Chip-scale clock

When it comes to the ultraprecise measurement of time and frequency, nothing tops an atomic clock. Imagine the applications, both commercial
and military, if very small, low-power versions of these ultimate timepieces could be made. Researchers at the National Institute of Standards and Technology's (NIST) Boulder, CO, site have laid the groundwork for such devices.

The NIST team reported on their findings in a recent issue of Applied Physics Letters. They have created a working prototype that is about the size of a grain of rice, or approximately 100 times smaller than any other atomic clock. This "physics package" can be fabricated on wafers using MEMS techniques and can then be integrated with control circuits and an external oscillator into a cubic-centimeter-sized device. The finished chip-scale clocks will potentially provide a thousandfold improvement in long-term timing precision compared with existing components, gaining or losing no more than a second every 300 years.

"The real power of our techniques is that we're able to run the clock on so little electrical power [less than 75 mW dissipation] that it could be battery operated," explains John Kitching, the project's principal investigator. "It's small enough to be easily incorporated into a cell phone or some other kind of handheld device. Nothing else like it even comes close as far as being mass producible."