U.S. patent application number 10/166591 was filed with the patent office on 2003-12-11 for closed-loop purging system for laser.
Invention is credited to Pang, Yang.
Application Number | 20030227957 10/166591 |
Document ID | / |
Family ID | 29710696 |
Filed Date | 2003-12-11 |
United States Patent
Application |
20030227957 |
Kind Code |
A1 |
Pang, Yang |
December 11, 2003 |
CLOSED-LOOP PURGING SYSTEM FOR LASER
Abstract
A method of operating a laser is disclosed. Components of the
laser are located in an enclosure, which may contain contaminants
including water vapor and organic vapor released by the optical
components, mounts of the optical components, or the enclosure
itself. The enclosure may also contain suspended particulate matter
and ozone. In order to reduce the level of these contaminants, a
purging system extracts gas from the enclosure and passes the gas
through a catalyst to decompose the ozone, a desiccant, an organic
vapor trapping material, and a particulate matter filter, then
returns the extracted gas to the enclosure. Decomposing ozone is
particularly important if the laser generates radiation at a
wavelength less than 250 nm.
Inventors: |
Pang, Yang; (San Jose,
CA) |
Correspondence
Address: |
STALLMAN & POLLOCK LLP
ATTN: MICHAEL A. STALLMAN
Suite 290
121 Spear Street
San Francisco
CA
94105
US
|
Family ID: |
29710696 |
Appl. No.: |
10/166591 |
Filed: |
June 10, 2002 |
Current U.S.
Class: |
372/59 |
Current CPC
Class: |
H01S 3/027 20130101;
B01D 53/8675 20130101; H01S 3/0346 20130101; G02F 2201/50 20130101;
G02F 1/3505 20210101; H01S 3/094053 20130101; H01S 3/09415
20130101 |
Class at
Publication: |
372/59 |
International
Class: |
H01S 003/22 |
Claims
What is claimed is:
1. A method of minimizing contamination of optical components of a
laser, the components being located in a gaseous atmosphere within
an enclosure, the gaseous atmosphere containing contaminants
including water vapor, organic vapor, ozone and suspended
particulate matter, the method comprising the steps of: (a)
extracting gas from the atmosphere within the enclosure; (b)
passing the extracted gas over a catalyst to convert the ozone into
oxygen; (c) following step (b) passing the extracted gas through a
first medium selected to reduce the water vapor content thereof;
(d) following step (c), passing the extracted gas through a second
medium selected to reduce the water vapor content thereof; (e)
following step (d) passing the extracted gas through a filter
selected to reduce the particulate matter content thereof; and (f)
following step (g), returning the extracted gas to the
enclosure.
2. The method of claim 1, wherein said catalyst is silver
oxide.
3. The method of claim 1, wherein said catalyst is manganese
oxide.
4. The method of claim 1, wherein said first medium is silica
gel.
5. The method of claim 1, wherein said second medium is activated
carbon.
6. The method of claim 1, wherein said second medium is a molecular
sieve.
7. The method of claim 1 wherein said filter is a HEPA filter.
8. A laser, comprising: an enclosure; a plurality of optical
components located in a gaseous atmosphere within said enclosure; a
gas conditioning arrangement including a catalyst for converting
ozone into oxygen, a desiccant medium, a medium for trapping
organic vapors, and a filter for trapping particulate matter, said
gas conditioning arrangement being in fluid communication with the
enclosure; and a pump arranged to extract gas from said enclosure
and deliver said extracted gas to said gas-conditioning arrangement
with said gas conditioning arrangement being configured such that
said extracted air delivered thereto passes through said catalyst,
said desiccant medium, said organic vapor trapping medium, and said
filter in the sequence listed and is then returned to said
enclosure.
9. The laser of claim 8, wherein said catalyst is silver oxide.
10. The method of claim 8, wherein said catalyst is manganese
oxide.
11. The laser of claim 8, wherein said desiccant medium is silica
gel.
12. The laser of claim 8, wherein said organic vapor trapping
medium is activated carbon.
13. The laser of claim 8, wherein said organic vapor trapping
medium is a molecular sieve.
14. The laser of claim 8, wherein said filter is a HEPA filter.
15. The laser of claim 8, further including a pair of conduits and
a pair of valves, said conduits and said valves arranged such that
a drying gas can be passed through said desiccant medium for
regenerating the desiccant medium while preventing said drying gas
from entering said enclosure.
16. A purging apparatus for a laser, the laser including a
plurality of optical components located in a gaseous atmosphere
within an enclosure, the apparatus comprising: a gas conditioning
arrangement including a catalyst for converting ozone into oxygen,
a desiccant medium, a medium for trapping organic vapors, and a
filter for trapping particulate matter; and a pump, said pump being
arranged to extract gas from said enclosure and deliver said
extracted gas to said gas-conditioning arrangement with said gas
conditioning arrangement being configured such that said extracted
air delivered thereto passes through said catalyst, said desiccant
medium, said organic vapor trapping medium, and said filter in the
sequence listed and is then returned to said enclosure.
17. The apparatus of claim 16, wherein said pump is arranged to
draw said extracted air through said catalyst such that said
extracted passes through said catalyst, then through said pump
before passing through said desiccant medium, said organic vapor
trapping medium, and said filter.
18. The apparatus of claim 16, wherein said catalyst is silver
oxide.
19. The apparatus of claim 16, wherein said catalyst is manganese
oxide.
20. The apparatus of claim 16, wherein said desiccant medium is
silica gel.
21. The apparatus of claim 16, wherein said organic vapor trapping
medium is activated carbon.
22. The apparatus of claim 16, wherein said organic vapor trapping
medium is a molecular sieve.
23. The apparatus of claim 16, wherein said filter is a HEPA
filter.
24. The purging apparatus of claim 16, further including first and
second valves, said first and second valves arranged such that a
drying gas may be circulated through said desiccant medium for
regenerating said desiccant medium while preventing said drying gas
from reaching said enclosure.
25. In a laser, housed in an enclosure having a gaseous atmosphere
therein, the laser generating ultraviolet radiation at a wavelength
less than 270 nm, and ozone being generated in the gaseous
atmosphere as a result of interaction of the ultraviolet radiation
therewith, a method of optimizing operation of the laser comprising
the steps of: (a) extracting gas from the atmosphere within the
enclosure; (b) passing the extracted gas over a catalyst to convert
the ozone into oxygen; and (c) following step (b), returning the
extracted gas to the enclosure.
26. The method of claim 25, wherein said catalyst is silver
oxide.
27. The method of claim 25, wherein said catalyst is manganese
oxide.
28. The method of claim 22 further including the step of (d)
purging the enclosure with an inert gas prior to step (a).
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates generally hermetic sealing of
lasers. The invention relates in particular to a closed-loop
purging system for ozone, water vapor, organic vapor and
particulate content in an enclosure surrounding an ultrafast laser
resonator or an ultraviolet (UV) laser resonator.
DISCUSSION OF BACKGROUND ART
[0002] Ultrafast lasers are generally regarded as being lasers that
deliver output radiation in pulses having a duration of a few
hundred femtoseconds or less. One common ultrafast laser is a
Ti:sapphire laser, which can be arranged to deliver output
radiation at wavelengths between about 700 nanometers (nm) and
about 1000 nm. The pulses delivered often have a relatively low
energy, for example, tens of millijoules (mJ) to as little as tens
of nanojoules (nJ). The short pulse-duration can cause the pulses
to have a very high peak power, for example, on the order of
gigawatts per square centimeter (GW/cm.sup.2) in certain locations
in a resonator.
[0003] The very high peak powers delivered by such lasers can
rapidly cause damage to optical components of the lasers, absent
measures to inhibit such damage. Laser damage to optical components
may be exacerbated by defects on or in optical surfaces of the
components. Accordingly, it is not unusual that at least some
portion of the optical components of an ultrafast laser are
generated by so-called super-polishing techniques which yield
surfaces having a surface smoothness of atomic dimensions, for
example, about 4 .ANG.ngstrom Units (.ANG.) root-mean-square (RMS)
or less. Optical coatings for such super-polished components,
reflective coatings in particular, are often deposited by ion-beam
sputtering (IBS). IBS is a coating deposition method that can
provide coatings having a high degree of chemical perfection and
very low defect content. This minimizes absorption and scattering
of radiation by the coatings. However, a super-polished, IBS-coated
optical component can be as much as about five or more times more
expensive than a similar component polished and coated by more
conventional methods. Such additional expense can be wasted if the
components are later contaminated by particulate matter,
condensates, vapors, or the like.
[0004] It is not unusual in commercial laser manufacture to
assemble lasers in clean-room conditions to minimize particulate
deposition on optical components of the lasers. In such a case, it
would be usual to place at least the optical resonator of the laser
in an enclosure sufficiently sealed to minimize, at least, ingress
of particulate contaminants, and preferably also, ingress of
contaminants in gaseous or vapor form. Such an enclosure may be
purged, before sealing, with filtered dry nitrogen, dry air or the
like.
[0005] By implementing one or more above-discussed measures during
manufacturing and assembly, an ultrafast laser may be operated for
a total of as long as several thousand hours before the performance
of the laser becomes significantly diminished by laser damage to
one or more optical components thereof. It is believed, however,
that even if an enclosure could be perfectly hermetically sealed,
damage to optical components may result from contamination of
optical components by outgassing products of the optical
components, adhesives and the enclosure itself. Outgassing products
can be generated while the laser is operating and also while the
laser is not operating.
[0006] It is believed that the most problematical of the outgassing
products are organic vapors, which can be released from material
such as adhesives, elastomer seals, and any plastic materials used
in the construction of the enclosure. Water vapor may also be
released from components of the enclosure or optics therein. The
water vapor and the organic vapors can condense directly on
surfaces of the optical components. The water vapor and organic
vapors together or in combination can react with laser radiation
while laser is operating. Products of the reactions can also
condense or be deposited on the optical surfaces. These reaction
products may include particulate matter such as carbon particles or
soot. Most of these reaction products, if condensed or deposited on
the optical surfaces can increase the vulnerability of the optical
surfaces to damage by the laser radiation application Ser. No.
09/901,857, filed Jul. 9, 2001, assigned to the assignee of the
present invention and incorporated herein by reference discloses
one arrangement for minimizing contamination of optical components
of a laser resonator. In this arrangement, a purging system
extracts gas from the enclosure and passes the gas through a
desiccant, an organic vapor trapping material, and a particulate
matter filter, then returns the extracted gas to the enclosure.
This arrangement has been found to be effective in removing most
reaction products of the interaction of laser radiation with
contaminants present in the enclosure as well as the contaminants
themselves. In instances where the laser resonator generates
ultraviolet laser radiation, however, it has been found that ozone
can be generated as a reaction product of the laser radiation with
oxygen or one or more contaminants. Ozone generation becomes
problematical when the ultraviolet radiation has a wavelength less
than 270 nm and becomes more problematical the shorter the
wavelength. The level of generated ozone is not significantly
reduced by the purging system and has been found to cause some
deterioration of resonator components and absorption of ultraviolet
radiation resulting in lowered power output.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a method of minimizing
contamination of optical components of a laser, the components
being located in a gaseous atmosphere within an enclosure. The
gaseous atmosphere can contain contaminants including water vapor,
organic vapor, and suspended particulate matter. These contaminants
may be present at some low level, for example, hundreds of parts
per billion or less, immediately after the components are placed in
the enclosure. The contaminant level can increase with both
operational and non-operational time of the laser. In a laser
system providing ultraviolet radiation the atmosphere in the
enclosure may include ozone generated as a result of interaction
between one or more of the contaminants and the ultraviolet
radiation.
[0008] In one aspect of the present invention, the method comprises
extracting gas from the atmosphere within the enclosure. The
extracted gas is passed through a catalyst to convert ozone into
oxygen, through a first medium selected to reduce the water vapor
content of the extracted gas; through a second medium selected to
reduce the organic vapor content of the extracted gas; and through
a filter selected to reduce the particulate matter content of the
extracted gas. After the extracted gas is passed through the
catalyst, the first and second media and the filter, it is returned
to the enclosure.
[0009] The extraction and replacement cycle preferably takes place
continuously during operation of the laser such that the water
vapor, organic vapor, and particulate matter content of the
atmosphere in the enclosure is maintained at a minimum consistent
with the selection of the media and the filter.
[0010] In another aspect of the invention, in an enclosure for a
laser generating radiation at a wavelength of less than 270 nm,
ozone generation can cause significant power loss, a problem that
cannot be adequately mitigated by filtering and vapor trapping
alone, or by pre-purging the enclosure with an inert gas.
Accordingly, in such an enclosure, the ozone removal of the present
invention is important as much for efficient operation of the laser
as for preventing progressive deterioration of laser
components.
[0011] In yet another aspect of the invention, apparatus for
carrying out the method includes a gas conditioning arrangement
including the catalyst, the first (a desiccant) medium, the second
(a medium for trapping organic vapors) medium, and the filter for
trapping particulate matter. The apparatus includes a pump, which
is arranged to extract gas from the enclosure and deliver the
extracted gas to the gas-conditioning arrangement. The gas
conditioning arrangement is configured such that the extracted air
is drawn by the pump over the catalyst, then urged by the pump
through the desiccant medium, the organic vapor trapping medium,
and the filter, and is subsequently returned to the enclosure.
[0012] In one preferred embodiment, the apparatus further includes
first and second valves. The first and second valves are arranged
such that a drying gas may be circulated through the desiccant
medium for regenerating the desiccant medium while preventing the
drying gas from reaching the enclosure.
[0013] Maintaining a low organic vapor content in a laser resonator
is particularly important if the laser resonator is an ultrafast
laser resonator or a laser resonator arranged to generate
ultraviolet laser radiation. The relatively high-energy of
ultraviolet laser radiation, multiphoton processes in the case of
ultrafast lasers, generating longer wavelength radiation can
increase the probability of reactions between the laser radiation
and the organic vapors or their condensates. As noted above,
products of these reactions, including particulate matter, can lead
to unstable operation of the laser, or accelerated damage to
optical components of the laser resonator.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 schematically illustrates an ultrafast laser
including an enclosure housing a laser resonator including a solid
state gain medium and two optically nonlinear crystals, a source of
optical pump light for optically pumping the solid-state
gain-medium, a controller, and a purging system in accordance with
the present invention for minimizing contaminants in the
enclosure.
[0015] FIG. 2 schematically illustrates one preferred embodiment of
the purging system of FIG. 1.
[0016] FIG. 3 schematically illustrates another preferred
embodiment of the purging system of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Referring now to FIG. 1, laser 20 includes a laser resonator
22, a source 24 of optical pump light, and a purging system 26 in
accordance with the present invention. In this example, laser
resonator 22 is a solid-state laser resonator including a
solid-state gain-medium radiation 28 for generating fundamental
radiation at a wavelength of about 1064 nanometers (nm). Resonator
22 is formed between mirrors 30 and 32. Preferred gain-media for
generating radiation at this wavelength are neodymium-doped YAG
(Nd:YAG) and neodymium-doped yttrium orthovanadate (Nd:YVO.sub.4).
Light source 24, in this example, is a diode-laser array providing
optical pump radiation at a wavelength of about 808 nm. The pump
light is transmitted via an optical fiber bundle 34, then focused
by a lens 35 through mirror 30 into gain medium 28 as indicated by
broken lines P.
[0018] Fundamental radiation circulates in resonator 22 as
indicated by arrows F. Fundamental radiation is delivered from the
resonator in the form of pulses the delivery of which is controlled
by a Q-switch 36. Pulses delivered by the resonator are first
doubled in frequency by an optically nonlinear crystal 38. The
frequency-doubled radiation is designated by arrow 2F.
Frequency-doubled radiation 2F is directed into another
optically-nonlinear crystal 40 to provide frequency quadrupled
radiation 4F having a wavelength of about 266 nm, a wavelength in
the ultraviolet region of the electromagnetic spectrum. It is
believed that the actual threshold (longest) wavelength for ozone
generation is dependent on the actual pulse power with higher pulse
powers having a longer threshold wavelength.
[0019] Laser resonator 22 and components thereof are located,
together with optically nonlinear crystals 38 and 40, in an
enclosure 42. The purging system 26 extracts the atmosphere
(including contaminant gases vapors and particulates suspended
therein) from enclosure 42 via a conduit 44, treats the extracted
atmosphere to remove the contaminants, and returns the treated
atmosphere to enclosure 42 via a conduit 46. The manner of treating
the contaminated atmosphere is described in detail further
hereinbelow. Frequency quadrupled radiation 4F is delivered from
the enclosure via a window 48 therein. A portion of the radiation
is sampled by a beamsplitter 49 and directed to a detector 51 for
measuring laser output power.
[0020] Laser 20 includes a controller 50 arranged to control
operations and parameters the laser resonator, the pump light
source, and the purging system. Controller 50 controls operations
of purging system 26 via electrical connections 52, 54, and 56. The
controller controls operations and parameters of laser resonator 22
via electrical connections 58 and 60. Connection 58 connects
Q-switch 36 to the controller for controlling pulse repetition
rate. Connection 60 connects detector 51 to the controller for
monitoring power output. Connection 62 connects the controller to
diode-laser array 24 for controlling pump power delivered to gain
medium 28 and ultimately, cooperative with signals from detector
21, controlling power output of laser 20. Purging system 26 also
includes conduits 64, 65, 66, and 68. Conduits 66 and 68 connect
with a desiccant module (not shown in FIG. 1) in the purging
system.
[0021] The interior (atmosphere) 42A of enclosure 42 is maintained
at about ambient atmospheric pressure. The atmosphere of enclosure
42 will usually be an air atmosphere. Before connecting and
operating purging system 26, enclosure 42 may be flushed with an
inert gas such as nitrogen to remove the bulk of contaminants
resulting from manufacture, mounting and assembly of components,
and to reduce the oxygen content of the atmosphere. Conduits 64 and
65 provide access for purging enclosure 42 with an inert gas or the
like.
[0022] Whatever the gaseous atmosphere of enclosure 42, after this
initial flushing, it can be expected to include some finite level
of contaminants, however small that level. As noted above,
particulate matter may include particulate matter that was present
at the time that the enclosure was closed, and particulate matter
generated as a result of interaction between laser radiation
circulating in resonant cavity 52 and the organic vapors. In a
laser generating ultraviolet radiation, ozone may be generated by
interaction of the ultraviolet radiation with oxygen or hydrocarbon
vapors in the atmosphere
[0023] Referring now to FIG. 2, one preferred embodiment 26A of a
purging system 26 in accordance with the present invention includes
a pump 72 and a gas conditioning arrangement. The gas conditioning
arrangement includes a container 76 containing a desiccant material
78, a container 80 including an organic vapor trapping material 82,
a filter unit 84 for filtering particulate matter, and a container
86 containing a catalyst 88 for converting ozone into oxygen.
[0024] Desiccant material 78 is preferably silica gel, but may be
any desiccant material. A preferred organic vapor trapping material
82 is a high surface-area, coconut-shell based, activated carbon.
Organic vapor traps including this material are available in
various sizes from Agilent Technologies, Inc. of Palo Alto, Calif.
Other suitable organic vapor trapping materials include a 5 .ANG.
molecular sieve. Filter unit 84 is preferably capable of trapping
particles having a size of about 0.5 micrometers (.mu.m) and
greater, for example, a HEPA filter. One suitable HEPA filter is
available from the Pall Gellman Sciences Inc. of Ann Arbor, Mich.
as HEPA Capsule Part No. 12144. This filter has a pore size of 0.3
.mu.m and has a filtering efficiency of 99.97% for 0.3 .mu.m DOP
aerosol. Catalyst 88 is preferably silver oxide. The catalyst
catalyzes a reaction that converts two molecules of ozone into
three molecules of oxygen. Manganese oxide is another suitable
catalyst for catalyzing this reaction. The catalyst is not consumed
in the reaction.
[0025] Pump 72 extracts gas from the atmosphere of enclosure 42 via
conduit 44. The pump draws the extracted gas via two-way valves 91
and 92 through catalyst 88 in container 86 to convert any ozone
therein into oxygen. The circulation direction of gas through the
purging system is indicated in FIG. 2 by arrows A. The gas is urged
by pump 72 via a conduit 90 and a two-way valve 94 through
desiccant material (medium) 78 in container 76; through a conduit
96; through another two-way valve 98; and then through organic
vapor trapping material 82. After passing through the organic vapor
trapping material, the gas passes through HEPA filter 84 into
conduit 46, which returns the gas to enclosure 42. As noted above,
desiccant material 78 reduces the water vapor content of the gas,
and organic vapor trapping material 82 reduces the organic vapor
content of the gas. HEPA filter 114 reduces the particulate matter
content of the gas. Valves 91, 92, 94, and 98 in this mode of
operation prevent any of the extracted gas from escaping the
purging system via conduits 64, 66, and 68.
[0026] In one preferred cycle of operation of purging system 26A,
the extraction and return of gas from and to the enclosure takes
place continually during any period in which laser 20 is operating.
Operation of the purging system is started and stopped by
correspondingly starting or stopping pump 72 by commands delivered
thereto from controller 50 via electrical connection 56. Continuous
operation of purging system 26A can provide that in the atmosphere
of enclosure 42, the ozone, water vapor, organic vapor, and
particulate matter content of the atmosphere are maintained at a
minimum consistent with the materials and configuration of the gas
conditioning arrangement. It is possible, of course, that the
inventive purging system could be activated and deactivated by
controller 50 based on measurements of particle count or
concentrations of particular vapor species. This, however, would
require providing corresponding sensors, which could increase the
cost of a laser or the purging system.
[0027] After a period of operation, depending on the ambient
atmosphere in which laser 20 is located, or the conditions of
operation of the laser, desiccant material 78 may become saturated
with water vapor. Should this occur, desiccant material 78 may be
revived or regenerated by passing a drying gas, such as dry air or
dry nitrogen, through the material, as follows.
[0028] Operation of pump 72 is stopped. Valve 94 is switched to
prevent air from being delivered from pump 72 to the desiccant
material, and to allow the drying gas to be delivered to the
desiccant material via conduit 66. Valve 98 is switched to prevent
any drying gas from reaching enclosure 42 via the organic vapor
trapping material, the HEPA filter, and conduit 46. This switching
allows drying gas delivered to the desiccant material via conduit
66 to pass through the desiccant material and exit the purging
system via conduit 68 as indicated in FIG. 3 by arrows D. After the
desiccant material has been regenerated, valves 94 and 98 are
switched back to a position that allows gas extracted from
enclosure 42 to pass to the gas conditioning system and return to
the enclosure via conduit 46. Valves 94 and 98 may be operated by
commands delivered thereto along connections 52 and 54 from
controller 50.
[0029] In order to further minimize ozone content of enclosure 42
during operation it can be advantageous to initially purge
enclosure 42 with an inert gas such as nitrogen. This can be
accomplished in purging system 26A by connecting a nitrogen source
to conduit 65 and operating pump 72 and valves 91, 92, 94 and 96
such that the nitrogen is urged through the gas conditioning system
and enclosure 42 to expel the original atmosphere of the enclosure
via conduit 64. Valves 91 and 92 are operated manually for this
procedure in purging system 26A. Provision can be made, however,
for operation of the valves by controller 50.
[0030] Another preferred embodiment 26B of a purging system in
accordance with the present invention is depicted in FIG. 3.
Purging system 26B is similar to purging system 26A of FIG. 3 with
an exception that desiccant material 78 and organic vapor trapping
material 82 are contained in a single container 100. A permeable
diaphragm or separator 102 separates the desiccant material from
the organic vapor trapping material. One such combined desiccant
and organic vapor trapping unit is available from the W. A. Hammond
Drierite Company Ltd of Xenia, Ohio as Part No.27068.
[0031] It is emphasized here that the sequence of vapor reduction
and filtering is particularly important in the method and apparatus
of the present invention. If water vapor reduction does not precede
organic vapor reduction there could be a significant degradation in
the efficiency of organic vapor reduction. As there is a
possibility that water vapor removal materials and organic vapor
trapping materials can generate particulate matter, it is important
that particulate matter filtering takes place following water vapor
reduction and organic vapor reduction. It is also important that
conversion of ozone in extracted gas into oxygen takes place before
the extracted gas passes through pump 72. This minimizes to
possibility of corrosion of the pump by the ozone.
[0032] In the description of laser 20 given above, laser resonator
22, controller 50, and purging system 26 are described as separate
units. This arrangement should not be construed as limiting the
present invention. By way of example, as the size of the purging
system can be relatively small compared with the laser resonator,
the purging system and the laser resonator may be combined in a
single unit or housing. Alternatively, the purging system may be
combined in a single housing with the controller. In another
arrangement, purging system 26 may be configured as a stand-alone
module including a dedicated controller separate from controller
50. One skilled in the art to which the present invention pertains
may devise other configurations of the purging system, the laser
resonator and one or more controllers without departing from the
spirit and scope of the present invention.
[0033] The purging system of present invention is described above
with reference to its use with a pulsed, frequency-tripled,
solid-state laser. This should not be construed as limiting the
present invention. The inventive purging system is applicable to
other lasers such as solid-state ultrafast lasers and ultrafast
lasers including dyes or semiconductor materials as gain media. As
noted above, the very high-power and short duration of ultrafast
laser pulses can increase the possibility of the ultrafast laser
radiation reacting with any organic contaminants that may be found
in the atmosphere in the resonant cavity of the laser. Also as
noted above, the inventive purging system is particularly useful in
ultraviolet lasers where the high-energy of the ultraviolet
radiation also increases the possibility of reactions with any
organic contaminants in the laser resonator. Costs permitting,
however, it may be found useful to use the inventive purging system
with any other laser with the goal of extending the operating
lifetime of optical components or reliability of operation of the
laser.
[0034] The present invention is described above in terms of a
preferred and other embodiments. The invention is not limited,
however, to the embodiments described and depicted herein. Rather,
the invention is limited only by the claims appended hereto.
* * * * *