Fabrication Technologies of Miniaturized Alkali Vapor Cells for Atomic Sensors

Alkali atomic vapor cells are the key components of all kinds of atomic sensors, including atomic clocks, atomic gyroscopes, atomic magnetometers, Rydberg atom sensors, etc. With the miniaturization and integration trends of these atomic sensing devices, compact alkali vapor cells, particularly micromanufactured vapor cells with high performance, are urgently needed. The development history from glass vapor cells to MEMS vapor cells is reviewed. The bonding methods for macro-fabricated alkali atomic vapor cells, such as anodic bonding, metal film thermocompression bonding, glass–frit bonding, epoxy glue bonding and laser bonding, are analyzed and summarized. The alkali metal filling techniques for vapor cells are also discussed, including the physical methods of direct filling and wax package filling, and chemical methods of the reaction of alkali chloride with BaN6, ultraviolet (UV) light decomposition of RbN6 and CsN6, electrolysis of alkali-rich glass, and laser decomposition of alkali dispensers. Compared to traditional vapor cell dimensions, vapor cells with long laser paths are emphasized, and the corresponding design and realization processes are discussed. Finally, the vapor cells with inner anti-relaxation coatings and passivation coatings aimed at achieving long reaction times and long lifetimes are analyzed.