A krypton fluoride laser (KrF laser) is a particular type of excimer laser, which is sometimes (more correctly) called an exciplex laser. With its 248 nanometer wavelength, it is a deep ultraviolet laser which is commonly used in the production of semiconductor integrated circuits, industrial micromachining, and scientific research. The term excimer is short for 'excited dimer', while exciplex is short for 'excited complex'. An excimer laser typically contains a mixture of: a noble gas such as argon, krypton, or xenon; and a halogen gas such as fluorine or chlorine. Under suitably intense conditions of electromagnetic stimulation and pressure, the mixture emits a beam of coherent stimulated radiation as laser light in the ultraviolet range. KrF and ArF excimer lasers are widely incorporated into high-resolution photolithography machines, one of the critical tools required for microelectronic chip manufacturing in nanometer dimensions. Excimer laser lithography has enabled transistor feature sizes to shrink from 800 nanometers in 1990 to 10 nanometers in 2016. Theory A krypton fluoride laser absorbs energy from a source, causing the krypton gas to react with the fluorine gas producing the exciplex krypton fluoride, a temporary complex in an excited energy state: 2 Kr + → 2 KrF The complex can undergo spontaneous or stimulated emission, reducing its energy state to a metastable, but highly repulsive ground state. The ground state complex quickly dissociates into unbound atoms: 2 KrF → 2 Kr + The result is an exciplex laser which radiates energy at 248 nm, near the ultraviolet portion of the spectrum, corresponding with the energy difference between the ground state and the excited state of the complex. Example Systems There have been several of these lasers built for ICF experiments; examples include: Los Alamos built a KrF laser in 1985 to prove test firing of beam with an energy level of 1.0 × 104 joules. This was part of the larger Aurora laser research effort that looked a CO2 lasers and other systems. Nike Laser. 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. The NIKE laser was switched to an Argon fluoride laser after 2013 to show the impact of going to shorter (193 nm) wavelengths. Naval Research Laboratory built the Electra laser and Nike to prove out both KrF and ArF