Time-domain spectroscopy in the mid-infrared

• Published in: Scientific reports Vol. 4; no. 1; p. 6670
• Main Authors: Lanin, A. A., Voronin, A. A., Fedotov, A. B., Zheltikov, A. M.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 20-10-2014; Nature Publishing Group
• Subjects: 639/624/400/385; 639/624/400/584; Electromagnetic fields; Experiments; Gating; Humanities and Social Sciences; Infrared spectroscopy; Lasers; multidisciplinary; Physics; Propagation; Radiation; Science; Sensors; Spectrometers; Spectrum allocation
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep06670

When coupled to characteristic, fingerprint vibrational and rotational motions of molecules, an electromagnetic field with an appropriate frequency and waveform offers a highly sensitive, highly informative probe, enabling chemically specific studies on a broad class of systems in physics, chemistry, biology, geosciences and medicine. The frequencies of these signature molecular modes, however, lie in a region where accurate spectroscopic measurements are extremely difficult because of the lack of efficient detectors and spectrometers. Here, we show that, with a combination of advanced ultrafast technologies and nonlinear-optical waveform characterization, time-domain techniques can be advantageously extended to the metrology of fundamental molecular motions in the mid-infrared. In our scheme, the spectral modulation of ultrashort mid-infrared pulses, induced by rovibrational motions of molecules, gives rise to interfering coherent dark waveforms in the time domain. These high-visibility interference patterns can be read out by cross-correlation frequency-resolved gating of the field in the visible generated through ultrabroadband four-wave mixing in a gas phase.