Fig. 1. Simplified representation of three levels of the 87Rb atoms

Fig. 2. (a) Vapor cell is made from a hollow-core Pyrex fiber with a CO2 laser; (b) vapor cell without filling tube made with a CO2 laser; (c) Cs-vapor micro-cell whose inner walls are coated with paraffin; (d) micro-glass cell on the top of silicon wafer

Fig. 3. (a) Transparent glass cell with regular geometry; (b) cylindrical glass cell

Fig. 4. (a) Vapor cell produced by micro-machining of silicon wafers and anodic bonding; (b) vapor cell with integrated multiply thin film reflectors

Fig. 5. (a) Photograph of vapor cell of Peking University; (b) CPT resonance signal measured at 47 ℃

Fig. 6. Micro-fabricated vapor cells based on photolysis of azide cesium

Fig. 7. Micro-graph of the vapor cells

Fig. 8. (a) Atomic cell of NIST in 2004; (b) vapor cells based on direct filling method

Fig. 9. Fabrication process of micro spherical rubidium vapor cell

Fig. 10. Process of electrolytic cell filling method

Fig. 11. Process outline to realize Rb vapor cells by using Rb wax micro-packets

Fig. 12. Micro-fabricated rubidium vapor cells with a thick glass core