CPT spectroscopy on low-temperature sealed MEMS rubidium vapour cells

In recent years there has been a strong effort to reduce the size and power consumption of vapour cell atomic clocks [1,2]. The progress in this direction is driven by several factors such as the use low power laser diodes (VCSEL), Coherent Population Trapping resonances (CPT), and micro-fabricated (MEMS) alkali-vapour cells. Here the micro-fabrication of vapour cells has proven a challenging task. All results reported on this task use anodic bonding at high-temperatures (>300°C) to seal the cell [3]. However, the low melting point and high vapour pressure of the alkali-metal combined with long bonding-times (>1hour) complicate this process. We have recently developed a low temperature (~150°C) sealing technique with fast process time (