Linear detection of 30 mW dual-comb interferograms

TL;DR

This paper demonstrates that high-bandwidth, non-amplified photodetectors can produce linear dual-comb interferograms at 30 mW power levels by managing impulse response overlap, reducing nonlinear artifacts significantly.

Contribution

It introduces a method to achieve linear dual-comb interferograms at high power using non-amplified detectors by analyzing impulse response conditions.

Findings

Nonlinear artifacts are at least 35 dB below the signal at 30 mW.

No systematic transmittance error from nonlinearity in spectroscopic measurements.

Proper management of impulse response overlap enables linear detection at high power.

Abstract

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.