Advanced search

Knowledge area

27 results, page 1 of 3

Optical Spectrometer with Acousto-Optical Dynamic Grating for Guillermo Haro Astrophysical Observatory

ALEXANDER SHCHERBAKOV Adán Omar Arellanes Bernabe Vahram Chavushyan (2013)

Optical spectrometer of the Guillermo Haro astrophysical observatory (Mexico) realizes investigations in the visible and near-infrared range 350 - 800 nm and exploits mechanically removable traditional static diffraction gratings as dispersive elements. There is a set of the static gratings with slit-densities 150 - 600 lines/mm and optical apertures 9 cm × 9 cm that provide the first order spectral resolution from 0.8 to 3.2 Å/pixel, respectively. However, the needed mechanical manipulations, namely, replacing the static diffraction gratings with various resolutions and following recalibration of spectrometer within studying even the same object are practically inconvenient and lead to wasting rather expensive observation time. We suggest exploiting an acousto-optical cell, i.e. the dynamic diffraction grating tunable electronically, as dispersive element in that spectrometer. Involving the acousto-optical technique, which can potentially provide electronic control over the spectral resolution and the range of observations, leads to eliminating the above-mentioned demerits and improving the efficiency of analysis


Optical spectrometer Guillermo Haro astrophysical observatory Acousto-Optical Dynamic Grating CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

Transmission function of collinear acousto-optical interaction occurred by acoustic waves of finite amplitude

ALEXANDER SHCHERBAKOV Adán Omar Arellanes Bernabe (2013)

New physical aspects of collinear acousto-optical interaction, occurred by acoustic waves of finite amplitude, are revealed and analyzed in crystalline materials exhibiting moderate linear acoustic losses. The analysis is performed in the regime of continuous traveling waves allowing a specific mechanism of the acousto-optic nonlinearity. Our consideration has shown that such nonlinearity together with linear acoustic losses is able to affect the transmission function inherent in collinear interaction. In particular, the mere presence of linear acoustic losses by themselves leads to broadening the width of the transmission function beginning already from very low levels of the applied acoustic power. Moreover, the transmission function exhibits a marked and quasi-periodical dependence on the applied acoustic power density, and that periodicity is governed by the linear acoustic losses. As a result, the transmission function can be significantly narrowed near isolated points at the cost of decreasing the interaction efficiency. These novelties related to collinear acousto-optical interaction accompanied by moderate linear acoustic losses have been studied and confirmed experimentally with an advanced acousto-optical cell based on calcium molybdate (CaMoO4) single crystal and controlled by acoustic waves of finite amplitude. © 2013 Optical Society of America


Dynamic gratings Nonlinear optics Parametric processes Acousto-optical devices CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

Transmission function of the collinear acousto-optical filter controlled by acoustic waves of the finite amplitude

ALEXANDER SHCHERBAKOV Adán Omar Arellanes Bernabe (2013)

An opportunity to exploit specific mechanisms of the acousto-optic nonlinearity to regulate performances of the collinear acousto-optical filter, realizing the sequential spectrum analysis of optical signals, is considered. This possibility is theoretically analyzed and experimentally confirmed with an advanced filter based on calcium molybdate (CaMoO4) single-crystal with a 15-μs time-aperture. It is able to operate over red and near-infrared light at relatively low radio-wave frequencies providing almost lossless regime for controlling acoustic waves of the finite amplitude. Under certain conditions, the transmission function of electronically tunable filter exhibits a marked dependence on the applied acoustic power density, and as a result, one can significantly squeeze the transmission function, i.e., improve the spectral resolution of this filter at the cost of decreasing the efficiency of the device partially. The identified and observed non-linear effect makes possible varying the performance data of similar advanced collinear acousto-optical filter governed by external signals of the finite amplitude. © 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.OE.52.6.064001]


Collinear acousto-optical interaction Optical filter Acousto-optical nonlinearity Transmission function Spectral resolution Waves of the finite amplitude CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

High-Resolution Broadband Millimeter-Wave Astrophysical Spectrometer with Triple Product Acousto-Optical Processor

MIGUEL CHAVEZ DAGOSTINO ALEXANDER SHCHERBAKOV Adán Omar Arellanes Bernabe Vahram Chavushyan (2013)

An advanced conceptual design of a high-bit-rate triple product acousto-optical processor is presented that can be applied in a number of astrophysical problems. We briefly describe the Large Millimeter Telescope as one of the potential observational infrastructures where the acousto-optical spectrometer can be successfully used. A summary on the study of molecular gas in relatively old (age > 10 Myr) disks around main sequence stars is provided. We have identified this as one of the science cases in which the proposed processor can have a big impact. Then we put forward triple product acousto-optical processor is able to realize algorithm of the space-and-time integrating, which is desirable for a wideband spectrum analysis of radio-wave signals with an improved resolution providing the resolution power of about 105 - 106 . It includes 1D-acousto-optic cells as the input devices for a 2D-optical data processing. The importance of this algorithm is based on exploiting the chirp Z-transform technique providing a 2D-Fourier transform of the input signals. The system produces the folded spectrum, accumulating advantages of both space and time integrating. Its frequency bandwidth is practically equal to the bandwidth of transducers inherent in acousto-optical cells. Then, similar processor is able to provide really high frequency resolution, which is practically equal to the reciprocal of the CCD-matrix photo-detector integration time. Here, the current state of developing the triple product acousto-optical processor in frames of the astrophysical instrumentation is shortly discussed.


Astrophysical Instrumentation Radio-Astronomy Millimeter-Wave Spectrometer Space-and-Time Integrating Acousto-Optical Devices Optical Processing System CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

Impurity-Related Nonlinear Optical Absorption in Delta-Doped Quantum Rings


Using a variational procedure within the efective mass approximation, we have calculated the hydrogenic impurity binding energy as well as the impurity-related nonlinear optical absorption in a single quantum ring with axia ln-type delta-doping.

Producción Científica de la Universidad Autónoma de Zacatecas UAZ



Collision of propagating vortices embedded within Airy beams


We present the engineered collision of two curvilinear propagating optical vortices each embedded in the main lobe of an Airy beam. Two cases are analyzed: same and opposite unitary topological vortex charge. We observed experimentally that in the first case the main vortices repel each other and remain separated after the collision. On the contrary, in the second case an annihilation of the main vortices occurs. Our experimental observations are reinforced by numerical simulations showing that the conservation of topological charge dictates the vortex dynamics.



Selective photodeposition of zinc nanoparticles on the core of a single-mode optical fiber


An experimental and theoretical study about selective photodeposition of metallic zinc nanoparticles onto an optical fiber end is presented. It is well known that metallic nanoparticles possess a high absorption coefficient and therefore trapping and manipulation is more challenging than dielectric particles. Here, we demonstrate a novel trapping mechanism that involves laser-induced convection flow (due to heat transfer from the zinc particles) that partially compensates both absorption and scattering forces in the vicinity of the fiber end. The gradient force is too small and plays no role on the deposition process. The interplay of these forces produces selective deposition of particles whose size is directly controlled by the laser power. In addition, a novel trapping mechanism termed convective-optical trapping is demonstrated.


Fiber optics, infrared Photothermal effects Optical tweezers or optical manipulation Laser trapping CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

Amorphous silicon-liquid crystals device forphotonic applications


We demonstrate that an hydrogenated amorphous silicon (a:SiH)-liquid crystals hybrid device could be used for the recording of high resolution (0.8-2 µm) dynamic holograms. A maximum diffraction efficiency of 3.3% was obtained at low power (1.5 mW) He-Ne laser. The nonlinear refractive index change at 0.6 W/cm2 is n2~1x10−2 cm2 /W, although small compared to that obtained in dye-doped liquid crystal, is equal to the reported in pure liquid crystal although with much higher power density (~50 W/cm2 ). The device operates in the red to near-infrared part of the spectrum which makes it attractive due to its potential applications in telecommunications and military applications.


Nonlinear optics Diffraction gratings Holography Liquid crystals CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA

Thermodynamic, structural and dynamic properties of ionic liquids [C4mim][CF3COO]

, [C4mim][Br]

in the condensed phase, using molecular simulations

Joel Sánchez-Badillo JORGE LOPEZ LEMUS Marco Gallo Ricardo Guirado (2019)

Articulo de investigacion

In this work a series of thermodynamic, structural, and dynamical properties for the 1-butyl-3-methylimidazolium trifluoroacetate ([C4mim][CF3COO]) and 1-butyl-3-methylimidazolium bromide, ([C4mim][Br]) ionic liquids (ILs) were calculated using Non-polarizable Force Fields (FF), parameterized using a methodology developed previously within the research group, for condensed phase applications. Properties such as the Vapor-Liquid Equilibrium (VLE) curve, critical points (ρc, Tc), Radial, Spatial and Combined Distribution Functions and self-diffusion coefficients were calculated using Equilibrium Molecular Dynamics simulations (EMD); other properties such as shear viscosities and thermal conductivities were calculated using Non-Equilibrium Molecular Dynamics simulations (NEMD). The results obtained in this work indicated that the calculated critical points are comparable with those available in the literature. The calculated structural information for these two ILs indicated that the anions interact mainly with hydrogen atoms from both the imidazolium ring and the methyl chain; the bromide anion displays twice the hydrogen coordination number than the oxygen atoms from the trifluoroacetate anion. Furthermore, Non-Covalent interactions (NCI index), determined by DFT calculations, revealed that some hydrogen bonds in the [C4mim][Br] IL displayed similar strength to those in the [C4mim][CF3COO] IL, in spite of the shorter O−–H distances found in the latter IL. The majority of the calculated transport properties presented reasonable agreement with the experimental available data. Nonetheless, the self-diffusion coefficients determined in this work are under-estimated with respect to experimental values; however, by escalating the electrostatic atomic charges for the anion and cation to ±0.8e, only for this property, a remarkable improvement was obtained. Experimental evidence was recovered for most of the calculated properties and to the best of our knowledge, some new predictions were done mainly in thermodynamic states where data are not available. To validate the FF, developed previously within the research group, dynamic properties were also evaluated for a series of ILs such as [C4mim][PF6], [C4mim][BF4], [C4mim][OMs], and [C4mim][NTf2] ILs.


ionic liquid molecular dynamics force field CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA

An experimental approach to discrete dynamical systems with Mathematica

Michael Studer (2021)

Experiment with discrete time dynamical systems, may represent an important educational resource in the investigation of the properties of dynamical systems and their potential applications to disciplines such as economics. As an illustration of this possibility teaching, this paper provides a brief introduction to the dynamics of discretetime dynamic systems using examples assisted by the symbolic language Mathematica. Such systems are essentially iterated maps. In the first part, we construct orbits of points under iteration of real and complex functions. If x is a real number or a complex number, then the orbit of x under f is the sequence {x, f (x), f (f (x)), ...}. These sequences may be convergent or sequences that tend to infinity. In particular, to test this behavior in complex sequences will require the concept of derivative of a complex function. In a second part, we use the concepts reviewed in the first to build Julia sets, these sets are obtained by assigning colors to a rectangular grid points according to the behavior of their orbits under the studied complex function, the colors are assigned according the classification of the points. The pattern obtained, the Julia set is a fractal. However, the image obtained is always an approximation.



Iteration dynamic system Mathematica fixed point orbits Julia set Iteración sistema dinámico punto fijo orbita conjunto Julia CIENCIAS SOCIALES CIENCIAS SOCIALES