Researchers Produce First Table-Top Laser-Like Beam Simultaneously Streaming X-Ray Wavelengths
Researchers affiliated with the Engineering Research Center for Extreme Ultraviolet Science and Technology (ERC EUV), an NSF-funded ERC headquartered at Colorado State University, have for the first time produced a laser-like, directed beam of light that simultaneously streams ultraviolet light, X-rays, and all wavelengths in between. This new technology is also the first to do so using a setup that fits on a laboratory table.
This work opens possibilities to probe the shortest natural-world space and time scales. The X-ray burst that emerges has short wavelengths, which will make it possible to follow the tiniest, fastest physical processes in nature, including the coupled dance of electrons and ions in molecules as they undergo chemical reactions or the flow of charges and spins in materials (see figure).
In the 1960s scientists believed that shorter-wavelength lasers (i.e., in the X-ray region below visible light) could someday be developed. In the 1980s scientists worked on a powerful X-ray laser device that could be launched into space and use a nuclear blast to fire beams at attacking Soviet nuclear-armed ballistic missiles. However, more recent interest in X-ray lasers has focused on their abilities to image extremely small objects because of their short wavelengths. Dr. Deborah Jackson, the NSF program officer who oversees the ERC EUV's grant, summed it up as follows: “Thirty years ago, people were saying we could make a coherent X-ray source, but it would have to be an X-ray laser, and we'd need an atomic bomb as the energy source to pump it. Now, we have these guys who understand the science fundamentals well enough to introduce new tricks for efficiently extracting energetic photons, pulling them out at X-ray wavelengths ... and it's all done on a table-top!"
By focusing intense pulses of infrared light—each just a few optical cycles in duration—into a high-pressure gas cell, the researchers converted part of the original laser energy into a coherent super-continuum of light that extends well into the X-ray region of the spectrum. "This is the broadest spectral, coherent-light source ever generated," said engineering and physics professor Henry Kapteyn, at the University of Colorado at Boulder (an ERC EUV partner institution), who led the study with fellow Professor Margaret Murnane and research scientist Tenio Popmintchev, in collaboration with researchers from the Vienna University of Technology, Cornell University, and the University of Salamanca. The breakthrough builds upon earlier discoveries from these and other experts to generate laser-like beams of light across a broad spectrum of wavelengths.