A microwave frequency reference based on VCSEL-driven dark line resonances in Cs vapor

Dark line resonances, narrowed with a buffer gas to less than 100 Hz width, are observed in a Cs vapor cell using a directly modulated vertical-cavity surface-emitting laser (VCSEL). An external oscillator locked to one of these resonances exhibits a short-term stability of /spl sigma//sub y/(/spl tau/)=9.3/spl times/10/sup -12///spl radic//spl tau/, which drops to 1.6/spl times/10/sup -12/ at 100 s. A physics package for a frequency-reference based on this design could be compact, low-power, and simple to implement.