Dual-Comb Spectroscopy in the Water-Transparent 8-12 μm Region

Dual-comb spectroscopy (DCS) is emerging as a technique of choice to measure gas absorption spectra over broad bands at high temporal resolution [1]. The extension of this technique to the mid-infrared is crucial for chemical kinetic studies in combustion environments, where a typically short absorption path length must be compensated by strong absorption features to enhance the signal-to-noise ratio over a short measurement time. It was only very recently that DCS has been demonstrated at full resolution [2], i.e. without apodization [3], in the spectroscopically rich water-free 8–12
$\mu \mathrm{m}$
absorption region. As a drawback, this was achieved with a rather complex apparatus driven by self-referenced Cromium combs at a repetition frequency
$(f_{\text{rep}})$
of only 80 MHz.