Sum-frequency generation of 589 nm light with near-unit efficiency
  We report on a laser source at 589 nm based on sum-frequency generation of two infrared laser at 1064 nm and 1319 nm. Output power as high as 800 mW are achieved starting from 370 mW at 1319 nm and 770 mW at 1064 nm, corresponding to converting roughly 90% of the 1319 nm photons entering the cavity. The power and frequency stability of this source are ideally suited for cooling and trapping of sodium atoms. 
Emmanuel Mimoun, Luigi De Sarlo, Jean-Jacques Zondy, Jean Dalibard,   and Fabrice Gerbier