  We have developed a modified Michelson interferometer type Raman laser system
to manipulate cold 87 Rb atoms to interfere. A frequency modulated continuous
wave technique was introduced to determine the optical path difference, thus
compensating it to zero to minimize the effects of common mode noise. The
linewidth (full width at half maximum) of the beat signal at 6.834 GHz was
measured to 1Hz limited by the resolution bandwidth of the spectral analyzer.
The measured rms phase variance of the phase noise at 166 MHz was 0.015 rad2,
mainly restricted by our poor performance radio frequency microwave source.
With modest improvements, we plan to apply this laser system to form an atom
interferometer for acceleration and rotation measurements.
