Optical atomic clock chip is as small as a coffee bean

A miniature type of atomic clock called an optical clock uses light tuned to rubidium atoms, and beats trillions of times per second. Dividing time into short intervals allows this atomic timepiece to keep time much more reliably than other clocks.

Optical atomic clock chip is as small as a coffee beanA new generation of small-scale optical clocks could better coordinate the flow of data through telecommunication networks, or sync up far-flung telescopes to make astronomical observations.

The “pendulum” inside the new optical clock is a laser tuned to about 385.285 terahertz that is, its light undulates 385.285 trillion times per second.

To ensure that the laser’s oscillations don’t fall out of rhythm, half of the beam feeds into the tiny chamber of rubidium atoms, which absorb light at precisely this frequency.

Monitoring whether the rubidium atoms are absorbing light tells the laser whether it needs to dial its frequency slightly up or down to keep time more precisely.

So the optical clock uses two components called frequency combs, also mounted on tiny chips, to translate the laser’s rapid-fire beats into slower, countable ticks. This works similar to the way a set of gears can translate the rapid spin of a small disk into the slower rotation of a larger disk.

Even though the new optical clock is pint-size compared with its predecessors, it isn’t a pocket watch yet. The chip-scale atom chamber and frequency combs are hooked up to supporting electronics that fill two tables.

“Eventually we’d like to get this technology to be truly handheld and battery powered,” Hummon says.

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