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NSF Press Release


Embargoed until 2 p.m. ET
NSF PR 03-01 - January 2, 2003

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 Josh Chamot

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Breakthrough Brings Laser Light to New Regions of the Spectrum

Sterling Backus and Randy Bartels
Sterling Backus and Randy Bartels standing next to the femtosecond laser amplifier system.
Image courtesy of the University of Colorado and NSF.
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the waveguide
The waveguide as it appears within the femtosecond laser amplifier system.
Image courtesy of the University of Colorado and NSF.
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the waveguide
The waveguide researchers used to generate coherent EUV light. The center of the fiber is hollow, and gas flows into the fiber via tubes (the tubes were removed for the picture). The laser is focused through the hollow fiber, where it interacts with the gas to generate coherent EUV light. The modulations in the fiber are not visible in this picture.
Image courtesy of the University of Colorado and NSF.
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schematic of the waveguide
This picture shows a schematic of the waveguide, the modulated hollow-core fiber used to efficiently generate shorter wavelength EUV light. The wall of the hollow fiber is modulated - wavelike, with indentations 10-micrometers (µm) deep, periodically spaced every 0.5 mm (in the highest-intensity waveguide). The average inner diameter of the fiber is 150µm. By modulating the diameter of the fiber, the researchers modulate the intensity of the initial laser beam, and therefore also modulate the process that produces the EUV light. The researchers adjusted the period of the wavelike modulations to restrict the EUV emission to regions where the light waves will be in phase - this is how the researchers were able to generate shorter wavelength light more efficiently than was previously possible.
Image courtesy of the University of Colorado and NSF.
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femtosecond laser amplifier system
A state-of-the-art femtosecond laser amplifier system. Although the pulse energies from this laser are modest (on the order of millijoules), and the size is relatively small, the laser system crams all of the energy into a tiny, 20 femtosecond pulse. The result is a peak power close to a terawatt (a terawatt is roughly the continuous electrical generating capacity of the United States). The amplifier system allows the researchers to generate coherent EUV beams by focusing the laser into a hollow fiber called a waveguide. The green light in the picture comes from the pump lasers that are used to amplify the femtosecond pulses to the terawatt level.
Image courtesy of the University of Colorado and NSF.
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Combining concepts from electromagnetic radiation research and fiber optics, researchers have created an extreme-ultraviolet, laser-like beam capable of producing tightly-focused light in a region of the electromagnetic spectrum not previously accessible to scientists.

Between 10-100 times shorter than visible light waves, the extreme-ultraviolet (EUV) wavelengths will allow researchers to "see" tiny features and carve miniature patterns, with applications in such fields as microscopy, lithography and nanotechnology.

The achievement is based on a new structure called a "waveguide," a hollow glass tube with internal humps that coax light waves into traveling along at the same speed and help the waves reinforce each other.

Reported in the January 2 issue of the journal Nature, the work is part of a continuing project supported by the National Science Foundation (NSF), an independent agency of the U.S. Government that supports science and engineering research and education.

The new beam has peak powers approaching a megawatt and produces nanometer-scale light waves, yet the entire apparatus fits on a moderately sized table.

Expanding upon earlier work, a team of researchers led by Henry Kapteyn and Margaret Murnane of JILA at the University of Colorado create EUV beams by firing a femtosecond laser through the gas-filled waveguide. A femtosecond is one quadrillionth -- 1/1,000,000,000,000,000 -- of a second, and a brief pulse of the laser can be measured in these tiny units.

The intense laser light literally rips the gas atoms apart, resulting in charged ions and electrons. The laser beam then accelerates the electrons to very high energies and slams them back into the ions, releasing electromagnetic radiation (in this instance, photons at EUV wavelengths).

Some of the EUV waves can be out of phase with the laser, canceling each other and weakening the strength and coherence of the output beam. However, by creating ripples in the diameter of the waveguide, the Colorado team coaxed the light waves from the laser and EUV beams into traveling at the same speed (a result called "phase matching").

"These waveguide structures are amazingly simple - just a modulated, hollow glass tube," said Murnane. "It is as if the laser beam 'surfs' on the modulations and is slowed down - just as the speed bumps on the road slow a car down very simply and very effectively," she added.

Slowing down the laser allows it to travel at the same speed as the EUV light and increases the efficiency of the process. The result is a well-synchronized stream of photons firing out of the system -- electromagnetic radiation boosted up to a high-energy, extreme ultraviolet, wavelength.

Unlike some room-sized counterparts, "the new, laser-like, EUV source is smaller than any other EUV laser design at these very short wavelengths," said Kapteyn. "The waveguide fiber fits in one hand and the laser fits on a desktop," he added.

Moreover, the peak power of the beam is higher than any other light source at the wavelengths it achieves - all the way from the ultraviolet (UV) to the EUV region of the spectrum around 6 nanometers.

The Colorado group hopes to extend the beam's range into what scientists call the "water-window" -- the region of the spectrum below 4 nanometers where the light is perfect for imaging biological structures. Producing a beam in this region would allow the researchers to build a small microscope for imaging living tissues on a desktop or for viewing objects at the nanoscale.

"In 10 years, laser light will span all the way to the x-ray region of the spectrum," speculated Kapteyn. "The light will be used for the most precise microscopes that we can imagine, allowing real-time movies of the complex dance that atoms weave in chemical reactions and in pharmaceuticals yet to be visualized," he added.

The research was principally supported by NSF, with additional funds from the Department of Energy. JILA is managed by both the National Institute of Standards and Technology and the University of Colorado.

For additional information, please see:

"Laser-Like Beam May Break Barriers to Technological Progress," NSF Release,

"X-rays light up chemical reactions," PhysicsWeb, July 2001,

"Powerful Ultrafast Sources get Small," Laser Focus World, August 2001,

A profile of Margaret Murnane is available at:

A profile of Henry Kapteyn is available at:

JILA website:

For information on light and the electromagnetic spectrum, please see:



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