arXiv subjects

Ramón Paniagua-Domínguez

Publications and source records attributed to Ramón Paniagua-Domínguez.

7 recordsLinked to original sources

arXiv2026

Dicke Superradiance in Extended 2D Quantum Arrays Coupled to Metasurface Bound States in the Continuum

Dicke superradiance is a collective phenomenon where the emission from ensembles of quantum emitters is coherently enhanced beyond the sum of each emitter's independent emission. Here, we propose a platform that exploits the delocalised nature of a high-Q, non-local mode supported by a dielectric metasurface (a so-called bound-state-in-the-continuum or BIC) to induce superradiant behaviour within an extended two-dimensional array of distant quantum emitters. We show that these BIC-mediated emitter interactions can span several wavelengths, thus overcoming the traditional subwavelength separation between emitters required in free space. We further show that reaching the idealised Dicke limit is possible in this system, provided that the emitters are coupled to the BIC mode efficiently enough, as quantified through the $β$-factor. Moreover, we demonstrate its experimental viability by analysing its robustness to realistic experimental imperfections. This work puts forward optical metasurfaces supporting BICs as a physically viable platform for realising the upper limits of cooperative emission in physically extended quantum emitter arrays.

quant-ph↗

arXiv2026

Sampling methods to describe superradiance in large ensembles of quantum emitters

Superradiance is a quantum phenomenon in which coherence between emitters results in enhanced and directional radiative emission. Many quantum optical phenomena can be characterized by the two-time quantum correlation function $g^{(2)}(t,τ)$, which describes the photon statistics of emitted radiation. However, the critical task of determining $g^{(2)}(t,τ)$ becomes intractable for large emitter ensembles due to the exponential scaling of the Hilbert space dimension with the number of emitters. Here, we analyse and benchmark two approximate numerical sampling methods applicable to emitter arrays embedded within electromagnetic environments, which generally provide upper and lower bounds for $g^{(2)}(t,0)$. We also introduce corrections to these methods (termed offset corrections) that significantly improve the quality of the predictions. The optimal choice of method depends on the total number of emitters, such that taken together, the two approaches provide accurate descriptions across a broad range of important regimes. This work therefore provides new theoretical tools for studying the well-known yet complex phenomenon of superradiance in large ensembles of quantum emitters.

quant-ph↗

arXiv2025

Dynamic Control of Momentum-Polarization Photoluminescence States with Liquid-Crystal-tuned Nanocavities

Dynamic control of light, and in particular beam steering, is pivotal in various optical applications, including telecommunications, LiDAR, and biomedical imaging. Traditional approaches achieve this by interfacing a tunable modulating device with an external light source, facing challenges in achieving compact devices. Here, we introduce a dynamic photoluminescence (PL) modulating device, with which the properties of light directly emitted by a quasi-two-dimensional perovskite (in particular its directionality and polarization) can be modified continuously and over a large range. The device is based on a liquid-crystal-tunable Fabry-Perot (FP) nanocavity and uses the FP energy-momentum dispersion and spin-orbit coupling between the excitons and the cavity modes to enable this dynamic control over the emitted radiation. With this device, we achieve electrically-controlled, continuous and variable emission angles up to a maximum of 28°, as well as manipulation of the PL polarization state, enabling both the creation of polarization gradients and the achievement of polarization conversion at specific emission angles. Moreover, due to its resonant character, a 3-fold increase in the emission intensity is observed, as confirmed through time-resolved photoluminescence (TRPL) measurements. Our approach leverages the unique properties of actively tunable birefringent nanocavities to improve emission directivity, angle tunability and polarization control, presenting a promising solution for next-generation, deeply integrated beam steering devices.

physics.optics↗

arXiv2022

Polarization-Tunable Perovskite Light-Emitting Metatransistor

Emerging immersive visual communication technologies require light sources with complex functionality for dynamic control of polarization, directivity, wavefront, spectrum, and intensity of light. Currently, this is mostly achieved by free space bulk optic elements, limiting the adoption of these technologies. Flat optics based on artificially structured metasurfaces that operate at the sub-wavelength scale are a viable solution, however their integration into electrically driven devices remains challenging. Here we demonstrate a radically new approach of monolithic integration of a dielectric metasurface into a perovskite light-emitting transistor. We show that nanogratings directly structured on top of the transistor channel yield an 8-fold increase of electroluminescence intensity and dynamic tunability of polarization. This new light-emitting metatransistor device concept opens unlimited opportunities for light management strategies based on metasurface design and integration.

physics.optics↗

arXiv2021

Phase-change perovskite tunable microlaser

Since the invention of the laser, adoption of new gain media and device architectures has provided solutions to a variety of applications requiring specific power, size, spectral, spatial, and temporal tunability. Here we introduce a fundamentally new type of tunable semiconductor laser based on a phase-change perovskite metasurface that acts simultaneously as gain medium and optical cavity. As a proof of principle demonstration, we fabricate a subwavelength-thin perovskite metasurface supporting bound states in the continuum (BICs). Upon the perovskite structural phase transitions, both its refractive index and gain vary substantially, inducing fast (1.35 nm/K rate) and broad spectral tunability (>15 nm in the near-infrared), deterministic spatial mode hopping between polarization vortexes, and hysteretic optical bistability of the microlaser. These features highlight the uniqueness of phase-change perovskite tunable lasers, which may find wide applications in compact and low-cost optical multiplexers, sensors, memories, and LIDARs.

physics.optics↗

arXiv2021

Photonic Bound-States-in-the-Continuum Observed with an Electron Nanoprobe

Bound-states-in-the-continuum (BIC)is a wave-mechanical concept that generates resonances with vanishing spectral linewidths. It has many practical applications in Optics, such as narrow-band filters, mirror-less lasing, and nonlinear harmonic generation. As true BIC optical modes non-radiative and confined to the near field of nanostructures, they cannot be excited using propagating light. As a result, their direct experimental observation has been elusive. Rather than using light, we demonstrate probing BIC modes on arrays of silicon nanoantennas using a focused beam of electrons in a tranmission electron microscope. By combining cathodoluminescence (CL) and monochromated electron energy-loss spectroscopy (EELS) with controlled nanofabrication, we provide direct experimental evidence of "true" BIC modes, and demonstrate a BIC mode in the visible spectrum at 720 nm. The ability to observe and quantify these guided resonances with a spatial precision more than two orders of magnitude higher than previous far-field measurements allows the probing of individual elements in the nano-antenna arrays. The high-resolution experimental results are supported by numerical simulations as well as multipolar decomposition analysis, allowing us to demonstrate that the coherent interaction length of the quasi-BIC resonance requires at least 6 neighboring antenna elements, achieving over 60 times higher emissivity than for unpatterned silicon.

physics.optics↗

arXiv2019

Phase-only transmissive spatial light modulator based on tunable dielectric metasurface

Rapidly developing augmented reality (AR) and 3D holographic display technologies require spatial light modulators (SLM) with high resolution and viewing angle to be able to satisfy increasing customer demands. Currently available SLMs, as well as their performance, are limited by their large pixel sizes of the order of several micrometres. Further pixel size miniaturization has been stagnant due to the persistent challenge to reduce the inter-pixel crosstalk associated with the liquid crystal (LC) cell thickness, which has to be large enough to accumulate the required 2π phase difference. Here, we propose a concept of tunable dielectric metasurfaces modulated by a liquid crystal environment, which can provide abrupt phase change and uncouple the phase accumulation from the LC cell thickness, ultimately enabling the pixel size miniaturization. We present a proof-of-concept metasurface-based SLM device, configured to generate active beam steering with >35% efficiency and large beam deflection angle of 11°, with LC cell thickness of only 1.5 μm, much smaller than conventional devices. We achieve the pixel size of 1.14 μm corresponding to the image resolution of 877 lp/mm, which is 30 times larger comparing to the presently available commercial SLM devices. High resolution and viewing angle of the metasurface-based SLMs opens up a new path to the next generation of near-eye AR and 3D holographic display technologies.

physics.optics↗