Long before “laser focus” became a cliché, physicists Henry Kapteyn and Margaret Murnane were laser-focused. During the last 35 years, Kapteyn and Murnane have been close partners in laser research and in life. Together they are happy to work long hours, especially if they are on the verge of a breakthrough, and to talk physics (nearly) all the time. Kapteyn and Murnane credit their intense teamwork, with each other and with colleagues, for the remarkable breakthroughs they’ve made in lasers and light. Today the Kapteyn-Murnane Group at the University of Colorado at Boulder are leaders in the thriving field of coherent ultra-fast x-ray laser light sources. Their groundbreaking research on laser light, published in more than 250 research papers, has impacted virtually every area of science, from biology to astronomy, lighting the way for numerous applications such as high-resolution imaging of objects as small as viruses, making and breaking chemical bonds, lensless imaging, and energy-efficient electronics. They have even succeeded in shrinking down high-intensity x-ray lasers so they can now fit on tabletops, which makes them more accessible and more affordable for a wider breadth of labs across the globe.
Henry Kapteyn and Margaret Murnane say that laser light is pure, controlled energy. It brought them together and has driven their tightly-focused creativity ever since. They met 35 years ago in a University of California, Berkeley graduate-level class on what was then a new technology: ultra-fast laser and x-ray light sources. From that beginning, Team Kapteyn and Murnane would become a major driving force in the development of ultra-fast laser and x-ray light sources, discovering new approaches and pushing existing methods in new directions. The relentless pace of their research is legendary in optical science, including the time that Murnane and Kapteyn conceived a novel application, collected data, and wrote a paper on it, all within a week. Now as professors of physics at the University of Colorado at Boulder, Murnane and Kapteyn are still pushing the limits of light.
Their lives followed parallel paths on separate continents. Murnane grew up in rural Ireland where, apart from schoolteachers, she didn’t know anyone who had gone to university, but her father brought home science books, math puzzles, and, one time, an encyclopedia. There she read of Archimedes and his “Eureka” moment in a bathtub when he realized he could measure the gold in a king’s crown by water displacement. In search of her own “Eureka” moments, Murnane earned a B.S. and M.S. in physics at University College Cork. She came to the United States in 1983 to earn her doctorate at Berkeley.
Kapteyn was born in Chicago’s suburbs, and his parents, post-World War II immigrants from the Netherlands, stoked his early interest in science. One of his earliest memories is being four years old and, outfitted in safety goggles, climbing a lab bench to ignite a Bunsen burner in a special Saturday science class. Kapteyn earned his B.S. at Harvey Mudd College in California and went for his M.S. at Princeton University, both in physics. But Kapteyn found that he missed California and transferred west for a physics doctoral program at Berkeley. There he discovered lasers and Margaret Murnane.
They clicked, first in science and then with each other, in the lab of newly-appointed physics professor, Roger Falcone. For his thesis, Kapteyn built a practical-sized laser that could produce x-ray wavelengths, which are more powerful than visible light. For hers, Murnane designed a high-power, fast-pulse laser that shortened the duration of the pulse to about 100 femtoseconds, or 100 quadrillionths of a second, quick enough to freeze natural processes like chemical bonding. Still, from the beginning, Murnane and Kapteyn were inseparable in the lab. In 1988, between discoveries, they married.
After graduation, they took their first faculty positions at Washington State University in 1990. Despite warnings from colleagues to keep an intellectual distance from each other, they set up a joint laser lab. The Kapteyn-Murnane Group soon reached its first “Eureka” moment. To have a fast laser, you need multiple wavelengths of light, but different wavelengths move at different speeds, tearing apart the light pulse. They realized that they could use the right kind of prisms to keep different wavelengths moving at the same speed. Their new device produced high-power, eight-femtosecond pulses, and was easy to use. News of their new process spread among colleagues at the speed of light, and soon Kapteyn and Murnane were distributing a do-it-yourself paper manual. “That manual went viral before ‘viral’ was really a word,” Kapteyn likes to joke.
In 1996, the Kapteyn-Murnane Group relocated to the University of Michigan. In Ann Arbor, they focused on further development of “high-order harmonic generation” (HHG), a process discovered by physicists in 1987, in which a femtosecond laser could be focused into a noble gas to convert it into ultraviolet wavelengths, edging it towards the more powerful x-ray wavelengths. Murnane and Kapteyn wanted to combine their ultrafast pulse lasers with the HHG process to create very fast bursts of x-rays in directed beams—just like a laser. Two years later, they had another “Eureka” moment with their student, Andy Rundquist, when in the small hours of the night, they were able to force laser light and x-ray light to travel at the same speed through a gas-filled fiber. Refinements to this method set the stage for their tabletop x-ray laser.
In 1999, Kapteyn and Murnane moved again, this time to the University of Colorado at Boulder. In 2012, they achieved true x-ray light with a tabletop laser that can capture unimaginably fast chemical processes. They say that this tightly focused, ultra-fast x-ray technology has broad scientific, medical, and industrial uses, and its small size and lower price tag mean it is accessible to a wider variety of users than ever before. The pair is pursuing distribution of this new technology through a commercial spinoff company, KMLabs.
Together, Murnane and Kapteyn have been showered with honors including the 2019 Colorado Governor's Award for High Impact Research, the 2017 Optical Society of America’s Frederic Ives Medal/Jarus W. Quinn Prize, the 2012 Willis Lamb Award for Laser Science and Quantum Optics, the 2010 Optical Society of America’s R.W. Wood Prize, the 2010 American Physical Society’s Arthur L Schawlow Prize in Laser Science, and the 2009 American Chemical Society’s Ahmed Zewail Award. Separately, Murnane was awarded a John D. and Catherine T. MacArthur Fellowship (the so-called “genius grant”) in 2000. Kapteyn won the Optical Society of America’s Adolph Lomb Medal in 1993. They are both elected members of the National Academy of Sciences, and fellows of the American Association for the Advancement of Science, the American Physical Society, the Optical Society of America, and the American Academy of Arts and Sciences.
Kapteyn admits that as a couple, they are not very good at separating work and home. Over dinner or hiking in the Rocky Mountain National Park, physics is often the conversational focus. Yet their dedication is incredibly effective. In June 2019, their lab made news, yet again, for being the first to create a “vortex beam” of light, which can capture extremely fast processes and even move and trap tiny objects. This work benefitted from a long-term collaboration with the University of Salamanca in Spain. Their advice for young scientists: don’t try to do it all by yourself—collaboration is crucial.
Information as of March 2020