Lamplight Stabilization in a Rb Atomic Clock for Improved Frequency Stability

Lamplight fluctuations in the rubidium (Rb) atomic frequency standard (RAFS) are a significant contributor to the clock’s long-term frequency instability. Briefly, random lamplight-intensity variations induce fluctuations in the Rb atoms’ 0-0 hyperfine frequency via the light-shift effect. These lamplight-induced frequency variations follow a compound Poisson process, and for GPS Block-IIR drive the Rb clock’s random-walk frequency noise, a dominant contributor to the GPS- signal-in-space user-range-error. Here, we show that lamplight stabilization via rf-power control can mitigate a RAFS’s lamplight variations without any undue harm to the clock’s short-term frequency stability. Rf-power control is achieved by a simple modification to the lamp’s oscillator circuit. For global navigation satellite systems, the present results could yield improved onboard clock frequency stability. For small satellites employing RAFS the results could yield longer holdover periods between satellite updates.