Bulletin of the American Physical Society
2005 APS March Meeting
Monday–Friday, March 21–25, 2005; Los Angeles, CA
Session D35: Nanophotonic Materials, Nonlinear Optics and Spectroscopy I |
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Sponsoring Units: DCP Chair: Michael D. Barnes, Univ. Massachusetts Room: LACC 511B |
Monday, March 21, 2005 2:30PM - 3:06PM |
D35.00001: Photonic Crystal Devices for Quantum and Nanoscale Photonics Invited Speaker: Photonic crystal structures can be built to operate in two opposite regimes: one is a suppression of photon states inside the photonic band gap, and the other is a large enhancement of the density of photon states. Both regimes are of consequence to a number of applications in nanoscale and nonlinear optics, as well as to photonic quantum information technologies. Our work on the employment of photonic crystals to build hardware of solid-state photonic quantum information systems, as well as to construct miniaturized optical devices will be reviewed in this talk. We have demonstrated sources of single photons on demand based on quantum dots in micropost microcavities that exhibit a large spontaneous emission rate enhancement (Purcell factor of five) together with a small multi-photon probability (2{\%} compared to a Poisson-distributed source of the same intensity). We have also tested the indistinguishability of emitted single photons from such a source through a Hong-Ou-Mandel-type two-photon interference experiment, and found that consecutive photons exhibit a mean wave-packet overlap as large as 0.81, making this source useful in a variety of experiments in quantum optics and quantum information. The applications of such a device include secure quantum cryptography and linear optical quantum computation. We have also developed two-dimensional photonic crystal microcavities of finite depth with embedded quantum dots that exhibit large quality factors ($\sim $3000) together with small mode volumes ($\sim $0.5($\lambda $/n)$^{3})$ and with a maximum field intensity in the high-index region, which is of importance for enhanced interaction with quantum dot excitons. We have performed spectroscopy on a single quantum dot coupled to such a cavity, and demonstrated a very strong modification of its radiative properties, as well as a single-photon generation on demand. A strong interaction between a quantum dot exciton and the field enabled by such a microcavity is of importance for construction of single photon sources with improved efficiency, visibility, and speed, as well as for construction of entangled photon sources. Finally, we will also discuss some of our ongoing work on the integration of many photonic crystal components into functional circuits and devices, such as two-dimensional coupled arrays of photonic crystal microcavities for miniaturized lasers or sensors, or integration of photonic crystal cavities and waveguides for quantum networking. [Preview Abstract] |
Monday, March 21, 2005 3:06PM - 3:42PM |
D35.00002: Cavity QED with Single Atoms and Photons Invited Speaker: H. Jeff Kimble Across a broad front in physics, an important advance in recent years has been the increasing ability to observe and manipulate the dynamical processes of individual quantum systems. In this endeavor, an important physical system has been a single atom strongly coupled to the electromagnetic field of a high-$Q$ cavity within the setting of cavity quantum electrodynamics (cavity QED). Because of several unique advantages, cavity QED is playing an important role in the new science of quantum information, such as for the realization of complex quantum networks and for the investigation of quantum dynamics of single quantum systems. My presentation will describe recent advances in the Quantum Optics Group at Caltech related to strong coupling for single atoms and photons and to applications in quantum information science [1-5]. This research is supported by the National Science Foundation PHY-0140355, by the Caltech MURI for Quantum Networks administered by the ARO, and by the Advanced Research and Development Activity (ARDA). \begin{thebibliography}{9} \bibitem{mckeever03a} \textquotedblleft State-Insensitive Cooling and Trapping of Single Atoms in an Optical Cavity,\textquotedblright\ J. McKeever, J.R. Buck, A.D. Boozer, A. Kuzmich, H.-C.Nagerl, D.M. Stamper-Kurn, H.J. Kimble, Phys. Rev. Lett. \textbf{90}, 133602 (2003). \bibitem{mckeever03b} \textquotedblleft Experimental Realization of a One-Atom Laser in the Regime of Strong Coupling,\textquotedblright\ J. McKeever, A. Boca, A. D. Boozer, J. R. Buck, and H. J. Kimble, Nature \textbf{425}, 268 (2003). \bibitem{mckeever04a} \textquotedblleft Deterministic Generation of Single Photons from One Atom Trapped in a Cavity,\textquotedblright\ J. McKeever, A. Boca, A. D. Boozer, R. Miller, J. R. Buck, A. Kuzmich, and H. J. Kimble, Science \textbf{303}, 1992 (2004). \bibitem{mckeever04b} \textquotedblleft Determination of the Number of Atoms Trapped in an Optical Cavity,\textquotedblright\ J. McKeever, J. R. Buck, A. D. Boozer, and H. J. Kimble, Phys. Rev. Lett. \textbf{92}, 143601 (2004). \bibitem{boca04} \textquotedblleft Observation of the Vacuum-Rabi Spectrum for One Trapped Atom,\textquotedblright\ A. Boca, R. Miller, K.~M. Birnbaum, A.~D. Boozer, J. McKeever, and H.~J. Kimble, quant-ph/0410164. \end{thebibliography} [Preview Abstract] |
Monday, March 21, 2005 3:42PM - 3:54PM |
D35.00003: Electrically Driven Single Photons at Room Temperature Robert M. Dickson, Jose I. Gonzalez, Tae-Hee Lee, Jie Zheng, Michael D. Barnes, Yasuko Antoku The high demand for practical quantum information processing has sparked a search for novel nanophotonic materials in which single-photon basis states may be easily prepared, manipulated, and characterized. Created within electromigration-induced break junctions, individual electrically-contacted several-atom gold nanoclusters reveal antibunched electroluminescence consistent with single-photon emission. Electrically-driven operation at room temperature, low bleaching, and high data rates with sub-ns emission lifetimes make this system a convenient platform for study of nanoscale charge transport and applications of quantum light emission. [Preview Abstract] |
Monday, March 21, 2005 3:54PM - 4:06PM |
D35.00004: A Gallium Nitride Single-Photon Source Stephan Goetzinger, Charles Santori, Yoshihisa Yamamoto, Satoshi Kako, Katsuyuki Hoshino, Yasuhiko Arakawa Nitride semiconductors have emerged as important materials for blue and ultraviolet light-emitting diodes with numerous commercial applications. However, their large bandgaps make these materials also interesting for quantum information applications, such as quantum cryptography. We report on a single-photon source based on a gallium nitride semiconductor quantum dot emitting at a record-short wavelength of 357 nm. The power dependence of the second order coherence function suggests a two-level model for photon antibunching, where the antibunching timescale converges to the exciton decay time in the weak-excitation limit. This is supported by fluorescence lifetime measurements on single quantum dots. In temperature dependent measurements, photon antibunching was observed up to about 75 K. At higher temperatures, spectral broadening, which is likely enhanced by the large built-in electric field, eliminates the possibility of isolating a single optical transition. In a pulsed experiment at 10 K, we estimated a suppression of the two-photon emission probability to about 25{\%} compared to a poissonian source. [Preview Abstract] |
Monday, March 21, 2005 4:06PM - 4:42PM |
D35.00005: Harnessing nonlinear optical phenomena for image-resolution enhancement Invited Speaker: Nonlinear optics offers the researcher a remarkable range of opportunities for generating light with interesting, novel, and useful properties. In particular, twin beams generated via spontaneous optical parametric down-conversion exhibit unique quantum-correlation features that are of interest in the context of imaging. Photons are emitted in pairs in an entangled quantum state. Twin beams have found use in optical coherence tomography (OCT) as well as in quantum-optical coherence tomography (QOCT), a new method for carrying out tomographic measurements of objects with dispersion-cancelled resolution. Achieving high axial resolution in these coherence-based imaging systems requires the use of light with a broad spectral profile. The twin-beam spectral profile is mediated by the nature of the nonlinear optical material, by the geometry of the optical arrangement, and by the spatial profile of the pump laser radiation. A broad spectral profile can be generated by making use of a chirped quasi-phase-matching nonlinear crystal structure, non-collinear down-conversion, and a tightly focused laser pump. We present the results of simple OCT and QOCT experiments that demonstrate submicron axial resolution. The results confirm that the quantum technique exhibits immunity to dispersion, and additionally offers a factor of two enhancement in resolution, in accordance with theoretical expectations. [Preview Abstract] |
Monday, March 21, 2005 4:42PM - 4:54PM |
D35.00006: Nantennae: Far-field coherent interactions between pairs of oriented polymer nanostructures Michael Barnes We demonstrate for the first time realization of a prototypical \textit{nanoscale phased-antennae array} using pairs of z-oriented polymer nanostructures. Far-field photonic coupling between pairs of oriented luminescent polymer nanostructures is manifested by a modulation in the fluorescence decay rate as a function of interparticle distance, closely resembling the interaction between two classical (macroscopic) coupled antennae. However, unlike classical emitters, previously measured photon-pair correlation statistics indicate that the interaction between oriented nanostructures is mediated by single-photon states. Our experiments, performed under ambient conditions, demonstrate the feasibility of a fully scalable polymer-based nanophotonic system. [Preview Abstract] |
Monday, March 21, 2005 4:54PM - 5:06PM |
D35.00007: Ultrafast Transient-Absorption Studies of Spatially Confined Conjugated Oligomers David Bussian, Alexander Mikhailovsky, Bin Liu, Guillermo Bazan, Steven Buratto We will report on femtosecond transient-absorption (TA) studies of a series of oligophenylenevinylene molecules (NROPV) and a confined system wherein four oligomers are bound via a tetrahedral carbon core (TNROPV). TA spectra and dynamics for a span of pump fluences will be presented for both NROPVs and TNROPVs. Our data shows pronounced power dependent features present in TNROPV which we attribute to confinement induced coupling. These studies present a unique perspective on coupling in spatially extended conjugated molecules that is intermediate between that of isolated chromophores and bulk films. Furthermore, they have helped to clarify the fundamental description of the excited state(s) present in these conjugated oligomer structures. [Preview Abstract] |
Monday, March 21, 2005 5:06PM - 5:18PM |
D35.00008: Exciton dynamics in paracyclophane coupled dimers Jeremy Maddox, Jeongho Kim, Andrew Moran, Janice Hong, Guillermo Bazan, Norbert Scherer, Shaul Mukamel Understanding and manipulating through-space electronic communication within aggregates of organic fragments with delocalized bonding structures can impact a range of nanotechnology applications. However, interrogating aggregates of this type has encountered multiple difficulties in the past, ranging from heterogeneity of environments in the solid to the ill-defined geometry of intermolecular contacts in solution. These difficulties are circumvented by designing aggregates which contain [2.2]paracyclophane contacts among molecular units with well-defined architectures and dimensions. These offer excellent control over the distance and relative orientation of the participating units and provide a model system for detailed examination of the molecular structure-function relationship of conducting polymeric materials. We present a comparative experimental and theoretical study of a model complex consisting of two (oligo)phenylenevinylene chromophores that are strongly coupled through a paracyclophane junction. Ultrafast pump-probe anisotropy measurements are compared with numerical simulations to investigate the nature of exciton dynamics in strongly coupled chromophores. [Preview Abstract] |
Monday, March 21, 2005 5:18PM - 5:30PM |
D35.00009: Unified treatment of fluorescence and Raman scattering processes near metal surfaces Peter Johansson, Hongxing Xu, Mikael Kall We performed a general model study [1] of surface-enhanced resonant Raman scattering and fluorescence, focusing on the interplay between electromagnetic (EM) effects and the molecular dynamics as treated by a density matrix calculation. The model molecule has two electronic levels, is affected by radiative and non-radiative damping mechanisms, and a Franck-Condon mechanism yields electron-vibration coupling. Placing the molecule near two Ag nanoparticles leads to enhanced coupling to the EM field, and the Raman scattering can for realistic parameter values increase by some 10 orders of magnitude (to $\sim10^{-14}$ cm$^2$) compared with the free-space case. Also the fluorescence cross section grows with increasing EM enhancement, however, at a slower rate, and this increase eventually stalls when non-radiative decay processes become important. Finally, we find that anti-Stokes Raman scattering is possible with strong incident laser intensities, $\sim 1$ mW/$\mu$m. \\ {[1]}. H. Xu, X.-H. Wang, M. P. Persson, H. Q. Xu, M. K\"all, and P. Johansson, to appear in Phys.\ Rev.\ Lett. [Preview Abstract] |
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D35.00010: Single-Molecule Electroluminescence with STM. Gueorgui Nazin, Shiwei Wu, Xiaohui Qiu, Wilson Ho The electron current of a scanning tunneling microscope (STM) is used to excite electroluminescence of individual Zn-Etioporphyrin-I and Mg-porphine molecules adsorbed on an ultrathin Al$_{2}$O$_{3 }$film grown on the NiAl(110) surface. Al$_{2}$O$_{3 }$film acts as a spacer reducing the quenching of luminescence by the metal substrate. The electroluminescence spectra show well-defined features attributable to vibrational excitation of the molecules. Electroluminescence is sensitive to the molecular adsorption configuration as well as to the position of the STM tip above the molecule. A clear correlation with the corresponding differential conductance spectra is observed. [Preview Abstract] |
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