CN113922197A

CN113922197A - Diaphragm and laser oscillator

Info

Publication number: CN113922197A
Application number: CN202110719138.7A
Authority: CN
Inventors: 河村让一; 田中研太
Original assignee: Sumitomo Heavy Industries Ltd
Current assignee: Sumitomo Heavy Industries Ltd
Priority date: 2020-07-10
Filing date: 2021-06-28
Publication date: 2022-01-11
Also published as: KR20220007512A; TWI781658B; JP2022015941A; TW202203529A

Abstract

The invention provides an aperture for an optical resonator capable of suppressing deviation of a beam cross section from a perfect circle. The aperture is disposed in a path of the laser beam enclosed within the optical cavity. The diaphragm defines a passage area through which the laser beam confined in the optical cavity passes and a light shielding area disposed around the passage area. The ratio of the dimensions in two directions orthogonal to each other in a plane orthogonal to the optical axis of the optical resonator, i.e., the aspect ratio, of the passing region is variable.

Description

Diaphragm and laser oscillator

The present application claims priority based on japanese patent application No. 2020-119131, filed on 10/7/2020. The entire contents of this japanese application are incorporated by reference into this specification.

Technical Field

The present invention relates to a diaphragm disposed in an optical resonator and a laser oscillator having the diaphragm mounted thereon.

Background

The laser oscillator includes an optical resonator including a front mirror and a rear mirror, and an excitation mechanism such as a discharge electrode. Typically, a front aperture and/or a rear aperture are arranged on the optical axis of the optical resonator. By disposing the diaphragm, the beam cross section can be shaped into a perfect circle, the beam divergence angle can be suppressed, and parasitic oscillation can be suppressed. In order to output a laser beam having a circular beam cross section, a metal plate provided with a circular opening is used as an aperture (for example, refer to patent document 1 below).

Patent document 1: japanese laid-open patent publication No. 61-276387

Even if the beam cross section is shaped by using a diaphragm having a circular aperture, the shape of the beam cross section of the laser beam output from the laser oscillator may deviate from a circular shape and become an elliptical shape.

Disclosure of Invention

The invention provides a diaphragm capable of suppressing deviation of a beam cross section from a perfect circle. Another object of the present invention is to provide a laser oscillator capable of suppressing deviation of a beam cross section from a perfect circle.

According to an embodiment of the invention, an aperture is provided, which is arranged in the path of the laser beam enclosed in the optical resonator, wherein,

the aperture defines a passage region through which the laser beam enclosed in the optical cavity passes and a light shielding region disposed around the passage region, and the aspect ratio, which is the ratio of the dimensions in two directions orthogonal to each other in a plane orthogonal to the optical axis of the optical cavity, of the passage region is variable.

According to another embodiment of the present invention, there is provided a laser oscillator including:

an optical resonant cavity enclosing the laser beam;

an aperture defining a passage region through which the laser beam confined in the optical cavity passes and a light shielding region disposed around the passage region, wherein an aspect ratio, which is a ratio of dimensions in two directions orthogonal to each other in a plane orthogonal to an optical axis of the optical cavity, of the passage region is variable;

the cavity is used for accommodating the optical resonant cavity, the diaphragm and the laser medium gas; and

an aspect ratio changing mechanism that operates from outside the chamber to change an aspect ratio of the passage area of the diaphragm.

By changing the aspect ratio of the passage area of the diaphragm, the shape of the beam cross section can be adjusted, and deviation from a perfect circle can be suppressed.

Drawings

Fig. 1 is a schematic diagram of a laser processing apparatus equipped with a laser oscillator according to the present embodiment.

Fig. 2 is a cross-sectional view including an optical axis of a laser oscillator according to an embodiment.

Fig. 3 is a cross-sectional view perpendicular to an optical axis of a laser oscillator according to an embodiment.

Fig. 4 is a view showing a positional relationship when the discharge electrode, the electrode case, and the diaphragm are viewed from the front side.

Fig. 5 (a) is a perspective view of the diaphragm, and fig. 5 (B) and (C) are front views of the 1 st and 2 nd members of the diaphragm.

Fig. 6 is a graph showing the results of an evaluation experiment for measuring the beam diameter of a beam spot (beam spot) of a laser beam at a position advanced from a light transmission window of a laser oscillator by a certain optical path length while changing the repetition frequency of pulses.

Fig. 7 is a cross-sectional view perpendicular to an optical axis of a laser oscillator according to another embodiment.

Fig. 8 is a perspective view of an aperture used in a laser oscillator according to still another embodiment.

In the figure: 11-stage, 12-laser oscillator, 15-chamber, 16-optical chamber, 17-blower chamber, 18-upper and lower partitions, 18A, 18B-opening, 19-bottom plate, 20-optical resonator, 20A-optical axis, 20B-region where light between a pair of resonator mirrors is blocked, 21-discharge electrode, 22-electrode box, 23-electrode support member, 24-discharge region, 25-resonator mirror, 26-resonator base, 27-optical resonator support member, 28-light transmission window, 29-blower, 40-partition, 41-1 st gas flow path, 42-2 nd gas flow path, 43-heat exchanger, 44-commutator, 45-support portion, 50-beam analyzer, 60-diaphragm, 60A-passing area, 60B-light-shielding area, 61-1 st part, 62-2 nd part, 62A, 62B-part of 2 nd part, 63-opening of 1 st part, 64-opening of 2 nd part, 65-sliding mechanism, 66A, 66B-rod, 67A, 67B-sealing structure, 70-diaphragm, 80-processing device, 81-beam shaping optical system, 82-worktable, 90-processing object, 100-shared base.

Detailed Description

Next, a laser oscillator according to an embodiment will be described with reference to fig. 1 to 6.

Fig. 1 is a schematic diagram of a laser processing apparatus equipped with a laser oscillator according to the present embodiment. The laser processing apparatus includes a laser oscillator 12 and a processing apparatus 80.

The laser oscillator 12 is supported by the mount 11, and the mount 11 is fixed to the common base 100. The processing device 80 includes a beam shaping optical system 81 and a stage 82. The object 90 is held on the table 82. The beam shaping optical system 81 and the stage 82 are fixed to a common base 100. A beam analyzer 50 may be disposed on the path of the laser beam between the laser oscillator 12 and the beam shaping optical system 81. In the laser processing, the beam analyzer 50 is retracted from the path of the laser beam. The common base 100 is, for example, a floor.

The laser oscillator 12 outputs a pulsed laser beam. As the laser oscillator 12, for example, a carbon dioxide laser oscillator is used. As the laser oscillator 12, other gas laser oscillators may be used, for example, an excimer laser oscillator may be used. The beam distribution of the pulse laser beam output from the laser oscillator 12 is shaped by the beam shaping optical system 81 and then enters the object 90.

Fig. 2 is a cross-sectional view including an optical axis of the laser oscillator 12 according to the embodiment. The laser oscillator 12 includes a chamber 15 that accommodates a laser medium gas, an optical resonator 20, and the like. The internal space of the chamber 15 is divided into an optical chamber 16 located on the upper side and a blower chamber 17 located on the lower side. The optical chamber 16 and the blower chamber 17 are partitioned by an upper partition 18 and a lower partition 18. The upper and lower partition plates 18 are provided with openings 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 protrudes from the side wall of the blower chamber 17 in the optical axis 20A direction of the optical resonator 20, and the length of the optical chamber 16 in the optical axis direction is longer than the length of the blower chamber 17 in the optical axis direction.

The floor 19 of the chamber 15 is supported on the gantry 11 (fig. 1) by means of four support points 45. The four support portions 45 are arranged at positions corresponding to four vertices of a rectangle in a plan view.

A pair of discharge electrodes 21 and a pair of resonator mirrors 25 are disposed in the optical chamber 16. The pair of discharge electrodes 21 are fixed to the electrode case 22, respectively. The pair of electrode cases 22 are supported on the base plate 19 via a plurality of electrode support members 23. The pair of discharge electrodes 21 are arranged with a gap therebetween in the vertical direction, and a discharge region 24 is defined therebetween. The discharge electrode 21 generates a discharge in the discharge region 24, thereby exciting the laser medium gas. A pair of resonator mirrors 25 constitute an optical resonator 20 having an optical axis 20A passing 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 a direction perpendicular to the paper surface of fig. 2.

The pair of resonator mirrors 25 are fixed to a common resonator base 26 disposed in the optical chamber 16. The resonator base 26 is a plate-like member elongated in the optical axis 20A direction, and is supported on the base plate 19 via a plurality of optical resonator support members 27.

The light generated in the discharge region 24 is repeatedly reflected between the pair of resonator mirrors 25, and a standing wave of a wavelength corresponding to the optical path length between the resonator mirrors 25 is generated in the region 20B between the pair of resonator mirrors 25. Thus, the laser beam is confined to the region 20B between the pair of resonator mirrors 25. A part of the laser beam enclosed in the optical resonator 20 is output to the outside through one resonator mirror 25 (the resonator mirror 25 on the left side in fig. 2). Two diaphragms 60, 70 are arranged on the path of the laser beam enclosed in the optical resonator 20. The diaphragms 60, 70 are supported by the cavity base 26. The two diaphragms 60, 70 are disposed at positions sandwiching the discharge region 24 in the optical axis 20A direction.

A light transmission window 28 through which a laser beam passes is provided at a position where an extension line extending in one direction (left direction in fig. 1) of the optical axis 20A of the optical resonator 20 intersects with a wall surface of the optical chamber 16. The laser beam excited in the optical resonator 20 is radiated toward the outside through the light transmitting window 28. The diaphragm 60 disposed on the side of the light-transmitting window 28 may be referred to as a front diaphragm, and the other diaphragm 70 may be referred to as a rear diaphragm.

A blower 29 is disposed 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 of the laser oscillator 12 according to the embodiment, which is perpendicular to the optical axis 20A (fig. 2). 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 pair of discharge electrodes 21 and a resonator base 26 are disposed in the optical chamber 16. The pair of discharge electrodes 21 are fixed to the electrode case 22, respectively. The electrode box 22 is supported by the bottom plate 19 of the chamber 15 via a plurality of electrode supporting members 23 (fig. 2). A discharge region 24 is defined between the pair of discharge electrodes 21. The resonator base 26 is supported to the floor 19 of the chamber 15 by a plurality of optical resonator support members 27 (fig. 2). Since the electrode support member 23 and the optical cavity support member 27 are arranged at positions shifted from the cross section shown in fig. 3, the electrode support member 23 and the optical cavity support member 27 are shown by broken lines in fig. 3.

A partition 40 is disposed in the optical chamber 16. The separators 40 define a 1 st gas flow path 41 from the opening 18A provided in the upper and lower separators 18 to the discharge region 24 and a 2 nd gas flow path 42 from the discharge region 24 to the other opening 18B provided in the upper and lower separators 18. The laser medium gas flows through 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 1 st gas channel 41, the discharge region 24, and the 2 nd gas channel 42 form a circulation channel through which the laser medium gas circulates. The blower 29 generates a laser medium gas flow indicated by an arrow to circulate the laser medium gas in the circulation flow path.

A heat exchanger 43 is accommodated in the circulation flow path in the blower chamber 17. The laser medium gas heated in the discharge region 24 is cooled by the heat exchanger 43, and the cooled laser medium gas is supplied to the discharge region 24 again.

Fig. 4 is a diagram showing a positional relationship when the discharge electrode 21, the electrode box 22, and the diaphragm 60 are viewed from the front side. In fig. 4, the electrode casing 22 is hatched. A pair of discharge electrodes 21 facing each other in the vertical direction are fixed to the electrode case 22, respectively. The 1 st gas flow path 41 and the 2 nd gas flow path 42 of the laser medium gas are defined by the separator 40 attached to the electrode case 22. The separator 40 is schematically shown in fig. 3, and the shape of the separator 40 shown in fig. 4 is different from the shape of the separator 40 schematically shown in fig. 3.

The laser medium gas flows from the 1 st gas channel 41 to the 2 nd gas channel 42 through the space between the pair of electrode boxes 22. In fig. 4, the arrows indicate the laser medium gas flow. The space between the pair of electrode boxes 22 contains a discharge region 24. A rectifying plate 44 is disposed at an inflow end of the laser medium gas flowing into the space between the pair of electrode boxes 22.

The diaphragm 60 is disposed at a position overlapping the discharge region 24. When viewed from the front side, the diaphragm 60 includes a passage area 60A through which the laser beam passes and a light shielding area 60B arranged around the passage area. The passage region 60A is included in the discharge region 24 when viewed from the front side. The ratio of the sizes of the passing regions 60A in two directions orthogonal to each other in a plane orthogonal to the optical axis 20A (fig. 2) of the optical resonator 20 is variable. The area through which the other diaphragm 70 (fig. 2) passes is a perfect circle, and the size thereof is not changed.

For example, the direction in which the laser medium gas flows (lateral direction in fig. 4) is defined as the 1 st direction D1, and the direction in which the pair of discharge electrodes 21 are spaced apart (longitudinal direction in fig. 4) is defined as the 2 nd direction D2. The dimension in the 1 st direction D1 through region 60A is variable, while the dimension in the 2 nd direction D2 is fixed. When the dimension in the 1 st direction D1 of the passing region 60A changes, the ratio of the dimension in the 1 st direction D1 of the passing region 60A to the dimension in the 2 nd direction D2 (hereinafter, referred to as the aspect ratio) changes. In fig. 4, the broken line indicates a passage area 60A in which the size in the 1 st direction D1 is reduced relative to the passage area 60A indicated by the solid line.

Next, the structure of the diaphragm 60 will be described with reference to fig. 5.

Fig. 5 (a) is a perspective view of the diaphragm 60. The diaphragm 60 includes a 1 st member 61 and a 2 nd member 62. The 2 nd part 62 comprises two

parts

62A, 62B. The 1 st member 61 is a plate material (e.g., a metal plate) disposed perpendicularly to the optical axis 20A of the optical resonator 20 (fig. 2), and an opening 63 overlapping with the path of the laser beam is provided in the plate material. The size of the opening 63 is constant.

The two

parts

62A, 62B of the 2 nd member 62 are arranged at positions sandwiching the optical axis 20A in the 1 st direction D1 when viewed from the front side. The two

members

62A and 62B are plate members disposed perpendicularly to the optical axis 20A. The edges of the two

parts

62A, 62B that are opposed to each other are recessed toward the inside so as to be curved.

The two

parts

62A, 62B of the 2 nd member 62 are supported by the slide mechanism 65 so as to be movable in the 1 st direction D1. The guide surface of the slide mechanism 65 is fixed to the resonator base 26 (fig. 2). The two

parts

62A, 62B are capable of moving individually in the 1 st direction D1. When the two

parts

62A, 62B are moved in the 1 st direction D1, the relative positional relationship between the opening 63 of the 1 st member 61 and the two

parts

62A, 62B changes when viewed from the front side. When the two

parts

62A and 62B are moved from the state where the two

parts

62A and 62B do not overlap the opening 63 to the direction approaching the optical axis 20A, the two

parts

62A and 62B overlap a part of the opening 63, and the part of the opening 63 is received from both sides in the 1 st direction D1. For example, the two

parts

62A, 62B block the area from the edge of the opening 63 to the inside. The area of the blocked area of the opening 63 changes based on the movement of the two

parts

62A, 62B of the 2 nd member 62.

Fig. 5 (B) and (C) are front views of the 1 st and 2

nd members

61 and 62. Fig. 5 (B) shows a state in which the two

parts

62A and 62B of the 2 nd member 62 do not overlap the opening 63 of the 1 st member 61. At this time, the opening 63 of the 1 st part 61 coincides with the passing area 60A of the diaphragm 60.

Fig. 5 (C) shows a state where two

parts

62A and 62B of the 2 nd member 62 overlap with a part of the opening 63 of the 1 st member 61. The region of the opening 63 that does not overlap with the 2 nd part 62 coincides with the passing region 60A of the diaphragm 60. By blocking a part of the opening 63 with the two

parts

62A, 62B of the 2 nd member 62, the dimension in the 1 st direction D1 passing through the area 60A becomes smaller. The dimension in the 2 nd direction D2 through the region 60A is the same as the dimension in the 2 nd direction D2 of the opening 63, which is unchanged.

Next, the excellent effects of the above-described embodiments will be described.

When a plurality of holes are formed by causing a pulsed laser beam output from a laser oscillator to enter a workpiece, the pulsed laser beam is caused to sequentially enter a plurality of positions where the holes are to be formed. If the distance from the hole to be processed to the next hole is longer, the distance of movement of the incident position of the pulse laser beam is longer, and the time from the previous irradiation to the next irradiation may be longer. Therefore, the repetition frequency of the pulse varies depending on the distribution of the holes to be formed. In order to make the shapes of the formed holes uniform, it is preferable that the repetition frequency of the pulse is variable and the shape of the beam spot is not variable.

The present inventors have conducted an evaluation experiment in which the shape of the beam spot of the laser beam is observed at a position advanced by a certain optical path length from the light transmission window 28 (fig. 2) of the laser oscillator 12 while changing the repetition frequency of the pulses of the laser oscillator 12. In the evaluation experiment, the passage area 60A of the diaphragm 60 is a perfect circle.

Fig. 6 is a graph showing the results of the evaluation experiment. The horizontal axis represents the repetition frequency of the pulses in the unit "kHz" and the vertical axis represents the size of the beam spot in the 1 st direction D1 and the 2 nd direction D2 as relative values. The circle and triangle marks in the graph indicate the dimension in the 1 st direction D1 and the dimension in the 2 nd direction D2, respectively. Regardless of the repetition frequency of the pulses, the size of the beam cross-section in the 1 st direction D1 is larger than the size in the 2 nd direction D2. In this way, even if the diaphragms 60 and 70 having perfect circles of the passage areas are used, the beam cross section does not become perfect circles, but becomes laterally long. This is because the oscillation condition is different in the 1 st direction D1 and the 2 nd direction D2 due to the influence of the laser medium gas flow and the nonuniformity of the discharge space.

When the repetition frequency of the pulse is decreased, the size of the beam cross section becomes large. However, the increase in the size in the 1 st direction D1 is larger than the increase in the size in the 2 nd direction D2. This is because the nonuniformity of the discharge state in the direction of the laser medium gas flow (1 st direction D1) is more greatly affected by the variation of the repetition frequency of the pulse than the nonuniformity of the discharge state in the 2 nd direction D2. When the repetition frequency of the pulse is decreased, the degree of deviation of the beam cross-section from a perfect circle becomes large.

In the present embodiment, by changing the size of the 1 st direction D1 of the passage area 60A of the diaphragm 60, the shape of the beam cross section can be made close to a perfect circle. For example, when the repetition frequency of the pulses is decreased so that the beam cross section becomes long in the 1 st direction D1, the size in the 1 st direction D1 passing through the region 60A may be decreased.

By adjusting the aspect ratio of the passing region 60A in accordance with the repetition frequency of the pulse, the beam cross section can be maintained in a substantially perfect circle state even if the repetition frequency of the pulse is changed.

Further, in the present embodiment, since a part of the opening 63 (fig. 5 (a)) of the 1 st part 61 is blocked from both sides in the 1 st direction D1, even if the size in the 1 st direction D1 passing through the area 60A is changed, the geometrically central position of the passing area 60A does not move. Therefore, even if the dimension in the 1 st direction D1 passing through the region 60A is changed, the central axis of the laser beam does not deviate.

Next, a modified example of the above embodiment will be explained.

In the above embodiment, the aspect ratio of the passage area 60A (fig. 4) of the front diaphragm 60 (fig. 2) is made variable, but the aspect ratio of the passage area of the rear diaphragm 70 may be made variable. Further, the aspect ratio of the passage area of both the diaphragms 60 and 70 may be variable.

In the above embodiment, the size of the diaphragm 60 in the 2 nd direction D2 passing through the region 60A is fixed, and the size in the 1 st direction D1 is variable, but the size in the 1 st direction D1 may be fixed and the size in the 2 nd direction D2 may be variable. In this case, it is preferable that the opening 63 (fig. 5 a) provided in the 1 st member 61 is formed in an elliptical shape elongated in the 2 nd direction D2, and the 2 nd member 62 is formed by two members divided in the 2 nd direction. The size in the 2 nd direction D2 of the passing region 60A may be increased as the repetition frequency of the pulse decreases. This can reduce the degree of deviation of the beam cross section from a perfect circle.

Further, both the size in the 1 st direction D1 and the size in the 2 nd direction D2 passing through the region 60A may be variable. This can improve the degree of freedom in adjusting the cross-sectional shape of the light beam.

In the above-described embodiment, the optical resonator 20 having the single linear optical axis 20A (fig. 2) is configured by the pair of resonator mirrors 25, but a folding optical resonator may be configured by additionally disposing other various mirrors. In this case, the optical resonator has, for example, a polygonal optical axis, and the laser beam is confined along the polygonal optical axis between the pair of resonator mirrors at both ends. The diaphragm may be disposed at an arbitrary position on the path of the polygonal line-shaped laser beam enclosed in the optical resonator.

Next, a laser oscillator according to another embodiment will be described with reference to fig. 7. Hereinafter, the same structure of the laser oscillator according to the embodiment shown in fig. 1 to 6 will not be described.

Fig. 7 is a cross-sectional view of the laser oscillator according to the present embodiment, which is perpendicular to the optical axis 20A. The 1 st part 61 of the diaphragm 60 is fixed to the cavity base 26. The two

parts

62A, 62B of the 2 nd member 62 are supported on the resonator base 26 via a slide mechanism 65. The two

parts

62A, 62B of the 2 nd member 62 are connected to

rods

66A, 66B, respectively. The

rods

66A, 66B extend from the two

parts

62A, 62B respectively in the 1 st direction D1, and extend through the side wall of the chamber 15 and out of the chamber 15. The portions of the

rods

66A and 66B penetrating the side wall of the chamber 15 are sealed with sealing

structures

67A and 67B including O-rings.

If the

levers

66A, 66B are operated from outside the chamber 15 to move in the 1 st direction D1, the two

parts

62A, 62B of the 2 nd member 62 will move in the 1 st direction D1. Thereby, the aspect ratio of the passing region 60A is changed. The

rods

66A, 66B function as an aspect ratio changing mechanism that changes the aspect ratio of the passage region 60A.

Next, the excellent effects of the present embodiment will be described.

In the present embodiment, the two

parts

62A, 62B of the 2 nd member 62 can be moved in the 1 st direction D1 from outside the chamber 15 via the

rods

66A, 66B. Therefore, the aspect ratio of the passage area 60A of the diaphragm 60 can be adjusted while observing the shape of the beam cross section by the beam analyzer 50 (fig. 1) in a state where the laser oscillator 12 is oscillated. This makes it possible to easily adjust the beam cross section to approximate a perfect circle.

Next, a laser oscillator according to still another embodiment will be described with reference to fig. 8. Hereinafter, the same structure of the laser oscillator according to the embodiment shown in fig. 1 to 6 will not be described.

Fig. 8 is a perspective view of an aperture 60 used in the laser oscillator according to the present embodiment. In the embodiment shown in fig. 1 to 6, the 2 nd member 62 (fig. 5 (a)) is divided into two in the 1 st direction D1. In contrast, in the present embodiment, neither the 1 st member 61 nor the 2 nd member 62 is divided. Like the 1 st member 61, the 2 nd member 62 is also formed of a plate material provided with openings 64. The 1 st member 61 and the 2 nd member 62 are supported by the slide mechanism 65 so as to be individually movable in the 1 st direction D1.

When the diaphragm 60 is viewed from the front side, an area where the opening 63 of the 1 st member 61 and the opening 64 of the 2 nd member 62 overlap each other coincides with the passing area 60A of the diaphragm 60. If the relative positional relationship in the 1 st direction D1 between the 1 st part 61 and the 2 nd part 62 is changed, the dimension in the 1 st direction D1 passing through the region 60A is changed. In addition, the dimension in the 2 nd direction D2 passing through the region 60A also changes, but the amount of change is small, and thus the aspect ratio passing through the region 60A changes. When the 1 st member 61 and the 2 nd member 62 are moved by the same distance in opposite directions, the dimension in the 1 st direction of the passage area 60A is changed while the center position of the passage area 60A is fixed.

Next, the excellent effects of the present embodiment will be described.

In the present embodiment, similarly to the embodiments shown in fig. 1 to 6, the beam cross section can be maintained in a substantially perfect circle state even if the repetition frequency of the pulse is changed by changing the aspect ratio of the passage area 60A of the diaphragm 60.

The above embodiments are merely examples, and it is needless to say that the structures shown in the different embodiments may be partially replaced or combined. The same operational effects based on the same structure in the plurality of embodiments are not individually described in each embodiment. Moreover, the present invention is not limited to only the above-described embodiments. For example, it will be apparent to those skilled in the art that various changes, modifications, combinations, and the like can be made.

Claims

1. An aperture disposed in a path of a laser beam enclosed within an optical resonator, the aperture characterized by,

2. The diaphragm according to claim 1,

a size in a 1 st direction of two directions orthogonal to each other in a plane orthogonal to an optical axis of the optical resonance cavity of the pass region is variable, and a size in a 2 nd direction orthogonal to the 1 st direction of the pass region is fixed.

3. The diaphragm according to claim 2, comprising:

the 1 st part is provided with an opening with a constant size; and

a 2 nd member supported to be movable in the 1 st direction with respect to the 1 st member, the 2 nd member being movable in the 1 st direction to block a partial region that enters from an edge of the opening of the 1 st member,

an area of the opening of the 1 st member, which is not blocked by the 2 nd member, becomes the passage area.

4. Aperture as claimed in claim 3,

the 2 nd member includes two parts divided from each other in the 1 st direction, and the two parts of the 2 nd member block a part of the opening of the 1 st member from both sides in the 1 st direction.

5. A laser oscillator is characterized by comprising:

an optical resonant cavity enclosing the laser beam;

6. The laser oscillator of claim 5,

7. The laser oscillator of claim 6,

the diaphragm includes:

the 1 st part is provided with an opening with a constant size; and

the aspect ratio changing mechanism moves the 2 nd member in the 1 st direction with respect to the 1 st member.

8. The laser oscillator of claim 7,

the 2 nd member includes two parts divided from each other in the 1 st direction, the two parts of the 2 nd member block the opening of the 1 st member from both sides in the 1 st direction,

the aspect ratio changing mechanism moves the two parts of the 2 nd member in the 1 st direction, respectively.