A Frequency Offset Lock for High Field Imaging

The design and implementation of a tuneable frequency offset lock for the high field imaging of magnetically and optically trapped 40K or 87Rb atoms is discussed. The tuneable laser is optically mixed with a master reference locked to the species ’ atomic lines using a saturated absorption spectroscopy. Heterodyning occurs on an GaAs ROSA de-tector and the beat frequency is phase-frequency locked to a tuneable frequency source using feedback control of the piezo voltage and laser current. The lock has a 500 kHz bandwidth and a range of 6.4 GHz above and below the master reference. Optical line width measure-ments have yet to be completed for the offset lock, however, in principle the tuned line width can approach that of the master reference