Optical unit, laser oscillator with the same, and laser processing device

Abstract

To provide an optical unit which is used inside of a laser oscillator of an external resonance type and capable of suppressing an output loss during external oscillation.SOLUTION: An optical unit 60 comprises a FAC lens array 63 and a beam twister array 64. A second surface 63b of the FAC lens array 63 includes a curvature part. A first surface 63a of the FAC lens array 63 and third and fourth surfaces 64a and 64b of the beam twister array 64 are flat surfaces. A first antireflection layer AR1 of a first reflection factor is provided on the flat surface, and a second antireflection layer AR2 of a second reflection factor is provided on the second surface 63b. The first and second reflection factors are lower than a predetermined reflection factor, and the second reflection factor is higher than the first reflection factor. A fluctuation rate of the reflection factor with respect to film thickness fluctuation of the second antireflection layer AR2 is smaller than that of the first antireflection layer AR1.SELECTED DRAWING: Figure 7B

Description

[Technical field]

[0001] The present disclosure relates to an optical unit, and a laser oscillator and a laser processing apparatus equipped with the optical unit. [Background technology]

[0002] In recent years, expectations for laser processing have been rising for various materials such as copper, gold, and resin. For example, in the automobile industry, motorization, miniaturization, high rigidity, improved design freedom, and improved productivity are required, and expectations for laser processing are high. To achieve highly productive processing, a laser light source that can generate a highly efficient and high-power laser light is required. A semiconductor laser element is known as a laser light source suitable for this requirement. In particular, to increase the output of laser light, a laser module equipped with a laser diode bar having a plurality of emitters that emit laser light is useful.

[0003] When using a laser diode bar, it is necessary to combine the laser beams emitted from the multiple emitters into a single laser beam. Before such combining, the shape of each laser beam may be appropriately shaped.

[0004] In view of this, a configuration has been proposed in the past in which one or more types of optical components are disposed in the vicinity of the laser light emission end face of a laser diode bar to shape the laser light (see, for example, Patent Documents 1 to 4).

[0005] In addition, Patent Document 4 proposes a configuration in which the laser beams emitted from the multiple emitters of a laser diode bar are shaped by optical components and then combined into one combined laser beam, and an external resonator is formed between an external resonator mirror and the rear end face of the emitter, thereby making it possible to obtain a high-power combined laser beam. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-061591 A [Patent Document 2] International Publication No. 2018 / 037663 [Patent Document 3] JP 2021-132151 A [Patent Document 4] Patent No. 5832455 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when an external resonance type laser oscillator as disclosed in Patent Document 4 was constructed, the output of the coupled laser light was sometimes significantly lower than the design value. The inventors of the present application analyzed the cause and found that the optical components were damaged. As a result of further analysis, it was found that a part of the laser light was reflected on the surface of the optical components arranged in the optical path of the laser light in the laser oscillator, inhibiting external resonance and causing loss.

[0008] The present disclosure has been made in consideration of these points, and its purpose is to provide an optical unit for use inside an external resonance type laser oscillator that is capable of suppressing output loss during external oscillation, and a laser oscillator and laser processing apparatus equipped with the same. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, an optical unit according to the present disclosure is an optical unit used inside an external resonator type laser oscillator, and has at least two optical components through which a first laser light emitted from the laser oscillator passes, and at least one of the transmission surfaces of the first laser light in the plurality of optical components has a predetermined or greater unevenness and has a curvature portion that collimates the first laser light, and a first anti-reflection layer is provided on a flat portion of the plurality of transmission surfaces, the reflectance of the first anti-reflection layer in the wavelength range of the first laser light is a first reflectance, and a second anti-reflection layer is provided on the curvature portion, the reflectance of the second anti-reflection layer in the wavelength range of the first laser light is a second reflectance, and the first reflectance and the second reflectance are each lower than a predetermined reflectance, and the second reflectance is higher than the first reflectance.

[0010] The laser oscillator according to the present disclosure comprises at least a semiconductor laser element having a plurality of emitters, the optical unit, and an external resonator mirror provided with a first reflective layer, the semiconductor laser element being a laser diode bar having a plurality of the emitters, or a plurality of laser diodes having a single emitter, and further comprises an optical coupling element disposed between the optical unit and the external resonator mirror, which combines a plurality of second laser beams emitted respectively from the plurality of emitters and transmitted through the optical unit to convert them into the first laser beam, and the external resonator mirror reflects the first laser beam combined by the optical coupling element via the optical coupling element toward the second reflective layer, and the first laser beam is emitted through the external resonator mirror.

[0011] The laser processing device according to the present disclosure is characterized by including at least the laser oscillator and a laser head that receives the first laser light and irradiates it toward a workpiece. Effect of the Invention

[0012] According to the optical unit of the present disclosure, it is possible to suppress the output loss during external oscillation. According to the laser oscillator of the present disclosure, it is possible to obtain a high-output first laser light by suppressing the output loss during external oscillation. According to the laser processing device of the present disclosure, it is possible to irradiate a high-output laser light onto a workpiece to perform laser processing on the workpiece. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of a laser processing device according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram illustrating the internal configuration of a laser oscillator. [Diagram 3] FIG. 2 is a perspective view of a laser diode bar. [Figure 4] FIG. 1 is a schematic diagram for explaining the principle of wavelength synthesis. [Diagram 5] FIG. 2 is a schematic diagram of a laser module. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7A] FIG. 2 is a perspective view of an FAC lens array. [Figure 7B] FIG. 7B is a cross-sectional view taken along line VIIB-VIIB in FIG. 7A. [Figure 8] FIG. 2 is a plan view of a beam twister array. [Figure 9] FIG. 2 is a schematic diagram of an external resonator at the time of design. [Figure 10A] 4 illustrates a wavelength spectrum of a first laser light in an ideal state. [Figure 10B] FIG. 4 is a diagram showing the drive current dependency of the output of a first laser light in an ideal state. [Figure 11A] 13 shows a wavelength spectrum of a first laser light when the reflectance of the first end face coating layer is set to 1%. [Figure 11B] FIG. 13 is a diagram showing the drive current dependency of the output of the first laser light when the reflectance of the first end face coating layer is set to 2%. [Figure 12A] 13 shows a wavelength spectrum of a first laser light when the reflectance of the first end face coating layer is set to 2%. [Figure 12B]FIG. 13 is a diagram showing the drive current dependency of the output of the first laser light when the reflectance of the first end face coating layer is set to 2%. [Figure 13] FIG. 1 is a schematic diagram of an actual external resonator. [Figure 14] FIG. 13 is a schematic diagram for explaining a curvature portion angle. [Figure 15] FIG. 13 is a diagram showing the dependence of the variation rate from the flat portion film thickness on the curvature portion angle. [Figure 16] FIG. 13 is a diagram showing the wavelength dependence of the reflectance of the first antireflection layer when the film thickness is changed. [Figure 17] FIG. 4 is a graph showing the wavelength dependence of the reflectance of a first antireflection layer and a second antireflection layer. [Figure 18] FIG. 13 is a schematic cross-sectional view of another FAC lens array. [Figure 19] FIG. 4 is a diagram showing the output of a first laser beam in an example and a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present disclosure, its application, or its uses.

[0015] (Embodiment) [Laser processing equipment configuration] FIG. 1 is a schematic configuration diagram of a laser processing device according to the present embodiment.

[0016] In FIG. 1, a plurality of components are arranged inside each of the laser oscillator 100, the beam combiner 200, the focusing optical unit 300, and the laser head 800, but illustration and description of these components are omitted.

[0017] In this specification, "orthogonal" or "parallel" means that the two objects are orthogonal or parallel, including the assembly tolerances and processing tolerances of the laser processing apparatus 1000 and its components, and does not mean that the objects being compared are orthogonal or parallel in the strict sense.

[0018] 1, the laser processing apparatus 1000 includes a plurality of laser oscillators 100, a beam combiner 200, a focusing optical unit 300, a housing 400, a control unit 500, a power supply 600, an optical fiber 700, and a laser head 800. Of these components, the plurality of laser oscillators 100, the beam combiner 200, the focusing optical unit 300, and a portion of the optical fiber 700 are housed inside the housing 400.

[0019] The laser oscillator 100 emits a first laser beam LB M The configuration of the laser oscillator 100 will be described later.

[0020] The beam combiner 200 combines the first laser beams LB emitted from the multiple laser oscillators 100. M These are combined into one laser beam LB (hereinafter, sometimes referred to as a combined laser beam (third laser beam) LB) and made to enter the light collecting optical unit 300. Specifically, each of the first laser beams LB M The optical axes of the two lenses are brought close to each other or are aligned, and the lenses are coupled so that their optical axes are parallel to each other.

[0021] The focusing optical unit 300 has a focusing lens (not shown). The combined laser light LB enters the focusing optical unit 300 from the beam combiner 200, is focused by the focusing lens, and enters the optical fiber 700.

[0022] The control unit 500 has one or more central processing units (CPUs) and semiconductor memories such as random access memories (RAMs) and read only memories (ROMs). The control unit 500 may further have hard disk drives (HDDs) and solid state drives (SSDs).

[0023] The control unit 500 controls the laser oscillation of each laser oscillator 100 by supplying control signals such as output voltage and on-time to the power source 600. It is also possible to control the laser oscillation of each laser oscillator 100 individually. For example, the laser oscillation output and on-time may be different for each laser oscillator 100. The control unit 500 may also control the operation of a robot (not shown) to which the laser head 800 is attached.

[0024] As described above, the power supply 600 supplies power for performing laser oscillation to each of the multiple laser oscillators 100. In response to a command from the control unit 500, the power supplied to each laser oscillator 100 may be made different.

[0025] The optical fiber 700 guides the coupled laser light LB incident from the focusing optical unit 300 to the laser head 800. The optical fiber 700 has one or more cores (not shown) which are optical waveguides, and a cladding (not shown) which is an optical confinement layer provided so as to surround the core.

[0026] The laser head 800 irradiates the combined laser light LB guided by the optical fiber 700 toward the outside. For example, in the laser processing apparatus 1000 shown in Fig. 1, the combined laser light LB is emitted toward a workpiece W, which is an object to be processed and is placed on a stage 900. In this manner, the workpiece W is laser processed.

[0027] According to the laser processing apparatus 1000 shown in FIG. 1, a high-power combined laser light LB having an output exceeding several kW can be obtained. This allows the workpiece W to be laser-processed at high speed. In addition, high-quality laser processing can be performed. In this embodiment, four laser oscillators 100 are mounted on the laser processing apparatus 1000, but this is not particularly limited. The number of laser oscillators 100 mounted can be appropriately changed depending on the output specifications required for the laser processing apparatus 1000 and the output specifications of each laser oscillator 100.

[0028] [Laser oscillator configuration] Fig. 2 is a schematic diagram of a laser oscillator according to an embodiment, Fig. 3 is a perspective view of a laser diode bar, and Fig. 4 is a schematic diagram for explaining the principle of wavelength synthesis.

[0029] In the following description, the second laser light LB emitted from each of the multiple emitters 11 provided in the laser diode bar 10 is E The direction in which the second laser light LB travels may be referred to as the X direction, and the direction in which the emitters 11 are arranged may be referred to as the Y direction. Also, a direction perpendicular to the X direction and the Y direction may be referred to as the Z direction. E The Y direction corresponds to the fast axis direction, and the Y direction corresponds to the slow axis direction. The fast axis and the slow axis will be explained later.

[0030] The Z direction is also the stacking direction of the laser diode bar 10 and the submount 20 (see FIG. 5). In the Z direction, the side on which the laser diode bar 10 is provided may be referred to as the top, upper side, or upper side. The side on which the submount 20 is provided may be referred to as the bottom, lower side, or lower side.

[0031] In addition, in the X direction, the side of the laser diode bar 10 on which the first end face coating layer 12 is provided may be referred to as the front or front side. The side on which the second end face coating layer (second reflective layer) 13 is provided may be referred to as the rear or rear side.

[0032] As shown in Fig. 2, the laser oscillator 100 has a plurality of laser modules 70, a diffraction grating DG, and an external resonator mirror OC, which are arranged inside a housing 80 while maintaining a predetermined positional relationship with each other. The laser module 70 has a laser diode bar 10 (see Fig. 5). The external resonator mirror OC is provided in the housing 80, covering a light exit window 81 provided in the housing 80. The external resonator mirror OC may be provided inside the housing 80, between the diffraction grating DG and the light exit window 81.

[0033] The laser oscillator 100 includes a number of components other than those mentioned above, such as a second laser beam LB E A mirror that directs the second laser beam LB to the diffraction grating DG. E In addition, the laser modules 70 are different in number from the actual laser modules 70.

[0034] As shown in Fig. 3, the laser diode bar 10 has emitters 11 arranged at intervals from each other along the Y direction. The front end face of the laser diode bar 10 is covered with a first end face coating layer 12. The rear end face of the laser diode bar 10 is covered with a second end face coating layer 13. The first end face coating layer 12 is a layer that is formed by applying a second laser light LB E and the first laser light LB M The second end face coating layer 13 is adjusted to have a reflectance of 0.0 several percent or less for light in the wavelength range of the second laser light LB E and the first laser light LB M When the emitter 11 oscillates, the first end face coating layer 12 emits a second laser beam LB E is emitted forward.

[0035] 3, the shape of the laser diode bar 10 is illustrated in a simplified manner and differs from the actual one. Also, the number of emitters 11 included in the laser diode bar 10 differs from the actual one.

[0036] As shown in FIG. 3, the second laser light LB emitted from each emitter 11 of the laser diode bar 10 is E At a location more than a certain distance away from the laser diode bar 10, a cross section cut by a virtual plane perpendicular to the optical axis (also called a far field pattern (FFP)) is elliptical. The long axis direction (long diameter direction) of this ellipse is called the fast axis direction. Note that the fast axis and the second laser beam LB E The direction perpendicular to the optical axis of each of the laser diode bar 70 and the optical axis of each of the laser diode bar 70 is called the slow axis direction (the short axis direction (minor diameter direction) which is the short side direction of the ellipse). The fast axis is an axis perpendicular to the pn junction (not shown) formed in the laser diode bar 10, and the slow axis is an axis parallel to the pn junction. The configuration of the laser module 70 will be described later.

[0037] As shown in FIG. 2, in one laser module 70, second laser light LB emitted from a plurality of emitters 11 is E The beams travel toward the diffraction grating DG after their expansion in the fast axis direction and the slow axis direction is collimated and their rotation direction is changed.

[0038] The diffraction grating DG is a multi-beam second laser beam LB E and emits the second laser beam LB E In this embodiment, the diffraction grating DG diffracts the second laser beam LB E The diffraction grating DG transmits the second laser beam LB E Alternatively, the light source 10 may be of a type that reflects each of the light sources 10 and 11.

[0039] At that time, the diffraction grating DG is irradiated with the second laser light LB EThe optical axes of the second laser beams LB are close to each other and parallel to each other. E are diffracted, respectively.

[0040] The external cavity mirror OC reflects the incident second laser light LB E In each of the laser diode bars 10, a part of the light is transmitted and the remaining part is reflected toward the diffraction grating DG. In this manner, an external cavity is formed between the external cavity mirror OC and each of the laser diode bars 10. This will be further described.

[0041] As shown in FIG. 4, the second laser light LB emitted from the laser diode bar 10 E Each of the first laser beams LB is diffracted by the diffraction grating DG and then enters the external cavity mirror OC. E A part of the reflected light passes through the first end face coating layer 12 provided on the light emission surface (hereinafter sometimes referred to as the front end face) of the laser diode bar 10, and reaches a second end face coating layer (second reflective layer; see FIG. 6) 13 provided on the rear end face opposite to the front end face. Furthermore, the second laser light LB E is reflected by the second end face coating layer 13 and emitted again to the outside of the laser diode bar 10 from the first end face coating layer 12.

[0042] A second laser beam LB emitted from each emitter 11 of the laser diode bar 10 E Among these, only light having a wavelength (hereinafter referred to as a lock wavelength) that satisfies the diffraction condition of the diffraction grating DG and is reflected by the external cavity mirror OC is fed back to the original emitter 11, whereby an external cavity is formed between the second end face coating layer 13 of the laser diode bar 10 and a first reflective layer R1 (see FIGS. 9 and 13) provided on the external cavity mirror OC, and a second laser light LB is emitted from the laser diode bar 10, specifically, from each of the multiple emitters 11. E will be output.

[0043] The lock wavelength of each emitter 11 is λ L , the period of the diffraction grating DG is d, the incident angle is α, the exit angle is β, and the order is m, then the lock wavelength λ L is expressed by equation (1).

[0044] d(sinα+sinβ)=mλ L ...(1) Generally, the order of the diffraction grating DG is m=1.

[0045] For example, in the laser diode bar 10, the emitters 11 are formed so that the incident angle α with respect to the incident surface of the diffraction grating DG changes for each arrangement position of the emitters 11. In this case, the lock wavelength of the emitters 11 formed in the laser diode bar 10 changes stepwise from one end of the laser diode bar 10 to the other end.

[0046] Each emitter 11 can oscillate by external resonance only when the inherent gain wavelength intensity of the laser diode bar 10 is equal to or greater than a predetermined value. g Therefore, the laser oscillator 100 of this embodiment oscillates at a lock wavelength within a predetermined range, and does not oscillate at a lock wavelength outside the predetermined range. g The upper and lower limit ranges are the lock wavelengths λ of the emitters 11 at both ends of the laser diode bar 10. L Difference Δλ L_bar The optical design of the laser diode bar 10 and each emitter 11 is performed so that the lock wavelength λ of the emitters 11 at both ends falls within the range. L Difference Δλ L_bar varies with the distance between the laser diode bar 10 and the diffraction grating DG.

[0047] The second laser light LB emitted from each emitter 11 of the laser diode bar 10 E The positional relationship between the laser diode bar 10 and the diffraction grating DG is defined so that the optical axes of the laser diode bars 10 and the diffraction grating DG overlap each other when they pass through the diffraction grating DG.

[0048] That is, the second laser light LB emitted from each of the multiple emitters 11 provided on the multiple laser diode bars 10 E The second laser beams LB are overlapped with each other when they are incident on the external cavity mirror OC. E The overlapping and combining of the second laser beams LB emitted from the respective emitters 11 provided on the laser diode bars 10 is called wavelength synthesis. E The first laser beam LB M The resulting light is wavelength-combined and emitted to the outside of the laser oscillator 100.

[0049] [Laser module configuration] Fig. 5 is a schematic diagram of a laser module according to embodiment 1. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 5. Fig. 7A is a perspective view of an FAC lens array. Fig. 7B is a cross-sectional view taken along line VIIB-VIIB in Fig. 7A. Fig. 8 is a plan view of a beam twister array.

[0050] 5 shows a side view of the laser module 70. For convenience of explanation, the internal structure of the microchannel cooler 40 (hereinafter, referred to as MCC 40) is not shown in FIG.

[0051] 5 and 6, the laser module 70 includes a laser diode bar 10, a submount 20, a first electrode block 31, a second electrode block 32, a microchannel cooler 40 (hereinafter referred to as MCC 40), and a base 50. The laser module 70 also includes an optical unit 60.

[0052] The submount 20 is a plate-shaped conductive member, and is bonded to the upper surface of the extension portion 32a of the second electrode block 32 by a conductive adhesive (not shown) such as Au-Sn solder. The material of the submount 20 is made of a composite material of diamond and metal, or a conductive semiconductor material such as SiC, and it is preferable that the linear expansion coefficient is close to that of the semiconductor material constituting the laser diode bar 10 and that the Young's modulus is high.

[0053] The first electrode block 31 is disposed behind the laser diode bar 10 and the submount 20 at a distance from them along the X direction. As shown in Fig. 6, the first electrode block 31 is disposed on the upper surface of the extension portion 32a of the second electrode block 32 via an insulating sheet 33. The first electrode block 31 is connected to the laser diode bar 10 by a plurality of metal wires MW.

[0054] The second electrode block 32 is disposed behind the first electrode block 31 with a gap therebetween along the X direction. As described above, the second electrode block 32 is insulated from the first electrode block 31 via the insulating sheet 33. Meanwhile, the extension portion 32a of the second electrode block 32 and the submount 20 are electrically connected to the laser diode bar 10 via a conductive adhesive material (not shown). When a voltage of a predetermined value or more is applied between the first electrode block 31 and the second electrode block 32 from an external power source (not shown), each of the multiple emitters 11 oscillates, and a second laser light LB is emitted. E is emitted forward.

[0055] The MCC 40 is a plate-shaped member having a cooling water channel (not shown) inside. When cooling water is supplied to the MCC 40 from a cooling water supply mechanism (not shown), the cooling water circulates inside the cooling water channel. At this time, the submount 20 and the laser diode bar 10 above the cooling water channel are cooled, and the temperature of the laser diode bar 10 during operation is maintained within an appropriate range.

[0056] Moreover, the MCC 40 supports the first electrode block 31 and the second electrode block 32. Moreover, the MCC 40 supports the submount 20 and the laser diode bar 10 mounted on the extension portion 32a of the second electrode block 32. The MCC 40 and the second electrode block 32 are insulated from each other by an insulating member (not shown).

[0057] The base 50 is a plate-like metal member that supports the MCC 40. The base 50 may also be provided with a cooling water passage (not shown) inside.

[0058] As shown in FIG. 6, the optical unit 60 includes a first holder 61, a second holder 62, an FAC lens array 63, and a beam twister array 64.

[0059] The first holder 61 and the second holder 62 are both configured to receive the second laser light LB E The first holder 61 and the second holder 62 are made of a material that transmits light, for example, synthetic quartz. The first holder 61 and the second holder 62 hold the FAC lens array (collimator lens array) 63 and the beam twister array 64 so as to sandwich them in the Z direction. As shown in FIG. 6, the second holder 62 is attached to the MCC 40 via an adhesive 65. The beam twister array 64 is attached to the first holder 61 and the second holder 62 via an adhesive 66. The FAC lens array 63 is attached to the beam twister array 64 via the adhesive 66. That is, the optical unit 60 is attached to the MCC 40 via the adhesives 65 and 66. In this embodiment, the adhesives 65 and 66 are photocurable adhesives. For example, the adhesives 65 and 66 are mainly made of ultraviolet curable resin.

[0060] 7A and 7B, the FAC lens array 63 has a convex lens 631 having a longitudinal direction in the Y direction. E The first surface 63a, which is the incident surface of the second laser beam LB, is a flat surface. ESecond surface 63b, which is the exit surface of the lens 631, i.e., the surface on which convex lens 631 is formed, has irregularities. In the following description, a portion where irregularities of a predetermined amount or more are formed is called a curvature portion, and a portion where irregularities are less than a predetermined amount is called a flat portion. More specifically, a surface that includes only irregularities where the angle θ between the surface of the convex portion and the bottom surface of the concave portion (hereinafter referred to as curvature portion angle θ (see FIG. 14)) is less than 35° is a flat portion, and a surface that includes irregularities where the curvature portion angle θ is 35° or more is a curvature portion.

[0061] The second laser light LB emitted from each of the multiple emitters 11 E After passing through the convex lens 631, the spread of the light in the fast axis direction is collimated. In other words, the convex lens 631 is a kind of collimating lens. Note that, instead of the convex lens 631, a plurality of collimating lenses may be disposed for each emitter 11.

[0062] As shown in FIGS. 6 and 7B, a first antireflection layer AR1 is provided on a first surface 63a of the FAC lens array 63, and a second antireflection layer AR2 is provided on a second surface 63b.

[0063] As shown in FIG. 7B, the first antireflection layer AR1 is a dielectric multilayer film in which tantalum oxide films (Ta2O5) and silicon oxide films (SiO2) are alternately laminated. The number of layers in the first antireflection layer AR1 is 8. That is, the first antireflection layer AR1 has four tantalum oxide film layers and four silicon oxide film layers. The thickness of the first antireflection layer AR1 is 700 nm.

[0064] The second antireflection layer AR2 is also a dielectric multilayer film in which tantalum oxide films and silicon oxide films are alternately laminated. However, the number of layers in the second antireflection layer AR2 is four. That is, the second antireflection layer AR2 has two tantalum oxide films and two silicon oxide films. The thickness of the second antireflection layer AR2 is 200 nm.

[0065] First laser light LB in this embodiment MThe wavelength range of the first laser light LB is 400 nm or more and 450 nm or less. However, it is not limited thereto. M The wavelength range may be from 380 nm to 465 nm, in other words, from ultraviolet to blue.

[0066] The type, number of layers, and thickness of the first antireflection layer AR1 are set so that the reflectance of the first antireflection layer AR1 is 0.005% for light in this wavelength range, and the type, number of layers, and thickness of the second antireflection layer AR2 are set so that the reflectance of the second antireflection layer AR2 is 0.05%.

[0067] As shown in Fig. 8, the beam twister array 64 is an optical component in which a plurality of beam twisters 641 are integrated in an array corresponding to a plurality of emitters 11. Note that the number of beam twisters 641 shown in Fig. 8 is different from the actual number. The longitudinal direction of the beam twister array 64 is the Y direction, which is the same as the longitudinal direction of the FAC lens array 63.

[0068] The beam twister 641 also transmits the second laser beam LB E The incident surface on which the second laser beam LB enters and the exit surface from which the second laser beam LBE exits are cylindrical lenses each having the same convex curvature. However, this curvature is smaller than that of the convex lens 631. Therefore, E The third surface 64a is the incident surface of the second laser beam LB E The unevenness of each of the fourth surfaces 64b, which are the exit surfaces of the beam twister array 64, is sufficiently smaller than the unevenness of the second surface 63b of the FAC lens array 63. In addition, the curvature angle θ of the third surface 64a and the fourth surface 64b of the beam twister array 64 is also sufficiently smaller, about 14°, than the curvature angle θ of the second surface 63b of the FAC lens array 63. In other words, the third surface 64a and the fourth surface 64b of the beam twister array 64 are each flat.

[0069] The second laser light LB transmitted through the FAC lens array 63 Eis rotated by 90 degrees by passing through the beam twister array 64. The beam twister array 64 rotates the second laser light LB E The FAC lens array 63 is disposed behind the FAC lens array 63 at a distance from the FAC lens array 63 in the X direction, which is the traveling direction of the laser beam.

[0070] As shown in FIG. 6, a third antireflection layer AR3 is provided on a third surface 64a of the beam twister array 64, and a fourth antireflection layer AR4 is provided on a fourth surface 64b.

[0071] The type, number and thickness of each layer of the third antireflection layer AR3 and the fourth antireflection layer AR4 are the same as the type, number and thickness of each layer of the first antireflection layer AR1. That is, both the third antireflection layer AR3 and the fourth antireflection layer AR4 are dielectric multilayer films of a total of eight layers in which tantalum oxide films and silicon oxide films are alternately stacked. In addition, each film thickness is 700 nm. Therefore, the type, number and thickness of each layer of the third antireflection layer AR3 and the fourth antireflection layer AR4 are set so that the reflectance for light in the ultraviolet to blue wavelength range is 0.005%.

[0072] In the first to fourth antireflection layers AR1 to AR4, layers of the same composition do not necessarily have the same thickness. That is, the tantalum oxide films of the respective layers may have different thicknesses. Similarly, the silicon oxide films of the respective layers may have different thicknesses. In addition, as will be described in detail later, the types, number of layers, and thicknesses of the respective layers of the first to fourth antireflection layers AR1 to AR4 are not particularly limited to the values ​​described above.

[0073] [Findings that led to this disclosure] Fig. 9 is a schematic diagram of an external resonator at the time of design. Fig. 10A is a wavelength spectrum of a first laser light in an ideal state. Fig. 10B is a diagram showing the drive current dependency of the output of the first laser light in an ideal state.

[0074] As shown in FIG. 9, in the laser oscillator 100, a second laser beam LB E and the first laser light LBM A fifth antireflection layer AR5 is provided on one of the two transmission surfaces, and a sixth antireflection layer AR6 is provided on the other. M As described above, the first laser beam LB in the external cavity mirror OC is incident on the seventh antireflection layer AR7. M A first reflective layer R1 is provided on the exit surface of the light emitting element.

[0075] The type, number of layers, and thickness of each of the fifth to seventh antireflection layers AR5 to AR7 are the same as those of the first antireflection layer AR1. In the laser oscillator 100 shown in FIG. 9, the first to seventh antireflection layers AR1 to AR7 are all configured to receive the first laser light LB M The type, number of layers, and film thickness of each layer are set so that the reflectance is 0.005% for light in the wavelength range of 1000 nm. In other words, the film thickness and layer structure are set to be the same as those of the first antireflection layer AR1 shown in FIG. 7B. On the other hand, the first reflective layer R1 has a reflectance of 0.005% for light in the wavelength range of 1000 nm. M The optical design is such that the reflectance for light in this wavelength range is 10% to 15%.

[0076] As described above, the first end face coating layer 12 of the laser diode bar 10 is M The second end face coating layer 13 has a reflectance of 99.5% or more for light in this wavelength range.

[0077] By carrying out the optical design in this manner, the first laser light LB M In this ideal state, the first laser light LB is hardly subjected to unnecessary reflections from multiple optical components arranged on the optical path, and the output should be as set. M has a single peak near 440 nm. Also, as shown in FIG. 10B, when the drive current applied to the laser diode bar 10 is greater than the threshold current I TH When the laser oscillator 100 emits the first laser beam LB MAlso, the first laser beam LB starts to be emitted in proportion to the drive current. M The output of becomes larger.

[0078] However, when the inventors of the present application actually fabricated a plurality of laser oscillators 100 and operated each of them, the first laser light LB M It was found that the output of the engine was 7% to several tens of percent lower than the design value.

[0079] In order to investigate the cause of this, the reflectance of the first end face coating layer 12 was changed and the first laser light LB M By increasing the internal reflection in the optical path of the first laser beam LB M We investigated how the properties of

[0080] Fig. 11A is a wavelength spectrum of the first laser light when the reflectance of the first end face coating layer is 1%. Fig. 11B is a diagram showing the drive current dependency of the output of the first laser light when the reflectance of the first end face coating layer is 2%. Fig. 12A is a wavelength spectrum of the first laser light when the reflectance of the first end face coating layer is 2%. Fig. 12B is a diagram showing the drive current dependency of the output of the first laser light when the reflectance of the first end face coating layer is 2%. Fig. 13 is a schematic diagram of an actual external resonator.

[0081] First laser light LB M When the reflectance of the first end face coating layer 12 is adjusted to 1% for light in the wavelength range of the first laser light LB M In addition to the peak near 440 nm, a side peak was observed on the longer wavelength side. M It was observed that the output of the generator did not increase, i.e., a phenomenon known as thermal saturation occurred.

[0082] Furthermore, when the reflectance of the first end face coating layer 12 is adjusted to 2%, as shown in FIG. 12A, the first laser light LB MIn the graph, the peak near 440 nm was split into two. Also, it was found that the side peak was stronger than in the case shown in FIG. 11A. Also, as shown in FIG. 12B, the threshold current I TH From I TH1 (>I TH ) was observed. When the driving current was increased, the first laser beam LB M A decrease in output was observed.

[0083] From the above, it was found that unnecessary reflections occurred inside the laser oscillator 100 that was actually manufactured, and this caused the first laser light LB M It was estimated that a power output drop of 100m was occurring.

[0084] In order to investigate the cause of the internal reflection, the first laser beam LB M Analysis of each optical component on the optical path revealed that the film thickness of the second antireflection layer AR2 fluctuated on the second surface 63b of the FAC lens array 63. Specifically, it was found that the film thickness of the second antireflection layer AR2 was the same as the set value in the flat portion described above, whereas the film thickness was thinner in the curved portion.

[0085] The variation in thickness of the second antireflection layer AR2 on the second surface 63b of the FAC lens array 63 will be further described with reference to FIGS.

[0086] Fig. 14 is a schematic diagram for explaining the angle of the curvature portion, and Fig. 15 is a diagram showing the dependency of the variation rate from the flat portion film thickness on the angle of the curvature portion.

[0087] As described above, the curvature angle θ is the angle between the surface of the convex portion and the bottom surface of the concave portion. Meanwhile, as shown in Fig. 14, the curvature angle θ changes depending on the position of the convex portion, in this case, the surface of the convex lens 631. In the example shown in Fig. 14, the curvature angle θ increases in the order of position A, position B, and position C. The curvature angle at position C is the same as the curvature angle θ at the flat portion (position D), and is approximately zero.

[0088] Incidentally, in order to prevent damage to the optical components due to heating during film formation, the first to seventh antireflection layers AR1 to AR7 are usually formed by a physical vapor deposition method such as a sputtering method or an electron beam evaporation method. In general, in a physical vapor deposition method, the amount of particles that fly to the film formation surface to become an attached film varies depending on the area of ​​the film formation surface as seen from the particles. More specifically, when the traveling direction of the flying particles is perpendicular to the film formation surface, the amount of adhesion increases, and the more acute the angle between the traveling direction of the flying particles and the film formation surface, the more the amount of adhesion decreases. Therefore, when the first to seventh antireflection layers AR1 to AR7 are formed on each optical component, each optical component is arranged so that the film formation surface is perpendicular to the traveling direction of the flying particles.

[0089] The first surface 63a of the FAC lens array 63 and the third surface 64a and the fourth surface 64b of the beam twister array 64 can be regarded as flat surfaces. M The first laser beam LB at the two transmission surfaces and the external cavity mirror OC M Therefore, the first antireflection layer AR1 and the third to seventh antireflection layers AR3 to AR7 formed on these surfaces have thicknesses exactly as set, and there is little variation in thickness within the film formation surface.

[0090] On the other hand, the second surface 63b of the FAC lens array 63 is not flat because the convex lenses 631 are provided on the second surface 63b. In each portion of the second surface 63b, the above-mentioned curvature angle θ changes continuously within a range from 0° to about 60°.

[0091] However, when the curvature angle θ becomes large, the angle between the traveling direction of the flying particles and the deposition surface becomes acute, so the amount of adhesion of the flying particles decreases, and as a result, the film thickness decreases in the portion where the curvature angle θ is large.

[0092] As shown in Fig. 15, when the curvature angle θ exceeds 30°, the variation rate from the flat portion thickness exceeds -15% at that portion. When the curvature angle θ exceeds 50°, the variation rate from the flat portion thickness exceeds -30% at that portion. This tendency was the same regardless of the physical vapor deposition method. In fact, on the second surface 63b of the FAC lens array 63, the thickness of the second antireflection layer AR2 was reduced by up to about 40% from the flat portion thickness.

[0093] Normally, when the thickness of a dielectric multilayer film varies, the reflectance also varies. When the first antireflection layer AR1 has the structure shown in Fig. 7B, the rate of variation in reflectance becomes large.

[0094] FIG. 16 is a diagram showing the wavelength dependency of the reflectance of the first antireflection layer when the film thickness is changed.

[0095] 16, when the thickness of the first antireflection layer AR1 is set to a set value (=700 nm), the reflectance for light in the wavelength range of 400 nm to 500 nm is a designed value of 0.005% (actual measurement is 0.1% or less). Note that the used wavelength range (400 nm to 450 nm) shown in FIG. 16 is the reflectance of the first laser light LB M This corresponds to the wavelength range.

[0096] On the other hand, when the thickness of the first antireflection layer AR1 is reduced to 610 nm (a reduction rate from the flat portion thickness: -13%), the design reflectance is 0.005% for light in the wavelength range of 440 nm or less, whereas the reflectance starts to increase when the wavelength of the light exceeds 450 nm. When the wavelength of the light reaches 500 nm, the reflectance increases to 60%. When the thickness of the first antireflection layer AR1 is reduced to 460 nm (a reduction rate from the flat portion thickness: -34%), the reflectance is only a few percent even when the wavelength of the light is 350 nm, and when the wavelength of the light becomes longer, the reflectance increases significantly. In the above-mentioned wavelength range of use, the reflectance exceeds 80%.

[0097] As described above, the thickness of the second antireflection layer AR2 is reduced at the curvature portion, so that the first laser light LB MThe reflectance increases significantly for light in the wavelength range of 100 nm to 150 nm. It was estimated that this caused a kind of resonance between the second end face coating layer 13 and the second antireflection layer AR2 provided on the second surface 63b of the FAC lens array 63, as shown in FIG. 13. This resonance inhibits external resonance, and the first laser light LB M It was estimated that the output loss of the first laser beam LB M If the output of the optical unit 60 decreases by 10% or more, a part of the optical unit 60 will burn, and the first laser light LB M The optical axis of the first laser beam LB was shifted. M In addition to the resonance between the second end face coating layer 13 and the second antireflection layer AR2, the output loss of the first laser light LB M This also includes the loss that occurs when the light passes through each optical component.

[0098] In consideration of the above, the inventors of the present application have decided to suppress the occurrence of resonance between the second end face coating layer 13 and the second antireflection layer AR2 by making the second antireflection layer AR2 have low fluctuations in reflectance even when the rate of fluctuation in film thickness is high. Specifically, the layer structure of the second antireflection layer AR2 is a dielectric multilayer film in which two layers of Ta2O5 and two layers of SiO2 are alternately stacked, as shown in Fig. 7B.

[0099] FIG. 17 is a diagram showing the wavelength dependence of the reflectance of the first antireflection layer and the second antireflection layer.

[0100] The wavelength dependency of the reflectance of the first antireflection layer AR1 is as described above. That is, the design value of the reflectance for light in the wavelength range of 400 nm to 450 nm is 0.005% (actual measurement is 0.1% or less). Also, as described above, the reflectance is highly dependent on the film thickness.

[0101] On the other hand, as shown in FIG. 17, the wavelength dependency of the reflectance of the second antireflection layer AR2 is extremely small compared to that of the first antireflection layer AR1. The design reflectance of the second antireflection layer AR2 for light in the wavelength range of 400 nm to 450 nm is 0.05% (actual measurement is 0.4% or less). On the other hand, even if the film thickness is reduced by 30% from the set value, the reflectance of the second antireflection layer AR2 (hereinafter referred to as the second reflectance) is suppressed to less than 3%. As a result, even if the film thickness fluctuation rate of the second antireflection layer AR2 increases to about 30%, the occurrence of resonance between the second end face coating layer 13 and the second antireflection layer AR2, and thus the first laser light LB, is prevented. M For example, if the set value of the film thickness of the second antireflection layer AR2 is 170 nm, and the configuration of the dielectric film included in the second antireflection layer AR2 is, from the second surface 63b of the optical unit 60, 15 nm of Ta2O5, 15 nm of SiO2, 70 nm of Ta2O5, and 70 nm of SiO2, the actual film thickness of the second antireflection layer AR2 may be 120 nm or more and 170 nm or less, and in this case, the second reflectance is greater than 0.05% and less than 3%.

[0102] On the other hand, in the case of the first antireflection layer AR1, when the film thickness is reduced by 30% from the set value, the reflectance (hereinafter referred to as the first reflectance) increases to about 80%. This causes the occurrence of resonance between the second end face coating layer 13 and the second antireflection layer AR2, and further the reflection of the first laser light LB M In addition, the output loss of the first laser beam LB cannot be suppressed due to the optical axis misalignment. M This will result in a decline in quality.

[0103] It was found that when the second antireflection layer AR2 is configured so that the second reflectance is smaller than 0.3%, the increase in the second reflectance with respect to the film thickness variation becomes too large. Specifically, when the film thickness of the second antireflection layer AR2 is reduced by 30%, the second reflectance exceeds 2%. On the other hand, it was found that when the set value of the second reflectance is made larger than 0.6%, the influence of internal resonance cannot be ignored, in addition to the slight reflection occurring on the first surface 63a of the FAC lens array 63 and the third and fourth surfaces 64a and 64b of the beam twister array 64.

[0104] In view of the above, the second reflectance is preferably not less than 0.3% and not more than 0.6%.

[0105] In addition, the second laser light LB in the optical unit 60 E and the first laser light LB M It has been found that if the sum of the reflectivities of the transmitting surfaces of the first and second reflectors exceeds a predetermined reflectivity, in this case 1.0%, a gain greater than a predetermined value occurs due to internal resonance in the external resonator, inhibiting external resonance. In view of this, it is preferable that the first reflectivity is 0.2% or less. The predetermined reflectivity depends on the configuration of the laser oscillator 100, in particular the reflectivity of the first laser light LB M This can be appropriately changed depending on the number of optical components arranged on the optical path, the shapes of each of the optical components, etc.

[0106] As shown in FIG. 17, the reflectance of the first antireflection layer AR1 increases rapidly when the wavelength of light exceeds 500 nm. On the other hand, the reflectance of the second antireflection layer AR2 increases only gradually even when the wavelength of light exceeds 500 nm. The wavelength range in which the reflectance is 3% or less is about 380 nm to 525 nm for the first antireflection layer AR1, whereas it is wider, about 340 nm to 575 nm, for the second antireflection layer AR2. Even when the wavelength is 800 nm, the reflectance is suppressed to about 10%. In other words, the wavelength dependency of the reflectance for light in the ultraviolet to visible wavelength range is smaller for the second antireflection layer AR2 than for the first antireflection layer AR1.

[0107] [Effects, etc.] As described above, the optical unit 60 according to this embodiment is an optical unit 60 used inside an external cavity type laser oscillator.

[0108] The optical unit 60 receives the first laser light LB emitted from an external oscillator configured in the laser oscillator 100. M The optical system has two optical components, an FAC lens array 63 and a beam twister array 64, through which the laser beam passes.

[0109] First laser light LB in the FAC lens array 63 M Among these transmitting surfaces, the second surface 63b has a curvature portion having a predetermined or greater unevenness, while the other transmitting surfaces, i.e., the first surface 63a of the FAC lens array 63 and the third and fourth surfaces 64a and 64b of the beam twister array 64, are flat surfaces without a curvature portion.

[0110] A first anti-reflection layer AR1 is provided on these flat surfaces, and the first laser light LB M The reflectance of the first antireflection layer AR1 in this wavelength range is a first reflectance.

[0111] A second anti-reflection layer AR2 is provided on the second surface 63b of the FAC lens array 63 including the curvature portion, and the first laser light LB M The reflectance of the second antireflection layer AR2 in this wavelength range is a second reflectance.

[0112] The first reflectance and the second reflectance are each lower than a predetermined reflectance, in this case 1.0%, and the second reflectance is higher than the first reflectance.

[0113] Moreover, the rate of variation of the second reflectance with respect to the film thickness variation of the second antireflection layer AR2 is smaller than the rate of variation of the first reflectance with respect to the film thickness variation of the first antireflection layer AR1.

[0114] By configuring the optical unit 60 in this way, the first laser light LB M Even if there is a transparent surface with a curved portion on the optical path of the first laser beam LB M This can suppress output loss.

[0115] It is preferable that the second reflectance is smaller than 2% when the thickness of the second antireflection layer is reduced by 30% from the set value. M This can reliably suppress output loss.

[0116] In the optical unit 60, the first laser light LB MWhen the sum of the reflectances of the transmitting surfaces is equal to or less than a predetermined reflectance (1.0%), the external oscillator does not generate a gain equal to or more than a predetermined value due to internal resonance. M The transmitting surfaces are the first surface 63a and the second surface 63b of the FAC lens array 63, and the third surface 64a and the fourth surface 64b of the beam twister array 64. Since the gain above a predetermined level due to internal resonance does not occur in the external oscillator, the first laser light LB M This can reliably suppress output loss.

[0117] The second reflectance is preferably 0.3% or more and 0.6% or less. In this way, it is possible to prevent the second reflectance of the second antireflection layer AR2 from increasing too much with respect to the film thickness variation. In addition, the first laser light LB in the optical unit 60 M The total effect of internal reflection on the transmission surface of the laser beam LB during external oscillation can be suppressed. M This can reliably suppress output loss.

[0118] The first reflectance is preferably 0.2% or less. By doing so, the first laser light LB in the optical unit 60 M The total effect of internal reflection on the transmission surface of the laser beam LB during external oscillation can be suppressed. M This can reliably suppress output loss.

[0119] Each of the first antireflection layer AR1 and the second antireflection layer AR2 is preferably a dielectric multilayer film in which a dielectric film having a high refractive index and a dielectric film having a low refractive index are alternately laminated. By appropriately setting the refractive index and film thickness of each of the first antireflection layer AR1 and the second antireflection layer AR2, the first antireflection layer AR1 and the second antireflection layer AR2 can respectively absorb the first laser light LB M It is possible to make the reflectance of the film have a desired value with respect to light in the wavelength range.

[0120] In this embodiment, Ta2O5 is selected as the high refractive index dielectric film, and SiO2 is selected as the low refractive index dielectric film. However, this is not particularly limited, and for example, HfO2 may be selected as the high refractive index dielectric film, and Al2O3 may be selected as the low refractive index dielectric film. In addition, both Ta2O5 and HfO2 may be used as the high refractive index dielectric film, and both SiO2 and Al2O3 may be used as the low refractive index dielectric film.

[0121] That is, the first antireflection layer AR1 and the second antireflection layer AR2 in the present disclosure each include at least a first group of dielectric films and a second group of dielectric films. The first group of dielectric films includes at least one of Ta2O5 and HfO2. The second group of dielectric films includes at least one of SiO2 and Al2O3.

[0122] It should be noted that the first group of dielectric films may be made of dielectric films other than Ta2O5 and HfO2, and may be made of dielectric films other than SiO2 and Al2O3.

[0123] The optical unit according to claim 7, The second antireflection layer AR2 is preferably formed by alternately stacking Ta2O5 and SiO2. It is particularly preferable that the second antireflection layer AR2 is formed by alternately stacking Ta2O5 and SiO2 twice. By appropriately setting the thicknesses of Ta2O5 and SiO2, the second reflectance itself can be appropriately reduced, and the variation rate of the second reflectance with respect to the film thickness variation can be suppressed to a low level.

[0124] The first antireflection layer AR1 is preferably configured by alternately stacking Ta2O5 and SiO2 four or more times. In this way, the first laser light LB M In this way, the first reflectance can be suppressed to a sufficiently low level, specifically, to 0.1% or less, for light in the wavelength range of the first laser light LB M This can suppress the total effect of internal reflection at the transmission surface of the first laser beam LB during external oscillation.M This can reliably suppress output loss.

[0125] The optical unit 60 has at least an FAC lens array 63 and a beam twister array 64 as a plurality of optical components.

[0126] The FAC lens array 63 is configured to receive the second laser light LB emitted from each of the emitters 11 of the laser diode bar 10 serving as a laser light source. E The beam twister array 64 parallelizes the spread of the second laser light LB transmitted through the FAC lens array 63 in the first axis direction. E Rotate by 90 degrees.

[0127] Moreover, the optical unit 60 further includes a first holder 61 and a second holder 62 that hold the FAC lens array 63 and the beam twister array 64 so as to sandwich them in the fast axis direction.

[0128] The curvature portion and the second antireflection layer AR2 are provided on at least one of the two transmission surfaces of the FAC lens array 63, that is, on the second surface 63b in this embodiment.

[0129] The beam twister array 64 is attached to the first holder 61 and the second holder 62 via an adhesive 66. In addition, the FAC lens array 63 is attached to the beam twister array 64 via an adhesive 66.

[0130] By configuring the optical unit 60 in this manner, each of the second laser beams LB E In this way, the spread of the second laser light LB in the fast axis direction can be suppressed, and the overlap in the slow axis direction can be separated. E Easily use one first laser beam LB M can be combined with

[0131] The laser oscillator 100 according to this embodiment at least includes a semiconductor laser element having a plurality of emitters 11, an optical unit 60, a diffraction grating (optical coupling element) DG, and an external cavity mirror OC.

[0132] The semiconductor laser element in this embodiment is a laser diode bar 10 having a plurality of emitters 11. In addition, the external cavity mirror OC is provided with a first reflective layer R1.

[0133] The diffraction grating DG is disposed between the optical unit 60 and the external cavity mirror OC, and is configured to receive the second laser beams LB emitted from the multiple emitters 11 and transmitted through the optical unit 60. E The first laser beam LB is generated by combining the first laser beam LB M Convert to.

[0134] The external cavity mirror OC couples the first laser beam LB to the diffraction grating DG. M The light is reflected via a diffraction grating DG toward a second end face coating layer (second reflective layer) 13 provided on the rear end face of the laser diode bar 10.

[0135] The first laser beam LB passes through the external cavity mirror OC. M is emitted from the laser oscillator 100.

[0136] By configuring the laser oscillator 100 in this manner, a plurality of second laser beams LB E The high-power first laser beam LB M can be emitted.

[0137] The semiconductor laser elements may be a plurality of laser diodes each having a single emitter 11. An optical unit 60 may be provided for each laser diode.

[0138] In this case, the optical unit 60 includes at least a collimator lens and a beam twister. The collimator lens is configured to collimate the second laser light LB emitted from the laser diode. EThe beam twister parallelizes the first axial spread of the second laser beam LB that has passed through the collimator lens. E is rotated by 90°. The first holder 61 and the second holder 62 hold the collimator lens and the beam twister so as to sandwich them in the fast axis direction.

[0139] The curvature portion and the second antireflection layer AR2 are arranged to reflect the second laser light LB from the collimator lens. E The beam twister is attached to the first holder 61 and the second holder 62 via an adhesive 66. The collimating lens is attached to the beam twister via an adhesive 66.

[0140] In addition, a plurality of second laser beams LB E The first laser beam LB M For coupling, an optical coupling element other than the diffraction grating DG, for example, a prism, etc. may be used.

[0141] The laser processing apparatus 1000 according to this embodiment includes at least a laser oscillator 100 and a laser head 800 .

[0142] By configuring the laser processing device in this manner, it is possible to irradiate the workpiece W with a high-power processing laser light to perform laser processing on the workpiece W. This allows, for example, to process the workpiece W at high speed. In addition, processing such as laser cutting and laser drilling can be easily performed on the workpiece W that is a thick plate.

[0143] The laser processing apparatus 1000 may be equipped with one or more laser oscillators 100. This is appropriately changed according to the specifications required for the laser processing.

[0144] When one laser oscillator 100 is mounted, the laser head 800 emits a first laser beam LB M and irradiates it towards the workpiece W.

[0145] When a plurality of laser oscillators 100 are mounted, the laser head 800 receives a plurality of first laser beams LB emitted from the plurality of laser oscillators 100. M The laser beam is combined into one combined laser beam (third laser beam) LB and irradiated toward the workpiece W.

[0146] The optical unit 60 of the present disclosure may include optical components other than the FAC lens array 63 and the beam twister array 64.

[0147] That is, in the optical unit 60 of the present disclosure, the first laser light LB M The optical system has at least two optical components through which the light is transmitted.

[0148] First laser light LB in a plurality of optical components M At least one of the transmitting surfaces has a curvature portion having a predetermined or greater degree of unevenness.

[0149] A plurality of first laser beams LB M A first anti-reflection layer AR1 is provided on the flat surface that does not have a curved portion among the transmitting surfaces of the first laser light LB. M The reflectance of the first antireflection layer AR1 in this wavelength range is a first reflectance.

[0150] The curvature portion is provided with a second anti-reflection layer AR2. M The reflectance of the second antireflection layer AR2 in this wavelength range is a second reflectance.

[0151] The first reflectance and the second reflectance are each lower than a predetermined reflectance, and the second reflectance is higher than the first reflectance. Furthermore, the rate of variation of the second reflectance with respect to the film thickness variation of the second antireflection layer AR2 is smaller than the rate of variation of the first reflectance with respect to the film thickness variation of the first antireflection layer AR1.

[0152] As can be seen from the above, the first laser light LB in the optical unit 60 M Of the transmitting surfaces, the surface on which the second antireflection layer AR2 is provided is not limited to the second surface of the FAC lens array 63.

[0153] Fig. 18 is a schematic cross-sectional view of another FAC lens array. The FAC lens array 63 shown in Fig. 18 differs from the FAC lens array 63 shown in Fig. 7B in that it has convex lenses 632 that are convex on both the first surface 63a and the second surface 63b.

[0154] In this case, the first surface 63a of the FAC lens array 63 also has a curvature. For this reason, as shown in Fig. 18, the first surface 63a is also provided with a second antireflection layer AR2 having the structure shown in Fig. 7B. In this way, in the external resonator formed in the laser oscillator 100, the first laser light LB during external oscillation is M This can suppress output loss.

[0155] At least one of the third surface 64a and the fourth surface 64b of the beam twister array 64 may have a curvature portion having a predetermined or greater unevenness. In this case, by providing a second antireflection layer AR2 having the structure shown in FIG. 7B on the transmission surface having the curvature portion, the first laser light LB during external oscillation in the external resonator formed in the laser oscillator 100 can be prevented from being reflected by the second antireflection layer AR2. M This can suppress output loss. EXAMPLES

[0156] A laser oscillator 100 having the configuration shown in FIG. 2 is manufactured, and a first laser beam LB M In this case, as an example, a second antireflection layer AR2 having the structure shown in FIG. 7B was provided on the second surface 63b of the FAC lens array 63. The output of the first laser light LB was measured. M 7B is provided on the transmitting surface of the FAC lens array 63. That is, the first antireflection layer AR1 is provided on the first surface 63a of the FAC lens array 63, the third surface 64a and the fourth surface of the beam twister array 64, the light entrance surface and the light exit surface of the diffraction grating DG, and the light entrance surface of the external reflecting mirror OC.

[0157] On the other hand, as a comparative example, the first laser light LB MIn other words, the first antireflection layer AR1 having the structure shown in FIG. 7B was also provided on the second surface 63b of the FAC lens array 63. Furthermore, the first laser light LB emitted from the laser oscillator 100 of the comparative example was M The output was measured.

[0158] In both the example and the comparative example, a laser diode bar 10 having 38 emitters 11 was used, a drive current of 60 A was applied to the laser diode bar 10, and the second laser light LB was emitted from each emitter 11. E was emitted.

[0159] FIG. 19 is a diagram showing the output of the first laser light in the example and the comparative example.

[0160] As is clear from FIG. 19, in the comparative example, the first laser light LB M The output of the battery was significantly lower than the theoretical value. The decrease rate was -11% compared to the theoretical value.

[0161] On the other hand, in the embodiment, the first laser light LB M It was found that the decrease rate of the output of the embodiment was significantly reduced compared to the comparative example. The decrease rate in the embodiment was about -1% with respect to the theoretical value.

[0162] From the above, in the embodiment, in the external resonator configured in the laser oscillator 100, the first laser light LB during external oscillation M It is clear that the output loss of the first laser beam LB is significantly suppressed compared to the comparative example. M It is presumed that this is because the provision of the second antireflection layer AR2 on the surface having the curved portion among the transmitting surfaces suppresses the inhibition of external resonance. [Industrial Applicability]

[0163] INDUSTRIAL APPLICABILITY The optical unit of the present disclosure is useful when used in an external resonance type laser oscillator because it can suppress inhibition of external resonance and suppress output loss of the first laser light during external oscillation. [Explanation of symbols]

[0164] 10 Laser diode bar (semiconductor laser element) 11 Emitter 12 First end face coating layer 13 Second end face coating layer (second reflective layer) 20 Submount 31 First electrode block 32 Second electrode block 40 Microchannel Cooler 50 Base 60 Optical Unit 61 First Holder 62 Second Holder 63 FAC lens array 63a 1st page 63b 2nd side 631, 632 Convex lenses 64 Beam Twister Array 641 Beam Twister 64a Page 3 64b Side 4 65 Adhesive 66 Adhesive 70 Laser Module 80 Case 100 Laser Oscillator 200 Beam combiner 300 Condenser Optical Unit 400 cabinet 500 Control section 600 power supply 700 Optical Fiber 800 Laser Head 900 Stages 1000 Laser processing equipment AR1 1st anti-reflection layer AR2 2nd anti-reflection layer DG Diffraction grating (optical coupling element) LBE Second laser beam LB M First laser beam LB Combined laser light (third laser light) MW Metal Wire OC External Cavity Mirror R1 1st reflective layer

Claims

1. An optical unit used inside an external cavity laser oscillator, The laser device includes at least two optical components through which the first laser light emitted from the laser oscillator passes, At least one surface among the transmission surfaces of the first laser light in the plurality of optical components has a predetermined or greater unevenness and has a curvature portion that collimates the first laser light, a first antireflection layer is provided on a flat surface of the plurality of transmission surfaces that does not have the curved portion, and a reflectance of the first antireflection layer in a wavelength range of the first laser light is a first reflectance; a second antireflection layer is provided on the curvature portion, and a reflectance of the second antireflection layer in a wavelength range of the first laser light is a second reflectance; the first reflectance and the second reflectance are each lower than a predetermined reflectance, and the second reflectance is higher than the first reflectance; An optical unit, comprising: a variation rate of the second reflectance with respect to a variation in thickness of the second antireflection layer, the variation rate of the first reflectance with respect to a variation in thickness of the first antireflection layer being smaller than a variation rate of the first reflectance with respect to a variation in thickness of the first antireflection layer.

2. 2. The optical unit according to claim 1, 13. An optical unit, comprising: a first antireflection layer having a thickness that is 30% smaller than a set thickness of said second antireflection layer; and a second antireflection layer having a thickness that is 30% smaller than a set thickness of said second antireflection layer.

3. 3. The optical unit according to claim 2, the second antireflection layer is formed by alternately laminating different types of dielectric films, The thickness of the second antireflection layer is set to 170 nm. The dielectric film included in the second antireflection layer is configured as follows, in order from the transmission surface having the curvature portion in the optical unit: Ta ２ O ５ is 15 nm, SiO ２ is 15 nm, Ta ２ O ５ is 70 nm, SiO ２ is 70 nm, the actual film thickness of the second antireflection layer is 120 nm or more and 170 nm or less, and the second reflectance is greater than 0.05% and smaller than 3%.

4. 2. The optical unit according to claim 1, An optical unit characterized in that, when the sum of the reflectances of the transmitting surfaces of the multiple first laser beams is equal to or less than the specified reflectance, no gain greater than a specified level is generated due to internal resonance in the laser oscillator.

5. 3. The optical unit according to claim 2, The optical unit according to claim 1, wherein the second reflectance is equal to or greater than 0.3% and equal to or less than 0.6%.

6. 6. The optical unit according to claim 5, The optical unit according to claim 1, wherein the first reflectance is 0.2% or less.

7. 5. The optical unit according to claim 4, The optical unit according to claim 1, wherein the predetermined reflectance is 1.0% or less.

8. 3. The optical unit according to claim 2, T ２ O ５ and HfO ２ A group including at least one of the above is defined as a first group of dielectric films, and SiO ２ and Al ２ O ３ When a group including at least one of the above is defined as a second group of dielectric films, An optical unit, wherein the first antireflection layer and the second antireflection layer each include at least the first group of dielectric films and the second group of dielectric films, respectively.

9. 9. The optical unit according to claim 8, The second anti-reflection layer is made of Ta. ２ O ５ and SiO ２ An optical unit comprising:

10. 10. The optical unit according to claim 9, The second anti-reflection layer is made of Ta. ２ O ５ and SiO ２ An optical unit comprising:

11. 9. The optical unit according to claim 8, The first antireflection layer is made of Ta. ２ O ５ and SiO ２ An optical unit comprising:

12. 2. The optical unit according to claim 1, An optical unit, characterized in that the wavelength range of the first laser light is 380 nm or more and 465 nm or less.

13. 13. The optical unit according to claim 1, The plurality of optical components include: a collimator lens that collimates the spread of the second laser light emitted from the laser light source included in the laser oscillator in a fast axis direction; and a beam twister that rotates the second laser light transmitted through the collimator lens by 90°. the optical unit further includes a first holder and a second holder that hold the collimator lens and the beam twister so as to sandwich them in the fast axis direction, the curvature portion and the second antireflection layer are provided on at least one of the two transmission surfaces of the collimator lens, The optical unit according to claim 1, wherein the beam twister is attached to the first holder and the second holder via an adhesive.

14. A semiconductor laser element having a plurality of emitters; An optical unit according to claim 13; An external cavity mirror having a first reflective layer; the semiconductor laser element is a laser diode bar having a plurality of the emitters, or a plurality of laser diodes having a single emitter; and a light coupling element disposed between the optical unit and the external cavity mirror, coupling a plurality of the second laser beams emitted from the plurality of emitters and transmitted through the optical unit to convert the plurality of second laser beams into the first laser beam, the external cavity mirror reflects the first laser light coupled by the optical coupling element toward a second reflective layer provided on the semiconductor laser element via the optical coupling element; a first laser beam being emitted through the external resonator mirror;

15. The laser oscillator according to claim 14; a laser head that receives the first laser light and irradiates it toward a workpiece.

16. 16. The laser processing apparatus according to claim 15, A laser oscillator is provided, The laser processing apparatus is characterized in that the laser head receives a third laser light, which is a combined laser light formed by combining multiple first laser light beams emitted from multiple laser oscillators, and irradiates the third laser light toward the workpiece.

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