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Molecular fingerprinting with spectrally-resolved modes of a femtosecond laser frequency comb



Scott A. Diddams, Leo W. Hollberg, Vela Mbele


The control of the broadband frequency comb1 emitted from a mode-locked femtosecond laser has permitted a wide range of scientific and technological breakthroughs¿ranging from the counting of optical cycles for next-generation atomic clocks to measurements of phase-sensitive high-field processes. A unique advantage of the stabilized frequency comb is that it provides in a single laser beam ~10e6 optical modes that can all share Hz-level linewidths with absolute frequency positions known to better than one part per quadrillion. One important application of this vast array of highly coherent optical fields is in the field of precision spectroscopy, where a large number of modes can be used to map internal atomic energy structure. However, efficient means to simultaneously identify, address, and measure the amplitude or relative phase of individual modes has not existed. Here we present a solution to this problem using a high-resolution disperser to separate the individual modes of a stabilized frequency comb into a two-dimensional array in the image plane of the spectrometer. We illustrate the power of this technique for high-resolution spectral fingerprinting of molecular iodine vapor, acquiring absorption images covering >6 THz of bandwidth with ~5 kHz resolution in a few milliseconds. High bandwidth spread-spectrum communications, coherent quantum control, and arbitrary optical waveform synthesis are all areas that could benefit from the direct and parallel access to the individual frequency comb modes, as demonstrated here.


femtosecond laser frequency comb, molecular spectroscopy


Diddams, S. , Hollberg, L. and Mbele, V. (2007), Molecular fingerprinting with spectrally-resolved modes of a femtosecond laser frequency comb, Nature, [online], (Accessed March 1, 2024)
Created February 8, 2007, Updated February 17, 2017