Optimization of a Prototype Atomic Clock Based on Coherent Population Trapping

We developed and constructed a VCSEL-based laser system to study various configurations of coherent population trapping resonances (CPT) in hot Rb vapor, relevant for miniature CPT-based atomic clocks. We also locked an external crystal oscillator to CPT resonance; best observed fractional stability is $6\cdot10^{-12}$ at 400s. In addition to its research value, our apparatus can be easily adopted as a advance undergraduate experiment, since it uses primarily off-the-shelf electronic and optical components.