Coherent light generators – Particular active media – Gas
Reexamination Certificate
2001-11-14
2003-10-28
Ip, Paul (Department: 2828)
Coherent light generators
Particular active media
Gas
C372S057000
Reexamination Certificate
active
06639929
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pulse oscillating gas laser device such as an excimer laser device.
BACKGROUND ART
In a pulse oscillating gas laser device such as an excimer laser device, it is conventionally known that shock waves and acoustic waves (hereinafter, generally referred to as shock waves) occur on the occasion of pulse discharge. Due to the shock waves, fluctuations occur to the density of a laser gas, and a beam profile, energy, and wavelength of laser light become unstable. The art of preventing this is disclosed in, for example, Japanese Patent Application Laid-open No. 4-328889.
FIG. 17
shows a detail view of an area near discharge electrodes of an excimer laser device
11
disclosed in Japanese Patent Application Laid-open No. 4-328889, and a prior art will be explained hereinafter based on FIG.
17
.
In
FIG. 17
, meal discharge electrodes
14
and
15
are placed to oppose each other inside a laser chamber
12
in which a laser gas is sealed. An upper cathode
15
is fixed to a cathode base
36
with insulating properties, and the cathode base
36
is fixed to the laser chamber
12
. A lower anode
14
is mounted on an anode base
40
electrically connected to the laser chamber
12
. The cathode
15
is electrically connected to a high voltage side HV of a high-voltage power source
23
, and the anode
14
and the laser chamber
12
are electrically connected to a grounding side GND of the high-voltage power source
23
. High voltage is applied between the discharge electrodes
14
and
15
from the high-voltage power source
23
to cause a primary discharge in a pulse form in a discharge space
37
, thereby causing laser light in the pulse form.
In this situation, a shock wave
41
occurs from the discharge space
37
as a result of the primary discharge. The shock wave
41
is reflected at components in the vicinity of the discharge electrodes
14
and
15
, and is returned to the discharge space
37
, whereby the density of a laser gas in the discharge space
37
fluctuates. As a result, the primary discharge becomes unstable, and the beam profile, energy stability, and wavelength stability of the laser light are disturbed. In order to prevent this, in the aforementioned Japanese Patent Application Laid-open No. 4-328889, porous ceramics
46
and
46
are fixed on the cathode base
36
and the anode base
40
, respectively. The porous ceramics
46
and
46
as described above absorb the shock wave
41
and prevent the shock wave
41
from returning to the discharge space
37
.
However, the aforementioned prior art has the disadvantages as described below.
Specifically, in
FIG. 17
, the cathode
15
and the laser chamber
12
are electrically insulated from each other, and on the occasion of primary discharge, a large potential difference occurs between them. Thus, creeping discharge sometimes occurs between the cathode
15
and the laser chamber
12
via the surface of the porous ceramic
46
. As a result, primary discharge is not carried out favorably, thus causing the disadvantages that the output of laser light is reduced and in an extreme instance, laser light is not generated. In order to avoid creeping discharge, it is advisable to make a distance between the cathode
15
and the laser chamber
12
longer, but this makes the excimer laser device
11
larger.
To prevent creeping discharge, the art of providing projections and depressions on the cathode base
36
to form a rib portion is known. According to this, the insulation distance between the cathode
15
and the laser chamber
12
is lengthened, and creeping discharge hardly occurs.
Further, in view of the demand for increase in the repetition frequency of laser oscillation in recent years, the need for reducing inductance of primary discharge arises. For this purpose, it is necessary to reduce an area of a current loop formed by a return plate (not shown) for electrically connecting the cathode
15
and the anode
14
, and the anode
14
and the laser chamber
12
. As a result, the distance between the cathode
15
and the laser chamber
12
is shortened, and the creeping discharge between the cathode
15
and the laser chamber
12
easily occurs. The aforementioned rib portions are also necessary to prevent this.
However, the phenomenon, in which shock waves
41
generating from the discharge space
37
enter the recessed portions of the rib portion and are reflected toward the discharge space
37
at a high reflectivity, sometimes occurs. Thus, there arises the disadvantage that the shock waves
41
make the beam profile, energy, and wavelength unstable as described above.
SUMMARY OF THE INVENTION
The present invention is made in view of the above-described disadvantages, and its object is to provide a pulse oscillating gas laser device which can reduce effects of shock waves caused by primary discharge and perform stable laser oscillation.
In order to attain the above-described object, a pulse oscillating gas laser of the present invention is a pulse oscillating gas laser device for exciting a laser gas by causing primary discharge in a pulse form between a pair of discharge electrodes opposing each other and oscillating laser light, and has the constitution in which
a rib portion with insulating properties for preventing creeping discharge is provided on a cathode base with insulating properties, to which the discharge electrode at a high voltage side of a pair of the discharge electrodes is fixed, and
a damping material for attenuating shock waves caused by the primary discharge is inserted in an inside of a groove portion between a raised portion of the rib portion and the high-voltage side discharge electrode.
According to the above constitution, the shock waves are attenuated favorably, and the rib portion with insulation properties makes it possible to prevent creeping discharge.
Further, in the pulse oscillating gas laser device,
the damping material may be inserted into a recessed portion of the rib portion.
According to the above constitution, the shock waves emitted to a distance from the discharge electrodes are also attenuated, and therefore the effect of the shock wave is reduced.
Furthermore, in the pulse oscillating gas laser device,
the damping material may be in close contact with a side face of the raised portion and a side face of the high-voltage side discharge electrode, and may be formed into a U-shape.
According to the above constitution, the shock waves reflected at the surface of the damping material can be also prevented from returning to the discharge space, and the shock waves can be attenuated at high efficiency.
Still further, in the pulse oscillating gas laser device, the damping material may be provided in close contact with the discharge electrode at a grounding side of a pair of the discharge electrodes.
According to the above constitution, the shock waves emitted toward both of the high-voltage side and grounding side are attenuated, and therefore the effect of the shock waves can be reduced.
Further, in the pulse oscillating gas laser device,
the damping material is a porous material with porosity of not less than 90%.
According to the above constitution, the porous material with high porosity is used, thus making it possible to attenuate the shock waves more efficiently.
REFERENCES:
patent: 5408490 (1995-04-01), Terai et al.
patent: 5771258 (1998-06-01), Morton et al.
patent: 5978405 (1999-11-01), Juhasz et al.
patent: 5991324 (1999-11-01), Knowles et al.
patent: 6023486 (2000-02-01), Hofmann et al.
patent: 6061376 (2000-05-01), Hofmann et al.
patent: 6430205 (2002-08-01), Bragin et al.
patent: 4-328889 (1992-11-01), None
Kakizaki Koji
Kataoka Naoki
Mizoguchi Hakaru
Saito Takashi
Armstrong Westerman & Hattori, LLP
Gigaphoton Inc.
Ip Paul
Vy Hung T
LandOfFree
Pulse oscillating gas laser device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pulse oscillating gas laser device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pulse oscillating gas laser device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3170804