laser device

Abstract

To enhance the flexibility of design in a travelling direction of a wavelength coupling beam.SOLUTION: A laser device comprises: a first mirror and a second mirror that form a resonator; a semiconductor laser element arranged between the mirrors, including a plurality of laser oscillation regions that perform laser oscillation at mutually different wavelengths; a collimator arranged between the semiconductor laser element and the second mirror to convert light emitted from the laser oscillation regions into a plurality of collimated beams; and first and second diffraction gratings arranged in parallel between the collimator and the second mirror. The first diffraction grating diffracts the collimated beams in different directions depending on their wavelengths to make them enter the second diffraction grating. The second diffraction grating further diffracts the plurality of collimated beams diffracted by the first diffraction grating to form a wavelength coupling beam and emits the wavelength coupling beam in a first direction. A diaphragm with an opening for making the wavelength coupling beam pass through is arranged between the second diffraction grating and the second mirror. At least a part of the second mirror is a planar mirror reflecting the wavelength coupling beam to return it to the second diffraction grating.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to laser devices. [Background technology]

[0002] A technology has been developed that combines multiple laser beams with different wavelengths emitted from semiconductor laser elements into one beam using a diffraction grating. This technology is called wavelength beam combining (WBC). Patent Document 1 describes a laser device that coaxially superimposes multiple laser beams emitted from semiconductor laser elements using a pair of diffraction gratings to form a single beam. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-120560 Summary of the Invention [Problem to be solved by the invention]

[0004] The laser device described in Patent Document 1 has a configuration that satisfies the resonator conditions even if misalignment occurs in the partial reflecting mirror that constitutes the external resonator. This configuration includes a concave mirror or a cylindrical lens and a plane mirror, which reduces the design freedom in the direction of light beam propagation. [Means for solving the problem]

[0005] In an exemplary embodiment, the laser device of the present disclosure includes a first mirror and a second mirror forming a resonator, a semiconductor laser element disposed between the first mirror and the second mirror and including multiple laser oscillation regions that oscillate at different wavelengths during operation, a collimator disposed between the semiconductor laser element and the second mirror and converting light emitted from the multiple laser oscillation regions into multiple collimated beams, and first and second diffraction gratings disposed parallel to each other between the collimator and the second mirror. The first diffraction grating diffracts the multiple collimated beams in different directions depending on their wavelengths and makes them incident on the second diffraction grating. The second diffraction grating further diffracts the multiple collimated beams diffracted by the first diffraction grating to form a wavelength-combined beam and emits the wavelength-combined beam in a first direction. The laser device further includes an aperture disposed between the second diffraction grating and the second mirror and having an aperture that passes the wavelength-combined beam. At least a portion of the second mirror is a flat mirror that reflects the wavelength-combined beam emitted from the second diffraction grating in a second direction opposite to the first direction and returns it to the second diffraction grating.

[0006] In another exemplary embodiment, the laser device of the present disclosure includes a first mirror and a second mirror forming a resonator, a semiconductor laser element disposed between the first mirror and the second mirror and including multiple laser oscillation regions that oscillate at different wavelengths during operation, a collimator disposed between the semiconductor laser element and the second mirror and converting light emitted from the multiple laser oscillation regions into multiple collimated beams, and first and second diffraction gratings disposed parallel to each other between the collimator and the second mirror. The first diffraction grating diffracts the multiple collimated beams in different directions depending on their wavelengths and makes them incident on the second diffraction grating. The second diffraction grating further diffracts the multiple collimated beams diffracted by the first diffraction grating to form a wavelength-combined beam and emits the wavelength-combined beam in a first direction. At least a portion of the second mirror is a flat mirror and has a reflective region that reflects the wavelength-combined beam emitted from the second diffraction grating in a second direction opposite to the first direction and returns it to the second diffraction grating. The size of the reflection region is between one and two times the beam diameter of the plurality of collimated beams, and the oscillation wavelength of each of the plurality of laser oscillation regions can be controlled by the position of the reflection region. [Effects of the Invention]

[0007] According to the embodiments of the present disclosure, it is possible to increase the degree of freedom in designing the propagation direction of the wavelength-combined beam. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view schematically illustrating an example of the configuration of a laser device according to an embodiment of the present disclosure. [Figure 2A] FIG. 2A is a perspective view schematically illustrating a more detailed configuration example of a semiconductor laser element included in a laser device according to an embodiment of the present disclosure. [Figure 2B] FIG. 2B is a cross-sectional view parallel to the XY plane of the semiconductor laser device 10 of FIG. 2A. [Figure 3] FIG. 3 is a diagram schematically showing diffraction by the first diffraction grating G1 and the second diffraction grating G2. [Figure 4] FIG. 4 is a diagram schematically showing a gain curve of the laser oscillation region and the spectrum of the laser light when oscillating in a longitudinal mode. [Figure 5A] FIG. 5A is a diagram schematically showing how a wavelength-combined beam is formed in a state before the position of the aperture in the X-axis direction is changed by the movable section. [Figure 5B] FIG. 5B is a diagram schematically showing how a wavelength-combined beam is formed in a state where the position of the aperture in the X-axis direction is changed by the movable section. [Figure 6] FIG. 6 is a plan view schematically illustrating another configuration example of a laser device according to an embodiment of the present disclosure. [Figure 7] FIG. 7 is a plan view schematically illustrating yet another configuration example of a laser device according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is a diagram schematically illustrating a modified example of the laser device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a laser device according to an embodiment of the present disclosure will be described in detail with reference to the drawings. Parts that appear in multiple drawings with the same reference numerals indicate the same or equivalent parts. The descriptions of the dimensions, materials, shapes, relative positions, etc. of components are intended to be illustrative and not to limit the scope of the present invention. The sizes and positional relationships of components shown in each drawing may be exaggerated to facilitate understanding.

[0010] First Embodiment An embodiment of a laser device according to the present disclosure will be described with reference to the drawings, in which mutually orthogonal X-axis, Y-axis, and Z-axis are shown for reference.

[0011] First, refer to FIG. 1. A laser device 100 in this embodiment includes a first mirror M1 and a second mirror M2 that form a resonator, and a semiconductor laser element 10 disposed between the first mirror M1 and the second mirror M2. The semiconductor laser element 10 includes multiple laser oscillation regions 10X that oscillate at different wavelengths during operation. In the illustrated example, the semiconductor laser element 10 is a laser bar having four laser oscillation regions 10X. The four laser oscillation regions 10X oscillate at wavelengths λ1, λ2, λ3, and λ4, respectively, and emit laser light having wavelengths λ1, λ2, λ3, and λ4. The number of laser oscillation regions 10X included in one laser bar is not limited to four and may be three, five or more, for example, ten or more. The semiconductor laser element 10 may have multiple ridges or multiple stripe electrodes that define the multiple laser oscillation regions 10X.

[0012] FIG. 2A is a perspective view schematically illustrating a detailed configuration example of the semiconductor laser device 10 according to this embodiment. In the example illustrated in FIG. 2A, the semiconductor laser device 10 includes a multilayer structure 11 including a semiconductor substrate, multiple ridges 13 provided on the multilayer structure 11, and stripe electrodes 15 provided on the multiple ridges 13. For simplicity, FIG. 2A does not depict specific components of the semiconductor laser device 10, such as insulating layers. The multilayer structure 11 includes semiconductor layers, such as a P-side cladding layer, an active layer, and an N-side cladding layer. The ridges 13 can be formed, for example, by etching the upper portion of the P-side cladding layer. When the stripe electrodes 15 function as P-side electrodes, an N-side electrode is provided in contact with the N-type semiconductor layer in the multilayer structure 11. The P-side electrode and the N-side electrode are each connected to a drive circuit. When a predetermined voltage is applied between the P-side electrode and the N-side electrode by the drive circuit, a current flows through each ridge 13 in the Y-axis direction. When the current flowing through the laser oscillation region 10X of the active layer exceeds a threshold, a charge inversion occurs in the laser oscillation region 10X, enabling light within a predetermined wavelength range to be amplified and laser oscillation to occur. The width of each laser oscillation region 10X is determined by the width of the ridge 13 or stripe electrode 15. Each laser oscillation region 10X may be called an "optical waveguide" within the semiconductor laser device 10.

[0013] 2B is a cross-sectional view parallel to the XY plane of the semiconductor laser device 10 of FIG. 2A. The illustrated semiconductor laser device 10 includes a multilayer structure 11 including a first-conductivity-type semiconductor substrate 11a, a first-conductivity-type semiconductor layer 11b, an active layer 11c, and a second-conductivity-type semiconductor layer 11d. Here, the "first conductivity type" refers to one of P-type and N-type, and the "second conductivity type" refers to the other of P-type and N-type. Each of the first-conductivity-type semiconductor layer 11b and the second-conductivity-type semiconductor layer 11d may have a multilayer structure including multiple layers such as cladding layers and guide layers. The active layer 11c may also have a quantum well structure or a multiple quantum well structure.

[0014] Ridges 13 are provided on the upper part of the second conductivity type semiconductor layer 11d. Second conductivity side electrodes (stripe electrodes) 15 are formed on the upper surfaces of the individual ridges 13. First conductivity side electrodes 14 are provided on the lower surface of the first conductivity type semiconductor substrate 11a. Adjacent second conductivity side electrodes 15 are electrically isolated from each other by an insulating layer 17 deposited on the second conductivity type semiconductor layer 11d. Pad electrodes 16 are provided on the second conductivity side electrodes 15.

[0015] The second conductivity type semiconductor layer 11d may include a contact layer in the ridge 13 at a portion that contacts the second conductivity side electrode 15. The ridge 13 defines the shape and size of the laser oscillation region 10X.

[0016] 2A and 2B is merely one example of the semiconductor laser device 10. The configuration of the semiconductor laser device 10 is not limited to this example. The semiconductor laser device 10 does not need to be a single laser bar, but may be a collection of multiple laser bars.

[0017] The semiconductor laser element 10 may be, for example, a semiconductor laser element that emits blue light, a semiconductor laser element that emits green light, or a semiconductor laser element that emits red light. Semiconductor laser elements that emit light other than blue, green, or red, such as ultraviolet or infrared light, may also be used. In this specification, blue light refers to light having a peak emission wavelength in the range of 420 nm to 494 nm. Green light refers to light having a peak emission wavelength in the range of 495 nm to 570 nm. Red light refers to light having a peak emission wavelength in the range of 605 nm to 750 nm. Examples of semiconductor laser elements that emit blue or green light include nitride semiconductors. Examples of nitride semiconductors that can be used include GaN, InGaN, and AlGaN. Examples of semiconductor laser elements that emit red light include InAlGaP-based, GaInP-based, GaAs-based, and AlGaAs-based semiconductors. When the laser device 100 is used to process, for example, metal materials, it is desirable to use a semiconductor laser element 10 that oscillates at a wavelength that is highly absorbed by the metal material to be processed.

[0018] Referring again to FIG. 1, the laser bar constituting the semiconductor laser device 10 has a light-emitting surface 10F where one ends of the plurality of laser oscillation regions 10X are aligned, and a light-reflecting surface 10R where the other ends of the plurality of laser oscillation regions 10X are aligned. A reflective film that forms the first mirror M1 is provided on the light-reflecting surface 10R. An anti-reflection film is provided on the light-emitting surface 10F. An example of such a reflective film and anti-reflection film is a dielectric multilayer film. The resonator formed by the first mirror M1 and the second mirror M2 is called an "external resonator."

[0019] In this embodiment, the laser device 100 includes a collimator 20 disposed between the semiconductor laser element 10 and the second mirror M2. The collimator 20 is configured to convert the light L emitted from the multiple laser oscillation regions 10X into multiple collimated beams 12. The collimator 20 is a collection of collimator lenses. The collimator 20 may be a lens array in which the same number of lenses as the number of laser oscillation regions 10X are formed from a single plastic material, or may be an optical component assembly in which multiple lenses are arranged.

[0020] In FIG. 1, the light L and collimated beam 12 emitted from the semiconductor laser element 10 are shown as simple straight lines. The actual light L and collimated beam 12 are light beams having an intensity distribution in a plane perpendicular to the propagation direction. This intensity distribution can be approximated by a distribution function such as a Gaussian distribution in the plane perpendicular to the propagation direction of the light beam. In this disclosure, the diameter of the beam is referred to as the "beam diameter." The beam diameter is 1 / e with respect to the light intensity at the beam center. 2The intensity distribution of a light beam is defined by the size of the region having a light intensity equal to or greater than the specified value. Here, "e" is Napier's constant. The intensity distribution of a light beam does not necessarily have to be axially symmetric. For example, light emitted from a semiconductor laser device 10 having the configuration shown in FIG. 2 diverges in the Y-axis and X-axis directions as it travels in the Z-axis direction. In this example, the angle of divergence in the Y-axis direction is larger than the angle of divergence in the X-axis direction. Therefore, for the semiconductor laser device 10 in FIG. 2, the Y-axis direction can be called the "fast axis" and the X-axis direction can be called the "slow axis." Immediately after emission, the light L emitted from the semiconductor laser device 10 has an elliptical intensity distribution (near-field pattern) with its major axis in the X-axis (slow axis) direction. However, as it travels in the Z-axis direction, it acquires an elliptical intensity distribution (far-field pattern) with its major axis in the Y-axis (fast axis) direction. The collimator 20 acts to reduce the divergence angles of the light L in the fast axis direction and the slow axis direction. In this case, the collimator 20 may be, for example, a combination of one cylindrical lens (fast axis collimator lens) whose generatrix direction (the direction of zero curvature) of the lens surface is parallel to the X-axis direction, and four cylindrical lenses (slow axis collimator lenses) whose generatrix directions of the lens surfaces are parallel to the Y-axis direction.

[0021] The collimated beam, which has a reduced divergence angle after passing through the collimator 20, is not strictly parallel light, but is approximated to a Gaussian beam, in which the product of the divergence angle and the beam diameter is a finite value. In the drawings, the central axes of the light beams are represented by straight lines to schematically show the direction of travel of such light beams. These straight lines can be considered to represent the rays passing through the centers of the respective light beams.

[0022] 1 includes a first diffraction grating G1 and a second diffraction grating G2 arranged parallel to each other between the collimator 20 and the second mirror M2. The first diffraction grating G1 diffracts each collimated beam 12 in different directions depending on its wavelength, causing the beams to enter the same region 64 of the second diffraction grating G2. The second diffraction grating G2 further diffracts the collimated beams 12 diffracted by the first diffraction grating G1 in the region 64 to form a wavelength-combined beam 40, and emits the wavelength-combined beam 40 in a first direction 50. In the illustrated example, the first direction 50 is parallel to the Z-axis direction, and the emission direction of each collimated beam 12 and the emission direction of the wavelength-combined beam 40 are parallel to each other.

[0023] In this embodiment, the first diffraction grating G1 and the second diffraction grating G2 are transmissive diffraction gratings arranged parallel to each other. In this example, the first diffraction grating G1 and the second diffraction grating G2 have the same structure and face each other so that the direction of extension of the diffraction grooves of the first diffraction grating G1 and the second diffraction grating G2 are parallel to each other. The diffraction groove period (the center-to-center spacing of the diffraction grooves) of the first diffraction grating G1 and the second diffraction grating G2 are equal. This configuration enables the wavelength-combined beam 40 to be emitted in a first direction 50 parallel to the emission direction of each collimated beam 12. The diffraction groove period of each of the first diffraction grating G1 and the second diffraction grating G2 affects the magnitude of the diffraction angle, as will be described later. The diffraction groove period of the first diffraction grating G1 and the diffraction groove period of the second diffraction grating G2 do not need to be strictly the same, but only need to be approximately equal to the extent that the emission directions of the diffracted light beams with different wavelengths that make up the wavelength combined beam 40 are aligned with the first direction 50.

[0024] The configurations and functions of the first diffraction grating G1 and the second diffraction grating G2 will be described below with reference to FIG.

[0025] 3 is a diagram showing a first diffraction grating G1 diffracting multiple collimated beams 12 in different directions depending on their wavelengths and causing them to enter the same region of the second diffraction grating G2. In this example, four collimated beams enter region 64 of the second diffraction grating G2. The collimated beams 12 that enter region 64 are further diffracted by the second diffraction grating G2 and coaxially superimposed to form the wavelength-combined beam 40.

[0026] The angles of incidence α of the four collimated beams 12 incident on the second diffraction grating G2 are denoted as α1, α2, α3, and α4, respectively. The angles of incidence α are the angles formed by the central axes of the collimated beams 12 with respect to the normal direction 66 of the second diffraction grating G2.

[0027] When the diffraction angle of the transmitted diffracted light formed when the collimated beam 12 is incident on the second diffraction grating G2 is β, the relationship of the following formula 1 holds. sinα + sinβ = N m λ (Equation 1) Here, N is the number of grooves per unit length of the second diffraction grating G2, m is the diffraction order, and λ is the wavelength of light. The number of grooves per unit length N is the reciprocal of the grating groove period.

[0028] Assuming that the diffraction order m is 1, for example, when N = 2220, the wavelength λ is 410.0 nm, and the incident angle α is 45.0 degrees, the diffraction angle β is equal to 11.77 degrees. In the example of FIG. 3, of the four collimated beams 12, the collimated beam 12 with wavelength λ = λ4 = 410.0 nm is incident on region 64 of second diffraction grating G2 at an incident angle α = α4 = 45.00 degrees, diffracted, and emitted in first direction 50. In this example, the collimated beams 12 incident on second diffraction grating G2 at incident angles α1, α2, and α3 all form coaxial first-order diffracted light along first direction 50 when their respective diffraction angles β are equal to 11.77 degrees. The magnitudes of the incident angles α1, α2, and α3 are geometrically determined depending on the position of region 64 on second diffraction grating G2. For example, if α1 = 46.26 degrees, α2 = 45.84 degrees, and α3 = 45.42 degrees, then the relationship in Equation 1 is satisfied when λ1 = 416.92 nm, λ2 = 414.63 nm, and λ3 = 412.32 nm. In this way, once the angles of incidence α1, α2, α3, and α4 and the diffraction angle β are determined, the wavelengths λ1, λ2, λ3, and λ4 can be determined from Equation 1. Table 1 shows some examples of wavelengths λ, angles of incidence α, and diffraction angles β that satisfy the relationship in Equation 1.

[0029] [Table 1]

[0030] The multiple laser oscillation regions 10X of the semiconductor laser element 10 are capable of laser oscillation in a predetermined wavelength range including the wavelength λ shown in Table 1, for example. According to the laser device 100 of this embodiment, collimated beams 12 having wavelengths λ that satisfy the relationship in Equation 1 are selectively coaxially superimposed to form a wavelength-combined beam 40. This wavelength-combined beam 40 is reflected by the second mirror M2 and fed back to the laser oscillation region 10X using a configuration described below. As a result, each laser oscillation region 10X can selectively and sharply oscillate at specific wavelengths λ1, λ2, λ3, and λ4 that satisfy Equation 1 within the wavelength range in which laser oscillation is possible.

[0031] FIG. 4 is a diagram illustrating the gain curve of a laser oscillation region 10X and the spectrum of laser light oscillating in a longitudinal mode with a wavelength λ that satisfies Equation 1. Multiple laser oscillation regions 10X included in a single semiconductor laser device 10 may have the same gain curve. However, as shown in Table 1, the wavelengths λ1, λ2, λ3, and λ4 that satisfy Equation 1 vary depending on the incident angles α1, α2, α3, and α4. Therefore, in each laser oscillation region 10X, light with different wavelengths λ1, λ2, λ3, and λ4 is selectively amplified and emitted as laser light. In the example shown in Table 1, the wavelengths λ1, λ2, λ3, and λ4 are in the range from 410.00 nm to 413.92 nm. Therefore, each laser oscillation region 10X of the semiconductor laser device 10 is required to have gain characteristics that enable oscillation over a wider wavelength range than this range.

[0032] In the above description, the angles of incidence α1, α2, α3, and α4 of the collimated beam 12 incident on the region 64 of the second diffraction grating G2 are geometrically determined depending on the position of the region 64. However, before laser oscillation occurs, light having a broad wavelength range can be emitted from the semiconductor laser device 10, as shown by the gain curve in FIG. 4. As a result, the light beam diffracted by the first diffraction grating G1 may be incident on a wider range than the region 64 of the second diffraction grating G2 depending on the wavelength. A special configuration is required to selectively feed back the light beam incident on a specific region 64 of the second diffraction grating G2 to the corresponding laser oscillation region 10X depending on the wavelength. This configuration will be described below.

[0033] As shown in FIG. 1, the laser device 100 in this embodiment includes an aperture 60 disposed between the second diffraction grating G2 and the second mirror M2. The aperture 60 has an aperture 62 that passes the wavelength-combined beam 40. The wavelength-combined beam 40 that passes through this aperture 62 is reflected by the second mirror M2 and then returns to the laser oscillation region 10X of the semiconductor laser device 10 along the same return path as the outward path. Therefore, the position of the aperture 62 in the aperture 60 (the position in the X-axis direction in FIG. 1) determines the position of the region 64 in the second diffraction grating G2. Furthermore, the size of the region 64 in the X-axis direction is determined by the size of the aperture 62 in the X-axis direction.

[0034] In this embodiment, the laser device 100 includes a support member 160 that supports the diaphragm 60, enabling control of the oscillation wavelength in each of the multiple laser oscillation regions 10X depending on the position of the aperture 62. In the illustrated example, the support member 160 has a movable portion 162 that supports the diaphragm 60 so that it can move in a direction intersecting the first direction 50 (in this example, the X-axis direction). Therefore, by adjusting the position of the aperture 62 in the X-axis direction using the movable portion 162, the position of the region 64 on the second diffraction grating G2 can be changed. As a result, it is possible to change the incident angles α1, α2, α3, and α4 and adjust the magnitudes of the wavelengths λ1, λ2, λ3, and λ4 that satisfy Equation 1.

[0035] This will be explained below using a specific example with reference to FIGS. 5A and 5B.

[0036] 5A is a schematic diagram showing how the wavelength-combined beam 40 is formed by coaxially superimposing collimated beams of wavelengths λ1, λ2, λ3, and λ4 that satisfy Equation 1 based on the position of the region 64 on the second diffraction grating G2. For reference, FIG. 5A also shows the wavelength λ1 that satisfies Equation 1 for other positions on the second diffraction grating G2. * , λ2 * , λ3 * , λ4 * The collimated beam (diffracted light) of these wavelengths λ1 is shown by the dashed line. * , λ2 * , λ3 * , λ4* The collimated beam (diffracted light) of wavelength λ1 cannot pass through the aperture 62 of the diaphragm 60 and is blocked by the diaphragm 60. * , λ2 * , λ3 * , λ4 * The light beam of wavelength λ1 does not return to the laser oscillation region 10X. * , λ2 * , λ3 * , λ4 * In reality, this laser light is not emitted from the semiconductor laser element 10.

[0037] FIG. 5B shows the wavelength λ1 that satisfies Equation 1 based on the new position of the region 64 on the second diffraction grating G2 when the position of the aperture 62 in the X-axis direction is changed by the movable portion 162. * , λ2 * , λ3 * , λ4 * 5B schematically illustrates how the collimated beams of wavelengths λ1, λ2, λ3, and λ4 are coaxially superimposed to form the wavelength-combined beam 40. For reference, in FIG. 5B, the collimated beams (diffracted beams) of wavelengths λ1, λ2, λ3, and λ4 that satisfy Equation 1 are shown by dashed lines for the position of region 64 (FIG. 5A) on second diffraction grating G2 before the change. These collimated beams (diffracted beams) of wavelengths λ1, λ2, λ3, and λ4 cannot pass through opening 62 of diaphragm 60 and are blocked by diaphragm 60. Therefore, the light beams of wavelengths λ1, λ2, λ3, and λ4 do not return to laser oscillation region 10X, and laser beams of wavelengths λ1, λ2, λ3, and λ4 are not actually emitted from semiconductor laser device 10.

[0038] As described above, according to the laser device 100 of this embodiment, the laser oscillation wavelength is automatically selected depending on the position of the aperture 62 of the diaphragm 60 in the X-axis direction. Since the position of the optical path of the wavelength-combined beam 40 can be adjusted, the wavelength-combined beam 40 can be swept while remaining parallel to the Z-axis direction.

[0039] At least a portion of the second mirror M2, including the sweepable range of the wavelength-combined beam 40, is a flat mirror 70. The flat mirror 70 is configured to reflect the wavelength-combined beam 40 emitted from the second diffraction grating G2 in a second direction 52 opposite to the first direction 50, and return the beam to the second diffraction grating G2. The second mirror M2 is a partially reflective mirror that transmits a portion of the wavelength-combined beam 40. The wavelength-combined beam 40 that has transmitted through the second mirror M2 is extracted from the laser device 100 and used.

[0040] As described above, the size of the opening 62 defines the size of the region 64. The size of the opening 62, and therefore the size of the region 64, is preferably at least one time and at most two times the beam diameter of each collimated beam 12. The beam diameter of each collimated beam 12 may be equal to or less than the center-to-center distance between the plurality of laser oscillation regions 10X. In one embodiment, the width of each laser oscillation region 10X may be at least 1 μm and at most 200 μm. This width may be 20 to 80% of the center-to-center distance between adjacent laser oscillation regions 10X.

[0041] Each laser oscillation region 10X receives a light ray of a predetermined wavelength included in a plurality of light rays (diffracted beams) formed when the wavelength-combined beam 40, which has passed through the aperture 62 of the diaphragm 60, is sequentially diffracted by the second diffraction grating G2 and the first diffraction grating G1. Each of the plurality of laser oscillation regions 10X oscillates at the peak wavelength of the incident light ray.

[0042] In the laser device 100 of this embodiment, the wavelength-combined beam formed from the collimated beam 12 is also collimated light and is reflected by the flat mirror of the second mirror M2, so the oscillation wavelength of the laser does not change even if the position of the second mirror M2 in the Z-axis direction changes. Therefore, the degree of freedom in the position of the second mirror M2 is improved compared to conventional technologies in which the second mirror is a concave mirror or a lens is placed in front of the second mirror.

[0043] It should be noted that the diaphragm 60 and the second mirror M2 do not need to be separate components placed at positions separated from each other, and the diaphragm 60 and the second mirror M2 may be integrated.

[0044] Second Embodiment Next, another embodiment of the laser device according to the present disclosure will be described with reference to FIG.

[0045] 6, the laser device 200 of this embodiment includes a first mirror M1 and a second mirror M2 that form a resonator, and a semiconductor laser element 10 disposed between the first mirror M1 and the second mirror M2. The laser device 200 also includes a collimator 20 disposed between the semiconductor laser element 10 and the second mirror M2, and first and second diffraction gratings G1, G2 disposed in parallel between the collimator 20 and the second mirror M2. Examples of the configuration of the first mirror M1, the semiconductor laser element 10, the collimator 20, and the first and second diffraction gratings G1, G2 are as described for the laser device 100 of the first embodiment.

[0046] In this embodiment, in order to define the area 64 on the second diffraction grating G2, a second mirror M2 having a new configuration is used instead of the aperture 60 of the laser device 100. This point will be explained below.

[0047] At least a portion of the second mirror M2 in this embodiment, including the reflective region 72 that reflects the wavelength-combined beam 40, is a flat mirror, and has the reflective region 72 that reflects the wavelength-combined beam 40 output from the second diffraction grating G2 in a second direction 52 opposite to the first direction 50 and returns it to the second diffraction grating G2. Specifically, the second mirror M2 in this embodiment can be realized by coating the reflective surface of the second mirror M2 with an anti-reflective film or a light-absorbing member having an opening that defines the position and size of the reflective region 72.

[0048] The size of the reflective region 72 is between one and two times the beam diameter (1 mm to 5 mm) of each collimated beam 12. Compared to a normal mirror, the size of the reflective region 72 is limited in this way, making it possible to control the oscillation wavelength in each of the multiple laser oscillation regions 10X depending on the position of the reflective region 72. Specifically, the reflective region 72 can function similarly to a flat mirror whose size is effectively reduced by the opening 62 of the diaphragm 60 in the first embodiment. In other words, light rays that do not enter the reflective region 72 do not return to each laser oscillation region 10X of the semiconductor laser device 10.

[0049] The laser device 200 in this embodiment includes a support member 160 that supports the second mirror M2. The support member 160 has a movable part 162 that supports the second mirror M2 so that the second mirror M2 can move in a direction intersecting with the first direction 50.

[0050] The laser oscillation regions 10X are incident with light rays included in a plurality of light rays formed when the wavelength-combined beam 40 reflected by the reflecting region 72 of the second mirror M2 is sequentially diffracted by the second diffraction grating G2 and the first diffraction grating G1. Each of the laser oscillation regions 10X oscillates at the peak wavelength of the incident light rays.

[0051] To achieve such a narrow reflection area 72, it is not necessary to adopt the configuration shown in Fig. 6. For example, as shown in Fig. 7, the narrow reflection area 72 can be achieved by adjusting the shape and size of the second mirror M2.

[0052] In the above embodiments, the first diffraction grating G1 and the second diffraction grating G2 are transmissive diffraction gratings, but one or both of the first diffraction grating G1 and the second diffraction grating G2 may be reflective diffraction gratings. Fig. 8 is a schematic diagram showing a modified example in which both the first diffraction grating G1 and the second diffraction grating G2 in the laser device 100 shown in Fig. 1 are replaced with reflective diffraction gratings. Such modifications are also possible in the configuration examples shown in Figs. 6 and 7. One of the first diffraction grating G1 and the second diffraction grating G2 may be transmissive and the other may be reflective.

[0053] In the illustrated example, diffraction is described as occurring at the light-incident surfaces of the first diffraction grating G1 and the second diffraction grating G2, but diffraction may also occur at the back surface of each diffraction grating G1, G2, which is located opposite the light-incident surface, or may occur inside the diffraction grating.

[0054] The laser device according to each of the above embodiments produces a wavelength-combined beam in which laser beams with different wavelengths are coaxially superimposed, thereby achieving a high optical intensity that cannot be achieved with a single-wavelength laser beam. Furthermore, because the reflective areas of the mirrors constituting the external resonator are flat mirrors and utilize the diffraction of the collimated beam, the laser device is less susceptible to misalignment in the direction of propagation of the collimated beam. As a result, the design flexibility regarding the position or dimensions of components in the direction of propagation of the collimated beam is improved. This allows for a more compact device with stable performance, and makes it easier to incorporate additional optical equipment into the device. Furthermore, laser oscillation is possible even if the aperture (FIGS. 5A and 5B) or the second mirror (FIGS. 6 and 7) moves in a direction intersecting the direction of propagation of the wavelength-combined beam, resulting in less susceptibility to misalignment of these elements. [Industrial Applicability]

[0055] The laser device of the present disclosure can be used in industrial fields where a high-power laser light source is required, such as cutting various materials, drilling holes, localized heat treatment, surface treatment, metal welding, and 3D printing.

[0056] The laser device of the present disclosure can be used as an excitation light source for a fiber laser device, or as a laser light source for a direct diode laser device that processes materials by directly irradiating them. [Explanation of symbols]

[0057] 10...Semiconductor laser element, 10F...Light output surface of semiconductor laser element, 10R...Light reflecting surface of semiconductor laser element, 10X...Laser oscillation region, 12...Collimated beam, 20...Collimator, 40...Wavelength combined beam, 50...First direction, 52...Second direction, 60...Aperture, 62...Aperture, 70...Plane mirror, 100...Laser device, 160...Aperture support member, 162...Moving part of aperture, G1...First diffraction grating, G2...Second diffraction grating, M1...First mirror, M2...Second mirror

Claims

1. a first mirror and a second mirror forming a resonator; a semiconductor laser element disposed between the first mirror and the second mirror, the semiconductor laser element including a plurality of laser oscillation regions that oscillate at different wavelengths during operation; a collimator disposed between the semiconductor laser element and the second mirror, the collimator converting the light beams emitted from the plurality of laser oscillation regions into a plurality of collimated beams; first and second diffraction gratings arranged in parallel between the collimator and the second mirror, wherein the first diffraction grating diffracts the plurality of collimated beams in different directions according to wavelengths and causes the beams to be incident on the second diffraction grating, and the second diffraction grating further diffracts the plurality of collimated beams diffracted by the first diffraction grating to form a wavelength-combined beam and emits the wavelength-combined beam in a first direction; a diaphragm disposed between the second diffraction grating and the second mirror, the diaphragm having an aperture for passing the wavelength-combined beam; Equipped with At least a portion of the second mirror is a flat mirror, and reflects the wavelength-combined beam output from the second diffraction grating in a second direction opposite to the first direction, and returns the beam to the second diffraction grating; a support member for supporting the aperture, the support member enabling control of an oscillation wavelength in each of the plurality of laser oscillation regions depending on the position of the aperture; The support member has a movable part that supports the aperture so that it can move in a direction intersecting the first direction, and by moving the position of the aperture, the wavelength-combined beam can be swept in a direction perpendicular to the first direction while remaining directed in the first direction.

2. The laser device according to claim 1 , wherein the size of the aperture is equal to or greater than one time and equal to or less than two times the beam diameter of the plurality of collimated beams.

3. 3. The laser device according to claim 1, wherein the beam diameter of the plurality of collimated beams is equal to or smaller than the center-to-center distance between the plurality of laser oscillation regions.

4. 4. The laser device according to claim 2, wherein the width of each of the plurality of laser oscillation regions is 1 μm or more and 200 μm or less.

5. 5. The laser device according to claim 4, wherein the width of each of the plurality of laser oscillation regions is 20 to 80% of the center-to-center distance of the plurality of laser oscillation regions.

6. the semiconductor laser element is a laser bar having the plurality of laser oscillation regions, The laser bar comprises: a light emitting surface on which one ends of the plurality of laser oscillation regions are aligned; a light reflecting surface on which the other ends of the plurality of laser oscillation regions are aligned; and The laser device according to claim 1 , wherein the light reflecting surface is provided with a reflective film that forms the first mirror, and the light emitting surface is provided with an anti-reflection film.

7. 7. The laser device according to claim 6, wherein said semiconductor laser element has a plurality of ridges or a plurality of stripe electrodes that define said plurality of laser oscillation regions.

8. the plurality of laser oscillation regions receive incident light beams included in a plurality of light beams formed by the wavelength-combined beam passing through the opening of the diaphragm being sequentially diffracted by the second diffraction grating and the first diffraction grating, The laser device according to claim 1 , wherein each of the plurality of laser oscillation regions oscillates at a peak wavelength of the incident light beam.

9. a first mirror and a second mirror forming a resonator; a semiconductor laser element disposed between the first mirror and the second mirror, the semiconductor laser element including a plurality of laser oscillation regions that oscillate at different wavelengths during operation; a collimator disposed between the semiconductor laser element and the second mirror, the collimator converting the light beams emitted from the plurality of laser oscillation regions into a plurality of collimated beams; first and second diffraction gratings arranged in parallel between the collimator and the second mirror, wherein the first diffraction grating diffracts the plurality of collimated beams in different directions according to wavelengths and causes the beams to be incident on the second diffraction grating, and the second diffraction grating further diffracts the plurality of collimated beams diffracted by the first diffraction grating to form a wavelength-combined beam and emits the wavelength-combined beam in a first direction; Equipped with At least a portion of the second mirror is a flat mirror and has a reflective region that reflects the wavelength-combined beam emitted from the second diffraction grating in a second direction opposite to the first direction and returns the beam to the second diffraction grating; The size of the reflection region is equal to or greater than one time and equal to or less than two times the beam diameter of the plurality of collimated beams, and the oscillation wavelength of each of the plurality of laser oscillation regions can be controlled by the position of the reflection region; a support member for supporting the second mirror, the support member having a movable portion for supporting the second mirror so as to be movable in a direction intersecting the first direction;

10. 10. The laser device according to claim 9, wherein the diameters of the plurality of collimated beams are equal to or smaller than the center-to-center distance between the plurality of laser oscillation regions.

11. 11. The laser device according to claim 9, wherein the width of each of the plurality of laser oscillation regions is not less than 1 [mu]m and not more than 200 [mu]m.

12. 12. The laser device according to claim 11, wherein the width of each of the plurality of laser oscillation regions is 20 to 80% of the center-to-center distance of the plurality of laser oscillation regions.

13. the semiconductor laser element is a laser bar having the plurality of laser oscillation regions, The laser bar comprises: a light emitting surface on which one ends of the plurality of laser oscillation regions are aligned; a light reflecting surface on which the other ends of the plurality of laser oscillation regions are aligned; and 13. The laser device according to claim 9, wherein the light reflecting surface is provided with a reflective film that forms the first mirror, and the light emitting surface is provided with an anti-reflection film.

14. 14. The laser device according to claim 13, wherein the semiconductor laser element has a plurality of ridges or a plurality of stripe electrodes that define the plurality of laser oscillation regions.

15. The plurality of laser oscillation regions are formed by the laser beams reflected by the reflective regions of the second mirror. receiving a light beam included in a plurality of light beams formed by the wavelength-combined beam being sequentially diffracted by the second diffraction grating and the first diffraction grating; 15. The laser device according to claim 9, wherein each of the plurality of laser oscillation regions oscillates at a peak wavelength of the incident light beam.

Images