Vacuum packaged microfabricated rubidium vapor cells

There is an interest to develop miniature tactical-grade clock to overcome GPS timing vulnerability for a wide range of DOD missions. Chip-scale atomic clocks do not meet tactical grade requirements and require 2 to 3 orders of magnitude improvement on their frequency sensitivity to thermal perturbations. One approach consists in replacing the atomic vapor (Rb, Cs, Ca, Sr, Yb) with molecular vapor (I2, COS, C2H2, CO) because molecules do not condensate at temperatures beyond 130˚C. With that in mind, miniature clocks with lower frequency drift rates require the development of heaters and thermal probes that do not generate residual magnetic fields at that target operating temperature.   In this Phase I effort, EngeniusMicro will transfer the technology developed by John Kitching’s group at NIST. The technology consists of an atomic vapor cell fabricated by a 2-step anodic process which removes the Rb pill from the final cell, allowing for a more stable chemical environment and a much smaller footprint. The atomic vapor cell is sandwiched by Kapton tethers which mechanically support and thermally isolate the cell from the environment. The complete physics package is 1cm by 1cm and the cell is electrically connected via planar electrical feedthroughs.  Several aspects of this technology will be improved upon including the design of the heaters and the choice of materials to enable RTDs with sub-1mK temperature sensitivity. If the prototyping effort is successful in Phases I & II, we will transfer the fabrication process flow to Dynetics Leidos for mid-volume fabrication in a single-user facility that can handle TS level security clearance.