{"id":47,"date":"2020-04-28T19:48:27","date_gmt":"2020-04-28T19:48:27","guid":{"rendered":"https:\/\/magazine.hmc.edu\/spring-2020\/?p=4"},"modified":"2020-05-08T23:59:50","modified_gmt":"2020-05-08T23:59:50","slug":"laser-focused","status":"publish","type":"post","link":"https:\/\/magazine.hmc.edu\/spring-2020\/laser-focused\/","title":{"rendered":"Laser-Focused"},"content":{"rendered":"

Henry Kapteyn ’83 can’t recall whether it was<\/strong> John Townsend or Tom Helliwell\u2014Harvey Mudd physics professors\u2014who originally introduced him to the topic of X-ray lasers, but he clearly remembers the discussion about the challenges of generating the enormous power to make them. \u201cWith the basic physics of a laser, you\u2019d need about a billion times more power to make an X-ray laser than you\u2019d need to make a laser pointer,\u201d Kapteyn explains. \u201cIt was a very interesting problem.\u201d It was also one he didn\u2019t forget.<\/p>\n

Now 37 years later, Kapteyn has become one of the field\u2019s foremost researchers, greatly expanding the understanding of ultra-fast laser science and its potential for high-resolution medical and other imaging, as well as next-generation microelectronics.<\/p>\n

Solved it!<\/h2>\n

After earning physics B.S. and M.S. degrees from HMC and Princeton University, respectively, Kapteyn became a doctoral student in the University of California-Berkeley\u2019s physics department and began pursuing the power puzzle at Lawrence Livermore National Laboratory. While some scientists at Livermore were mulling over the idea of exploding a nuclear bomb to get the power to make an X-ray laser, Kapteyn hoped to find a more widely accessible method. He took a big step toward that goal by generating laser pulses in the ultraviolet region of the spectrum\u2014and without any explosions required. It was quite an achievement, but he still sought to design lasers at the evens-horter wavelengths of the X-ray region.<\/p>\n

\"Margaret
Margaret Murnane and Henry Kapteyn ’83<\/figcaption><\/figure>\n

Also while at Berkeley, Kapteyn met fellow doctoral student Margaret Murnane, who would become both his wife and his research partner. Once the pair earned their PhD degrees, they took shared-lab faculty positions first at Washington State University and then at the University of Michigan, before finally settling at the University of Colorado and its renowned JILA institute in 1999. Along the way, they succeeded in solving the central power problem plaguing X-ray laser development.<\/p>\n

\u201cWhat happened is we used a different set of physics to get around the fundamental difficulties of making an X-ray laser, and we did that by converting light at the visible wavelength to very short wavelengths,\u201d Kapteyn says. The process involved producing super-short pulses of visible light\u2014just 10 femtoseconds (10-14 seconds) in duration\u2014which greatly concentrated the energy of light and generated the high level of power needed to create a focused beam of photons at X-ray frequencies. By \u201ctransmuting\u201d laser light from the visible to the X-ray region of the spectrum, it was possible to retain the focused, directional nature of this laser, creating coherent X-ray laser light.<\/p>\n

Not only did Kapteyn and Murnane produce X-ray laser light, but they did it on a device that can fit in a typical research lab. \u201cThis made it a lot more practical,\u201d he says, \u201cbecause it\u2019s something that runs on your tabletop to generate coherent X-rays as opposed to where this field started, which was a single-shot experiment where your power comes from a nuclear detonation!\u201d<\/p>\n

The upshot<\/h2>\n

Since that first discussion about X-ray lasers in his undergraduate days, Kapteyn\u2019s interest has also extended to the myriad potential uses for this technology. To that end, he and Murnane started a company, KMLabs, shortly after they left Berkeley so they could explore the possible uses of ultrafast lasers. Today, the company offers a product line of laser systems capable of delivering femtosecond and attosecond (10-18) pulses of X-ray and ultraviolet light for a broad range of applications.<\/p>\n

One area of great interest is in imaging, where shorter wavelengths correspond to increased resolution. Kapteyn envisions medical doctors and researchers using this technology to view exceedingly fine details of the brain or other organs. In addition, the couple\u2019s group has also been able to string together successive rapid-fire snapshots to create videos, and \u201cwe made the first actual nanoscale movie just a year or two ago,\u201d he says. Such a capability would yield insight into neuronal activity and other biological processes occurring in real time.<\/p>\n

In addition, X-ray laser imaging has great potential in the microelectronics industry, which is always seeking smaller and faster chips. \u201cWhen you\u2019re on an engineering path, which is very much the description of microelectronics, people keep pushing evolutionary improvements without really looking at the underlying physics of what\u2019s happening. There\u2019s a lot that\u2019s unknown and that has to work better to have a big impact.\u201d Kapteyn says. This is where coherent X-ray lasers come in.<\/p>\n

For instance, KMLabs is helping with a major issue that has arisen since manufacturers have begun using an advanced etching technique called extreme ultraviolet (EUV) or soft X-ray lithography to make new, cutting-edge chips. The technique relies in part on light-sensitive material, called photoresist, to help print the often molecule-sized microscopic circuitry onto chips, but there\u2019s a hitch. The photoresist isn\u2019t behaving as expected, so the chip details aren\u2019t printing cleanly, Kapteyn says. At the request of a nonprofit consortium that serves the semiconductor industry, KMLabs is building an X-ray laser system to peer into light-matter interaction in the photoresists and figure out what\u2019s going on.<\/p>\n

These are just a few of the possibilities for ultrafast laser technology, he says. \u201cAn X-ray laser isn\u2019t something that will be in everybody\u2019s house, but the products that are enabled by that technology could end up being in everybody\u2019s pocket as the next-generation smart phone.\u201d<\/p>\n

Looking back and forward<\/h2>\n

Kapteyn has seen amazing progress over his career, but he still sees much to do.<\/p>\n

\u201cWe\u2019re now doing things that we wouldn\u2019t have dreamed were possible when I was a grad student or when I was an undergrad at Harvey Mudd, and I feel very fortunate that a lot of what I envisioned I wanted to do with my life is getting there,\u201d he said. \u201cScientists tend to work until they drop, and I don\u2019t see us running out of things to do. There are a lot of exciting new directions ahead for us.\u201d<\/p>\n

__________<\/p>\n

Married to the Research \u2026 and the Researcher<\/h3>\n

Married research partners are few and far between in the sciences, but Henry Kapteyn wouldn\u2019t have it any other way. He and his wife, Margaret Murnane, have been sharing a lab since 1990.<\/p>\n

Their joint accomplishments haven\u2019t escaped notice. In addition to the Arthur L. Schawlow Prize in Laser Science, one of the highest honors awarded by the American Physical Society, they were named co-recipients of the prestigious Benjamin Franklin Medal in Physics. The last time the Franklin Medal went to a married couple for physics accomplishments was in 1909, and it went to none other than celebrated physicists Pierre and Marie Curie. Kapteyn remarked, \u201cIt\u2019s a big thrill.\u201d<\/p>\n

The key to working together for Kapteyn and Murnane has been communication, even when\u2014and sometimes especially when\u2014they don\u2019t see eye to eye, he says. \u201cWe bounce ideas off each other all the time, and I think a big part of my success
\nis having someone I can truly be open with and trusting with.\u201d He adds, \u201cYou get an information transfer that really accelerates the thinking process and puts you on the right track a lot faster.\u201d<\/p>\n

\n

UPDATE | March 27, 2020<\/h2>\n

\u201cMargaret and I have been isolating ourselves for nearly two weeks now\u2014but videoconferencing means we\u2019re still working hard. And also cleaning the house and gardening, to keep sane. Our labs are shut down for the time being. But we\u2019re fortunate otherwise\u2014a few colleagues who have had mild symptoms of COVID, but weren\u2019t tested, are recovering well. The Franklin Institute award gala has been postponed until an indefinite time in the fall, as would be expected.\u201d<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

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