Coherent Light from the UV to THz

Analytical optical methods are vital to our modern society as they permit the fast and secure identi­fication of substances within solids, liquids or gases. These methods rely on light interacting with each of these substances dif­ferently at different parts of the optical spectrum. For instance, the ultra­violet range of the spectrum can directly access electronic transitions inside a substance while the terahertz is very sensitive to molecular vibra­tions.

Artistic impression of the spectrum of a mid-infrared pulse broadening in the background with the electric field of the generated pulse. (Source: L. Maidment, U. Elu & J. Biegert, ICFO)

Throughout the years many techniques have been developed to achieve hyper­spectral spectro­scopy and imaging, allowing scientists to observe the behavior of, for example, molecules when they fold, rotate or vibrate in order to understand the identi­fication of cancer markers, greenhouse gases, pollutants or even substances that could be harmful to us. These ultra­sensitive techniques have proven to be very useful in appli­cations related to food inspection, biochemical sensing or even in cultural heritage, to inves­tigate the structure of the materials used for ancient objects, paintings or sculptures. A standing challenge has been the absence of compact sources that cover such large spectral range with sufficient brightness. Synchro­trons provide the spectral coverage, but they lack the temporal coherence of lasers, and such sources are available only in large-scale user facilities.

Now, an inter­national team of researchers from ICFO, the Max-Planck Institute for the Science of Light, the Kuban State Univer­sity, and the Max-Born-Institute for Nonlinear Optics and Ultra­fast Spectro­scopy, led by Jens Biegert, report on a compact high-brightness mid-IR-driven source combining a gas-filled anti-resonant-ring photonic crystal fiber with a novel nonlinear-crystal. The table top source provides a seven-octave coherent spectrum from 340 nm to 40,000 nm with spectral brightness 2-5 orders of magnitude higher than one of the brightest Synchro­tron faci­lities.

Future research will leverage the few-cycle pulse duration of the source for the time-domain analysis of substances and materials, thus opening new oppor­tunities for multimodal measurement approaches in areas such as molecular spectro­scopy, physical chemistry or solid-state physics, to name a few. (Source: ICFO)

Reference: U. Elu et al.: Seven-octave high-brightness and carrier-envelope-phase-stable light source, Nat. Phot., online 14 December 2020; DOI: 10.1038/s41566-020-00735-1

Link: Attoscience and Ultrafast Optics, ICFO – Institut de Ciencies Fotoniques, Barcelona Institute of Science and Technology, Barcelona, Spain

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