Reduction of laser phase-noise to amplitude-noise conversion in the gas-cell atomic clock

In the laser-pumped gas-cell atomic clock, the short-term stability is significantly influenced by laser phase-noise (PM) to amplitude-noise (AM) conversion. Here, we discuss the influence of pressure-broadening on the conversion process, and find that when collisional dephasing is very rapid there is a significant decrease in the efficiency of PM-to-AM conversion. Normally, since pressure-broadening increases the linewidth of an atomic transition, collisional dephasing decreases spectroscopic sensitivity. However, the present results imply that when laser PM-to-AM conversion is dominant, pressure broadening can actually increase spectroscopic sensitivity. Thus, under conditions of significant PM-to-AM conversion, pressure-broadening should improve the performance of laser-pumped atomic clocks.