Frequency tripled 1542 nm telecom laser diode stabilized to iodine   hyperfine line in the 10-15 range
  We report on telecom laser frequency stabilization to narrow iodine hyperfine line in the green range of the optical domain, after a frequency tripling process using two nonlinear PPLN crystals. We have generated up to 300 mW optical power in the green (P3w), from 800 mW of infrared power (Pw). This result corresponds to an optical conversion efficiency eta= P3w/Pw ~ 36 %. To our knowledge, this is the best value ever demonstrated for a CW frequency tripling process. We have used a narrow linewidth iodine hyperfine line (component a1 of the 127I2 R 35 (44-0) line) to stabilize the IR laser yielding to frequency stability of 4.8x10-14 t-1/2 with a minimum of 6x10-15 reached after 50 s of integration time. The whole optical setup is very compact and mostly optically fibered. This approach opens the way for efficient and elegant architecture development for space applications as one of several potential uses. 
Charles Philippe, Rodolphe Le Tragat, David Holleville, Michel Lours,   Tuam Minh-Pham, Jan Hrabina, Frederic Du Burck, Pete...
physics.atom-ph physics.ins-det physics.optics