  Deep ultraviolet (DUV) laser pulses with tuneable wavelength and very short
duration are a key enabling technology for next-generation technology and
ultrafast science. Their generation has been the subject of extensive
experimental effort, but no technique demonstrated thus far has been able to
meet all requirements in one light source. Here we demonstrate a bright,
efficient, and compact source of tuneable deep ultraviolet ultrafast laser
pulses based on resonant dispersive wave emission in hollow capillary fibre. In
a total footprint of only 120 x 75 cm, including the ytterbium-based drive
laser, we generate pulses between 208 nm and 363 nm at 50 kHz repetition rate
with a total efficiency of up to 3.6%. Down-scaling of the DUV generation
reduces the required energy sufficiently to enable the generation of two-colour
few-femtosecond DUV pulses.
