Next Generation of X-Ray Laser

Defense Fellow Building Next Generation of X-Ray Laser


April 16, 2010 - Dr. Margaret Murnane is a faculty member at the University of Colorado and a National Security Science and Engineering Faculty Fellow. She runs a joint research group with her husband, Dr. Henry Kapteyn, and credits their success to teamwork.

2010 is the 50th anniversary of the first demonstration of the laser — an advance that has transformed our lives in many wonderful ways. It is also a very special year for my husband Henry and me.

We met as graduate students together at Berkeley, studying in the same field and in the same group. Many people told us that we had no hope of ever getting faculty positions together because no university would ever hire two people in the same field. Fortunately, Washington State University (WSU) did. And, even better, they were fine with us working together.

At WSU, we developed the fastest lasers in the world at the time – under 10 femtoseconds (< 0.000000000000001 sec). We also figured out how to compress all the laser energy into a light pancake that was a few millimeters in diameter and only 3 microns thick! By comparison, a human hair averages 50 microns in diameter.

Teamwork was essential – we had a team of students with whom we celebrated our successes and supported each other. We worked faster and harder because we worked together.

Moving next to the University of Michigan and then to Colorado, we continued to run a joint group and benefit from many wonderful collaborations. Clearly, teamwork and openness to new ideas and other fields has helped us learn, brainstorm and overcome challenges.

This year, we are very excited because our team has finally figured out how to make a coherent or laser-like version of the x-ray tube in a small setup that eventually could be in widespread use. Like lasers, x-rays have transformed our lives by uncovering the double helix structure of DNA, helping doctors diagnose fractures and disease, and making air travel more secure. The images taken using x-ray tubes, however, are nowhere near as sharp as the wavelength of the x-rays. This is because x-ray tube technology is more like a bright x-ray flashlight or light bulb than a laser. Synchtrotron sources are another, brighter x-ray source useful for science, but housed in machines so large and expensive that their versatility is limited.



Margaret and Henry (center) meeting with high school and undergraduate students working in their laboratory during the summer. (Courtesy photo)

To generate coherent, laser-like beams of x-rays, we determined how to combine many ultra-fast laser photons together in a reasonably efficient way and generate coherent x-ray beams from a visible laser. Building an x-ray laser takes enormous power. Thus, it is easier to start with a visible laser and use nonlinear optics to upshift the laser light from the visible into the x-ray region.

To do this, we developed a new area of nonlinear optics of x-ray generation. So far, we have studied how the electron cloud in a chemical bond changes shape as a molecule breaks apart, measured how fast a magnetic material can flip orientation, followed how fast heat flows in a nanocircuit, and built a table-top microscope that does not need lenses.

How far can we go? It may be possible to generate bright beams of coherent hard x-rays and revolutionize crystallography, and biological, materials, and medical imaging. In theory, efficient conversion to very short wavelengths < 1 nm (corresponding to very high > 10keV photon energies) is possible, guaranteeing more exciting advances in lasers.

These achievements will require more of what we’ve benefited from all along: Partnerships and teamwork. From our start at WSU, I have learned that together we have a great chance to transform science.