Physical Model of Modulation Dependent Effects in CPT Clocks

We report on the semi-analytic evaluation of the three level atom in multiple light fields subject to a slow phase modulation. Combining these results with a model of the corresponding phase sensitive detection leads to a demodulated line shape that quantitatively accounts for the shifts and dependencies that have been observed in systematic studies of Coherent Population Trapping (CPT) resonances.\footnote{to appear in JOSAB, Feb. 2005} Understanding these effects in detail is likely to be of utility in the optimization of miniature atomic time standards based on optical coherences.