arXiv subjects

Pedro David García

Publications and source records attributed to Pedro David García.

10 recordsLinked to original sources

arXiv2026

Robust Radiative Cooling in Functionalizable Silica Microsphere Paints

Disordered coatings based on silica microspheres provide a scalable and robust platform for passive daytime radiative cooling. While particle-size optimization is often considered critical for enhancing solar scattering, the role of microsphere diameter once a coating operates in the multiple-scattering regime remains unclear. Here, we characterize the radiative cooling performance of disordered, optically thick photonic glass coatings with diameters ranging from 2 to 8 um. Despite measurable differences in microscopic scattering properties, both the spectral radiative response and the net cooling performance are robust to variations in particle diameter when the system operates deep in the diffusive regime. Outdoor thermal measurements reveal nearly identical steady-state temperature reductions across the full size range. These results indicate that radiative cooling in photonic glass coatings is governed by collective light transport, enabling microsphere size to be selected based on surface chemistry or processing constraints without compromising cooling performance.

physics.optics↗

arXiv2025

Rough Fabry-Perot cavity: a vastly multi-scale numerical problem

A commercial Fabry-Perot laser diode is characterized by highly disproportionate dimensions, which poses a significant numerical challenge, even for state-of-the-art tools. This challenge is exacerbated when one of the cavity mirrors is rough-ened, as is the case when fabricating random laser diodes. Such a system involves length scales from several hundred mi-crometres (length) to a few nanometres (roughness) all of which are relevant when studying optical properties in the visi-ble. While involving an extreme range of dimensions, these cavities cannot be treated through statistical approaches such as those used with self-similar fractal structures known to show well-studied properties. Here we deploy numerical meth-ods to compute cavity modes and show how random corrugations of the Fabry-Perot cavity wall affect statistical proper-ties of their spectral features. Our study constitutes a necessary first step in developing technologically essential devices for photonic computation and efficient speckle-free illumination.

physics.optics↗

arXiv2022

Cavity optomechanics with Anderson-localized optical modes

Confining photons in cavities enhances the interactions between light and matter. In cavity optomechanics, this enables a wealth of phenomena ranging from optomechanically induced transparency to macroscopic objects cooled to their motional ground state. Previous work in cavity optomechanics employed devices where ubiquitous structural disorder played no role beyond perturbing resonance frequencies and quality factors. More generally, the interplay between disorder, which must be described by statistical physics, and optomechanical effects has thus far been unexplored. Here, we demonstrate how sidewall roughness in air-slot photonic-crystal waveguides can induce sufficiently strong backscattering of slot-guided light to create Anderson-localized modes with quality factors as high as half a million and mode volumes that are below the diffraction limit. We observe how the interaction between these disorder-induced optical modes and in-plane mechanical modes of the slotted membrane is governed by a distribution of coupling rates, which can exceed $g_{\text{o}}/2π\sim 200$ kHz, leading to mechanical amplification up to self sustained oscillations via optomechanical backaction. Our work constitutes the first steps towards understanding optomechanics in the multiple-scattering regime and opens new perspectives for exploring complex systems with multitude mutually-coupled degrees of freedom.

physics.optics↗

arXiv2021

Observation of slow light in glide-symmetric photonic-crystal waveguides

We report optical transmission measurements on suspended silicon photonic-crystal waveguides, where one side of the photonic lattice is shifted by half a period along the waveguide axis. The combination of this glide symmetry and slow light leads to a strongly enhanced chiral light-matter interaction but the interplay between slow light and backscattering has not been investigated experimentally in such waveguides. We build photonic-crystal resonators consisting of glide-symmetric waveguides terminated by reflectors and use transmission measurements as well as evanescent coupling to map out the dispersion relation. We find excellent agreement with theory and measure group indices exceeding 90, implying significant potential for applications in slow-light devices and chiral quantum optics. By measuring resonators of different length, we assess the role of backscattering induced by fabrication imperfections and its intimate connection to the group index.

physics.optics↗

arXiv2020

Quantifying the robustness of topological slow light

Low-dimensional nanostructured materials can guide light propagating with very low group velocity vg. However, this slow light is significantly sensitive to unwanted imperfections in the critical dimensions of the nanostructure. The backscattering mean free path, xi, the average ballistic propagation length along the waveguide, quantifies the robustness of slow light against this type of structural disorder. This figure of merit determines the crossover between acceptable slow-light transmission affected by minimal scattering losses and a strong backscattering-induced destructive interference when xi exceeds the waveguide length L. Here, we calculate the backscattering mean free path for a topological photonic waveguide for a specific and determined amount of disorder and, equally relevant, for a fixed value of the group index ng which is the slowdown factor of the group velocity with respect to the speed of light in vacuum. These two figures of merit, xi and ng, should be taken into account when quantifying the robustness of topological and conventional (non-topological) slow-light transport at the nanoscale. Otherwise, any claim on a better performance of topological guided light over conventional one is not justified.

physics.optics↗

arXiv2018

Anderson photon-phonon co-localization in certain random superlattices

Fundamental concepts in quantum physics and technological applications ranging from the detection of gravitational waves to the generation of stimulated Brillouin scattering rely on the interaction between the optical and the mechanical degrees of freedom.\ A key parameter to engineer this interaction is the spatial overlap between the two fields, optimized in carefully designed resonators on a case-by-case basis.\ Disorder is an alternative strategy to confine light and sound at the nanoscale.\ However, it lacks an \textit{a priori} mechanism guaranteeing a high degree of co-localization due to the inherently complex nature of the underlying interference process.\ Here, we propose a way to address this challenge by using GaAs/AlAs vertical distributed Bragg reflectors with embedded geometrical disorder.\ Due to a remarkable coincidence in the physical parameters governing light and motion propagation in these two materials, the equations for both longitudinal acoustic waves in the growth direction and normal-incidence light become practically equivalent for excitations of the same wavelength.\ This guarantees spatial overlap between photons and phonons leading to a statistically significant enhancement in the vacuum optomechanical coupling rate, $g_{0}$, and making this system a promising candidate to explore Anderson localization of high frequency ($\sim$ 20 GHz) phonons enabled by cavity optomechanics.\

physics.optics↗

arXiv2017

Two mechanisms of disorder-induced localization in photonic-crystal waveguides

Unintentional but unavoidable fabrication imperfections in state-of-the-art photonic-crystal waveguides lead to the spontaneous formation of Anderson-localized modes thereby limiting slowlight propagation and its potential applications. On the other hand, disorder-induced cavities offer an approach to cavity-quantum electrodynamics and random lasing at the nanoscale. The key statistical parameter governing the disorder effects is the localization length, which together with the waveguide length determines the statistical transport of light through the waveguide. In a disordered photonic-crystal waveguide, the localization length is highly dispersive, and therefore, by controlling the underlying lattice parameters, it is possible to tune the localization of the mode. In the present work, we study the localization length in a disordered photonic-crystal waveguide using numerical simulations. We demonstrate two different localization regimes in the dispersion diagram where the localization length is linked to the density of states and the photon effective mass, respectively. The two different localization regimes are identified in experiments by recording the photoluminescence from quantum dots embedded in photonic-crystal waveguides.

physics.optics↗

arXiv2017

Physics of quantum light emitters in disordered photonic nanostructures

Nanophotonics focuses on the control of light and the interaction with matter by the aid of intricate nanostructures. Typically, a photonic nanostructure is carefully designed for a specific application and any imperfections may reduce its performance, i.e., a thorough investigation of the role of unavoidable fabrication imperfections is essential for any application. However, another approach to nanophotonic applications exists where fabrication disorder is used to induce functionalities by enhancing light-matter interaction. Disorder leads to multiple scattering of light, which is the realm of statistical optics where light propagation requires a statistical description. We review here the recent progress on disordered photonic nanostructures and the potential implications for quantum photonics devices.

physics.optics↗

arXiv2017

Optomechanical coupling in the Anderson-localization regime

Optomechanical crystals, purposely designed and fabricated semiconductor nanostructures, are used to enhance the coupling between the electromagnetic field and the mechanical vibrations of matter at the nanoscale. However, in real optomechanical crystals, imperfections open extra channels where the transfer of energy is lost, reducing the optomechanical coupling eficiency. Here, we quantify the role of disorder in a paradigmatic one-dimensional optomechanical crystal with full phononic and photonic bandgaps. We show how disorder can be exploited as a resource to enhance the optomechanical coupling beyond engineered structures, thus providing a new toolset for optomechanics.

physics.optics↗

arXiv2012

Nonuniversal intensity correlations in 2D Anderson localizing random medium

Complex dielectric media often appear opaque because light traveling through them is scattered multiple times. Although the light scattering is a random process, different paths through the medium can be correlated encoding information about the medium. Here, we present spectroscopic measurements of nonuniversal intensity correlations that emerge when embedding quantum emitters inside a disordered photonic crystal that is found to Anderson-localize light. The emitters probe in-situ the microscopic details of the medium, and imprint such near-field properties onto the far-field correlations. Our findings provide new ways of enhancing light-matter interaction for quantum electrodynamics and energy harvesting, and may find applications in subwavelength diffuse-wave spectroscopy for biophotonics.

physics.optics↗