Person: Martínez Matos, Óscar
Universidad Complutense de Madrid
Faculty / Institute
Now showing 1 - 10 of 35
- PublicationInfluence of the electron-lattice coupling for Cr^3^+ ions in Nb^5^+ site into congruent co-doped LiNbO_3: Cr^3^+: ZnO crystal(Pergamon-Elsevier Science LTD, 2003-08) Martínez Matos, Óscar; Torchia, Gustavo Adrián; Vaveliuk, Pablo; Tocho, Jorge OmarThis paper shows the important role that plays the electron-lattice coupling to represent correctly the energy levels of Cr^3^+ ions in Nb^5^+ site into congruent LiN_bO_3 crystals doped with 5.3% of ZnO. Racah's parameters: and crystal field intensity were determined and the Tanabe–Sugano's diagram was constructed. The characteristics of the absorption and emission spectra of Cr^3^+ ions in Nb^5^+ site have been explained in terms of the Configurational Co-ordinate model in the harmonic approximation. Huang–Rhys parameter, S=3.5 and the breathing phonon energy, are also reported in this work. Different values of breathing phonon for Cr^3^+ in Nb^5^+ site than in Li+ site could explain the higher luminescent quantum efficiency of Cr^3^+ ions located in Nb^5^+ site in LiN_bO_3 crystals.
- PublicationDiffusion study in tailored gratings recorded in photopolymer glass with high refractive index species(American Institute of Physics, 2007-10-01) Martínez Matos, Óscar; Calvo Padilla, María Luisa; Rodrigo Martín-Romo, José Augusto; Cheben, Pavel; Monte Muñoz de la Peña, Francisco delWe report results on the temporal evolution of the diffraction efficiency of volume holographic gratings recorded in a photopolymer glass incorporating Zr-based high refractive index species (HRIS) at molecular level. We record high spatial frequency gratings in this material with diffraction efficiencies near 100%. A two-component diffusion model is introduced for the evolution of refractive index modulation in darkness. Diffusion parameters for the Zr-based HRIS and monomer components have been determined. Codirectional diffusion of both components is demonstrated. The results show the feasibility for tailoring in this photomaterial holographic gratings with high diffraction efficiency over a wide range of spatial frequencies. (C) 2007 American Institute of Physics.
- PublicationHelix-shaped tractor and repulsor beams enabling bidirectional optical transport of particles en masse(OSA Publishing, 2022-11-01) Rodrigo Martín-Romo, José Augusto; Martínez Matos, Óscar; Alieva, Tatiana KrasheninnikovaThree-dimensional programmable transport of micro/nano-particles can be straightforwardly achieved by using optical forces arising from intensity and phase gradients of a structured laser beam. Repulsor and tractor beams based on such forces and shaped in the form of a curved trajectory allow for downstream and upstream (against light propagation) transportation of particles along the beams, respectively. By using both types of beams, bidirectional transport has been demonstrated on the example of a circular helix beam just by tuning its phase gradient. Specifically, the transport of a single particle along a loop of the helix has been reported. However, the design and generation of helix-shaped beams is a complex problem that has not been completely addressed, which makes their practical application challenging. Moreover, there is no evidence of simultaneous transport of multiple particles along the helix trajectory, which is a crucial requisite in practice. Here, we address these challenges by introducing a theoretical background for designing helix beams of any axial extension, shape, and phase gradient that takes into account the experimental limitations of the optical system required for their generation. We have found that only certain phase gradients prescribed along the helix beam are possible. Based on these findings, we have experimentally demonstrated, for the first time, helix-shaped repulsor and tractor beams enabling programmable bidirectional optical transport of particles en masse. This is direct evidence of the essential functional robustness of helix beams arising from their self-reconstructing character. These achievements provide new insight into the behavior of helix-shaped beams, and the proven technique makes their implementation easier for optical transport of particles as well as for other light-matter interaction applications.
- PublicationCurve-shaped ultrashort laser pulses with programmable spatiotemporal behavior(Optica Publishing Group, 2023-03-08) Franco Rodríguez, Enar; Martínez Matos, Óscar; Rodrigo Martín Romo, José AugustoStructured ultrashort laser pulses with controlled spatiotemporal properties are emerging as a key tool for the study and application of light-matter interactions in different fields such as microscopy, time-resolved imaging, laser micromachining, particle acceleration, and attosecond science. In practice, a structured ultrashort pulse focused along a target trajectory with controlled pulse dynamics is required, e.g., to set the trajectory and velocity of the resulting intensity peak. Here, to address this challenging problem, we present a technique and experimental setup that allows straightforward engineering of structured ultrashort laser pulses with control of their spatiotemporal properties enabling tailored pulse propagation dynamics along the target trajectory. Our theoretical framework describes the design and control of this kind of curve-shaped laser pulse in terms of the curve geometry and phase prescribed along it. We have derived a closed-form expression that describes the interplay between the curve geometry and prescribed phase governing the pulse dynamics, including the temporal behavior of the pulse peak intensity while preserving the pulse duration. The theoretical results and the corresponding numerical simulations allow us to analyze the pulse dynamics on the example of femtosecond curve-shaped vortex pulses, including contour-shaped pulses created to follow the outline of objects at micrometer scale. The experimental results demonstrate the generation of these structured ultrashort pulses. These findings could pave the way for the next generation of ultrashort laser-based optical tools for the study and control of light-matter interactions.
- PublicationExperimental detection of the optical Pendellösung effect(American Physical Society, 2006-08-25) Martínez Matos, Óscar; Calvo Padilla, María Luisa; Cheben, Pavel; Monte Muñoz de la Peña, Francisco del; Rodrigo Martín-Romo, José AugustoWe report observations of periodic oscillatory behavior of the angular selectivity, near the Bragg angle, in volume holographic gratings recorded in a new photopolymerizable glass with high refractive index modulation. We have detected the presence of overmodulation in the intensity distribution of the first diffraction order. The results reported here were achieved by incorporating in the photopolymerizable sol-gel glass zirconium-based high refractive index species at the molecular level. This is the first time that this effect is observed for light diffraction in an amorphous material.
- PublicationA volume holographic sol-gel material with large enhancement of dynamic range by incorporation of high refractive index species(WILEY-V C H VERLAG GMBH, 2006-08-04) Monte Muñoz de la Peña, Francisco del; Martínez Matos, Óscar; Rodrigo Martín-Romo, José Augusto; Calvo Padilla, María Luisa; Cheben, PavelImproved performance of volume holographic sol-gel materials-refractive index modulations in the 10^2 range, diffraction efficiencies near 100 %, and low levels of noise scattering-are reported that arise from the incorporation of Zr-based high refractive index species capable of diffusing from dark to bright fringes of the interference pattern (see figure).
- PublicationEffect of ABCD transformations on beam paraxiality(The Optical Society Of America, 2011-12-19) Martínez Matos, Óscar; Vaveliuk, PabloThe limits of the paraxial approximation for a laser beam under ABCD transformations is established through the relationship between a parameter concerning the beam paraxiality, the paraxial estimator, and the beam second-order moments. The applicability of such an estimator is extended to an optical system composed by optical elements as mirrors and lenses and sections of free space, what completes the analysis early performed for free-space propagation solely. As an example, the paraxiality of a system composed by free space and a spherical thin lens under the propagation of Hermite-Gauss and Laguerre-Gauss modes is established. The results show that the the paraxial approximation fails for a certain feasible range of values of main parameters. In this sense, the paraxial estimator is an useful tool to monitor the limits of the paraxial optics theory under ABCD transformations.
- PublicationFemtosecond spatial pulse shaping at the focal plane(The Optical Society Of America, 2013-10-21) Martínez Matos, Óscar; Vaveliuk, Pablo; González Izquierdo, Jesús; Loriot, VincentSpatial shaping of ultrashort laser beams at the focal plane is theoretically analyzed. The description of the pulse is performed by its expansion in terms of Laguerre-Gaussian orthonormal modes. This procedure gives both a comprehensive interpretation of the propagation dynamics and the required signal to encode onto a spatial light modulator for spatial shaping, without using iterative algorithms. As an example, pulses with top-hat and annular spatial profiles are designed and their dynamics analyzed. The interference of top-hat pulses is also investigated finding potential applications in high precision pump-probe experiments (without using delay lines) and for the creation of subwavelength ablation patterns. In addition, a novel class of ultrashort pulses possessing non-stationary orbital angular momentum is also proposed. These exotic pulses provide additional degrees of freedom that open up new perspectives in fields such as laser-matter interaction and micro-machining.
- PublicationCaustics, catastrophes, and symmetries in curved beams(American Physical Society, 2015-09-28) Vaveliuk, Pablo; Lencina, Alberto; Rodrigo Martín-Romo, José Augusto; Martínez Matos, ÓscarIn this paper, a meaningful classification of optical caustic beams in two dimensions is presented. It is demonstrated that the phase symmetry of the beam's angular spectrum governs the optical catastrophe, which describes the wave properties of ray singularities, for cusp (symmetric phase) and fold (antisymmetric phase) caustics. In contrast to the established idea, the caustic classification arises from the phase symmetry rather than from the phase power, thus breaking the commonly accepted concept that fold and cusp caustics are related to the Airy and Pearcey functions, respectively. Nevertheless, the role played by the spectral phase power is to control the degree of caustic curvature. These findings provide straightforward engineering of caustic beams by addressing the spectral phase into a spatial light modulator or glass plate.
- PublicationArrayed waveguide grating based on group-index modification(IEEE - Inst. Electrical Electronics Engineers Inc., 2006-03) Martínez Matos, Óscar; Calvo Padilla, María Luisa; Cheben, Pavel; Janz, Siegfried; Rodrigo Martín-Romo, José Augusto; Xu, Dan-Xia; Delâge, AndréThe authors propose a new wavelength-dispersive principle based on waveguide group-index modification and apply this principle in a new type of arrayed waveguide dispersive element based on modified group index. The element is composed by an array of waveguides consisting of two sections with different group indexes. We deduce the applicable dispersion formula and demonstrate that the group-index modification can be used for controlling or enhancing device wavelength dispersion. Two device examples are provided. First, dispersive properties of a waveguide array with silicon on insulator (SOI) straight waveguides with group index modified by waveguide widening are calculated. Then, the authors show that by placing the element with modified group index in a phased array of a conventional arrayed waveguide grating (AWG) device, the dispersive properties of the AWG are markedly enhanced. Dispersion-enhancement factor of up to 60 is calculated for a compact demultiplexer designed for SOI platform with group index modified by photonic-bandgap effect.