We study the spreading of initially localized excitations in one-dimensional disordered granular crystals. We thereby investigate localization phenomena in strongly nonlinear systems, which we demonstrate to differ fundamentally from... more
We study the spreading of initially localized excitations in one-dimensional disordered granular crystals. We thereby investigate localization phenomena in strongly nonlinear systems, which we demonstrate to differ fundamentally from localization in linear and weakly nonlinear systems. We conduct a thorough comparison of wave dynamics in chains with three different types of disorder-an uncorrelated (Anderson-like) disorder and two types of correlated disorders (which are produced by random dimer arrangements)-and for two types of initial conditions (displacement excitations and velocity excitations). We find for strongly precompressed (i.e., weakly nonlinear) chains that the dynamics depend strongly on the type of initial condition. In particular, for displacement excitations, the long-time asymptotic behavior of the second moment m[over ̃]_{2} of the energy has oscillations that depend on the type of disorder, with a complex trend that differs markedly from a power law and which is...
Room temperature optical variable delays are demonstrated using InAs/InP quantum dash semiconductor optical amplifiers (SOAs) at 1.55 μm. A microwave frequency modulated single optical beam allows to demonstrate fast light through the... more
Room temperature optical variable delays are demonstrated using InAs/InP quantum dash semiconductor optical amplifiers (SOAs) at 1.55 μm. A microwave frequency modulated single optical beam allows to demonstrate fast light through the achievement of maximum optical delays of 136 ps at 250 MHz and ˜55 ps at 2 GHz by means of electrical control of the SOA bias current. The group index variation is attributed to enhanced nearly degenerate four wave mixing of this material system as well as population pulsation.
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We propose a structure that allows the splitting of electromagnetic waves with a phase shift of 180° between output signals based on photonic crystals. The structure consists of two parallel coupled-cavity waveguides placed in proximity.... more
We propose a structure that allows the splitting of electromagnetic waves with a phase shift of 180° between output signals based on photonic crystals. The structure consists of two parallel coupled-cavity waveguides placed in proximity. The performance of the splitting structure is theoretically discussed, evaluated by means of finite-difference time-domain method simulations and experimentally demonstrated at microwave frequencies. As both output paths have the same physical length, the two output signals are synchronized, which is very attractive for splitting high-speed optical signals in photonic-crystal-based integrated circuits.
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Periodically structured materials exhibiting simultaneous photonic and phononic band gaps offer unprecedented ways to tailor photon-phonon interactions. A review of the works reported on these materials, sometimes termed" phoxonic... more
Periodically structured materials exhibiting simultaneous photonic and phononic band gaps offer unprecedented ways to tailor photon-phonon interactions. A review of the works reported on these materials, sometimes termed" phoxonic crystals", is presented before ...
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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... more
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 the convergence of the refractive index.
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Teaching is a very complex endeavor. Embedded within this complex environment are issues of power, culture, ethnicity, and race. When teachers and students come together, in the classroom, some of these issues become visible and others... more
Teaching is a very complex endeavor. Embedded within this complex environment are issues of power, culture, ethnicity, and race. When teachers and students come together, in the classroom, some of these issues become visible and others remain invisible. Attempting to make influences on teaching and learning visible is one of the steps toward developing a practice framed by conscientização. Ms. Cook, the teacher of this story, is empowering herself and her students; through critical reflection that serves to deneutralize educational acts by recognizing they are embedded in issues of culture, ethnicity, politics, power, and, race. Classroom based research must be more inclusive and indeed cognizant of the mediating macrostructures that teachers deal with everyday. For example, Goldberg and Muir Welsh describe some of the students as being Latinos. In doing so, they adopts a third person as opposed to a first person view of these students. A first person view can acknowledge a dialectical relationship between race and ethnicity.
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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... more
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 peaks are observed. The separation between the metallic layers is small enough to allow SPPs propagating through the inner interfaces to couple and form an internal SPP, with a different dispersion relation from the outer one and so giving rise to EOT peaks at different frequencies. We propose a relatively simple model to predict the frequencies of those EOT peaks. Internal SPPs show certain unique properties different from the external SPPs: they can give rise to a magnetic response and a negative effective permeability, and the transmission of their EOT peaks increases when no direct line of sight is allowed through the structure. All these findings may be utilized in wavelength tuning of extraordinary optical transmission in subwavelength optics.
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... deterministic studies, as advanced in Sanz-Andres and Navarro-Medina (2010). Figure 3. Left side: photograph of the testing area of the gust wind tunnel showing the reference total pressure probe (1), the semi-spherical stone model... more
... deterministic studies, as advanced in Sanz-Andres and Navarro-Medina (2010). Figure 3. Left side: photograph of the testing area of the gust wind tunnel showing the reference total pressure probe (1), the semi-spherical stone model (2), the total pressure-probe rake (3) and ...
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From November, 2006 to March, 2008 a series of tests were performed onboard a wide variety of trains in order to check their response to pressure waves generated while passing through tunnels. In this communication part of the... more
From November, 2006 to March, 2008 a series of tests were performed onboard a wide variety of trains in order to check their response to pressure waves generated while passing through tunnels. In this communication part of the experimental results are presented, showing the pressure waves generated and focusing on the differences caused by some parameters involved such as train
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ABSTRACT We report on the optomechanical properties of a breathing mechanical mode oscillating at 5.5 GHz in a 1D corrugated Si nanobeam. This mode has an experimental single-particle optomechanical coupling rate of |g o, OM | = 1.8 MHz... more
ABSTRACT We report on the optomechanical properties of a breathing mechanical mode oscillating at 5.5 GHz in a 1D corrugated Si nanobeam. This mode has an experimental single-particle optomechanical coupling rate of |g o, OM | = 1.8 MHz (|g o, OM |/2π = 0.3 MHz) and shows strong dynamical back-action effects at room temperature. The geometrical flexibility of the unit-cell would lend itself to further engineering of the cavity region to localize the mode within the full phononic band-gap present at 4 GHz while keeping high g o, OM values. This would lead to longer lifetimes at cryogenic temperatures, due to the suppression of acoustic leakage.
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ABSTRACT The transmission of a 155 Mbit/s 40 GHz modulated carrier through a 2.2 km SSMF link is demonstrated using a technique for dispersion-tolerant optical harmonic generation of modulated microwave/millimeter-wave signals with... more
ABSTRACT The transmission of a 155 Mbit/s 40 GHz modulated carrier through a 2.2 km SSMF link is demonstrated using a technique for dispersion-tolerant optical harmonic generation of modulated microwave/millimeter-wave signals with simultaneous LO remoting, which employs a single laser and a single dual-drive Mach-Zehnder modulator.
A novel 2 N beams heterodyne optical beamforming architecture based on NxN optical butler matrices. Daniel Madrid, Borja Vidal, Alejandro Martinez, Valentin Polo, Juan Luis Corral, Javier Marti IEEE MTT-S International Microwave Symposium... more
A novel 2 N beams heterodyne optical beamforming architecture based on NxN optical butler matrices. Daniel Madrid, Borja Vidal, Alejandro Martinez, Valentin Polo, Juan Luis Corral, Javier Marti IEEE MTT-S International Microwave Symposium Digest 3, 1945-1948, 2002. ...
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ABSTRACT 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... more
ABSTRACT 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 a spacetime cloak. The proposed method can be generalized to transform other kinds of physical fields beyond the constraint of form-invariance, finding potential applications in other branches such as quantum fluids and graphene electronics.
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Optical Add-Drop Multiplexers (OADMs) allow extracting and inserting data channels in WDM, user access and interconnection applications. A great interest is focused on building small footprint integrated OADMs, which can be achieved using... more
Optical Add-Drop Multiplexers (OADMs) allow extracting and inserting data channels in WDM, user access and interconnection applications. A great interest is focused on building small footprint integrated OADMs, which can be achieved using compact ring resonators (RR). Free spectral range (FSR) values up to some tens of nanometers can be obtained by using RR with small radius or multi-stage configurations,
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ABSTRACT The education of undergraduate mechanical engineering students (UGME) in state of the art technology development for microturbomachinery (MTM) is of importance to ensure the availability of qualified labor satisfying MTM... more
ABSTRACT The education of undergraduate mechanical engineering students (UGME) in state of the art technology development for microturbomachinery (MTM) is of importance to ensure the availability of qualified labor satisfying MTM manufacturer and end used needs ...
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Negative index metamaterial through high-order plasmon resonances on u-shaped nanowires ... Francisco J. Rodríguez-Fortuño, Carlos García-Meca, Rubén Ortuño, Javier Martí and Alejandro Martínez ... Nanophotonics Technology Center,... more
Negative index metamaterial through high-order plasmon resonances on u-shaped nanowires ... Francisco J. Rodríguez-Fortuño, Carlos García-Meca, Rubén Ortuño, Javier Martí and Alejandro Martínez ... Nanophotonics Technology Center, Universidad Politécnica de Valencia, ...
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A simple configuration for achieving a radio frequency transparent 90° hybrid, for broadband QAM wireless systems using silicon photonics is proposed. The device consists of a high Q ring resonator which induces an optical 90° phase shift... more
A simple configuration for achieving a radio frequency transparent 90° hybrid, for broadband QAM wireless systems using silicon photonics is proposed. The device consists of a high Q ring resonator which induces an optical 90° phase shift between two adjacent resonant wavelengths. When these optical carriers are modulated by an RF carrier the resulting device behaves as an RF 90°
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ABSTRACT Sub-micron waveguides and cavities have been shown to produce the confinement of elastic and optical waves in the same devices in order to benefit from their interaction. It has been shown that square and honeycomb lattices are... more
ABSTRACT Sub-micron waveguides and cavities have been shown to produce the confinement of elastic and optical waves in the same devices in order to benefit from their interaction. It has been shown that square and honeycomb lattices are the most suitable to produce simultaneous photonic and phononic band gaps on suspended silicon slabs. The introduction of line defects on such "phoxonic" (or optomechanical) crystals should lead to an enhanced interaction between confined light and sound. In this work we report on the experimental measurements of light guiding through waveguides created in these kinds of two-dimensional photonic crystal membranes. The dimensions of the fabricated structures are chosen to provide a "phoxonic" bandgap with a photonic gap around 1550 nm. For both kinds of lattice, we observe a high-transmission band when introducing a linear defect, although it is observed for TM polarization in the honeycomb lattice and for TE in the square. Using the plane-wave expansion and the finite element methods we demonstrate that the guided modes are below the light line and, therefore, without additional losses beside fabrication imperfections. Our results lead us to conclude that waveguides implemented in honeycomb and square lattice "phoxonic" crystals are a very suitable platform to observe an enhanced interaction between propagating photons and phonons.
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The calibration coefficients of several models of cup and propeller anemometers were analysed. The analysis was based on a series of laboratory calibrations between January 2003 and August 2007. Mean and standard deviation values of... more
The calibration coefficients of several models of cup and propeller anemometers were analysed. The analysis was based on a series of laboratory calibrations between January 2003 and August 2007. Mean and standard deviation values of calibration coefficients ...
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Wave interference is a fundamental manifestation of the superposition principle with numerous applications. Although in conventional optics, interference occurs between waves undergoing different phase advances during propagation, we show... more
Wave interference is a fundamental manifestation of the superposition principle with numerous applications. Although in conventional optics, interference occurs between waves undergoing different phase advances during propagation, we show that the vectorial structure of the near field of an emitter is essential for controlling its radiation as it interferes with itself on interaction with a mediating object. We demonstrate that the near-field interference of a circularly polarized dipole results in the unidirectional excitation of guided electromagnetic modes in the near field, with no preferred far-field radiation direction. By mimicking the dipole with a single illuminated slit in a gold film, we measured unidirectional surface-plasmon excitation in a spatially symmetric structure. The surface wave direction is switchable with the polarization.