2024/08/14 by Dang, Hongliang, Gao, Jiaxin, Wu, Hao +2
#FOS: Physical sciences #Optics (physics.optics)
paper · doi:10.48550/arxiv.2408.07306
Sub-cycle optical pulse is of great importance for ultrafast science and technology. While a narrower pulse can offer a higher temporal resolution, so far the pulse width has not reached the limit of half an optical cycle. Here we propose to break the half-cycle limit via inverse Compton scattering in a deep-subwavelength-confined infrared or THz optical driving field, which can be converted into a deep-sub-cycle (i.e., less than half a cycle) ultrafast pulse by relativistic electrons passing through. Quantitatively, by using a deep-subwavelength-confined 0.4-THz 1-ps pulsed driving field and a 3-MeV 1-fs electron bunch, we obtain a ∼ 0.1-cycle femtosecond pulse with a peak frequency of ∼ 26 THz (∼ 38 fs in optical cycle) and a pulse width of ∼ 3.6 fs; with the same driving field and a 30-MeV 50-as electron bunch, we obtain a 0.17-cycle attosecond pulse with a peak frequency of ∼ 2.0 PHz (∼ 500 as in optical cycle) and a pulse width of ∼ 86 as. Below the optical damage threshold of the field-confinement material, the single-pulse photon number can exceed 106. Such pulses may open opportunities for studying light-matter interaction on the deep-sub-cycle level, and pave a way to unprecedented optical technology ranging from temporal super-resolution optical microscopy and spectroscopy to unconventional atom/molecule polarization and manipulation.