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Frequency Uncertainty for Optically Referenced Femtosecond Laser Frequency Combs



Long-Sheng Ma, Zhiyi Bi, A Bartels, Kyoungsik Kim, Lennart Robertsson, Massimo Zucco, Robert Windeler, G Wilpers, Christopher W. Oates, Leo W. Hollberg, Scott Diddams


We present measurements and analysis of the currently known residual frequency uncertainty of femtosecond laser frequency combs (FLFCs) based on Kerr-lens mode-locked Ti:sapphire lasers. Broadband frequency combs generated directly from the laser oscillator, as well as octave-spanning combs generated with nonlinear optical fiber are compared. The residual uncertainty introduced by an optically-referenced FLFC is measured for both its optical and microwave outputs. We find that the fractional frequency uncertainty of the optical and microwave outputs of the FLFC can be as low as 8e-20 and 1.7e-18, with confidence level of 95%, respectively. Photo-detection of the optical pulse train introduces excess noise, which degrades the instability and subsequent uncertainty limit of the microwave output to 2.6e-17.
IEEE Journal of Quantum Electronics


femtosecond laser, frequency comb, optical clock


Ma, L. , Bi, Z. , Bartels, A. , Kim, K. , Robertsson, L. , Zucco, M. , Windeler, R. , Wilpers, G. , Oates, C. , Hollberg, L. and Diddams, S. (2007), Frequency Uncertainty for Optically Referenced Femtosecond Laser Frequency Combs, IEEE Journal of Quantum Electronics, [online], (Accessed June 13, 2024)


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Created January 31, 2007, Updated October 12, 2021