An excimer laser.
Excimer laser is a gas laser operating on electronic transitions of excimer molecules (molecules that exist only in electronically excited States).
Excimer laser – a gas laser in which the laser active medium in the form of a volatile compound ions in a gas discharge electrical pumping.
Excimer laser gas laseroperating on electronic transitions of excimer molecules (molecules that exist only in electronically excited States).
The world’s first excimer laser was invented in 1970
Molecules of the working substance of the active medium of excimer lasers can be divided into two types: formed by particles of the same substance and the particles of two different substances. Active medium formed by the particles of the same substance, called “exameron”. Active medium formed by the particles of two different substances, called “exciplexes”.
The term excimer (eng. excimer, excited dimer) stands for excited dimer and refers to the type of material used as the working medium of the laser. Excimer is a dimer or heterodimer short-lived molecule formed from two types of atoms, at least one of which is in an electronic excited state. Eximer formed between two atoms or molecules that have not formed a chemical bond if both would be mostly stable, unexcited state. The lifetime of excimers is very small and is usually a matter of nanoseconds.
The term exciplex (eng. exciplex, excitedcomplex) denotes the excited molecular complexes of two or more molecules.
As the working substance excimer lasers use the noble gases (argon, krypton, xenon), which, because of their inertia do not form molecules, as well as their compounds with Halogens (bromine, fluorine, chlorine).
Laser radiation exoneree molecules is due to the fact that she is attractive (associative) excited state and “repulsive” (not associative) main. That is, of excimer molecules in General, a stable state does not exist. This is because noble gasessuch as argon, xenon or krypton vysokinichi and usually do not form chemical compounds. In the excited state (caused by electrical discharge or high energy electron beams), they can form temporarily associated molecules with themselves (eximer) or with Halogens (exiplexes), such as bromine, fluorine or chlorine, a bromide, xenon, krypton chloride, krypton fluoride, etc. the Appearance of these molecules in the excited bound state automatically creates the inversion of populations between the two energy levels of the molecule. Eximer or exiplexes quickly disintegrate into component atoms (within picoseconds), causing the molecule goes from the excited into the ground state of stable atoms by emitting the quantum of electromagnetic radiation (photon).
The wavelength of an excimer laser depends on the composition of the gas used, and usually lies in the ultraviolet region:
|Excimer (exciplex)||Wavelength, nm|
Excimer lasers typically operate in a pulsed mode with a pulse repetition frequency from 1 Hz to several hundred Hz, depending on the model rate can reach 2 kHz; it is also possible to generate isolated pulses. The pulses usually have a duration from 10 to 30 NS and energies from units to hundreds of MJ.
The device of the excimer laser device is similar to any other gas laser. Excimer laser is filled with gas – active medium of the discharge tube. The discharge tube is closed from one side of the fully reflective mirror, and on the other hand, the output semi – transparent mirror. As the pumping source acts as an electric discharge or high-energy beam of electrons.
An excimer laser is widely used in eye surgery (laser vision correction), in dermatology, in the microprocessing of materials, in the production of LCD panels and semiconductor manufacturing.
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