We describe a compact and versatile multi-frequency laser system for laser-cooling potassium atoms by frequency doubling a fiber-optic telecom beam (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 a high-power amplifier. A final free-space second-harmonic generation stage provides a single beam with typically 2.5 W at quasi-resonant frequencies (767 or 770 nm) with high-quality mode and ready for laser cooling. This allowed us to trap up to 4×10941K atoms with fast loading times (2.5 s) at sub-Doppler temperatures of 16 μK. This opens promising perspectives toward versatile and transportable ultracold atom setups.

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