Automatic laser control for a88Sr+optical frequency standard

Optical frequency standards, based on the 674 nm 2 S 1/2 – 2 D 5/2 transition in a single cold trapped 88 Sr + ion, are being characterized at the UK National Physical Laboratory. Routine operation is required for measurement campaigns over several days and there is also a long-term requirement for unattended operation in remote environments, such as on a satellite or at a spacecraft tracking ground station. Software algorithms have been developed which enable the automatic relocking of multiple extended cavity diode lasers to optical cavities following out-of-lock errors. Additional algorithms are used to monitor and control auxiliary distributed feedback diode lasers by means of a wavemeter. Using this control system, unattended operation for more than 60 h has been demonstrated. Preliminary results are presented giving a single-trap relative frequency stability of 2.5 × 10 −16 at τ = 4000 s. This capability paves the way for a reliable Sr + ion-trap-based optical standard capable of operating remotely for extended periods.