Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Generating terahertz radiation from water makes 'the impossible, possible'

29.09.2017

Xi-Cheng Zhang has worked for nearly a decade to solve a scientific puzzle that many in the research community believed to be impossible: producing terahertz waves--a form of electromagnetic radiation in the far infrared frequency range--from liquid water.

Now, as reported in a paper published in Applied Physics Letters, researchers at the University of Rochester have "made the impossible, possible," says Zhang, the M. Parker Givens Professor of Optics. "Figuring out how to generate terahertz waves from liquid water is a fundamental breakthrough because water is such an important element in the human body and on Earth."


Researchers use lasers to generate terahertz pulses via interaction with a target. In this case, the target was an extremely thin water film -- approximately 200 microns or about the thickness of two pieces of paper -- created using water suspended between two aluminum wires.

Credit: University of Rochester photo / Kaia Williams

Terahertz waves have attracted increased attention recently because of their ability to nondestructively pass through solid objects, including those made of cloth, paper, wood, plastic, and ceramics, and produce images of the interiors of the objects.

Additionally, the energy of a terahertz photon is weaker than an x-ray photon. Unlike x-rays, terahertz waves are non-ionizing--they do not have enough energy to remove an electron from an atom--so they do not have the same harmful effects on human tissue and DNA.

Because of these abilities, terahertz waves have unique applications in imaging and spectroscopy--everything from discovering bombs in suspicious packages, to identifying murals hidden beneath coats of paint, to detecting tooth decay.

"Terahertz waves have a capacity to see through clothing, which is why you have these sub-terahertz body scanners at airports," Zhang says. "These waves can help to identify if an object is explosive, chemical, or biological, even if they can't tell exactly what the object is."

Zhang's research group uses lasers to generate terahertz pulses via interaction with a target. In this case, the target is an extremely thin film of water--approximately 200 microns or about the thickness of two pieces of paper--created using water suspended by surface tension between two aluminum wires. Researchers focus a laser into the water film, which acts as an emitter for the terahertz radiation output.

Previous researchers have generated terahertz waves from targets of solid crystals, metals, air plasma, and water vapor, but, until now, liquid water has proved elusive.

"Water was considered the enemy of terahertz waves because of water's strong absorption," Zhang says. "We always tried to avoid water, but it is a surprisingly efficient terahertz source."

In fact, when researchers measured the terahertz waves generated by the water, they found they were 1.8 times stronger than the terahertz waves generated from air plasma under comparable experimental conditions.

Because water is such a strong absorber, however, many people in the research community believed it would be impossible to use water as a target. Zhang himself has spent years attempting a solution, and he found a likewise stalwart in Qi Jin, now a PhD candidate in optics at Rochester, and the lead author on the paper.

"Almost everybody thought we wouldn't be able to get a signal from water," Jin says. "At first, I didn't believe it either."

One of the challenges was creating a film of water thin enough that the terahertz photons generated by the laser beam would not be absorbed, but thick enough to withstand the laser's energy.

Along with Yiwen E, a postdoctoral associate in Zhang's research group, Jin spent months optimizing the thickness of the water film and the incident angle, intensity, and pulse duration of the laser beam.

"We increased the thickness of the water a little bit, and gradually increased the laser, and just kept trying until we could make it work," Jin says. "Water is one of the richest resources on Earth, so it was really important for us to be able to generate these waves from water. There were many times I wanted to give up on this, but people in the lab kept encouraging me."

Zhang agrees: "I always tell my students and researchers here: if you try something, you might not get the result you wanted. But if you never try it, you definitely won't get it."

###

The research was sponsored by grants from the Army Research Office.

Media Contact

Lindsey Valich
lvalich@ur.rochester.edu
585-276-6264

 @UofR

http://www.rochester.edu 

Lindsey Valich | EurekAlert!

More articles from Physics and Astronomy:

nachricht What happens when we heat the atomic lattice of a magnet all of a sudden?
18.07.2018 | Forschungsverbund Berlin

nachricht Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Scientists uncover the role of a protein in production & survival of myelin-forming cells

19.07.2018 | Life Sciences

In the ocean's twilight zone, tiny organisms may have giant effect on Earth's carbon cycle

19.07.2018 | Earth Sciences

Lying in a foreign language is easier

19.07.2018 | Social Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>