Sub-2 fs pulses generated by self-channeling in the deep ultraviolet.

The generation of sub-2 fs light pulses in the UV is numerically demonstrated, using frequency conversion in filamentation regime. Few-cycle pulses emitted at 266 nm keep their temporal shape over several tens of centimeters. Self-compression results from the interplay between Kerr self-focusing and a low-density plasma, which continuously defocuses the pulse over extended propagation ranges.