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The Measurement of Optical Frequencies



Leo W. Hollberg, Scott A. Diddams, A Bartels, Tara M. Fortier, Kyoungsik Kim


Even the suggestion of counting optical frequencies in the visible (~ 500 THz) must have seemed ludicrous to many in the past, because traditional methods failed to work above about 100 GHz. Nonetheless, with some vision and new ideas a few researchers had the will to try. This feat was finally accomplished in the 1970s and 1980s and resulted in a defined speed of light and a redefinition of the unit of length, the meter. Of particular importance was the goal of making a coherent connection of optical frequencies to microwaves sources and electronics. An even more powerful and useful tool is the recently developed femtosecond laser based frequency synthesizer that can connect any arbitrary frequency to any other frequency from DC to 1000 THz. These technologies are the subject of this paper.


femtosecond laser, frequency standard, frequency synthesis, optical frequency measurement


Hollberg, L. , Diddams, S. , Bartels, A. , Fortier, T. and Kim, K. (2005), The Measurement of Optical Frequencies, Metrologia, [online], (Accessed June 14, 2024)


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Created June 7, 2005, Updated February 17, 2017