Rubidium chip-scale atomic clock with improved long-term stability through light intensity optimization and compensation for laser frequency detuning

We demonstrate the implementation of a Rb-87 chip-scale atomic clock (CSAC) that has improved long-term stability. A simple method of reducing the frequency drift in the CSAC is proposed. As well as the well-known effect of light intensity on the clock frequency, our analysis shows that the frequency drift that is due to laser frequency detuning (LFD) variation originates from asymmetry in the coherent laser fields, and thus, we propose to actively compensate the clock frequency by using variations in the light intensity and LFD. We performed experiments to obtain precise clock frequency sensitivities to the light intensity and LFD, and the frequency drift was reduced from 7.1 x 10(-11)/day to 6.9 x 10(-13)/day with the frequency compensation method. Additionally, the CSAC with an optimized configuration of light intensity and microwave power showed evident long-term frequency stability improvement, from 8.9 x 10(-11) to 8.7 x 10(-12) at 10(5) s. Therefore, our method is useful in reducing the frequency drift of CSACs and could be potentially used in applications that require moderate long-term stability of sub-1 x 10(-11). (C) 2016 Optical Society of America