41 episodios

The OSC Colloquium Series is a dynamic forum for the rapid and widespread interchange of ideas, techniques and research in all areas of optics. We schedule an impressive list of academic scholars and industry leaders to lead discussions and open the program to questions and comments. All OSC students and faculty members, as well as members of the optics community and the public, are invited to attend.

Colloquium is usually held on Thursday at 3:30 p.m. in Meinel 307.

Optical Sciences Colloquium Series University of Arizona

    • Ciencia

The OSC Colloquium Series is a dynamic forum for the rapid and widespread interchange of ideas, techniques and research in all areas of optics. We schedule an impressive list of academic scholars and industry leaders to lead discussions and open the program to questions and comments. All OSC students and faculty members, as well as members of the optics community and the public, are invited to attend.

Colloquium is usually held on Thursday at 3:30 p.m. in Meinel 307.

    • video
    Gigapixel Television

    Gigapixel Television

    Abstract: The physical limit for the number of pixels per color channel per frame in an optical imager is approximately equal to the aperture area in square microns. While this limit is essentially achieved in megapixel scale cell phone cameras, the limit of 100 megapixels for cm apertures, 10 gigapixels for 10 cm apertures and 1 terapixel for meter apertures is far beyond current practice. These pixel counts may be further increased by factors of 100-10,000 in spectral and 3-D imagers. At the physical limit, a practical imager may easily deliver >1 terapixel per second. Imagers that scale to the physical limit must overcome challenges in the design of lenses, electronic focal planes and image processing units. This talk reviews efforts to overcome these challenges through the DARPA AWARE program. We specifically discuss the construction of a compact 5 gigapixel camera and we discuss implications for such cameras in online and broadcast media. Presented Thursday, October 4, 2012.

    • 1h 2 min
    • video
    Colloquium: A. Mysyrowicz

    Colloquium: A. Mysyrowicz

    Abstract:

    The fate of an ultrashort laser pulse propagating in air depends crucially upon its peak power. Below a critical value, Pcr, group velocity dispersion and beam diffraction combine to rapidly reduce the pulse intensity. On the other hand, if P is less than Pcr, a completely different behaviour is observed. In this case, instead of decreasing, the pulse intensity increases with distance up to the point where it becomes sufficiently high (~1013 W/cm²) to ionize air. The pulse then retains this high intensity for very long distances that can reach kilometers. This regime is called filamentation. In this lecture the basic notions at the heart of filamentation will be introduced. Techniques to characterize air filaments will be described. This includes measurements of the beam size, pulse intensity, pulse duration, density and length of the plasma column created in the wake of the pulse, and the plasma density evolution. These results are well reproduced by numerical simulations. Recent experiments will be described which allow to manipulate and to exchange energy between filaments. A second part will be devoted to applications of filaments. They include the triggering and guiding of low resistance, high current electric discharges, the creation of short bursts of terahertz radiation, the illumination of distant objects, the use of filaments as virtual RF antennas. Presented Thursday, October 11, 2012.

    • 52 min
    • video
    Optical Physics in Organic Semiconductor Molecules

    Optical Physics in Organic Semiconductor Molecules

    Abstract: Organic semiconductor materials offer the potential of low-cost and flexible displays and lighting solutions, some of which have already made it to the marketplace. Despite this, much of the underlying optical physics remains poorly understood and hinders progress towards better and more powerful devices. In this talk, the basic properties of organic semiconductors will be reviewed and some of the outstanding issues explored. We will show how simple models based on dipole-dipole coupling can be validated (by comparison with quantum chemistry) and used to compute optical properties such as absorption, gain and luminescence spectra. Recent theoretical and experimental results on the optical pulse propagation and timescales of excitation transfer and hopping in linear oligoflourine and star-shaped samples will be also presented. Presented Thursday, September 20, 2012.

    • 54 min
    • video
    High-Power Beams in the Atmosphere: Where the Air Goes Nonlinear

    High-Power Beams in the Atmosphere: Where the Air Goes Nonlinear

    Abstract: We often forget in our daily life that air does not have the same optical properties as vacuum. At least in New Mexico and Arizona, we are made aware that it has an index of refraction, and that it is not the ideal homogeneous optical material. However, in daily experiments, we do not think too often of air as being a nonlinear medium, having a complex intensity dependent index of refraction, nonlinear absorption, induced birefringence, and becoming a partially conductive medium. These properties lead to light filamentation, a situation where the nonlinear properties of air dominate the propagation properties. It has produced — and still is producing — a flurry of papers and dreams of wild applications. Aside from the practical or unpractical applications, it is a unique example of light-matter-light interaction, which makes us rethink basic concepts of electromagnetism, even down to the nature of an index of refraction.

    He investigating two types of filaments, produced either by femtosecond pulses in the near infrared (800 nm) and by nanoscond pulses in the ultraviolet (266 nm). The two are interesting in comparison because of their very different wavelength and temporal regime.

    An infrared filament is an ideal object of study for investigating strong field light-matter interaction, in which light and matter have a mutual recordable effect on each other. For a few hundred femtosecond-long infrared filament in air, the interaction of light is with bond electrons in atoms or molecules, with free electrons created by tunnel ionized, and with partially orientated molecules. Since the modification of light happens in a time scale much faster than a plasma period, a careful microscopic (in the fs scale) study of the parameters involved in filament formation is needed.

    In this talk, Diels shows how pre-filamentation propagation can cause a) new spectral development and b) polarization-dependent filamentation. We used an aerodynamic window to prepare the focus in vacuum before launching the filament in air. A model to study the index of refraction of tunneled electrons in the femtosecond time scale of a laser pulse was presented.

    • 1h
    • video
    Freeform Optical Surfaces

    Freeform Optical Surfaces

    Abstract: Slow-servo diamond turning has revolutionized what is possible in optical fabrication. As a result, optical design provides new horizons where freeform surfaces may offer new degrees of freedom. In this talk I will provide a brief history of the emergence of freeform optics and point to a growing customer base. I will then discuss recent advances in surface shape descriptions for freeform optics from phi-polynomials to multicentric radial basis functions. Finally, I will show how freeform surfaces may provide in one case study a factor of 10 in field area. Insight into the correction of aberrations will be provided and a metrology approach to testing freeform surfaces will be discussed.

    Dr. Rolland is Brian J. Thompson Professor of Optical & Biomedical Engineering; Associate Director of the R.E. Hopkins Center for Optical Design & Engineering. Professor Rolland's central research interests are in the fields of optical instrumentation and system engineering. Research areas of interest are (1) Optical System Design for Imaging and Non-imaging Optics (2) Physics-based modeling, and (3) Image Quality Assessment. These areas have been applied to Eyewear Displays for Augmented Reality, Optical Coherence Imaging, Biomedical and Medical Modeling and Simulation, Alignment of Optical Systems, and 3D Velocimetry.

    • 1h 13 min
    • video
    Imaging of Implosions at the National Ignition Facility

    Imaging of Implosions at the National Ignition Facility

    Abstract: The National Ignition Facility, sited at the Lawrence Livermore National Laboratory in Livermore, Calif., is a 192-beam, 1.8-MJ (351 nm) laser designed to compress ~250 µg spheres of deuterium and tritium to thermonuclear ignition. Fuel compression is achieved through an ablative rocket drive mechanism where the outer wall of the fuel shell is ablatively removed by a 300 eV radiation field. The 300 eV field is produced through laser matter interactions at the wall of either a gold or uranium hohlraum surrounding the capsule. Obtaining ignition will depend on controlling several critical aspects of the implosion, including the amount of kinetic energy transferred to the fuel, the internal energy generated within the fuel, the symmetry of the implosion, as well as maintaining the hydrodynamic stability of the fuel as it compresses. Imaging diagnostics provide unique insight into the performance of these implosions, and the NIF has assembled a broad suite of imaging capability, utilizing both X-rays and neutrons to diagnose critical aspects of the implosion process. In this presentation I will review the basic motivation for the inertial confinement fusion experiments taking place at the NIF, as well as a description of the NIF laser and its diagnostic capability, with an emphasis on imaging. This work was performed for the U.S. Department of Energy and National Nuclear Security Administration and by the National Ignition Campaign partners: Lawrence Livermore National Laboratory, University of Rochester Laboratory for Laser Energetics, General Atomics, Los Alamos National Laboratory and Sandia National Laboratories. Other contributors include Lawrence Berkeley National Laboratory; the Massachusetts Institute of Technology; Atomic Weapons Establishment, England; and Commissariat à l’Énergie Atomique, France.

    Gary P. Grim received his B.S. in mathematics from California State University, Chico in 1985, followed by his M.S. in 1992 and Ph.D. in 199) in experimental physics from the University of California, Davis. Grim’s graduate studies were in the field of particle physics, where he studied rare charm mesons decays as a test of electro-weak interaction theory within the standard model of particle physics. During his postdoctoral research in 1995–1999, Grim switched research groups at Davis and was an active participant in the design and construction of several semiconductor-based particle tracking detectors aimed at hadron collider experiments. These efforts included the CDF experiment at Fermi National Accelerator Laboratory and CMS experiment at CERN. During this time, Grim developed and tested the first data-driven pixel tracking telescope for use in high energy physics.

    In 2002, Grim joined the Physics Division staff at the Los Alamos National Laboratory. During his tenure at LANL, he has worked on a wide ranging set of projects and problems, including leading the design and construction of the National Ignition Facility neutron imaging diagnostic, as well as being a key player in the construction of a forward pixel detector for use at the PHENIX experiment at the RHIC facility sited at Brookhaven National Laboratory. Grim’s current efforts are focused on analyzing the data being produced by the NIF imaging diagnostics, as well as leading the development of new NIF diagnostic capabilities including the novel prompt-radiochemical assay techniques and gamma-ray imaging capabilities.

    • 1h 6 min

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