and

An experiment has been conducted to investigate the effect of laser line-narrowing on the performance of an optically pumped cesium beam frequency standard. A two laser scheme (4-+4'u for optical pumping and 4+5'7t. for detection) was used and the lasers were either frequency locked to Cs saturated absorption features in an external cell or line-narrowed by optical feedback from an external Fabry'Perot cavity [ l]. Relative to the frequency stabilization to the saturated absorption the line-narrowing on the detection laser produced a large improvement (+14dB) in the signal-to-noise ratio (S/N). However, line-narrowing on both pump and detector lasers was necessary to achieve beam shot noise limited performance. The S/N and line Q achieved in these experiments should result in a clock stability of uy (~)=3-5~10-' ~ T- ' / ' [ 2 1