Coherent light generators – Particular active media – Gas
Patent
1990-10-02
1992-08-04
Scott, Jr., Leon
Coherent light generators
Particular active media
Gas
372 87, 372 88, H01S 303
Patent
active
051366061
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a discharge tube for a high-speed axial-flow type discharge pumping gas laser device utilizing a high-frequency discharge, and more particularly, to a configuration of an electrode portion of a discharge tube.
BACKGROUND ART
FIG. 3 is a conceptual diagram illustrating a configuration of electrodes of a cylindrical discharge tube according to the prior art, wherein 1 denotes a discharge tube, and 2a and 2b denote metal electrodes arranged along the outer periphery of the tubular wall of the discharge tube 1 and utilizing the tubular wall as a capacitive load. A high-frequency electric power of 2 MHz is supplied from a high-frequency, power supply 3, provided outside the discharge tube 1, through the electrodes to a laser gas flow 4 passing through the interior of the discharge tube 1 at a high speed. Numeral 5a schematically illustrates a transverse mode of the laser beam produced by this discharge pumping means. This transverse mode is a multimode, as explained hereinafter.
Optical elements and other elements necessary for a laser oscillator to produce a laser beam are omitted from FIG. 3.
FIG. 4 is a sectional view of the discharge tube in FIG. 3. As will be understood from FIG. 4, because the electrodes 2a and 2b are arranged on the outer periphery of the discharge tube 1, the closer they are to the tubular wall of the discharge tube away from the center thereof, the shorter the discharging distance between the opposed electrodes 2a and 2b, and thus the electric field is concentrated at the side edges of the electrodes 2a and 2b. Accordingly, a discharge current is liable to be concentrated at both ends of the discharge tube 1 and thus the current density per unit volume is large.
The distribution of the electric field strength is indicated by electric lines of force 6, and the laser active region is indicated at 7 in FIG. 4.
According to the prior art, the laser oscillation gain is lower at the center of the discharge tube than at the outer portions thereof, and thus a single-mode laser beam usable for a laser machining operation cannot be obtained. Accordingly, a multimode transverse mode of the laser beam is used, as indicated at 5a in FIG. 3.
DISCLOSURE OF THE INVENTION
The present invention has been created in view of the above circumstances, and an object thereof is to provide a discharge tube for a gas laser device by which the distribution of a current density, and thus a laser oscillation gain within a discharge tube, is made uniform to obtain a single mode laser beam able to be used for a laser machining operation.
To achieve the above object, according to the present invention, there is provided a discharge tube for a high-speed axial-flow type discharge pumping gas laser device in which the axis of a laser gas flow and the axis of a laser oscillation are in alignment and are perpendicular to the direction of discharge for high-frequency discharge pumping, the discharge tube being characterized in that a capacitive load medium under metal electrodes has convexly curved faces opposed to each other and constitutes a discharge tube.
Since the capacitive load medium under the metal electrodes has convex faces, the discharge current and the distribution of the oscillation gain are made uniform, whereby a single-mode laser beam can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a discharge tube for a gas laser device according to an embodiment of the present invention;
FIG. 2 is a sectional view of the discharge tube shown in FIG. 1;
FIG. 3 is a conceptual diagram illustrating a configuration of electrodes of a prior art cylindrical discharge tube; and
FIG. 4 is a sectional view of the discharge tube shown in FIG. 3.
BEST MODE OF CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of a discharge tube for a gas laser device according to an embodiment of the invention, wherein 1 denotes a discharge tube, and 2a and 2b
REFERENCES:
patent: 4359777 (1982-11-01), Fox et al.
patent: 4464760 (1984-08-01), Sutter, Jr.
patent: 4800567 (1989-01-01), Karube
patent: 4885754 (1989-12-01), Egawa
patent: 4964136 (1990-10-01), Egawa
Iehisa Nobuaki
Yamazaki Etsuo
Fanuc Ltd.
Jr. Leon Scott
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