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Determination of the Carrier-Envelope Phase of Few-Cycle Laser Pulses with Terahertz-Emission Spectroscopy

Markus Kress·Torsten Loeffler·Mark D. Thomson·Reinhard Doerner·Hartmut Gimpel·Karl Zrost·Thorsten Ergler·Robert Moshammer·Uwe Morgner·Joachim Ullrich·Hartmut G. Roskos
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Abstract

The availability of few-cycle optical pulses opens a window to physical phenomena occurring on the attosecond time scale. In order to take full advantage of such pulses, it is crucial to measure and stabilise their carrier-envelope (CE) phase, i.e., the phase difference between the carrier wave and the envelope function. We introduce a novel approach to determine the CE phase by down-conversion of the laser light to the terahertz (THz) frequency range via plasma generation in ambient air, an isotropic medium where optical rectification (down-conversion) in the forward direction is only possible if the inversion symmetry is broken by electrical or optical means. We show that few-cycle pulses directly produce a spatial charge asymmetry in the plasma. The asymmetry, associated with THz emission, depends on the CE phase, which allows for a determination of the phase by measurement of the amplitude and polarity of the THz pulse.

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Markus Kress, Torsten Loeffler, Mark D. Thomson, Reinhard Doerner, Hartmut Gimpel, Karl Zrost, Thorsten Ergler, Robert Moshammer, Uwe Morgner, Joachim Ullrich, Hartmut G. Roskos. 2006-03-16. Determination of the Carrier-Envelope Phase of Few-Cycle Laser Pulses with Terahertz-Emission Spectroscopy. https://doi.org/10.1038/nphys286

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