Optical amplifier and laser processing apparatus including the same

Abstract

A light amplifier and a laser processing apparatus including the same are disclosed. The disclosed light amplifier includes: a gain material having a first surface on which a signal beam is incident and a second surface disposed opposite to the first surface, wherein the incident signal beam is amplified during its movement toward the second surface and exits through the second surface; and a pump source connected to the gain material to provide a pump beam to one of the first surface and the second surface, wherein the gain material may include a scattering prevention surface connecting the first surface and the second surface and reflecting the pump beam during its movement toward the first surface or the second surface, and the signal beam may be configured to pass through a concentrated region where the pump beam reflected by the scattering prevention surface is focused.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2020-0105539, filed on August 21, 2020, which is incorporated herein by reference for all purposes as fully set forth herein. Technical Field

[0003] This invention relates to an optical amplifier and a laser processing apparatus including the same. Background Technology

[0004] Generally, a laser processing device refers to a device that uses a focusing lens to focus a laser beam into a focal point and then directs that focus onto the surface or interior of the object being processed.

[0005] Such a laser processing apparatus may include an oscillator that generates a signal beam and an optical amplifier that amplifies the signal beam generated by the oscillator.

[0006] An optical amplifier may include a gain material capable of amplifying a signal beam, and a pump source that provides a pump beam to the gain material to induce density inversion within the gain material.

[0007] The amplification efficiency of an optical amplifier can be varied depending on the amount of pump beam incident on the inside of the gain material that unexpectedly slips out or is scattered. Summary of the Invention

[0008] The present invention provides an optical amplifier and a laser processing apparatus that improves amplification efficiency by minimizing the amount of pump beam that unintentionally leaks out or scatters from the interior of the gain material.

[0009] The present invention provides an optical amplifier and a laser processing apparatus, which can reduce the temperature difference inside the gain material by improving the thermal conductivity of the gain material.

[0010] The present invention provides an optical amplifier and a laser processing apparatus that improves the amplification efficiency of a signal beam inside a gain material by reusing a pump beam with a large divergence angle.

[0011] The light amplifier according to one aspect of the present invention includes:

[0012] A gain medium having a first surface on which a signal beam is incident and a second surface disposed opposite the first surface, wherein the incident signal beam is amplified during its movement to the second surface and exits through the second surface; and

[0013] A pump source, connected to the gain material, provides a pump beam to at least one of the first and second surfaces.

[0014] The gain material includes a scattering prevention surface that connects the first surface and the second surface and reflects the pump beam during its movement toward either the first or second surface.

[0015] The signal beam can be configured to pass through a concentrated region of the pump beam that is concentrated by the scattering-prevented surface reflection.

[0016] The surface flatness of the scattering prevention surface can be λ / 1 or smaller.

[0017] The gain material may include: a first concentration region in which the pump beam is concentrated; a first divergence region in which the pump beam diverges through the first concentration region; a second concentration region in which the pump beam, which passes through the first divergence region and is concentrated by the scattering-prevented surface reflection, is concentrated; and a second divergence region in which the pump beam diverges through the second concentration region.

[0018] The length of the gain material can be 10 times or more and 100 times or less than the width of the gain material.

[0019] The light amplifier may further include a metal layer disposed on the outline of the scattering prevention surface.

[0020] The metal layer may include a material having a reflectivity of 95% or higher for the pump beam.

[0021] The light amplifier may further include a heat-dissipating structure comprising trenches for accommodating the gain material.

[0022] The thermal conductivity of the heat-exothermic structure can be greater than that of the gain material.

[0023] The cross-sectional shape in the length direction perpendicular to the gain direction can be at least one of a circle, an ellipse, and a polygon.

[0024] A laser processing apparatus according to another aspect of the present invention includes:

[0025] A laser oscillator that generates a signal beam;

[0026] An optical amplifier that amplifies the signal beam generated by the laser oscillator.

[0027] The light amplifier includes:

[0028] A gain material having a first surface on which the signal beam is incident and a second surface disposed opposite the first surface, and amplifying and exiting the incident signal beam through the second surface as it moves toward the second surface; and

[0029] A pump source, connected to the gain material, provides a pump beam to at least one of the first and second surfaces.

[0030] The gain material includes a scattering prevention surface that connects the first surface and the second surface and reflects the pump beam during its movement toward either the first or second surface.

[0031] The signal beam can be configured as a concentrated region where the pump beam, after being scattered multiple times to prevent surface reflection, is focused.

[0032] The surface flatness of the scattering prevention surface can be λ / 1 or smaller.

[0033] The gain material may include: a first concentration region in which the pump beam is concentrated; a first divergence region in which the pump beam diverges through the first concentration region; a second concentration region in which the pump beam, which passes through the first divergence region and is concentrated by the scattering-prevented surface reflection, is concentrated; and a second divergence region in which the pump beam diverges through the second concentration region.

[0034] The length of the gain material can be 10 times or more and 100 times or less than the width of the gain material.

[0035] The light amplifier may further include a metal layer disposed on the outline of the scattering prevention surface.

[0036] The metal layer may be made of a material that has a reflectivity of 95% or higher for the pump beam.

[0037] The light amplifier may further include a heat-dissipating structure comprising trenches for accommodating the gain material.

[0038] The thermal conductivity of the heat-exothermic structure can be greater than that of the gain material.

[0039] The cross-sectional shape in the length direction perpendicular to the gain direction can be at least one of a circle, an ellipse, and a polygon. Attached Figure Description

[0040] Figure 1 This is a conceptual diagram of a laser processing apparatus according to an embodiment.

[0041] Figure 2 This is a conceptual diagram of an optical amplifier according to one embodiment.

[0042] Figure 3 The illustration shows a light amplifier according to one embodiment.

[0043] Figure 4A diagram illustrating the scattering prevention surface of the gain material according to an embodiment.

[0044] Figure 5 This is a diagram used to describe diffuse reflection in the gain material according to a comparative scale.

[0045] Figure 6 This is a diagram illustrating an optical amplifier according to another embodiment.

[0046] Figure 7 for Figure 6 A magnified view of a portion of the image.

[0047] Figure 8 This is for describing an optical amplifier according to another embodiment.

[0048] Figures 9A to 9E This is a diagram illustrating an example of the cross-sectional shape of a gain material according to an embodiment.

[0049] Figure 10 This is a diagram used to describe the movement of the signal beam.

[0050] Figure 11 and Figure 12 This is a conceptual diagram of an optical amplifier according to other embodiments. Detailed Implementation

[0051] In the following, embodiments of the invention are described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals refer to the same components, and for the sake of simplicity, the dimensions or thicknesses of the components may be exaggerated.

[0052] Terms including ordinal numbers such as "first," "second," etc., can be used to describe various components, but components are not limited to the limitations of these terms. These terms are used only to distinguish one component from another. For example, without departing from the scope of the invention, a first component can be named a second component, and similarly, a second component can be named a first component. The term "and / or" includes a combination of multiple related items or any one of multiple related items.

[0053] Figure 1 This is a conceptual diagram of a laser processing apparatus 1 according to an embodiment. Figure 2 This is a conceptual diagram of a light amplifier according to an embodiment.

[0054] Reference Figure 1 and Figure 2 The laser processing device 1 may include a laser oscillator 10 and an optical amplifier 20.

[0055] The laser oscillator 10 can generate a signal beam SB. The laser oscillator 10 transmits the signal beam SB to the optical amplifier 20. The signal beam SB can be a pulsed laser beam.

[0056] The optical amplifier 20 includes a gain material 100 and a pump source 200 that provides a pump beam PB to the gain material 100.

[0057] The gain material 100 has a first surface 101 on which the signal beam SB is incident, and a second surface 102 disposed on the opposite side of the first surface 101. The gain material 100 may, for example, include active ions obtained from rare earth elements such as ytterbium (Yb), neodymium (Nd), erbium (Er), and thulium (Tm). Furthermore, the gain material 100 may, for example, include active ions obtained from transition metal elements such as chromium (Cr) and titanium (Ti).

[0058] Pump source 200 can be connected to gain material 100 to provide a pump beam PB to at least one of the first surface 101 and the second surface 102 of gain material 100. For example, pump source 200 can be connected to gain material 100 to provide a pump beam PB to the first surface 101 of gain material 100. The pump beam PB provided by pump source 200 is incident on the first surface 101, and density inversion occurs within gain material 100 due to the incident pump beam PB. As signal beam SB passes through gain material 100 in which density inversion occurs, amplification of signal beam SB occurs.

[0059] An optical component 30 may be arranged between the pump source 200 and the gain material 100, which collects the pump beam PB and transmits it into the gain material 100. As an example, the optical component 30 may include at least one of a focusing lens 31 for collecting the pump beam PB and a reflector 32 for converting the direction of the pump beam PB. The pump beam PB passing through the gain material 100 may be absorbed by the dump 34 after being reflected by the reflector 33. Figure 3 The figure shows a light amplifier 20 according to one embodiment.

[0060] Reference Figure 3 The gain material 100 may have a rod-type shape extending from the first surface 101 to the second surface 102.

[0061] The gain material 100 may have a preset length L. For example, the length L of the gain material 100 may be 10 times or more and 100 times or less than the width D of the gain material 100. When the shape of the gain material 100 is cylindrical, the width D of the gain material 100 may be expressed as the diameter.

[0062] The width D of the gain material 100 can be 2 mm or less. The length L of the gain material 100 can be 100 mm or less.

[0063] Both the signal beam SB and the pump beam PB can be incident along the length of the gain material 100. For example, the signal beam SB and the pump beam PB can be incident on the same surface of the gain material 100, namely the first surface 101. However, the incident is not limited to this; various deformations can be made as long as the signal beam SB and the pump beam PB are incident along the length of the gain material 100. For example, the pump beam PB can be incident on the second surface 102, which serves as the exit surface of the signal beam SB (see reference). Figure 11 Alternatively, it can be incident on the first surface 101, which serves as the incident surface of the signal beam SB, and the second surface 102, which serves as the exit surface (see reference). Figure 12 ).

[0064] The gain material 100 includes a scattering prevention surface 110, which connects the first surface 101 and the second surface 102.

[0065] The scattering prevention surface 110 can be configured to reflect the pump beam PB that moves within the gain material 100 toward at least one of the first surface 101 and the second surface 102 and prevent the pump beam PB from being diffusely reflected within the gain material 100.

[0066] When the pump beam PB is incident on the first surface 101 of the gain material 100, the scattering prevention surface 110 can be configured to reflect the pump beam PB moving toward the second surface 102 inside the gain material 100 and prevent the pump beam PB from being diffusely reflected inside the gain material 100.

[0067] Figure 4 This is a diagram illustrating the scattering prevention surface 110 of the gain material 100 according to an embodiment. Figure 5 This is a diagram used to describe diffuse reflection in gain material 100 according to a comparative example.

[0068] The scattering prevention surface 110 can have an optically flat surface. For example, the surface flatness (or optical flatness) of the scattering prevention surface 110 can be λ / 1 or smaller. For example, the surface flatness of the scattering prevention surface 110 can be λ / 2 or smaller. For example, the surface flatness of the scattering prevention surface 110 can be λ / 4 or smaller. For example, the surface flatness of the scattering prevention surface 110 can be λ / 8 or smaller. For this purpose, the outer surface of the gain material can be polished by optical processing.

[0069] Reference Figure 4The scattering prevention surface 100 can concentrate the pump beams PB1, PB2, and PB3 within a predetermined area inside the gain material 100 by uniformly reflecting the pump beams PB1, PB2, and PB3, and can prevent the pump beams PB from being diffusely reflected and unexpectedly slipping out to the outside.

[0070] Conversely, refer to Figure 5 In the case where the gain material 1000 does not have a scattering prevention surface 110, in other words, in the case of having an uneven surface 1100, the pump beams PB1, PB2, and PB3 are diffusely reflected on the surface of the gain material 1000, and some of the pump beams PB1, PB2, and PB3 may slip out to the outside.

[0071] Refer to Figure 3 The pump beam PB can be incident to focus at a predetermined position on the gain material 100. As the pump beam PB is reflected by the scattering prevention surface 110, multiple concentrated regions 121, 122, and 123 appear inside the gain material 100.

[0072] The gain material 100 may include: a first concentration region 121 in which the pump beam PB is concentrated; a first divergence region in which the pump beam PB diverges through the first concentration region 121; a second concentration region 122 in which the pump beam PB, which passes through the first divergence region 131 and is reflected by the scattering prevention surface 110, is concentrated; and a second divergence region 132 in which the pump beam PB diverges through the second concentration region 122. The gain material 100 may further include a third concentration region 123 in which the pump beam PB, which passes through the second divergence region 132 and is reflected by the scattering prevention surface 100, is concentrated.

[0073] The pump beam PB can be relatively concentrated in the first concentration region 121, the second concentration region 122, and the third concentration region 123 in the gain material 100. Therefore, the signal beam SB is amplified by more during its passage through the first concentration region 121, the second concentration region 122, and the third concentration region 123 than it is amplified by more during its passage through the first divergence region 131 and the second divergence region 132.

[0074] The minimum diameter D1 of the pump beam PB in the first concentration region 121, the second concentration region 122, and the third concentration region 123 can be half or less than the maximum diameter of the pump beam PB in the first divergence region 131 and the second divergence region 132. For example, the minimum diameter D1 of the pump beam PB in the first concentration region 121, the second concentration region 122, and the third concentration region 123 can be one-fifth or less than the maximum diameter of the pump beam PB in the first divergence region 131 and the second divergence region 132. For example, the minimum diameter D1 of the pump beam PB in the first concentration region 121, the second concentration region 122, and the third concentration region 123 can be one-tenth or less than the maximum diameter of the pump beam PB in the first divergence region 131 and the second divergence region 132. The maximum diameter of the pump beam PB in the first divergence region 131 and the second divergence region 132 can be the same as the width D (or diameter) of the gain material 100.

[0075] In the light amplifier 20 according to the embodiment, since the scattering prevention surface 110 has multiple concentrated regions (i.e., the first concentrated region 121, the second concentrated region 122, and the third concentrated region 123) in the gain material 100, the signal beam SB can have improved amplification efficiency by passing through the multiple concentrated regions.

[0076] The minimum diameter D1 of the laser beam PB in the first concentrated region 121, the second concentrated region 122, and the third concentrated region 123 can be smaller than the minimum diameter of the signal beam SB passing through the gain material 100.

[0077] Figure 6 This is a diagram illustrating an optical amplifier 20A according to another embodiment. Figure 7 for Figure 6 A magnified view of a portion of the image.

[0078] Reference Figure 6 and Figure 7 The optical amplifier 20A according to the embodiment may further include a metal layer 150 disposed on the outer contour of the gain material 100. The metal layer 150 may be arranged to contact the scattering prevention surface 110. For this purpose, the metal layer 150 may be coated on the scattering prevention surface 110 of the gain material 100. The same reference numerals are used for the same configuration as in the foregoing embodiment, and repeated descriptions will be omitted.

[0079] Because the anti-scattering surface 110 has a flat surface, it can be closely attached to the metal layer 150 while minimizing the gap between the metal layer 150 and the anti-scattering surface 110.

[0080] The metal layer 150 can reflect pump beams PB1, PB2, and PB3 that attempt to escape from the gain material 100. Even though the scattering prevention surface 110 of the gain material 100 has a flat surface as described above, it is difficult to actually have a completely smooth surface. Therefore, although negligible, scattering or diffuse reflection occurs on the scattering prevention surface 110, and in the process, there is a possibility that a portion of the pump beam PB may escape from the gain material 100.

[0081] In the light amplifier 20 according to the embodiment, the metal layer 150 is arranged on the outer contour of the gain material 100, thereby preventing a portion of the pump beam PB from slipping out of the gain material 100 and reflecting it into the gain material 100.

[0082] The material of the metal layer 150 can be determined by considering the wavelength of the pump beam PB and its reflectivity. The metal layer 150 may include a material that has a reflectivity of 95% or higher to the pump beam PB. For example, the metal layer 150 may include a material that has a reflectivity of 95% or higher at the total internal reflection angle for the pump beam PB incident on the interior of the gain material 100.

[0083] The material of the metal layer 150 may include at least one of copper (Cu), aluminum (Al), gold (Au), silver (Ag), tungsten (W), and molybdenum (Mo).

[0084] The metal layer 150 can reflect the pump beam PB, whose angle is greater than the total internal reflection angle, back inward. Therefore, the pump beam PB can be reused, and the design can be flexibly modified, such as by designing the divergence angle of the pump beam PB to be large.

[0085] The thermal conductivity of the metal layer 150 can be greater than that of the gain material 100. Therefore, it is possible to perform the function of causing the gain material 100 to release heat. By improving the thermal conductivity of the gain material 100, the temperature difference within the gain material 100 can be reduced. This minimizes side effects caused by unintended heating of the gain material 100, such as thermal lensing, thermal stresses, photoelastic effects, and stress birefringence.

[0086] Figure 8 A diagram illustrating an optical amplifier 20B according to another embodiment. (Refer to...) Figure 8 The light amplifier 20B may further include a heat-dissipating structure 300, which includes a trench 310 for accommodating the gain material 100.

[0087] The heat generated in the gain material 100 can be released to the outside through the heat-releasing structure 300.

[0088] The heat-dissipating structure 300 may include a material whose thermal conductivity is greater than that of the gain material 100. For example, the material of the heat-dissipating structure 300 may include copper. However, the material of the heat-dissipating structure 300 is not limited to this; it can be changed to various materials as long as its thermal conductivity is greater than that of the gain material 100.

[0089] The heat-dissipating structure 300 may include a material whose thermal conductivity is greater than that of the metal layer 150.

[0090] By improving the thermal conductivity of the gain material 100 through the metal layer 150 and the heat-dissipating structure 300, the temperature difference within the gain material 100 can be reduced. This minimizes the undesirable thermal lensing phenomenon of the gain material 100.

[0091] Although the above embodiments primarily describe an example of gain material 100 being surrounded by metal layer 150, metal layer 150 is an optional configuration and can be omitted as needed. For example, although not illustrated, light amplifier 20B may have a structure that excludes metal layer 150, allowing gain material 100 to directly contact heat-dissipating structure 300.

[0092] Figures 9A to 9E A diagram illustrating examples of the cross-sectional shapes of gain materials 100, 100A, 100B, 100C, and 100D according to embodiments. Figure 10 This is a diagram used to describe the movement of the signal beam SB.

[0093] Reference Figure 9A The gain material 100 can have a cylindrical shape, and its cross-sectional shape can be circular. However, the cross-sectional shape of the gain material 100 is not limited to this, and it can be deformed into various shapes.

[0094] like Figure 10 As shown, the signal beam SB can move in a spiral pattern within the gain material 100, rather than in a straight line (indicated by dashed lines). In this case, the signal beam SB can pass through the periphery of the gain material 100 without passing through its center.

[0095] Considering that the signal beam SB can pass through the periphery as described above, the cross-sectional shapes of the gain materials 100A, 100B, 100C, and 100D can be designed to have shapes other than circular. Thus, the signal beam SB passing through the periphery of the gain material 100 can be reflected by the scattering prevention surface 110 of the gain material 100, thereby inducing the signal beam SB to pass through the center of the gain material 100.

[0096] For example, the gain materials 100A, 100B, 100C, and 100D can be polygonal in shape, or can have at least partially asymmetrical shapes. For example, the gain materials 100A, 100B, 100C, and 100D can have shapes such as... Figure 9B The octagon shown, such as Figure 9C The hexagon shown, such as Figure 9D The rounded quadrilateral shown, or as... Figure 9E The shape shown is an ellipse.

[0097] In the foregoing embodiments, the description focuses on the optical amplifier 20 employing forward pumping. Forward pumping refers to the method of incident the gain material with the pump beam PB in the same direction as the signal beam SB.

[0098] However, light amplifiers 21 and 22 are not limited to this and can be applied to, for example Figure 11 The back-pumping method shown depicts the pump beam PB incident on the gain material 100 in a direction opposite to that of the signal beam SB. Alternatively, it can be applied as follows: Figure 12 The diagram illustrates a bi-pumping method where the pump beam PB is incident on the first surface 101 and the second surface 102 of the gain material 100. For convenience, in... Figure 12 The illustration of dump 24 is omitted. In the optical amplifier 22 using the dual-pump method, the temperature distribution of the gain material 100 can be more uniform compared to optical amplifiers 20 and 21 using other pump methods.

[0099] The optical amplifier and laser processing apparatus according to embodiments of the present invention can improve amplification efficiency by minimizing the amount of pump beam that unintentionally leaks out or scatters from the interior of the gain material.

[0100] The optical amplifier and laser processing apparatus according to embodiments of the present invention can reduce the temperature difference inside the gain material by improving the thermal conductivity of the gain material, thereby minimizing the side effects caused by heat generation.

[0101] According to embodiments of the present invention, the optical amplifier and laser processing apparatus can further utilize a pump beam with a large divergence angle to improve the amplification efficiency of the signal beam inside the gain material.

[0102] Although embodiments of the invention have been described above, they are merely exemplary, and those skilled in the art will understand that various modifications and equivalent embodiments can be implemented based on these embodiments.

[0103] Symbol Explanation

[0104] 1: Laser processing device; 10: Laser oscillator

[0105] 20, 20A, 20B: Optical amplifiers; 30: Optical components

[0106] 31: Cluster lens; 32: Reflector

[0107] 100: Gain material; 101: First surface

[0108] 102: Second surface; 110: Scattering prevention surface

[0109] 121: First Concentration Area; 122: Second Concentration Area

[0110] 131: First divergence region; 132: Second divergence region

[0111] 150: Metal layer 200: Pump source

[0112] 300: Heat-dissipating structure; SB: Signal beam.

[0113] PB: Pump Beam

Claims

1. An optical amplifier, comprising: A gain medium having a first surface on which a signal beam is incident and a second surface disposed opposite the first surface, wherein the incident signal beam is amplified during its movement to the second surface and exits through the second surface; and A pump source, connected to the gain material, provides a pump beam to at least one of the first and second surfaces. The gain material includes a scattering prevention surface that connects the first surface and the second surface and reflects the pump beam during its movement toward either the first or second surface. The light amplifier also includes: A metal layer is disposed on the outer contour of the scattering-preventing surface, such that it is in contact with the scattering-preventing surface. The signal beam is configured to pass through a concentrated region of the pump beam, which is focused by the scattering-prevented surface. The metal layer comprises a material having a reflectivity of 95% or higher to the pump beam at the total internal reflection angle when the pump beam is incident on the interior of the gain material, thereby reflecting the pump beam. In the concentrated region, the minimum diameter of the pump beam is smaller than the minimum diameter of the signal beam.

2. The optical amplifier according to claim 1, wherein, The surface flatness of the scattering prevention surface is λ / 1 or less.

3. The optical amplifier according to claim 1, wherein, The gain material includes: A first concentrated region in which the pump beam is concentrated; a first diverging region in which the pump beam diverges through the first concentrated region; a second concentrated region in which the pump beam, which passes through the first diverging region and is concentrated by the scattering to prevent surface reflection; and a second diverging region in which the pump beam diverges through the second concentrated region.

4. The optical amplifier according to claim 1, wherein, The length of the gain material is 10 times or more and 100 times or less than the width of the gain material.

5. The optical amplifier according to claim 1, further comprising: A heat-generating structure comprising grooves for accommodating the gain material.

6. The optical amplifier according to claim 5, wherein, The thermal conductivity of the heat-exothermic structure is greater than that of the gain material.

7. The optical amplifier according to claim 1, wherein, The cross-sectional shape in the direction perpendicular to the length of the gain material is at least one of a circle, an ellipse, and a polygon.

8. A laser processing apparatus, comprising: A laser oscillator that generates a signal beam; as well as An optical amplifier that amplifies the signal beam generated by the laser oscillator. The light amplifier includes: A gain material having a first surface on which the signal beam is incident and a second surface disposed opposite the first surface, wherein the incident signal beam is amplified and exits through the second surface during its movement to the second surface; and A pump source, connected to the gain material, provides a pump beam to at least one of the first and second surfaces. The gain material includes a scattering prevention surface that connects the first surface and the second surface and reflects the pump beam during its movement toward either the first or second surface. The light amplifier also includes: A metal layer is disposed on the outer contour of the scattering-preventing surface, such that it is in contact with the scattering-preventing surface. The signal beam is configured to pass through a concentrated region of the pump beam, which is focused by the scattering-prevented surface. The metal layer comprises a material having a reflectivity of 95% or higher to the pump beam at the total internal reflection angle when the pump beam is incident on the interior of the gain material, thereby reflecting the pump beam. In the concentrated region, the minimum diameter of the pump beam is smaller than the minimum diameter of the signal beam.

9. The laser processing apparatus according to claim 8, wherein, The surface flatness of the scattering prevention surface is λ / 1 or less.

10. The laser processing apparatus according to claim 8, wherein, The gain material includes: A first concentrated region in which the pump beam is concentrated; a first diverging region in which the pump beam diverges through the first concentrated region; a second concentrated region in which the pump beam, which passes through the first diverging region and is concentrated by the scattering to prevent surface reflection; and a second diverging region in which the pump beam diverges through the second concentrated region.

11. The laser processing apparatus according to claim 8, wherein, The length of the gain material is 10 times or more and 100 times or less than the width of the gain material.

12. The laser processing apparatus according to claim 8, further comprising: A heat-generating structure comprising grooves for accommodating the gain material.

13. The laser processing apparatus according to claim 12, wherein, The thermal conductivity of the heat-exothermic structure is greater than that of the gain material.

14. The laser processing apparatus according to claim 8, wherein, The cross-sectional shape in the direction perpendicular to the length of the gain material is at least one of a circle, an ellipse, and a polygon.

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