Abstract

In recent years femtosecond frequency-comb lasers have been successfully applied in broadband cavity enhanced spectroscopy [1,2]. The challenge with these new applications is that the regularly spaced frequency structure of the comb is resonantly matched to the modes of a high-finesse cavity where the comb laser interacts with a trace gas possessing a unique absorption spectrum. The signal detection after the cavity is then typically based either on a dispersive spectrometer in conjunction with a time dependent ring-down measurement [1], or on the use of a second readout frequency-comb laser for multi-heterodyne Fourier transform spectroscopy [2] (dual-comb spectroscopy [3]).

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