Spreading the technique

"If Hansch's technique can be made practical and portable, we'd be stand­ing first in line to use it," says Kleppner. "But right now his laser chain is so big and complex that I don't know of any American lab that could reproduce it in the present funding climate. The US used to be in the forefront of atomic clock development. But with our declining support, the leadership has passed to Germany and France. Optical frequency research is a perfect example of a new technology being spawned by basic research."

A senior scientist at the US National Institute of Standards and Technology was recently overheard to say, "If any­one at NIST admitted he was setting out to do something as pure as testing QED, he'd be in trouble." But beyond its purely scientific value, the ability to measure optical frequencies to high precision should give us better atomic clocks for a myriad of practical appli­cations. "With the 10¹⁰ Hz frequency of a cesium atomic clock," explains Hansch, "you have to wait hours to get a ∆t precision of 10^-14. But with a clock based on optical transitions, you could get 10^-15 in one second."

“To make our new technique acces­sible to other labs," Hansch told us, "we want to replace all our big, costly lasers with small, compact semiconductor diode lasers. We're already us­ing such diodes in our latest frequency divider chain [see the photo above]. The special grating-stabilized diode la­sers we've designed are now being mar­keted by a German firm."