Fourier-Limited Few-Cycle Attosecond Pulses from High-Order Harmonic Generation Assisted by an Ultraintense Ultrafast Magnetic Field

Abstract

Attosecond (as) pulse generation is temporally constrained by the attochirp inherent to the high-order harmonic generation (HHG) process. In the extreme ultraviolet, near Fourier-limited as-pulses are obtained compensating the attochirp using dispersive materials like metallic filters. The shortest as-pulse record used a Zr-filter to compress the pulse down to just 43 as [1]. However, at the soft x-rays regime, chirp compensation optics is inefficient and the generation of near Fourier-limited pulses has become a great challenge. We identify a promising scenario to suppress the attochirp assisting HHG with a strong fast oscillating magnetic field (B-field), up to tens of kT, than can be obtained from structured beams or stationary configurations of state-of-the-art Petawatt laser systems. [2].