Spectroscopy method IDs, quantifies molecular species in real time

An international team of scientists has developed a real-time identification and quantification method for molecules.

Content Dam Bow Online Articles 2014 02 Pr 14 02 28

A team of scientists at the Laser Spectroscopy Division of the Max Planck Institute of Quantum Optics (MPQ; Garching, Germany), Ludwig Maximilian University (LMU; Munich, Germany), and the Institut des Sciences Moléculaires d’Orsay (France) has developed a real-time identification and quantification method for molecules. The work has implications in areas such as bioimaging, where real-time recording of molecular spectra is important.

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Dual-comb spectroscopy has demonstrated exciting potential for ultra-rapid recording of complex molecular spectra. When compared to state-of-the-art instrumentation used in Fourier transform spectroscopy, it shortens recording times from seconds to microseconds. Dual-comb spectroscopy without moving parts harnesses two laser frequency combs (coherent sources that emit a regular train of ultrashort pulses) to perform interferometric measurements, but it is difficult to synchronize the two lasers within the required precision. Recognizing this, the research team developed a new approach that enabled them to use unstabilized free-running femtosecond lasers without sacrificing performance. By generating proper clock signals, they compensated for laser short-term instabilities by electronic signal processing only.

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Content Dam Bow Online Articles 2014 02 Pr 14 02 28
Portion of a dual-comb real-time absorption spectrum of acetylene in the near-infrared (NIR) region. While the spectrum without the adaptive sampling (blind sampling) is strongly distorted, the adaptive spectrum accurately reveals the molecular profiles. (Image courtesy of MPQ/Laser Spectroscopy Division)

The possibility of using femtosecond lasers without any sophisticated stabilization scheme considerably eases the implementation of a dual-comb spectrometer. "It should facilitate applications to real-time sensing," comments Takuro Ideguchi, who just completed his doctoral dissertation partly based on this experiment. "Dual-comb spectroscopy holds much promise for new approaches to molecular physics and our scheme of adaptive sampling is a key to their efficient implementation. Enhanced sensitivity for weak concentrations is within reach with the development of mid-infrared frequency combs, while nonlinear dual-comb spectroscopy provides intriguing prospects for applications ranging from bioimaging to precision spectroscopy."

Full details of the work appear in the journal Nature Communications; for more information, please visit http://dx.doi.org/10.1038/ncomms4375.

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