Finer Optical Ticks

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Science  16 Jul 2004:
Vol. 305, Issue 5682, pp. 313
DOI: 10.1126/science.305.5682.313a

In mechanical timepieces, the resolution to which time can be sliced is dependent on how fine the movement is. Typically, this is limited to hundredths of a second, or equivalent to the movement running at several hundred cycles per second. However, the precision to which the time slice can be determined is also dependent on the width of the ticks around the clock face. The development of optical frequency standards allows a much finer movement to be accessed (∼1015 cycles per second), but analogously, the precision to which the time increments can be determined is dependent on the linewidth of the laser light being used. Webster et al. tackle the problem of linewidth broadening by isolating the light frequency, in this case the resonance frequency of a high-finesse Fabry-Perot etalon, from many of the sources of external noise. By reducing external parameters such as temperature and pressure fluctuations, acoustic noise, and expansion due to heating from the light itself, they show that the linewidth of the etalon resonance frequency can be reduced to below 0.5 Hz. The ability to stabilize light to such high resolution is important not only for the further development of precise timekeeping but also for applications in fundamental physics and tests of special relativity. — ISO

Op. Lett. 29, 1497 (2004).

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