Abstract
Electro-optic frequency comb generators are particularly promising for dual-comb spectroscopy. They provide a high degree of mutual coherence between the combs without resorting to complex feedback stabilization mechanisms. In addition, electro-optic frequency combs can operate at very high repetition rates, thus providing very fast acquisition speeds. Here, we exploit these two features to resolve the rapid movement of a vibrating target. Our electro-optic dual-comb interferometer is capable of combining time-of-fight information with a more precise interferometric measurement based on the carrier phase. This fact, previously demonstrated by stabilized femtosecond frequency combs, allows us to increase the precision of the time-of-flight measurement by several orders of magnitude. As a proof of concept, we implement a fiber-based vibrometer that offers sub-nanometer precision at an effective acquisition speed of 250 kHz. These results expand the application landscape of electro-optic dual-comb spectroscopy to laser ranging and other remote sensing measurements.
Highlights
Coherent dual-comb spectroscopy (DCS) is an interferometric technique that exploits the resolution and accuracy offered by optical frequency combs to characterize spectroscopic samples in amplitude and phase [1]
Electro-optic frequency comb generators are promising for dual-comb spectroscopy
They provide a high degree of mutual coherence between the combs without resorting to complex feedback stabilization mechanisms
Summary
Coherent dual-comb spectroscopy (DCS) is an interferometric technique that exploits the resolution and accuracy offered by optical frequency combs to characterize spectroscopic samples in amplitude and phase [1]. The distinctive advantage of DCS is its ability of resolving individual comb lines whose spacing is usually finer than the resolution provided by standard commercial spectrometers [2] This is possible thanks to the combination of two combs with slightly different repetition rates, enabling a virtual scanning over much longer delays than what is possible with conventional Fourier transform spectrometers. Nanometer precision for an absolute range of > 1 m has been recently demonstrated [6], avoiding systematic errors due to spurious reflections that are observed in multiwavelength interferometric procedures [14] This exceptional result is possible thanks to the combination of time-of-flight (TOF) information, a common method for laser ranging [15], together with an interferometric range measurement related to the phase of the optical carrier [16,17]. In a proof-of-principle demonstration, we resolve sub-nanometer displacements from ultrasound vibrations operating at a maximum refresh rate of 250 kHz
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