title: Terahertz white-light pulses from an air plasma photo-induced by incommensurate two-color optical fields.
abstract: We demonstrate plasma-THz generation in ambient air with two-color (ω-2ω) optical excitation using input pulses with a bandwidth supporting sub-20-fs duration, yielding a continuous bandwidth exceeding 100 THz with no significant roll-off and a pulse energy of 360 nJ at a 1-kHz repetition rate. The key aspect in achieving this performance is an optimized geometry of the second-harmonic generation (SHG) crystal, producing a 2ω-field detuned from the second-harmonic of the ω-field, which promotes both a high polarization bandwidth and optimal ω-2ω temporal overlap in the plasma, as supported by theoretical results.
authors.affiliation: Physikalisches Institut, J. W. Goethe-Universit¨at, Max-von-Laue-Str 1, 60438 Frankfurt am Main, Germany. thomson@physik.uni-frankfurt.de
authors.forename: Mark D
authors.initials: MD
authors.lastname: Thomson
authors.forename: Volker
authors.initials: V
authors.lastname: Blank
authors.forename: Hartmut G
authors.initials: HG
authors.lastname: Roskos