arXiv subjects

Ángela Barreda

Publications and source records attributed to Ángela Barreda.

5 recordsLinked to original sources

arXiv2026

Towards Polarization Routing of Magnetic and Electric Dipolar Emission with Dielectric Metasurfaces

We investigate the polarization properties of emission associated with the magnetic dipole and electric dipole transitions of europium(III) coupled to an anisotropic dielectric metasurface with polarization-engineered electric and magnetic photonic local density of states. The metasurface consists of a square array of Mie-resonant elliptical a-Si:H dimers situated on an SiO$_2$ substrate and embedded in a PMMA film containing Eu(TTA)$_3$. Based on reciprocity principle, it was designed to achieve maximum electric (magnetic) field enhancement in the dimer gap at 610 nm (590 nm) for $x$-polarized ($y$-polarized) normally incident light in order to selectively enhance the electric dipole (magnetic dipole) emission into the $x$-polarized ($y$-polarized) emission channel, respectively. Momentum-resolved spectroscopy and back-focal plane imaging of emission of the fabricated light-emitting metasurface clearly reveal the intended polarization-dependent emission behaviour, with the $x$-polarized ($y$-polarized) emission showing a reduced (enhanced) ratio of the magnetic-/electric dipole emission intensity, correspondingly where the magnetic dipole emission is enhanced with a magnetic field enhancement from the nanostructures. The demonstrated polarization-dependent interaction of a designed nanostructure with the electric- and magnetic dipolar transitions of trivalent lanthanide ions opens an avenue towards routing of emission of different multipolar orders into different polarization channels.

physics.optics↗

arXiv2025

Polarization Dependent Enhancement of Magnetic Dipolar Emission with Silicon Nanodimers

Eu(TTA)3 complexes are used as an emission source in the presence of high refractive index dielectric nanostructures. These nanostructures support Mie-type resonances that modify the local density of optical states. Specifically, the silicon dimer provides polarization-dependent electric and magnetic field enhancement in the dimer gap to modify the electric dipolar and magnetic dipolar emissions of the Eu3+ at 610 nm and 590 nm, respectively. Finite element method simulations are used to determine the optimal parameters for the sample and to demonstrate the polarization-dependent emission enhancement of dipolar emitters in the gap. A two-step electron beam lithography process is used to fabricate the hybrid nanoscopic structures, with a Eu3+ doped electron beam resist located only in the center of the dimer. The results demonstrate the potential of these nanostructures to selectively tailor the emission of the two distinct dipolar transitions by engineering the resonant nanostructures. Our work highlights the potential of magnetic light-matter interactions as a novel degree of freedom.

physics.optics↗

arXiv2025

Tunable Resonant Metasurfaces Empowered by Atomically Thin Semiconductors

Nanophotonics has recently gained new momentum with the emergence of a novel class of nanophotonic systems consisting of resonant dielectric nanostructures integrated with single or few layers of transition metal dichalcogenides (2D-TMDs). Thinned to the single layer phase, 2D-TMDs are unique solid-state systems with excitonic states able to persist at room temperature and demonstrate notable tunability of their energies in the optical range. Based on these properties, they offer important opportunities for hybrid nanophotonic systems where a nanophotonic structure serves to enhance the light-matter interaction in the 2D-TMDs, while the 2D-TMDs can provide various active functionalities, thereby dramatically enhancing the scope of nanophotonic structures. In this work, we combine 2D-TMD materials with resonant photonic nanostructures, namely, metasurfaces composed of high-index dielectric nanoparticles. The dependence of the excitonic states on charge carrier density in 2D-TMDs leads to an amplitude modulation of the corresponding optical transitions upon changes of the Fermi level, and thereby to changes of the coupling strength between the 2D-TMDs and resonant modes of the photonic nanostructure. We experimentally implement such a hybrid nanophotonic system and demonstrate voltage tuning of its reflectance as well as its different polarization-dependent behavior. Our results show that hybridization with 2D-TMDs can serve to render resonant photonic nanostructures tunable and time-variant $-$ important properties for practical applications in optical analog computers and neuromorphic circuits.

physics.optics↗

arXiv2024

Polarization-Insensitive Integration of Nanoparticle-on-a-Slit Cavities with Dielectric Waveguides for On-chip Surface Enhanced Raman Spectroscopy

Amongst the available plasmonic nanostructures, nanoparticle-on-a-mirror (NPoM) cavities - consisting of metal nanoparticles separated from a metal mirror by a molecular-size monolayer - provide the ultimate light confinement in gaps even below 1 nm. A variation of the NPoM cavity is the nanoparticle-on-a-slit (NPoS) configuration, where the nanoparticle is placed on a functionalized narrow slit created on a metal plate so that there are two nanometric-scale gaps for plasmonic localization. Interestingly, the NPoS cavity can also perform as a dual dipole antenna to localize both infrared and visible light, which is useful in molecular optomechanics. For many applications, it is desirable to integrate such cavities on a chip and provide access to (and collection from) the hot spots via photonic integrated waveguides. In this work, we propose, design, and experimentally demonstrate the efficient integration of NPoS plasmonic cavities with dielectric waveguides on a silicon-based chip. To this end, we use silicon-nitride slot waveguides and show that both the fundamental TE and TM modes can be used to drive the cavity, making our device polarization-independent. We demonstrate our concept by performing surface-enhanced Raman spectroscopy of BPT molecules on a chip fabricated by standard silicon fabrication tools mixed with the deterministic positioning of gold nanospheres on the gap of a plasmonic dipole antenna.

physics.optics↗

arXiv2020

Dispersive optomechanics of supercavity modes in high-index disks

In this work, we study the dispersive coupling between optical quasi-bound-states in the continuum at telecom wavelengths and GHz-mechanical modes in high-index wavelength-sized disks. We show that such cavities can display values of the optomechanical coupling rate on par with optomechanical crystal cavities ($g_{0}/2π\backsimeq$ 800 kHz). Interestingly, optomechanical coupling of optical resonances with mechanical modes at frequencies well above 10 GHz seems attainable. We also show that mechanical leakage in the substrate can be extremely reduced by placing the disk over a thin silica pedestal. Our results suggest a new route for ultra compact optomechanical cavities which can potentially be arranged in massive arrays forming optomechanical metasurfaces.

physics.optics↗