A special type of gas laser that gets its power by an electrical discharge where the excimer works as a lasing medium, or more precisely an exciplex in existing design are known as «Excimer lasers». These are the type of molecules that exists only with one atom in an excited electronic state.
Once a molecule transfers its excitation energy to a photon, its atoms are no longer bound to each other and the molecule disintegrates. This instantly decreases the population of the low energy state thus greatly facilitating a population inversion.
Excimers that are used in current times are all noble gas compounds; nobles’ gases are chemically inert in nature and can only form compounds that are in an excited state.
In general, the ultraviolet wavelengths are required by the excimer lasers to work with major applications including semiconductor photolithography and LASIK eye surgery. KrCl (222 nm), XeCl (308 nm), ArF (emission at 193 nm), KrF (248 nm), and XeF (351 nm) are examples of some commonly used excimer molecules.
There are some molecular fluorine lasers available in the market which emit at 157 nm in the vacuum ultraviolet are sometimes considered as an excimer laser, although this appears to be a misnomer inasmuch as F2 is a stable compound. The concept of optical laser optics and fused silica optical window can be used to answer the question what is optical lens types.
Free-electron lasers (FELs in short form), generate coherent, high-power radiation that can be controlled, currently that falls within a range from microwave through terahertz radiation and infrared to the visible spectrum, to soft X-rays.
Among all the laser types, these type of laser types has the widest range of frequency. Although, there are same optical characteristics in the FEL beams as other lasers have, such as coherent radiation, FEL operation is quite different.
FELs use a relativistic electron beam as the lasing medium, hence the term free-electron which is totally opposite to the gas, liquid, or solid-state lasers which rely on bound atomic or molecular states.
An organic dye is used as the gain medium in the dye lasers. The available dyes or mixture of dyes have a wide gain spectrum which allows these lasers to be highly adjustable or to produce very short-duration (on the order of a few femtoseconds).
Although these tunable lasers are primarily known in their liquid form, researchers have also demonstrated narrow-linewidth tunable emission in dispersive oscillator configurations incorporating solid-state dye gain media.