Carlos García-Meca

• PhD
• Head of photonic and quantum engineering at Navantia

In this work, we study the application of three recent computer vision architectures to the classification of the modulation type of single- and dual-component signals, making emphasis on their usage in a realistic context by simultaneously considering a wide variety of modulations while varying the number of components. In order to do so, we first...

Imaging Cloaked Objects Artist's rendering of a tomographic image of a hexagonal invisibility cloak based on transformation optics. While this type of cloak has been shown to do a good job of hiding objects from scattering cross‐section measurements, as can be seen, diffraction tomography is able to reveal its presence by providing an image of its...

Invisibility cloaks have become one of the most outstanding developments among the wide range of applications in the field of metamaterials. So far, most efforts in invisibility science have been devoted to achieving practically realizable cloak designs and to improving the effectiveness of these devices in reducing their scattering cross‐section (...

Invisibility cloaks have become one of the most outstanding developments among the wide range of applications in the field of metamaterials. So far, most efforts in invisibility science have been devoted to achieving practically realizable cloak designs and to improving the effectiveness of these devices in reducing their scattering cross-section (...

Nanomaterials with very specific features (purity, colloidal stability, composition, size, shape, location…) are commonly requested by cutting-edge technologic applications, and hence a sustainable process for the mass-production of tunable/engineered nanomaterials would be desirable. Despite this, tuning nano-scale features when scaling-up the pro...

Metallic apertures remain one of the most intensively investigated optical structures due to their rich behavior. This encompasses physical phenomena such as Bragg scattering, surface plasmons, or localized modes, offering great potential for many applications in the growing fields of nanophotonics and plasmonics. Here, we show that isolated metall...

Supersymmetry is a conjectured symmetry between bosons and fermions aiming at solving fundamental questions in string and quantum field theory. Its subsequent application to quantum mechanics led to a ground-breaking analysis and design machinery, later fruitfully extrapolated to photonics. In all cases, the algebraic transformations of quantum-mec...

Plasmonic technology promises to unfold new advanced on-chip functionalities with direct applications in photovoltaics, light matter interaction and the miniaturization of optical interconnects at the nanoscale. In this scenario, it is crucial to efficiently drive light to/from plasmonic devices. However, typically-used plasmonic wires introduce pr...

Recently, a novel Photonic‐Integrated Circuit (PIC) paradigm based on the use of a new kind of ultra‐directive, low‐loss, highly efficient and broadband silicon nanoantenna has enabled the first demonstration of an on‐chip wireless interconnect, with potential applications in reconfigurable networks and lab‐on‐a‐chip systems. Despite the fact that...

Originally emerged within the context of string and quantum field theory, and later fruitfully extrapolated to photonics, the algebraic transformations of quantum-mechanical supersymmetry were conceived in the space realm. Here, we introduce a paradigm shift, demonstrating that Maxwell's equations also possess an underlying supersymmetry in the tim...

Photonic integrated circuits (PICs) promise to open new avenues in high-performance computing, biosensing or optical beamforming, amongst others. Current PICs rely on the use of guided interconnects, hampering the creation of flexible and reconfigurable networks-on-a-chip and preventing the far-field light-matter interaction for many sensing applic...

We experimentally demonstrate an all-silicon nanoantenna-based micro-optofluidic cytometer showing a combination of high signal-to-noise ratio (SNR) > 14 dB and ultra-compact size. Thanks to the ultra-high directivity of the antennas (>150), which enables a state-of-the-art sub-micron resolution, we are able to avoid the use of the bulky devices ty...

Flow cytometry currently represents a fundamental source of progress in biomedical research and chemical diagnosis, opening new means in the treatment of diseases such as AIDS or cancer. Via this technique, flows of live cells or biotargets can be dynamically analysed via the use of optical-or impedance-based devices. In this work, an ultra-compact...

Supersymmetry (SUSY) was originally introduced within the context of string and quantum field theory as a necessary ingredient to unify the basic interactions of nature (strong, electroweak, and gravitational). Despite the fact that there is no experimental evidence of SUSY in nature, the mathematical framework of SUSY has been profitably extended...

Supersymmetry (SUSY) has recently emerged as a tool to design unique optical structures with degenerate spectra. Here, we study several fundamental aspects and variants of one-dimensional SUSY in axially symmetric optical media, including their basic spectral features and the conditions for degeneracy breaking. Surprisingly, we find that the SUSY d...

Photonic integrated circuits (PICs) promise to open new avenues in high-performance computing, biosensing or optical beamforming, amongst others. Current PICs rely on the use of guided interconnects, hampering the creation of flexible and reconfigurable networks-on-a-chip and preventing the far-field light-matter interaction for many sensing applic...

Aimed to improve the flexibility of optical network-on-a-chip topologies, unguided optical interconnects using plasmonic nanoantennas or dielectric phased arrays have been proposed. However, the bulky footprints of the latter, and both the low directivity figures and high losses of the former, together with complicated excitation schemes, limit the...

Multi-core fibers (MCFs) have sparked a new paradigm in optical communications and open new possibilities and applications in experimental physics and other fields of science, such as biological and medical imaging. In many of these cases, ultra-short pulse propagation is revealed as a key factor that enables us to exploit the full potential of thi...

Photonic integrated circuits are developing as key enabling components for high-performance computing and advanced network-on-chip, as well as other emerging technologies such as lab-on-chip sensors, with relevant applications in areas from medicine and biotechnology to aerospace. These demanding applications will require novel features, such as dy...

Invisibility in a diffusive-light-scattering medium has been recently demonstrated by employing a scattering-cancellation core-shell cloak. Unlike nondiffusive cloaks, such a device can be simultaneously macroscopic, broadband, passive, polarization independent, and omnidirectional. Unfortunately, it has been verified that this cloak, as well as mo...

In this paper, we evaluate experimentally and model theoretically the intra- and inter-core crosstalk between the polarized core modes in single-mode multi-core fiber media including temporal and longitudinal birefringent effects. Specifically, extensive experimental results on a four-core fiber indicate that the temporal fluctuation of fiber biref...

We present an alternative version of transformation optics that allows us to mold the flow of light without rotating or scaling the electromagnetic fields. The resulting media experience unusual force densities, are nonreciprocal, and exhibit loss or gain. Because of these singular features, a variety of effects and devices unreachable by standard...

Recently, the introduction of transformation thermodynamics has provided a way to design thermal media that alter the flow of heat according to any spatial deformation, enabling the construction of novel devices such as thermal cloaks or concentrators. However, in its current version, this technique only allows static deformations of space. Here, w...

Metallic nano-particles support localized surface plasmon resonances (LSPRs) associated with the interaction of free electrons on the metal surface and incoming light. LSPRs can enhance the electric field by several orders of magnitude while confining it to sub-wavelength regions. Recently, we showed that arrays of closely spaced nano-rings can als...

We present a way of exciting surface plasmon polaritons along non-patterned metallic surfaces by means of a flat squeezing slab designed with transformation optics. The slab changes the dispersion relation of incident light, enabling evanescent coupling to propagating surface plasmons. Unlike prism couplers, the proposed device does not introduce r...

A recently developed technique known as analogue transformation acoustics has allowed the extension of the transformational paradigm to general spacetime transformations under which the acoustic equations are not form invariant. In this paper, we review the fundamentals of analogue transformation acoustics and show how this technique can be applied...

We apply a homogenization process to the acoustic velocity potential wave equation. The study of various examples shows that the resulting effective properties are different from those of the homogenized pressure wave equation for the same underlying acoustic parameters. A careful analysis reveals that a given set of inhomogeneous parameters repres...

In this work, we present a metamaterial working at terahertz frequencies made over a flexible polypropylene substrate. The experimental measurements, in accordance with the numerical calculations, show the metamaterial reliance on the impinging electric field polarization. The structure’s symmetry yields purely electrical resonant responses elimina...

A recently proposed analogue transformation method has allowed the extension of transformation acoustics to general space–time transformations. We analyze here in detail the differences between this new analogue transformation acoustics (ATA) method and the standard one (STA). We show explicitly that STA is not suitable for transformations that mix...

We present a method that enables the implementation of full three-dimensional (3D) transformation media with minimized anisotropy. It is based on a special kind of shape-preserving mapping and a subsequent optimization process. For sufficiently smooth transformations, the resulting anisotropy can be neglected, paving the way for practically realiza...

Using the idea of analogue spacetimes, we derive an "analogue transformation acoustics" formalism that naturally allows the use of transformations mixing space and time or involving moving fluids, both of which were impossible with the standard approach. We illustrate the use of the method by designing acoustic versions of a dynamic compressor and...

Over the last decade, negative index media have attracted much attention due to their potential applications, especially the possibility of constructing superlenses. However, achieving high-performance negative-index metamaterials at visible frequencies, where this kind of media could find many applications, still remains a challenge. In this artic...

Transformation optics has shaped up a revolutionary electromagnetic design paradigm, enabling scientists to build astonishing devices such as invisibility cloaks. Unfortunately, the application of transformation techniques to other branches of physics is often constrained by the structure of the field equations. We develop here a complete transform...

Supplementary Information

Light-matter interaction at optical frequencies is mostly mediated by the electric component of the electromagnetic field, being the response to the magnetic component usually negligible. Recently, it has be shown that properly engineered metallic nanostructures can provide a magnetic response at optical frequencies originated from real or virtual...

Transformation optics specializes in the engineering of advanced optical devices, and in combination with differential geometry it allows to control electromagnetic fields with artificial media in an unprecedented manner. In this work, we model transformation optics in an inherently covariant fashion starting with a fundamental Lagrangian function....

Optical measurements of the transmission spectra through nanofabricated planar arrays of silver u-shaped nanowires on a silicon substrate resonating at infrared frequencies are performed. Good agreement with the numerically simulated surface plasmon standing wave resonances supported by the structures is found. Such resonances exhibit field enhance...

In this work, we show that closely-spaced gold nanohoops periodically distributed in a square lattice can provide a strong magnetic response in the near infrared regime when illuminated under normal incidence (perpendicular to the structure plane). Therefore, just a single metallic layer is needed to achieve the magnetic activity. A key point to ac...

We study the electromagnetic behavior of a structure consisting of coupled aluminum nanodisks on a silicon waveguide at telecom wavelengths. Numerical simulations show that the fundamental TE-like waveguide mode excites a localized magnetic plasmon resonance between adjacent nanodisks with suitable dimensions, leading to transmission dips. For a su...

Over the last decade, metamaterials have attracted a great interest thanks to their potential to expand the range of electromagnetic properties found in natural materials. In particular, the possibility of achieving negative refractive index media (NIM) enables us to implement superlenses and optical storing devices. Since the first experimental de...

We use a combination of conformal and quasi-conformal mappings to engineer isotropic electromagnetic devices that modify the omnidirectional radiation pattern of a point source. For TE waves, the designed devices are also non-magnetic. The flexibility offered by the proposed method is much higher than that achieved with conformal mappings. As a res...

An effective negative refractive index (NRI) is demonstrated and experimentally verified for the first two propagation bands of a fishnet-like metamaterial at millimeter-wave frequencies. The dual-band NRI behavior is achieved by engineering the diffraction order ( ± 1 , ± 1 ) associated with the internal mode supported between holey layers to corr...

Some interesting optical instruments such as the Eaton lens and the invisible sphere require singularities of the refractive index for their implementation. We show how to transmute those singularities into harmless topological defects in anisotropic media without the need for anomalous material properties.

We study the reflection properties of squeezing devices based on transformation optics. An analytical expression for the angle-dependent reflection coefficient of a generic three-dimensional squeezer is derived. In contrast with previous studies, we find that there exist several conditions that guarantee no reflections so it is possible to build tr...

We experimentally demonstrate a low-loss multilayered metamaterial exhibiting a double-negative refractive index in the visible spectral range. To this end, we exploit a second-order magnetic resonance of the so-called fishnet structure. The low-loss nature of the employed magnetic resonance, together with the effect of the interacting adjacent lay...

We have studied the relationship between internal-surface plasmon polaritons and negative permeability in cascaded patterned metallic layers. By properly selecting the dielectric thicknesses of the multilayer structure, the negative effective index can broaden which could be of potential use in the design of metamaterials. The excitations of claddi...

By exploiting the concept of internal surface plasmon polariton (I-SPP) resonances, which appear at nonsingle metallic film stacks, we have designed a metamaterial showing a negative effective index within a large frequency bandwidth. The designed structure consists of an arrangement of several fishnet layers. By properly adjusting the lattice and...

We demonstrate that the resonance of metallic split-ring resonators can interact with Bragg phase interference effects in a surrounding one-dimensional photonic crystal in such a way that a zero-bandwidth mode arises within the photonic band gap of the crystal. The band can also be designed to exhibit forward or backward slow-light propagation. We...

Exploiting the concept of internal surface plasmon polariton (I-SPP) resonances, which appear at non-single metallic film stacks, we have designed a metamaterial showing a negative effective refractive index within a large bandwidth. The designed structure consists of an arrangement of several fishnet layers. By properly adjusting the lattice const...

We prove theoretically that it is possible to build embedded reflectionless squeezers/expanders using transformation optics. We illustrate the potential of this finding by proposing an application in which the squeezer is a key element: an ultra-short perfect coupler for high-index nanophotonic waveguides.

We study numerically and theoretically the optical transmission of nanostructured gold films embedded in dielectric claddings. We show how multiple transmission peaks appear as the claddings thickness increases. These transmission peaks come not only from surface plasmon polariton excitations but also from the excitation of Fabry-Perot modes sustai...

An experimental study is made of the enhanced optical transmission of nanostructured gold films in the midinfrared region. Results indicate that the excitation of surface plasmon polaritons due to periodicity plays a fundamental role in producing extraordinary optical transmission. The influence of the surrounding claddings, hole shape, and periodi...

We propose the use of closely packed deep-subwavelength plasmonic coaxial waveguides that support backward propagating modes at visible frequencies, analogous to those in planar metal–insulator–metal geometries, as negative-index metamaterials. We show through simulation that the propagation properties of the metamaterial are determined by the disp...

In this letter we introduce the concept of optical security marks based on photonic metamaterials. We propose that a metamaterial with strong negative magnetic activity in the visible wavelength regime can be used to create a security mark that can be incorporated in any object to ensure its authenticity. The sophisticated nanofabrication processes...

We show that a second-order magnetic resonance present in the fishnet metamaterial can be enhanced so as to achieve simultaneous negative permittivity and permeability in the visible range. The double-negative behavior leads to reduced losses in this particular fishnet metamaterial. We also study the stacking of several functional layers, verifying...

We study under which conditions extraordinary optical transmission (EOT) structures can be used to build negative refractive index media. As a result, we present a metamaterial with superimposed EOT and negative index at visible wavelengths. The tailoring process starting from a simple hole array until achieving the negative index is detailed. We a...

We apply the concept of slow surface-plasmon polariton standing-wave resonances to model the plasmon resonances which exist on split-ring resonators (U-shaped nanowires) forming the unit cell of a metamaterial at infrared frequencies. We compare the expected resonances predicted by the model with full electrodynamic three-dimensional simulations of...

We study analytically and numerically the far-field extraordinary optical transmission (EOT) through double-layer metallic grating structures patterned with subwavelength hole arrays. In addition to EOT phenomena due to the well-known surface plasmon polaritons (SPPs) on the outer surfaces such as those on a single layer hole array, further EOT pea...

Future ultracompact photonic integrated circuits (PICs) will rely on high-index-contrast dielectric materials, which permit a strong confinement of the optical field in the diffraction limit as well as low propagation losses. This is the case of PICs implemented on a silicon-on-insulator (SOI) platform. To achieve confinement beyond the diffraction...

Second- and third-order standing-wave slow-plasmon resonances on gold u-shaped nanowires are modelled and used to achieve a negative index metamaterial at far infrared frequencies which can be stacked showing backward phase propagation.

A two-dimensional photonic-crystal engineered to possess a refractive index equal to minus one at a certain frequency is used as a flat superlens. Subwavelength imaging (image size below half a wavelength) is observed both in the near-field and far-field regimes when the interface with air is properly terminated to support surface states with even...

We present a structure exhibiting a negative index of refraction at visible or near infrared frequencies using a single metal layer. This contrasts with recently developed structures based on metal-dielectric-metal composites. The proposed metamaterial consists of periodically arranged thick stripes interacting with each other to give rise to a neg...