Bulletin of the American Physical Society
APS March Meeting 2011
Volume 56, Number 1
Monday–Friday, March 21–25, 2011; Dallas, Texas
Session T4: Keithly Award Session |
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Sponsoring Units: GIMS Chair: Timothy Graber, University of Chicago Room: Ballroom A4 |
Wednesday, March 23, 2011 2:30PM - 3:06PM |
T4.00001: Joseph F. Keithley Award For Advances in Measurement Science Talk: Beyond the Fringe: measuring ultrafast optical pulses using spectral interferometry Invited Speaker: The ability to completely characterize ultrashort electromagnetic pulses has revolutionized the field of ultrafast optics, enabling both new technology and new science. The aim of pulse characterization is to infer the electric field of the pulse from measurements of quantities that rely on standard (relatively slow) photodetectors. Since the field is a fundamental entity in Maxwell's theory, it contains the most information one may obtain about a system probed by an optical pulse, and is, in this sense, much more valuable set of data than a measurement simply of the pulse energy or even the spectral or temporal intensity, Pulse measurement methods may be categorized as spectrographic and tomographic, by which the time-frequency phase space of the pulse is mapped, or interferometric, by which the phase is determined directly. Interferometry provides a sensitivity and robust approach affording a rapid, direct reconstruction algorithm that gives a provably unique solution to the complete space-time field. An important class of self-referencing interferometric are those based on spectral shearing, whereby two frequency shifter replicas of the test pulse are generated encoding the spectral phase derivative in the spectral interferogram resulting from their superposition. The nonlinear implementation of this approach is called spectral phase interferometry for direct electric-field reconstruction (SPIDER). SPIDER has shown itself to be an adaptable and robust method, gaining widespread application in all areas of ultrafast optics, from nonlinear microscopy to attoscience. Some essential concepts and history of the field will be presented, along with recent developments, illustrating applications in ultrafast source diagnosis and certification, dynamical spectroscopy, coherent control, imaging and materials processing. [Preview Abstract] |
Wednesday, March 23, 2011 3:06PM - 3:42PM |
T4.00002: High-Energy Sub-Cycle Waveform Synthesis and Characterization Invited Speaker: The control of atomic scale electronic motion by ultrafast optical electric field waveforms strong enough to mitigate the atomic Coulomb potential has broken tremendous new ground with the advent of phase controlled high-energy few-cycle pulse sources. Currently, such sources are based on Ti:sapphire amplifiers and hollow-core fiber post-compression or optical parametric chirped pulse amplification, together with optical gating techniques. Significant control of the waveform on sub-cycle time scales, however, requires a fully phase-controlled multiple-octave-spanning spectrum. Here, we present a first fully phase-controlled multi-octave-spanning source that supports gigawatt-peak-power isolated single-cycle waveforms based on pulse synthesis of two carrier-envelope phase (CEP) stable OPCPA systems. It is especially a challenge to fully characterize such ultrawide band waveforms. We apply two-dimensional spectral shearing interferometry (2DSI), which can measure the group delay between all spectral components of the synthesized pulse. [Preview Abstract] |
Wednesday, March 23, 2011 3:42PM - 4:18PM |
T4.00003: Generation, characterization and spectroscopic use of ultrashort pulses fully tunable from the deep UV to the MIR Invited Speaker: The impressive work of Ian Walmsley has brought us invaluable new possibilities for the full characterization of ultrashort pulses. Spectroscopy of physical, chemical and biological relevance does, however, need pulses far from the 800 nm Ti:sapphire wavelength used for testing SPIDER and its advanced versions. Fortunately, optical parametric amplification (OPA) allows for easy generation of fully tunable pulses. I will review our efforts, highlighting noncollinear OPA, i.e. NOPA, for visible pulses shorter than 10 fs, mixing into the UV down to below 200 nm at 20 fs duration and novel hybrid schemes to efficiently reach the middle IR. I will show that these schemes can be used equally well from kHz to MHz repetition rates. The tunable ultrafast pulses in turn also demand improvements in characterization. The UV range led us to use difference frequency generation instead of the sum frequency mixing employed in the original SPIDER. The lack of proper beam splitters and auto-referencing led us to the use of two auxiliary pulses and the avoidance of any additional chirp added to the test pulse. We termed this zero-additional-phase SPIDER, i.e. ZAP-SPIDER. Lately, with increased use of UV pulses, we came to the conclusion, that the ubiquitous two-photon-absorption can well serve as nonlinearity, at least in UV autocorrelation measurement. How do we use this for full characterization? Hopefully, Ian will tell us! Since the proof is known to be in the eating, I will demonstrate the success of our technical efforts with examples taken from ultrafast molecular dynamics. Highly pronounced vibronic wavepackets in the product of ultrafast excited state proton transfer and the very primary processes leading to homolytic and heterolytic bond cleavage will serve as easy to comprehend illustrations. [Preview Abstract] |
Wednesday, March 23, 2011 4:18PM - 4:54PM |
T4.00004: Probing Electron Correlation with Sequential Laser--Induced Tunnel ionization Invited Speaker: Since 1964 we have known that multiphoton ionization could be approximated by tunnel ionization for long wavelength light. Aside from re-collision, since then multiple ionization has been treated as successive, independent single ionization events. Our results show that this long-held belief is false. Tunnelling is highly directional and highly sensitive to the ionization potential (Ip) of the accessible ionic states (which itself can depend on the direction of ionization). Using rare gas atoms as examples, we show that laser induced tunnelling is suppressed or enhanced depending on how the field is applied. We image the hole left by the first tunnelling electron by measuring in the spatial correlation of the second electron. Laser induced tunnelling gives us experimental access to one of the most difficult to measure properties of matter -- electron-electron correlations [1]. \\[4pt] [1] A. Fleischer, H.J. W\"{o}rner, L. Arissian, L.R. Liu, M. Meckel, A. Rippert, R. D\"{o}rner, D.M. Villeneuve, A. Staudte and P.B. Corkum, unpublished results. [Preview Abstract] |
Wednesday, March 23, 2011 4:54PM - 5:30PM |
T4.00005: Pulse Propagation through Dispersive Optical Materials Invited Speaker: It is now possible to characterize the complete time-frequency behavior of optical pulses with unprecedented precision [1, 2]. The frequency content of optical pulses determines how they propagate through dispersive optical materials. In this talk, we review recent work on methods for dramatically modifying the velocity with which light pulses propagate through material systems. This modification can be so severe that one speaks of slow light, fast light, and backwards light depending on how the magnitude and sign of the group velocity compares to the vacuum speed of light c. We review the physical processes that can be used to achieve such a strong modification of the velocity of light, and we discuss the conceptual understanding of exotic propagation effects such as backwards propagation. We also review the implications of modified pulse velocities within the context of modern optical technology.\\[4pt] [1] Kane, D.J. and R. Trebino, Opt. Lett., 18 823 (1993)\\[0pt] [2] C. Iaconis and I. A. Walmsley, Opt. Lett., 23 792 (1998). [Preview Abstract] |
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