More than 20 W fiber-based continuous-wave single frequency laser at 780 nm.

We demonstrate a 21.2 W continuous-wave single frequency 780 nm laser by utilizing single-pass frequency doubling of a 49.8 W 1560 nm fiber amplifier in a periodically-poled magnesium-oxide-doped lithium niobate (MgO: PPLN) crystal. The conversion efficiency of the frequency doubling reaches up to 42.6%. The high power 1560 nm Erbium-doped fiber amplifier (EDFA) is in-band pumped by a 1480 nm Raman fiber laser. Maximum output power of 49.8 W is obtained at an incident 1480 nm laser of 60.6 W, corresponding to an amplification efficiency of 79.7%. To the best of our knowledge, this is the highest reported continuous-wave single frequency 780 nm laser, which is developed for advanced quantum technology with Rb cold atoms.