Micro Rb atomic vapor cells for the chip-scale atomic clock

Nowadays, the portable atomic clocks with small size and low power consumption have attracted much attention. With the development of the coherent population trapping (CPT) and the micro-electro-mechanical systems (MEMS) technologies, it is possible to fabricate the miniature atomic clocks with power consumption less than 100mW. Researchers have already made great progress in the miniaturization of VCSELs, RF circuits, and photodiodes, which are the key technologies of the chip-scale atomic clock (CSAC). However, the fabrication of micro alkali atomic vapor cells is still to be improved. In this article, we describe the fabrication of micro Rb atomic vapor cells with inner dimensions of 3 mm length and 3 mm radius using anodic bonding and chemical reaction between BaN₆ and RbCl. The optical absorption and CPT resonances of the cells were measured slightly above the room temperature. In this condition, the consumption in the temperature control will be very low. Moreover, the long life (more than four years) of the cells makes it possible to use them in CSACs.