear at highly symmetric points in the dispersion of periodic systems. Although the addition of nonequivalent lattice points in a unit cell is an easy and straightforward way of tuning the symmetry, BICs in such particle lattice, i.e., non-Bravais lattice, are less explored among periodic systems. Starting from a periodic square lattice of Si nanodisks, we have prepared three non-Bravais lattices by detuning size and position of the second disk in the unit cell. Diffraction-induced coupling excites magnetic/electric dipoles in each nanodisk, producing two surface lattice resonances at the $Γ$ point with a band gap in between. %of $\sim$ 41 meV. The high/low energy branch becomes a BIC for the size/position-detuned array, respectively, while both branches are bright (or leaky) when both size and position are detuned simultaneously. The role of magnetic and electric resonances in dielectric nanoparticles and the change of BIC to bright character of the modes is explained by the two different origins of BICs in the detuned arrays, which is further discussed with the aid of a coupled electric and magnetic dipole model. This study gives a simple way of tuning BICs at telecom wavelengths in non-Bravais lattices, including both plasmonic and dielectric systems, thus scalable to a wide range of frequencies.

physics.optics↗

arXiv2021

Unveiling Symmetry Protection of Bound States in the Continuum with Terahertz Near-field Imaging

Bound states in the continuum (BICs) represent a new paradigm in photonics due to the full suppression of radiation losses. However, this suppression has also hampered their direct observation. By using a double terahertz (THz) near-field technique that allows the local excitation and detection of the THz amplitude, we are able to map for the first time the electromagnetic field of BICs over extended areas, unveiling the field-symmetry protection that suppresses far-field radiation. This investigation, done for metasurfaces of dimer rod resonators, reveals the in-plane extension and formation of BICs with anti-symmetric phases, in agreement with coupled-dipole calculations. By displacing the rods, we demonstrate that mirror symmetry is not a necessary condition for BIC formation. Only $π$-rotation symmetry is required, making BICs exceptionally robust to structural changes. This work makes the local field of BICs experimentally accessible, which is crucial for the engineering of cavities with infinite lifetimes.

physics.optics↗

arXiv2020

Collective Mie Exciton-Polaritons in an Atomically Thin Semiconductor

Optically induced Mie resonances in dielectric nanoantennas feature low dissipative losses and large resonant enhancement of both electric and magnetic fields. They offer an alternative platform to plasmonic resonances to study light-matter interactions from the weak to the strong coupling regimes. Here, we experimentally demonstrate the strong coupling of bright excitons in monolayer WS$_2$ with Mie surface lattice resonances (Mie-SLRs). We resolve both electric and magnetic Mie-SLRs of a Si nanoparticle array in angular dispersion measurements. At the zero detuning condition, the dispersion of electric Mie-SLRs (e-SLRs) exhibits a clear anti-crossing and a Rabi-splitting of 32 meV between the upper and lower polariton bands. The magnetic Mie-SLRs (m-SLRs) nearly cross the energy band of excitons. These results suggest that the field of m-SLRs is dominated by out-of-plane components that do not efficiently couple with the in-plane excitonic dipoles of the monolayer WS$_2$. In contrast, e-SLRs in dielectric nanoparticle arrays with relatively high quality factors (Q $\sim$ 120) facilitate the formation of collective Mie exciton-polaritons, and may allow the development of novel polaritonic devices which can tailor the optoelectronic properties of atomically thin two-dimensional semiconductors.

physics.optics↗

arXiv2020

Enhanced light emission by magnetic and electric resonances in dielectric metasurfaces

We demonstrate an enhanced emission of high quantum yield molecules coupled to dielectric metasurfaces formed by periodic arrays of polycrystalline silicon nanoparticles. Radiative coupling of the nanoparticles, mediated by in-plane diffraction, leads to the formation of collective Mie scattering resonances or Mie surface lattice resonances (M-SLRs), with remarkable narrow line widths. These narrow line widths and the intrinsic electric and magnetic dipole moments of the individual Si nanoparticles allow to resolve electric and magnetic M-SLRs. Incidence angle- and polarization-dependent extinction measurements and high-accuracy surface integral simulations show unambiguously that magnetic M-SLRs arise from in- and out-of-plane magnetic dipoles, while electric M-SLRs are due to in-plane electric dipoles. Pronounced changes in the emission spectrum of the molecules are observed, with almost a 20-fold enhancement of the emission in defined directions of molecules coupled to electric M-SLRs, and a 5-fold enhancement of the emission of molecules coupled to magnetic M-SLRs. These measurements demonstrate the potential of dielectric metasurfaces for emission control and enhancement, and open new opportunities to induce asymmetric scattering and emission using collective electric and magnetic resonances.

physics.optics↗

arXiv2019

Enhanced Delayed Fluorescence in Tetracene Crystals by Strong Light-Matter Coupling

We demonstrate experimentally an enhanced delayed fluorescence in tetracene single crystals strongly coupled to optical modes in open cavities formed by arrays of plasmonic nanoparticles. Hybridization of singlet excitons with collective plasmonic resonances in the arrays leads to the splitting of the material dispersion into a lower and an upper polariton band. This splitting significantly modifies the dynamics of the photo-excited tetracene crystal, resulting in an increase of the delayed fluorescence by a factor of four. The enhanced delayed fluorescence is attributed to the emergence of an additional radiative decay channel, where the lower polariton band harvests long-lived triplet states. There is also an increase in total emission, which is wavelength dependent, and can be explained by the direct emission from the lower polariton band, the more effcient light out-coupling and the enhancement of the excitation intensity. The observed enhanced fluorescence opens the possibility of effcient radiative triplet harvesting in open optical cavities, to improve the performance of organic light emitting diodes.

cond-mat.mes-hall↗

arXiv2019

Strong coupling between weakly guided semiconductor nanowire modes and an organic dye

The light-matter coupling between electromagnetic modes guided by a semiconductor nanowire and excitonic states of molecules localized in its surrounding media is studied from both classical and quantum perspectives, with the aim of describing the strong coupling regime. Weakly guided modes (bare photonic modes) are found through a classical analysis, identifying those lowest-order modes presenting large electromagnetic fields spreading outside the nanowire, while preserving their robust guided behavior. Experimental fits of the dielectric permittivity of an organic dye that exhibits excitonic states are used for realistic scenarios. A quantum model properly confirms through an avoided mode crossing that the strong coupling regime can be achieved for this configuration, leading to Rabi splitting values above 100 meV. In addition, it is shown that the coupling strength depends on the fraction of energy spread outside the nanowire, rather than on the mode field localization. These results open up a new avenue towards strong coupling phenomenology involving propagating modes in non-absorbing media.

physics.optics↗

arXiv2019

From Fano resonances to bound states in the continuum in dipole arrays at THz frequencies

Fano resonances and bound states in the continuum (BICs) exhibit a rich phenomenology stemming from, respectively, their asymmetric line shapes and infinite quality factors. Here, we show experimentally and theoretically that rod dimer metasurfaces exhibit narrow (high-Q) Fano resonances at THz frequencies. These resonances evolve continuously into a BIC as the rods in each dimer become identical. We demonstrate analytically that this is a universal behavior occurring in arrays of dimers consisting of detuned resonant dipoles. Fano resonances arise as a result of the interference between broad and narrow lattice dipole resonances, with high-Q factors tending to infinity in the detuning parameter space as the narrow lattice resonance becomes a BIC for identical resonant dipoles. Similar configurations can be straightforwardly envisioned throughout the electromagnetic spectrum leading to ultrahigh-Q Fano resonances and BICs of interest in photonics applications such as sensing and lasing.

physics.optics↗

arXiv2013

Polarization-dependent light extinction in ensembles of polydisperse, vertical semiconductor nanowires: A Mie scattering effective medium

We present an experimental and theoretical study of the angle- and polarization-dependent light extinction in random arrays of polydisperse semiconductor nanowires epitaxially grown on substrates. The specular reflectance is described by averaging the scattering properties of individual nanowires obtained from Lorenz-Mie theory over the diameter distribution. The complex effective refractive index describing the propagation and attenuation of the coherent beam scattered in forward direction is determined in the independent scattering approximation and used to calculate the angle- and polarization-dependent reflectance. Our measurements demonstrate the highly anisotropic scattering in ensembles of aligned nanowires.

physics.optics↗

arXiv2013

Mapping the directional emission of quasi-two-dimensional photonic crystals of semiconductor nanowires using Fourier microscopy

Controlling the dispersion and directionality of the emission of nanosources is one of the major goals of nanophotonics research. This control will allow the development of highly efficient nanosources even at the single photon level. One of the ways to achieve this goal is to couple the emission to Bloch modes of periodic structures. Here, we present the first measurements of the directional emission from nanowire photonic crystals by using Fourier microscopy. With this technique we efficiently collect and resolve the directional emission of nanowires within the numerical aperture of a microscope objective. The light emission from a heterostructure grown in each nanowire is governed by the photonic (Bloch) modes of the photonic crystal. We also demonstrate that the directionality of the emission can be easily controlled by infiltrating the photonic crystal with a high refractive index liquid. This work opens new possibilities for the control of the emission of sources in nanowires.

physics.optics↗