Credit: F. Quinlan/NIST
The black rectangle (center) is a high-speed semiconductor photodiode that converts laser pulses to super-stable microwave frequencies. The diode is surrounded by a gold-coated border in which electrical leads are embedded. Wires connect the leads to the copper electrical circuit (top) used to extract microwave signals. The entire setup rests on a brass plate for mechanical stability.
Researchers at the National Institute of Standards and Technology (NIST) have used state-of-the-art atomic clocks, advanced light detectors, and a measurement tool called a frequency comb to boost the stability of microwave signals a hundredfold. This marks a giant step toward better electronics to enable more accurate time dissemination, improved navigation, more reliable communications and higher-resolution imaging for radar and astronomy. Improving the microwave signal’s consistency over a specific time period helps ensure reliable operation of a device or system.
The work transfers the already superb stability of the cutting-edge laboratory atomic clocks operating at optical frequencies to microwave frequencies, which are currently used to calibrate electronics. Electronic systems are unable to directly count optical signals, so the NIST technology and techniques indirectly transfer the signal stability of optical clocks to the microwave domain. The demonstration is described in the May 22, 2020, issue of Science.
In their setup, the researchers used the “ticking” of two of NIST’s ytterbium lattice clocks to generate light pulses, as well as frequency combs serving as gears to translate the higher-f ..
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