By optical injection of an 852-nm extended-cavity diode laser (master laser) to lock the + 1-order sideband of a ~9-GHz-current-modulated diode laser (slave laser), we generate a pair of phase-locked lasers with a frequency difference up to ~9-GHz for a cesium (Cs) magneto-optical trap (MOT) with convenient tuning capability. For a cesium MOT, the master laser acts as repumping laser, locked to the Cs 6S₁/₂ (F = 3) - 6P₃/₂ (F' = 4) transition. When the + 1-order sideband of the 8.9536-GHz-current-modulated slave laser is optically injection-locked, the carrier operates on the Cs 6S₁/₂ (F = 4) - 6P₃/₂ (F' = 5) cooling cycle transition with -12 MHz detuning and acts as cooling/trapping laser. When carrying a 9.1926-GHz modulation signal, this phase-locked laser system can be applied in the fields of coherent population trapping and coherent manipulation of Cs atomic ground states.
A simultaneous observation of the optical-clock ${}^{2}{S}_{1/2}{\ensuremath{-}}^{2}{D}_{5/2}$ transition at 674 nm, in two separately trapped single
88Sr+ ions, is reported. Two nominally identical miniature rf Paul traps were used together with a 674-nm sideband-injection-locked extended-cavity diode laser. This ``slave'' laser was optically phase locked about 650 MHz away from a ``master'' diode laser, which was itself locked to a high-finesse, ultra-low-expansion (ULE) cavity. The ULE cavity was temperature-stabilized and suspended in an evacuated enclosure, and provided an ``optical flywheel'' reference standard with a relative drift rate of better than 1 part in
1011 per hour. The difference between center frequencies of the single
88Sr+-ion 674-nm (445-THz) transition multiplet in two traps was 120(90) Hz (one standard uncertainty). Thus the two trap center frequencies agree to 3 parts in
1013.