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 Tangled magnetic fields power cosmic particle accelerators
14.12.2018 | DOE/SLAC National Accelerator Laboratory

nachricht In search of missing worlds, Hubble finds a fast evaporating exoplanet
14.12.2018 | NASA/Goddard Space Flight Center

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: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Data use draining your battery? Tiny device to speed up memory while also saving power

14.12.2018 | Power and Electrical Engineering

Tangled magnetic fields power cosmic particle accelerators

14.12.2018 | Physics and Astronomy

In search of missing worlds, Hubble finds a fast evaporating exoplanet

14.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>