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The Chip-Scale Atomic Clock

Robert Lutwak, Symmetricom

(Session : Thursday from )

Abstract. The Chip-Scale Atomic Clock (CSAC) represents the prototypical integrated atomic system (IAS). While the atomic physics of CSAC is relatively simple, many of the engineering challenges are common to all emerging IAS technology. In particular, the development of the thermal and mechanical design of the physics package, low-power narrowband laser sources, and low-power microwave synthesis and control systems are likely to present similar and comparable challenges for other miniature low-power atomic systems. Our research collaborative, comprised of the clock development group at the Symmetricom Technology Realization Center, the microelectromechanical systems (MEMS) group at the Charles Stark Draper Laboratory, and the optoelectronics group at Sandia National Laboratories, has been developing CSAC technology since 2002. The 1 cm3 CSAC physics package consists of a vertical cavity surface emitting laser (VCSEL), an alkali metal vapor resonance cell, and a silicon photodiode, which are all temperature stabilized at 85°C, with a power consumption of less than 10 mW. The entire CSAC, including the physics package, microwave synthesizer, and control electronics, consumes <130 mW over an operating temperature range of -10°C to +70°C. In 2007, we completed a prototype build of 10 nearly identical CSACs in order to evaluate consistency of build and unit-to-unit variation. The results were quite promising. All of the units perform similarly, with Allan deviation stability of sy(ô) < 3x10-10ô-1/2. Following our initial characterization of these devices, several were sent to government laboratories for independent evaluation and others have been loaned to systems’ integrators where they have demonstrated new capabilities in communications, navigation, and remote monitoring applications. In this talk, I will describe the architecture of the CSAC, with particular emphasis on those elements of the design which permit low-power and reliable operation over a wide range of real-world environmental conditions. I will review the data from the pre-production build and present recent results on efforts to continue improving performance while reducing overall size and power consumption.