Optical amplifier and laser processing apparatus including same

Abstract

An optical amplifier is disclosed. The optical amplifier includes: a gain medium which has a first surface on which a seed beam is incident, a second surface positioned opposite to the first surface, and a side surface connecting the first surface and the second surface, and in which the incident seed beam is amplified while moving to the second surface and emitted to the second surface; and a pumping source providing a pump beam to at least one of the first surface or the second surface, wherein a pump beam removal region is provided in one region of the side surface of the gain medium, the pump beam removal region being surface-treated so that at least a portion of the pump beam existing inside the gain medium is emitted to the outside of the gain medium, and the pump beam removal region is located closer to the first surface than a region in which the pump beam is first reflected from the side surface of the gain medium.

Description

Optical amplifier and laser processing device including the same

[0001] The present disclosure relates to an optical amplifier and a laser processing device including the same.

[0002] A laser processing device is a device that uses a focusing lens to focus a laser beam into a single focus and irradiates the focus onto the surface or inside of a processing target to process it.

[0003] The laser processing device may include a laser generator that generates a seed beam and an optical amplifier that amplifies the seed beam.

[0004] The optical amplifier may include a gain medium capable of amplifying a seed beam, and a pumping source providing a pump beam to the gain medium to induce density inversion within the gain medium.

[0005] To improve the amplification efficiency of an optical amplifier, it is important to prevent the pump beam incident on the inside of the gain medium from unintentionally escaping outside the gain medium. However, unnecessary pump beams need to be removed from the gain medium, as they can reduce the amplification efficiency of the optical amplifier or damage the laser oscillator. Unwanted pump beams may include pump beams with unintended incidence directions and properties, or pump beams incident from outside. For example, a "backward signal" that propagates in the opposite direction of the seed beam's emission direction within or on the surface of the gain medium is an example.

[0006] A 'backward signal' refers to a pump beam that propagates in the opposite direction to the emission direction of the seed beam within or on the surface of the gain medium. The backward signal may be emitted outside the gain medium through the entrance surface of the gain medium into which the seed beam is input. In particular, in a multi-stage amplification system, if the backward signal enters the gain medium of the previous stage, the amplification efficiency of the multi-stage amplification system may be reduced, which may reduce the output of the seed beam or deteriorate the laser quality. In addition, the backward signal may be amplified and flow back to the laser oscillator that generates the seed beam, thereby damaging the laser oscillator.

[0007] Therefore, a technology to reduce backward signals is required.

[0008] The technical problem to be solved by the present invention is to provide an optical amplifier capable of removing unnecessary pump beams that may impair the amplification efficiency or safety of the optical amplifier.

[0009] Another technical problem to be solved by the present invention is to provide an optical amplifier in which the generation of backward signals within a gain medium is reduced.

[0010] Another technical problem that the present invention seeks to solve is to provide an optical amplifier that amplifies a backward signal that enters a gain material and attenuates the backward signal without sending it to the previous stage.

[0011] The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art of the present invention from the description below.

[0012] According to one embodiment of the present disclosure, an optical amplifier may be provided, including: a gain medium having a first surface onto which a seed beam is incident; a second surface located opposite the first surface; and a side surface connecting the first surface and the second surface, wherein the incident seed beam is amplified while traveling to the second surface and is emitted to the second surface; and a pumping source providing a pump beam to at least one surface of the first surface or the second surface; wherein a pump beam removal region is provided in an area of ​​the side surface of the gain medium, the pump beam removal region being surface-treated so that at least a portion of the pump beam existing inside the gain medium is emitted to the outside of the gain medium, and wherein the pump beam removal region is positioned closer to the first surface than an area where the pump beam is first reflected from the side surface of the gain medium.

[0013] The surface treatment comprises at least one of sanding, etching or line processing, and the gain medium in the pump beam removal region may have a non-flat surface with an uneven depth.

[0014] The gain medium further includes an additional pump beam removal region positioned on the side adjacent to the second surface, and a length of the additional pump beam removal region may be greater than a length of the pump beam removal region.

[0015] The optical amplifier further includes a heat dissipation structure surrounding at least a portion of the side surface of the gain medium; and a filling layer provided between the gain medium and the heat dissipation structure; wherein the filling layer may have a flat surface.

[0016] The optical amplifier further includes a metal layer surrounding the side surface of the gain medium, wherein the metal layer includes a first surface in contact with the gain medium and a second surface opposite the first surface, and the first surface may be uneven along the contour of the uneven surface of the gain medium in a first region corresponding to the pump beam removal region, and may be flat in a second region not corresponding to the pump beam removal region. The second surface may be flat in the first region and the second region.

[0017] The above pump beam can be emitted outside the gain medium based on the difference in refractive index between the gain medium and the metal layer.

[0018] The above second surface may have a shape inclined at a first angle preset based on the first axis.

[0019] The above first surface may have a shape inclined at a preset second angle based on a second axis that is perpendicular to the first axis.

[0020] The above-described first angle and the above-described second angle may be the same.

[0021] The above gain medium may include YAG crystals added to a rare earth metal.

[0022] According to another embodiment of the present disclosure, a laser processing device may be provided, including: a laser generator for generating a seed beam; and an optical amplifier for amplifying the seed beam generated by the laser generator; wherein the optical amplifier has a first surface on which the seed beam is incident, a second surface located opposite the first surface, and a side surface connecting the first surface and the second surface, and includes a gain medium in which the incident seed beam is amplified while moving to the second surface and is emitted to the second surface; and a pumping source for providing a pump beam to at least one surface of the first surface or the second surface, wherein a pump beam removal region is provided in one area of ​​the side surface of the gain medium, the pump beam removal region being surface-treated so that at least a portion of the pump beam existing inside the gain medium is emitted to the outside of the gain medium, and the pump beam removal region is characterized in that it is located closer to the first surface than an area in which the pump beam is first reflected from the side surface of the gain medium.

[0023] The above exemplary embodiments and other exemplary embodiments will be explained or clarified by the detailed description set forth below of exemplary embodiments to be read in conjunction with the accompanying drawings.

[0024] The disclosed technology may have the following effects. However, this does not mean that a particular embodiment must include all or only the following effects, and therefore the scope of the disclosed technology should not be construed as being limited thereby.

[0025] According to one embodiment of the present disclosure, the amplification efficiency, safety, and laser quality of an optical amplifier can be improved by removing unnecessary pump beams remaining inside a gain medium.

[0026] According to another embodiment of the present disclosure, the generation of backward signals within the gain medium can be reduced, thereby improving the amplification efficiency, safety, and laser quality of the optical amplifier.

[0027] According to another embodiment of the present disclosure, the stability of an optical amplifier can be improved by attenuating a backward signal entering the gain material.

[0028] The above description of the invention is not intended to be an exhaustive list of all aspects of the present invention. It should be understood that the present invention encompasses all methods, devices, and systems capable of being implemented from all appropriate combinations of the various aspects disclosed in the detailed description and claims below, as well as the matters summarized above. Furthermore, the detailed description of the embodiments of the present disclosure will directly or implicitly disclose any benefits that may be obtained or anticipated from the embodiments of the present disclosure. For example, various anticipated benefits of the embodiments of the present disclosure will be disclosed in the detailed description that follows.

[0029] Aspects, features and advantages of specific embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings.

[0030] FIG. 1 is a schematic diagram showing an optical amplifier (100) according to one embodiment of the present disclosure.

[0031] FIG. 2 is a drawing showing a cross-section of an optical amplifier (100) according to one embodiment of the present disclosure.

[0032] FIG. 3 is a cross-sectional view for explaining the operation of an optical amplifier (100) according to one embodiment of the present disclosure.

[0033] FIG. 4 is a drawing showing a cross-section of an optical amplifier (100) according to one embodiment of the present disclosure.

[0034] FIG. 5 is a drawing showing a cross-section of an optical amplifier (100) according to another embodiment of the present disclosure.

[0035] FIG. 6 is a drawing showing a cross-section of an optical amplifier (100) according to one embodiment of the present disclosure.

[0036] FIG. 7 is a drawing showing a cross-section of an optical amplifier (100) according to another embodiment of the present disclosure.

[0037] FIG. 8 is a block diagram conceptually illustrating a laser processing device according to one embodiment of the present disclosure.

[0038] The terms used in this specification will be briefly explained, and the present disclosure will be described in detail.

[0039] The terms used in the embodiments of this disclosure have been selected from widely used, current terms, taking into account the functions of this disclosure. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, terms may be arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the description of the relevant disclosure. Therefore, the terms used in this disclosure should not be defined simply as names, but rather based on the meanings of the terms and the overall content of this disclosure.

[0040] The embodiments of the present disclosure are capable of various modifications and multiple embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the scope of the present disclosure to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the scope of the disclosed concepts and techniques. In describing the embodiments, detailed descriptions of related known technologies will be omitted if they are deemed to obscure the main point.

[0041] Terms such as "first" and "second" may be used to describe various components, but the components should not be limited by these terms. These terms are used solely to distinguish one component from another.

[0042] Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as "comprise" or "consist of" are intended to indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but should be understood not to preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0043] Below, with reference to the attached drawings, embodiments of the present disclosure are described in detail so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein. In addition, in the drawings, parts irrelevant to the description are omitted for clarity of description of the present disclosure, and similar parts are designated with similar reference numerals throughout the specification.

[0044]

[0045] FIG. 1 is a schematic diagram showing an optical amplifier (100) according to one embodiment of the present disclosure.

[0046] Referring to FIG. 1, the optical amplifier (100) may include a gain medium (110) and a heat dissipation structure (140).

[0047] The gain medium (110) may include active ions obtained from rare earth metals. Exemplary rare earth metals may include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

[0048] Additionally, the gain medium (110) may include active ions obtained from transition metal elements such as chromium (Cr), titanium (Ti), etc. For example, the gain medium (110) may be a Yttrium Aluminum Garnet (YAG) crystal to which active ions are added. In another embodiment, the gain medium (110) may be composed of a single crystal of a type other than a YAG crystal.

[0049] The gain medium (110) may have a rod shape. The gain medium (110) may have a cylindrical shape. The gain medium (110) may include a first surface, a second surface opposite the first surface, and a side surface connecting the first surface and the second surface. The first surface may be an incident surface onto which a seed beam (or a signal beam) is incident. The second surface may be an exit surface onto which an amplified seed beam is output. The pump beam may be incident on the first surface and / or the second surface. For example, the diameter of the cross-section of the gain medium (110) may be 1 mm or 1.5 mm. However, this is only an example, and the diameter of the cross-section of the gain medium (110) may be greater than 1 mm and less than 1.5 mm, or greater than 1.5 mm.

[0050] The heat dissipation structure (140) may surround at least a portion of a side surface of the gain medium (110). The heat dissipation structure (140) may include a groove (G) that accommodates the gain medium (110). The groove (G) may be a U-shaped groove.

[0051] The heat dissipation structure (140) can dissipate heat generated in the gain medium (110) to the outside. The heat dissipation structure (140) can have various shapes. For example, the heat dissipation structure (140) can be a heat sink.

[0052] The heat dissipation structure (140) may include a material having a higher thermal conductivity than the gain medium (110). For example, the material of the heat dissipation structure (140) may include copper.

[0053] By improving the heat conduction and cooling efficiency of the gain medium (110) through the heat dissipation structure (140), the temperature difference along the Y and Z axes within the gain medium (110) can be reduced. Accordingly, unintended thermal lensing of the gain medium (110) and deterioration of beam quality can be minimized.

[0054] FIG. 2 is a drawing showing a cross-section of an optical amplifier (100) according to one embodiment of the present disclosure.

[0055] Referring to FIG. 2, the optical amplifier (100) may include a gain medium (110), a metal layer (120), a filling layer (130), and a heat dissipation structure (140). The gain medium (110) serves to transmit a laser beam. Inside the gain medium (110), the laser beam (e.g., a pump beam) may propagate by total reflection. Total reflection may occur due to a difference in refractive indices between the gain medium (110) and the metal layer (120). For example, the refractive index of the gain medium (110) may be 1.82. The refractive index of the metal layer (120) may be smaller than the refractive index of the gain medium (110). For example, the refractive index of the metal layer (120) may be 0.2.

[0056] The metal layer (120) can guide the laser beam so that the laser beam propagates within the gain medium (110). The metal layer (120) can reflect the pump beam, which is trying to escape outside the gain medium (110), back into the gain medium (110). For example, the metal layer (120) can reflect the pump beam at an angle greater than the critical angle of total reflection back into the gain medium (110).

[0057] The metal layer (120) can surround the side surface of the gain medium (110). Since the metal layer (120) is arranged on the outer surface of the gain medium (110), some of the pump beams can be blocked from escaping to the outside of the gain medium (110) and reflected into the inside of the gain medium (110).

[0058] The material of the metal layer (120) may be determined in consideration of the wavelength of the pump beam and its reflectivity. The metal layer (120) may include a material having a reflectivity of 95% or more for the pump beam. For example, the metal layer (120) may include a material having a reflectivity of 95% or more at a total reflection angle for the pump beam incident on the inside of the gain medium (110).

[0059] For example, the material of the metal layer (120) may be silver. As another example, the material of the metal layer (120) may include at least one of copper (Cu), aluminum (Al), gold (Au), tungsten (W), and molybdenum (Mo).

[0060] The filling layer (130) can fix the gain medium (110) by bonding the gain medium (110) and the heat dissipation structure (140). The filling layer (130) can transfer heat generated in the gain medium (110) to the heat dissipation structure (140). For example, the filling layer (130) can be made of tin.

[0061] The pump beam that is not totally reflected by the metal layer (120) can be absorbed by the metal layer (120) and converted into thermal energy. The converted thermal energy can be released to the outside through the filling layer (130) and the heat dissipation structure (140).

[0062] The heat dissipation structure (140) can dissipate heat generated from the gain medium (110). For example, the heat dissipation structure (140) can be made of copper.

[0063] FIG. 3 is a cross-sectional view for explaining the operation of an optical amplifier (100) according to one embodiment of the present disclosure.

[0064] Referring to FIG. 3, the gain medium (110) may include a first surface (31), a second surface (32) which is the opposite surface of the first surface (31), and a side surface (33). In FIG. 3, it should be noted that the filling layer (130) is omitted for convenience in explaining the amplification process of the seed beam (10). In addition, although the pump beam (20) is illustrated as only one light ray, this is for convenience of explanation, and multiple light rays constituting the pump beam (20) are incident on the gain medium (110) and propagate, and this also applies below.

[0065] The gain medium (110) can receive the seed beam (10) and the pump beam (20) through the first surface (31). Since the gain medium (110) has a refractive index greater than that of the metal layer (120), the seed beam (10) and the pump beam (20) can repeat total reflection at the boundary surface (i.e., the side surface (33)) of the gain medium (110) and the metal layer (120) and propagate in the longitudinal direction (i.e., the -x-axis direction) of the gain medium (110). The pump beam (20) can be absorbed by rare-earth metal ions included in the gain medium (110) while propagating inside the gain medium (110) and excite the rare-earth metal ions. Accordingly, the seed beam (10) can be amplified.

[0066] Meanwhile, unnecessary pump beams may exist within the gain medium (110). Unnecessary pump beams may include pump beams having unintended incident directions and properties, or pump beams incident from the outside. For example, a pump beam having unintended properties and directions that do not help the seed beam (10) to be amplified in a predetermined direction and properties may adversely affect the characteristics of the seed beam (10). In addition, some of the pump beams (20) may return in the opposite direction to the propagation direction (i.e., the +x-axis direction). The returned pump beams may become pump beams having undesirable properties and directions in the preceding stages of the multi-stage amplifier module, and may adversely affect the characteristics of the amplified signal of the preceding amplifier module. Therefore, it is necessary to emit unnecessary pump beams outside the gain medium (110).

[0067] FIG. 4 is a drawing showing a cross-section of an optical amplifier (100) according to one embodiment of the present disclosure.

[0068] Referring to Fig. 4, a pump beam (20) can be incident on the first surface (31) of the gain medium (110). The pump beam (20) can proceed in the -x-axis direction while repeating total reflection within the gain medium (110).

[0069] The gain medium (110) may include a pump beam removal region (A1). The pump beam removal region (A1) may be a region for emitting at least a portion of the pump beam (20) remaining inside the gain medium (110) to the outside of the gain medium (110). The pump beam removal region (A1) may be provided on a side of the gain medium (110) adjacent to the first surface (31). The surface of the gain medium (110) in the pump beam removal region (A1) may be surface-treated to be uneven. For example, the surface treatment may include at least one of sanding, etching, or line processing.

[0070] Specifically, when viewed in the horizontal direction (i.e., y-axis direction) perpendicular to the longitudinal direction (i.e., x-axis direction) of the gain medium, the depth of the surface of the gain medium (110) in the vertical direction (i.e., z-axis direction) may be non-uniform. For example, when viewed in the horizontal direction, the surface of the gain medium (110) in the pump beam removal region (A1) may have a zigzag pattern. The zigzag pattern may have an irregular shape or a regular shape. In addition, the edge portion of the zigzag pattern may have a sharp shape or a smooth shape.

[0071] At least a portion of the pump beam (20) inside the gain medium (110) may be emitted to the outside of the gain medium (110) through the pump beam removal region (A1). For example, if the first pump beam (P1) encounters the pump beam removal region (A1) at an angle smaller than the critical angle, the first pump beam (P1) may transmit through the pump beam removal region (A1). The first pump beam (P1) may be the unnecessary pump beam described above, for example, a backward signal. The transmitted first pump beam (P1) may be absorbed by the metal layer (120), converted into heat energy, and then emitted to the outside. Since the gain medium (110) of the pump beam removal region (A1) has an uneven surface, the probability that the first pump beam (P1) encounters the side surface of the gain medium (110) at an angle smaller than the critical angle may increase.

[0072] The pump beam removal region (A1) may be located between the first surface (31) and the region (41) on the side surface of the gain medium (110) where the pump beam (20) is first reflected. When the part closest to the first surface (31) is referred to as the beginning of the pump beam removal region (A1) and the part farthest from the first surface (31) is referred to as the end of the pump beam removal region (A1), the end of the pump beam removal region (A1) may be located closer to the first surface (31) than the region (41). When the end of the pump beam removal region (A1) is located farther from the first surface (31) than the region (41), a significant portion of the pump beam (20) may be removed through the pump beam removal region (A1) during the initial pumping process, and in this case, the seed beam (10) may not be amplified as intended.

[0073] The metal layer (120) may have two surfaces of different shapes. The metal layer (120) may include a first surface in contact with the gain medium (110) (i.e., an interface with the gain medium (110)) and a second surface opposite the first surface (i.e., an interface with the filling layer (130)). For example, the second surface may have the same shape regardless of the X-axis position. Specifically, the second surface may have a flat shape.

[0074] On the other hand, the first surface of the metal layer (120) may have different shapes depending on the X-axis position. For example, the side region of the gain medium (110) may be divided into a first region having a pump beam removal region (A1) and a second region, which is the remaining region. The first surface may be uneven in the first region and flat in the second region.

[0075] FIG. 5 is a drawing showing a cross-section of an optical amplifier (100) according to another embodiment of the present disclosure.

[0076] Referring to Fig. 5, a pump beam (20) can be incident on the first surface (31) of the gain medium (110). The pump beam (20) can proceed in the -x-axis direction while repeating total reflection within the gain medium (110).

[0077] The gain medium (110) may include a pump beam removal region (A2). The pump beam removal region (A2) may be a region for emitting at least a portion of the pump beam (20) remaining inside the gain medium (110) outside the gain medium (110). The pump beam removal region (A2) may be provided on a side of the gain medium (110) adjacent to the second surface (32). The surface of the gain medium (110) in the pump beam removal region (A2) may be surface-treated (e.g., sanded) to be uneven.

[0078] At least a portion of the pump beam (20) inside the gain medium (110) may be emitted outside the gain medium (110) through the pump beam removal region (A2). For example, when the second pump beam (P2) encounters the pump beam removal region (A2) at an angle smaller than the critical angle, the second pump beam (P2) may transmit through the pump beam removal region (A2) and be absorbed into the metal layer (120). The second pump beam (P2) may be the unnecessary pump beam described above, for example, a backward signal. Since the gain medium (110) of the pump beam removal region (A2) has an uneven surface, the probability that the second pump beam (P2) encounters the side surface of the gain medium (110) at an angle smaller than the critical angle may increase. As the second pump beam (P2) is removed, no more pump beam (20) than necessary remains inside the gain medium (110), and thus, the characteristics of the seed beam (10) can be prevented from being deteriorated by the second pump beam (P2).

[0079] The pump beam removal region (A2) may be located in an area adjacent to the second surface (32). In an area corresponding to the pump beam removal region (A2), the metal layer (120) may have an uneven surface. For example, the metal layer (120) may have an uneven surface along the surface of the gain medium (110). In an area not corresponding to the pump beam removal region (A2), the metal layer (120) may have a uniform (or flat) surface. In an area corresponding to the pump beam removal region (A2), the filling layer (130) may have an uneven surface. For example, the filling layer (130) may have an uneven surface along the surface of the gain medium (110). In an area not corresponding to the pump beam removal region (A2), the filling layer (130) may have a uniform (or flat) surface.

[0080] Meanwhile, the pump beam removal area (A2) may be larger than the pump beam removal area (A1) of FIG. 4. The x-axis direction length of the pump beam removal area (A2) may be larger than the x-axis direction length of the pump beam removal area (A1). This is because the seed beam (10) that has advanced to the pump beam removal area (A2) has already been amplified to a sufficient size, so there is no longer a need to prevent contact between the pump beam (20) and the pump beam removal area (A2).

[0081] In another embodiment, the gain medium (110) may include both the pump beam removal region (A1) of FIG. 4 and the pump beam removal region (A2) of FIG. 5. Furthermore, in the present disclosure, either of the two regions (A1, A2) is referred to as an additional pump beam removal region.

[0082] In another embodiment, the metal layer (120) may not be present in at least some of the pump beam removal regions (A1, A2). For example, the metal layer (120) may not be present in the pump beam removal region (A1). In this case, the metal layer (120) may be present only in the remaining region of the side surface of the gain medium (110) excluding the pump beam removal region (A1). Since the metal layer (120) can reflect the pump beam back into the gain medium (110), when the metal layer (120) is absent, the pump beam escaping outside the gain medium (110) may increase. In other words, the amount of pump beam removal in the pump beam removal region (A1) may increase.

[0083] As described above, the amplification efficiency, safety, and laser quality of the optical amplifier (100) can be improved by removing unnecessary pump beams through the pump beam removal region (A1). In addition, the backward signal entering the gain material can be attenuated by using the pump beam removal region (A1).

[0084] FIG. 6 is a drawing showing a cross-section of an optical amplifier (100) according to one embodiment of the present disclosure.

[0085] Referring to Fig. 6, the emission surface of the gain medium (110), i.e., the second surface (32), may have an inclined shape. For example, the second surface (32) may be inclined by a preset first angle (61) with respect to the z-axis. That is, the second surface (32) may have a wedge shape. The preset first angle (61) may be 5 degrees.

[0086] If the second surface (32) has a wedge shape, the backward signal of the pump beam (20) may be reduced compared to when the second surface (32) is parallel to the z-axis. That is, the amount of the pump beam (20) directed toward the first surface (31) may be reduced as it is reflected within the gain medium (110). As described above, the backward signal may have a negative effect on the quality of the laser beam. Since the second surface (32) has a wedge shape, the backward signal may be reduced, and as a result, the quality of the laser beam may be improved.

[0087] [Table 1] is experimental data showing the backward signal reduction effect of the wedge shape.

[0088] Ppump (W)Pbackward (mW)NormalWedgedNormalWedgedw / o input signalw / o input signalw / 5mW input signalw / 5mW input signal216222119595260292439714630437296421913474432882204

[0089] Specifically, the intensity of the backward signal of the pump beam (20) was measured while adjusting the intensity of the pump beam (20) for each case where the input signal (i.e., the seed beam (10)) was input to the gain medium (110) and when it was not input. Ppump represents the intensity of the pump beam (20), and Pbackward represents the intensity of the backward signal. The input signal means the seed beam (10). The intensity of the backward signal was measured when the gain medium (110) had a general shape and a wedge shape, respectively. Here, the general shape means that it is not a wedge shape, and for example, there may be a shape in which the incident surface and the exit surface are horizontal.

[0090] Referring to Table 1, it can be seen that in each case, the wedge shape has a lower intensity of the backward signal compared to the general shape (i.e., a shape in which the incident and exit surfaces are horizontal). In this way, if the intensity of the backward signal is reduced, the amplification efficiency, safety, and laser quality of the optical amplifier (100) can be improved.

[0091] Meanwhile, the second surface (S2) of the heat dissipation structure (140) may be positioned on the same plane as the second surface (32) of the gain medium (110). Accordingly, the second surface (S2) of the heat dissipation structure (140) may also have a wedge shape inclined by a preset first angle (61) with respect to the z-axis. However, this is only one embodiment, and it is also possible that the second surface (S2) of the heat dissipation structure (140) is not positioned on the same plane as the second surface (32) of the gain medium (110).

[0092] FIG. 7 is a drawing showing a cross-section of an optical amplifier (100) according to another embodiment of the present disclosure.

[0093] Referring to Fig. 7, the incident surface of the gain medium (110), i.e., the first surface (31), may have an inclined shape. For example, the first surface (31) may be inclined by a preset second angle (71) with respect to the y-axis. That is, the first surface (31) may have a wedge shape. The preset second angle (71) may be 5 degrees.

[0094] When the second surface (32) has a wedge shape inclined with respect to the z-axis as shown in Fig. 6, aberration (e.g., astigmatism) of the output beam in the z-axis direction may occur. In this case, when the first surface (31) has a wedge shape inclined with respect to an axis perpendicular to the z-axis (e.g., the y-axis), aberration of the output beam may be improved.

[0095] According to various embodiments, the first side (31) of the gain medium (110) may have a wedge shape, the second side (32) may have a wedge shape, or both the first side (31) and the second side (32) may have a wedge shape.

[0096] Meanwhile, the first surface (S1) of the heat dissipation structure (140) may be positioned on the same plane as the first surface (31) of the gain medium (110). Accordingly, the first surface (S1) of the heat dissipation structure (140) may also have a wedge shape inclined by a preset second angle (71) with respect to the y-axis. However, this is only one embodiment, and it is also possible that the first surface (S1) of the heat dissipation structure (140) is not positioned on the same plane as the first surface (31) of the gain medium (110).

[0097] In FIGS. 4 and 5, a method for removing unnecessary pump beams by using surface treatment of the side surface of the gain medium (110) is described. In addition, in FIGS. 6 and 7, a method for reducing unnecessary pump beams (particularly, backward signals) by using the structure of the incident or exit surface of the gain medium (110) is described. Depending on the embodiment, the surface treatment of the side surface of the gain medium (110) and the structure of the incident or exit surface may be applied selectively or together.

[0098] FIG. 8 is a block diagram conceptually illustrating a laser processing device according to one embodiment of the present disclosure.

[0099] Referring to FIG. 8, a laser processing device (1000) may include an optical amplifier (100) and a laser generator (200). The optical amplifier (100) may include a gain medium (110) and a pumping source that provides a pump beam to the gain medium (110).

[0100] The pumping source can provide the pump beam to the first surface (31) and / or the second surface (32) of the gain medium (110). For example, the pumping source can provide the pump beam to the first surface (31) of the gain medium (110). The pump beam incident on the gain medium (110) can cause density inversion within the gain medium (110). Amplification of the seed beam can occur as the seed beam passes through the gain medium (110) where density inversion has occurred.

[0101] A laser generator (200) can generate a seed beam (or signal beam). The laser generator (200) can transmit the seed beam to an optical amplifier (100). The seed beam may be a pulsed laser beam.

[0102] According to one embodiment of the present disclosure, a laser processing device including an optical amplifier (100) may be provided. The laser processing device may include a laser generator and a pump beam light source. The laser generator may output a seed beam (or signal beam) provided to the optical amplifier (100). For example, the laser generator may be a picosecond or femtosecond seed laser light source.

[0103] A pump beam light source can output a pump beam provided to an optical amplifier (100). The pump beam can be incident on the first surface (31) or the second surface (32) of the optical amplifier (100). Alternatively, the pump beam can be incident on each of the first surface (31) and the second surface (32) of the optical amplifier (100).

[0104] Although the preferred embodiments of the present disclosure have been illustrated and described above, the present disclosure is not limited to the specific embodiments described above, and various modifications may be made by a person skilled in the art to which the present disclosure pertains without departing from the gist of the present disclosure as claimed in the claims, and such modifications should not be understood individually from the technical idea or prospect of the present disclosure.

Claims

1. A gain medium having a first surface onto which a seed beam is incident, a second surface located opposite the first surface, and a side surface connecting the first surface and the second surface, and in which the incident seed beam is amplified while moving to the second surface and is emitted to the second surface; and A pumping source that provides a pump beam to at least one of the first surface or the second surface; In one area of ​​the above side of the above gain medium, A pump beam removal region is provided whose surface is treated so that at least a portion of the pump beam existing inside the gain medium is emitted to the outside of the gain medium, The above pump beam removal area is, characterized in that the pump beam is located closer to the first surface than the area where it is first reflected from the side surface of the gain medium. Optical amplifier.

2. In paragraph 1, The above surface treatment includes at least one of sanding, etching or line processing, In the above pump beam removal region, the gain medium has a non-flat surface with an uneven depth. Optical amplifier.

3. In paragraph 1, The above gain medium is, Further comprising an additional pump beam removal region located on the side adjacent to the second surface, The length of the additional pump beam removal region is characterized in that the length of the above pump beam removal area is greater than that of the above pump beam removal area. Optical amplifier.

4. In paragraph 2, further comprising a metal layer surrounding the side surface of the gain medium; The above metal layer is, comprising a first surface in contact with the gain medium and a second surface opposite to the first surface, The above first surface is, In the first region corresponding to the pump beam removal region, the gain medium is non-flat along the contour of the non-flat surface, In the second region that does not correspond to the above pump beam removal region, it is flat, The above second surface is, characterized by being flat in the first region and the second region Optical amplifier.

5. In paragraph 4, The above pump beam is, Based on the difference in refractive index between the gain medium and the metal layer, the light is emitted to the outside of the gain medium. Optical amplifier.

6. In paragraph 2, a heat dissipation structure surrounding at least a portion of the side surface of the gain medium; and Further comprising a filling layer provided between the above gain medium and the heat dissipation structure; The above filling layer is, characterized by having a flat surface Optical amplifier.

7. In paragraph 1, The above second side, It is characterized by having a shape inclined at a first angle set based on the first axis. Optical amplifier.

8. In paragraph 7, The above first side, It is characterized by having a shape inclined at a preset second angle based on a second axis perpendicular to the first axis. Optical amplifier.

9. In paragraph 8, The above-described first angle and the above-described second angle are characterized in that they are the same. Optical amplifier.

10. In paragraph 1, The above gain medium is, Containing YAG crystals added to rare earth metals Optical amplifier.

11. A laser generator that generates a seed beam; and An optical amplifier that amplifies a seed beam generated from the laser generator; The above optical amplifier, A gain medium having a first surface on which a seed beam is incident, a second surface located opposite the first surface, and a side connecting the first surface and the second surface, and in which the incident seed beam is amplified while moving to the second surface and is emitted to the second surface, and A pumping source that provides a pump beam to at least one of the first surface or the second surface, In one area of ​​the above side of the above gain medium, A pump beam removal region is provided whose surface is treated so that at least a portion of the pump beam existing inside the gain medium is emitted to the outside of the gain medium, The above pump beam removal area is, characterized in that the pump beam is located closer to the first surface than the area where it is first reflected from the side surface of the gain medium. Laser processing device.

12. In paragraph 11, The above surface treatment includes at least one of sanding, etching or line processing, In the above pump beam removal region, the gain medium has a non-flat surface with an uneven depth. Laser processing device.

13. In paragraph 11, The above gain medium is, Further comprising an additional pump beam removal region located on the side adjacent to the second surface, The length of the additional pump beam removal region is characterized in that the length of the above pump beam removal area is greater than that of the above pump beam removal area. Laser processing device.

14. In paragraph 11, The above second side, It is characterized by having a shape inclined at a first angle set based on the first axis. Laser processing device.

15. In paragraph 14, The above first side, It is characterized by having a shape inclined at a preset second angle based on a second axis perpendicular to the first axis. Laser processing device.

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