Interrogation laser for a strontium lattice clock
  We report on the setup and characterization of a 698 nm master-slave diode laser system to probe the 1S0-3P0 clock transition of strontium atoms confined in a one-dimensional optical lattice. A linewidth in the order of around 100 Hz of the laser system has been measured with respect to an ultrastable 657 nm diode laser with 1 Hz linewidth using a femtosecond fiber comb as transfer oscillator. The laser has been used to measure the magnetically induced 1S0-3P0 clock transition in 88Sr where a linewidth of 165 Hz has been observed. The transfer oscillator method provides a virtual beat signal between the two diode lasers that has been used to phase lock the 698 nm laser to the 1 Hz linewidth laser at 657 nm, transferring its stability to the 698 nm laser system. 
T. Legero, Ch. Lisdat, J. S. R. Vellore Winfred, H. Schnatz, G.   Grosche, F. Riehle and U. Sterr