Accurate navigation requires precision timing synchronization to about 1 billionth of a second per day. New applications require timing mechanisms that can operate without satellites and in harsh environments. NIST developed a chip-scale atomic clock (CSAC) that is smaller, energy-efficient and more accurate.
NIST Impacts: Navigation through Timekeeping
The physics package of the NIST chip-scale atomic clock includes (from the bottom) a laser, a lens, an optical attenuator to reduce the laser power, a waveplate that changes the polarization of the light, a cell containing a vapor of cesium atoms, and (on top) a photodiode to detect the laser light transmitted through the cell.
Credit: NIST
NIST created a new atomic clock the size of a computer chip, eliminating the need for large microwave cavities, and adapted standard microfabrication techniques to develop an economically viable device. Building on NIST prototypes, commercialized chip-scale atomic clocks now offered by Microsemi are about a thousand times smaller than previous products, while providing the stability necessary for GPS receivers, unmanned vehicles, underwater sensor networks and anti-IED jamming systems.
The atomic clocks used for navigation as well as telecommunications networks, power grids and financial transactions rely on precision timekeeping disseminated by NIST, starting with the NIST primary standard atomic clock. Those systems, which rely on communication with satellites, are inadequate for indoor and underwater use and are subject to malicious jamming.
With a focus on manufacturability, NIST decided to build a prototype chip-scale atomic clock using commercial, off-the-shelf technology where possible, along with standard microelectro-mechanical systems fabrication and wafer-level assembly potential. NIST improved the devices to as good as 10-12 uncertainty before transferring the technology to commercial manufacturers.
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