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17 Jun 2002
A new method for measuring the frequency of visible and infrared light to a high precision has been developed by a team of researchers from Lucent Technologies' Bell Labs and the US National Institute of Standards (NIST).
The technique employs a single laser and offers a higher level of precision than expensive multiple laser systems because it compares the frequency directly with the well-defined frequency standard of a cesium-133 atomic clock. The researchers believe that the technique could lead to a level of precision that is only limited by that of the atomic clock itself.
The experiments, which were carried out at JILA, a joint research initiative of NIST and the University of Colorado at Boulder, involved a radio-frequency-clock-stabilized titanium-sapphire laser. The laser was "locked" so that it generated a repetitive train of ultrashort optical pulses and gave an output spectrum consisting of sharply defined spectral lines separated by the repetition frequency.
In this case, the envelopes of the pulses and the waves of the laser light were locked together with a controlled relationship and the repetition rate of the pulses was locked to the standard cesium microwave frequency (9.2 GHz). This makes it possible to determine the absolute optical frequencies of each line is the laser's spectrum with a single laser.
This research was reported in the 28 April 2000 issue of the journal Science.
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