  Detector nonlinearity is an important factor limiting the maximal power and
hence the signal-to-noise ratio (SNR) in dual-comb interferometry. To increase
the SNR without overwhelming averaging time, specific experimental conditions
must be met to ensure that photodetector nonlinearity is properly handled for
high input power. Detectors exhibiting nonlinear behavior can produce linear
dual-comb interferograms if the area of the detector's impulse response does
not saturate and if the overlap between successive time-varying impulse
responses is properly managed. Here, a high bandwidth non-amplified
photodetector is characterized in terms of its impulse response to high
intensity short pulses to exemplify the conditions. With 30 mW of continuous
power on the detector, nonlinear spectral artifacts in dual-comb interferograms
are at least 35 dB below the signal. A comparative spectroscopic measurement
with a frequency swept laser shows that no systematic transmittance error can
be attributed to nonlinearity.
