Nanosecond time-resolved dual-comb absorption spectroscopy

Frequency combs have revolutionized the field of optical spectroscopy, enabling researchers to probe molecular systems with a multitude of accurate and precise optical frequencies. Although there have been tremendous strides in direct frequency comb spectroscopy, these approaches have been unable to record high-resolution spectra on the nanosecond-timescale characteristic of many physiochemical processes. Here we demonstrate a new approach to achieve optical frequency comb generation in which a pair of electro-optic combs is produced in the near-infrared regime and subsequently transferred with high mutual coherence and efficiency into the mid-infrared regime within a single optical parametric oscillator. The high power, mutual coherence and agile repetition rates of these combs, as well as the large mid-infrared absorption of many molecular species, enable fully resolved spectral transitions to be recorded in timescales as short as 20 ns. We have applied this approach to study the rapid dynamics occurring within a supersonic pulsed jet; however, we note that this method is widely applicable to fields such as chemical and quantum physics, atmospheric chemistry, combustion science and biology. A mid-infrared dual-comb system capable of nanosecond time-resolved spectral measurements is realized by using a singly resonant optical parametric oscillator that allows an efficient conversion of an input dual-comb pump at 1 µm into an idler dual comb in the mid-infrared regime.