Reflection-type vapor cell for micro atomic clocks using local anodic bonding of 45° mirrors

Area of Science:

• Atomic, Molecular, and Optical Physics
• Microfabrication and MEMS
• Metrology and Timekeeping

Background:

• Chip-scale atomic clocks require miniaturized and stable vapor cells.
• Conventional vertically stacked cells present fabrication and integration challenges.
• Reflection-type designs offer potential for improved performance and manufacturability.

Purpose of the Study:

• To design, fabricate, and evaluate reflection-type planar vapor cells for chip-scale atomic clocks.
• To assess the performance of these cells using coherent population trapping resonance.
• To compare the stability of planar cells with conventional vertically stacked designs.

Main Methods:

• Fabrication of planar vapor cells with integrated Bragg reflector mirrors using anodic bonding.
• Cavity lengths varied from 2 mm to 8 mm.
• Observation of coherent population trapping resonance in Rubidium (Rb) atoms.
• Measurement of Allan deviations to quantify clock stability.

Main Results:

• Successful fabrication and operation of reflection-type planar vapor cells.
• Coherent population trapping resonance achieved, demonstrating atomic clock functionality.
• Excellent Allan deviations recorded: ${2.2} \times {{1}}{{{0}}^{- 10}}$ (2 mm cell) and ${9.5} \times {{1}}{{{0}}^{- 11}}$ (6 mm cell) at 1 s averaging time.
• Planar cell stability is comparable to conventional vertically stacked cells.

Conclusions:

• Reflection-type planar vapor cells are feasible for chip-scale atomic clocks.
• These cells are compatible with system-in-package integration.
• The developed cells maintain high clock stabilities without performance degradation.