Dual-Comb Spectroscopy Calculator

Model dual-comb spectroscopy parameters: resolution, bandwidth, update rate, and multi-heterodyne RF spectrum.

Comb 1 rep rate f_r (MHz)Comb 2 rep rate (MHz)Number of comb teeth Nf_CEO comb 1 (MHz)f_CEO comb 2 (MHz)Center wavelength (nm)

Δf_r

200.0 Hz

compression f_r/Δf_r = 5.000e+5

Update time 1/Δf_r

5.000 ms

one interferogram

Optical bandwidth

10.00 THz

80.14 nm

Alias-free limit f_r²/(2Δf_r)

25.00 THz

200.3 nm

RF image of the band

3.072–23.07 MHz

N·Δf_r = 20.00 MHz of [0, 50.00] MHz

Resolution (tooth spacing)

100.0 MHz

0.8014 pm

Optical → RF Mapping

Each comb-1 tooth beats with the nearest comb-2 tooth. Alias-free, the points form one straight line inside [0, f_r/2]; a fold at 0 or at f_r/2 means two optical frequencies land on the same RF frequency.

Model

ν_j(n) = n f_r,j + f_0,j, f_RF(n) = |wrap(n Δf_r + Δf₀)| into [0, f_r/2]

Δν ≤ f_r²/(2Δf_r), T_update = 1/Δf_r, compression = f_r/Δf_r

Comb equation and sampling arithmetic, exact (Coddington, Newbury & Swann, "Dual-comb spectroscopy", Optica 3, 414, 2016). The interferogram is sampled once per pulse, so its Nyquist frequency is f_r/2. The band's image must sit inside one half-band, which depends on the absolute tooth numbers and the offset frequencies, not only on the bandwidth limit.

Model and references

Exact. The equations are exact within the stated assumptions, or are a standard's tabulated values. The results are as good as the inputs. About the tiers

Comb equation and sampling arithmetic. The mapping from optical tooth to RF beat is alias-free only if the band's image stays in one half-band, which needs Δν ≤ f_r²/(2|Δf_r|) and suitable offset frequencies.

Coddington I., Newbury N., Swann W. (2016). Dual-comb spectroscopy. Optica 3, 414. doi:10.1364/optica.3.000414

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