They can already generate laser-like X-ray beams in the soft X-ray region and believe they have discovered how to extend the process all the way into the hard X-ray region of the electromagnetic spectrum.
"If we can do this, it could lead to all kinds of possibilities," Kapteyn said. "It might make it possible to improve X-ray imaging resolution at your doctor's office by a thousand times. The X-rays we get in the hospital now are limited. For example, they can't detect really small cancers because the X-ray source in your doctor's office is more like a light bulb, not a laser. If you had a bright, focused laser-like X-ray beam, you could image with far higher resolution."
Their method can be thought of as a coherent version of the X-ray tube, according to Murnane. In an X-ray tube, an electron is boiled off a filament, then it is accelerated in an electric field before hitting a solid target, where the kinetic energy of the electron is converted into incoherent X-rays. These incoherent X-rays are like the incoherent light from a light bulb or flashlight -- they aren't very focused.
In the tabletop setup, instead of boiling an electron from a filament, they pluck part of the quantum wave function of an electron from an atom using a very intense laser pulse. The electron is then accelerated and slammed back into the ion, releasing its energy as an X-ray photon. Since the laser field controls the motion of the electron, the X-rays emitted can retain the coherence properties of a laser, Murnane said.
Being able to build a tabletop X-ray laser is just the beginning, said Kapteyn.
"An analogy that is pretty close to what is going on in this field is the MRI, which started as just a fundamental investigation," said Kapteyn. "People then started using it for microscopy, and then it progressed into a medical diagnostic technique."
Murnane and Kapteyn were recently recogniz
|Contact: Margaret Murnane|
University of Colorado at Boulder