Efficient 494-mW Sum-frequency Generation of 589-nm Light by Using a Periodically Poled LiNbO3 Ridge Waveguide

Sodium atoms have long played an important role in spectroscopy and in the study of degenerate quantum gases. Since there are no appropriate solid-state lasers for generating continuous wave 589 nm light, which corresponds to the sodium doublet, dye lasers have mainly been used. These lasers have a problem as regards stability and their operation requires daily maintenance. Recently, it has been proposed to replace the dye laser with the sum-frequency generation (SFG) of two Nd:YAG lasers at 1064 and 1319 nm [1]. However, a doubly resonant enhancement cavity with a complex feedback locking system had to be used in order to obtain a good conversion efficiency. In this report, by using a periodically poled LiNbO
3
(PPLN) ridge waveguide [2] for the SFG, a high conversion efficiency to 589 nm light is obtained solely with a simple single pass wavelength conversion process without using an enhancement cavity.