We present an evaluation of the long-term frequency instability and environmental sensitivity of a chip-scale atomic clock based on coherent population trapping, particularly as affected by the light-source subassembly. The long-term frequency stability of this type of device can be dramatically improved by judicious choice of operating parameters of the light-source subassembly. We find that the clock frequency is influenced by the laser-injection current, the laser temperature, and the rf modulation index. The sensitivity of the clock frequency to changes in the laser-injection current or the substrate temperature can be significantly reduced through adjustment of the rf modulation index. This makes the requirements imposed on the laser-temperature stabilization, in order to achieve a given frequency stability, less severe. The clock-frequency instability due to variations in local oscillator power is shown to be reduced through the choice of an appropriate light intensity inside the cell. The importance of these parameters with regard to the long-term stability of such systems is discussed.
© 2006 Optical Society of America
Atomic and Molecular Physics
Original Manuscript: September 16, 2005
Manuscript Accepted: November 17, 2005
Vladislav Gerginov, Svenja Knappe, Vishal Shah, Peter D. D. Schwindt, Leo Hollberg, and John Kitching, "Long-term frequency instability of atomic frequency references based on coherent population trapping and microfabricated vapor cells," J. Opt. Soc. Am. B 23, 593-597 (2006)