The 2nd harmonic signal in vapor-cell clocks error-signal quality: Does S2 imply dS1/dΔ?

摘要

How does one directly assess the quality of a Rb atomic clock signal remotely and in real time? Typically, one monitors the clock's 2nd harmonic signal, S_2, which in the quasi-static approximation is a measure of the correction signal's slope, dS_1/dΔ. Unfortunately, in real vapor-cell clocks the quasi-static approximation is not valid, and the physics relating S_2 to dS_1/dΔ is complicated and not well understood. We have begun a series of studies aimed at elucidating the relationship between S_2 and dS_1/dΔ, and here we present our preliminary results.