My watch list
my.chemeurope.com

Krypton fluoride laser

For background information about krypton and fluorine, the two active elements in a krypton fluoride laser, see Krypton and Fluorine.

A krypton fluoride laser (KrF laser) utilizes the chemical property of krypton gas and the strong oxidizing power of fluorine gas to produce laser between the two with the stimulation of a strong electron energy input.

Theory

A krypton fluoride laser absorbs energy from a source and causes the krypton gas to react with the fluorine gas, producing krypton fluoride, which is an unstable compound.

$2Kr_{(g)} + F_{2\, (g)} \xrightarrow{electron\,energy} \,2KrF_{(g)}$

When the supplied energy is stopped, the compound will decompose and the excess chemical energy stored in the compound will release in the form of strongly synchronized radiation.

$2KrF_{(g)} \xrightarrow{\,} \,2Kr_{(g)} + F_{2\, (g)}+ energy$

The result is an excimer laser that radiates energy at 248 nm, which lies in the near ultraviolet portion of the spectrum.

Applications

The KrF laser has been of interest in the nuclear fusion energy research community in inertial confinement experiments. This laser has high beam uniformity, short wavelength, and the ability to modify the spot size to track an imploding pellet.

In 1985 the Los Alamos National Laboratory completed a test firing of an experimental KrF laser with an energy level of 1.0 × 104 joules. The Laser Plasma Branch of the Naval Research Laboratory completed a KrF laser called the Nike laser that can produce about 4.5 × 103 joules of UV energy output in a 4 nanosecond pulse. Kent A. Gerber was the driving force behind this project. This later laser is being used in laser confinement experiments.

The KrF laser is also used in laser microlithography, where the short wavelength is desirable for etching very small features. However it will likely be replaced for this purpose by the argon fluoride laser, which has a 193 nm wavelength. Pulse widths of KrF lasers in commercial applications are typically 20-30 nanoseconds.

This laser has also been used to produce soft X-ray emission from a plasma irradiated by brief pulses of this laser light. Other potential applications include machining of certain materials such as plastic, glass, crystal, composite materials and organic tissue. The light from this UV laser is strongly absorbed by lipids, nucleic acids and proteins, giving it potential applications in medical therapy and surgery.

Safety

The light emitted by the KrF is invisible to the human eye, so additional safety precautions are necessary when working with this laser to avoid stray beams. Gloves are needed to protect the flesh from the potentially carcinogenic properties of the UV beam, and UV goggles are needed to protect the eyes.

References

• J. Sethian, M. Friedman, M. Myers, S. Obenschain, R, Lehmberg, J. Giuliani, P. Kepple, F. Hegeler, S. Swanekamp, D. Weidenheimer, "Krypton Fluoride Laser Development for Inertial Fusion Energy".
• M. C. Myers, J. D. Sethian, J. L. Giuliani, R. Lehmberg, P. Kepple, M. F. Wolford, F. Hegeler, M. Friedman, T. C. Jones, S. B. Swanekamp, D. Weidenheimer and D. Rose, "Repetitively pulsed, high energy KrF lasers for inertial fusion energy", 2004, Nuclear Fusion, 44.
• J. Goldhar, K. S. Jancaitis, J. R. Murray, L. G. Schlitt, "An 850 J, 150 ns narrow-band krypton fluoride laser", 1984, 13th Intern. Conf. on Quantum Electron.