  Infrared femtosecond laser pulses are important tools both in strong-field
physics, driving X-ray high-harmonic generation, and as the basis for widely
tuneable, if inefficient, ultrafast sources in the visible and ultraviolet.
Although anomalous material dispersion simplifies compression to few-cycle
pulses, attosecond pulses in the infrared have remained out of reach. We
demonstrate soliton self-compression of 1800 nm laser pulses in hollow
capillary fibers to sub-cycle envelope duration (2 fs) with 27 GW peak power,
corresponding to attosecond field transients. In the same system, we generate
wavelength-tuneable few-femtosecond pulses from the ultraviolet (300 nm) to the
infrared (740 nm) with energy up to 25 $\mu$J and efficiency up to 12 %, and
experimentally characterize the generation dynamics in the time-frequency
domain. A compact second stage generates multi-$\mu$J pulses from 210 nm to 700
nm using less than 200 $\mu$J of input energy. Our results significantly expand
the toolkit available to ultrafast science.
