http://hdl.handle.net/2117/3217 2013-05-23T10:32:34Z http://hdl.handle.net/2117/19359 Title: A dynamics analysis of antigen specific T cells during brain autoimmunity supports the role of regulatory T cells in disease outcome Authors: Martinez Pasamar, Sara; Abad Adán, Elena; Moreno, Beatriz; Velez de Mendizabal, Nieves; Martinez Forero, Ivan; García Ojalvo, Jordi; Villoslada, Pablo 2013-05-21T10:37:45Z http://hdl.handle.net/2117/19358 Title: Detecting long-range teleconnections in the climate network via ordinal pattern time-series analysis Authors: Deza, Juan Ignacio; Barreiro, Marcelo; Masoller Alonso, Cristina 2013-05-21T10:17:14Z http://hdl.handle.net/2117/19335 Title: Focalization of evanescent beams Authors: Botey Cumella, Muriel; Cheng, Yu Chieh; Herrero Simon, Ramon; Romero García, V.; Pico, R.; Sánchez Morcillo, V. J.; Staliunas, Kestutis Abstract: We predict and show the existence of unlocked evanescent waves in two dimensional periodic structures. In a one dimensional periodic structure an evanescent mode are located either at the center or at the boundary of the Brillouin Zone, and the real part of wave-vectors is locked either to zero or to the modulation vector of the periodicity. However, we report an unexpected observation that this is not the case in 2D or 3D PhCs where "unlocked" complex modes can be predicted. As an interesting consequence, due to their “complex” character, or, equivalently, due to their phase freedom, beams constructed from such evanescent waves can show focalization effects. Indeed, we numerically simulate the propagation of such beams in the bandgap of PhC slabs, and we find significant focalization. 2013-05-17T12:44:37Z http://hdl.handle.net/2117/19257 Title: Spatial noise reduction in broad area semiconductors Authors: Herrero Simon, Ramon; Botey Cumella, Muriel; Pradeep Kumar, Nikhil; Staliunas, Kestutis 2013-05-15T14:13:50Z http://hdl.handle.net/2117/19253 Title: Dispersion management in spatially modulated broad band semiconductors Authors: Herrero Simon, Ramon; Botey Cumella, Muriel; Khumar, N.P.; Staliunas, Kestutis 2013-05-15T13:44:05Z http://hdl.handle.net/2117/18769 Title: Optimal control of high-harmonic generation Authors: Pou, Arnau; Serrat Jurado, Carles 2013-04-11T12:59:10Z http://hdl.handle.net/2117/15758 Title: All optical implementation of a stochastic logic gate using a VCSEL with external optical injection Authors: Perrone, S.; Masoller Alonso, Cristina; Vilaseca Alavedra, Ramon Abstract: We perform numerical simulations of the dynamics of two VCSELs optically coupled in a master-slave configuration. We show that the interplay of nonlinearity and spontaneous emission noise can yield logic behavior, and the emergent outcome of such system is a reliable logic gate. Specifically in our case represents an all-optical logic gate, with the logic input encoded in the strength of the light injected in the slave laser by the master laser, and the fast and robust response decoded from the polarization state of the light emitted by the slave laser. 2012-04-25T11:56:48Z http://hdl.handle.net/2117/15757 Title: Diode laser operation under orthogonal feedback : experiments and theory Authors: Sorrentino, T.; Masoller Alonso, Cristina; Soares, C.; Vidal, I.; Oria, Marcos Abstract: We report experimental and numerical investigations concerning semiconductor lasers emission under polarization-rotated feedback. We experimentally observe that for some semiconductor lasers the weak TM mode does lase even in the absence of TM feedback and we monitor how the TE and TM emissions evolve with the increase of the TM feedback strength. The emission frequency of a semiconductor laser subject to polarization-rotated feedback experiences a shift proportional to the optical power fed back into the laser. We aim to investigate what affects the sensibility of the frequency of semiconductor lasers to polarization-rotated feedback. Experimentally, we measured the proportionality coefficient β between frequency shift and feedback power for different lasers and characterized how it varies with some parameters. Theoretically, we made numerical calculations using a rate equation model, and our results show a critical dependence of the β coefficient on the gain self- and cross-saturation of both modes and the relations between these saturation coefficients. 2012-04-25T11:42:42Z http://hdl.handle.net/2117/11710 Title: New propagation effects in semiconductors in the UV range: inhibition of absorption, negative refraction, anomalous momentum states, sub-wavelength imaging and non-plamonic nanometer-size guided waves Authors: Scalora, M.; Vicenti, M.A.; Roppo, Vito; Foreman, John V.; Hans, Joseph W.; Akozeb, Neset; Bloemer, M.J. Abstract: We discuss new propagation effects in semiconductors at frequencies above the absorption including inhibition of linear absorption using phase-locked harmonic pulses, negative refraction, anomalous momentum states, sub-wavelength imaging and ultrathin, nanometer-size guiding channels. 2011-03-08T12:02:37Z http://hdl.handle.net/2117/11512 Title: Diffractive effects in 1D and 2D gain/loss periodic spatial modulated materials Authors: Herrero Simon, Ramon; Botey Cumella, Muriel; Staliunas, Kestutis Abstract: The propagation of light through materials with periodically modulated gain can present different effects that are analyzed in the paper. The characterization of these gain/loss metamaterials (GLM) with a two-dimensional modulation predicts the mode locked states and effects like non diffractive propagation of beams, superlaminar light propagation regimes and superdiffusion due to angular gain dependence. The last allows the management of amplification and spatial frequency filtering altogether, obtaining amplified, cleaned and focalized beams at the output of these kind of gain modulated materials. The characterization is obtained from the full Maxwell equations using the plane wave expansion (PWE) method, propagation through a given direction is simulated considering beam propagation in the paraxial approximation. 2011-02-23T19:23:49Z http://hdl.handle.net/2117/9853 Title: Nonlinear Light Generation at the High Energy Range of a 3D Opal Film Authors: Martorell Pena, Jordi; Botey Cumella, Muriel; Maymó Camós, Marc; Molinos-Gómez, Alberto; Dorado, Luís A.; Depine, Ricardo A.; Lozano, Gabriel; Mihi, Agustín; Míguez, Hernán 2010-10-20T11:13:57Z http://hdl.handle.net/2117/8710 Title: Lag alternance in unidirectional coupled semiconductor lasers Authors: Tiana Alsina, Jordi; García López, J.H.; Torrent Serra, Maria del Carmen; García Ojalvo, Jordi 2010-09-02T07:36:32Z http://hdl.handle.net/2117/7384 Title: Anomalous group velocity at the high energy range of real 3D photonic nanostructures Authors: Botey Cumella, Muriel; Martorell Pena, Jordi Abstract: We perform a theoretical study on the group velocity for finite thin artificial opal slabs made of a reduced number of layers in the spectral range where the light wavelength is on the order of the lattice parameter. The vector KKR method including extinction allows us to evaluate the finite-size effects on light propagation in the GL and GX directions of fcc close-packed opal films made of dielectric spheres. The group is index determined from the phase delay introduced by the structure to the forwardly transmitted electric field. We show that for certain frequencies, light propagation can either be superluminal —positive or negative— or approach zero depending on the crystal size and absorption. Such anomalous behavior can be attributed to the finite character of the structure and provides confirmation of recently emerged experimental results. 2010-05-26T15:09:32Z http://hdl.handle.net/2117/7292 Title: Gain/loss periodic spatial modulated materials on a wavelength scale Authors: Staliunas, Kestutis; Herrero Simon, Ramon; Vilaseca Alavedra, Ramon Description: We predict self-collimation and superdiffusion of light propagating in materials with periodically modulated gain/loss profile. The modulation is parallel and transverse to the light propagation direction and its periodicity is on the wavelength scale. The self-collimation (or diffraction-free propagation) of the beams is found, which is similar to that observed in photonic crystals. The superdiffusion is also predicted, which means a dependence of the beam amplification on the propagation direction, which results in the spatial frequency filtering of the beams. We justify the predictions by the numerical simulations of the paraxial wave propagation equations. 2010-05-17T14:01:21Z