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Updated: May 16, 2026

Femtosecond Laser Filaments for Use in Sub-Diffraction-Limited Imaging and Remote Sensing
Published on: April 25, 2019
Phase-stable sub-cycle mid-infrared conical emission from filamentation in gases
Yutaka Nomura1, Hideto Shirai, Kenta Ishii
1Laser Zentrum Hannover eV, Hollerithallee 8 30419 Hannover, Germany. c.unger@lzh.de
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.
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