Femtosecond laser is best measure of optical frequency

17 Jun 2002

The frequency of visible light emitted by a caesium atom undergoing an electronic transition has been measured to a much greater precision than previously possible.

Researchers at the Max Planck Institute for Quantum Optics in Germany have determined high frequencies of light very accurately used the regular spacing of the peaks in the spectrum resulting from a femtosecond laser pulse.

Thomas Udem, one of the researchers from the Max Planck Institute, told OPTICS.ORG, "In a paper to appear on 1 July 1999 in Optics Letters we show that the mode spacing constancy is fulfilled within a few parts in 10¹⁷. The best clocks today do not even reach one part in 10¹⁵."

The accuracy of the frequency measurements holds great potential for metrology. Currently the technique is applied to basic research but it paves the way for optical clocks with greater accuracy than the best atomic clocks.

According to Udem, the next step will be to improve the measurements of the radiation from electronic transitions in hydrogen atoms. The team will also modify the spectral width of the pulsed laser, with shorter pulses and nonlinear effects in fibres.

SH