Phase Coherent Vacuum-Ultraviolet to Radio Frequency Comparison with a Mode-Locked Laser

J. Reichert; M. Niering; R. Holzwarth; M. Weitz; Th. Udem; T. W. Hänsch

doi:10.1103/PhysRevLett.84.3232

Milestone

Phase Coherent Vacuum-Ultraviolet to Radio Frequency Comparison with a Mode-Locked Laser

J. Reichert, M. Niering, R. Holzwarth, M. Weitz, Th. Udem, and T. W. Hänsch

Phys. Rev. Lett. 84, 3232 – Published 10 April 2000

An article within the collection: Letters from the Past - A PRL Retrospective

Abstract

We demonstrate a versatile new technique that provides a phase coherent link between optical frequencies and the radio frequency domain. The regularly spaced comb of modes of a mode-locked femtosecond laser is used as a precise ruler to measure a large frequency gap between two different multiples (harmonics or subharmonics) of a laser frequency. In this way, we have determined a new value of the hydrogen $1 S - 2 S$ two-photon resonance, $f_{1 S - 2 S} = 2 466 061 413 187.29 (37) kHz$ , representing now the most accurate measurement of an optical frequency.

Received 18 November 1999

DOI:https://doi.org/10.1103/PhysRevLett.84.3232

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Letters from the Past - A PRL Retrospective

2008 marked PRL’s 50th anniversary. As part of the celebrations a collection of milestone Letters was started. The collection contains Letters that have made long-lived contributions to physics, either by announcing significant discoveries, or by initiating new areas of research.