JPH053354A - Gas laser device - Google Patents

Abstract

PURPOSE:To prevent the adhesion of dust to the window members of an airtight container through which laser light is passed by providing a light transmissive shielding member which is tilted between the window members and communicating internal sections partitioned by means of the shielding member with each other. CONSTITUTION:A main electrode 9 which excites a gas laser medium by discharge to emit laser light is provided in an airtight container 1 in which the gas laser medium is contained and airtight window members 5 are put on openings at both ends in the axial direction of the container 1. A light transmissive shielding member 16 which is tilted at a Brewster angle or an angle near Brewster angle in the direction perpendicular to the axial direction of the container 1 is provided between the members 5. Then space sections 17 and 18 partitioned by the member 16 in the container 1 are communicated with another through a communicating vessel 19. Therefore, adhesion of dust to the window members 5 can be prevented by means of the shielding member 16 and, at the same time, the time required for cleaning the members 5 by removing the members 5 can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas laser device which excites a gas laser medium by discharge to generate laser light.

[0002]

_2. Description of the Related Art For example, a CO ₂ laser or an excimer laser is used.
A gas laser device such as a laser has an airtight container in which a gas laser medium is housed. A main electrode is arranged in this airtight container. When electrical energy is applied between the main electrodes to generate a glow discharge, the gas laser medium is excited to generate laser light.

Openings are formed on both end surfaces in the axial direction of the airtight container, and the openings transmit laser light.
For example, it is hermetically closed by a window member formed of a translucent material such as CaF ₂ . A high reflection mirror is arranged to face one of the window members, and an output mirror forming an optical resonator with the high reflection mirror is arranged to face the other window member. The laser light generated by the discharge excitation of the gas laser medium is amplified by the optical resonator and oscillated from the output mirror.

A gas laser device having such a structure,
For example, in the excimer laser, when the laser light passes through the window member, the photon energy is large, so that the outermost shell molecule of the molecules of the window member pops out. Therefore, it is considered that the portion of the window member through which the laser light is transmitted is positively charged. Since the window member made of CaF ₂ is an insulator, the portion of the window member through which the laser light is transmitted remains positively charged.

On the other hand, a large amount of dust generated by electric discharge exists inside the airtight container. These dusts are attracted to and adhere to the portion of the surface of the window member where the laser light, which is a charged portion, is transmitted. As a result, the window member becomes dirty and the transmittance of laser light is reduced, resulting in a reduction in output.

In order to prevent such a decrease in the laser light output, the window member must be removed for cleaning. However, it is not easy to remove and clean the window member, and it is not easy to return the airtight container whose airtight state has been broken to the original airtight state. Therefore, it is required to remove and clean the window member as often as possible.

Further, in the gas laser device, normally,
The output is detected by branching and monitoring a part of the laser light emitted from the window member.
However, if the laser light emitted from the window member is branched and monitored, an optical member for branching the laser light is required, or the size of the entire device is increased. is there.

[0008]

As described above, in the conventional gas laser apparatus, since the window member is easily soiled, the window member may be frequently removed from the airtight container and cleaned, and the laser may be removed. In order to monitor the light, it was necessary to use a dedicated optical member. A first object of the present invention is to provide a gas laser device in which the window member is resistant to dirt.

A second object of the present invention is that even if a part of the window member is contaminated, the uncontaminated portion can be exposed to the optical path of the laser light by sliding the window member. Another object of the present invention is to provide a gas laser device.

A third object of the present invention is to provide a gas laser device capable of preventing the window member from being contaminated and monitoring laser light without branching.

[0011]

In order to solve the above-mentioned problems, the first means of the present invention is to provide an airtight container in which a gas laser medium is housed, and the gas laser installed in the airtight container.
A main electrode that excites the laser medium to generate laser light;
Window members airtightly provided in openings at both axial ends of the airtight container, and a Brewster's angle or a greater angle inwardly of the window member of the airtight container with respect to a direction orthogonal to the axis. A light-transmitting shielding member that is inclined with respect to each other, and a communication unit that communicates one space portion and the other space portion inside the airtight container partitioned by the shielding member. To do.

A second means of the present invention is an airtight container for accommodating a gas laser medium, and a main electrode provided in the airtight container for exciting the gas laser medium by discharge to generate laser light. A window member airtightly provided at each of the openings at both axial ends of the airtight container, and an inner portion of the window member of the airtight container communicating with the inner space of the airtight container and in the axial direction of the airtight container. And a housing part formed so as to intersect with the housing part, and a part of the housing part is made to face the space in the airtight container and is inclined at a Brewster angle or more with respect to a direction orthogonal to the axis. A light-transmitting shield member slidably provided, and a communicating means for communicating one space portion and the other space portion inside the airtight container partitioned by the shield member. To do.

A third means of the present invention is an airtight container for accommodating a gas laser medium, and a main electrode provided in the airtight container for exciting the gas laser medium by discharge to generate laser light. A window member airtightly provided in each of the openings at both axial ends of the airtight container, and a Brewster angle or more inwardly of the window member of the airtight container in a direction orthogonal to the axis. The light-transmitting shield member inclined at an angle of, and the ray sequentially reflected by the inner surface of the window member and one surface of the shield member facing the window member.
It is characterized by comprising a lead-out section for leading the laser light to the outside of the airtight container, and a detection means for detecting the intensity of the laser light led out from the lead-out section.

[0014]

According to the first means described above, not only can the dust be prevented from adhering to the window member by the shielding member, but also the shielding member can be inclined at a Brewster's angle or a larger angle. As a result, the energy density of the laser light transmitted through the shielding member becomes low, so that dust is unlikely to adhere to this shielding member. According to the above-mentioned second means, by sliding the shielding member, it is possible to sequentially position the portions to which dust is not attached in the optical path of the laser light. According to the third means, the intensity of laser light can be monitored by using a dedicated optical component without branching.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show a first embodiment of the present invention, and FIG. 2 shows, for example, a KrF excimer laser as a gas laser device. This excimer laser is provided with an airtight container 1 in which a gas laser medium in which krypton, fluorine and helium are mixed is sealed at a pressure higher than atmospheric pressure. The airtight container 1 is composed of a main body 2 and a pair of thin tube portions 3 projecting from both ends of the main body 2 in the direction of the axis O (which coincides with the optical axis of the laser light L described later). There is. The pair of thin tube portions 3 are provided with their axes aligned with the main body portion 2.

A mounting flange 4 is provided on the protruding end of each thin tube portion 3.
Is 5 to 1 with respect to a perpendicular line S orthogonal to the axis O of the airtight container 1.
It is tilted at an angle of 0 degree. A window member 5 made of a material such as CaF ₂ is joined to the mounting flange 4 via an O-ring 6. The window member 5 is held by a holding flange 8 fixed to the mounting flange 4 by a screw 7. Thereby, the open end of the thin tube portion 3 is hermetically closed.

A pair of main electrodes 9 are arranged in the main body 2 so as to face each other in a direction orthogonal to the direction of the axis O of the airtight container 1. These main electrodes 9 are connected to a high voltage power source (not shown). When electric energy is supplied to the main electrodes 9 from the high-voltage power source, a glow discharge is generated between the main electrodes 9 to excite the gas laser medium and laser light L is generated.

A highly reflective mirror-1 is provided on one of the pair of window members 5.
1 are arranged to face each other, and the output mirror is provided on the other window member 5.
12 are arranged facing each other, and these mirrors 11 and 12 form an optical resonator.

Laser light L generated in the airtight container 1
Is repeatedly reflected by the high-reflecting mirror 11 and the output mirror 12 and amplified, and when the intensity reaches a predetermined level, the output mirror 12 oscillates.

Inside the thin tube portion 3, a first engaging portion 13 is formed in the upper portion on the base end side, and a second engaging portion 14 is formed in the lower portion on the tip end side. Each of the engaging portions 13 and 14 is composed of an L-shaped piece 15a and a pressing projection 15b protrudingly provided on the open end side of the L-shaped piece 15a. A shielding member 16 formed in a thin plate shape by a material that transmits the laser light L such as CaF ₂ is engaged with the engaging portions 13 and 14 at one end and the other end, respectively. Is held. The inclination angle B (shown in FIG. 1) of the shielding member 16 with respect to the perpendicular line S is set to be Brewster's angle (56 degrees in this case) or an angle in the vicinity thereof.

The protrusion 15b of the second engaging portion 14 is formed by a vibrating element 15c such as a piezoelectric element. The vibrating element 15c is connected to the power feeding portion 15d and is operated by a control signal from the power feeding portion 15d. When the vibrating element 15c operates, the shielding member 16 having one end joined to the vibrating element 15c vibrates. As a result, the dust attached to the shielding member 16 can be removed.

The inside of the thin tube portion 3 is divided by the shielding member 16 into a first space portion 17 communicating with the main body portion 2 side and a second space portion 18 on the window member 5 side. The first space portion 17 and the second space portion 18 are connected by a communication pipe 19. That is, one end of the communication pipe 19 is connected to the end face of the main body portion 2 and the other end thereof is connected to a portion of the thin pipe portion 3 corresponding to the second space portion 18. Communication pipe 19
A filter 21 is provided at one end of the. The filter 21 blocks dust generated by discharge of the main electrode 9 in the main body 2 from flowing into the second space 18 through the communication pipe 19.

One end of a lead-out pipe 22 inclined at a predetermined angle is connected to one of the thin tube portions 3 at a position corresponding to the second space portion 18. The inclination angle of the lead-out tube 22 is such that the reflected laser light L'transmitted through the shield member 16 and sequentially reflected by the inner surface of the window member 5 and one side surface of the shield member 16 opposite to the inner surface of the window member 5 is. The incident angle is set.
The light quantity of the reflected laser light L ′ incident on the lead-out tube 22 is
It is determined by the reflectance of the window member 5.

The open end of the lead-out tube 22 is hermetically closed by a transparent member 23. The reflected laser light L'transmitted through the transparent member 23 is detected by a sensor 24 such as a photodiode. The electric signal from the sensor 24 is input to the monitor 25. The monitor 25 displays the intensity of the reflected laser light L '.

Next, the operation of the gas laser device having the above construction will be described. When the laser light L is generated by supplying electric energy to the main electrode 9 to generate a discharge and discharge-exciting the gas laser medium in the airtight container 1, the laser light L is generated.
The light L passes through each window member 5, and is repeatedly reflected and amplified by the high-reflection mirror 11 and the output mirror 12 that form an optical resonator that is arranged to face each window member 5. When the laser light L reaches a predetermined intensity, the output mirror 12
Is oscillated from.

When a discharge is generated in the main electrode 9, dust is generated in the first space 17 on the main body 2 side of the airtight container 1 due to the discharge or the like. However, the dust generated in the first space portion 17 of the main body portion 2 is prevented from flowing into the second space portion 18 on the window member 5 side by the shield member 16 provided in the pair of thin tube portions 3. It Therefore, since dust generated by discharge or the like does not adhere to the inner surface of the window member 5, it is possible to prevent a decrease in output due to a decrease in the transmittance of the laser light L.

The dust generated in the main body 2 adheres to the surface of the shielding member 16 facing the first space 17 side. However, the shielding member 16 is provided so as to be inclined at a Brewster's angle or a larger angle. Therefore, the laser light L transmitted through the shielding member 16
The power density per unit area is extremely smaller than that of the window member 5. If the power density of the laser light L transmitted through the shield member 16 is small, plasma is less likely to be generated in the shield member 16, and therefore charging is hardly caused. Therefore, dust is less likely to adhere to the shielding member 16, so that the transmittance of the laser light L does not decrease for a long time.

The intensity of the laser light L transmitted through the shielding member 16 is detected by the monitor 25. That is, a part of the laser light L transmitted through the shielding member 16 is sequentially reflected by the inner surface of the window member 5 and one side surface of the shielding member 16 facing the inner surface. The reflected laser light L'is incident on the sensor 24 through the lead-out tube 22, the output thereof is detected, and the monitor 2
It is displayed in 5.

The intensity of the reflected laser light L'is reflected by the inner surface of the window member 5 which is not contaminated by dust and the one side surface of the shielding member 16 facing the second space portion 18 side. Is detected by the sensor 24. Therefore, the intensity of the reflected laser light L'is proportional to the intensity of the laser light L that is transmitted through the window member 5 and is not polluted by dust. By monitoring, the intensity of the laser light L can be accurately detected.

That is, since a part of the laser light L can be monitored by using the shielding member 16 for preventing the window member 5 from being soiled, the laser light L is used by using a dedicated optical component.
Of the laser light L'used in the monitor is in proportion to the intensity of the laser light L emitted from the window member 5, and therefore the laser is not branched. The intensity of the light L can be accurately detected.

On the other hand, dust is adhered to the surface of the shielding member 16 on the side of the first space 17 due to long-term use, and the residue may be discharged.
The output of the light L may decrease. In such a case, the second engaging portion 14 supporting one end of the shielding member 16
The vibrating element 15c forming the protrusion 15b is activated to vibrate the shielding member 16. As a result, the dust attached to the surface of the shielding member 16 facing the first space portion 17 can be dropped, so that the output of the laser light L can be recovered.

The window member 5 and the shielding member 16 may be removed and cleaned only when the output of the laser light L is not recovered even when the shielding member 16 is vibrated.
Therefore, the period (time) in which the window member 5 and the shielding member 16 have to be removed and cleaning can be made sufficiently long.

The first space portion 17 and the second space portion 18 in the thin tube portion 3 separated by the shielding member 16 are connected by a communication pipe 19. Therefore, when the laser medium is filled in the airtight container 1, there is no pressure difference between the first space portion 17 and the second space portion 18,
The shielding member 16 is not damaged. Moreover, since the filter 21 is provided at one end of the communication pipe 19, dust generated by the discharge is generated in the second space 1.
It does not flow into 8.

On the other hand, according to the experiment, the angle of inclination of the shielding member 16 with respect to the vertical line S is 80 or more which is greater than Brewster's angle.
When set to 1 degree, the dirt on the shielding member 16 is about one fifth of the dirt on the window member 5 without the shielding member 16.
It was confirmed to be reduced to. This is the shielding member 16
The power density per unit area of the laser light L transmitted through is 5
It is considered that this is because it is reduced to one-half.

FIGS. 3 and 4 show a second embodiment of the present invention. In the second embodiment, thin plate members 31 are provided on both sides of the thin tube portion 3 so as to project therefrom. One end of each of the plate-like bodies 31 communicates with the inside of the thin tube portion 3 and has a slit-shaped accommodating portion 3.
2 is inclined with respect to a perpendicular line S orthogonal to the axis O of the airtight container 1 at a Brewster angle or an angle in the vicinity thereof. A shielding member 16a formed in a rectangular plate shape that is sufficiently larger than the cross-sectional area of the internal space of the thin tube portion 3 is slid in the housing portion 32 so that a part of the shielding member 16a faces the optical path of the laser light L. It is freely accommodated.

At one end of the accommodating portion 32, the shield member 1 is provided.
A drive member 33 is provided in contact with one end of 6a. The driving member 33 is formed of, for example, a bimetal in an arc shape, and is gradually curved to have a large curvature by being electrically heated. Thereby, the shielding member 16a
Can be slid in the direction indicated by the arrow in FIG.

According to this structure, when the intensity of the laser light L detected by the monitor 25 is lowered,
The drive member 33 is electrically heated to slide the shield member 16a. As a result, the dust-free portion of the shielding member 16a can be exposed to the optical path of the laser light L of the thin tube portion 3, so that the output of the laser light L can be restored.

That is, since the shielding member 16a is slid by a predetermined size each time the output of the laser light L is reduced, the output can be recovered, so that the window member 5 is provided.
It is possible to sufficiently lengthen the cycle in which cleaning must be performed by removing.

[0040]

As described above, according to the first configuration of the present invention, it is possible to prevent dust from adhering to the window member by the shield member, and the shield member has almost the Brewster angle or the same. Since it is provided so as to be inclined at an angle in the vicinity, it is possible to reduce the power density of laser light per unit area in the shielding member and reduce the charging due to the generation of plasma. Since the adhesion can be reduced, the cleaning without removing the window member for a long time is not required.

Further, according to the second aspect of the present invention, since the shielding member is slidably provided, when the dust adheres to the shielding member and the output decreases, the shielding member is slid. The output can be recovered by exposing a new portion to the optical path of the laser light. Therefore, also in this case, cleaning without removing the window member is not required for a long time.

Further, according to the third aspect of the present invention, a part of the laser light reflected on the inner surface of the window member is led out to the outside by using the shielding member and is thus monitored. In addition to requiring no dedicated optical component, the intensity of laser light reflected by the inner surface of the window member and the shielding member is proportional to the intensity of laser light transmitted through the window member. You can monitor the light accurately.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a thin tube portion of an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of the entire gas laser apparatus.

FIG. 3 is an enlarged sectional view of a thin tube portion showing another embodiment of the present invention.

FIG. 4 is a plan view of the same.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Airtight container, 5 ... Window member, 9 ... Main electrode, 16 and 16a
... Shielding member, 17 ... First space part, 18 ... Second space part, 19 ... Communication pipe, 22 ... Outlet pipe (outlet part), 24 ... Sensor (detection means).

Claims (3)

[Claims] 1. An airtight container in which a gas laser medium is housed, a main electrode which is provided in the airtight container and discharges the gas laser medium to generate laser light, and an axis line of the airtight container. A window member provided airtightly at each of the openings at both ends in the direction, and provided inwardly of the window member of the airtight container with a Brewster angle or an angle in the vicinity thereof with respect to a direction orthogonal to the axis. A gas laser device, comprising: a light-transmitting shielding member; and a communicating means for communicating one space portion and the other space portion inside the airtight container partitioned by the shielding member. 2. An airtight container containing a gas laser medium, a main electrode provided in the airtight container to excite the gas laser medium to generate laser light, and an axis line of the airtight container. A window member is provided at each of the openings at both ends in the direction airtightly, and is formed in an inner portion of the window member of the airtight container so as to communicate with the internal space of the airtight container and intersect the axial direction of the airtight container. A housing part and a transparent part slidably provided so that a part of the housing part faces the internal space of the airtight container and is tilted at a Brewster angle or an angle in the vicinity thereof with respect to a direction orthogonal to the axis. A gas laser device comprising: a light-shielding member; and a communicating means for communicating one space portion and the other space portion inside the airtight container partitioned by this shielding member. 3. An airtight container containing a gas laser medium, a main electrode provided in the airtight container for exciting the gas laser medium by discharge to generate laser light, and an axis line of the airtight container. A window member provided airtightly at each of the openings at both ends in the direction, and provided inwardly of the window member of the airtight container with a Brewster angle or an angle in the vicinity thereof with respect to a direction orthogonal to the axis. A translucent shield member, and a lead-out portion for leading out the laser light sequentially reflected by the inner surface of the window member and one surface of the shield member facing the window member to the outside of the hermetic container, A gas laser device, comprising: a detector for detecting the intensity of the laser light led out from the lead-out portion.