Coherent light generators – Particular resonant cavity – Specified cavity component
Reexamination Certificate
2000-07-26
2003-05-06
Tran, Minh Loan (Department: 2826)
Coherent light generators
Particular resonant cavity
Specified cavity component
C372S099000, C372S100000
Reexamination Certificate
active
06560269
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fluorine laser device, and particularly relates to a fluorine laser device in which a band of a wavelength is narrowed by a dispersion prism.
BACKGROUND ART
Band narrowing means for narrowing a band of a wavelength of laser light with use of a dispersion prism is conventionally known, and is shown, for example, in the reference, Canadian Journal of Physics, Vol. 63, PP. 214-219, 1985.
FIG. 21
shows a fluorine laser device in which the band of a wavelength is narrowed by using the band narrowing means which is disclosed in the aforementioned reference, and the prior art will be explained below based on FIG.
21
.
In
FIG. 21
, a fluorine laser device
1
includes a laser chamber
2
containing laser gas being a laser medium. High voltage is applied across discharge electrodes not illustrated which are placed inside the laser chamber
2
from a high-voltage power supply not illustrated, and discharge occurs across the discharge electrodes, thereby generating laser light
11
.
At both end portions of the laser chamber
2
, fixed are a front window
107
and a rear window
109
for transmitting the laser light
11
. In front of (right side of
FIG. 1
) and behind the laser chamber
2
, respectively placed are a front slit
116
and a rear slit
117
having a front opening
33
and a rear opening
34
each having a predetermined width.
In front of the front slit
116
, placed is a front mirror
8
for transmitting part of the laser light
11
at a predetermined transmissivity to emit it. Further, behind the rear slit
117
, disposed are two dispersion prisms
118
and
118
, and a rear mirror
106
for totally reflecting the laser light
11
is disposed behind the prisms
118
and
118
.
The laser light
11
oscillated inside the laser chamber
2
is transmitted through the rear window
109
, and passes through the rear opening
34
and the two prisms
118
and
118
. Subsequently, it is reflected at the rear mirror
106
, passes through the dispersion prisms
118
and
118
and the rear opening
34
once again, and is transmitted through the rear window
109
to return to the laser chamber
2
. The laser light
11
passes through the front window
107
and the front opening
33
, and is partly transmitted through the front mirror
8
to be emitted forward.
In this situation, in the laser light
11
oscillated inside the laser chamber
2
, high-power intense line light
11
A (wavelength 157.6299 nm) and low-power weak line light
11
B (wavelength 157.5233 nm) coexist. Since the intense line light
11
A and the weak line light
11
B have different wavelengths, refraction angles at which they enter and exit the dispersion prisms
118
and
118
differ from each other. As a result, while the intense line light
11
A and the weak line light
11
B are passing through the two dispersion prisms
118
and
118
, optical paths thereof deviate from each other little by little.
The intense line light
11
A passes through the rear opening
34
and the front opening
33
and is emitted from the front mirror
8
. On the other hand, the weak line light
11
B has its optical path deviated while it goes and returns through the two dispersion prisms
118
and
118
and is blocked by either the rear slit
117
or the front slit
116
, and as a result it is not oscillated. Thus, only the intense line light
11
A is oscillated, thereby narrowing the bandwidth of the wavelength of the laser light
11
.
However, the application of the band narrowing means with use of the above dispersion prisms
118
and
118
to the fluorine laser device
1
has the following disadvantages.
Specifically, during discharge to excite the laser medium, a spontaneous emission occurs in every direction from the excited fluorine from the fluorine laser device
1
. Of the above spontaneous emissions, those traveling in the same direction as the laser light
11
interact with a number of excited molecules and inductively emit a large quantity of photon. It is known that the spontaneous emissions traveling on approximately the same axis of the laser light
11
are intensified as a result of the above. The intensified spontaneous emission is called an amplified spontaneous emission
36
hereinafter.
As shown in
FIG. 21
, the amplified spontaneous emission
36
, for example, emitted rearward from the laser chamber
2
is hit against the slits
116
and
117
to be reflected since it has a larger broadening angle than the laser light
11
. In this situation, it sometimes happens that the amplified spontaneous emission
36
which is hit against the slits
116
and
117
is irregularly reflected and returns into the laser chamber
2
. As a result, part of discharge energy for amplifying the laser light
11
is spent to amplify the amplified spontaneous emission
36
once again, thus causing the disadvantage of reducing the power of the laser light
11
.
Further, it sometimes happens that the weak line light
11
B is irregularly reflected at the slit
16
and returns into the laser chamber
2
as the amplified spontaneous emission
36
, and is amplified again by discharge in the laser chamber
2
. Thus, the intense line light
11
A and the weak line light
11
B are mixed in the emitted laser light
11
to reduce the monochromatic property of the laser light
11
and the spectral width of the wavelength is increased. As a result, for example, when the laser light
11
is used for laser machining, there arises the disadvantage of machining accuracy being reduced.
SUMMARY OF THE INVENTION
The present invention is made to eliminate the above disadvantages of the prior art, and its object is to provide a fluorine laser device capable of obtaining high-power laser light with large monochromatic property.
In order to attain the above object, a first configuration of a fluorine laser device according to the present invention is in a fluorine laser device including
a laser chamber in which a laser medium including fluorine is contained and is excited to thereby oscillate laser light,
a front slit disposed in front of the laser chamber and having a front opening for transmitting the laser light, and
a rear slit disposed behind the laser chamber and having a rear opening for transmitting the laser light,
at least one of the front slit and the rear slit is a slit in which a slit inclined plane is formed on a surface at a laser chamber side to make one of the front opening and the rear opening convex.
According to the above configuration, amplified spontaneous emission generated inside the laser chamber hits against the slit inclined plane and is reflected in a direction away from the laser chamber, and thus less of it returns into the laser chamber. Accordingly, less of the amplified spontaneous emission is amplified, and the ratio of energy spent for oscillation of the laser light increases, thus increasing the power of the laser light.
Further, in the fluorine laser device, the slit with the slit inclined plane being formed may further have a slit inclined plane formed on a surface at an opposite side to the laser chamber to make one of the front opening and the rear opening convex.
According to the above configuration, weak line light, which is reflected, for example, at the rear mirror and the front mirror and returns in the direction of the laser chamber, hits against the slit inclined plane and is reflected in the direction away from the laser chamber. As a result, less of the weak line light returns into the laser chamber to be amplified again, and only intense line light is amplified and oscillated. Accordingly, the monochromatic property of the laser light is improved, and for example, when the laser light is used for laser machining, machining accuracy is improved. Further, the amplified spontaneous emission reflected, for example, at the rear mirror and the front mirror also hits against the slit inclined plane and is reflected in the direction away from the laser chamber, and thus less of it returns into the laser chamber.
Further, in the fluorine laser device, the slit with the sl
Ariga Tatsuya
Takehisa Kiwamu
Wakabayashi Osamu
Armstrong Westerman & Hattori, LLP.
Komatsu Ltd.
Tran Minh Loan
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