Tabletop-Laser for Extreme Ultraviolet Light

Lumeras founder Andrew Merriam, left, and SLAC/Stanford Professor Zhi-Xun Shen with a tabletop laser the company developed and installed in a laboratory run by SIMES, the Stanford Institute for Materials and Energy Sciences. Shen’s group collaborated with the startup to help turn the novel laser into a commercial product (Source: SLAC)

Lumeras founder Andrew Merriam, left, and Stanford Professor Zhi-Xun Shen with a tabletop laser the company developed and installed in a laboratory run by SIMES, the Stanford Institute for Materials and Energy Sciences (Source: SLAC)

Scientists at Stanford University and the Depart­ment of Energy’s SLAC National Acce­lerator Labora­tory have colla­borated with a local startup company to turn a novel tabletop laser into a commer­cial product. The new device produces extreme ultraviolet light at unpre­cedented energies and pulse rates for studies of complex materials. Now two of the laser systems are operating in labs run by SIMES, the Stanford Institute for Materials and Energy Sciences at SLAC. The startup, Santa Cruz-based Lumeras LLC, is selling the systems to research labs around the world.

“In a way this is a classic startup scenario,” said Zhi-Xun Shen, a SIMES investigator and professor at SLAC and Stanford who helped the company get development funding and integrate the laser into advanced materials research. “Researchers in our group were the first users of the laser system, and we helped nurture this company through the Valley of Death. Now they’re growing and hiring, and we’re getting amazing research results.”

The new laser system is based on the principle of nonlinear optical frequency conversion, in which light passing through certain materials is shifted to shorter wave­lengths and higher energies. Discovered decades ago, it’s routinely used to boost pulses of laser light to energy ranges that can’t be achieved with laser techno­logy alone. In this case, researchers shifted the energy of infrared laser light in three stages by shining it through two crystals and a cloud of xenon gas. They wound up with a beam of extreme ultra­violet light with a photon energy of 11 electron­volts – nearly double the energy of previous systems. What’s more important, the laser’s pulses, just pico­seconds long and arriving 10 million times per second, can be used to study the energy spectrum of advanced materials, which governs their properties, at extremely high resolution.

In the SIMES labs, these extreme ultra­violet beams feed into ARPES, or angle-resolved photo­emission spectro­scopy, a powerful tool for examining the electronic and magnetic behavior of materials used in energy-efficient elec­tronics and information storage. Shen’s group has been instru­mental in deve­loping ARPES and using it to inves­tigate complex materials such as super­conductors, which conduct electricity with zero loss, and topo­logical insulators, which carry electrical current on their surfaces but not through their interiors. These materials could eventually have profound impacts on society by allowing power lines to transmit elec­tricity with 100 percent efficiency, for instance.

As the techno­logy developed, Shen agreed to buy the company’s first laser system for his lab on the main Stanford campus. That first purchase agreement was critical, enabling Merriam to tweak the laser into its final operating configuration. Meanwhile, his staff worked closely with SIMES researchers to integrate the laser system into the ARPES setup, where it’s already been used to study a range of materials, including super­conductors and semi­conductors. Shen says the system’s combi­nation of high reso­lution, high pulse rate and high bright­ness allows researchers to explore the entire range of electron behaviors that give materials their properties. For example, it offers a totally new way to probe electron spins, which give rise to magnetism, and has potential for increasing the sensitivity of mass spectro­metry, which is used for chemical analysis and environ­mental moni­toring.

When further developed, he added, this laser also has the potential to explore and optimize conditions for in-depth expe­riments at LCLS II – a major upgrade of SLAC’s Linac Coherent Light Source X-ray free-electron laser that is now underway. The upgrade will add a second X-ray laser beam that’s 10,000 times brighter, on average, than the current one and fires 8,000 times faster, up to a million pulses per second, for expe­riments that sharpen our view of how nature works on the atomic level and on ultra­fast time­scales. Pre­liminary work with instru­ments like the new table­top laser could help scientists make the most of their limited time at LCLS-II so they can take full advantage of what it has to offer. (Source: SLAC)

Reference: Y. He et al.: High resolution angle resolved photoemission with tabletop 11 eV laser, Rev. Sci. Instrum. 87, 011301 (2016); DOI: 10.1063/1.4939759

Links: Lumeras LLC, Santa Cruz, California, USA • SIMES, SLAC National Accelerator Laboratory, Menlo Park, California, USA

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