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 R3: EIT and Slow Light |
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Chair: Deniz Yavuz, University of Wisconsin Room: Gilmer Hall 190 |
Friday, May 22, 2009 10:30AM - 10:42AM |
R3.00001: Studies on negative refractive index without absorption Renuka Rajapakse, Susanne Yelin We study suitable systems for negative refractive index with minimal absorption. We suggest a modified level scheme of atoms, excitons or polar molecules to study negative refractive index without absorption. Quantum interference effects to suppress absorption and introduce chirality are discussed, and we attempt to find optimal densities of media that will give us negative refractive index without absorption. [Preview Abstract] |
Friday, May 22, 2009 10:42AM - 10:54AM |
R3.00002: Multi-Soliton Pulse Areas and the Bright-Dark Basis E. Groves, J.H. Eberly We study the fully coherent interaction of four short optical pulses propagating through a particular four-level medium. We present an exact analytic solution for this system which incorporates elements of $V$- and $\Lambda$-type systems. In the early stages of propagation, a single pair of solitons drives transitions in the atoms while farther into the medium the second pair of pulses is amplified as the first pair is depleted. Throughout the medium there are three stable ``total'' pulse areas. Our numerical solutions show that pulse transfer (the amplification of two pulses at the expense of the other two) occurs for a variety of input pulse shapes and areas along with SIT-type pulse reshaping. As in the three-level case examined by Clader and Eberly (2008), we find that our four-level system can be described in terms of bright and dark states. Working in the bright-dark basis we show that temporally-matched pulses obey a four-pulse area theorem and that the three pulse areas control the evolution of the system. [Preview Abstract] |
Friday, May 22, 2009 10:54AM - 11:06AM |
R3.00003: Magneto-optical control of the speed of light Anil Patnaik, Paul Hsu, Sukesh Roy, James Gord To control the group velocity of separate polarization components of light, we envision the use of a homogeneous magnetic field in conjunction with a single resonant laser of relatively high intensity. We show that this method is effective in controlling dispersion in an atomic system having a V-configuration with Zeeman sublevels as the excited states. We demonstrate such control via the interaction of monochromatic linearly polarized light and a moderately strong magnetic field with $^{87}$Rb atoms. Our system can function as a delay-splitter device that splits the signal into two polarization components with their delays controlled magneto-optically. [Preview Abstract] |
Friday, May 22, 2009 11:06AM - 11:18AM |
R3.00004: Electromagnetically induced transparency involving Rydberg states in a Rb microcell James Shaffer, Harold K\"ubler, Thomas Baluktsian, Alexi Charnukha, Christian Urban, Robert L\"ow, Tilman Pfau Small glass cells filled with Rb vapor are promising candidates for few photon nonlinear optics and quantum information processing using Rydberg states and the dipole blockade effect. Dipole blockade is a consequence of the strong interaction between two Rydberg atoms which can detune the Rydberg atom transition off resonance (pair excitation vs. single atom excitation). As a result of dipole blockade, only one Rydberg excitation is possible within a volume characterized by the blockade radius (typically a few microns), which is determined by the laser bandwidth and the Rydberg atom interaction strength. The effect is a nonlinear one that can be used as a tool to entangle atoms. Similar to atom entanglement, an atomic vapor confined on a length scale comparable to the blockade radius can be used like quantum wells (2D), quantum wires (1D) and quantum dots (0D) e.g. to realize a single photon source. We present measurements of electromagnetically induced transparency (EIT) in Rb vapor cells with thicknesses on the order of the blockade radius. We use the observed EIT to investigate the effects of the confinement in these vapor cells. The experiments show that coherent dynamics involving Rydberg states are possible in micro cells above room temperature. [Preview Abstract] |
Friday, May 22, 2009 11:18AM - 11:30AM |
R3.00005: Experimental study of memory decay in an optically dense EIT medium Nathaniel Phillips, Irina Novikova, Alexey Gorshkov In a typical quantum memory scheme that is based on Slow Light via Electromagnetically Induced Transparency, a strong control field is used to map a weak probe pulse onto a long-lived atomic ground state coherence (i.e., ``spin wave''), which is then stored for some time during which all laser fields are turned off. After this storage time, the spin wave is retrieved into a photonic mode by reapplication of a control field. The maximally achieved storage time and efficiency is crippled by the spin wave's decoherence. Theoretically, one can measure the spin wave decay rate by varying the storage time, detecting the retrieved signal field, and computing the exponential decay of the storage efficiency. Experimentally, however, things are more complicated. We perform this measurement in a buffered vapor cell of Rb-87, and investigate parameters that connect the storage efficiency decay rate to the fundamental decoherence rate of the Rb-87 $5^{2}$S$_{1/2}$ hyperfine state. [Preview Abstract] |
Friday, May 22, 2009 11:30AM - 11:42AM |
R3.00006: Electromagnetically induced transparency and four-wave mixing in an optically dense atomic vapor Irina Novikova, Nathaniel Phillips, Alexey Gorshkov We show that resonant four-wave mixing (FWM), which is enhanced in optically dense atomic medium under electromagnetically induced transparency (EIT) conditions, can strongly modify both cw spectra and the dynamics of the pulse propagation. In particular, we investigate the possibility to reduce the negative effects of FWM in EIT-based quantum memory. We also discuss how some of the observed features can be described by a simple theoretical model. [Preview Abstract] |
Friday, May 22, 2009 11:42AM - 11:54AM |
R3.00007: Controlling Light with Light: Efficient Energy Transfer between Laser Beams by Stimulated Raman Scattering Youbo Zhao, Tana E. Witt, Robert J. Gordon Efficient energy transfer between two intersecting ultrafast laser beams is reported. This effect is observed when the linearly polarized beams are focused in air and intersect at an acute angle. This phenomenon is attributed to plasma-mediated forward stimulated Raman scattering. Depletion of the pump beam increases with seed energy and is facilitated by supercontinuua generated by both pulses. Pump depletion as high as 57{\%} is observed. Amplification of the seed pulse depends on the polarization directions of the two lasers and the delay between the pulses. Interaction between the laser beams results also in pulse compression, rotation of the polarization plane, and spectral broadening of the seed laser. [Preview Abstract] |
Friday, May 22, 2009 11:54AM - 12:06PM |
R3.00008: Cross correlation between entangled photon pairs from four-wave mixing in a Warm Ensemble of Rubidium Tommy Willis, Francisco Willis, Daniel Hemmer, Steven Rolston, Luis Orozco We investigate correlated photon-pair generation by spontaneous four-wave mixing from a continuously pumped warm ensemble of rubidium atoms. The correlated pairs occur at 780 nm and 1367 nm. We find that the temporal character of the cross correlation of the emitted photons can be modified by varying the pump laser detunings and powers. The cross-correlation function exhibits quantum beats that reflect the hyperfine structure of the intermediate level. Selective excitation of one of those levels can erase the oscillation. We find that the envelope of the cross- correlation function depends on the spectral features of the thick sample and the modification of the absorption from optical pumping processes. [Preview Abstract] |
Friday, May 22, 2009 12:06PM - 12:18PM |
R3.00009: All-Optical Modulation of Four Wave Mixing in a Rb-Filled Hollow-Core Photonic Band-Gap Fiber Pablo Londero, Vivek Venkataraman, Amar Bhagwat, Aaron Slepkov, Alexander Gaeta Hollow waveguides are capable of tightly confining vapors and light fields over large interaction lengths to generate exceptionally high nonlinearities that are highly sensitive to perturbations. We have previously shown that a Rb-filled hollow-core fiber can generate high optical depths resulting in four wave mixing (FWM) gains greater than 100 at microwatts of pump power. Here, we show that the introduction of a weak, resonant switching field perturbs the effective third-order susceptibility and produces a modulation of a weak probe undergoing FWM amplification on the D1 transition. Modulation is observed over the full FWM bandwidth of 100 MHz, which implies a system response time of 1.6 ns. We observe 3 dB attenuation of the output probe power with 650 nW of switching pump power. From these results, we extrapolate that switching occurs with 3600 photons and a switching energy density of 23 photons per atomic cross-section. [Preview Abstract] |
Friday, May 22, 2009 12:18PM - 12:30PM |
R3.00010: Pulse Propagation in Four-Level Atomic Systems Studied in light of Three-Level Doublets Tony Abi-Salloum, Seth Meiselman, J.P. Davis, Frank A. Narducci Based on our understanding of coherent effects such as Electromagnetically Induced Transparency (EIT) and Autler-Townes (AT) in three-level systems (Lambda, Cascade, Vee) we study the propagation of a probe pulse in a variety of four-level systems. Specifically, we study two ``N'' schemes: one in which the probe field couples the ``outer'' levels and one in which the probe couples two of the ``inner'' levels. Surprising, although these systems appear different, they exhibit very similar steady state behavior. The Physics becomes clear in a semi-dressed states picture where each four-level system reduces to two three-level systems. The semi-dressed states picture analysis is complemented with a numerical work that follows from the discretization in time and space of the fields and density matrix elements equations. The systems under study exhibit slow and fast light behaviors with a dramatic transition between two positive and negative group velocity regimes that are explained in the adopted picture. [Preview Abstract] |
Friday, May 22, 2009 12:30PM - 12:42PM |
R3.00011: Dirac dynamics of stationary light in 1D: Klein tunneling and Zitterbewegung Johannes Otterbach, Razmik Unanyan, Michael Fleischhauer In order to create nonlinear interactions between single photons in an atomic ensemble it is necessary to have long interaction times and high electric fields per photon. One possibility to achieve this is to use stationary light in setups exhibiting electromagnetically induced transparency (EIT). We analyze the ultimate limit of compression of stationary photonic excitations and show that at pulse lengths as small as the absorption length the probe pulses have to be described by an effective Dirac equation for a two-component spinor. The effective speed of light and the effective mass entering this equation can be controlled externally and can be made many orders of magnitude smaller than the corresponding quantities for graphene, fermionic atoms and electrons. Consequently relativistic behavior can be observed at much larger length scales and much lower energies. As a result of this the compression limit, given by the corresponding Compton length, can be macroscopic. We discuss certain predictions of the Dirac theory as e.g. Klein tunneling and the Zitterbewegung. [Preview Abstract] |
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