Coherent light generators – Particular beam control device – Q-switch
Reexamination Certificate
2000-01-05
2002-05-21
Font, Frank G. (Department: 2877)
Coherent light generators
Particular beam control device
Q-switch
C372S010000, C372S095000, C372S022000, C372S026000, C372S099000, C372S027000
Reexamination Certificate
active
06393034
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser apparatus and a laser machining apparatus of an intracavity wavelength conversion type, which converts a wavelength by placing a wavelength conversion crystal in a resonator.
2. Discussion of Background
FIG. 14
is a structural view of a conventional laser apparatus disclosed in JP-A-8-250797. In
FIG. 14
, numerical reference
25
designates a resonator mirror having a high reflectance with respect to a fundamental laser beam. Numerical references
2
c
,
2
d
designate solid-state laser active mediums. Numerical reference
9
a
designates a 90 degree polarization rotator. Numerical reference
4
b
designates a second harmonic generation wavelength conversion crystal. Numerical reference
6
b
designates a fundamental laser beam. Numerical reference
5
b
designates a laser optical axis of the fundamental laser beam. Numerical reference
3
b
designates a folding and outcoupling mirror having a high reflectance with respect to the fundamental laser beam and high transmittance with respect to the second harmonic laser beam. Numerical reference
26
designates a resonator mirror having a high reflectance with respect to the fundamental beam and second harmonic laser beam. The second harmonic generation wavelength conversion crystal
4
b
is provided with an optimum phase matching means by changing an angle and temperature of the frequency conversion crystal.
In the laser apparatus shown in
FIG. 14
, a part of the fundamental laser beam, which is generated by the mirrors
25
,
26
, the 90 degree polarization rotator
9
a
, and the solid-state laser active mediums
2
c
,
2
d
, is converted into a second harmonic laser beam by the second harmonic generation wavelength conversion crystal
4
b
placed inside of a resonator and extracted from a laser beam folding mirror
3
b
. In this laser apparatus, one of the resonator mirrors configurating the resonator is a convex mirror, and the other mirror
26
on a side close to the second harmonic generating wavelength conversion crystal
4
b
is a concave mirror. The second harmonic generation wavelength conversion crystal
4
b
is positioned where the diameter of the fundamental wave laser beam
6
b
is narrowed by a function of the resonator.
In the laser apparatus shown in
FIG. 14
, as the 90 degree polarization rotator
9
a is positioned between the laser active mediums
2
c
,
2
d
, it is possible to improve stability and efficiency of a laser system by compensating the birefringence and the bifocusing of the two laser active mediums.
FIG. 15
is a structural view showing a laser apparatus disclosed in “Solid State Laser Engineering” (3rd Edition) by W. Koechner. In
FIG. 15
, numerical reference
25
a
designates a resonator mirror having a concave curvature. Numerical reference
8
b
designates a resonator Q switching element. Numerical reference
2
e
designates a laser active medium. Numerical reference
5
c designates a laser optical axis of a fundamental wave laser beam. Numerical reference
3
c
designates a folding and outcoupling mirror, which has a high reflectance with respect to the fundamental wave laser beam and a high transmittance with respect to second harmonic laser beam. Numerical reference
4
c
designates a second harmonic generation wavelength conversion crystal. Numerical reference
26
a
designates a mirror having a concave curvature, the mirror has a high reflectance with respect to the fundamental wave-laser beam and the second harmonic laser beam. In this apparatus, the second harmonic generation wavelength conversion crystal
4
c
is positioned at where the fundamental laser beam is narrowed by a function of the laser resonator like the apparatus illustrated in FIG.
14
.
In a second harmonic laser beam generation apparatus constructed as in
FIG. 15
, a part of a fundamental Q pulse laser beam, which is generated by the resonator mirrors
25
a
,
26
a
, the reflective mirror
3
c
, the laser active medium
2
e
, and the Q-switching element
8
b
, is converted into second harmonic laser beam by the second harmonic generation wavelength conversion crystal
4
c
and extracted from the mirror
3
c.
In the laser systems, illustrated in
FIGS. 14 and 15
, the wavelength conversion crystal is positioned at where the laser beam diameter is narrowed in the vicinity of the concave mirror. As the wavelength conversion efficiency of the wavelength conversion crystal becomes high as the beam intensity increases, the wavelength conversion crystal is generally placed at where the laser beam is focused. A concave mirror is ordinarily used as the resonator mirror.
In thus constructed second harmonic laser beam generation apparatus, since the concave mirror is used as the resonator mirror, on at least a side in which the wavelength conversion crystal is positioned, the length of the resonator is increased, whereby a compact wavelength conversion laser apparatus could not be fabricated. Further, the resonator has low stability with respect to a vibration of the resonant mirror. Further, it is difficult to generate a wavelength conversion pulse laser beam with a narrow pulse width. In addition, when one tries to improve the output power and the efficiency of the system, wavelength conversion crystal is apt to be damaged. Meanwhile, in case that a wavelength conversion crystal having a small nonlinear constant is used, it is difficult to obtain high frequency conversion efficiency.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional laser apparatus and to provide an intracavity wavelength conversion laser apparatus, in which the pulse width is short; operation is easy; reproducibility and stability are excellent; a wavelength conversion crystal is less susceptible to damages; and the size is compact.
Another object of the present invention is to provide a wavelength conversion laser apparatus, which demonstrates high efficiency even in case when a wavelength conversion crystal has a small wavelength conversion coefficient.
Another object of the present invention is to provide a laser machining apparatus, which is easily and stably operated. And it is possible to process finely with high accuracy at high speed.
Another object of the present invention is to provide a laser apparatus, which is easily operated and could excite another laser system, stably and efficiently.
According to a first aspect of the present invention, there is provided a laser apparatus having a stable resonator and a mirror, wherein the stable resonator includes a solid-state laser active medium, a Q factor modulating element, and a wavelength conversion crystal, and the convex mirror positioned on a side in the vicinity of the wavelength conversion crystal.
According to a second aspect of the present invention, there is provided the laser apparatus according to the first aspect of the invention, wherein the wavelength conversion crystal for generating a second harmonic laser beam is a type II phase matching type LBO (LiB
3
O
5
) crystal.
According to a third aspect of the present invention, there is provided the laser apparatus according to the first and second aspects of the invention, wherein at least one polarization controlling element is inserted inside of the resonator.
According to a fourth aspect of the present invention, there is provided the laser apparatus according to the first through third aspects of the invention, wherein an output power of a wavelength converted Q pulse laser beam is 50W or more.
According to a fifth aspect of the present invention, there is provided a laser machining apparatus, wherein the wavelength converted laser beam, generated from the laser apparatuses, according to the first through fourth aspects of the invention is used for processing.
According to a sixth aspect of the present invention, there is provided the laser apparatus according to the first through fourth aspects of the invention, wherein the wavelength converted laser beam, g
Fujikawa Shuichi
Kojima Tetsuo
Konno Susumu
Flores-Ruiz Delma R.
Font Frank G.
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
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