A high-stability semiconductor laser system for a ~(88)Sr-based optical lattice clock

摘要

We describe a frequency-stabilized diode laser at 698 nm used for high-resolution spectroscopy of the ~1S_0 ~3P_0 strontium clock transition. For the laser stabilization we use state-of-the-art symmetrically suspended optical cavities optimized for very low thermal noise at room temperature. Two-stage frequency stabilization to high-finesse optical cavities results in measured laser frequency noise about a factor of three above the cavity thermal noise between 2 Hz and 11 Hz. With this system, we demonstrate high-resolution remote spectroscopy on the ~(88)Sr clock transition by transferring the laser output over a phase noisecompensated 200-m-long fiber link between two separated laboratories. Our dedicated fiber link ensures a transfer of the optical carrier with frequency stability of 7×10~(18) after 100 s integration time, which could enable the observation of the strontium clock transition with an atomic Q of 10~(14). Furthermore, with an eye toward the development of transportable optical clocks, we investigate how the complete laser system (laser + optics + cavity) can be influenced by environmental disturbances in terms of both short- and long-term frequency stability.