Diode laser frequency stabilization for a Ca optical clock

Frequency stabilization of extended-cavity diode lasers at 657 nm to the Hz-level is reported. Using the Pound-Drever-Hall technique the lasers are locked to high-finesse Fabry-Perot cavities made of ULE (ultra low expansion glass). The cavities are isolated against vibrations passively with a one stage spring suspension inside an acoustic damping box resting on the optical table. Thus cavity accelerations on the μg-level and below are achieved. The temperature of the reference cavities is stabilized by the use of active and passive temperature stabilization.