Long-term frequency instability of atomic frequency references based on coherent population trapping and microfabricated vapor cells

Abstract

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 lasertemperature 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.

Influence of laser sources with different spectral properties on the performance of vapor cell atomic clocks based on lin‖lin CPT

“…Thus, for cPT-based atomic clocks, the detection noise can be noticeably reduced. In such a case, v mod is larger than the line width Γ of the monitored signal 3 [13], [14], which cannot be implemented in the microwave optical double resonance (dr) clock scheme as presently used. on the contrary, in reference [13], the authors showed that it is possible to realize a cPT clock using v mod ≈ 10 · Γ.…”

Rubidium pump-probe spectroscopy: Comparison betweenab initiotheory and experiment

“…There has been much interest recently in the effect of the propagation of a laser beam through dilute vapors of alkali metal atoms [1][2][3][4][5] due to their application in laser cooling [6,7], chip-scale atomic clocks and magnetometers [8,9], laser stabilization [10][11][12], and electromagnetically induced transparency [13]. In order to understand the spectra, several models have been proposed which accurately predict the Doppler-broadened and sub-Doppler absorption spectra of a dilute vapor with weak and strong probe beams [1,[14][15][16][17][18].…”

Optical system design of a portable coherent population trapping (CPT) atom clock

“…In recent years, the coherent population trapping (CPT) phenomenon [1,2] has drawn more and more attention in the time and frequency community. The possibility of using the CPT phenomenon for the implementation of atomic clocks was proposed in the last decade, and experiments are currently being carried out on several laboratories [3][4][5][6][7][8][9][10][11] . Portable atom clock with small volume has been in demand for portable equipment such as GPS and BEIDOU receivers, in-field telecommunication devices, and various kinds of measuring instruments.…”