U.S. patent application number 09/729217 was filed with the patent office on 2001-05-10 for laser oscillation device.
Invention is credited to Ozu, Akira.
Application Number | 20010001003 09/729217 |
Document ID | / |
Family ID | 26569275 |
Filed Date | 2001-05-10 |
United States Patent
Application |
20010001003 |
Kind Code |
A1 |
Ozu, Akira |
May 10, 2001 |
Laser oscillation device
Abstract
A new laser oscillation device is provided which is capable of
readily cooling down a laser medium without employing any
large-size complicated separate or discrete devices such as fan
blowers while at the same time improving the laser oscillation
efficiency to thereby easily generate high-output laser light. To
this end, a Lorentz force drive electromagnetic pump means and a
cooling means are provided in a way such that the Lorentz force
drive electromagnetic pump means is operable to drive the laser
medium while allowing the cooling means to cool down the laser
medium being driven.
Inventors: |
Ozu, Akira; (Ibaraki,
JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 "K" Street, N.W. Suite 800
Washington
DC
20006
US
|
Family ID: |
26569275 |
Appl. No.: |
09/729217 |
Filed: |
December 5, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09729217 |
Dec 5, 2000 |
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09200865 |
Nov 27, 1998 |
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6185234 |
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Current U.S.
Class: |
372/34 ; 372/109;
372/76 |
Current CPC
Class: |
H01S 3/041 20130101;
H01S 3/0326 20130101 |
Class at
Publication: |
372/34 ; 372/76;
372/109 |
International
Class: |
H01S 003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 1997 |
JP |
329039/1997 |
Nov 9, 1998 |
JP |
318177/1998 |
Claims
What is claimed is:
1. A laser oscillation device comprising Lorentz force drive
electromagnetic pump means and cooling means, wherein a laser
medium is driven by the Lorentz force drive electromagnetic pump
means, and wherein the laser medium being driven is cooled by the
cooling means.
2. The laser oscillation device according to claim 1, wherein the
cooling means is one of a wall of a laser vacuum vessel being
cooled and a cooler machine.
3. The laser oscillation device according to claim 1 or 2, wherein
a magnetic field generation means for applying a magnetic field to
the laser medium within a laser tube is provided as the Lorentz
force drive-electromagnetic pump means, and wherein the discharge
between electrodes is performed upon application of the magnetic
field by said magnetic field generation means causing oscillation
of laser while simultaneously letting a discharge plasma
generatable in a discharge region exhibit convection due to a
Lorentz force created by a discharge current flowing at right
angles to the magnetic field to thereby drive the laser medium.
4. The laser oscillation device according to claim 3, wherein the
magnetic field generation means is provided inside or outside of
the laser tube.
5. The laser oscillation device according to claim 3 or 4, wherein
the magnetic field generation means is one of an inductive coil and
a magnet.
6. The laser oscillation device according to any one of the
preceding claims 1 to 5, wherein a cathode and an anode have a
structure wherein a discharge current has a component perpendicular
to the direction of a magnetic field.
7. The laser oscillation device according to any one of the
preceding claims 1 to 6, wherein the discharging direction is at
right angles to the magnetic field direction.
Description
BACKGROUND OF THE INVENTION
1. 1. Field of the Invention
2. The present invention relates to laser oscillation apparatus.
More particularly, this invention relates to new laser oscillator
devices adaptable for use as laser-machining discharge excitation
type laser oscillators which require large-output and
high-efficiency laser light.
3. 2. Description of the Related Art
4. Typically, in discharge laser oscillation apparatus, the
discharge is performed with respect to a laser medium in order to
attain laser oscillation required. When this is done, the laser
medium increases in temperature. The higher the medium temperature,
the less the efficiency of such laser oscillation. This phenomenon
will become more severe especially in pulse laser oscillation
devices.
5. Conventionally, in order to avoid such reduction of laser
oscillation efficiency due to temperature increase of the laser
medium thereby obtaining efficiency-enhanced laser oscillation, one
approach is to wait for the laser medium to have lowered its
temperature down to an acceptable level; another approach is to
replace and cool the laser medium per se.
6. Additionally, in large-output lasers such as an excimer laser or
carbon dioxide gas laser or the like, a convection device such as a
fan blower or the like as well as a thermal exchanging machine are
provided inside of a laser tube for forcibly causing a laser medium
gas to exhibit convection to thereby achieve cooling by
substitution and circulation from a laser cavity or between
electrodes, which in turn lets the resulting laser output power
stay higher.
7. However, in the prior art, large-output fan blower devices have
been required in order to attain the circulation or percolation of
the laser medium such as a gas or the like within laser devices or
laser tubes, which fan blowers might be configured from large-scale
complicated electrical equipment including a motor, fan, vacuum
shaft coupler and others, resulting in an increase in size and
production cost of laser devices and laser tubes concerned. Another
problem faced with the prior art is that resultant power
dissipation can significantly increase undesirably.
SUMMARY OF THE INVENTION
8. The present invention was made in view of the foregoing
technical background, and its primary object is to provide a laser
oscillation device capable of readily cooling down laser media
without having to employ any large-scale complicated separate
apparatus or equipment such as fan blowers thereby improving the
laser oscillation efficiency thus enabling generation of
high-output laser light while reducing complexity.
BRIEF DESCRIPTION OF THE DRAWINGS
9. The forgoing and other objects, features and advantages of the
present invention will be apparent from the following more
particular description of preferred embodiments of the invention,
taken in conjunction with the accompanying drawings, in which:
10. FIG. 1 is a diagram showing, in longitudinal cross section, a
laser oscillation device of the longitudinal discharge type in
accordance with one preferred embodiment of this invention, which
includes a laser tube and employs a coaxial cylindrical electrode
structure.
11. FIG. 2 is a diagram showing a cross-sectional view of the laser
tube of the laser oscillator device as looking at from the
direction of arrow "A" in FIG. 1.
12. FIG. 3 is a graph exemplarily showing a relation of laser
output obtainable from the laser oscillator shown in FIG. 1 versus
an associated magnetic field in the coaxial direction thereof.
13. FIG. 4 depicts an interelectrode cross-sectional view of a
laser medium drive mechanism used in a laser oscillator device of
the transverse discharge type employing an elongate electrode in
accordance with another embodiment of this invention.
DETAILED DESCRIPTION OF THE INVENTION
14. (First Embodiment)
15. Referring now to FIG. 1, there is illustrated in longitudinal
cross section a laser oscillation device of the longitudinal
discharge type including its laser tube employing a coaxial
cylindrical electrode in accordance with one preferred embodiment
of the present invention. See also FIG. 2, which is a
cross-sectional view of the laser tube as looking at from the
direction "A" of FIG. 1.
16. In the laser oscillator device shown as one example in FIG. 1,
this device is configured including a negative electrode or
"cathode" 1 and positive electrode or "anode" 2 with a laser tube 4
being mounted therebetween. The cathode 1 and anode 2 are different
in diameter dimension from each other. The laser tube 4 is
surrounded with a solenoid coil 3, as a magnetic field generation
means, which applies a magnetic field 5 axially between
inter-electrodes of the laser tube 4. While the magnetic field 5 is
being applied, when the discharge is performed between the cathode
1 and the anode 2, a discharge current 7 rushes to flow between the
cathode 1 and anode 2 in the direction at right angles to the
magnetic field 5 as conceptually shown in FIG. 2, which in turn
causes effectuation of laser oscillation. When this is done, the
Lorentz force 8 takes place due to such perpendicular discharging
between the discharge current 7 and magnetic field 5 simultaneously
when laser oscillation is effected, thereby allowing the resultant
discharge plasma 6 to behave to convect within the laser tube 4 as
exemplarily shown in FIG. 2 so that a laser medium in the laser
oscillation region inside the cathode 1 is subject to replacement
or substitution due to such convection. The laser medium thus
substituted is moved from the laser cavity or between the
electrodes and then effectively cooled down by the inner wall of
the laser tube 4. The wall of laser tube 4 is being air-cooled.
17. In this laser oscillator device embodying the invention, it
will also be permissible that a means is provided such as a device
for forcing the convection of discharge plasma 6 within the laser
tube 4 to flow into the center part of the laser tube 4 between the
cathode 1 and anode 2; with this means, it becomes possible to
further improve the substitution rate of the laser medium toward
the inside of cathode 1.
18. Here, experimentation was carried out to measure a laser output
actually obtainable from the laser oscillator device incorporating
the principles of the invention shown in FIG. 1, which the laser
output is relative to the magnetic field 5 in the axis direction.
One typical measurement result is demonstrated in FIG. 3, which
shows a relation of the measured laser output power (W) versus
intensity (Gauss) of the axial magnetic field 5.
19. It should be noted that in the laser oscillator device used
during the characteristic measurement, its laser medium was made of
an HBr gas while employing a low-temperature copper-vapor laser
having the aperture diameter of 40 mm.phi. as the laser tube 4. The
storage capacitor charging voltage Vc was set at 20 kV. A Ne gas
used was at a pressure of 22 Torr. HBr concentration was 5%,
whereas the laser pulse repetition frequency was 15 kHz.
20. It is apparent by viewing the graph of FIG. 3 that as the axial
magnetic field 5 applied by the solenoid coil 3 increases in
magnitude, the resultant laser output likewise increases by several
tens of percent (%) in intensity. It may be considered that the
obtainability of such high laser output is originated from the fact
that successful cooling was achieved in the discharge region by
circulation of the laser medium inside the laser tube 4 due to
presence of the Lorentz force. It may also be considered that an
increase in laser output relative to such increase in magnetic
field is due to the fact that the laser medium's circulation and
cool-down speed depend upon the Lorentz force. Hence, it is
possible by further increasing the magnetic field intensity to
achieve further improvements of the laser output.
21. (Second Embodiment)
22. Turning now to FIG. 4, there is depicted in cross-section a
laser medium drive mechanism of a laser oscillator device of the
transverse discharge type which makes use of elongate electrodes in
accordance with another embodiment of the invention.
23. The laser oscillator shown in FIG. 4 is arranged in a way such
that its cathode 1 and anode 2 are externally applied a magnetic
field 5 in a specified direction lying parallel to the longitudinal
direction of the electrodes, by use of a magnetic field generation
means (not shown) including but not limited to a variety of types
of coil members (solenoid coils, Helmholtz coils, yoke coils, or
the like) or magnets, or any equivalents thereto. When the
discharge is effected between the cathode 1 and anode 2 with the
magnetic field 5 being applied thereto, a discharge current 6
attempts to flow in a direction perpendicular to the magnetic field
5, resulting in oscillation of laser. Upon occurrence of this laser
oscillation, the Lorentz force 7 takes place simultaneously with
respect to a discharge plasma 8 in the direction at right angles to
both the discharge current 6 and the magnetic field 5. This Lorentz
force 7 lets the discharge plasma 8 be pushed out of the space
between the cathode 1 and anode 2, resulting in substitution of the
laser medium within the laser tube 4. This medium substitution in
turn permits movement from the laser cavity or between the
electrodes thus providing effective cooling activities.
24. As has been described above, the laser oscillator device
embodying the invention has the Lorentz force drive electromagnetic
pump mechanism for use in creating the Lorentz force due to the
presence of a magnetic field as applied by the magnetic field
generation means including but not limited to coils or magnets.
This Lorentz force drive electromagnetic pump mechanism functions
to allow the laser medium's plasma is driven in a prespecified
direction at right angles to both the current and the magnetic
field, thereby enabling achievement of sufficient cooling. It is
thus possible to more readily accomplish with no difficulties the
intended cooling and substitution of the laser medium being kept at
high temperatures due to discharging, while avoiding a need for
employment of any "special" laser medium set at low temperatures
unlike the prior art.
25. Also note that laser oscillation is performed simultaneously
when driving the laser medium due to interelectrode discharging. In
this case the applied magnetic field lets electrons exhibit spiral
motion, increasing the efficiency of impact or collision with
associative atoms and molecules, which may in turn increase the
laser efficiency.
26. Another advantage of the laser oscillator is that it becomes
possible by the magnetic field as applied by the magnetic field
generation means to achieve the required discharging with enhanced
spacial uniformity inside the laser medium used.
27. It is noted here that while in the aforementioned embodiments
the magnetic field generation means is arranged to be mounted
outside the laser tube, this magnetic field generation means may
alternatively be disposed inside the laser tube in such case also,
the intended effects and advantages are obtainable which are
similar to those in the case the generator is provided
externally.
28. Also note that the cooler means for cooling the laser medium
being presently driven should not exclusively be limited to the
illustrative laser vacuum vessel's wall as set in the cooling
condition such as air-cooling, and may also be designed employing a
separate cooler machine where appropriate.
29. This invention should not be limited only to the aforementioned
embodiments, and it will be understood by those skilled in the art
that other changes in form and details may be made therein without
departing from the spirit and scope of the invention.
30. As has been described in detail above, in accordance with this
invention, there is provided a new and improved laser oscillator
device capable of avoiding a necessity of using large-size
complicated separate devices such as fan blowers unlike the prior
art, and capable of facilitating cooling replacement/substitution
of a laser medium by letting a discharge plasma exhibit convection
by use of the Lorentz force drive electromagnetic pump means,
provided internally or externally to the laser tube, such as a coil
or the like for application of a magnetic field to such laser
medium, and thereby capable of producing with no difficulties
high-output laser light by improving the laser oscillation
efficiency.
* * * * *