Progress on a Miniature Cold-Atom Frequency Standard

Atomic clocks play a crucial role in timekeeping, communications, and navigation systems. Recent efforts enabled by heterogeneous MEMS integration have led to the commercial introduction of Chip-Scale Atomic Clocks (CSAC) 1 with a volume of 16 cm 3 , power consumption of 120 mW, and instability (Allan Deviation) of j(k = 1 sec) < 2e-10. In order to reduce the temperature sensitivity of next-generation CSACs for timing applications, the interaction of atoms with the environment must be minimized, which can be accomplished in an architecture based on trapped, laser-cooled atoms. In this paper, we present results describing the development of a miniature cold-atom apparatus for operation as a frequency standard. Our architecture is based on laser-cooling a sample of neutral atoms in a Magneto-Optical Trap (MOT) using a conical retro-reflector in a miniature vacuum chamber. Trapping the atoms in vacuum and performing microwave interrogation in the dark reduces the temperature sensitivity compared to vapor-cell CSACs. We present details of the component development associated with the laser systems, optoelectronics, and vacuum package for miniature cold-atom technology. Finally, we conclude by characterizing the optimum alkali background pressure for such a cold-atom frequency standard.