Coherent multiheterodyne spectroscopy using stabilized optical frequency combs

Phys Rev Lett. 2008 Jan 11;100(1):013902. doi: 10.1103/PhysRevLett.100.013902. Epub 2008 Jan 2.


The broadband, coherent nature of narrow-linewidth fiber frequency combs is exploited to measure the full complex spectrum of a molecular gas through multiheterodyne spectroscopy. We measure the absorption and phase shift experienced by each of 155 000 individual frequency-comb lines, spaced by 100 MHz and spanning from 1495 to 1620 nm, after passing through hydrogen cyanide gas. The measured phase spectrum agrees with the Kramers-Kronig transformation of the absorption spectrum. This technique can provide a full complex spectrum rapidly, over wide bandwidths, and with hertz-level accuracy.