Characterization of Microfabricated Rubidium Vapor Cells

Atomic vapor cells, which are sealed vessels containing an alkali metal vapor addressable by lasers, are often used as frequency references in applications towards chip-scale atomic clocks and quantum sensing. Wafer-level MEMS vapor cells are of significant interest due to reductions in SWaP and fabrication techniques scalable to mass production. Photolithography on silicon wafers, patterned to include an activation cavity with a rubidium micropill dispenser, an optical cavity for measurements, and a channel connecting the two, as well as anodic bonding to borosilicate glass were performed in order to fabricate many vapor cells at once. The vapor cells were activated using a high intensity 1064 nm laser aligned with the activation cavity. Absolute and saturated absorption spectroscopy were performed in order to characterize the properties of activated vapor cells. Results demonstrate the characterization of transition linewidth broadening within various MEMS vapor cells. Sources of broadening include optical saturation effects and optical pumping, the presence of buffer gas, and temperature-dependent Doppler broadening. This work informs future efforts towards novel and scalable vapor cell fabrication techniques.