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Communications of the ACM

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Future Electronics May Depend on Lasers, Not Quartz


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Vahala's new laser frequency reference (left) is a 6mm disk; the quartz "tuning fork" (center) is the frequency reference commonly used in watches. The dime at right is for scale.

A new method of stabilizing microwave signals in the gigahertz range uses a pair of laser beams as the reference, rather than quartz.

Credit: Jiang Li/Caltech

California Institute of Technology (Caltech) researchers have developed a method to stabilize microwave signals in the gigahertz range using a pair of laser beams as the reference instead of a crystal.

The new technique, called electro-optical frequency division, is based on the method of optical frequency division. "Our new method reverses the architecture used in standard crystal-stabilized microwave oscillators--the 'quartz' reference is replaced by optical signals much higher in frequency than the microwave signal to be stabilized," says Caltech professor Kerry Vahala.

Caltech's Jiang Li says the new method can be compared to a gear chain on a bicycle that translates pedaling motion from a small, fast-moving gear into the motion of a much larger wheel. "Electrical frequency dividers used widely in electronics can work at frequencies no higher than 50 to 100 GHz," he points out. "Our new architecture is a hybrid electro-optical 'gear chain' that stabilizes a common microwave electrical oscillator with optical references at much higher frequencies in the range of terahertz or trillions of cycles per second."

The laser measures just 6 mm in diameter, which makes it especially useful in compact photonics devices, according to project leader Scott Diddams at the U.S. National Institute of Standards and Technology.

From California Institute of Technology
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