18W ultra-narrow diode laser absolutely locked to the Rb D₂ line

We described a wavelength locked and spectral narrowed high-power diode laser with a Faraday anomalous dispersion optical filter (FADOF). By an external cavity with a ⁸⁵Rb FADOF, the central wavelength of the diode laser was precisely locked to the Rb resonance D₂ line. The bandwidth was narrowed from the free-running 4 nm to 0.002 nm (1.2 GHz, FWHM). At 4.9 A maximal driven current, the laser produced a continuous wave (CW) output of 18 W with an external cavity efficiency of 80%, either the current or the temperature had no impact on the central wavelength of the diode laser. The Rb cell works well without any damage under a long-time running. This ultra-stable and extreme-narrowed high power diode laser would find many applications in alkali lasers pumping, metastable rare gas laser pumping, spin-exchange optical pumping, and quantum optics.