Second-Harmonic Generation for Narrow-Line Cooling of 7Li

Abstract

Laser cooling of lithium atoms is usually performed on the 2S1/2 to 2P3/2 transition at 671 nm. The Doppler temperature of this transition, which is the limit temperature of laser cooling, is 140 µK. The 2S1/2 to 3P3/2 transition at 323 nm has a Doppler temperature 7 times smaller than that of the 671 nm transition. With the 323 nm transition, it is possible to reach a temperature low enough for an all-optical production of a Bose-Einstein condensate. The 323 nm light is produced by second-harmonic generation (SHG). We present our design of the laser system that generates light at 646 nm and the frequency-doubling cavity for SHG. The laser frequency is stabilized by a Fabry-Perot cavity and an Iodine transition.