Physics

High-power terahertz sources

Print edition : September 06, 2013

Experiments and simulations show that the observed THz radiation is mostly emitted at large angles to the laser pulse direction. Photo: Physical Review Letters

IN a recent publication in the journal Physical Review Letters, a team of German researchers, led by Amrutha Gopal of the Institute of Optics and Quantum Electronics, Friedrich-Schiller-Universitat Jena, has reported a compact scheme that generates penetrating photon pulses with the highest peak power (of the order of gigawatts) ever reported.

Terahertz (THz) radiation—which passes through materials that block light and can be used to measure important properties of solids and molecules—could drive applications ranging from wireless communication to the imaging of biomolecules or semiconductor wafers. But technology for generating THz waves is still in its infancy and sufficiently powerful sources are not yet available.

In the present work, the scientists have demonstrated a laser-based source that emits short THz pulses with the highest peak power ever recorded in a laboratory.

The device is based on the team’s earlier observation that THz radiation is emitted from the rear surface of a solid target while interacting with an intense laser pulse. Numerical results point to a large part of the emission originating from a micron-scale plasma sheath at the rear surface of the target, which is also responsible for the ion acceleration.

The scheme may have an intriguing medical application: the set-up generates beams able to both detect and treat cancerous cells on human skin (which absorb THz wavelengths differently than healthy skin cells).

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