Bulletin of the American Physical Society
Joint Fall 2010 Meeting of the Texas Sections of the APS, AAPT, Zone 13 of SPS and the National Society of Hispanic Physicists
Volume 55, Number 11
Thursday–Saturday, October 21–23, 2010; San Antonio, Texas
Session SM1: Atomic, Molecular, and Optical Physics III |
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Chair: Kelly Nash, University of Texas at San Antonio Room: University Center III Travis Room, 2nd floor |
Saturday, October 23, 2010 10:00AM - 10:12AM |
SM1.00001: Can interference occur in conditions where the which-path information is available? John Sandy, Daniel Dominguez, Luis Grave de Peralta We show that integrated-optics pulse shapers based on arrayed waveguide gratings (AWGs) can be used to produce interference between femtosecond pulses of light in conditions where the which-path information is available. We base our discussion in recently published experimental results with AWGs illuminated with femtosecond pulses of light. In these experiments, it was possible to know which waveguide of the grating photons passed through. Nevertheless, interference occurred inside of the device. [Preview Abstract] |
Saturday, October 23, 2010 10:12AM - 10:24AM |
SM1.00002: Progress Report on Femtosecond Electron Switch using a Plasmonic Antenna Jessica White, Shawn Hilbert, Herman Batelaan In this talk we discuss progress that has been made toward a femtosecond electron switch. The system uses a pump-probe approach. We use one pulse to induce electrons from a field emission tip and a second to activate a plasmonic antenna to make an intense electric field. Descriptions of the system's components will be presented. This system could produce switching in the 20 femtosecond range. Such switching would provide better temporal resolution for movies of molecular motion, and provide the resolution required to observe the freefall of elementary particles. [Preview Abstract] |
Saturday, October 23, 2010 10:24AM - 10:36AM |
SM1.00003: In-depth trapping and fluorescence excitation of microscopic objects using single optical fiber tweezers Mervyn Pinto, Dondre Rose, Ninad Ingle, Samarendra Mohanty Fluorescence analysis of microscopic objects in suspension is of considerable interest. However, imaging and spectroscopy of motile samples in suspension requires immobilization of the sample, thereby perturbing the sample conformation. Though optical tweezers can hold microscopic samples without any physical contact, it has very short working distance, thus limiting its applicability to large depths. We report on trapping of microscopic objects at depths of few cm using single fiber optical tweezers developed by use of a microfabricated fiber tip and cw green laser beam. The micro-axicon tip was fabricated by chemical etching of single mode as well as multimode fiber. The fiber tweezers beam can simultaneously excite the trapped objects to emit fluorescence. While single mode fiber tweezers provided better trapping stability, the multi mode fiber tweezers is found to be more robust. Fluorescence imaging of trapped object inside a cuvette at depths of few cm was carried out using a side-viewing long-working distance microscope objective. A 2x2 fiber optic splitter allowed coupling of the single mode fiber tweezers beam onto one of the input arms and the fluorescence being collected by the other arm. The use of optical trapping using single fiber optical tweezers and fluorescence excitation, together will pave the way for analysis of suspended samples at large depths. [Preview Abstract] |
Saturday, October 23, 2010 10:36AM - 10:48AM |
SM1.00004: Digital holographic microscopy and atomic force microscope integrated with optical microscope Nelson Cardenas, Ninad Ingle, Lingfeng Yu, Samarendra Mohanty We report integration of atomic force microscope (AFM) and digital holography microscope (DHM) onto an inverted optical microscope. This allowed mapping of the physical and optical properties of the sample in the nanometer scale without compromising optical (phase-contrast and fluorescence) imaging capabilities of the optical microscope. While AFM provided high resolution topographical information, quantitative phase properties of the sample are revealed by the DHM technique. DHM implements off-axis configuration to encode the phase and intensity profiles in a single record. This allows for high speed acquisition of the hologram which could be numerically analyzed to reveal the sample with an axial resolution at the nanometer scale as well as changes in refractive index. Nanonics AFM platform's transparent nature and bent configuration of fiber based cantilever yields very minute interference during the simultaneous DHM and AFM recordings. We will present the imaging capabilities of the integrated system for analysis of both living and non-living structures. [Preview Abstract] |
Saturday, October 23, 2010 10:48AM - 11:00AM |
SM1.00005: Low-concentration chemical sensing using surface-enhanced coherent anti-Stokes Raman spectroscopy Xia Hua, Alexander Sinyukov, Andrew Traverso, Dmitri Veronine, Kai Wang, Hui Xia, Wenlong Yang, Luqi Yuan, Alexei Sokolov, Marlan Scully Measurements of surface enhanced coherent anti-Stokes Raman spectra (CARS) of cyclohexane are carried out. Random aggregates of gold nanoparticles for field enhancement were deposited on a glass substrate and were characterized using atomic force microscopy (AFM). Surface enhancement of the CARS signal by gold nanoparticles is observed. This technique can be used to detect low amounts of chemicals with a higher sensitivity compared to the conventional surface-enhanced Raman spectroscopy (SERS). The lowest detected concentration of cyclohexane in a thin film of methanol was 1{\%}. However, it was not possible to detect any signal from the same sample of cyclohexane without gold nanoparticles using conventional CARS technique. Therefore, surface enhancement is necessary to achieve higher spectroscopy sensitivity. Further studies of nanostructure-enhanced electrical fields are required to quantitatively understand the observed effects and will be performed in the future. [Preview Abstract] |
Saturday, October 23, 2010 11:00AM - 11:12AM |
SM1.00006: Photon Transport Through Dense Atomic Vapor Nabraj Bhattarai, Andrzej Sieradzan An understanding of photon transport through scattering media is of great importance to many areas of physics and astronomy. We present a detailed study of infrared light propagation in hot cesium vapors. An experimental investigation of beam transmission as a function of vapor density shows that while a monochromatic light spreads in manner characteristic for a normal diffusion, transport of nonmonochromatic atomic fluorescence shows properties of Levy flights. A simple model gives a good quantitative account of most of our experimental results. However, yet unexplained presence of fluorescence components practically immune to scattering must be dealt with before a fully consistent picture of the scattering process can be claimed. [Preview Abstract] |
Saturday, October 23, 2010 11:12AM - 11:24AM |
SM1.00007: Resonant dispersive waves generated with multi-input femtosecond pulses Kai Wang, Jiahui Peng, Alex Sokolov We investigated the resonant dispersive waves generated by high-order dispersion theoretically. We considered different femtosecond pulses propagating in the kagome-lattice hollow-core photonics crystal fibers. The two third order and fourth order resonant dispersive waves would be produced in the visible range to produce the ultrashort pulse. [Preview Abstract] |
Saturday, October 23, 2010 11:24AM - 11:36AM |
SM1.00008: A Newtonian Explanation of the Hydrogen Fine Structure Paul Fisher, James Espinosa, James Woodyard The Hydrogen spectrum as seen by low dispersion spectrometers is correctly described by a classical theory founded on Ritz's magnetic model. With increasingly powerful instruments, individual lines are split into smaller groupings that are three orders of magnitude smaller. Arnold Sommerfeld was the first to develop a theory based on the mass variation of the electron to correctly describe this ``fine'' structure. A few years later, Vannevar Bush pointed out that Weber's force law could be used instead of Einstein's theory of relativity. We will utilize this line of approach to present a purely classical theory of the fine structure of the Hydrogen atom. Ritz's theory of electromagnetism replaces Weber's law; we will summarize all the other atomic physics experiments that our classical theory already describes correctly. Finally we will show how this fine structure theory logically paves the way for an explanation of the linear Stark effect. [Preview Abstract] |
Saturday, October 23, 2010 11:36AM - 11:48AM |
SM1.00009: A Classical Description of the Hyperfine Structure of the Hydrogen Atom Andrea Chaney, James Espinosa, James Woodyard As stronger dispersion gratings are utilized, the Hydrogen spectrum is broken into small groupings. At first, the fine structure was successfully described by Sommerfeld by utilizing the special theory of relativity. The fine structure groupings are three orders of magnitude smaller than the series separations as described by Balmer and others. With even further powerful instruments, Michelson was the first to split these lines into further groupings which are a further two orders of magnitude smaller. It was almost fifty years before Breit used quantum mechanics to describe this hyperfine structure. It is almost universally believed that classical theory utterly fails to describe this phenomenon. We will show how our classical Hydrogen atom based on Ritz's magnetic model can account for the splitting of the 1s state, which is famous for its use by radio astronomers to map out the distribution of hydrogen in the universe. [Preview Abstract] |
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