The new microcomb clock uses a laser to excite the Caltech disk to generate a frequency comb, broadens the spectrum using nonlinear fiber, and stabilizes two comb teeth (individual frequencies) to energy transitions in rubidium atoms that "tick" at optical frequencies. (Conventional rubidium atomic clocks operate at much lower microwave frequencies.) The comb converts these optical frequency ticks to the microwave domain.
Thanks to the gear-like properties of the disk and the comb, the output is also 100 times more stable than the intrinsic ticking of the rubidium atoms. According to Diddams. "A simple analogy is that of a mechanical clock: The rubidium atoms provide stable oscillationsa pendulumand the microcomb is like a set of gears that synthesizes optical and microwave frequencies."
The center of the comb spectrum is locked to an infrared laser operating at 1560 nanometers, a wavelength used in telecommunications.
NIST researchers have not yet systematically analyzed the microcomb clock's precision. The prototype uses a tabletop-sized rubidium reference. The scientists expect to reduce the instrument size by switching to a miniature container of atoms like that used in NIST's original chip-scale atomic clock.*** Scientists also hope to find a more stable atomic reference.
The microcomb chip was made by use of conventional semiconductor fabrication techniques and, therefore, could be mass produced and integrated with other chip-scale components such as lasers and atomic references. NIST researchers expect that, with further research, the microcomb clock architecture can achieve substantially better performance in the future.
|Contact: Laura Ost|
National Institute of Standards and Technology (NIST)