Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Molecular fingerprinting with the resolved modes of a femtosecond laser frequency comb


The control of the broadband frequency comb1 emitted from a mode-locked femtosecond laser has permitted a wide range of scientific and technological advances—ranging from the counting of optical cycles for next-generation atomic clocks1,2 to measurements of phase-sensitive high-field processes3. A unique advantage of the stabilized frequency comb is that it provides, in a single laser beam, about a million optical modes with very narrow linewidths4 and absolute frequency positions known to better than one part in 1015 (ref. 5). One important application of this vast array of highly coherent optical fields is precision spectroscopy, in which a large number of modes can be used to map internal atomic energy structure and dynamics6,7. However, an efficient means of simultaneously identifying, addressing and measuring the amplitude or relative phase of individual modes has not existed. Here we use a high-resolution disperser8,9 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 vapour, acquiring in a few milliseconds absorption images covering over 6 THz of bandwidth with high frequency resolution. Our technique for direct and parallel accessing of stabilized frequency comb modes could find application in high-bandwidth spread-spectrum communications with increased security, high-resolution coherent quantum control, and arbitrary optical waveform synthesis10 with control at the optical radian level.

This is a preview of subscription content

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Experimental set-up.
Figure 2: Two-dimensional spectrograms of optical frequency ‘brush’.
Figure 3: Concatenated line spectra.
Figure 4: Absorption spectra of P(32)6–3, R(59)8–4 and R(53)8–4 transitions in iodine.


  1. 1

    Udem, T., Holzwarth, R. & Hansch, T. W. Optical frequency metrology. Nature 416, 233–237 (2002)

    ADS  CAS  Article  Google Scholar 

  2. 2

    Diddams, S. A. et al. An optical clock based on a single trapped 199Hg+ ion. Science 293, 825–828 (2001)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Baltuska, A. et al. Attosecond control of electronic processes by intense light fields. Nature 421, 611–615 (2003)

    ADS  CAS  Article  Google Scholar 

  4. 4

    Bartels, A., Oates, C. W., Hollberg, L. & Diddams, S. A. Stabilization of femtosecond laser frequency combs with subhertz residual linewidths. Opt. Lett. 29, 1081–1083 (2004)

    ADS  CAS  Article  Google Scholar 

  5. 5

    Oskay, W. H. et al. Single-atom optical clock with high accuracy. Phys. Rev. Lett. 97, 020801 (2006)

    ADS  CAS  Article  Google Scholar 

  6. 6

    Marian, A., Stowe, M. C., Lawall, J. R., Felinto, D. & Ye, J. United time-frequency spectroscopy for dynamics and global structure. Science 306, 2063–2068 (2004)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Gerginov, V., Tanner, C. E., Diddams, S. A., Bartels, A. & Hollberg, L. High-resolution spectroscopy with a femtosecond laser frequency comb. Opt. Lett. 30, 1734–1736 (2005)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Shirasaki, M. Large angular dispersion by a virtually imaged phased array and its application to a wavelength demultiplexer. Opt. Lett. 21, 366–368 (1996)

    ADS  CAS  Article  Google Scholar 

  9. 9

    Xiao, S. & Weiner, A. M. 2-D wavelength demultiplexer with potential for ≥ 1000 channels in the C-band. Opt. Express 12, 2895–2901 (2004)

    ADS  Article  Google Scholar 

  10. 10

    Jiang, Z., Seo, D. S., Leaird, D. E. & Weiner, A. M. Spectral line-by-line pulse shaping. Opt. Lett. 30, 1557–1559 (2005)

    ADS  CAS  Article  Google Scholar 

  11. 11

    Baklanov, Y. V. & Chebotayev, V. P. Narrow resonances of two-photon absorption of super-narrow pulses in a gas. Appl. Phys. 12, 97–99 (1977)

    ADS  CAS  Article  Google Scholar 

  12. 12

    Teets, R., Eckstein, J. & Hänsch, T. W. Coherent two-photon excitation by multiple light pulses. Phys. Rev. Lett. 38, 760–764 (1977)

    ADS  CAS  Article  Google Scholar 

  13. 13

    Jones, D. J. et al. Carrier-envelope phase control of femtosecond mode-locked lasers and direct optical frequency synthesis. Science 288, 635–639 (2000)

    ADS  CAS  Article  Google Scholar 

  14. 14

    Lepetit, L., Cheriaux, G. & Joffre, M. Linear techniques of phase measurement by femtosecond spectral interferometry for applications in spectroscopy. J. Opt. Soc. Am. B 12, 2467–2474 (1995)

    ADS  CAS  Article  Google Scholar 

  15. 15

    Bartels, A. & Kurz, H. Generation of a broadband continuum by a Ti:sapphire femtosecond oscillator with a 1-GHz repetition rate. Opt. Lett. 27, 1839–1841 (2002)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Ramond, T. M., Diddams, S. A., Hollberg, L. & Bartels, A. Phase-coherent link from optical to microwave frequencies by means of the broadband continuum from a 1-GHz Ti:sapphire femtosecond oscillator. Opt. Lett. 27, 1842–1844 (2002)

    ADS  CAS  Article  Google Scholar 

  17. 17

    Wang, S. X., Xiao, S. & Weiner, A. M. Broadband, high spectral resolution 2-D wavelength-parallel polarimeter for dense WDM systems. Opt. Express 13, 9374–9380 (2005)

    ADS  CAS  Article  Google Scholar 

  18. 18

    Jenkins, F. A. & White, H. E. Fundamentals of Optics 4th edn (McGraw Hill, New York, 1976)

    MATH  Google Scholar 

  19. 19

    Quinn, T. J. Practical realization of the definition of the metre, including recommended radiations of other optical frequency standards (2001). Metrologia 40, 103–133 (2003)

    ADS  Article  Google Scholar 

  20. 20

    Kato, H. Doppler-Free High Resolution Spectral Atlas of Iodine Molecule 15000 to 19000 cm-1 (Japan Society for the Promotion of Science, Tokyo, 2000)

    Google Scholar 

  21. 21

    Thorpe, M. J., Moll, K. D., Jones, R. J., Safdi, B. & Ye, J. Broadband cavity ringdown spectroscopy for sensitive and rapid molecular detection. Science 311, 1595–1599 (2006)

    ADS  CAS  Article  Google Scholar 

  22. 22

    Simonsen, H. R. & Rose, F. Absolute measurements of the hyperfine splittings of six molecular 127I2 around the He-Ne/I2 wavelength at λ≈633 nm. Metrologia 37, 651–658 (2000)

    ADS  Article  Google Scholar 

Download references


We thank A. M. Weiner for discussions about the VIPA spectrometer, and J. Ye for discussions that motivated our application of frequency combs to broadband spectroscopy. We further thank J. Stalnaker and Y. LeCoq for their comments on this manuscript, and H. Kato for the CW iodine spectroscopy data. This paper is a contribution of the National Institute of Standards and Technology, with partial support from DARPA.

Author information



Corresponding author

Correspondence to Scott A. Diddams.

Ethics declarations

Competing interests

Reprints and permissions information is available at The authors declare no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Diddams, S., Hollberg, L. & Mbele, V. Molecular fingerprinting with the resolved modes of a femtosecond laser frequency comb. Nature 445, 627–630 (2007).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links