Absolute Frequency Measurements of theHg+and Ca Optical Clock Transitions with a Femtosecond Laser

• DOI: 10.1103/physrevlett.86.4996
• Publication Date: 2002-07-27T01:44:38Z
• Authors: Th. Udem; S. A. Diddams; K. R. Vogel; C. W. Oates; E. A. Curtis; W. D. Lee; W. M. Itano; R. E. Drullinger; J. C. Bergquist; L. Hollberg
• Keywords: Atomic Physics (physics.atom-ph); 0103 physical sciences; FOS: Physical sciences; 01 natural sciences; Physics - Atomic Physics; Physics - Optics; Optics (physics.optics)

The frequency comb created by a femtosecond mode-locked laser and microstructured fiber is used to phase coherently measure the frequencies of both Hg+ Ca optical standards with respect SI second. We find transition be f(Hg) = 1 064 721 609 899 143(10) Hz f(Ca) 455 986 240 494 158(26) Hz, respectively. In addition unprecedented precision demonstrated here, this work precursor all-optical atomic clocks based on standards. Furthermore, when combined previous measurements, we no time variations these within uncertainties absolute value of( partial differential f(Ca)/ t)/f(Ca) < or =8 x 10(-14) yr(-1) of(partial f(Hg)/ t)/f(Hg) =30 yr(-1).