Dual-comb spectroscopy, sometimes abbreviated to DCS, is an advanced spectroscopic technique.\u00a0 This technique deploys two coherent laser sources with discrete, equally-spaced frequency lines. A laser source with this type of spectrum is defined as a frequency comb. <\/p>\n\n\n\n
The primary benefit of using two frequency combs is that your sample\u2019s spectral response can be quickly assessed on what is known as a tooth-by-tooth basis. But what does this mean in practice? \u00a0 <\/p>\n\n\n\n
It is worth digging into the working principles of dual-comb spectroscopy to truly understand the benefits of this pioneering spectroscopic tool. \u00a0<\/p>\n\n\n\n
In dual-comb spectroscopy, the idea is to generate an RF spectrum by heterodyning two distinct frequency combs with slightly different repetition rates. The resulting RF comb comprises distinguishable beats between pairs of optical comb teeth. \u00a0 <\/p>\n\n\n\n
This works by placing a sample in the optical beam paths of one\/both of your coherent laser sources and recovering the encoded response via heterodyne detection. A rapid photodiode acquires and combines both beams into a characteristic RF comb which is accessible by standard electronics. \u00a0 <\/p>\n\n\n\n
Spectra in the optical and RF domains should have an equal correspondence. This means the RF comb can be reliably sampled to produce a digital spectrum with all your relevant spectroscopic data. \u00a0<\/p>\n\n\n\n
Different configurations will yield different information, but dual-comb spectroscopy is widely renowned for its speed, precision, and stability. It can provide rapid, broadband spectral measurements with exceptional resolution and high signal-to-noise ratios. The ability to carry out spectral analysis via RF referencing is also desirable for its ease and simplicity. That simplicity stems into the general architecture of dual-comb spectroscopy too. \u00a0 <\/p>\n\n\n\n
Unlike conventional spectroscopic tools, dual-comb spectroscopy requires no complex moving parts nor gratings to separate optical frequencies and spread the optical spectrum. This carries out digitally in the RF domain. <\/p>\n\n\n\n
One consequence of this is that both optical paths can easily implement on optical fibres or photonic chips.\u00a0 This significantly reduces the design complexity. This makes dual-comb spectrometers small and robust, with excellent compensation for external perturbations. \u00a0<\/p>\n\n\n\n