Claudia Gollner and the laser system at TU Wien. Credit score: TU Wien

A brand new, extraordinarily environment friendly supply of terahertz radiation has been developed at TU Wien (Vienna): Lasers flip air into plasma, thereby producing terahertz rays for a lot of potential purposes.

Terahertz radiation is used for safety checks at airports, for medical examinations and in addition for high quality checks in trade. Nevertheless, radiation within the terahertz vary is extraordinarily tough to generate. Scientists at TU Wien have now succeeded in growing a terahertz radiation supply that breaks a number of data: this can be very environment friendly, and its spectrum may be very broad — it generates completely different wavelengths from the complete terahertz vary. This opens up the opportunity of creating quick radiation pulses with extraordinarily excessive radiation depth. The brand new terahertz know-how has now been offered within the journal Nature Communications.

The “Terahertz Hole” Between Lasers and Antennas

“Terahertz radiation has very helpful properties,” says Claudia Gollner from the Institute of Photonics at TU Wien. “It could possibly simply penetrate many supplies, however not like X-rays, it’s innocent as a result of it isn’t ionizing radiation.”

From a technical standpoint, nonetheless, terahertz radiation is positioned in a frequency area which may be very onerous to entry – in type of a no man’s land between two well-known areas: Radiation with larger frequencies will be generated by extraordinary solid-state lasers. Low-frequency radiation, alternatively, as it’s utilized in cellular communications, is emitted by antennas. The best challenges lie precisely in between, within the terahertz vary.

Claudia Gollner

Claudia Gollner within the lab at TU Wien. Credit score: TU Wien

Within the laser laboratories of TU Wien, quite a lot of effort should due to this fact be put into producing the specified high-intensity terahertz radiation pulses. “Our place to begin is the radiation of an infrared laser system. It was developed at our Institute and it’s distinctive on the planet,” says Claudia Gollner. First, the laser mild is distributed by way of a so-called non-linear medium. On this materials, the infrared radiation is modified, a part of it’s transformed into radiation with twice the frequency.

“So now we have now two several types of infrared radiation. These two sorts of radiation are then superimposed. This creates a wave with an electrical subject with a really particular uneven form,” says Gollner.

“Preliminary experiments with zinc-telluride crystals already present that terahertz radiation is excellently suited to reply essential questions from materials science in a very new approach. We’re satisfied that this technique has a terrific future.”

Turning Air into Plasma

This electromagnetic wave is intense sufficient to tear electrons out of the molecules within the air. The air turns right into a glowing plasma. Then, the particular form of the wave’s electrical subject accelerates the electrons in such a approach that they produce the specified terahertz radiation.

“Our technique is extraordinarily environment friendly: 2.three% of the provided vitality is transformed into terahertz radiation — that’s orders of magnitude greater than will be achieved with different strategies. This ends in exceptionally excessive THz energies of virtually 200 µJ,” says Claudia Gollner. One other essential benefit of the brand new technique is very broad spectrum of terahertz radiation is generated. Very completely different wavelengths all through the terahertz vary are emitted concurrently. This produces extraordinarily intense quick radiation pulses. The bigger the spectrum of various terahertz wavelengths, the shorter and extra intense pulses will be generated.

Quite a few Doable Functions

“Because of this for the primary time a terahertz supply for very excessive depth radiation is now obtainable,” says Andrius Baltuska, the pinnacle of the analysis group on the Vienna College of Expertise. “Preliminary experiments with zinc-telluride crystals already present that terahertz radiation is excellently suited to reply essential questions from materials science in a very new approach. We’re satisfied that this technique has a terrific future.”

Reference: “Commentary of extraordinarily environment friendly terahertz era from mid-infrared two-color laser filaments” by Anastasios D. Koulouklidis, Claudia Gollner, Valentina Shumakova, Vladimir Yu. Fedorov, Audrius Pugžlys, Andrius Baltuška and Stelios Tzortzakis, 15 January 2020, Nature Communications.
DOI: 10.1038/s41467-019-14206-x

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