Faraday laser using 1.2 km fiber as an extended cavity

Abstract

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 of the natural 87Rb 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 in the FADOF is 20.5% with an ultra-narrow bandwidth of 29.1 MHz. The Allan deviation of the Faraday laser is around in 0.06 to 1 s sampling time. Laser frequency is always kept in the center of the transmitted peak assigned to . 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.