Bulletin of the American Physical Society
75th Annual Meeting of the Southeastern Section of APS
Volume 53, Number 13
Thursday–Saturday, October 30–November 1 2008; Raleigh, North Carolina
Session PB: Optical Physics |
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Chair: John Yukich, Davidson College Room: Holiday Inn Brownstone Washington |
Saturday, November 1, 2008 10:30AM - 10:42AM |
PB.00001: UV Induced Photopatterning of Poly-L-Lysine and Photodegradation of Ppolymethylmetacrylate Jean Michel Taguenang, Aschalew Kassu, Redahegn Sileshi, Fernando Calzzani, Anup Sharma We present the effects of UV irradiation on two different organic polymers. In the first part, deep UV lithography on poly-L-lysine thin films is used to generate microarrays with enhanced hydrophilicity. This is manifested as adsorption of ambient humidity from air by areas exposed to UV fluence around 5 J$/$cm2 and is made visible by phase-contrast microscopy. Kinetics of adsorption is investigated by a novel technique involving fabrication of submicrometer hydrophilicity grating by two-beam UV interferometry. In an aqueous colloidal medium, gold and polystyrene microspheres preferentially attach to areas that are relatively less hydrophilic, i.e., those areas not exposed to UV light. This provides a method for fabricating micro- and nanoporous arrays with controlled porosity. Laser-induced fluorescence, Raman and absorption spectroscopies are used to investigate reversible degradation of transmission in PMMA optical fibers. When exposed to 254 nm light, transmission of PMMA fiber in 400--800 nm range shows a significant change in attenuation. Over a period of 10 days following UV exposure, transmittance of the plastic fiber recovers to a significant fraction of its pre-exposure value. Exposed exhibits strong laser-induced fluorescence with 488 nm laser which spans from 450 nm to 750 nm and peaks at 580 nm. [Preview Abstract] |
Saturday, November 1, 2008 10:42AM - 10:54AM |
PB.00002: Polybutadiene polymer as a photopatterning substrate Aschalew Kassu, Jean Michel Taguenang, Fernando Calzzani, Redahegn Sileshi, Anup Sharma Surface relief gratings produced on planar substrates have been widely investigated for their application as a holographic recording medium. In this work, surface relief holographic gratings are fabricated on polybutadiene-coated walls of a cell filled with an aqueous solution of azo-dye-labeled phospholipid as well as rhodamine 6G. This deposition as a grating pattern is photo-induced in a dye-solution by holographic interference of low power 488 nm light from an argon-ion laser. Dynamics of this aqueous-phase grating deposition is investigated for various concentrations of the dye. A plausible mechanism of grating formation involves photochemical reaction of polybutadiene substrate with the laser-excited dye. Lithographic masks are used to show that photochemical pattern on the substrate is an exact replica of the light intensity distribution and so the technique can be used for holographic recording as well as for biomolecular applications. Surface relief structure of the grating is characterized with an atomic force microscope. [Preview Abstract] |
Saturday, November 1, 2008 10:54AM - 11:06AM |
PB.00003: Investigating Capacitance Behavior of Nanomaterials through Split-tip Scanning Capacitance Microscopy Beverly Clark III, Hans Hallen A split-tip Near-field Scanning Optical Microscope (NSOM) probe is used to measure capacitance. We build a model for the instrument by solving Poisson's equation for a simplified system using the finite element program Femlab. The governing equations and boundary conditions are paramount in obtaining a converging solution. Values obtained from a simple capacitor model are compared to calculated values found from the Scanning Capacitance setup. The split-tip capacitance values will be compared with measured values from the Scanning Conductivity Microscopy (SCM) experimental setup. This scanning probe microscope uses two electrically-isolated electrodes fabricated on one split-tip probe to investigate local electrical behavior of nanostructures. The split-tip probe, which we have recently developed, is optimized for light coupling into a particular region of a nanostructure while non-contact capacitance measurements are simultaneously made between the two electrodes. The capacitance is influenced by the presence of a conducting region on the surface beneath the electrodes. The capacitance coupled or scanning conductivity mode allows rapid characterization of large areas of the sample so that regions of interest can be identified for further study. The finite element model aids in the quantification and understanding of the data. [Preview Abstract] |
Saturday, November 1, 2008 11:06AM - 11:18AM |
PB.00004: Optimal control of light pulse storage and retrieval in atomic vapor Nathaniel Phillips, Irina Novikova, Alexey Gorshkov Efficient and reliable quantum communication will require the coherent control of individual photons. As a step toward this objective, we have demonstrated promising techniques that involve using the dynamic form of electromagnetically induced transparency to optimally and reversibly map arbitrary classical pulse shapes of light onto an ensemble of hot Rubidium atoms. One technique employs time-reversal to determine, using an iterative procedure, the optimally-stored signal field for a given control field. Another method makes use of the one-to-one mapping between the decayless spin modes of the atoms and the signal field to calculate the optimal control field for a given signal field. We show that both techniques equivalently obtain optimal memory efficiency for a given optical depth. We observe good agreement with theoretical predictions for lower optical depth ($<15$), but memory efficiency falls below predictions at higher optical depths ($>25$). We analyze possible effects responsible for this reduced memory, such as resonant four-wave mixing, ac-Stark shifts, etc, and present the results of current investigations into the optical depth dependence of such phenomena. [Preview Abstract] |
Saturday, November 1, 2008 11:18AM - 11:30AM |
PB.00005: ABSTRACT HAS BEEN MOVED TO HA.00064 |
Saturday, November 1, 2008 11:30AM - 11:42AM |
PB.00006: ABSTRACT HAS BEEN MOVED TO HA.00063 |
Saturday, November 1, 2008 11:42AM - 11:54AM |
PB.00007: Silicides for infrared surface plasmon resonance biosensors J.W. Cleary, R.E. Peale, W. Buchwald, R. Soref Biomolecules on a conductor strongly affect its surface plasmon modes, providing for real-time sensing of biomolecules. We consider silicides for IR plasmonic biosensors. The lower plasma frequency of silicides relative to metals shifts the plasmon dispersion curve farther from the light line in the IR, enhancing resonances in the attenuated total reflection (ATR) configuration. Better mode confinement on silicides increases sensitivity to near-surface biomolecules. Higher silicide surface impedance gives more efficient IR-to-plasmon coupling by gratings. We experimentally determine the IR permittivity for industrially-relevant Pt-, Pd-, Ni-, and Ti-silicides. IR surface plasmon properties including mode profiles, propagation lengths, ATR lineshapes, and grating coupling efficiencies are then calculated. Experimental surface plasmon resonance data at CO$_{2}$ laser wavelengths are then presented for both ATR and grating configurations. [Preview Abstract] |
Saturday, November 1, 2008 11:54AM - 12:06PM |
PB.00008: The Terahertz Spectrum of Nitric Acid Paul Helminger, Douglas T. Petkie, Ivan Medvedev, Frank C. De Lucia A solid state tripler has been put into operation on the FASSST system at Ohio State University. This device converts the microwave input power from a swept OB-30 backward wave oscillator (240-375 GHz) to terahertz output power. We have used this device to record the rotational spectrum of nitric acid in the 875-1100 GHz range. Spectral assignments have now been made for the molecule in the ground, v9=1, and v8=1 states, and work is underway on the assignment of spectral lines in several other excited vibration states. Results will be reported. [Preview Abstract] |
Saturday, November 1, 2008 12:06PM - 12:18PM |
PB.00009: Application of the Anisotropic Bond Model to a Single Bond Attached to a Sphere E.J. Adles, D.E. Aspnes The configuration consisting of a single adatom on a sphere of dimensions small compared to the relevant wavelength of light is of interest to both surface-enhanced Raman scattering (SERS) and second-harmonic generation (SHG). Here we apply our recently developed anisotropic bond model (ABM) of nonlinear optics (NLO) to investigate this configuration. The ABM provides a simple means for calculating NLO properties by factoring the problem into the fundamental 4-step process of optics: first, determine the local field at the bond charge site; second, solve the anharmonic force equation for the bond charge; third, calculate the radiation from the accelerated bond charge; fourth, superpose the radiation from all charges. This factorization is possible because typical NLO signals occur at different energies with intensities that are orders of magnitude weaker than the driving fields. Therefore, NLO problems are actually simpler than linear-optics problems where all four steps must be solved self-consistently. For SERS, the calculations show that the strength of the exciting field is enhanced via the ``lightning-rod'' effect, but no such enhancement occurs for the emerging radiation. [Preview Abstract] |
Saturday, November 1, 2008 12:18PM - 12:30PM |
PB.00010: Magnetic field structure in photodetachment from the lowest threshold of the O$^{-}$ ion John N. Yukich, Anne Joiner, Robert H. Mohr Numerous experiments have examined photodetachment in a magnetic field at the $^{2}$P$_{3/2 }\to \quad ^{3}$P$_{2}$ threshold of ions such as S$^{-}$ and O$^{-}$. The threshold energy is known as the atom's \textit{electron affinity}. Many of these experiments have visually resolved cyclotron and Zeeman structure in the detachment cross section. We report on an experiment that for the first time has resolved magnetic field structure in detachment at the lowest-lying threshold for the O$^{-}$ ion, the $^{2}$P$_{1/2 }\to \quad ^{3}$P$_{2}$ threshold. Our experimental apparatus includes a Penning ion trap in which the ions are created, trapped and stored, and a single-mode, amplified diode laser. Our observations also yield a quantitative measurement for the threshold energy. [Preview Abstract] |
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