Bulletin of the American Physical Society
Joint Fall 2009 Meeting of the Texas Sections of the APS, AAPT, and SPS
Volume 54, Number 13
Thursday–Saturday, October 22–24, 2009; San Marcos, Texas
Session G3: Atomic, Molecular, and Optical Physics |
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Chair: Charles Manka, Naval Research Laboratory Room: LBJ Student Center 3-10.1 |
Saturday, October 24, 2009 10:00AM - 10:12AM |
G3.00001: The photon Russell L. Collins There are no TEM waves, only photons. Lets build a photon, using a radio antenna. A short antenna ($2L<< \lambda$) simplifies the calculation, letting $\bf B\bf $ fall off everywhere as $1/r^{2}$. The Biot-Savart law finds $B = (\mu_{0}/4\pi)(LI_{0}/r^{2})\sin \theta \sin \omega t$. The magnetic flux thru a semi-circle of radius $\lambda/2$ is set equal to the flux quantum h/e, determining the needed source strength, $LI_{0}$. From this, one can integrate the magnetic energy density over a sphere of radius $\lambda /2$ and finds it to be $1.0121 hc/\lambda$. Pretty close. A $\bf B \bf$ field collapses when the current ceases, but the photon evades this by creating a $\epsilon_{0} \partial \bf E \bf / \partial t$ displacement current at center that fully supports the toroidal $\bf B \bf$ assembly as it moves at c. This $\bf E=vxB \bf $ arises because the photon moves at c. Stopped, a photon decays. At every point along the photon's path, an observer will note a transient oscillation of an $\bf E \bf$ field. This sources the EM ``guiding wave'', carrying little or no energy and expanding at c. At the head of the photon, all these spherical guiding waves gather ``in-phase'' as a planar wavefront. This model speaks to all the many things we know about light. The photon is tiny, but its guiding wave is huge. [Preview Abstract] |
Saturday, October 24, 2009 10:12AM - 10:24AM |
G3.00002: Characterization of Guided Mode Resonance Filters for Wavelength Stabilization of Thulium Fiber Lasers Tany Dax, Martin Richardson, Andrew Sims Stable, eye-safe lasers are important for use in medical environments and atmospheric propagation. A Guided Mode Resonance Filter (GMRF) consists of a waveguide between a layer of substrate and a diffractive layer. The GMRFs are produced at UNC Charlotte. The Thulium (Tm) doped fiber used consists of an octagonal undoped fiber with a doped core, and is the gain medium of the fiber laser. The Laser Plasma Laboratory at the UCF College of Optics and Photonics performed the necessary characterization of the output spectra and damage thresholds of the GMRF when used as the feedback element of the Thulium fiber lasers. This summer's Research Experience for Undergraduates project aided in this characterization. The laser reached 10W of stabilized output. Further, the GMRFs withstood thermal changes and focused power with no damage or change in output spectra. [Preview Abstract] |
Saturday, October 24, 2009 10:24AM - 10:36AM |
G3.00003: A Comparative Study of a New Computational Technique for Determining Optical Properties of Biological Samples Utilizing the Discontinuity Theory Described by the Dahm equation Brian Yust, Lawrence Mimun, Dhiraj Sardar Due to inhomogeneities inherent in biological samples, such as tissues, the current theories which are used to determine their optical properties can only result in an estimate whose accuracy is dependent on how well the approximation applies to the geometry and specific details of each sample. Specifically, in the regime of extremely thin biological samples, the usually techniques for determining optical properties, such as Kubelka-Munk, Inverse Adding-Doubling, and Inverse Monte Carlo, are no longer valid. A new computational technique utilizing the Dahm equation has been developed to determine the optical properties of samples which can be described under the representative layer theory. The main differences, strengths, weaknesses between this new technique and conventional ones will be discussed. A statistical comparison will also be made using experimental data sets previously obtained. [Preview Abstract] |
Saturday, October 24, 2009 10:36AM - 10:48AM |
G3.00004: Electromagnetically induced transparency inside the laser cavity: Switch between first-order and second-order phase transitions Qingqing Sun, Selim Shahriar, Suhail Zubairy We investigate the effect of electromagnetically induced transparency (EIT) inside a laser cavity. By changing the intensity of an external drive field, we can control the absorption to the laser field. A semiclassical analysis shows that the system undergoes switch between first-order and second-order phase transitions. Around the tricritical point there could be a second-order phase transition followed by a first-order phase transition. [Preview Abstract] |
Saturday, October 24, 2009 10:48AM - 11:00AM |
G3.00005: Optical precursor in Rb Vapor Wenlong Yang, Alexei Sokolov Picosecond pulses with center wave length 780nm are directed through a hot Rubidium cell. The input pulse are shaped with dazzler to be Gaussian, modulated Gaussian or square shape pulses. The output pulses are detected by streak camera. Simulation results of output pulse shape are presented. Optical precursors are observed in the simulation results. Some issues in the simulations are also discussed. [Preview Abstract] |
Saturday, October 24, 2009 11:00AM - 11:12AM |
G3.00006: A Complete Discharging Solution for LIGO Quentin Funk, Dennis Ugolini Surface charge on LIGO interferometer optics creates a changing electric field that exerts an oscillating pull on the optics, creating a fake signal. Replacing viton earthquake stops with fused silica reduced charging from $\left( {6\pm 1} \right)\times 10^{-12}$C/cm$^{2}$ to $\left( {-4\pm 1} \right)\times 10^{-14}$ C/cm$^{2}$ per contact. We also investigated three ways to discharge an optic in vacuum. UV light removes negative charge via the photoelectric effect with a time constant of $\left( {9\pm 3} \right)\times 10^{-6}$s$^{-1}$, and neutralizes positive charge by liberating electrons from a reaction mass at a rate of $\left( {-9.89\pm .2} \right)\times 10^{-4}$C/s. Both polarities are discharged faster at lower wavelengths. The energy to reduce negative surface charge by 1/$e$ is $(3\pm 1)\times 10^{-2}$ J/cm$^{2}$, which could damage the reflective optical coatings over time. A Kimball Physics electron gun eliminates positive charge within seconds, but we believe that a modified Bayard-Alpert gauge could be a complete, less expensive, and more robust discharging solution. [Preview Abstract] |
Saturday, October 24, 2009 11:12AM - 11:24AM |
G3.00007: Wide-Field Microscopy Based on Leakage of Plasmon-Coupled Fluorescence Jacob Ajimo, Stephen P. Frisbie, Ananth Krishnan, Catherine Chestnutt, Alex A. Bernussi, Luis Grave de Peralta Recent developments in wide-field leakage plasmon-coupled fluorescence (WFLPCF) microscopy are presented. We present pictures of nanostructures taken with a WFLPCF microscope. We discuss the general relationship existing between the lateral pattern stamped in the sample surface and the Fraunhofer diffraction pattern formed in the Fourier plane by the plasmon-coupled fluorescence leaked to the high numerical aperture objective lens of the microscope. In addition, we demonstrate that adding a linear polarizer in the optical path of the microscope permits to identify the polarization state of the guided wave polariton modes exited in the asymmetric metal/dielectric/air slab waveguide of the samples. [Preview Abstract] |
Saturday, October 24, 2009 11:24AM - 11:36AM |
G3.00008: Heterodyne effect in Hybrid CARS Xi Wang, Aihua Zhang, Miaochan Zhi, Alexei Sokolov, George Welch, Marlan Scully We study the interaction between the resonant Raman signal and non-Raman field, either the concomitant nonresonant four-wave-mixing (FWM) background or an applied external field, in our recently developed scheme of coherent Anti-Stokes Raman scattering, a hybrid CARS. Our technique combines instantaneous coherent excitation of several characteristic molecular vibrations with subsequent probing of these vibrations by an optimally shaped, time-delayed, narrowband laser pulse. This pulse configuration mitigates the non-resonant FWM background while maximizing the Raman-resonant signal, and allows rapid and highly specific detection even in the presence of multiple scattering. We apply this method to non-invasive monitoring of blood glucose levels. Under certain conditions we find that the measured signal is linearly proportional to the glucose concentration due to optical interference with the residual background light, which allows reliable detection of spectral signatures down to medically-relevant glucose levels. We also study the interference between the CARS field and an external field (the local oscillator) by controlling their relative phase and amplitude. This control allows direct observation of the real and imaginary components of the third-order nonlinear susceptibility (\textit{$\chi $}$^{(3)})$ of the sample. We demonstrate that the heterodyne method can be used to amplify the signal and thus increase detection sensitivity. [Preview Abstract] |
Saturday, October 24, 2009 11:36AM - 11:48AM |
G3.00009: Raman's Classical Theory of the Compton Effect James Espinosa, James Woodyard The Compton effect is one of the key experiments that convinced physicists to accept the photon concept. One of the few notable dissenters was C.V. Raman. After a brief overview of his life, we will describe the physical model that he used to reproduce the Compton formula for scattering. It combines a quasi-free electronic atomic model with classical wave principles. We will show the theory predicts two kinds of radiation from this atom when a light wave interacts with it. One of them will be determined by the motion of the electrons and will produce the Compton scattering predicted by quantum theory. We will slightly modify his argument to make it compatible with an earlier work by Hugh Callendar that described Blackbody radiation classically, demonstrating that the photon concept is not needed to explain Compton's experiment. [Preview Abstract] |
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