Coherent light generators – Particular active media – Gas
Patent
1990-04-13
1991-12-17
Scott, Jr., Leon
Coherent light generators
Particular active media
Gas
H01S 322
Patent
active
050738976
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to gases to be used for CO.sub.2 laser operations, i.e. gases comprising as components, at least helium, nitrogen and carbon dioxide (CO.sub.2) and intended to be introduced as active medium into the cavity of so-called "CO.sub.2 lasers".
There is presently on the market gases of two types of purity: gases of so-called "industrial purity", whose guaranteed purity is generally in the vicinity of 99.5%, and gases of so-called "scientific purity", whose garanteed purity is generally 99.995% or more.
Since the gases of industrial purity are not sufficiently purified for the requirements of lasers, the gases used for laser operations are of scientific purity, and have the disadvantage of being very costly.
The invention intends to provide more economical gases, which are particularly adapted to CO.sub.2 lasers.
For this purpose, it is an object of the present invention, according to a first aspect thereof, to provide a premixed gas for use in laser operation, containing at least helium, nitrogen and CO.sub.2, characterized in that it has a total purity less than 99.995%, a water content lower than 5 vpm and a total hydrocarbon content lower than 5 vpm (vpm = volume parts per million).
According to a second aspect, it is an object of the invention to provide a gas than can be used for laser production containing at least helium, nitrogen and CO.sub.2 and obtained by mixing at least two gases in situ, characterized in that (a) each of said gases has a total purity less than 99.995% and has a water content lower than 5 vpm and a total hydrocarbon content less than 5 vpm, with the possible exception of CO.sub.2 when the latter constitute one of said gases, wherein said CO.sub.2 may have a water content less than 20 vpm, and (b) the mixture has a water content lower than 5 vpm and a total hydrocarbon content lower than 5 vpm.
It is also an object of the present invention to provide a process for operating with CO.sub.2 laser in which a gas for CO.sub.2 laser operation defined above is introduced into the cavity of the laser.
As it will easily be understood, in the composition of a gas, a distinction has to be made between the components on the one hand, which are intentionally introduced therein, sometimes even at very low concentrations, and the impurities, which are normally present in the gas, sometimes in non negligible quantities if the gas, or its components before mixing, are not highly purified. Thus, the same substance may constitute a component for a gas and an impurity for another, as it will be seen later with respect for example of oxygen, carbon monoxide, CO.sub.2 and nitrogen.
On the other hand, we are only concerned herein with the impurities which are normally found in the industrial production of the components of gases used for CO.sub.2 laser operations, such as: water, oxygen, carbon monoxide, CO.sub.2, C.sub.n H.sub.m hydrocarbons, hydrogen, nitrogen, argon, neon, COS and SO.sub.2.
Examples of gases used for laser operations according to the invention will now be described with reference to the annexed drawings, in which:
FIG. 1 is a diagram illustrating the variation of the power, measured on an industrial CO.sub.2 laser of the rapid axial flux type, under a pressure of 80 mb and a current of 510 mA, as a function of the water content of the gas used for laser operation which is introduced into the cavity of the laser; and
FIG. 2 is a diagram illustrating the variation of the gain measured on an experimental CO.sub.2 laser, as a function of the hydrocarbon content of the gas used for laser operation which is introduced into the cavity of the laser.
The Applicant has carried out extensive research on the influence on the operation of CO.sub.2 lasers, of the presence of various impurities normally found in the industrial production of gases which enter into the composition of gases used for laser operation intended for these lasers. This research was essentially concerned with the gain obtained by lasers, at which value the power of the laser is proporti
REFERENCES:
patent: 3813612 (1974-05-01), Schriever et al.
Applied Physics Letters, vol. 7, No. 1 of Jul. 1, 1965, J. A. Howe: "Effect of Foreign Gases on the CO.sub.2 Laser: R-branch Transitions", pp. 21, 22.
Journal of Applied Physics, vol. 56, No. 9 of Nov. 1, 1984, American Institute of Physics (N.Y.), K. Midorikawa et al., "Comprehensive Study of a CO.sub.2 Laser Using Electrochemical Transformation of Organic Compounds", pp. 2487-2490, voir p. 2487.
Larue Jean-Pierre
Marie Bruno
Marot Christine
Ougarane Lahcen
Van der Have Philippe
Jr. Leon Scott
L'Air Liquide Societe Anonyme pour l'Etude et, l'Exploitation de
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