From U Nebraska – Lincoln: “1 billion suns: World’s brightest laser sparks new behavior in light”

University of Nebraska -Lincoln

6.26.17
Scott Schrage

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A rendering of how changes in an electron’s motion (bottom) alter the scattering of light (top), as measured in a new experiment that scattered more than 500 photons of light from a single electron. Previous experiments had managed to scatter no more than a few photons at a time. Donald Umstadter and Wenchao Yan

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Brighter than a billion suns: A scientist at work in the Extreme Light Laboratory. Diocles Laser.
University of Nebraska-Lincoln. COSMOS.

Physicists from the University of Nebraska-Lincoln are seeing an everyday phenomenon in a new light.

By focusing laser light to a brightness 1 billion times greater than the surface of the sun — the brightest light ever produced on Earth — the physicists have observed changes in a vision-enabling interaction between light and matter.

Those changes yielded unique X-ray pulses with the potential to generate extremely high-resolution imagery useful for medical, engineering, scientific and security purposes. The team’s findings, detailed June 26 in the journal Nature Photonics, should also help inform future experiments involving high-intensity lasers.

Donald Umstadter and colleagues at the university’s Extreme Light Laboratory fired their Diocles Laser at helium-suspended electrons to measure how the laser’s photons — considered both particles and waves of light — scattered from a single electron after striking it.

Under typical conditions, as when light from a bulb or the sun strikes a surface, that scattering phenomenon makes vision possible. But an electron — the negatively charged particle present in matter-forming atoms — normally scatters just one photon of light at a time. And the average electron rarely enjoys even that privilege, Umstadter said, getting struck only once every four months or so.

Though previous laser-based experiments had scattered a few photons from the same electron, Umstadter’s team managed to scatter nearly 1,000 photons at a time. At the ultra-high intensities produced by the laser, both the photons and electron behaved much differently than usual.

“When we have this unimaginably bright light, it turns out that the scattering — this fundamental thing that makes everything visible — fundamentally changes in nature,” said Umstadter, the Leland and Dorothy Olson Professor of Physics and Astronomy.

A photon from standard light will typically scatter at the same angle and energy it featured before striking the electron, regardless of how bright its light might be. Yet Umstadter’s team found that, above a certain threshold, the laser’s brightness altered the angle, shape and wavelength of that scattered light.

“So it’s as if things appear differently as you turn up the brightness of the light, which is not something you normally would experience,” Umstadter said. “(An object) normally becomes brighter, but otherwise, it looks just like it did with a lower light level. But here, the light is changing (the object’s) appearance. The light’s coming off at different angles, with different colors, depending on how bright it is.”

That phenomenon stemmed partly from a change in the electron, which abandoned its usual up-and-down motion in favor of a figure-8 flight pattern. As it would under normal conditions, the electron also ejected its own photon, which was jarred loose by the energy of the incoming photons. But the researchers found that the ejected photon absorbed the collective energy of all the scattered photons, granting it the energy and wavelength of an X-ray.

The unique properties of that X-ray might be applied in multiple ways, Umstadter said. Its extreme but narrow range of energy, combined with its extraordinarily short duration, could help generate three-dimensional images on the nanoscopic scale while reducing the dose necessary to produce them.

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Using a laser focused to the brightest intensity yet recorded, physicists at the Extreme Light Laboratory produced unique X-ray pulses with greater energy than their conventional counterparts. The team demonstrated these X-rays by imaging the circuitry of a USB drive. Extreme Light Laboratory | University of Nebraska-Lincoln.

Those qualities might qualify it to hunt for tumors or microfractures that elude conventional X-rays, map the molecular landscapes of nanoscopic materials now finding their way into semiconductor technology, or detect increasingly sophisticated threats at security checkpoints. Atomic and molecular physicists could also employ the X-ray as a form of ultrafast camera to capture snapshots of electron motion or chemical reactions.

As physicists themselves, Umstadter and his colleagues also expressed excitement for the scientific implications of their experiment. By establishing a relationship between the laser’s brightness and the properties of its scattered light, the team confirmed a recently proposed method for measuring a laser’s peak intensity. The study also supported several longstanding hypotheses that technological limitations had kept physicists from directly testing.

“There were many theories, for many years, that had never been tested in the lab, because we never had a bright-enough light source to actually do the experiment,” Umstadter said. “There were various predictions for what would happen, and we have confirmed some of those predictions.

“It’s all part of what we call electrodynamics. There are textbooks on classical electrodynamics that all physicists learn. So this, in a sense, was really a textbook experiment.”

Umstadter authored the study with Sudeep Banerjee and Shouyuan Chen, research associate professors of physics and astronomy; Grigory Golovin and Cheng Liu, senior research associates in physics and astronomy; Wenchao Yan, Ping Zhang, Baozhen Zhao and Jun Zhang, postdoctoral researchers in physics and astronomy; Colton Fruhling and Daniel Haden, doctoral students in physics and astronomy; along with Min Chen and Ji Luo of Shanghai Jiao Tong University.

The team received support from the Air Force Office for Scientific Research, the National Science Foundation, the U.S. Department of Energy’s Office of Science, the Department of Homeland Security’s Domestic Nuclear Detection Office, and the National Science Foundation of China.

See the full article here .

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The University of Nebraska–Lincoln, often referred to as Nebraska, UNL or NU, is a public research university in the city of Lincoln, in the state of Nebraska in the Midwestern United States. It is the state’s oldest university, and the largest in the University of Nebraska system.

The state legislature chartered the university in 1869 as a land-grant university under the 1862 Morrill Act, two years after Nebraska’s statehood into the United States. Around the turn of the 20th century, the university began to expand significantly, hiring professors from eastern schools to teach in the newly organized professional colleges while also producing groundbreaking research in agricultural sciences. The “Nebraska method” of ecological study developed here during this time pioneered grassland ecology and laid the foundation for research in theoretical ecology for the rest of the 20th century. The university is organized into eight colleges on two campuses in Lincoln with over 100 classroom buildings and research facilities.

Its athletic program, called the Cornhuskers, is a member of the Big Ten Conference. The Nebraska football team has won 46 conference championships, and since 1970, five national championships. The women’s volleyball team has won four national championships along with eight other appearances in the Final Four. The Husker football team plays its home games at Memorial Stadium, selling out every game since 1962. The stadium’s capacity is about 92,000 people, larger than the population of Nebraska’s third-largest city.

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