  We demonstrate theoretically that few-cycle vortex beam with subterawatt peak
power can be generated by self-compression of mid-infrared femtosecond vortex
beam using the thin-plate scheme. The 3 {\mu}m femtosecond vortex beam with
input duration of 90 fs is compressed to 15.1 fs with the vortex
characteristics preserved. The conversion efficiency is as high as 91.5% and
the peak power reaches 0.18 TW. The generation of the high-peak-power few-cycle
vortex beam is owing to the proper spatiotemporal match by this novel scheme,
where the spectrum is broadened enough, the negative group velocity dispersion
can compensate the positive chirp induced by nonlinear effects, and multiple
filamentation is inhibited for the keeping of the vortex characteristics. Our
work will help to generate isolated attosecond vortices, opening a new
perspective in ultrafast science.
