Researchers from the National Institute of Standards and Technology (NIST) and California Institute of Technology (Caltech) have demonstrated a new design for an atomic clock that is based on a chip-scale frequency comb, or a microcomb.
The microcomb clock, featured on the cover of the inaugural issue of the new journal Optica,* is the first demonstration of all-optical control of the microcomb, and its accurate conversion of optical frequencies to lower microwave frequencies. (Optical frequencies are too high to count; microwave frequencies can be counted with electronics.)
The new clock architecture might eventually be used to make portable tools for calibrating frequencies of advanced telecommunications systems or providing microwave signals to boost stability and resolution in radar, navigation and scientific instruments. The technology also has potential to combine good timekeeping precision with very small size. The comb clock might be a component of future "NIST on a chip" technologies offering multiple measurement methods and standards in a portable form.
"The microcomb clock is one way we might get precision frequency metrology tools out of the lab and into real-world settings," NIST physicist Scott Diddams says.
Frequency combs produce precisely defined colors, or frequencies, of light that are evenly spaced throughout the comb's range. (The name comes from the spectrum's resemblance to the teeth of a pocket comb.) The original combs required relatively large lasers that produced rapid, extremely short pulses of light, but more recently NIST and other laboratories have developed much smaller microcombs.
For more info and visuals, go to http://www.nist.gov/pml/div688/comb-072214.cfm