We have devised an all-optical setup for the generation of two phase-locked
laser fields with a frequency difference of 3 GHz using only standard opti
cs and two acousto-optical frequency shifters, that are operated at 253 MHz
in sixtupel pass. The spectral width of the beat frequency is measured to
be 300 Hz (full width at half maximum) limited by the resolution bandwidth
of the spectrum analyzer. We routinely obtain an overall efficiency of more
than 15% and demonstrate that the frequency shifted light can be further a
mplified by injecting it into additional "slave" lasers. This setup provide
s a low-cost alternative over conventional methods to generate laser fields
with difference frequencies in the GHz domain, as for example, used in las
er spectroscopy, laser cooling and trapping, and coherent manipulation of a
tomic quantum states. (C) 2000 American Institute of Physics. [S0034-6748(0
0)03109-9].