  We describe a compact and versatile multi-frequency laser system for
laser-cooling potassium atoms, by frequency doubling a fiber-optic telecom beam
($\simeq 1534$ or $1540$~nm). Low-power fiber-based telecom lasers and
components generate a single beam containing the cooling and repumper half
frequencies, subsequently amplified by high-power amplifier. A final free-space
SHG stage generates a single beam with typically 2.5 W at quasi-resonant
frequencies ($\simeq 767$ or $770$~nm) with high-quality mode and ready for
laser cooling. This allowed to trap up to $4\times10^9$ $^{41}$K atoms with
fast loading times (2.5 s) at sub-Doppler temperatures of 16~$\mu$K. This opens
promising perspectives towards versatile and transportable ultracold atom
setups.
