Abstract
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.
Highlights
Atmospheric optics is one of the earliest fields in optics, but among all the natural sciences[1, 2]
Our experiments reveal clear signatures of anomalous group-velocity dispersion (GVD) in this wavelength range, with group delays as long as 1.8 ps detected across the bandwidth covered by 80-fs laser pulses
Dispersion of atmospheric air within the 3.5–4.2-μm wavelength range is dominated by the 00°01–00°11 asymmetric-stretch rovibrational band of atmospheric CO2
Summary
Atmospheric optics is one of the earliest fields in optics, but among all the natural sciences[1, 2]. In the era of ultrafast laser technologies, enabling the generation of high-power ultrashort field waveforms within an ultrabroad spectral range from the visible to the mid-infrared, a deeper understanding of the group-velocity dispersion (GVD) of atmospheric air is needed.
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