X-Ray Lasers:

Michael Wheeler, Associate News Editor

Since the demonstration of the first visible lasers in the 1960s, the prospect of a tabletop x-ray laser has intrigued chemists and biologists alike. Such a laser might finally unlock the many secrets of what goes on within cells or provide researchers with a better view of chemical interactions. For the fusion experts, the x-ray laser promises a better method of evaluating plasmas.
While some scientists dreamed of applications, a small group of researchers in the US, Europe and Japan have steadfastly explored different ways of devising such a laser, experiencing mixed results along the way.
Fourteen years ago, engineers at the Lawrence Livermore National Laboratory in California aimed Nova, the US' largest and most powerful laser at the time, at small foil targets, creating a high-density, high-temperature neon-like plasma. The ions that were excited by the laser pulse jumped to a higher energy level, resulting in population inversion. After decades of fruitless research, the x-ray laser was born.
Since then, researchers have scrambled to find ways around using gargantuan pumping lasers like Nova and have investigated ways of making devices compact enough to fit on a laboratory table. They have also come tantalizingly close to reaching the hallowed "water window," the small range of wavelengths between 2.2 and 4.4 nm where water is transparent but carbon absorbs readily.