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 – one that produces extreme ultraviolet light at unprecedented energies and pulse rates for studies of complex materials – into a commercial product.
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.
And the scientists involved say they’re glad to have played a role in shepherding the technology through the “Valley of Death” – the treacherous passage from research project to commercial product where many promising technologies, and the companies that develop them, stumble and fail. Bridging that gap so the fruits of basic research can spread into the wider society is an important part of the DOE mission.
“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.”
A Three-stage Energy Boost
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 trillionths of a second (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. The researchers described the new tabletop laser and its integration into the ARPES setup in a recent cover article in Review of Scientific Instruments.
A Long Road to Success
The roots of the Lumeras laser system go back to about 2000, when company founder Andrew Merriam was a graduate student at Stanford. For his doctoral research, he did proof-of-principle experiments on an early version of a nonlinear system based on ultraviolet lasers. It was in no way ready for commercialization, he says.
His PhD complete, Merriam joined a small laser research and development company in Scotts Valley. There he continued to pursue the idea and went looking for funding to develop it. He approached Shen, who had been on his thesis committee and was familiar with the concept.
Shen agreed to write a letter of recommendation in support of the company’s application for a Small Business Innovation Research (SBIR) grant from the National Science Foundation. A six-month Phase 1 grant was approved, and Merriam began work on a fresh approach using a completely different laser technology to shift the properties of the laser beam to more desirable energies.
It was a flop.
“Ultimately the original Phase 1 effort just collapsed and failed,” Merriam said. “It was then I founded Lumeras in order to work full-time to develop this technology. My wife and I put up the seed capital for optics, materials and equipment, and we rented a small commercial space in Santa Cruz. With the help of Mike Jefferson, a retired physicist from IBM, we re-did the Phase 1 work from a new direction. And this time it worked.”
Based on that success, the company was awarded a two-year Phase 2 SBIR grant, bringing its total NSF funding to about $750,000 over three years. “The NSF award gave us the resources to develop and apply advanced laser techniques,” Merriam said. “Only then were we able to break into 21st century laser technology.”
Exploring the Full Range of Electron Behavior
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. And in April Lumeras delivered a second laser system to a SIMES laboratory at SLAC.
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; like today’s LCLS, it will be a DOE Office of Science User Facility.
In addition to funding from NSF and Lumeras, the ARPES studies and commissioning of the new laser system were supported by Stanford and the DOE Office of Science.