Few-Cycle Laser Pulses: The Carrier-Envelope Phase, Its Role in the THz Emission from Laser-Generated Plasmas and a New Way to Measure It
M. Kress a, T. Löffler a, M.D. Thomson a, H.G. Roskos a, R. Dörner b, H. Gimpel c, K. Zrost c, T. Ergler c, R. Moshammer c, U. Morgner c and J. Ullrich c
a Physikalisches Institut, Johann Wolfgang Goethe-Universität, Max-von-Laue-Str. 1, D-60438 Frankfurt (M), Germany
b Institut fűr Kernphysik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Str. 1, D-60438 Frankfurt (M), Germany
c Max-Planck-Institut fűr Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany
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Received: 26 08 2007;
Terahertz emission from laser-generated air plasmas has recently been identified as an interesting source for THz radiation. High intensities and a large bandwidth of the THz pulses can be achieved. We briefly review several mechanisms which were employed to generate the quasi-static dipole moment needed for the optical rectification process. This leads us to a discussion of a specific application of THz emission from an air plasma, namely the investigation of the carrier-envelope phase of few-cycle optical pulses. Such pulses of a duration of less than 10 fs induce a spatial charge asymmetry in the plasma directly via non-linear tunneling ionization. The asymmetry, and with it the emission of the THz radiation from the plasma, depend on the carrier-envelope phase, with the consequence that one can determine the phase by measurement of the amplitude and polarity of the THz pulse.
DOI: 10.12693/APhysPolA.113.769
PACS numbers: 42.65.Re, 72.30.+q, 78.47.-p