JP2022013224A - Laser oscillator - Google Patents

Abstract

To provide a laser oscillator capable of suppressing increase in size and cost of a device and of suppressing deviation of an optical axis of an optical resonator.SOLUTION: A chamber houses a laser medium gas. A discharge electrode generates electric discharge in the chamber. An optical resonator that has an optical axis passing through a region where the electric discharge is generated by the discharge electrode is held by a resonator base arranged in the chamber. A temperature difference reduction structure reduces a temperature difference between a first surface facing the discharge electrode and a second surface facing an opposite side to the discharge electrode, in a surface of the resonator base.SELECTED DRAWING: Figure 2

Description

The present invention relates to a laser oscillator.

The optical cavity used in a laser oscillator has a pair of resonator mirrors that confine light between the resonator mirrors to produce stimulated emission. If the optical axis of the pair of resonator mirrors shifts, the output of the laser beam will decrease. In order to avoid a decrease in the output of the laser beam, it is important to suppress the deviation of the optical axis of the pair of resonator mirrors. In order to suppress the optical axis shift, a structure in which a pair of resonator mirrors are fixed to the resonator base may be adopted.

Patent Document 1 below discloses a laser oscillator in which a container containing a laser medium and an optical resonator is arranged in another outer container, and a vacuum is created between the outer container and the inner container. There is. With this configuration, the influence of heat from the outside is reduced.

Japanese Unexamined Patent Publication No. 58-176985

In a configuration in which a pair of resonator mirrors are supported by one resonator base, it is preferable to use a member having high rigidity in which the resonator base is not easily deformed in order to suppress the optical axis deviation. However, if a thick and large member is used as the resonator base in order to increase the rigidity, the size of the device becomes large and the cost increases.

An object of the present invention is to provide a laser oscillator capable of suppressing an increase in size and cost of an apparatus and suppressing an optical axis deviation of an optical resonator.

According to one aspect of the invention
A discharge electrode that generates a discharge in the chamber that houses the laser medium gas,
A resonator base that is located in the chamber and holds an optical resonator having an optical axis that passes through a region where discharge occurs at the discharge electrode.
A laser oscillator having a temperature difference reducing structure for reducing a temperature difference between a first surface facing the discharge electrode and a second surface facing the opposite side of the discharge electrode among the surfaces of the resonator base. Provided.

The temperature difference reduction structure reduces the temperature between the first surface and the second surface of the resonator base. This makes it possible to suppress warpage deformation due to a temperature difference without using a thick and highly rigid member as the resonator base. Since the deformation of the resonator base is less likely to occur, the optical axis deviation of the optical resonator is also less likely to occur. Since it is not necessary to use a thick and highly rigid member as the resonator base, it is possible to suppress an increase in size and cost of the device.

FIG. 1 is a schematic view of a laser device equipped with a laser oscillator according to an embodiment and a processing device that performs processing with a laser beam output from the laser oscillator. FIG. 2 is a cross-sectional view including an optical axis of the laser oscillator according to the embodiment. FIG. 3 is a cross-sectional view perpendicular to the optical axis of the laser oscillator according to the embodiment. 4A is a plan view of the resonator base used in the laser oscillator according to the embodiment, and FIGS. 4B and 4C are cross-sectional views taken along the alternate long and short dash line 4B-4B and 4C-4C, respectively. .. FIG. 5 is a cross-sectional view including an optical axis of a laser oscillator according to another embodiment. FIG. 6 is a cross-sectional view perpendicular to the optical axis of the laser oscillator according to still another embodiment.

FIG. 1 is a schematic view of a laser device 10 equipped with a laser oscillator 12 according to an embodiment, and a processing device 80 that performs processing with a laser beam output from the laser device 10. The laser device 10 and the processing device 80 are fixed to the common base 100. The common base 100 is, for example, a floor.

The laser device 10 includes a gantry 11 fixed to the common base 100 and a laser oscillator 12 supported by the gantry 11. The processing apparatus 80 includes a beam shaping optical system 81 and a stage 82. The object to be machined 90 is held on the stage 82. The beam shaping optical system 81 and the stage 82 are fixed to the common base 100. The laser beam output from the laser oscillator 12 has its beam profile shaped by the beam shaping optical system 81, and is incident on the object to be machined 90.

FIG. 2 is a cross-sectional view including the optical axis of the laser oscillator 12. The laser oscillator 12 includes a chamber 15 that houses a laser medium gas, an optical resonator 20, and the like. The laser medium gas is housed in the chamber 15. The internal space of the chamber 15 is divided into an optical chamber 16 located relatively above and a blower chamber 17 located relatively below. The optical chamber 16 and the blower chamber 17 are partitioned by an upper and lower partition plate 18. The upper and lower partition plates 18 are provided with an opening for allowing the laser medium gas to flow between the optical chamber 16 and the blower chamber 17. The bottom plate 19 of the optical chamber 16 projects from the side wall of the blower chamber 17 in the direction of the optical axis 20A of the optical resonator 20, and the length of the optical chamber 16 in the optical axis direction is the length of the blower chamber 17 in the optical axis direction. It's longer than that.

The bottom plate 19 of the chamber 15 is supported by the gantry 11 (FIG. 1) at four support points 35. The four support points 35 are arranged at positions corresponding to the four vertices of the rectangle in a plan view.

A discharge electrode 21 and an optical resonator 20 are arranged in the optical chamber 16. The optical resonator 20 includes a pair of resonator mirrors 25. The discharge electrode 21 includes a pair of conductive members 21A, and each of the pair of conductive members 21A is fixed to the electrode box 22. The pair of electrode boxes 22 are supported by the bottom plate 19 via the electrode support member 23. The pair of conductive members 21A constituting the discharge electrode 21 are arranged at intervals in the vertical direction, and a discharge region 24 is defined between the two. The discharge electrode 21 excites the laser medium gas by causing a discharge in the discharge region 24. The optical axis 20A of the optical resonator 20 passes through the discharge region 24. As will be described later with reference to FIG. 3, the laser medium gas flows through the discharge region 24 in the direction perpendicular to the paper surface of FIG.

The optical cavity 20 including the pair of resonator mirrors 25 is fixed to one resonator base 26 arranged in the optical chamber 16. The resonator base 26 is a single plate-shaped member long in the direction of the optical axis 20A, and is supported by the bottom plate 19 via four optical resonator support members 27. A heat shielding member 30 is held on the upper surface of the resonator base 26 so as to be expandable and contractible in the direction of the optical axis 20A. The heat shield member 30 is held by the resonator base 26 by bolts 31 so as not to fall off from the resonator base 26. In the present specification, among the upper and lower surfaces of the resonator base 26, the surface facing the discharge electrode 21 side (upper surface in FIG. 2) is referred to as the first surface 26A, and the surface facing the opposite side (lower surface in FIG. 2) is referred to as the first surface. 2 Surface 26B.

A light transmission window 28 for transmitting a laser beam is attached to an intersection of an extension line extending the optical axis 20A of the optical resonator 20 in one direction (left direction in FIG. 1) and the wall surface of the optical chamber 16. .. The laser beam excited in the optical resonator passes through the light transmission window 28 and is radiated to the outside.

A blower 29 is arranged in the blower chamber 17. The blower 29 circulates the laser medium gas between the optical chamber 16 and the blower chamber 17.

FIG. 3 is a cross-sectional view perpendicular to the optical axis 20A (FIG. 2) of the laser oscillator 12 according to the embodiment. As described with reference to FIG. 2, the internal space of the chamber 15 is divided into an upper optical chamber 16 and a lower blower chamber 17 by the upper and lower partition plates 18. A discharge electrode 21, a resonator base 26, and a heat shielding member 30 are arranged in the optical chamber 16. A pair of conductive members 21A constituting the discharge electrode 21 are fixed to the electrode box 22, respectively. The electrode box 22 is supported by the electrode support member 23 on the bottom plate 19 (FIG. 2) of the chamber 15. A discharge region 24 is defined between the pair of conductive members 21A. The resonator base 26 is supported by the optical resonator support member 27 on the bottom plate 19 (FIG. 2) of the chamber 15. Since the electrode support member 23 and the optical resonator support member 27 are arranged at positions deviated from the cross section shown in FIG. 3, the electrode support member 23 and the optical resonator support member 27 are represented by broken lines in FIG. ..

A partition plate 40 is arranged in the optical chamber 16. The partition plate 40 is a first gas flow path 41 from the opening 18A provided in the upper and lower partition plates 18 to the discharge region 24, and a second gas flow from the discharge region 24 to another opening 18B provided in the upper and lower partition plates 18. The road 42 is defined. The laser medium gas flows in the discharge region 24 in a direction orthogonal to the optical axis 20A (FIG. 2). The discharge direction is orthogonal to both the direction in which the laser medium gas flows and the optical axis 20A. The blower chamber 17, the first gas flow path 41, the discharge region 24, and the second gas flow path 42 form a circulation path through which the laser medium gas circulates. The blower 29 generates a flow of the laser medium gas indicated by an arrow so that the laser medium gas circulates in this circulation path.

The heat exchanger 43 is housed in the circulation path in the blower chamber 17. The laser medium gas heated in the discharge region 24 is cooled by passing through the heat exchanger 43, and the cooled laser medium gas is resupplied to the discharge region 24.

Next, the support structure of the resonator base 26 and the heat shielding member 30 will be described with reference to FIGS. 4A to 4C.

4A is a plan view of the resonator base 26 and the heat shield member 30, and FIGS. 4B and 4C are cross-sectional views taken along the alternate long and short dash line 4B-4B and the alternate long and short dash line 4C-4C of FIG. 4A, respectively. A heat shielding member 30 is placed on the resonator base 26 and is supported so as to be expandable and contractible in the direction of the optical axis 20A. The resonator base 26 is a flat plate long in the direction of the optical axis 20A. The resonator mirror 25 is fixed on the first surface 26A near both ends of the resonator base 26.

Four optical resonator support members 27A, 27B, 27C, and 27D are arranged at positions included in the resonator base 26 in a plan view. Each of the optical resonator support members 27A and 27B is a stepped pin, and is arranged on the same side of the optical axis 20A in a plan view. The straight line passing through the center of the optical resonator support members 27A and 27B in a plan view is parallel to the optical axis 20A. The other two optical resonator support members 27C and 27D are pins having no step, and are arranged at positions of line symmetry of the optical resonator support members 27A and 27B with respect to the optical axis 20A in a plan view, respectively. .. That is, the four optical resonator support members 27A to 27D are arranged at positions corresponding to the four vertices of the rectangle. The lower ends of the four optical resonator support members 27A to 27D are embedded in the bottom plate 19 and fixed to the bottom plate 19.

The resonator base 26 is provided with a circular hole 51 and an elongated hole 52. The circular hole 51 and the elongated hole 52 are arranged at positions corresponding to the optical resonator support members 27A and 27B in a plan view, respectively. The elongated hole 52 has a long shape in a direction parallel to the optical axis 20A in a plan view. A portion of the optical resonator support members 27A and 27B above the step is inserted into the circular hole 51 and the elongated hole 52. The resonator base 26 is supported in a direction in which a load is applied by the stepped portions of the optical resonator support members 27A and 27B and the upper end surfaces of the optical resonator support members 27C and 27D.

The portion of the resonator base 26 around the circular hole 51 is constrained in position in the horizontal plane with respect to the optical resonator support member 27A. The optical resonator support member 27B inserted into the elongated hole 52 is movable in a one-dimensional direction parallel to the optical axis 20A with respect to the resonator base 26. The optical resonator support members 27C and 27D can move in two directions in a horizontal plane with respect to the resonator base 26. That is, the resonator base 26 is constrained in the horizontal position at one place with respect to the chamber 15, and is not constrained in the horizontal position at the other three places.

The heat shield member 30 is supported by the resonator base 26 by four bolts 31 penetrating the heat shield member 30 so as not to fall off from the resonator base 26. The hole of the heat shield member 30 through which two bolts 31 of the four bolts 31 pass is an elongated hole 32, and the heat shield member 30 can expand and contract in the direction of the optical axis 20A with respect to the resonator base 26. Is.

Next, the excellent effect of the above embodiment will be described.
In the configuration in which the heat shielding member 30 is not arranged, the heat generated in the discharge electrode 21 and the electrode box 22 is transmitted to the resonator base 26, and the temperature of the first surface 26A of the resonator base 26 is higher than the temperature of the second surface 26B. It gets higher. When a temperature difference occurs in the thickness direction of the resonator base 26, the amount of thermal expansion differs between the first surface 26A and the second surface 26B of the resonator base 26, and the resonator base 26 is warped and deformed. When the resonator base 26 is warped and deformed, the parallelism of the pair of resonator mirrors 25 is lowered. That is, the optical axes of the pair of resonator mirrors 25 are displaced. If the optical axes of the pair of resonator mirrors 25 are displaced, the laser output will decrease. In order to reduce the warp deformation of the resonator base 26, the resonator base 26 must be thickened to increase its rigidity. Alternatively, an expensive low thermal expansion member must be used for the resonator base 26.

On the other hand, in the above embodiment, the heat shielding member 30 suppresses the transfer of heat from the discharge electrode 21 and the electrode box 22 to the first surface 26A of the resonator base 26 via the laser medium gas. For the heat shielding member 30, a material having a small thermal conductivity such as PTFE is used. Even if the upper surface of the heat shield member 30 is heated and the temperature rises, the temperature rise of the lower surface is suppressed. As a result, the temperature rise of the first surface 26A of the resonator base 26 facing the lower surface of the heat shielding member 30 is also suppressed. Therefore, a temperature difference is less likely to occur between the first surface 26A and the second surface 26B of the resonator base 26, and warpage deformation due to the temperature difference is also less likely to occur. Therefore, the resonator base 26 can be made thinner, and the size of the apparatus can be suppressed. Further, since it is not necessary to use a low thermal expansion member having high characteristics for the resonator base 26, it is possible to reduce the cost of the device. In order to obtain a sufficient effect that a temperature difference is less likely to occur between the first surface 26A and the second surface 26B of the resonator base 26, the heat shield member 30 has a heat smaller than the thermal conductivity of the resonator base 26. It is preferable to use a material having conductivity.

Further, since the heat shield member 30 can expand and contract in the direction of the optical axis 20A (FIG. 2) with respect to the resonator base 26, even if the heat shield member 30 itself thermally expands, the resonator base 26 is deformed. do not have.

Next, a modified example of the above embodiment will be described.
In the above embodiment, a material having a small thermal conductivity such as PTFE is used for the heat shielding member 30 (FIGS. 2 and 3), but other heat insulating materials may be used. Further, a heat shield member that shields the radiant heat from the discharge electrode 21 and the electrode box 22 to the resonator base 26 may be used. In the above embodiment, the heat shield member 30 is mounted on the first surface 26A of the resonator base 26, but the heat shield member 30 is supported in the space between the discharge electrode 21 and the resonator base 26. May be good.

In the above embodiment, the optical resonator 20 is composed of a pair of resonator mirrors 25, but one or more mirrors may be added to form a folded optical resonator. In this case, the pair of resonator mirrors 25 constituting the optical resonator and other mirrors included in the optical resonator may be supported on the resonator base 26. Also in this configuration, by arranging the heat shielding member 30, it is possible to suppress the deviation of the optical axis of the optical component including the pair of resonator mirrors 25 and other mirrors.

Next, a laser oscillator according to another embodiment will be described with reference to FIG. Hereinafter, the description of the common configuration with the laser oscillator according to the embodiment shown in FIGS. 1 to 4C will be omitted.

FIG. 5 is a cross-sectional view including an optical axis 20A of the laser oscillator according to the present embodiment. In this embodiment, the cooling flow path 60 is provided inside the resonator base 26 instead of the heat shielding member 30 (FIGS. 2 and 3). The partition wall joints 62 and 63 are attached to the wall surface of the chamber 15. Pipe lines 64 and 65 are introduced into the chamber 15 from the cooling water supply / recovery device 61 via the partition wall joints 62 and 63, respectively. The pipelines 64 and 65 are connected to the cooling flow path 60 in the resonator base 26 via the joints 66 and 67, respectively. The cooling water supply / recovery device 61 supplies cooling water to the cooling flow path 60 through one of the pipelines 64, and recovers the cooling water from the cooling flow path 60 through the other pipeline 65.

The cooling flow path 60 is provided at a position closer to the first surface 26A than the second surface 26B. That is, it is arranged closer to the discharge electrode 21 than the center in the thickness direction.

Next, the excellent effects of the examples shown in FIG. 5 will be described.
In this embodiment, the resonator base 26 is cooled by the cooling water flowing through the cooling flow path 60. Since the cooling flow path 60 is arranged on the first surface 26A side, the first surface 26A is preferentially cooled over the second surface 26B. Since the first surface 26A, which tends to be relatively hot, is preferentially cooled, the temperature difference between the upper and lower surfaces of the resonator base 26 can be reduced. Therefore, as in the examples shown in FIGS. 1 to 4C, the resonator base 26 has an excellent effect that warpage deformation due to a temperature difference is less likely to occur.

Next, a modified example of this embodiment will be described.
In this embodiment, the cooling flow path 60 is provided inside the resonator base 26, but it may be provided on the first surface 26A. In this embodiment, the cooling water is flowed through the cooling flow path 60, but other cooling fluids may be flowed. For example, gas may be used as the fluid flowing through the cooling flow path 60.

Next, still another embodiment will be described with reference to FIG. Hereinafter, the description of the common configuration with the laser oscillator according to the embodiment shown in FIGS. 1 to 4C will be omitted.

FIG. 6 is a cross-sectional view perpendicular to the optical axis 20A of the laser oscillator according to the present embodiment. In this embodiment, the gas circulation mechanism 70 is arranged in place of the heat shielding member 30 (FIGS. 2 and 3). The gas circulation mechanism 70 circulates the laser medium gas between the space in contact with the first surface 26A of the resonator base 26 and the space in contact with the second surface 26B. The gas circulation mechanism 70 includes, for example, a blower fan.

The gas circulation mechanism 70 causes the laser medium gas in the space in contact with the first surface 26A to flow in a direction intersecting the optical axis 20A (FIG. 2). The laser medium gas flowing along the first surface 26A is folded back in front of the partition plate 40 and flows into the space in contact with the second surface 26B. The laser medium gas flowing along the second surface 26B is folded back in front of the partition plate 40 on the opposite side and returns to the space in contact with the first surface 26A.

Next, the excellent effects of the examples shown in FIG. 6 will be described. In this embodiment, heat is transferred between the first surface 26A and the second surface 26B via the laser medium gas circulating between the space in contact with the first surface 26A and the space in contact with the second surface 26B. Is done. As a result, the temperature difference between the first surface 26A and the second surface 26B is reduced. Therefore, as in the examples shown in FIGS. 1 to 4C, the resonator base 26 has an excellent effect that warpage deformation due to a temperature difference is less likely to occur.

In any of the above three embodiments, the laser oscillator has a temperature difference reducing structure that reduces the temperature difference between the first surface 26A and the second surface 26B of the resonator base 26. In the embodiment shown in FIGS. 1 to 4C, the temperature difference reducing structure includes the heat shielding member 30 (FIGS. 2 and 3). In the embodiment shown in FIG. 5, the temperature difference reduction structure includes a cooling flow path 60 (FIG. 5) and the like. In the embodiment shown in FIG. 6, the temperature difference reduction structure includes the gas circulation mechanism 70 (FIG. 6). The temperature difference reducing structure may include a plurality of heat shielding members 30 (FIGS. 2 and 3), a cooling flow path 60 (FIG. 5), and a gas circulation mechanism 70 (FIG. 6). Further, another structure may be adopted as the temperature difference reducing structure.

It goes without saying that each of the above embodiments is exemplary and the configurations shown in different examples can be partially replaced or combined. Similar actions and effects due to the same configuration of a plurality of examples will not be mentioned sequentially for each example. Furthermore, the present invention is not limited to the above-mentioned examples. For example, it will be obvious to those skilled in the art that various changes, improvements, combinations, etc. are possible.

10 Laser device 11 Stand 12 Laser oscillator 15 Chamber 16 Optical chamber 17 Blower chamber 18 Upper and lower partition plates 18A, 18B Opening 19 Bottom plate 20 Optical cavity 20A Optical axis 21 Discharge electrode 21A Pair of conductive members 22 that make up the discharge electrode 22 Electrode box 23 Electrode support member 24 Discharge region 25 Optical cavity mirror 26 Resonator base 26A First surface 26B Second surface 27, 27A, 27B, 27C, 27D Optical cavity support member 28 Light transmission window 29 Blower 30 Heat shield member 31 Bolt 32 Long hole 35 Chamber support 40 Partition plate 41 1st gas flow path 42 2nd gas flow path 43 Heat exchanger 51 Circular hole 52 Long hole 60 Cooling flow path 61 Cooling water supply / recovery device 62, 63 Partition joint 64, 65 Pipeline 66, 67 Joint 70 Gas circulation mechanism 80 Processing device 81 Beam shaping optical system 82 Stage 90 Processing object 100 Common base

Claims (5)

A discharge electrode that generates a discharge in the chamber that houses the laser medium gas,
A resonator base that is located in the chamber and holds an optical resonator having an optical axis that passes through a region where discharge occurs at the discharge electrode.
A laser oscillator having a temperature difference reducing structure for reducing a temperature difference between a first surface of the surface of the resonator base facing the discharge electrode and a second surface facing the opposite side of the discharge electrode. The laser oscillator according to claim 1, wherein the temperature difference reducing structure is arranged between the resonator base and the discharge electrode, and includes a heat shielding member that insulates or shields heat. The laser oscillator according to claim 2, wherein the heat shielding member is supported on the resonator base so as to be expandable and contractible in the optical axis direction of the optical resonator. Claim 1 to the above-mentioned temperature difference reducing structure includes a cooling flow path provided on the first surface or inside the resonator base at a position closer to the first surface than the second surface. The laser oscillator according to any one of 3. The one according to any one of claims 1 to 4, wherein the temperature difference reducing structure includes a gas circulation mechanism for circulating a laser medium gas between a space in contact with the first surface and a space in contact with the second surface. Laser oscillator.

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