  Efficient supercontinuum (SC) generation featuring high spectral intensity
across a large bandwidth requires high peak powers of several megawatt from
pulsed lasers. Under these conditions and at multi-kilohertz (kHz) repetition
rates, the SC generated in most materials is unstable due to thermal effects.
In this work, we leverage the superior dispersion properties of water to
maximize the spectral width of the SC, while avoiding stability issues due to
thermal loading by means of a constant laminar flow of the liquid. This flow is
controlled by a differential pressure scheme that allows to precisely adjust
the fluid velocity to an optimum value for maximum stability of the SC. This
approach is successfully implemented for repetition rates of 50 kHz and 100 kHz
and two different pump wavelengths in the visible (VIS) and near infrared (NIR)
spectral region with stability of the SC signal only limited by the driving
pulses. The resulting water SC spans more than one octave covering the VIS to
NIR range. Compared to established materials, such as yttrium aluminum garnet
(YAG) and sapphire, the spectral bandwidth is increased by 60 % and 40 %
respectively. Our scheme has the potential to be implemented with other liquids
such as bromine or carbon disulfide (CS2), which promise even wider broadening
and operation up to the mid-infrared.
