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.