Optical frequency comb spectroscopy
Aleksandra Foltynowicz, Department of Physics, Umeå University
(aleksandra.foltynowicz@physics.umu.se)
Optical frequency combs are produced by femtosecond mode-locked lasers, whose spectrum spans
tens or hundreds of terahertz of bandwidth and consists of a series of narrow equidistant modes. The
unique combination of wide bandwidth and high spectral resolution offered by the frequency combs
has opened up exciting new possibilities in spectroscopy. Absorption spectroscopy performed with
optical frequency combs is virtually equivalent to a simultaneous measurement with tens of
thousands of narrow synchronized laser lines, and allows multiplexed detection of many gaseous
species with high selectivity in short acquisition times. Moreover, due to its regular spectrum, a
frequency comb can be efficiently coupled into an external high finesse cavity, which enhances the
interaction length with the sample and results in high absorption sensitivity. The recent development
of frequency comb sources in the mid-infrared wavelength range provides access to strong
fundamental ro-vibrational transitions of a wide range of molecules and allows achieving low
detection limits in terms of gas concentrations. In this talk I will describe the principles of cavityenhanced optical frequency comb spectroscopy and give examples of the performance and
applications of the technique.