Leyva J.A.L.,Research Center Cientifica Educacion |
Mondragon A.A.,Research Center Cientifica Educacion |
Garcia E.,Autonomous University of Baja California |
Mendieta F.J.,Mexicana University |
And 2 more authors.
Optical Engineering | Year: 2012
We describe a homodyne optical Costas loop receiver intended to detect weak coherent states with diffused phase and suppressed carrier phase modulation. In order to get the information contained in the quadrature components of the optical field, we implement an 8-port receiver operating at 1550 nm, based on the manipulation of the state of polarization of both the local oscillator and the data signal. Employing binary phase-shift keying, we make measurements in the time and frequency domain of the quantum noise and bit error rate using an optimum loop filter, and compare the performance of our receiver against the standard quantum limit for the simultaneous quadrature detection, considering both ideal conditions and the overall efficiency of our set up. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).
Torres-Torres C.,National Polytechnic Institute of Mexico |
Torres-Torres D.,CIMAV |
Garcia-Zarate M.A.,Research Center Cientifica Educacion |
Garcia-Gil C.I.,Research Center Cientifica Educacion |
And 5 more authors.
Journal of Modern Optics | Year: 2014
Photoconduction and nonlinear optical refraction effects exhibited by an array of separated Au microchannels are reported. The samples were constituted by Au thin solid films containing Au nanoparticles prepared by an evaporation method. The photoconductivity of the sample was measured with continuous illumination at 532 nm wavelength with 1 W average power. A vectorial two-wave interaction allowed us to explore the optical Kerr effect exhibited at 532 nm wavelength and 1 ns pulse duration. Z-scan experiments performed in a comparative Au thin solid film pointed out a saturated optical absorption as a dominant physical mechanism that originates the optical nonlinearity at 1064 nm wavelength with 150 ps pulses. The third-order optical nonlinearities measured in the studied cases with ps and ns pulses were estimated to be about |X(3) 1111| = 10-10 esu. Microscopy observations were carried out to describe the morphology that is responsible for the noticeable optical Kerr effect. The optoelectronic switching behavior exhibited by the studied array was analyzed. © 2014 Taylor & Francis.
Martin-Atienza B.,Autonomous University of Baja California |
Alvarez-Borrego J.,Research Center Cientifica Educacion
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2013
The sunlight reflection process in the sea surface, considering a two-dimensional geometric model with variable reflection angle, is examined and the corresponding equations are derived. A synthetic data surface is used to calculate the corresponding glitter pattern. An analysis of the relationship between the variance of the surface slopes and the variance of the intensity values in the glitter pattern are calculated considering a gaussian distribution and a non-gaussian distribution of the surface slopes. The results obtained for both distributions are compared and presented graphically. © 2013 IEEE.
Puente N.P.,Autonomous University of Baja California |
Chaikina E.I.,Research Center Cientifica Educacion |
Herath S.,Missouri University of Science and Technology |
Yamilov A.,Missouri University of Science and Technology
Applied Optics | Year: 2011
We present results of experimental and theoretical studies of polarization-resolved light transmission through optical fiber with disorder generated in its germanium-doped core via UV radiation transmitted through a diffuser. In samples longer than a certain characteristic length, the power transmitted with preserved polarization is observed to be distributed over all forward-propagating modes, as evidenced by the Rayleigh negative exponential distribution of the near-field intensity at the output surface of the fiber. Furthermore, the transmitted power becomes also equally distributed over both polarizations. To describe the optical properties of the fibers with the experimentally induced disorder, a theoretical model based on coupled-mode theory is developed. The obtained analytical expression for the correlation function describing spatial properties of the disorder shows that it is highly anisotropic. Our calculations demonstrate that this experimentally controllable anisotropy can lead to suppression of the radiative leakage of the propagating modes, so that intermode coupling becomes the dominant scattering process. The obtained theoretical expressions for the polarization-resolved transmission fit very well with the experimental data, and the information extracted from the fit shows that radiative leakage is indeed small. The reported technique provides an easy way to fabricate different configurations of controlled disorder in optical fibers suitable for such applications as random fiber lasers. © 2011 Optical Society of America.
Birt T.P.,Queen's University |
Carter H.R.,California Institute of Environmental Studies |
Whitworth D.L.,California Institute of Environmental Studies |
McDonald A.,Queen's University |
And 6 more authors.
Auk | Year: 2012
Population genetic structure was characterized in Xantus's Murrelet (Synthliboramphus hypoleucus) by analyzing variation in the mitochondrial control region (505 samples) and 12 microsatellite loci (428 samples) in birds captured at all 13 current breeding areas in southern California and northwestern Baja California, Mexico. The two types of molecular markers were consistent in revealing strong genetic differentiation between the two currently recognized subspecies (S. h. hypoleucus and S. h. scrippsi) and little or no differentiation among breeding areas within subspecies. Estimates of gene flow were essentially zero, and no evidence for admixture was found. Gene flow among breeding locations within subspecies, on the other hand, was seemingly high. Given these genetic results, as well as clear morphological differences between the subspecies and the apparent lack of interbreeding at breeding areas where the two forms are sympatric, we suggest that two species be recognized. Both forms are genetically distinct from Craveri's Murrelet (S. craveri), a closely related species whose breeding range partially overlaps that of Xantus's Murrelet. Taxonomic subdivision of Xantus's Murrelet introduces new conservation concerns, especially for S. h. hypoleucus, which urgently requires greater study and protective efforts. © The American Ornithologists' Union, 2012.
Biggs J.S.,University of Guam |
Watkins M.,University of Utah |
Puillandre N.,University of Utah |
Ownby J.-P.,University of Utah |
And 8 more authors.
Molecular Phylogenetics and Evolution | Year: 2010
Conus species are characterized by their hyperdiverse toxins, encoded by a few gene superfamilies. Our phylogenies of the genus, based on mitochondrial genes, confirm previous results that C. californicus is highly divergent from all other species. Genetic and biochemical analysis of their venom peptides comprise the fifteen most abundant conopeptides and over 50 mature cDNA transcripts from the venom duct. Although C. californicus venom retains many of the general properties of other Conus species, they share only half of the toxin gene superfamilies found in other Conus species. Thus, in these two lineages, approximately half of the rapidly diversifying gene superfamilies originated after an early Tertiary split. Such results demonstrate that, unlike endogenously acting gene families, these genes are likely to be significantly more restricted in their phylogenetic distribution. In concordance with the evolutionary distance of C. californicus from other species, there are aspects of prey-capture behavior and prey preferences of this species that diverges significantly from all other Conus. © 2010 Elsevier Inc. All rights reserved.
Rangel-Rojo R.,Research Center Cientifica Educacion |
Can-Uc B.A.,Research Center Cientifica Educacion |
Rodriguez-Fernandez L.,National Autonomous University of Mexico |
Oliver A.,National Autonomous University of Mexico
Latin America Optics and Photonics Conference, LAOP 2014 | Year: 2014
In this work, we present results for the study of the third-order nonlinear optical properties of metallic nanoparticles contained in a silica matrix. This includes particle with an spherical shape, as well as elongated in a preferential direction. Femtosecond infrared pulses are used both to study the nonlinear response of the particle, as well as to modify them, producing tailor-made patterns in the matrix. Finally, a masked multiple energy ion-implantation technique is used to produce channel waveguides based on these materials. © OSA 2014.
Corona M.,National Autonomous University of Mexico |
Corona M.,Research Center Cientifica Educacion |
Garay-Palmett K.,National Autonomous University of Mexico |
U'Ren A.B.,National Autonomous University of Mexico
Optics Letters | Year: 2011
We present an experimental proposal for the generation of photon triplets based on third-order spontaneous parametric downconversion in thin optical fibers. Our analysis includes expressions for the quantum state, which describes the photon triplets and for the generation rate in terms of all experimental parameters. We also present, for a specific source design, numerically calculated generation rates. © 2011 Optical Society of America.
Hwang P.A.,U.S. Navy |
Ocampo-Torres F.J.,Research Center Cientifica Educacion |
Garcia-Nava H.,Research Center Cientifica Educacion
Journal of Atmospheric and Oceanic Technology | Year: 2012
In an earlier paper by Wang and Hwang, a wave steepness method was introduced to separate the wind sea and swell of the 1D wave spectrum without relying on external information, such as the wind speed. Later, the method was found to produce the unreasonable result of placing the swell-sea separation frequency higher than the wind sea peak frequency. Here, the following two factors causing the erratic performance are identified: (a) the wave steepness method defines the swell-sea separation frequency to be equal to the wind sea peak frequency with a wave age equal to one, and, (b) for more mature wave conditions, the peak frequency of the wave steepness function may not continue monotonic downshifting in high winds if the highfrequency portion of the wave spectrum has a spectral slope milder than 25. Conceptually, the swell-sea separation frequency should be placed between the swell and wind sea peak frequencies rather than at the wind sea peak frequency. Furthermore the wind sea wave age can vary over a considerable range, thus factor a above can lead to incorrect results. Also, because the slope of the wind sea equilibrium spectrum is typically close to 24, factor b becomes a serious restriction in more mature wave conditions. A spectrum integration method generalized from the wave steepness method is presented here for wind sea and swell separation of the 1D wave spectrum without requiring external information. The new spectrum integration method works very well over a wide range of wind wave development stages in the ocean. © 2012 American Meteorological Society.
Aguilar-Gonzalez P.M.,Research Center Cientifica Educacion |
Kober V.,Research Center Cientifica Educacion
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012
Correlation filters for object detection use information about the appearance and shape of the object of interest. Therefore, detection performance degrades when the appearance of the object in the scene differs from the appearance used in the filter design process. This problem has been approached by utilizing composite filters designed from a training set containing known views of the object of interest. However, common composite filter design is usually carried out under the assumption that the ideal appearance and shape of the target are known. In this work we propose an algorithm for composite filter design using noisy training images. The algorithm is a modification of the class synthetic discriminant function technique that uses arbitrary filter impulse responses. Furthermore, filters can be adapted to achieve a prescribed discrimination capability for a class of backgrounds if a representative sample is known. Computer simulation results obtained with the proposed algorithm are presented and compared with those of common composite correlation filters. © 2012 Springer-Verlag Berlin Heidelberg.