Laser oscillator

Abstract

This laser oscillator is provided with: an output mirror (1); a reflection mirror (2) that reflects laser light (A) output from the output mirror (1); and electrodes (3) that are disposed as a pair at an interval D in a y-axis direction, which is an axis perpendicular to a z-axis that is the optical axis of the laser light (A), and for which a length in the x-axis direction, which is the axis perpendicular to the z-axis and the y-axis, is W. An outer surface (11) of the output mirror (1) is an inclined surface that is inclined with respect to an xy plane perpendicular to the z-axis. An angle α, which is formed by the y-axis and an inclined straight line that is a straight line intersecting the optical axis in the outer surface (11) of the output mirror (1) and has a largest angle θ relative to the xy-plane, is larger than tan -1 (W / D) and smaller than π-tan-1 (W / D), or is larger than tan-1 (W / D) -π and smaller than -tan-1 (W / D), in terms of radian as a unit of angle.

Description

laser oscillator

[0001] The present disclosure relates to laser oscillators.

[0002] Conventionally, laser oscillators have been known that include an output mirror that outputs laser light, a reflecting mirror that reflects the laser light output from the output mirror, and a pair of electrodes spaced apart in a direction perpendicular to the optical axis of the laser light. When unwanted parasitic oscillation light is generated by light reflection on the outer surface of the output mirror, the transverse mode, which is the intensity distribution, deteriorates and the output of the laser light decreases. For example, the optical resonator disclosed in Patent Document 1 tilts the outer surface of the front mirror, which serves as the output mirror, and uses a roof mirror with two intersecting reflective surfaces as the reflecting mirror. The tilted outer surface of the front mirror is arranged parallel to the valley line of the roof mirror, thereby suppressing parasitic oscillation light.

[0003] Japanese Patent Application Laid-Open No. 2020-98814

[0004] However, in the technology disclosed in Patent Document 1, the inclination direction of the outer surface of the front mirror and the valley line of the roof mirror are perpendicular to the electrodes arranged in pairs, so light reflected from the outer surface of the front mirror heads toward the electrodes, and there is a risk that reflection by the electrodes will result in parasitic oscillation light.

[0005] The present disclosure has been made in view of the above, and has an object to provide a laser oscillator that can suppress parasitic oscillation light that occurs due to reflection from the electrodes.

[0006] In order to solve the above-mentioned problems and achieve the object, the laser oscillator according to the present disclosure comprises an output mirror from which laser light is output, a reflecting mirror that reflects the laser light output from the output mirror, and electrodes arranged in pairs at a distance D in the y-axis direction, which is an axis perpendicular to the z-axis, which is the optical axis of the laser light, and each electrode has a length W in the x-axis direction, which is an axis perpendicular to the z-axis and y-axis. An optical resonator is formed by the inner surface of the output mirror and the inner surface of the reflecting mirror facing the inner surface of the output mirror. The outer surface of the output mirror is an inclined surface that is inclined with respect to the xy plane, which is perpendicular to the z-axis. If the angle between the y-axis and a straight line within the outer surface of the output mirror that intersects with the optical axis and makes the largest angle with the xy plane is defined as angle α, then angle α can be expressed as tan －１ (W / D) is larger than π-tan －１ (W / D) or tan －１ (W / D)-π or greater, -tan －１ (W / D).

[0007] The laser oscillator according to the present disclosure has the advantage of being able to suppress parasitic oscillation light caused by reflection from the electrodes.

[0008] 8 is a plan view showing light reflected by the outer surface of the output mirror in the optical resonator of the laser oscillator according to the first embodiment; －１ (W / D) is an explanatory diagram showing the state in which the electrodes of the laser oscillator according to the first embodiment are viewed from the z-axis direction, and the angle α of the inclined straight line is π-tan －１1 is a perspective view of an optical resonator in a modified example 1 of the laser oscillator according to the first embodiment; 2 is a perspective view of an optical resonator in a modified example 2 of the laser oscillator according to the first embodiment; 3 is a perspective view of an optical resonator in a laser oscillator according to the third embodiment; and 4 is a graph showing the power of light reflected by the output mirror, the electrode, and the retroreflection mirror when the angle α is changed in the laser oscillator according to the third embodiment.

[0009] Hereinafter, a laser oscillator according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0010] First Embodiment. FIG. 1 is a perspective view showing the overall configuration of a laser oscillator according to a first embodiment. As shown in FIG. 1, a laser oscillator 200 is disposed inside a vacuum vessel 300. The laser oscillator 200 includes an output mirror 1, a reflecting mirror 2, a pair of electrodes 3, a heat exchanger 4, and a blower 5. In the following description, the output mirror 1, the reflecting mirror 2, and the electrodes 3 are collectively referred to as an optical resonator 100. The laser oscillator 200 shown in FIG. 1 illustrates a case in which a discharge occurs in the direction of the y-axis (y-axis direction), which is perpendicular to the z-axis, which is the optical axis of the laser light A output from the output mirror 1, and a gas flow F in the discharge space S occurs in the direction of the x-axis (x-axis direction), which is perpendicular to the z-axis and y-axis. The laser oscillator 200 shown in FIG. 1 is called a three-axis orthogonal laser in which the optical axis of the laser light A, the direction of the discharge, and the direction of the gas flow F are mutually orthogonal.

[0011] FIG. 2 is a perspective view showing an optical resonator of the laser oscillator according to the first embodiment. As shown in FIG. 2 , in the optical resonator 100, an output mirror 1 and a reflecting mirror 2 are arranged facing each other with a gap therebetween, and an inner surface 10 of the output mirror 1 and an inner surface 20 of the reflecting mirror 2 that face each other form an optical resonator. In the optical resonator 100, laser light A is output from the output mirror 1. The output mirror 1 has an inner surface 10 that faces the inside of the optical resonator and an outer surface 11 that faces the outside. The inner surface 10 of the output mirror 1 is coated with, for example, a coating that provides a desired reflectance for the wavelength of the laser light A. The outer surface 11 of the output mirror 1 is coated with, for example, a coating that provides high transmittance for the wavelength of the laser light A.

[0012] The reflecting mirror 2 has an inner surface 20 that faces the inside of the optical resonator and an outer surface 21 that faces the outside. The inner surface 20 of the reflecting mirror 2 is coated with, for example, a coating that provides high reflectivity for the wavelength of the laser light A.

[0013] The paired electrodes 3 are arranged with a distance D in the y-axis direction. Each electrode 3 has a length W in the x-axis direction and a length L in the z-axis direction. Between the paired electrodes 3 is a discharge space S where the laser gas is excited by the discharge. The volume of the discharge space S can be expressed as W x D x L using W, D, and L. A laser gas that functions as a laser medium is supplied between the paired electrodes 3. The laser gas can be, for example, CO ２ , N ２ , He, CO, Xe, O ２ , H ２ The laser gas is a mixed gas containing some or all of the above. For example, CO having a wavelength of 10.6 μm or 9.3 μm is used. ２ A laser or a CO laser having a wavelength in the 5 μm to 6 μm band oscillates.

[0014] In the optical resonator 100, laser light A travels back and forth between the inner surface 10 of the output mirror 1 and the inner surface 20 of the reflecting mirror 2, and is amplified by the laser gas excited in the discharge space S. A portion of the amplified laser light A is output from the outer surface 11 of the output mirror 1 and extracted.

[0015] The heat exchanger 4 cools the laser gas excited in the discharge space S. The blower 5 is disposed to circulate the laser gas within the discharge space S, and generates a gas flow F that is a flow of the laser gas. The laser gas cooled by the heat exchanger 4 is blown by the blower 5 and circulated and supplied back to the discharge space S.

[0016] FIG. 3 is a plan view showing an optical resonator of a comparative example. FIG. 4 is a front view showing an optical resonator of a comparative example. FIGS. 3 and 4 show an example in which laser light A oscillates along the z-axis, which is the optical axis, in the optical resonator 100A. As shown in FIG. 4, the outer surface 11 of the output mirror 1 in the comparative example is inclined with respect to the x-y plane, which is perpendicular to the z-axis, which is the optical axis. The direction in which the outer surface 11 of the output mirror 1 is inclined is defined as the direction of the line included in the outer surface 11 that has the largest inclination angle with respect to the x-y plane. This maximum inclination angle is defined as θ. Here, the line included in the outer surface 11 of the output mirror 1 that has the largest inclination angle with respect to the x-y plane and intersects with the z-axis, which is the optical axis, is referred to as an inclined line. In FIG. 4, the inclined line exists in the y-z cross section. In this case, the inclined line is referred to as "inclined in the y-axis direction." The inclination direction of the outer surface 11 and the inclination direction of the inclined line are the same.

[0017] 5 is a front view showing a state in which parasitic oscillation light is generated between the outer surface of the output mirror, the inner surface of the reflecting mirror, and the electrode in the optical resonator of the comparative example. As shown in FIG. 5, in the optical resonator 100A of the comparative example, the inclined straight line included in the outer surface 11 of the output mirror 1 is inclined in the y-axis direction. Therefore, light reflected by the outer surface 11 of the output mirror 1 travels toward the electrode 3, is reflected by the electrode 3, and becomes unwanted parasitic oscillation light B between the outer surface 11 of the output mirror 1, the inner surface 20 of the reflecting mirror 2, and the electrode 3. In other words, the parasitic oscillation light B is not aligned with the z-axis, which is the optical axis of the optical resonator 100A. Thus, in the optical resonator 100A of the comparative example, the unwanted oscillation, parasitic oscillation light B, causes a deterioration in the transverse mode, which is the intensity distribution, and reduces the output of the laser light A.

[0018] FIG. 6 is a plan view showing the optical resonator of the laser oscillator according to the first embodiment. FIG. 7 is a front view showing the optical resonator of the laser oscillator according to the first embodiment. FIGS. 6 and 7 show an example in which laser light A oscillates along the z-axis, which is the optical axis, in the optical resonator 100. As shown in FIG. 6 , in the optical resonator 100 of the laser oscillator 200 according to the first embodiment, the outer surface 11 of the output mirror 1 is inclined in the x-axis direction, unlike the outer surface 11 of the output mirror 1 inclined in the y-axis direction shown in FIG. 4 as a comparative example. In other words, among the straight lines present in the outer surface 11 of the output mirror 1, an inclined straight line exists in the x-z cross section, which is a straight line having the largest inclination angle with respect to the xy plane and which intersects with the z-axis, which is the optical axis.

[0019] 8 is a plan view showing the reflected light reflected by the outer surface of the output mirror in the optical resonator of the laser oscillator according to the first embodiment. As shown in FIG. 8, in the optical resonator 100 of the laser oscillator 200 according to the first embodiment, the inclined line included in the outer surface 11 of the output mirror 1 is inclined in the x-axis direction. Therefore, the reflected light C reflected by the outer surface 11 of the output mirror 1 does not head toward the electrode 3, but passes through between the electrodes 3 arranged in pairs to exit the optical resonator 100. That is, in the laser oscillator 200 according to the first embodiment, the reflected light C reflected by the outer surface 11 of the output mirror 1 is not reflected by the electrode 3.

[0020] The inclination angle θ at which the reflected light C, which is reflected by the outer surface 11 of the output mirror 1 without being reflected by the electrode 3, exits the optical resonator 100 while traveling back and forth within the optical resonator 100 may be set to satisfy the following formula (1): However, the requirement for satisfying the inclination angle θ is not limited to formula (1).

[0021]

[0022] In this way, in the laser oscillator 200 according to the first embodiment, the parasitic oscillation light B due to reflection at the electrode 3 as shown in FIG. 5 is not generated, so that the transverse mode, which is the intensity distribution, can be improved and a decrease in the output of the laser light A can be suppressed.

[0023] FIG. 9 is an explanatory diagram showing the output mirror as viewed from the y-axis direction. FIG. 10 is an explanatory diagram showing an enlarged view of a portion of the outer surface of the output mirror as viewed from the white arrow X shown in FIG. 10 . In FIG. 10 , an inclined straight line 12 is indicated by an arrow. As shown in FIG. 9 , the outer surface 11 of the output mirror 1 is inclined at an inclination angle θ with respect to the xy plane 13. The example shown in FIG. 10 shows a state in which the inclined straight line 12, which is the line on the outer surface 11 of the output mirror 1 that has the largest inclination angle with respect to the xy plane 13 and intersects with the z-axis, which is the optical axis, is rotated by an angle α from the y-axis. The angle α shown in FIG. 10 is π / 2 radians.

[0024] 9, when the output mirror 1 is viewed on a plane where the inclined line 12 and the z-axis exist, that is, in the xz cross section, the direction of the arrow of the inclined line 12 shown in Fig. 10 indicates the direction away from the intersection P of the inner surface 10 and the outer surface 11 of the output mirror 1 when the surfaces are extended. Therefore, the optical resonator 100 can suppress the parasitic oscillation light B shown in Fig. 5 by rotating the inclined line 12, which indicates the inclination direction of the outer surface 11 of the output mirror 1, by π / 2 radians with respect to the y-axis, which is the direction in which the electrodes 3 face each other.

[0025] Although the inclined line 12 shown in Figure 10 is rotated counterclockwise by π / 2 radians from the y-axis, it may also be rotated clockwise by π / 2 radians from the y-axis. In this case, the angle α is -π / 2 radians. In the optical resonator 100A of the comparative example shown in Figures 3 to 5, the angle α between the inclined line in the outer surface 11 and the y-axis is 0 radians, so that the light reflected by the outer surface 11 of the output mirror 1 travels toward the electrode 3 and is reflected by the electrode 3 to become unwanted parasitic oscillation light B.

[0026] FIG. 11 shows the state of the electrodes of the laser oscillator according to the first embodiment as viewed from the z-axis direction, with the angle α of the inclined straight line being tangent to the －１ 12 is an explanatory diagram showing the state in which the electrode of the laser oscillator according to the first embodiment is viewed from the z-axis direction, and the angle α of the inclined straight line is π-tan －１ 11 and 12 are arranged in pairs and face each other at a distance D in the y-axis direction. The length of each electrode 3 in the x-axis direction is W.

[0027] 11 and 12, in order to suppress the parasitic oscillation light B shown in Fig. 5, the inclined line 12 indicating the inclination direction of the outer surface 11 of the output mirror 1 is made not to intersect with the electrode 3 so that the reflected light C reflected by the outer surface 11 of the output mirror 1 is not reflected onto the electrode 3. In other words, the angle α formed by the inclined line 12 and the y-axis should be set to satisfy the following formula (2).

[0028]

[0029] 11 and 12 show the inclined straight line 12 rotated counterclockwise by the angle α, but it may also be rotated clockwise by the angle α. In this case, the angle α between the inclined straight line 12 and the y-axis is given by the following formula (3).

[0030]

[0031] For example, when W = 9 mm and D = 12.9 mm, the range of formula (2) is 0.61 radians (35 degrees) < α < 2.53 radians (145 degrees), and the range of formula (3) is -2.53 radians (-145 degrees) < α < -0.61 radians (-35 degrees).

[0032] Furthermore, for example, when W = 38 mm and D = 12.9 mm, the range of formula (2) is 1.24 radians (71 degrees) < α < 1.90 radians (109 degrees), and the range of formula (3) is -1.90 radians (-109 degrees) < α < -1.24 radians (-71 degrees).

[0033] Furthermore, for example, when W = 50 mm and D = 12.9 mm, the range of formula (2) is 1.32 radians (76 degrees) < α < 1.82 radians (105 degrees), and the range of formula (3) is -1.82 radians (-105 degrees) < α < -1.32 radians (-76 degrees).

[0034] Furthermore, if the angle α of the inclined straight line 12 is π / 2 radians (90 degrees), which is the median value of the range of equations (2) and (3), or −π / 2 radians (−90 degrees), the parasitic oscillation light B can be further suppressed.

[0035] As described above, the laser oscillator 200 according to the first embodiment includes an output mirror 1 from which laser light A is output, a reflecting mirror 2 that reflects the laser light A output from the output mirror 1, and electrodes 3 that are arranged in pairs at a distance D in the y-axis direction that is perpendicular to the z-axis that is the optical axis of the laser light A, and have a length W in the x-axis direction that is perpendicular to the z-axis and y-axis. An optical resonator is formed by an inner surface 10 of the output mirror 1 and an inner surface 20 of the reflecting mirror 2 that faces the inner surface 10 of the output mirror 1. An outer surface 11 of the output mirror 1 is an inclined surface that is inclined with respect to an xy-plane 13 that is perpendicular to the z-axis. If the angle between the y-axis and an inclined straight line 12 that intersects with the optical axis within the outer surface 11 of the output mirror 1 and that forms the maximum angle θ with the xy-plane 13 is defined as angle α, the angle α can be expressed in radians as tan －１ (W / D) is larger than π-tan －１ (W / D) or tan －１ (W / D)-π or greater, -tan －１ (W / D).

[0036] That is, in the laser oscillator 200 according to the first embodiment, the angle α formed by the inclined line 12 and the y-axis is set so that the inclined line 12, which indicates the inclination direction of the outer surface 11 of the output mirror 1, does not intersect with the electrode 3. As a result, the reflected light C reflected by the outer surface 11 of the output mirror 1 is not reflected by the electrode 3 but passes outside the optical resonator 100, thereby suppressing the parasitic oscillation light B generated due to the reflection by the electrode 3. This makes it possible to improve the transverse mode, which is the intensity distribution, and to suppress a decrease in the output of the laser light A.

[0037] 13 is a perspective view showing an optical resonator in a first modification of the laser oscillator according to the first embodiment. As shown in Fig. 13, in the optical resonator 100 according to the first embodiment, a folding mirror 6 that defines the polarization of the laser light A may be provided on the optical path of the laser light A between the inner surface 10 of the output mirror 1 and the inner surface 20 of the reflecting mirror 2. For example, a polarization-dependent coating may be applied to the reflecting surface 60 of the folding mirror 6 so that the laser light A has a desired polarization.

[0038] 14 is an explanatory diagram showing an output mirror of a second modification of the laser oscillator according to the first embodiment. The inner surface 10 of the output mirror 1A of the modification shown in FIG. １ The radius of curvature R is the center of curvature １ For example, the output mirror 1A has an inner surface 10 with a radius of curvature R １ is a radius of curvature R that satisfies the stability condition shown in the following formula (4). １ By doing so, a stable optical resonator can be constructed, and the output of the laser light A can be stabilized. ２ is the radius of curvature of the inner surface 20 of the reflecting mirror 2, and L ｃ is the resonator length. The resonator length is the distance between the inner surface 10 of the output mirror 1A and the inner surface 20 of the reflecting mirror 2. In addition, in Fig. 14, the outer surface 11 of the output mirror 1A is illustrated as being flat, but it is not limited to being flat, and may be a curved surface or a surface having another shape.

[0039]

[0040] Second Embodiment Next, a laser oscillator according to a second embodiment will be described. Fig. 15 is an explanatory diagram showing an output mirror of the laser oscillator according to the second embodiment. As shown in Fig. 15, the output mirror 1B of the laser oscillator according to the second embodiment has an outer surface 11 made of O ２ The radius of curvature r with the center of curvature １ The other configurations are the same as those of the first embodiment. The radius of curvature r is set so that an optical resonator is not formed between the outer surface 11 of the output mirror 1B and the inner surface 20 of the reflecting mirror 2. １ For example, when the radius of curvature r １ is the formula (4) above, R １ r １ and the stability condition expressed by the formula (4) is not satisfied, it is possible to suppress the parasitic oscillation light B. Note that a stable resonator can also be constructed by satisfying the formula (4) above for the inner surface 10 of the output mirror 1B. In this case, in the formula (4) above, since the inner surface 10 of the output mirror 1B is a flat surface, the radius of curvature R １can be considered to be infinite, and (1-L ｃ / R １ ) becomes 1.

[0041] Furthermore, in the output mirror 1B shown in Figure 15, the tilt direction of the outer surface 11 is defined as follows. Of the straight lines included in the tangent plane 14 that is tangent to the intersection of the outer surface 11 and the z-axis, the direction of the straight line that has the largest tilt angle with respect to the xy-plane 13 is defined as the tilt direction, and this maximum tilt angle is defined as θ. Of the straight lines included in the tangent plane 14 that is tangent to the intersection of the outer surface 11 and the z-axis, the straight line that has the largest tilt angle with respect to the xy-plane 13 and intersects with the z-axis, which is the optical axis, is called the tilt straight line. The tilt straight line in the output mirror 1B shown in Figure 15 exists in the xz cross section and is tilted toward the x-axis direction.

[0042] As with the optical resonator 100 in the first embodiment, the angle α between the y-axis and an inclined line, which is a line that has the maximum inclination angle with respect to the xy-plane 13 and intersects with the z-axis, on the outer surface 11 of the output mirror 1B should satisfy the above formulas (2) and (3). Thus, in the laser oscillator according to the second embodiment, even when the angle α satisfies the above formulas (2) and (3), the inclined line indicating the inclination direction of the outer surface 11 of the output mirror 1B can be prevented from intersecting with the electrode 3, thereby making it possible to suppress the parasitic oscillation light B.

[0043] In the laser oscillator according to the second embodiment, in the above formula (4), R １ r １ 15 illustrates the inner surface 10 of the output mirror 1B as a flat surface, but it is not limited to a flat surface, and may be a curved surface or a surface having another shape.

[0044] 16 is an explanatory diagram showing an output mirror as a modification of the laser oscillator according to the second embodiment. In the output mirror 1C of the modification shown in FIG. 16, the inner surface 10 is O １ The radius of curvature R is the center of curvature １ The outer surface 11 is a spherical surface of O ２ The radius of curvature r with the center of curvature１ In the output mirror 1C shown in FIG. 16, the radius of curvature of the inner surface 10 is R １ The radius of curvature R satisfies the above formula (4). １ By doing so, the stability as an optical resonator can be improved, and the output of the laser light A can be stabilized.

[0045] Third Embodiment Next, a laser oscillator 200 according to the third embodiment will be described. FIG. 17 is a perspective view showing an optical resonator of the laser oscillator according to the third embodiment. The optical resonator 101 of the laser oscillator 200 shown in FIG. 17 uses a retroreflective mirror 7 as the reflecting mirror 2. The retroreflective mirror 7 is a mirror in which a first reflecting mirror surface 70 and a second reflecting mirror surface 71 intersect at a right angle. The retroreflective mirror 7 has a valley line 72, which is the intersection line between the first reflecting mirror surface 70 and the second reflecting mirror surface 71. The retroreflective mirror 7 is arranged, for example, so that the valley line 72 is parallel to the y-axis. In this case, the direction of the valley line 72 is perpendicular to the x-axis, which is the direction of the gas flow F in the discharge space S, and the z-axis, which is the optical axis of the laser light A. By using the retroreflective mirror 7, the optical resonator 101 can prevent the optical axis of the laser light A output from the output mirror 1 from being changed by the gas flow F, thereby achieving stable oscillation.

[0046] FIG. 18 is a graph showing the power of light reflected by the output mirror, electrodes, and retroreflection mirror when the angle α is changed in the laser oscillator according to the third embodiment. The vertical axis represents the power of light reflected between the outer surface 11 of the output mirror 1, the electrode 3, and the first and second reflecting mirror surfaces 70 and 71 of the retroreflection mirror 7. The horizontal axis represents the angle α. In FIG. 18, in order to illustrate the likelihood of occurrence of parasitic oscillation light B in the optical resonator 101, the power of the reflected light is calculated and normalized by a value of α = 0. Hereinafter, the power of the reflected light normalized by a value of α = 0 will be simply referred to as normalized power. The larger the normalized power, the more likely parasitic oscillation light B is to be generated.

[0047] The solid line shown in Fig. 18 is a calculation example when the length W of the electrode 3 in the x-axis direction is 9 mm. The dashed line shown in Fig. 18 is a calculation example when the length W of the electrode 3 in the x-axis direction is 38 mm. The dotted line shown in Fig. 18 is a calculation example when the length W of the electrode 3 in the x-axis direction is 50 mm. In all of the solid line, dashed line, and dotted line shown in Fig. 18, the spacing D of the electrodes 3 in the y-axis direction is 12.9 mm.

[0048] The normalized power shown in Fig. 18 decreases as |α|, the absolute value of the angle α, increases from 0 radians (0 degrees), and tends to decrease until it approaches 1.57 radians (90 degrees) for all of the solid, dashed, and dotted lines. Furthermore, the normalized power shown in Fig. 18 has a graph shape that is symmetrical with respect to |α| of 1.57 radians (90 degrees).

[0049] The normalized power shown in FIG. 18 is small near 1.57 radians (90 degrees), and there is a range where it does not change significantly even when the angle |α| changes. In this range, not only can the parasitic oscillation light B be suppressed, but the normalized power does not change significantly even when the angle |α| changes, increasing the margin for suppressing the parasitic oscillation light B. When W=9 mm, this range is 1.05 radians (60 degrees) < |α| < 2.09 radians (120 degrees). When W=38 mm, it is 1.40 radians (80 degrees) < |α| < 1.75 radians (100 degrees). When W=50 mm, it is 1.40 radians (80 degrees) < |α| < 1.75 radians (100 degrees).

[0050] The smaller the length W of the electrode 3 in the x-axis direction, the wider the range of |α| becomes, and the range of |α| remains unchanged even when the value of W is greater than 38 mm. Rewriting the range of |α| where parasitic oscillation light B can be suppressed and where the suppression margin is large as the range of α, when W = 9 mm, the ranges are 1.05 radians (60 degrees) < α < 2.09 radians (120 degrees) and -2.09 radians (-120 degrees) < α < -1.05 radians (-60 degrees). When W = 38 mm, the ranges are 1.40 radians (80 degrees) < α < 1.75 radians (100 degrees) and -1.75 radians (-100 degrees) < α < -1.40 radians (-80 degrees). When W = 50 mm, 1.40 radians (80 degrees) < α < 1.75 radians (100 degrees), and -1.75 radians (-100 degrees) < α < -1.40 radians (-80 degrees).

[0051] The range of |α| becomes wider as the length W of the electrode 3 in the x-axis direction becomes smaller. Furthermore, the range of |α| does not change when the length W of the electrode 3 in the x-axis direction is 38 mm or greater. Therefore, for example, a common range of α that is independent of the length W of the electrode 3 in the x-axis direction may be 1.40 radians (80 degrees) < α < 1.75 radians (100 degrees) or -1.75 radians (-100 degrees) < α < -1.40 radians (-80 degrees).

[0052] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0053] 1, 1A, 1B, 1C Output mirror, 2 Reflection mirror, 3 Electrode, 4 Heat exchanger, 5 Fan, 6 Folding mirror, 7 Retroreflection mirror, 10, 20 Inner surface, 11, 21 Outer surface, 12 Inclined straight line, 13 xy plane, 14 Tangent plane, 60 Reflection surface, 70 First reflection mirror surface, 71 Second reflection mirror surface, 72 Valley line, 100, 100A, 101 Optical resonator, 200 Laser oscillator, A Laser light, B Parasitic oscillation light, C Reflected light, S Discharge space.

Claims

1. An optical resonator is provided, comprising: an output mirror that outputs laser light; a reflecting mirror that reflects the laser light output from said output mirror; and electrodes that are arranged in pairs at an interval D in the direction of the y-axis that is perpendicular to the z-axis that is the optical axis of the laser light, and each electrode has a length of W in the direction of the x-axis that is perpendicular to the z-axis and the y-axis, wherein the inner surface of said output mirror and the inner surface of said reflecting mirror that faces the inner surface of said output mirror form an optical resonator, the outer surface of said output mirror is an inclined surface that is inclined with respect to the xy plane that is perpendicular to the z-axis, and when the angle formed by the inclined line that intersects with the optical axis on the outer surface of said output mirror and that forms the largest angle with the xy plane and the y-axis is defined as angle α, said angle α is expressed in radians as tan －１ (W / D) is larger than π-tan －１ (W / D) or tan －１ (W / D)-π or greater, -tan －１ (W / D) is smaller than 1 / 2.

2. A laser oscillator comprising: an output mirror that outputs laser light; a reflecting mirror that reflects the laser light output from said output mirror; and electrodes arranged in pairs with a gap in the direction of the y-axis that is perpendicular to the z-axis that is the optical axis of the laser light, wherein an optical resonator is formed by the inner surface of said reflecting mirror and the inner surface of said output mirror that faces the inner surface of said reflecting mirror, and wherein the outer surface of said output mirror is spherical with a radius of curvature, and a tangent plane that is a plane tangent to the intersection of the outer surface of said output mirror and said optical axis is formed so as to be inclined with respect to the xy plane that is perpendicular to the z-axis.

3. The electrodes are arranged in pairs with a distance D in the y-axis direction, and the length in the x-axis direction, which is perpendicular to the z-axis and y-axis, is W. If the angle between the y-axis and the inclined line that intersects with the optical axis in the tangential plane and forms the largest angle with the xy plane is defined as angle α, then the angle α is expressed as tan －１ (W / D) is larger than π-tan －１ (W / D) or tan －１ (W / D)-π or greater, -tan －１ 3. The laser oscillator according to claim 2, wherein the wattage is smaller than (W / D).

4. A laser oscillator according to any one of claims 1 to 3, characterized in that the reflecting mirror has two reflecting surfaces that are orthogonal to each other.

5. The laser oscillator according to claim 4, wherein a valley line, which is an intersection line between the two reflecting surfaces, is parallel to the y-axis.

6. A laser oscillator according to claim 5 dependent on claim 1, wherein the angle α is greater than 1.40 radians and less than 1.75 radians, or greater than -1.75 radians and less than -1.40 radians.

7. A laser oscillator according to claim 1, claim 3, or claim 4 or 5 depending on claim 1 or 3, wherein the angle α is π / 2 radians or -π / 2 radians.

Images