Effects of Polarization Fluctuations in CPT-Based Atomic Clocks; Conference paper

摘要

In the typical CPT clock, circularly polarized light creates a superposition state between the two m(F)=0 ground state sublevels via a common m(F)= +1 (or m(F)=1) excited state. If the laser polarization suddenly changes, the common excited state will also change. This introduces a transient into the CPT signal, which can degrade the clock's signal-to-noise ratio. Here, we present preliminary results from our experiments examining this issue. In particular, we find that a change in laser polarization leads to a transient change in the CPT signal via two processes. The first appears to be associated with the re-establishment of an equilibrium electronic spin polarization in the vapor, which, in a four-level model of the CPT signal, can be thought of as a re-establishment of the trapping state population; the second process is still under investigation. Each of these processes has a unique timescale, and both will be important for understanding a CPT signal's response to laser polarization noise.