Faraday laser using 1.2 km fiber as an extended cavity

We demonstrate a Faraday laser using a 1.2 km fiber as an extended cavity, which provides optical feedback and obtains small free spectrum range (FSR) of 83 kHz, and have succeeded in limiting the laser frequency to a crossover transition 5(2)S(1/2), F = 2 -> 5(2)P(3/2) F' = 1,3 1 2 2 3 2 of the natural Rb-87 at 780 nm. The Faraday laser is based on a Faraday anomalous dispersion optical filter (FADOF) with an ultra-narrow bandwidth and the long fiber extended cavity of 1.2 km. The peak transmission assigned to the crossover transition F= 2 -> F' = 1, 3 in the FADOF is 20.5% with an ultra-narrow bandwidth of 29.1 MHz. The Allan deviation of the Faraday laser is around 6.0 x 10(-11) in 0.06 to 1 s sampling time. Laser frequency is always kept in the center of the transmitted peak assigned to F = 2 -> F' = 1, 3. The Faraday laser realized here can provide light exactly resonant with an atomic transition used for atom-photon interaction experiments and is insensitive to diode temperature and injection current fluctuations.SCI(E)ARTICLEjbchen@pku.edu.cn134