Transversely excited non waveguide RF gas laser configuration

A gas laser consisting of a single elongated piece of dielectric material (1), with two hermetically sealed parallel elongated chambers (2) and (3), and an opening (4) connecting the two chambers. One of the elongated chambers (2) is of a cross section suitable for confining a laser gas discharge. The other elongated chamber (3) is a reservoir for laser gas, which also functions to dampen the unwanted acoustic waves generated by the laser gas discharge and as a means of extending the operating lifetime of the laser gas. The opening connecting the two elongated chambers serves to dampen the acoustic waves generated by the laser gas discharge traveling the length of the elongated laser chamber and to stop unwanted low angle wall reflections of laser light energy traveling at a slight angle to the length of the laser chamber.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to gas lasers, and more particularly, to 
an improved high power, large double bore RF powered gas laser. 
2. Description of the Related Art 
It is generally known that higher power output energy can be obtained from 
a gas laser if the diameter of the laser chamber is made larger. For 
example, a waveguide laser will have a laser chamber which is about 1-2 
millimeters in cross-section, while a higher power, large bore laser will 
have a laser chamber which ranges from about 0.25 inches in diameter to 
over 0.5 inches in diameter. Furthermore, the length of the laser chamber 
in such large bore, higher power lasers is also increased. Such elongated 
laser chambers usually have continuous, smooth internal side walls which 
reflect unwanted low angle laser light energy traveling along the length 
of the laser chamber, at a slight angle to the length of the laser 
chamber. At this slight angle, the reflections work their way around the 
inside diameter of the laser chamber, and produce unwanted laser modes 
which are difficult to deal with. One known way to reduce these laser wall 
modes is by placing apertures inside the laser chamber. However, these 
internal apertures reduce laser output power. Apertures may also be placed 
outside of the laser chamber for clipping the unwanted laser energy. 
U.S. Pat. No. 4,589,114, discloses a gas laser having an elongated 
cylindrical chamber with a plurality of groves formed on the internal 
surface to provide optical mode control. Additionally, this patent 
discloses numerous electrode configurations to transversely excite the 
gas, such as CO.sub.2, in the cylindrical chamber, to produce a laser 
discharge which is reflected and guided by a pair of reflectors mounted at 
the ends of the cylindrical chamber. This patent, however, fails to 
disclose a double bore laser. 
U.S. Pat. Nos. 4,596,018 and 4,618,916 also disclose gas discharge lasers 
having elongated cylindrical laser chambers with external electrodes 
transverse to the laser chamber. These patents, however, also fail to 
disclose double bore lasers. 
Another problem seen with an increase in gas laser size is that acoustic 
waves are generated within the gas laser discharge thus affecting the rate 
at which the laser can be modulated. Most lasers do not operate in the 
continuous wave mode but are modulated at a frequency between 0 and 60 
KHz. Therefore, when the laser modulation rate and the acoustic waves 
inside the laser are at the same frequency, the laser output power is 
reduced dramatically. 
There is, therefore, a need in the art for an improved RF powered high 
power laser. The present invention provides such an improvement, by 
reducing unwanted wall reflections without losing laser output power, and 
reducing acoustic waves inside the laser cavity to a level which does not 
affect the power output during modulation. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a means of 
eliminating unwanted laser wave reflections in a laser cavity and to 
improve laser beam quality and laser power output. 
It is another object of the present invention to provide a means of 
eliminating unwanted acoustic waves which are generated in a laser gas 
discharge within an RF excited gas laser, so as to improve the laser 
modulation and performance thereof. 
It is a further object of the present invention to provide a gas laser with 
a gas reservoir connected to a separate laser chamber, for efficient gas 
exchange between the laser and reservoir chambers, so as to increase the 
operating lifetime of the laser gas. 
These and other objects and advantages are achieved by providing an 
improved gas laser having an elongated cylindrical body with separate 
elongated cylindrical chambers formed therein, with an opening in the 
laser body connecting the separate chambers. A plurality of electrodes are 
placed longitudinally along the exterior of the laser body, and these 
electrodes are excited by an RF generator electrically connected thereto.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The following description is provided to enable any person skilled in the 
art to make and use the invention and sets forth the best modes 
contemplated by the inventor of carrying out his invention. Various 
modifications, however, will remain readily apparent to those skilled in 
the art, since the generic principles of the present invention have been 
defined herein specifically to provide for an improved and simplified high 
power gas laser generally indicated at 1. 
The gas laser 1 is preferably fabricated from a single, continuous 
elongated piece of dielectric material, such as ceramic or glass, which 
may be of any shape, but which is preferably circular, between 0.75 to 1.0 
inches in diameter, and may be of any desired length. The laser 1, 
includes a plurality of elongated cylindrical bores 2, 3, formed extending 
entirely therethrough between the ends thereof. The bores may also be of 
any shape, and are preferably parallel, with a first bore 2 forming an 
approximately 0.25 inches in diameter laser gas discharge chamber. The 
second bore 3, forms a laser gas reservoir chamber, which is preferably 
smaller than the first bore, but which may range in cross-section from 
about 0.20 to 0.25 inches. These elongated chambers 2 and 3 are fluidly 
connected by an opening 4, which may be of any desired length or width, 
but which is preferably a narrow slot, approximately 0.0625 inches wide, 
extending along the full length of the chambers 2 and 3, so that laser gas 
may flow freely between the chambers. These chambers 2 and 3 hold a 
sufficient amount of laser gas, such as CO.sub.2, He, and N.sub.2, at a 
pressure of about 1 torr to 1,000 torr to maintain a laser gas discharge 
therein. The preferred single piece of dielectric material forming the 
laser 1, allows for a structural shape of maximum mechanical rigidity and 
stiffness required for laser construction. 
The laser 1 has a plurality of electrodes 5 and 6, constructed from an 
electrically conductive material. The first electrode 5 is secured to the 
external surface of the laser 1, and preferably extends longitudinally 
along the laser, adjacent to and parallel to the elongated gas discharge 
chamber 2. Second and third electrodes 6 are mounted on opposite sides and 
extend longitudinally along the gas laser 1. These second and third 
electrodes are preferably water cooled, symmetric to and form a ground 
plane for the first electrode. That is, the first electrode is preferably 
mounted midway between the two ground electrodes 6. An RF energy source 7 
applies a voltage of alternating polarity to the first electrode 5 to 
establish a laser gas discharge in the laser gas discharge chamber 2, 
transversely to the length of this chamber. Symmetric cooling of the water 
cooled ground electrodes 6 against the external surface of the laser, 
outside of both the laser gas discharge chamber 2 and laser gas reservoir 
chamber 3, minimizes thermal distortions which would affect laser 
performance. The open ends of the laser 1 and elongated chambers 2 and 3 
are provided with cover means, such as end plates 8, to hermetically seal 
these ends. 
Two laser optic means, such as optical reflectors 9 are hermetically sealed 
in openings in the end plates 8, aligned with the open ends of the laser 
gas discharge chamber 2, to guide laser light energy from a gas discharge 
within the laser gas discharge chamber 2. The laser light produced therein 
is independent of the internal walls as it travels the length of the 
elongated cylindrical laser gas discharge chamber 2. 
The pair of end plates 8 are preferably fabricated from a metal, such as 
stainless steel, and are securely fastened to the ends of the laser by air 
tight sealing means, such as washers or the like, made of indium alloy, 
about 0.005 inches thick. At least one of these end plates may have a 
fitting attached thereto to enable the laser to be filled with a selected 
laser gas, in a manner known to those skilled in the art. This fitting is 
normally pinched off after power testing of the laser. Each of the end 
plates preferably has a through opening formed therein, aligned with the 
laser gas discharge chamber end openings, and the laser optics 9 are 
mounted over these through openings in alignment with the laser gas 
discharge chamber end openings, preferably on adjustable mounts (not 
shown), and sealed air tight to the end plates, as by use of sealing 
means, such as 0.005 inch thick indium washers. The laser optic 9 at a 
first open end of the laser gas discharge chamber 2 preferably has an 
optical reflectivity of near 100 percent, and may be made of any desired 
material, such as silicon having a silver or gold coating. The laser optic 
9 at the other or second open end of the laser gas discharge chamber 2, 
preferably has an optical reflectivity of about 85 to 95 percent and may 
made of any desired material, such as zinc selenide or germanium. These 
laser optics are adjusted in a manner known to those skilled in the art, 
to reflect the laser light energy from the gas discharge within the laser 
gas discharge chamber back on itself so as to travel longitudinally along 
the length of the laser gas discharge chamber and to be optically 
independent of the internal walls of the laser gas discharge chamber. 
The 3 elongated, longitudinal electrodes, are made from any desired 
electrically conductive material. For example, the first electrode 5 is 
generally a 0.125 inch wide copper ribbon and forms the positive 
electrode. The other two electrodes 6, are generally about 0.375 inches 
wide and made of aluminum with a center passage for water cooling, in a 
manner known to those skilled in the art. These two water cooled 
electrodes 6 are placed on opposite sides of the laser 1 and symmetric 
with the positive electrode 5. These two water cooled electrodes 6 are 
electrically connected to ground and, in combination with the positive 
electrode, produce a transversely excited laser gas discharge within the 
laser gas discharge chamber 2, in a manner well known to those skilled in 
the art. 
The RF power source 7 is electrically coupled to the electrodes 5 and 6 in 
a known manner, and provides an alternating electric field in the laser 
gas discharge chamber 2, in a direction transverse to the length of the 
laser gas discharge chamber, at a frequency from about 10 MHz to 3 GHz, to 
establish a laser gas discharge therein. 
Those skilled in the art will appreciate that various adaptations and 
modification of the just-described preferred embodiments can be configured 
without departing from the scope and spirit of the invention. Therefore, 
it is to be understood that, within the scope of the appended claims, the 
invention may be practiced other than as specifically described herein.