Bulletin of the American Physical Society
15th Annual Meeting of the Northwest Section of the APS
Volume 59, Number 6
Thursday–Saturday, May 1–3, 2014; Seattle, Washington
Session G1: Atomic, Molecular and Optical Physics II |
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Chair: Boris Blinov, University of Washington Room: Alder Commons 104 |
Saturday, May 3, 2014 1:30PM - 2:00PM |
G1.00001: How a noisy signal can be a useful spectroscopic tool: understanding noise from quantum interference Invited Speaker: Shannon O'Leary Naively one might assume that unavoidable fluctuations in laser frequency, intensity, and phase always diminishes the precision of spectroscopic applications. But light-matter interactions sensitive to laser fluctuations encode useful information about the medium in the transmitted light's fluctuations, and analysis of these fluctuations can enhance measurement precision. Diode lasers in particular have significant phase noise and a resonant atomic vapor converts this phase noise into transmitted intensity noise. Further, intensity noise from two orthogonally polarized fields originating from the same laser can be either correlated or anti-correlated, depending very sensitively on detuning from a resonance. In this talk I will present a noise correlation technique using a single ``noisy'' diode laser interacting with rubidium vapor on a sharp resonance feature from quantum interference, Electromagnetically Induced Transparency (EIT). Of particular interest is a narrow band of correlation that coincides with the quantum interference. The linewidth of this noise correlation peak has been shown in earlier work to be power-broadening resistant at low laser powers. I will present recent experimental noise correlation studies, including power broadening of this correlation peak at higher powers. This noise correlation technique holds promise in high-resolution applications such as atomic EIT-noise magnetometry. [Preview Abstract] |
Saturday, May 3, 2014 2:00PM - 2:12PM |
G1.00002: Ytterbium Bose-Einstein condensate interferometer: current results and new construction Benjamin Plotkin-Swing, Alan Jamison, Subhadeep Gupta We present the first ytterbium matter-wave interferometer using a Bose-Einstein condensate (BEC) source in a contrast interferometer geometry. We measured h/m, where h is Planck's constant and m is the mass of an ytterbium atom, in order to determine the fine structure constant $\alpha$. We demonstrate theoretical understanding and experimental control over our two main sources of systematic error: atomic interactions and diffraction phases. Based on our findings, we present our plans for increasing the precision of our $\alpha$ measurement to the level of one part in ten billion. We also observed that the interferometer signal is sensitive to the condensate critical temperature, and we propose BEC interferometry as a tool for studying phase transitions. We will describe some of the features of a new apparatus for our next generation of measurements that is currently under construction. [Preview Abstract] |
Saturday, May 3, 2014 2:12PM - 2:24PM |
G1.00003: Stress Induced Birefringence in Atom Trap Viewports Claire Warner, Alexandre Gorelov, John Behr At TRIUMF Neutral Atom Trap (TRINAT), the current goal is a measurement of the angular asymmetry of beta particles with respect to the nuclear spin, $A_{\beta }$, from the beta decay of $^{\mathrm{37}}$K nuclei. Trapped atoms are spin-polarized by optically pumping with circularly polarized light. We characterize the degree of circular polarization of the light with the Stokes parameter S$_{\mathrm{3}}$; with an S$_{\mathrm{3}}$ value of 0.999 required to spin polarize the atoms to a proportional degree of accuracy of 10$^{\mathrm{-3}}$. One major difficulty we have encountered is stress induced birefringence on the viewports of the atom trap, which alters the S$_{\mathrm{3}}$ value. Fully annealed copper gaskets consistently achieved S$_{\mathrm{3}}$ values of over 0.999 with reproducibility down to 0.9986 and a strong dependence on the torque applied to the bolts sealing the CF flange. Using elastomer o-rings to seal the viewports, we achieved S$_{\mathrm{3}}$ values of over 0.9999, corresponding to a birefringence of $\Delta $n $=$ 3x10$^{\mathrm{-6}}$ [see Solmeyer, Rev. Sci. Instrum$.$ 82 (2011) 066105]. The drawbacks of this method are outgassing and permeation. We achieved 3x10$^{\mathrm{-8}}$ Torr with Viton and Kalrez o-rings, and we are testing Neoflon. In this talk methods of producing and quantifying circularly polarized light will be discussed, as well as techniques for reducing stress-induced birefringence. [Preview Abstract] |
Saturday, May 3, 2014 2:24PM - 2:36PM |
G1.00004: Characterization of Electron Orbital Angular Momentum Transfer to Nanoparticle Plasmon Modes Tyler Harvey, Jordan Chess, Jordan Pierce, Peter Ercius, Benjamin McMorran We observed the decay of an electron vortex beam from a state with orbital angular momentum $m = 1\hbar$ to $m = 0\hbar$ by interaction with gold nanoparticle surface plasmon modes. We produced electron vortex beams with $m=1\hbar$ orbital angular momentum in a transmission electron microscope at 300 kV. We observed an increase in the intensity of the zero orbital angular momentum component of the beam upon interaction with a gold nanopariticle. By conservation of orbital angular momentum, we see that we transferred orbital angular momentum to the nanoparticle. Because this scattered intensity peaked when the radius of the beam matched the radius of the nanoparticle, and because preliminary electron energy loss spectra show a peak at 2 eV, we speculate that orbital angular momentum was transferred to plasmon modes in the nanoparticle. Several optical studies have induced plasmon vortices using optical vortices and circularly polarized light and suggested their use in nanophotonic and plasmonic devices. Direct observation of angular momentum transfer from electron vortices allows for unique identification of the orbital angular momentum associated with localized plasmon excitations down to the nanometer scale. [Preview Abstract] |
Saturday, May 3, 2014 2:36PM - 2:48PM |
G1.00005: Nonlinear Terahertz Spectroscopy of Single-Layer Graphene Zachary Thompson, Michael Paul, Andrew Stickel, Jenna Wardini, Ethan Minot, Yun-Shik Lee Graphene has unique electronic properties which lead to remarkably strong optical nonlinearities in the terahertz (THz) and infrared (IR) regime, thus making it an attractive material for active photonic devices. Using THz free-space transmission spectroscopy, we demonstrate large THz transmission enhancement (\textgreater 15{\%}) in single-layer CVD graphene at high THz intensities. The nonlinear effects, caused by charge acceleration and carrier-carrier scattering, exhibit non-Drude behavior in the THz conductivity, where THz fields induce extreme non-equilibrium electron distributions. [Preview Abstract] |
Saturday, May 3, 2014 2:48PM - 3:00PM |
G1.00006: Large Enhancement of Nonlinear Terahertz Absorption in Intrinsic GaAs by Plasmonic Nano Antennas Michael Paul, Young-Gyun Jeong, Seung-Hyun Kim, Ki-Ju Yee, Dai-Sik Kim, Yun-Shik Lee We present our preliminary study on nonlinear THz effects in GaAs and their huge enhancement by plasmonic nano-antennas. We fabricated nano-antenna arrays on a 500-$\mu$ m-thick, intrinsic (100) GaAs wafer, using an electron beam lithography technique. THz pulses were generated by tilted-pulse-front optical rectification in LiNbO$_{3}$. The THz field amplitude (central frequency, 1 THz; bandwidth, 1 THz) varies from 20 to 120 kV/cm. We measured the transmitted THz pulses using a L-He cooled Si:Bolometer to obtain either spectrally-integrated total THz transmitted power or transmission spectra via Michelson interferometry. We observe (1) a transmission decrease ($\Delta $T/T) of about 5 {\%} at around 100 kV/cm incident field strength in bare GaAs wafers and (2) a transmission decrease of more than 30 {\%} over the incident field amplitude range from 40 to 120 kV/cm in nano-antenna-on-GaAs samples. Our experimental study demonstrates that strong THz pulses induce nonlinear THz absorption in intrinsic GaAs. The nonlinear THz effects are intensified by the field enhancement in a nano-antenna array. [Preview Abstract] |
Saturday, May 3, 2014 3:00PM - 3:12PM |
G1.00007: Terahertz Spectroscopy of Metal-Insulator Transition in Vanadium Dioxide Andrew Stickel, Zack Thompson, Younggyun Jeong, Michael Paul, Ali Mousavian, Dai-Sik Kim, Yun-Shik Lee Vanadium Dioxide is an attractive material for high-speed optical and electrical switching as it undergoes a metal-insulator transition near room temperature (340 K). We examine the phase transition using free-space THz transmission spectroscopy. THz probe is sensitive to the metal-to-insulator transition, because the insulating phase is transparent at THz frequencies while the metal phase is highly reflective. We demonstrate that THz transmission exhibits hysteresis of the metal-insulator transition during a temperature cycle. The phase transition gives rise to not only a reduction in transmission but also a spectral broadening as temperature increases. [Preview Abstract] |
Saturday, May 3, 2014 3:12PM - 3:24PM |
G1.00008: ABSTRACT WITHDRAWN |
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