Fourier-Transform and Dual-Comb Hybrid Spectroscopy*

Dual-comb spectroscopy is a powerful method for materials' characterization. Its working principle is based on Fourier-transform spectroscopy, but scanning between the pulses is done automatically without mechanical moving elements and hence it enables the measurements of linear spectra rapidly and with high spectral resolution. However, dual-comb spectroscopy has a low duty cycle especially when used for studying semiconductor materials and molecules in solutions whose excited states’ dephasing rates are much shorter than the spacing between the comb pulses. When DCS is applied to these systems, a vast majority of energy and acquisition time is wasted. Here, we demonstrate a simple approach that can aid efforts to solve this issue.  In our approach, we digitally control the relative locking phase between two combs, which allows us to control the delay between the comb pulses with very high precision and take the data rapidly and continuously only in the region where the signal is non-zero. We demonstrate the concept on a Neodymium-doped yttrium orthovanadate (Nd:YVO4) sample. We show that, we could scan the optical delay between the comb pulses over several ps in hundreds of µs. The interferograms obtained using this approach and conventional DCS are very similar and corresponding spectra are in very good agreement.