KR102359965B1 - Optical amplifier and laser processing apparatus including the same - Google Patents

Abstract

Disclosed are an optical amplifier and a laser processing device comprising the same. The disclosed optical amplifier comprises: a gain material having a first surface on which a signal beam is incident and a second surface disposed on an opposite side to the first surface, and amplified while the incident signal beam moves to the second surface and is emitted to the second surface; and a pumping source connected to provide a pump beam to at least one surface among the first surface and the second surface, wherein the gain material comprises a scattering-prevention surface connecting the first surface and the second surface and reflecting the pump beam while the pump beam moves toward the first surface or the second surface, and the signal beam may be configured to pass through a concentration area where the pump beam is reflected and focused by the scattering-prevention surface. Therefore, the present invention is capable of improving an efficiency of amplification.

Description

Optical amplifier and laser processing apparatus including the same

The present invention relates to an optical amplifier and a laser processing apparatus including the same.

In general, a laser processing apparatus refers to an apparatus for condensing a laser beam in the form of a single focus using a condensing lens, and irradiating the focus to the surface or the inside of an object to be processed.

Such a laser processing apparatus may include an oscillator for generating a signal beam, and an optical amplifier for amplifying the signal beam generated by the oscillator.

The optical amplifier may include a gain material capable of amplifying the signal beam and a pumping source providing a pump beam to the gain material to induce a density reversal within the gain material.

The amplification efficiency of the optical amplifier may vary depending on the amount of unintentional escaping or scattering of a pump beam incident inside the gain material.

The present invention provides an optical amplifier and a laser processing apparatus having improved amplification efficiency by minimizing the amount of a pump beam that is unintentionally escaping or scattered inside a gain material.

The present invention provides an optical amplifier and a laser processing apparatus capable of reducing the temperature difference inside the gain material by improving the heat conduction efficiency of the gain material.

The present invention provides an optical amplifier and a laser processing apparatus that improve the amplification efficiency of a signal beam in a gain material through reuse of a pump beam having a large divergence angle.

An optical amplifier according to an aspect of the present invention,

A gain that has a first surface on which a signal beam is incident and a second surface disposed on the opposite side to the first surface, and is amplified while the incident signal beam moves to the second surface and is emitted to the second surface matter; and

a pumping source coupled to provide a pump beam to at least one of the first side and the second side;

the gain material includes an anti-scattering surface connecting the first surface and the second surface and reflecting the pump beam while the pump beam moves toward the first surface or the second surface;

The signal beam may be configured to pass through a concentration area where the pump beam is reflected and focused by the anti-scattering surface.

The surface flatness of the scattering prevention surface may be lambda (λ)/1 or less.

The gain material includes a first concentration area where the pump beam is focused, a first divergent area where the pump beam is diverged past the first concentration area, and a first divergent area that is reflected by the anti-scattering surface It may include a second concentration area to be focused, and a second diverging area from which the pump beam is diverged through the second concentration area.

The length of the gain material may be 10 times or more and 100 times or less the width of the gain material.

The optical amplifier may further include a metal layer disposed outside the scattering prevention surface.

The metal layer may include a material having a reflectance of 95% or more with respect to the pump beam.

The optical amplifier may further include a heat dissipation structure including a groove for accommodating the gain material.

A thermal conductivity of the heating structure may be greater than a thermal conductivity of the gain material.

A cross-sectional shape in a direction perpendicular to the longitudinal direction of the gain material may be at least one of a circle, an ellipse, and a polygon.

Laser processing apparatus according to another aspect of the present invention,

a laser oscillator that generates a signal beam;

Including; an optical amplifier for amplifying the signal beam generated by the oscillator;

The optical amplifier is

It has a first surface on which the signal beam is incident, and a second surface disposed on the opposite side to the first surface, and is amplified while the incident signal beam moves to the second surface and is emitted to the second surface. gain substance; and

a pumping source coupled to provide a pump beam to at least one of the first side and the second side;

the gain material includes an anti-scattering surface connecting the first surface and the second surface and reflecting the pump beam while the pump beam moves toward the first surface or the second surface;

The signal beam may be configured to pass through a concentration area where the pump beam is reflected and focused by the anti-scattering surface.

The surface flatness of the scattering prevention surface may be lambda (λ)/1 or less.

The gain material includes a first concentration area where the pump beam is focused, a first divergent area where the pump beam is diverged past the first concentration area, and a first divergent area that is reflected by the anti-scattering surface It may include a second concentration area to be focused, and a second diverging area from which the pump beam is diverged through the second concentration area.

The length of the gain material may be 10 times or more and 100 times or less the width of the gain material.

The optical amplifier may further include a metal layer disposed outside the scattering prevention surface.

The metal layer may include a material having a reflectance of 95% or more with respect to the pump beam.

The optical amplifier may further include a heat dissipation structure including a groove for accommodating the gain material.

A thermal conductivity of the heating structure may be greater than a thermal conductivity of the gain material.

A cross-sectional shape in a direction perpendicular to the longitudinal direction of the gain material may be at least one of a circle, an ellipse, and a polygon.

The optical amplifier and the laser processing apparatus according to an embodiment of the present invention minimize the amount of the pump beam that is unintentionally escaping or scattered inside the gain material, thereby improving amplification efficiency.

The optical amplifier and the laser processing apparatus according to an embodiment of the present invention can reduce the temperature difference inside the gain material by improving the heat conduction efficiency of the gain material, thereby minimizing side effects due to heat generation.

The optical amplifier and the laser processing apparatus according to the embodiment of the present invention can improve the amplification efficiency of the signal beam in the gain material through the reuse of the pump beam having a large divergent angle.

1 is a view conceptually showing a laser processing apparatus according to an embodiment.
2 is a diagram conceptually illustrating an optical amplifier according to an embodiment.
3 shows an optical amplifier according to an embodiment.
4 is a view for explaining the anti-scattering surface of the gain material according to the embodiment,
5 is a view for explaining diffuse reflection in a gain material according to a comparative example.
6 is a diagram illustrating an optical amplifier according to another embodiment.
FIG. 7 is an enlarged view of a part of FIG. 6 .
8 is a view for explaining an optical amplifier according to another embodiment.
9A to 9E are diagrams for explaining an example of a cross-sectional shape of a gain material according to an embodiment.
10 is a diagram for explaining movement of a signal beam.
11 and 12 are diagrams conceptually illustrating an optical amplifier according to another embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals refer to the same components, and the size or thickness of each component may be exaggerated for clarity of description.

Terms including an ordinal number such as “first” and “second” may be used to describe various elements, but the elements are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component. The term “and/or” includes a combination of a plurality of related items or any one of a plurality of related items.

1 is a view conceptually showing a laser processing apparatus 1 according to an embodiment. 2 is a diagram conceptually illustrating an optical amplifier according to an embodiment.

1 and 2 , the laser processing apparatus 1 may include a laser oscillator 10 and an optical amplifier 20 .

The laser oscillator 10 may generate a signal beam SB. The laser oscillator 10 transmits the signal beam SB to the optical amplifier 20 . The signal beam SB may be a pulsed laser beam.

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

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 to the first surface 101 . The gain material 100 may include active ions obtained from rare earth elements such as ytterbium (Yb), neodymium (Nd), erbium (Er), and thulium (Tm). Also, the gain material 100 may include active ions obtained from transition metal elements such as chromium (Cr) and titanium (Ti).

The pumping source 200 may be connected to provide a pump beam PB to at least one of the first side 101 and the second side 102 of the gain material 100 . For example, the pumping source 200 may be connected to provide a pump beam PB to the first side 101 of the gain material 100 . The pump beam PB provided by the pumping source 200 is incident on the first surface 101 , and density inversion occurs in the gain material 100 by the incident pump beam PB. When the signal beam SB passes through the gain material 100 in which the density inversion has occurred, the signal beam SB is amplified.

An optical member 30 may be disposed between the pumping source 200 and the gain material 100 to focus the pump beam PB into the gain material 100 . As an example, the optical member 30 may include at least one of a focusing lens 31 for condensing the pump beam PB and a reflection mirror 32 for changing the direction of the pump beam PB. The pump beam PB that has passed through the gain material 100 may be reflected by the reflective mirror 33 and then absorbed by the dump 34. FIG. 3 shows an optical amplifier 20 according to one embodiment. did it

Referring to FIG. 3 , the gain material 100 may have a rod-type shape extending from the first surface 101 to the second surface 102 .

The gain material 100 may have a predetermined length L. For example, the length L of the gain material 100 may be 10 times or more and 100 times or less the width D of the gain material 100 . The width D of the gain material 100 may be expressed as a diameter when the gain material 100 has a cylindrical shape.

The width D of the gain material 100 may be 2 mm or less. The length L of the gain material 100 may be 100 mm or less.

Both the signal beam SB and the pump beam PB may be incident in the longitudinal direction of the gain material 100 . For example, the signal beam SB and the pump beam PB may be incident on the first surface 101 that is the same surface of the gain material 100 . However, the present invention is not necessarily limited thereto, and may be variously modified if the signal beam SB and the pump beam PB are incident in the longitudinal direction of the gain material 100 . For example, the pump beam PB is incident on the second surface 102 that is the exit surface of the signal beam SB (see FIG. 11 ), or the first surface 101 that is the incident surface of the signal beam SB and It may be incident (refer to FIG. 12) to the second surface 102, which is an exit surface.

The gain material 100 includes an anti-scattering surface 110 connecting the first surface 101 and the second surface 102 .

The anti-scattering surface 110 reflects the pump beam PB moving toward at least one of the first surface 101 and the second surface 102 inside the gain material 100 , but the pump beam PB ) may be configured to prevent diffuse reflection inside the gain material 100 .

When the pump beam PB is incident on the first surface 101 of the gain material 100 , the anti-scattering surface 110 moves toward the second surface 102 from the inside of the gain material 100 . It may be configured to reflect PB, but prevent the pump beam PB from being diffusely reflected inside the gain material 100 .

4 is a view for explaining the scattering prevention surface 110 of the gain material 100 according to the embodiment, and FIG. 5 is a view for explaining diffuse reflection in the gain material 100 according to the comparative example.

The anti-scattering surface 110 may have an optically flat surface. For example, the surface flatness (or optical flatness) of the anti-scattering surface 110 may be lambda (λ)/1 or less. For example, the surface flatness of the scattering prevention surface 110 may be lambda (λ)/2 or less. For example, the surface flatness of the anti-scattering surface 110 may be lambda (λ)/4 or less. For example, the surface flatness of the anti-scattering surface 110 may be lambda (λ)/8 or less. To this end, the outer surface of the gain material 100 may be treated by optical polishing.

Referring to FIG. 4 , the anti-scattering surface 110 constantly reflects the pump beams PB1 , PB2 , and PB3 , so that the pump beams PB1 , PB2 , and PB3 are focused in a predetermined area inside the gain material 100 . It can be done, and it is possible to prevent the pump beam PB from being unintentionally escaping to the outside due to diffuse reflection.

On the other hand, referring to FIG. 5 , when the gain material 1000 does not have the anti-scattering surface 110 , that is, when it has a non-planar surface 1100 , the pump beams PB1 , PB2 , and PB3 are gain The surface 1100 of the material 100 may diffusely reflect, and some pump beams PB2 and PB3 may escape to the outside.

Referring back to FIG. 3 , the pump beam PB may be incident to be focused on a predetermined position of the gain material 100 . As the pump beam PB is reflected by the anti-scattering surface 110 , a plurality of concentration regions 121 , 122 , and 123 appear in the gain material 100 .

The gain material 100 includes a first concentration region 121 on which the pump beam PB is focused, a first diverging region 131 on which the pump beam PB is diverged through the first concentration region 121, and a second A second concentration region 122 that passes through the first divergent region 131 and is reflected and concentrated by the scattering prevention surface 110 , and a second divergent region where the pump beam PB is diverged through the second concentration region 122 . region 132 . The gain material 100 may further include a third concentrating region 123 that passes through the second divergence region 132 and is reflected and concentrated by the scattering prevention surface 110 .

The pump beam PB may be relatively focused on the concentration regions 121 , 122 , and 123 in the gain material 100 . Accordingly, the amount of amplification of the signal beam SB while passing through the concentration regions 121 , 122 , and 123 is greater than the amount of amplification of the signal beam SB while passing through the diverging regions 131 and 132 .

The minimum diameter D1 of the pump beam PB in the concentration areas 121 , 122 , and 123 may be less than or equal to 1/2 of the maximum diameter of the pump beam PB in the diverging areas 131 and 132 . For example, the minimum diameter D1 of the pump beam PB in the concentration regions 121 , 122 , and 123 may be 1/5 or less of the maximum diameter of the pump beam PB in the diverging regions 131 and 132 . For example, the minimum diameter D1 of the pump beam PB in the concentration regions 121 , 122 , and 123 may be less than or equal to 1/10 of the maximum diameter of the pump beam PB in the diverging regions 131 and 132 . The maximum diameter of the pump beam PB in the diverging regions 131 and 132 may be equal to the width D (or diameter) of the gain material 100 .

In the optical amplifiers 20 and 20 according to the embodiment, a plurality of concentration regions 121 , 122 , and 123 appear in the gain material 100 by the scattering prevention surface 110 , and the signal beam SB is As the plurality of concentration regions 121 , 122 , and 123 pass, amplification efficiency may be improved.

The minimum diameter D1 of the pump beam PB in the concentration areas 121 , 122 , and 123 may be smaller than the minimum diameter of the signal beam SB passing through the gain material 100 .

6 is a view showing an optical amplifier 20A according to another embodiment. FIG. 7 is an enlarged view of a part of FIG. 6 .

6 and 7 , the optical amplifier 20A according to the embodiment may further include a metal layer 150 disposed outside the gain material 100 . The metal layer 150 may be disposed to contact the scattering prevention surface 110 . To this end, the metal layer 150 may be coated on the anti-scattering surface 110 of the gain material 100 . Configurations overlapping those of the above-described embodiment are denoted by the same reference numerals, and overlapping descriptions will be omitted.

Since the scattering prevention surface 110 has a flat surface, a gap between the metal layer 150 and the scattering prevention surface 110 may be minimized and adhered thereto.

The metal layer 150 may reflect the pump beams PB1 , PB2 , and PB3 that are about to escape to the outside of the gain material 100 . As described above, even if the anti-scattering surface 110 of the gain material 100 has a flat surface, it is difficult to actually have a perfectly flat surface. Accordingly, although weak, scattering or diffuse reflection appears on the anti-scattering surface 110 , and in the process, there is a possibility that some of the pump beams PB may escape to the outside of the gain material 100 .

In the optical amplifier 20 according to the embodiment, since the metal layer 150 is disposed outside the gain material 100 , some pump beams PB are prevented from escaping to the outside of the gain material 100 . and may be reflected into the gain material 100 .

The material of the metal layer 150 may be determined in consideration of the wavelength of the pump beam PB and its reflectance. The metal layer 150 may include a material having a reflectance of 95% or more with respect to the pump beam PB. For example, the metal layer 150 may include a material having a reflectance of 95% or more at a total reflection angle of the pump beam PB incident into the gain material 100 .

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).

Meanwhile, the metal layer 150 may reflect the pump beam PB at an angle greater than the total reflection angle back to the inside. Accordingly, the pump beam PB can be reused, and free design changes such as designing a large divergent angle of the pump beam PB are possible.

The metal layer 150 may have higher thermal conductivity than the gain material 100 . Accordingly, the gain material 100 may perform a function of dissipating heat. By improving the heat conduction efficiency of the gain material 100 , a temperature difference inside the gain material 100 may be reduced. Accordingly, unintended side effects due to heat generation of the gain material 100, for example, thermal lensing, thermal stresses, photoelastic effects, and stress birefringence. can be minimized.

8 is a view for explaining an optical amplifier 20B according to another embodiment. Referring to FIG. 8 , the optical amplifier 20B may further include a heat dissipation structure 300 including a groove 310 for accommodating the gain material 100 .

Through the heat dissipation structure 300 , heat generated in the gain material 100 may be dissipated to the outside.

The heat dissipation structure 300 may include a material having a higher thermal conductivity than the gain material 100 . For example, the material of the heat dissipation structure 300 may include copper. However, the material of the heat dissipation structure 300 is not limited thereto, and may be variously deformed because it is a material having a higher thermal conductivity than the gain material 100 .

The heat dissipation structure 300 may include a material having a higher thermal conductivity than the metal layer 150 .

By improving the heat conduction efficiency of the gain material 100 through the metal layer 150 and the heat dissipation structure 300 , a temperature difference inside the gain material 100 may be reduced. Accordingly, unintentional thermal lensing of the gain material 100 may be minimized.

Although the above-described embodiment has been mainly described with respect to an example in which the gain material 100 is surrounded by the metal layer 150 , the metal layer 150 is an optional configuration and may be omitted if necessary. For example, although not shown, the optical amplifier 20B may have a structure in which the gain material 100 directly contacts the heat dissipation structure 300 without the metal layer 150 .

9A to 9E are views for explaining examples of cross-sectional shapes of gain materials 100 , 100A, 100B, 100C, and 100D according to an embodiment. 10 is a diagram for explaining the movement of the signal beam SB.

Referring to FIG. 9A , the gain material 100 may have a cylindrical shape, and a cross-sectional shape thereof may be circular. However, the cross-sectional shape of the gain material 100 is not limited thereto, and may be variously deformed.

The signal beam SB does not move in a straight line (indicated by a dotted line) within the gain material 100 as shown in FIG. 10 , but may move in a spiral form. In this case, the signal beam SB may pass through the peripheral portion of the gain material 100 without passing through the central portion.

As described above, in consideration of the fact that the signal beam SB may pass through the peripheral portion, the cross-sectional shape of the gain materials 100A, 100B, 100C, and 100D may be designed to have a shape other than a circular shape. In this way, the signal beam SB passing through the periphery of the gain material 100 may be reflected by the anti-scattering surface 110 of the gain material 100 , so that the signal beam SB passes through the gain material 100 . ) can be induced to pass through the center of the

For example, the cross-sectional shape of the gain materials 100A, 100B, 100C, and 100D may be a polygonal shape or may be at least partially asymmetrical. For example, the cross-sectional shape of the gain materials 100A, 100B, 100C, 100D is an octagonal shape as shown in FIG. 9B, a hexagonal shape as shown in FIG. 9C, a rectangular shape with rounded corners as shown in FIG. 9D, or a rectangular shape as shown in FIG. 9E. It may have an elliptical shape.

Meanwhile, in the above-described embodiment, the optical amplifier 20 to which the forward pumping method, in which the pump beam PB and the signal beam SB are incident on the gain material 100 in the same direction, is applied will be mainly described. did

However, the optical amplifiers 21 and 22 are not limited thereto, and as shown in FIG. 11 , a backward pumping method in which the pump beam PB is incident on the gain material 100 in the opposite direction to the signal beam SB. is applied, or a bi-pumping method in which the pump beam PB is incident on the first surface 101 and the second surface 102 of the gain material 100 as shown in FIG. 12 may be applied. In FIG. 12 , illustration of the dump 24 is omitted for convenience. In the optical amplifier 22 to which the bi-pumping method is applied, the temperature distribution of the gain material 100 may be uniform compared to the optical amplifiers 20 and 21 to which other pumping methods are applied.

Although the embodiments of the present invention have been described above, these are merely exemplary, and those of ordinary skill in the art will understand that various modifications and equivalent other embodiments are possible therefrom.

1: laser processing device 10: laser oscillator
20, 20A, 20B: optical amplifier 30: optical member
31: focusing lens 32: reflective mirror
100: gain material 101: first side
102: second surface 110: anti-scattering surface
121: first concentration area 122: second concentration area
131: first diverging region 132: second diverging region
150: metal layer 200: pumping source
300: heat dissipation structure SB: signal beam
PB : pump beam

Claims (18)

An optical amplifier comprising:
A gain that has a first surface on which the signal beam is incident and a second surface disposed on the opposite side to the first surface, and is amplified and output to the second surface while the incident signal beam moves to the second surface matter; and
a pumping source coupled to provide a pump beam to at least one of the first side and the second side;
the gain material comprises an anti-scattering surface connecting the first surface and the second surface and reflecting the pump beam while the pump beam moves toward the first surface or the second surface;
The optical amplifier further includes a metal layer disposed outside the scattering prevention surface in contact with the scattering prevention surface,
The signal beam is configured to pass through a concentration area where the pump beam is reflected and focused by the anti-scattering surface,
The metal layer includes a material having a reflectance of 95% or more with respect to the pump beam to reflect the pump beam. According to claim 1,
and a surface flatness of the anti-scattering surface is lambda (λ)/1 or less. According to claim 1,
The gain material is
A first concentration area where the pump beam is focused, a first divergent area where the pump beam is diverged through the first concentration area, and a second area where the pump beam is focused through the first diverging area and reflected by the scattering prevention surface An optical amplifier comprising: a concentration region; and a second divergent region through which the pump beam diverges past the second concentration region. According to claim 1,
and a length of the gain material is at least 10 times and no more than 100 times a width of the gain material. delete delete According to claim 1,
and a heat dissipation structure including a groove for receiving the gain material. 8. The method of claim 7,
and a thermal conductivity of the heat dissipation structure is greater than a thermal conductivity of the gain material. The method of claim 1,
and a cross-sectional shape in a direction perpendicular to the longitudinal direction of the gain material is at least one of a circle, an ellipse, and a polygon. a laser oscillator that generates a signal beam;
Including; an optical amplifier for amplifying the signal beam generated by the oscillator;
The optical amplifier is
It has a first surface on which the signal beam is incident, and a second surface disposed on the opposite side to the first surface, and is amplified while the incident signal beam moves to the second surface and is emitted to the second surface. gain substance; and
a pumping source coupled to provide a pump beam to at least one of the first side and the second side;
the gain material includes an anti-scattering surface connecting the first surface and the second surface and reflecting the pump beam while the pump beam moves toward the first surface or the second surface;
The optical amplifier further includes a metal layer disposed outside the scattering prevention surface in contact with the scattering prevention surface,
The signal beam is configured to pass through a concentration area where the pump beam is reflected and focused by the anti-scattering surface,
The metal layer includes a material having a reflectance of 95% or more with respect to the pump beam to reflect the pump beam. 11. The method of claim 10,
The surface flatness of the scattering prevention surface is lambda (λ)/1 or less, laser processing apparatus. 11. The method of claim 10,
The gain material is
A first concentration area where the pump beam is focused, a first divergent area where the pump beam is diverged through the first concentration area, and a second area where the pump beam is focused through the first diverging area and reflected by the scattering prevention surface A laser processing apparatus comprising: a concentration area; and a second divergent area through which the pump beam diverges past the second concentration area. 11. The method of claim 10,
The length of the gain material is not less than 10 times and not more than 100 times the width of the gain material, laser processing apparatus. delete delete 11. The method of claim 10,
Further comprising a heat dissipation structure including a groove for receiving the gain material, laser processing apparatus. 17. The method of claim 16,
wherein the thermal conductivity of the heat dissipation structure is greater than the thermal conductivity of the gain material. 11. The method of claim 10,
A cross-sectional shape in a direction perpendicular to the longitudinal direction of the gain material is at least one of a circle, an ellipse, and a polygon.

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