Dual-comb hyperspectral digital holography

Abstract

Holography1 has always held special appeal as it is able to record and display spatial information in three dimensions2–10. Here we show how to augment the capabilities of digital holography11,12 by using a large number of narrow laser lines at precisely defined optical frequencies simultaneously. Using an interferometer based on two frequency combs13–15 of slightly different repetition frequencies and a lensless camera sensor, we record time-varying spatial interference patterns that generate spectral hypercubes of complex holograms, revealing the amplitudes and phases of scattered wave-fields for each comb line frequency. Advancing beyond multicolour holography and low-coherence holography (including with a frequency comb16), the synergy of broad spectral bandwidth and high temporal coherence in dual-comb holography opens up novel optical diagnostics, such as precise dimensional metrology over large distances without interferometric phase ambiguity, or hyperspectral three-dimensional imaging with high spectral resolving power, as we demonstrate with molecule-selective imaging of an absorbing gas.

Performance and limitations of dual-comb based ranging systems

“…Apart from LiDAR applications, the analysis presented in this work can be applied to other techniques relying on the estimation of the phases change as a function of the frequency. For instance, recent results in dual-comb holography [34] rely on the use of multiple comb lines to perform holographic measurement by unwrapping the phases differences of multiple synthetic wavelengths. Therefore, the tradeoff between non-ambiguity range and precision is similar to the one presented in this article.…”

Advances in Digital Holographic Interferometry

“…This method is realized due to the simultaneous use of a large number of narrow laser lines at precisely defined optical frequencies. The usage of an interferometer based on two frequency ranges with slightly different repetition frequencies and a camera sensor without a lens allows for recording time-varying spatial interference patterns that generate spectral hypercubes of complex holograms, revealing the amplitudes and phases of scattered wave fields for each frequency of the comb line [ 3 , 11 ]. A similar method is used by other authors [ 12 ].…”

High-Resolution Quantum Cascade Laser Dual-Comb Spectroscopy in the Mid-Infrared with Absolute Frequency Referencing

“…Over the last two decades, dual-comb spectroscopy [12] has developed into a powerful tool for applications requiring fast temporal resolution, high spectral accuracy, and broad spectral coverage. It has enabled difficult or previously impossible measurements, such as multispecies trace gas detection in open-path [13], monitoring of irreversible processes with micro-second resolution [2], hyperspectral 3D imaging [14], and fast determination of isotope ratios of multiple species [15]. Moreover, photonic chip integrated comb sources such as microcombs [4], quantum cascade lasers (QCL) [1], and interband cascade lasers [5], are potential game-changers, by enabling mass-producible integrated gas sensors for demanding fields, such as health, security, environment, and industrial process monitoring.…”