title: Phase-stable sub-cycle mid-infrared conical emission from filamentation in gases.
abstract: Sub-single-cycle pulses in the mid-infrared (MIR) region were generated through a conical emission from a laser-induced filament. Fundamental and second-harmonic pulses of 25-fs Ti:sapphire amplifier output were focused into argon to produce phase-stable broadband MIR pulses in a well-focusable ring-shaped beam. The beam profile and spectrum of the MIR field are accurately reproduced with a simple calculation based on a four-wave mixing process. The ring-shaped pattern of the MIR beam originates from a dramatic confocal-parameter mismatch between the MIR field and the laser beams.
authors.affiliation: Laser Zentrum Hannover eV, Hollerithallee 8 30419 Hannover, Germany. c.unger@lzh.de
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Nomura
authors.forename: Hideto
authors.initials: H
authors.lastname: Shirai
authors.forename: Kenta
authors.initials: K
authors.lastname: Ishii
authors.forename: Noriaki
authors.initials: N
authors.lastname: Tsurumachi
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Voronin
authors.forename: Aleksei M
authors.initials: AM
authors.lastname: Zheltikov
authors.forename: Takao
authors.initials: T
authors.lastname: Fuji