Bright light

[Image: Getty Images]

On 14 December, several dozen leading laser scientists and others drew together for a conference at the Keck Building of the U.S. National Academies of Science, Engineering, and Medicine (NAS) in Washington, D.C. At issue was the status and future of ultrafast, high-intensity lasers in the United States, particularly in light of large projects in other countries such as the European Extreme Light Infrastructure (ELI).

Philip Bucksbaum of the SLAC National Accelerator Laboratory (who also served as the 2014 President of The Optical Society) described the petawatt-class, femtosecond lasers under discussion at NAS as producing “the brightest light on Earth.” And those high-intensity, ultrafast light pulses hold the promise, according to the meeting’s conveners, both of driving both some exotic, otherwise inaccessible new science, and of empowering applications in manufacturing, biomedicine and elsewhere.

A key take-home message of the meeting, though, was that the U.S. science and engineering community has some work to do to re-establish the dominant position it once held in this technology.

New NAS report

Opportunities report cover

[Image: National Academies Press]

The occasion for the NAS panel, convened by the Academies and the National Photonics Initiative (NPI), was a briefing on a new NAS report, Opportunities in Intense Ultrafast Lasers: Reaching for the Brightest Light. The report—authored by an NAS committee chaired by Bucksbaum and including 14 senior scientists and others from academia, government and industry—assessed the status of high-intensity science both in the United States and abroad, laying out a case for a more focused U.S. program.

The report’s authors wanted to determine, according to Bucksbaum, whether there was “a roadmap that we could recommend for the U.S. to follow.” Three U.S. agencies active in photonics funding, the Department of Energy (DOE), the Office of Naval Research, and the Air Force Office of Scientific Research, co-sponsored the report.

In brief remarks opening the meeting, Elizabeth Rogan, the CEO of The Optical Society, drew comparisons between the new NAS study and the Academy’s seminal 2012 report Optics and Photonics: Essential Technologies for Our Nation. Among other things, that report spurred the formation of the NPI itself, an academic-industry-government coalition led by several scientific societies that has had some success in raising the profile of photonics in the United States. (In addition to OSA, NPI’s founding members include SPIE, APS, LIA, and the IEEE Photonics Society.) Said Rogan: “There’s an opportunity here—we’ve got the talent, we’ve got the infrastructure—to take advantage of those assets to push the U.S. into a leading role” in high-intensity lasers in the future.

The pluses: Historic leadership, exotic science

Increasing intensity with time

Early U.S. leadership in enabling technologies such as chirped-pulse amplification (CPA) allowed laser intensities to grow dramatically since the 1990s. [Image: Philip Bucksbaum/National Academies Press]

Looking at the scene today, however, the authors of the Opportunities report found a mixed bag for intense ultrafast lasers in the United States. On the plus side, the report recognizes the U.S. role in pioneering the technology beginning in the 1990s, when the country was “the leading innovator and dominant user.”

The study also stresses the importance of petawatt-peak-power lasers both for basic science (in areas ranging from the attosecond-timescale movement of electrons to particle physics to astrophysical simulations of giant planets) and for applications in materials processing, nuclear-stockpile stewardship and biomedicine. One of the panelists, Thomas Katsouleas of the University of Virginia (who was not one of the authors of the NAS report), cited the memorable example of “boiling the vacuum”—the ability, given energy delivered at high enough intensity, to “tear apart the vacuum itself,” and create conditions akin to those in some models of an expanding universe.

“The science,” Katsouleas argued, “is promising.” And, Bucksbaum added, “this is not just a single science opportunity,” pointing to the proliferation of research papers across a swath of scientific disciplines taking advantage of these lasers as their intensity has increased geometrically over time.

The downside: “Lost dominance”

PW laser distribution

A map in the Opportunities report, showing the current distribution of petawatt-class lasers, shows concentrations in Europe and Asia. [Image: Courtesy of J.L. Collier/National Academies]

Yet a persistent theme of both the panel discussion and the Opportunities report is that the United States has “lost its previous dominance” in ultrafast technology, ceding it in particular to Europe (as seen in projects such as the ELI) and Asia. “At present,” the report notes, “80 to 90 percent of the high-intensity laser systems are overseas, and all of the highest power (multi-petawatt) research lasers currently in construction or already built are overseas.”

Peter Moulton of the Lincoln Laboratory, Massachusetts Institute of Technology, drove the point home with a review of the technical history of these lasers. Moulton noted that the early ingredients that led to the first petawatt laser in 1998—especially the key enabling technology of chirped-pulse amplification, developed in 1985 by Donna Strickland and Gérard Mourou—were thoroughly American-born. Yet despite those technical roots, the U.S. position in petawatt-class lasers has eroded as other societies have taken a greater interest.

That’s not for a lack of talent in the United States, according to Moulton, who cited the example of the HAPLS laser recently designed and built by the Lawerence Livermore National Laboratory and installed at the ELI Beamlines facility near Prague, Czechoslovakia. (See “High-average-power ultrafast lasers,” OPN, October 2017.) “We had an early lead, we developed the technology,” Moulton said. “And then we started shipping it overseas.”

Diagnosis and prescription

HAPLS laser shot

The High-repetition-rate Advanced Petawatt Laser System (HAPLS), built by Lawrence Livermore National Laboratory for the Extreme Light Infrastructure facility in the Czech Republic. [Courtesy of LLNL]

The Opportunities report lays the blame for the eroded U.S. position most pointedly on issues of coordination and community. In the United States, it concludes, the research community in ultrafast, high-intensity lasers, while “large and talented,” is also fragmented, with little industry–government coordination and with no “cross-agency stewardship” unifying government sponsorship of this technology. That contrasts markedly, according to the report’s authors, with the much more coordinated approach seen in Europe. As a result, said Bucksbaum, “right now the Europeans are certainly winning the infrastructure race.”

The report also offers a prescription for re-establishing a strong U.S. position in petawatt lasers. In particular, it recommends creation of a “broad national network” of academic, industry and government labs, with an active effort at integration and coordination led by federal research agencies. It also calls for the forging of a “comprehensive interagency national strategy” that would encompass development of both large-scale and midscale projects, as well as greasing the skids for technology transfer to private-sector applications. And the report advocates the creation of “at least one large-scale open access high-intensity laser facility,” co-located with an existing national lab, and programs to help “retain and renew” the U.S. talent base in high-intensity lasers.

Building the case

The opportunities (and challenges) for making such a vision reality were the focus of a bracing final talk by Patricia Dehmer, the retired deputy director for science programs at the DOE Office of Science. Building the case for a sustained government commitment requires “a few things—the case has to be compelling, exciting, unassailable and widely supported,” said Dehmer. “And it would help if you got a little help from your friends” outside of the government sphere.

The new NAS report, Dehmer suggested, is a good starting point, but researchers with a stake in high-intensity science will need to go much further to make a compelling case. And that, in turn, will require the currently fragmented U.S. ultrafast community to “come together in common cause.”

Dehmer noted the political and policy dimensions today that underscore the need for this kind of community-driven action. “In normal times in the United States, the Office of Science and Technology Policy [OSTP] does this” kind of coordination, serving as a nexus across federal agencies. But with OSTP still in a state of flux one year into the Trump administration, “communities, professional societies and other groups are forced to take over and do this,” she said.

That kind of community cohesiveness, Dehmer and the other panelists agreed, is a necessary first condition of making the case for a renewed effort in high-intensity lasers in the United States. What government and the public like to support, said Bucksbaum, is “a clean, unified vision of an exciting future outcome. That comes from a community that has a stake in that outcome.”

“If the science community is excited about something, even LIGO can happen,” said Bucksbaum. “And, in fact, it did.”

Meeting participants

Participants in the NAS meeting included David Lang, NAS; Elizabeth Rogan, OSA; Eugene Arthurs, SPIE; Roger Falcone, University of California, Berkeley; Patricia Dehmer, U.S. Dept. of Energy (ret.); Philip Bucksbaum, Stanford University/SLAC; Peter Moulton, MIT; and Thomas Katsouleas, University of Virignia. [Courtesy of Rebecca Andersen]