Bulletin of the American Physical Society
40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009; Charlottesville, Virginia
Session R4: Spectroscopy Techniques / MEMS |
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Chair: Mishkatul Bhattacharya, University of Arizona Room: Clark Hall 108 |
Friday, May 22, 2009 10:30AM - 10:42AM |
R4.00001: Population transfer between ground state and coherent superposition of excited states by spectrally shaped broadband pulses Sergey Zhdanovich, Evgeny Shapiro, Moshe Shapiro, John Hepburn, Valery Milner We demonstrate a method for executing complete, robust and selective population transfer from a single ground state to a coherent superposition of multiple excited states. The method is based on simultaneous execution of multiple adiabatic passages with shaped broadband laser pulses. It enables full control over the relative amplitudes and phases of the eigenstates in the target superposition. Our approach is experimentally implemented using $4s_{1/2} \rightarrow \{4p_{1/2}, 4p_{3/2}\}$ transition in atomic Potassium. We show that, unlike the excitation with unshaped pulses, our method is insensitive to overall laser intensity. Prospects of complete population transfer into shaped molecular wavepackets are discussed. [Preview Abstract] |
Friday, May 22, 2009 10:42AM - 10:54AM |
R4.00002: Narrowband spectroscopy by all-optical correlation of broadband pulses Xiaoji Xu, Stanislav Konorov, John Hepburn, Valery Milner High peak power ultrafast lasers are widely used in nonlinear spectroscopy but often limit its spectral resolution because of the broad frequency bandwidth of ultrashort laser pulses. Improving the resolution by achieving spectrally narrow excitation of, or emission from, the resonant medium by means of multi-photon interferences has been the focus of many recent developments in ultrafast spectroscopy. We demonstrate an alternative approach, in which high resolution is exercised by detecting narrow spectral correlations between broadband excitation and emission optical fields. All-optical correlation analysis, easily incorporated into the traditional spectroscopic setup, enables direct, robust and simultaneous detection of multiple narrow resonances with a single femtosecond pulse. [Preview Abstract] |
Friday, May 22, 2009 10:54AM - 11:06AM |
R4.00003: Influence of femtosecond dephasing on CARS coherence in various approximations Vladimir Malinovsky We discuss adiabatic passage implementations to maximize CARS coherence without making an assumption of adiabatic elimination of detuned excited electronic states. Also we analyze influence of fast femtosecond dephasing in the molecular samples on the results of proposed schemes. It is shown that the adiabatic method allows achieving chemical sensitivity with high resolution and can be used to obtain CARS signal with efficiently suppressed background in molecular systems with coherence times of several hundred of femtoseconds. [Preview Abstract] |
Friday, May 22, 2009 11:06AM - 11:18AM |
R4.00004: Two-color STIRAP in trapped-ion quantum states Chitra Rangan We show how two-color Stimulated Raman Adiabatic Passage (STIRAP) can be executed in an N-level quantum system. The system of choice is the trapped-ion system which can be modeled by a spin-half system coupled to a harmonic oscillator. The two-color fields are the those that produce the spin-flip ``carrier" transition, and the first red sideband transition. Generalization to multiple ions and the potential to produce quantum `gates' are investigated. [Preview Abstract] |
Friday, May 22, 2009 11:18AM - 11:30AM |
R4.00005: Efficiency of STIRAP as a function of buffer gas pressure: sodium in argon Jim L. Hicks, Susan D. Allen, Joey Burdin, William D. Murry, J. Bruce Johnson We present the dependence of the efficiency of the STIRAP process on sodium vapor as a function of the pressure of an argon buffer gas. These results elucidate the nature of how the coherent STIRAP process is spoiled by the incoherent process of random collisions. The transitions used for the pump and Stokes pulses are 3p ($^{2}$P$_{1/2}) \quad \leftarrow $ 3s ($^{2}$S$_{1/2})$ and 5s ($^{2}$S$_{1/2}) \quad \leftarrow $ 3p ($^{2}$P$_{1/2})$ respectively. Light to couple the states was produced by two synchronously pumped OPG/OPAs (pumped by the 355 nm light from a picosecond YAG). The light pulses were approximately 15 ps long and were near-Fourier-transform-limited. Fluorescence from the 5s state to both 3p states ($^{2}$P$_{1/2}$, $^{2}$P$_{3/2})$, from both 3p states to the 3s state, and from the 4p states to the 3s state was measured with a monochromator using a gated CCD to eliminate Rayleigh scattered light. [Preview Abstract] |
Friday, May 22, 2009 11:30AM - 11:42AM |
R4.00006: Cavity enhanced absorption spectroscopy using a broadband prism cavity and a supercontinuum source Paul S. Johnston, Kevin K. Lehmann We report the design and construction of a cavity enhanced absorption spectrometer using broadband Brewster's angle prism retroreflectors and a spatially coherent 500 nm to $>$1.75 $\mu $m supercontinuum excitation source. Using prisms made from fused silica an effective cavity reflectivity of $>$99.99{\%} at 1.064 $\mu $m was achieved. A proof of principle experiment was performed by recording the cavity enhanced absorption spectrum of the weak b-X (1$\leftarrow $0) transition of molecular oxygen at 14529 cm$^{-1}$ and the fifth overtone of the acetylene C-H stretch at 18430 cm$^{-1}$. CCD frames were integrated for 150 sec and 30 sec, with 3 frames (each 100 cm$^{-1}$ wide) and 1 frame (266 cm$^{-1}$ wide) required to observe the O$_{2}$ and C$_{2}$H$_{2}$ spectra, respectively. A rms noise equivalent absorption ($\alpha _{min})$ of 7.21x10$^{-8}$ cm$^{{\-}1 }$Hz$^{{\-}1/2}$ and 1.28x10$^{{\-}7}$ cm$^{-1 }$Hz$^{{\-}1/2}$ with full width half maximum line widths of 0.18 cm$^{-1}$ and 0.44 cm$^{-1}$ was achieved for the molecular oxygen band and acetylene overtone. [Preview Abstract] |
Friday, May 22, 2009 11:42AM - 11:54AM |
R4.00007: High resolution spectroscopy of Rb atoms in hollow-core fibers Aaron Slepkov, Vivek Venkataraman, Amar Bhagwat, Pablo Londero, Alexander Gaeta Recent demonstrations of light-matter interaction with atoms and molecules confined to hollow waveguides offer great promise to ultralow-light-level applications. The use of waveguides allows for tight optical confinement and orders of magnitude increases in interaction lengths. However, the combination of strong atom-photon interactions and nonuniformity of guided light modes gives rise to spectroscopic features that must be completely understood in order to take full advantage of the properties of such systems. We use light-induced atomic desorption to generate an optically-dense Rb vapor at room temperature inside the 6-$\mu $m core of a hollow-core photonic bandgap fiber. Saturable absorption spectroscopy elucidates large ac-Stark shifts, and the substantial power and transit-time broadening that occurs in this system. These effects persist at nW powers and thus provide a limit on the achievable linewidths. [Preview Abstract] |
Friday, May 22, 2009 11:54AM - 12:06PM |
R4.00008: Active feedback lock of a Fabry-Perot cavity to the emission of a single quantum dot John Lawall, Michael Metcalfe, Glenn Solomon Self-assembled quantum dots behave as artificial atoms that are spatially localized in a solid-state environment, with discrete energy levels that can be manipulated by external fields. By embedding them in a semiconductor cavity, the fluorescence can be made strong enough to lock a macroscopic Fabry-Perot cavity to the emission of a single quantum dot. We demonstrate here the ability to lock a cavity to a quantum dot with a mean transmitted photon flux of 4 kHz. For short integration times, the error signal is dominated by shot noise, and at long integration times, it is dominated by cavity drifts. We present an analytic approach to determining the optimum integration time and servo feedback characteristics. We will discuss the prospects for using a Stark shift to invert the situation and lock the emission wavelength of a quantum dot to a stable Fabry-Perot cavity. [Preview Abstract] |
Friday, May 22, 2009 12:06PM - 12:18PM |
R4.00009: Magnetic coupling of laser-cooled atoms to a micro-resonator Andrew Geraci, Ying-Ju Wang, Matthew Eardley, John Moreland, John Kitching The direct coupling of the spin-degrees of freedom of an atomic vapor to the vibrational motion of a magnetic cantilever tip has recently been demonstrated [1], and prospects for coupling a BEC on an atom-chip to a nano- mechanical resonator have been recently discussed [2]. Possible applications include chip-scale atomic devices, in which localized interactions with magnetic cantilever tips selectively influence or probe atomic spins. As a next step towards the realization of a strongly coupled ultra-cold atom- resonator system, we have constructed an apparatus to study the direct coupling between the spins of trapped laser-cooled Rb atoms and a magnetic tip on a micro-cantilever. The atoms will be loaded into a magnetic trap formed by the cantilever tip and external magnetic fields. The cantilever will be driven capacitively at its resonance frequency, resulting in a coherent precession of the trapped atomic spins with a matching Larmor frequency. Prospects for measuring the back-action of the ensemble of atomic spins on a cantilever beam will also be discussed. [1] Y.-J. Wang,M. Eardley, S. Knappe, J. Moreland, L. Hollberg, and J. Kitching, PRL 97, 227602 (2006). [2] P. Treutlein,D. Hunger, S. Camerer, T. W. Hansch, and J. Reichel, PRL 99, 140403 (2007). [Preview Abstract] |
Friday, May 22, 2009 12:18PM - 12:30PM |
R4.00010: Multi-color, Multi-path Optical Beam Steering Utilizing High Performance MEMS Mirrors Caleb Knoernschild, Changsoon Kim, Felix Lu, Jungsang Kim Scaling current atomic based quantum computer experiments beyond individual gate operations requires an efficient means of distributing laser resources across an array of trap sites. Micro-electromechanical system (MEMS) technology can provide the scalability and flexibility in an optical beam steering system to effectively share multiple, independent lasers among trap sites within a $1$D or $2$D qubit array. Controllable micro mirrors with broadband reflective metal coatings enable concurrent multi-wavelength beam steering along multiple beam paths as well as wavelength multiplexing along the same beam path. We demonstrate a MEMS based beam steering system that addresses $49$ locations in a $7$x$7$ array with two separate wavelengths at $635$ nm and $780$ nm. This system features switching speeds between lattice sites of $4$ $\mu$s and $-29$ dB residual optical intensity at neighboring array locations. [Preview Abstract] |
Friday, May 22, 2009 12:30PM - 12:42PM |
R4.00011: Coupling nanomechanical cantilevers to dipolar molecules Swati Singh, Mishkat Bhattacharya, Omjyoti Dutta, Pierre Meystre We investigate the coupling of a nanomechanical oscillator with ultracold dipolar molecules. We find theoretically that the cantilever can produce single-mode squeezing of the center-of-mass motion of an isolated trapped molecule and two-mode squeezing of the phonons of an array of molecules. This work opens up the possibility of manipulating dipolar crystals, and more generally, is indicative of the promise of nanoscale cantilevers for the quantum detection and control of atomic and molecular systems. [Preview Abstract] |
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