Operating Atomic Fountain Clock Using Robust DBR Laser: Short-Term Stability Analysis

We report on a robust distributed Bragg reflector (DBR) laser system for an atomic fountain clock. To confirm the performance of a DBR laser, the short-term stability of an atomic fountain clock, KRISS-F1, is measured with both DBR laser and an extended-cavity diode laser (ECDL) as a master laser in the fountain laser system. The short-term stability of the fountain clock due to the laser noise is determined to be $\sigma _{y} (\tau = T_{c}) = 1.4 \times 10^{-14}$ when either the ECDL or the DBR laser is used as a master laser. The total stability of the fountain clock with the DBR laser is limited to $3.5 \times 10^{-14}$ at 1 s of averaging time and at the highest atom number in the experiment, which is limited by quantum projection noise. No additional degradation in fountain performance is observed when an ECDL is replaced by the DBR laser. From these results, we conclude that our fountain clock is made much more robust by adopting a DBR laser, which is immune to acoustic and vibrational shocks as well as environmental temperature variations.