Mapping anomalous dispersion of air with ultrashort mid-infrared pulses

• Published in: Scientific reports 2017-05, Vol.7 (1), p.2103-7, Article 2103
• Main Authors: Mitrofanov, A. V., Voronin, A. A., Sidorov-Biryukov, D. A., Rozhko, M. V., Stepanov, E. A., Fedotov, A. B., Shumakova, V., Ališauskas, S., Pugžlys, A., Baltuška, A., Zheltikov, A. M.
• Format: Article
• Language: English
• Subjects: 639/624/400/584; 639/766/400/584; Carbon dioxide; Electromagnetic radiation; Humanities and Social Sciences; Lasers; multidisciplinary; Science; Science (multidisciplinary); Wavelength; Wavelengths
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-01598-3

We present experimental studies of long-distance transmission of ultrashort mid-infrared laser pulses through atmospheric air, probing air dispersion in the 3.6–4.2-μm wavelength range. Atmospheric air is still highly transparent to electromagnetic radiation in this spectral region, making it interesting for long-distance signal transmission. However, unlike most of the high-transmission regions in gas media, the group-velocity dispersion, as we show in this work, is anomalous at these wavelengths due to the nearby asymmetric-stretch rovibrational band of atmospheric carbon dioxide. The spectrograms of ultrashort mid-infrared laser pulses transmitted over a distance of 60 m in our experiments provide a map of air dispersion in this wavelength range, revealing clear signatures of anomalous dispersion, with anomalous group delays as long as 1.8 ps detected across the bandwidth covered by 80-fs laser pulses.