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Q 42.5 Do 17:30 HS 223
Spatial and temporal control of optical near field distributions
using femtosecond polarization pulse shaping — •W. Pfeiffer 1 ,
F.J. Garcia de Abajo 2 , and T. Brixner 3 — 1 Universität Würzburg,
Physikalisches Institut EP1, 97074 Würzburg, Germany — 2 Centro
Mixto CSIC-UPV/EHU, 20080 San Sebastian, Spain — 3 University of
California at Berkeley, Department of Chemistry, Berkeley, CA 94720,
USA
Optical near-field distributions are at the center of experimental techniques
such as scanning photon tunneling microscopy (STM) or near-field
two-photon fluorescence microscopy. Ultrahigh spatial resolution is provided
by making use of the optical field enhancement in the vicinity of a
sharp tip. We simulate the field distribution near an STM tip/sample geometry
under the irradiation with polarization-shaped femtosecond laser
pulses by means of the boundary-element method. This allows for the
first time to shape all three mutually orthogonal polarization components
of a femtosecond light pulse in a complex fashion. Using an evolutionary
algorithm, nonlinear signals and contrast ratios at specific points in
space can be enhanced by optimized light pulses. Apart from applications
in the above-mentioned near-field techniques, this offers the possibility
for three-dimensional quantum control on surface-adsorbed molecules,
accessing 3D wavefunction properties with light fields optimized in all
three polarization directions and along three spatial coordinates.
Q 42.6 Do 17:45 HS 223
Carrier-Envelope Phase Measurement using a Non Phase
Stable Laser — •Matthias Lezius 1,2 , Kevin O’Keeffe 1 , Peter
Jöchl 1 , Herwig Drexel 2 , Verena Grill 2 , and Ferenc Krausz 1
— 1 Institut für Photonik, Technische Universität Wien, Gusshausstr.
27/387, A-1040 Wien — 2 Institut für Ionenphysik, Universität
Innsbruck,Technikerstr. 25, A-6020 Innsbruck
We demonstrate that the phase between the carrier and the pulse envelope
of a few-cycle laser pulse can be retrieved from non phase stable
laser systems, provided that such laser pulses are about 5 fs long and the
repetition rate is in the order of 1kHz. Our approach is based on online
determination of the phase using f − 2f interferometry. By a comparison
of the self referencing interferometric signal with the photoelectron
current emitted into a 7 degree solid angle parallel to the laser polarization
we obtain the absolute value of the carrier envelope phase provided
that Coulomb correction for electron energies below 10eV can be taken
correctly into account.
Q 42.7 Do 18:00 HS 223
Determination of the carrier-envelope phase of ultrashort laser
pulses using metal surfaces — •C. Lemell 1 , P. Dombi 2 , X.-M.
Tong 3 , F. Krausz 2 , and J. Burgdörfer 1 — 1 Inst. f. Theoretical
Physics, Vienna University of Technology — 2 Photonics Inst., Vienna
University of Technology — 3 Dept. of Physics, Kansas State University
Q 43 Biophotonik und Laser in der Medizin
Many results of ultrashort-laser matter experiments strongly depend
on the relative phase ϕ of the field oscillations with respect to the peak
of the laser pulse. Until recently, determination of ϕ was limited by a
±π ambiguity and restricted to high-energy (≫ 1 µJ) pulses. Control
mechanisms for pulses at moderate intensity levels were missing. Our
simulations of ultrashort laser pulses interacting with metal surfaces
based on time dependent density functional theory [1] indicate that
photoemission from surfaces, especially in the multiphoton regime
(I < 10 13 W/cm 2 ), might be a promising candidate for measuring ϕ
for pulse durations τ shorter than 10 fs. To better understand this
surprising result we set up a classical trajectory Monte Carlo simulation
of the process including photon absorption by conduction band electrons
giving insight into the relative importance of underlying mechanisms.
First experiments [2] support out predictions.
This work has been supported by Fonds zur Förderung der wissenschaftlichen
Forschung under project no. FWF-SFB016.
[1] C. Lemell et al., Phys. Rev. Lett. 90, 076403 (2003).
[2] A. Apolonsky et al., submitted to Phys. Rev. Lett. (2003).
Gruppenbericht Q 42.8 Do 18:15 HS 223
Phase-locked chirped pulse optical parametric amplification
of 12 fs pulses from a Ti:sapphire oscillator — •Jens Biegert,
Christoph P. Hauri, Philip Schlup, and Ursula Keller —
Physik Department, Swiss Federal Institute of Technology (ETH),
Zürich, Switzerland
We present first results of direct chirped pulse optical parametric amplification
of 12-fs, 1.7 nJ pulses from a phase-locked Ti:sapphire oscillator.
The interaction is modeled with a 3D code and experimental
parameters agree well with the simulation. Preliminary experimental results
showed amplified spectra spanning a bandwidth of 160 nm with an
energy of 85 µJ (0.9 mJ pump at 400 nm), supporting a transform limited
pulse duration of 9.8 fs. Compression only led to 28 fs pulses, measured
with SPIDER, due to the limited optics bandpass (48 nm, supporting
21 fs) in our setup. Furthermore, we could confirm that the phase-lock
of the oscillator pulses is conserved in the amplification process, hence
this technique can potentially give access to phase-locked, high-energy
few-cycle pulses.
Zeit: Donnerstag 16:30–18:30 Raum: HS 224
Q 43.1 Do 16:30 HS 224
A single-nanoparticle biosensor based on light scattering
spectroscopy — •Gunnar Raschke 1 , Sandra Brogl 1 , Stefan
Kowarik 1 , Thomas Franzl 1 , Carsten Sönnichsen 1 , Thomas
A. Klar 1 , Jochen Feldmann 1 , Alfons Nichtl 2 , and Konrad
Kürzinger 2 — 1 Photonics and Optoelectronics Group, Physics
Department and Center for NanoScience, Ludwig-Maximilians-
Universität, Amalienstr. 54, 80799 Munich — 2 Roche Diagnostics
GmbH, Nonnenwald 2, 82372 Penzberg
We present a novel biosensor for the optical detection of molecular
binding events based on scattering spectroscopy of single functionalized
gold nanoparticles.
The scattering spectrum of a gold metal nanoparticle shows a distinct
resonance in the visible due to a collective oscillation of its conduction
band electrons. The spectral position of this nanoparticle plasmon resonance
(NPPR) depends sensitively on the dielectric properties of the
particle’s immediate surrounding. Molecular binding events inside this
nanoenvironment alter the refractive index and can therefore be deduced
from a shifted plasmon resonance position.
We monitor the homogenous NPPR spectrum of a single gold nanoparticle
which allows us to detect spectral shifts of only a few meV. There-
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fore, less than 200 molecules with a molecular weight of only 50 000 D can
be detected under physiological conditions. We demonstrate this concept
using gold nanoparticles functionalized with biotin to detect streptavidin
molecules [1].
[1] G. Raschke et al., Nano Letters, 3, 935 (2003).
Q 43.2 Do 16:45 HS 224
Mikrobewegungsanalyse an lebenden Zellen und Kleinstlebewesen
mit photorefraktiven Neuigkeitsfiltern — •Vishnu Vardhan
Krishnamachari, Oliver Grothe, Hendrik Deitmar und Cornelia
Denz — Institut für Angewandte Physik, Westfälische Wilhelms
Universität Münster, D-48149 Münster
Im Rahmen der Biophotonik müssen Methoden entwickelt werden, mit
denen Zellfunktionen in vivo kontinuierlich beobachtet werden können.
Hier stellen wir ein Mikroskop mit einem photorefraktiven Neuigkeitsfilter
vor. Es basiert auf Strahlkopplung in photorefraktiven Kristallen
und reagiert auf Intensitäts- und Phasenänderungen. Es können sowohl
die Bewegung als auch die Veränderung kleinster Objekte kontinuierlich
beobachtet werden. Im Vergleich zu anderen Methoden der Bewegungsdetektion
ist keine weitere Präparation der Objekte notwendig und es
reichen sehr geringe Lichtintensitäten. Im Falle teilweise transparenter