Semiconductor laser device and control method thereof

Abstract

A semiconductor laser device (1) comprises: a plurality of light amplifying units which are controlled by a controller (80) and which each emit light; a diffraction grating (50) on which light from the plurality of light amplifying units is incident; and a revolving mirror that can revolve and is disposed on the light paths between the diffraction grating (50) and the plurality of light amplifying units. The controller (80) revolves the revolving mirror in accordance with the current applied to the plurality of light amplifying units, and the angle of incidence of light with respect to the diffraction grating (50) changes depending on the current applied.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor laser device and a control method for a semiconductor laser device.

Background Art

[0002] Conventionally, processing of various products has been performed using laser light emitted from a semiconductor laser device. In this type of semiconductor laser device, an increase in the output power of the emitted light is required to improve the processing quality.

[0003] In the semiconductor laser device described in Patent Document 1, in order to optimize the synthesis efficiency of a plurality of lights in a diffraction grating, the incident angle of the light with respect to the diffraction grating is set according to the wavelength of the light. However, the wavelength of the light emitted from the semiconductor laser element changes according to the current applied to the semiconductor laser element. Therefore, when the current applied to the semiconductor laser element is changed, the optimal incident angle of the light with respect to the diffraction grating changes. For this reason, when the current applied to the semiconductor laser element is changed, the synthesis efficiency of a plurality of lights in the diffraction grating decreases.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the semiconductor laser device described in Patent Document 1, in order to optimize the synthesis efficiency of a plurality of lights in the diffraction grating, the incident angle of the light with respect to the diffraction grating is set according to the wavelength of the light. However, the wavelength of the light emitted from the semiconductor laser element changes according to the current applied to the semiconductor laser element. Therefore, when the current applied to the semiconductor laser element is changed, the optimal incident angle of the light with respect to the diffraction grating changes. For this reason, when the current applied to the semiconductor laser element is changed, the synthesis efficiency of a plurality of lights in the diffraction grating decreases.

[0006] The present disclosure solves such problems, and an object thereof is to provide a semiconductor laser device and the like that can suppress a decrease in the synthesis efficiency of a plurality of lights in a diffraction grating.

Means for Solving the Problem

[0007] In order to solve the above problems, one aspect of the semiconductor laser device according to the present disclosure is a semiconductor laser device controlled by a controller, including a plurality of optical amplification parts each emitting light, a diffraction grating into which the light from each of the plurality of optical amplification parts is incident, and a rotatable rotation mirror disposed on an optical path between the plurality of optical amplification parts and the diffraction grating. The controller rotates the rotation mirror according to an applied current to the plurality of optical amplification parts, and an incident angle of the light with respect to the diffraction grating changes according to the applied current.

[0008] Also, in order to solve the above problems, one aspect of the control method of the semiconductor laser device according to the present disclosure is that the semiconductor laser device includes a plurality of optical amplification parts each emitting light, a diffraction grating into which the light from each of the plurality of optical amplification parts is incident, and a rotatable rotation mirror disposed on an optical path between the plurality of optical amplification parts and the diffraction grating. The control method of the semiconductor laser device includes a determination step of determining an applied current to the plurality of optical amplification parts, and a rotation step of rotating the rotation mirror according to the applied current. An incident angle of the light with respect to the diffraction grating changes according to the applied current.

Advantages of the Invention

[0009] According to the present disclosure, it is possible to provide a semiconductor laser device or the like that can suppress a decrease in the synthesis efficiency of a plurality of lights in a diffraction grating.

Brief Description of the Drawings

[0010]

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that each of the embodiments described below shows a specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, the arrangement positions and connection forms of the components, etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0012] Also, each figure is a schematic diagram and is not necessarily drawn precisely. Therefore, the scales etc. in each figure do not necessarily match. In each figure, the same reference numerals are given to substantially the same configurations, and overlapping descriptions are omitted or simplified.

[0013] In this specification, the terms "upper" and "lower" do not refer to the upward (vertically upward) and downward (vertically downward) directions in an absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. Also, the terms "upper" and "lower" are applicable not only when two components are arranged with a gap therebetween and there is another component between the two components, but also when the two components are arranged in contact with each other.

[0014] (Embodiment 1) A semiconductor laser device and its control method according to Embodiment 1 will be described.

[0015] [1-1. Overall Configuration] First, the overall configuration of the semiconductor laser device according to this embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic diagram showing the overall configuration of the semiconductor laser device 1 according to this embodiment. Note that in FIG. 1 and each of the figures shown below, an X-axis, a Y-axis, and a Z-axis orthogonal to each other are shown.

[0016] The semiconductor laser device 1 according to this embodiment is a device that synthesizes a plurality of lights by a diffraction grating 50 and emits the synthesized light. As shown in FIG. 1, the semiconductor laser device 1 includes a plurality of laser modules CP1 to CP8, first mirrors MR11 to MR18, a second mirror MR2, a third mirror MR3, a fourth mirror MR4, and a diffraction grating 50. In this embodiment, the semiconductor laser device 1 further includes a controller 80, a power supply 82, driving devices ST3 and ST4, fast-axis collimator lenses FAC1 to FAC8, and heat sinks HS1 and HS2.

[0017] Each of the laser modules CP1 to CP8 is a module including a semiconductor laser element. In this embodiment, each of the laser modules CP1 to CP8 includes a CAN package and a semiconductor laser element. The laser modules CP1 to CP4 are arranged on the heat sink HS1, and the laser modules CP5 to CP8 are arranged on the heat sink HS2. Thereby, the heat generated in the laser modules CP1 to CP8 can be dissipated to the heat sinks HS1 and HS2. The configurations of the heat sinks HS1 and HS2 are not particularly limited, and for example, a heat dissipation plate formed of a plate-shaped metal member or the like may be used.

[0018] The semiconductor laser elements included in each of the laser modules CP1 to CP8 will be described with reference to FIGS. 2 and 3. FIG. 2 is a schematic perspective view showing an example of the configuration of the semiconductor laser element 11 according to this embodiment. FIG. 3 is a schematic diagram showing the fast-axis direction and the slow-axis direction of the light emitted from the semiconductor laser element 11 according to this embodiment.

[0019] The semiconductor laser element 11 is an example of a light amplification unit that emits light. As shown in FIG. 2, it has a substrate 114, an N-type clad layer 112, an active layer 111, a P-type clad layer 113, a contact layer 115, electrodes 116P and 116N, and an insulating layer 120.

[0020] The substrate 114 is a plate-shaped base material with a semiconductor layer laminated on one main surface and an electrode 116N disposed on the other main surface. In the present embodiment, the substrate 114 is an N-type semiconductor substrate. The N-type cladding layer 112 is disposed above the substrate 114 and is an N-type semiconductor layer having a refractive index lower than that of the active layer 111. The active layer 111 is a light-emitting layer disposed above the N-type cladding layer 112. The P-type cladding layer 113 is disposed above the active layer 111 and is a P-type semiconductor layer having a refractive index lower than that of the active layer 111. The contact layer 115 is a P-type semiconductor layer that makes an ohmic contact with the electrode 116P.

[0021] The insulating layer 120 is a dielectric layer that electrically insulates the electrode 116P and the contact layer 115. A slit extending in the Y-axis direction is formed at the center of the insulating layer 120. Inside the slit of the insulating layer 120, the contact layer 115 and the electrode 116P are in contact. Thereby, a current injection region is formed in which current is injected from the electrode 116P into the contact layer 115. In the present embodiment, a current injection region extending in the Y-axis direction is formed. Current is injected into the active layer 111 disposed below the slit of the insulating layer 120. The region of the active layer 111 into which current is injected forms the light-emitting region 117.

[0022] The dimension W1 of the light-emitting region 117 in the Z-axis direction (that is, the direction parallel to the main surface of the active layer 111 and perpendicular to the longitudinal direction of the current injection region) is longer than the dimension W2 of the light-emitting region 117 in the X-axis direction (that is, the stacking direction of the active layer 111). In the semiconductor laser element 11, the Z-axis direction is referred to as the slow axis direction, and the X-axis direction is referred to as the fast axis direction. In FIG. 3, the axis 118a indicates the fast axis, and the axis 118b indicates the slow axis. As shown in FIG. 3, the divergence angle of the light emitted from the light-emitting region 117 in the fast axis direction is larger than the divergence angle in the slow axis direction. For this reason, as shown in FIG. 3, the cross-sectional shape of the light B20 emitted from the light-emitting region 117 is an ellipse.

[0023] One end face of the semiconductor laser element 11 in the Y-axis direction is the front end face 11F, and the other end face is the rear end face 11R. The front end face 11F is an end face with a low light reflectivity, and light is emitted from the light emitting region 117 of the front end face 11F. The reflectivity of the front end face 11F is, for example, 10% or less. A dielectric multilayer film or the like for reducing the reflectivity of the light emitted from the light emitting region 117 may be formed on the front end face 11F. The rear end face 11R is an end face with a higher light reflectivity than the front end face 11F. The reflectivity of the rear end face 11R is, for example, 90% or more. A dielectric multilayer film or the like for increasing the reflectivity of the light emitted from the light emitting region 117 may be formed on the rear end face 11R.

[0024] Each of the semiconductor laser elements 11 included in the laser modules CP1 to CP8 shown in FIG. 1 emits light with different wavelengths. The wavelengths of two adjacent semiconductor laser elements 11 included in the laser modules CP1 to CP8 are different from each other by, for example, about several nm. The wavelength of the light emitted by the semiconductor laser element 11 is set, for example, to be about 390 nm or more and 450 nm or less.

[0025] The semiconductor material for forming each semiconductor layer of the semiconductor laser element 11 is not particularly limited. As each semiconductor material, for example, a nitride-based semiconductor or the like can be used.

[0026] Returning to FIG. 1, the laser modules CP1 to CP8 are arranged linearly side by side in the X-axis direction. The first mirrors MR11 to MR18 are respectively arranged at a distance from the laser modules CP1 to CP8 in the Y-axis direction. Each of the first mirrors MR11 to MR18 is arranged at a position facing the front end face 11F of the semiconductor laser element 11 included in each of the laser modules CP1 to CP8. That is, each of the first mirrors MR11 to MR18 is arranged on the optical axis of the light emitted from the semiconductor laser element 11 included in each of the laser modules CP1 to CP8.

[0027] On the optical axes between the laser modules CP1 to CP8 and the first mirrors MR11 to MR18, fast-axis collimator lenses FAC1 to FAC8 are respectively arranged. Each of the fast-axis collimator lenses FAC1 to FAC8 is an example of a collimator lens that collimates the light emitted from each of the plurality of optical amplification units, and suppresses the divergence in the fast-axis direction of the light. Thereby, the light emitted from the laser modules CP1 to CP8 and transmitted through the fast-axis collimator lenses FAC1 to FAC8 is incident on the first mirrors MR11 to MR18, respectively. Specifically, the fast-axis collimator lenses FAC1 to FAC8 are respectively arranged in the vicinity of the laser modules CP1 to CP8. Thereby, the dimension in the fast-axis direction of the light emitted from the laser modules CP1 to CP8 can be suppressed. For example, a cylindrical lens can be used as the fast-axis collimator lenses FAC1 to FAC8.

[0028] Note that, on the optical axis between the fast-axis collimator lenses FAC1 to FAC8 and the first mirrors MR11 to MR18 or the like, a slow-axis collimator lens, which is another example of a collimator lens that collimates the light emitted from each of the plurality of optical amplification units, may be arranged. The slow-axis collimator lens suppresses the divergence in the slow-axis direction of the light.

[0029] The reflecting surfaces of the first mirrors MR11 to MR18 are flat and are arranged inclined with respect to the optical axis. Thereby, the first mirrors MR11 to MR18 respectively reflect the light from the laser modules CP1 to CP8 toward the second mirror MR2. The first mirrors MR11 to MR14 are arranged shifted from each other in the Y-axis direction in order to suppress blocking the light reflected by the other first mirrors. The first mirrors MR15 to MR18 are also arranged shifted from each other in the Y-axis direction, similarly to the first mirrors MR11 to MR14.

[0030] The first mirrors MR11 to MR14 are arranged in a parabola on a plane where the reflecting surface is parallel to the XY plane. Also, the first mirrors MR15 to MR18 are arranged in a parabola on a plane where the reflecting surface is parallel to the XY plane. Here, the parabola is not limited to a mathematically exact parabola, and positions slightly deviated from the parabola are also included. For example, positions deviated from a mathematically exact parabola by about the dimensions of the reflecting surface of each first mirror are included in the parabola.

[0031] The tilt angles of the reflecting surfaces of the first mirrors MR11 to MR14 are different from each other, and the tilt angles of the reflecting surfaces of the first mirrors MR15 to MR18 are different from each other.

[0032] The second mirror MR2 is a mirror that receives the light reflected by the first mirrors MR11 to MR18 and reflects it toward the third mirror MR3. In the present embodiment, the position of the second mirror MR2 in the X-axis direction is between the position of the laser module CP4 in the X-axis direction and the position of the laser module CP5 in the X-axis direction. Hereinafter, the configuration of the second mirror MR2 will be described with reference to FIG. 4. FIG. 4 is a schematic diagram showing the configuration of the second mirror MR2 according to the present embodiment. As shown in FIG. 4, the second mirror MR2 has the same number of mirrors MR21 to MR28 as the laser modules CP1 to CP8. The light reflected by the first mirrors MR11 to MR18 shown in FIG. 1 is incident on the mirrors MR21 to MR28 of the second mirror MR2 shown in FIG. 4, respectively. The mirrors MR21 to MR28 of the second mirror MR2 are each a plane mirror and reflect the incident light toward the third mirror MR3. The tilt angles of the reflecting surfaces of the mirrors MR21 to MR24 of the second mirror MR2 are different from each other, and the tilt angles of the reflecting surfaces of the mirrors MR25 to MR28 of the second mirror MR2 are different from each other.

[0033] Returning to FIG. 1, the third mirror MR3 is a mirror onto which the light reflected by the mirrors MR21 to MR28 of the second mirror MR2 is incident and which reflects the light toward the fourth mirror MR4. The third mirror MR3 is, for example, a plane mirror. The third mirror MR3 is held by the driving device ST3. The driving device ST3 is controlled by the controller 80 to rotate the third mirror MR3. When the third mirror MR3 rotates, the incident angle and the reflection angle of the light on the reflecting surface of the third mirror MR3 change. Accordingly, the incident angle of the light on the fourth mirror MR4 also changes.

[0034] The fourth mirror MR4 is a mirror onto which the light reflected by the third mirror MR3 is incident and which reflects the light toward the diffraction grating 50. The plurality of lights reflected by the fourth mirror MR4 are incident on the diffraction grating 50 at different incident angles. The fourth mirror MR4 is, for example, a plane mirror. The fourth mirror MR4 is held by the driving device ST4. The driving device ST4 is controlled by the controller 80 to rotate the fourth mirror MR4. When the fourth mirror MR4 rotates, the incident angle and the reflection angle of the light on the reflecting surface of the fourth mirror MR4 change. Accordingly, the incident angle of the light on the diffraction grating 50 changes.

[0035] As described above, the third mirror MR3 is an example of a rotatable first rotation mirror disposed on the optical path between the plurality of semiconductor laser elements 11, which are a plurality of optical amplification units, and the diffraction grating 50. The fourth mirror MR4 is an example of a rotatable second rotation mirror disposed on the optical path between the plurality of semiconductor laser elements 11, which are a plurality of optical amplification units, and the diffraction grating 50.

[0036] The diffraction grating 50 is an optical element into which light from each of the plurality of optical amplification sections is incident. The light from each of the plurality of optical amplification sections is incident on substantially the same position of the diffraction grating 50 and is diffracted. The diffraction grating 50 diffracts the incident light according to the wavelength. Therefore, by appropriately determining the incident angle according to the wavelength of each light, the emission angle (i.e., the diffraction angle) of each light with respect to the diffraction grating 50 can be made substantially the same. That is, the diffraction grating 50 can combine a plurality of lights having different wavelengths from each other. That is, the optical axes of the lights emitted from the diffraction grating 50 are aligned with each other. Thereby, the emitted light L10 is generated. In the present embodiment, the plurality of lights are incident on the diffraction grating 50 such that the grating arrangement direction in the diffraction grating 50 coincides with the fast axis direction of the plurality of lights. Further, the plurality of lights are arranged in the fast axis direction. Thereby, in the diffraction grating 50, the beam diameter of the plurality of lights to be combined in the grating arrangement direction can be reduced. Here, in the diffraction grating 50, the smaller the diameter of the light in the grating arrangement direction, the higher the combining efficiency can be. Therefore, by making the grating arrangement direction in the diffraction grating 50 coincide with the fast axis direction in which the diameter of the light can be reduced, the combining efficiency of the plurality of lights can be increased.

[0037] In the present embodiment, a part of the light incident on the diffraction grating 50 is diffracted to become the emitted light L10. Further, another part of the light incident on the diffraction grating 50 is reflected and returns to the semiconductor laser element 11 via the fourth mirror MR4, the third mirror MR3, the second mirror MR2, and the first mirrors MR11 to MR18. That is, the diffraction grating 50 and the rear end face 11R of the semiconductor laser element 11 form an external resonator, and laser light is generated by the oscillation of light in the external resonator. The wavelength of the light amplified by each semiconductor laser element 11 is determined by the incident angle of the light with respect to the diffraction grating 50 and the amplification gain characteristics with respect to the wavelength in each semiconductor laser element 11. Therefore, in each semiconductor laser element 11, laser light having different wavelengths from each other is generated. In this way, the light generated by each semiconductor laser element 11 is combined by the diffraction grating 50 and output as the emitted light L10 including laser light of a plurality of wavelengths.

[0038] The power supply 82 is a DC power supply that supplies power to each of the laser modules CP1 to CP8. Specifically, the power supply 82 applies a DC current to the semiconductor laser elements 11 included in each of the laser modules CP1 to CP8. The eight semiconductor laser elements 11 included in the laser modules CP1 to CP8 are, for example, electrically connected in series, and the same current is applied to the eight semiconductor laser elements 11. The current applied from the power supply 82 to the semiconductor laser element 11 is controlled by the controller 80.

[0039] The controller 80 is a device that controls the semiconductor laser device 1. The controller 80 controls the power supply 82 and the driving devices ST3 and ST4. Specifically, the controller 80 controls the current applied to the semiconductor laser element 11, which is the optical amplification section, by controlling the power supply 82. In addition, the controller 80 controls the driving devices ST3 and ST4 to control the rotation angles (i.e., the angles with respect to the optical axis) of the third mirror MR3 and the fourth mirror MR4, which are rotating mirrors. Note that the controller 80 rotating the third mirror MR3 and the fourth mirror MR4 by controlling the driving devices ST3 and ST4 is also expressed as the controller 80 rotating the third mirror MR3 and the fourth mirror MR4. The controller 80 rotates the third mirror MR3 and the fourth mirror MR4, which are rotating mirrors, according to the current applied to the plurality of semiconductor laser elements 11, which are the plurality of optical amplification sections. Details of the control of the semiconductor laser device 1 by the controller 80 will be described later. The controller 80 can be realized, for example, by a microcomputer. The microcomputer is a one-chip semiconductor integrated circuit having a memory such as a ROM and a RAM in which a program is stored, a processor (CPU) that executes the program, a timer, and an input / output circuit including an A / D converter and a D / A converter. Note that the controller 80 may be realized using a personal computer, an electric circuit, etc. other than the microcomputer.

[0040] [1-2. Relationship between Applied Current and Emitted Light] Next, the relationship between the applied current to the plurality of semiconductor laser elements 11 according to the present embodiment and the emitted light L10 will be described with reference to FIG. 5. FIG. 5 is a graph showing the relationship between the rotation angle of the fourth mirror MR4 of the semiconductor laser device 1 according to the present embodiment and the optical output. In FIG. 5, graphs for cases where the applied current to the semiconductor laser element 11 is 20 A, 30 A, 40 A, and 60 A are shown. The horizontal axis of the graph in FIG. 5 indicates the rotation angle of the fourth mirror MR4, and the vertical axis indicates the optical output. Note that the rotation angle of the fourth mirror MR4 on the horizontal axis is set to zero at the angle at which the optical output is maximized when the applied current is 60 A.

[0041] As shown in FIG. 5, the rotation angle of the fourth mirror MR4 at which the optical output is maximized changes according to the applied current. This is because as the applied current increases, the temperature of the semiconductor laser element 11 rises, causing the wavelength of the light emitted from the semiconductor laser element 11, that is, the wavelength of ASE (Amplified Spontaneous Emission), to shift to the longer wavelength side. That is, the optimum values of the incident angles of the plurality of lights with respect to the diffraction grating 50 change according to the wavelengths of the plurality of lights from the plurality of semiconductor laser elements 11. Here, the optimum value of the incident angle is the incident angle that maximizes the combined efficiency of the plurality of lights in the diffraction grating 50. In the example shown in FIG. 5, as the wavelengths of the plurality of lights become longer, the rotation angle of the fourth mirror MR4 at which the optical output is maximized becomes smaller (see the wavelength axis shown below the horizontal axis in FIG. 5).

[0042] The controller 80 according to the present embodiment rotates the third mirror MR3 and the fourth mirror MR4, which are rotation mirrors, according to the applied current. For example, the controller 80 has a table showing the relationship between the applied current and the angles of the respective rotation mirrors at which the optical output is maximized, and controls the angles of the respective rotation mirrors according to the applied current based on the table.

[0043] As a result, the incident angle of light on the diffraction grating 50 changes according to the applied current. Therefore, even when the applied current changes, it is possible to suppress a decrease in the synthesis efficiency of a plurality of lights in the diffraction grating 50. More specifically, the incident angle of light on the diffraction grating 50 increases as the applied current increases. Thus, in the present embodiment, in accordance with an increase in the wavelength of light from the semiconductor laser element 11 accompanying an increase in the applied current, the incident angle of light on the diffraction grating 50 increases. For this reason, it is possible to suppress a decrease in the synthesis efficiency of a plurality of lights in the diffraction grating 50 accompanying an increase in the wavelength of light.

[0044] Also, in the present embodiment, the third mirror MR3 and the fourth mirror MR4, which are rotating mirrors, change the incident angle of light so that the diffraction angle of light with respect to the diffraction grating 50 is maintained. As a result, even when the wavelength of light changes due to a change in the applied current, since the diffraction angle is maintained constant, it is possible to suppress a decrease in the synthesis efficiency of a plurality of lights in the diffraction grating 50.

[0045] Such an effect of the semiconductor laser device 1 according to the present embodiment will be described with reference to FIG. 6. FIG. 6 is a graph showing the relationship between the applied current to the plurality of optical amplification units of the semiconductor laser device 1 according to the present embodiment and the optical output. FIG. 6 also shows the relationship between the applied current and the optical output of a semiconductor laser device of a comparative example. The semiconductor laser device of the comparative example has the same configuration as the semiconductor laser device 1 according to the present embodiment, except that the rotation angles of the third mirror MR3 and the fourth mirror MR4 are fixed at an angle at which the optical output is maximized when the applied current is 60 A.

[0046] In the semiconductor laser device of the comparative example, since the angle of the fourth mirror MR4 is fixed, when the applied current is other than 60 A, the synthesis efficiency of a plurality of lights in the diffraction grating 50 decreases, and the maximum light output shown in FIG. 5 cannot be obtained. On the other hand, in the semiconductor laser device 1 according to the present embodiment, by rotating the fourth mirror MR4 according to the applied current, a decrease in the synthesis efficiency of a plurality of lights in the diffraction grating 50 can be suppressed. For this reason, as shown in FIG. 6, the maximum light output shown in FIG. 5 can be obtained at all applied currents.

[0047] Also, as shown in FIG. 6, in the semiconductor laser device 1 according to the present embodiment, for example, a light output of about 6 W can be obtained with an applied current of about 20 A, but in the semiconductor laser device of the comparative example, an applied current of about 30 A is required to obtain a light output of about 6 W. Thus, in the present embodiment, since a decrease in the synthesis efficiency in the diffraction grating 50 can be suppressed, power consumption can be suppressed.

[0048] [1-3. Control Method] Next, a control method of the semiconductor laser device 1 according to the present embodiment will be described with reference to FIG. 7. FIG. 7 is a flowchart showing the control method of the semiconductor laser device 1 according to the present embodiment.

[0049] As shown in FIG. 7, first, the controller 80 determines an applied current to the semiconductor laser element 11 which is a plurality of amplification units (S10). The controller 80 determines the applied current based on, for example, a signal input from the outside by a user or the like.

[0050] Subsequently, the controller 80 determines the angles of the respective rotation mirrors based on the applied current determined in step S10 (S20). More specifically, the controller 80 determines the angles of the respective rotation mirrors (the third mirror MR3, the fourth mirror MR4) so that the light output is maximized at the applied current determined in step S10, based on the relationship between the applied current and the angles of the respective rotation mirrors that maximize the light output.

[0051] Subsequently, the controller 80 rotates each rotation mirror so that the angle of each rotation mirror determined in step S20 matches the angle of each rotation mirror (S30). More specifically, the controller 80 controls the drive device ST3 to rotate the third mirror MR3 so that the angle of the third mirror MR3 matches the angle of the third mirror MR3 determined in step S20. Further, the controller 80 controls the drive device ST4 to rotate the fourth mirror MR4 so that the angle of the fourth mirror MR4 matches the angle of the fourth mirror MR4 determined in step S20. As a result, the incident angle of light on the diffraction grating 50 changes according to the applied current.

[0052] Subsequently, the controller 80 applies current to a plurality of semiconductor laser elements 11 which are a plurality of optical amplification units (S40). More specifically, the controller 80 controls the power supply 82 to apply the applied current determined in step S10 to the plurality of semiconductor laser elements 11.

[0053] As described above, the semiconductor laser device 1 according to the present embodiment can be controlled so as to suppress a decrease in the synthesis efficiency in the diffraction grating 50 according to the applied current.

[0054] (Embodiment 2) A semiconductor laser device and its control method according to Embodiment 2 will be described. The semiconductor laser device according to the present embodiment is different from the semiconductor laser device 1 according to Embodiment 1 in that it includes a partial reflection mirror that functions as an output coupler. Hereinafter, the semiconductor laser device and its control method according to the present embodiment will be described with reference to FIG. 8, centering on the differences from Embodiment 1.

[0055] FIG. 8 is a schematic diagram showing the overall configuration of the semiconductor laser device 101 according to the present embodiment. As shown in FIG. 8, the semiconductor laser device 101 according to the present embodiment includes the same components as the semiconductor laser device 1 according to Embodiment 1 and a partial reflection mirror 60.

[0056] The partial reflection mirror 60 is a mirror that transmits a part of the light emitted from the diffraction grating 50 and reflects the other part. The partial reflection mirror 60 forms an external resonator with the rear end face 11R of the semiconductor laser element 11 included in each of the laser modules CP1 to CP8 of the semiconductor laser device 101 and functions as an output coupler. The partial reflection mirror 60 is, for example, a plane mirror. Note that the partial reflection mirror 60 may be a concave mirror.

[0057] In the semiconductor laser device 101 according to the present embodiment, the same effects as those of the semiconductor laser device according to Embodiment 1 are also achieved. 1 Further, in the present embodiment, since the partial reflection mirror 60 that functions as an output coupler is provided, the degree of freedom in designing the reflectivity, curvature, etc. of the output coupler can be increased as compared with the case where the diffraction grating 50 is used as the output coupler.

[0058] (Embodiment 3) A semiconductor laser device and a control method thereof according to Embodiment 3 will be described. The semiconductor laser device according to the present embodiment is different from the semiconductor laser device 101 according to Embodiment 2 in that it includes a coupling optical system. Hereinafter, the semiconductor laser device and the control method thereof according to the present embodiment will be described with reference to FIG. 9, centering on the differences from Embodiment 2.

[0059] FIG. 9 is a schematic diagram showing the overall configuration of the semiconductor laser device 201 according to the present embodiment. As shown in FIG. 9, the semiconductor laser device 201 according to the present embodiment includes the same components as the semiconductor laser device 101 according to Embodiment 2 and a coupling optical system 70.

[0060] The coupling optical system 70 is an optical system that superimposes the light emitted from each of the plurality of semiconductor laser elements 11, which are a plurality of optical amplification units, with the diffraction grating 50. The coupling optical system 70 is disposed on the optical path between the plurality of optical amplification units and the diffraction grating 50. In the present embodiment, the coupling optical system 70 is a cylindrical lens and is disposed on the optical path between the fourth mirror MR4 and the diffraction grating 50.

[0061] In the semiconductor laser device 201 according to the present embodiment, the same effects as those of the semiconductor laser device 101 according to the second embodiment are also achieved. Further, in the present embodiment, by providing the coupling optical system 70, the degree of freedom in design such as the configuration of each mirror and the optical path length between the diffraction grating 50 and the semiconductor laser element 11 can be increased.

[0062] (Embodiment 4) A semiconductor laser device and a control method thereof according to Embodiment 4 will be described. The semiconductor laser device according to the present embodiment is different from the semiconductor laser device 1 according to Embodiment 1 in that it includes a semiconductor laser array as an optical amplification unit. Hereinafter, the semiconductor laser device 301 and the control method thereof according to the present embodiment will be described with reference to FIG. 10, focusing on the differences from Embodiment 1.

[0063] FIG. 10 is a schematic diagram showing the overall configuration of the semiconductor laser device 301 according to the present embodiment. As shown in FIG. 10, the semiconductor laser device 301 according to the present embodiment includes laser units LU1 to LU8, first mirrors MR11 to MR18, a second mirror MR2, a third mirror MR3, a fourth mirror MR4, and a diffraction grating 50. In the present embodiment, the semiconductor laser device 301 further includes a controller 80, a power supply 82, driving devices ST3 and ST4, and heat sinks HS1 and HS2.

[0064] The laser units LU1 to LU8 according to the present embodiment will be described with reference to FIG. 11. FIG. 11 is a schematic diagram showing the configuration of the laser unit LU1 according to the present embodiment. As shown in FIG. 11, the laser unit LU1 includes a semiconductor laser array 311, a fast-axis collimator lens FAC, a 90° image rotation optical system BT, a heat dissipation block BL, and a slow-axis collimator lens SAC.

[0065] The semiconductor laser array 311 is a semiconductor light-emitting device having a plurality of optical amplification sections. The configuration of the semiconductor laser array 311 will be described with reference to FIG. 12. FIG. 12 is a schematic perspective view showing an example of the configuration of the semiconductor laser array 311 according to the present embodiment. As shown in FIG. 12, the semiconductor laser array 311 is an element in which a plurality of semiconductor laser elements 11 are arranged in an array. Each of the plurality of semiconductor laser elements 11 has the same configuration as the semiconductor laser element 11 according to Embodiment 1. The semiconductor laser array 311 has a plurality of light-emitting regions 117 arranged in the slow-axis direction. In the present embodiment, the plurality of semiconductor laser elements 11 are arranged on a common substrate 320. In FIG. 12, an example in which the semiconductor laser array 311 has four semiconductor laser elements 11 is shown, but the number of semiconductor laser elements 11 included in the semiconductor laser array 311 is not limited to four. The number of semiconductor laser elements 11 included in the semiconductor laser array 311 may be two or more. Also, the semiconductor laser array 311 may have a plurality of semiconductor laser elements 11 integrally formed, or may be separated from each other.

[0066] Returning to FIG. 11, the fast-axis collimator lens FAC is an example of a lens that collimates the light emitted from the optical amplification section, and suppresses the divergence of the light in the fast-axis direction. In the present embodiment, the divergence of the light emitted from the semiconductor laser element 11, which is the optical amplification section, in the fast-axis direction is suppressed. As the fast-axis collimator lens FAC, for example, a cylindrical lens can be used.

[0067] The 90° image rotation optical system BT is disposed on the optical path between the fast-axis collimator lens FAC and the diffraction grating 50, and is an optical system that exchanges the fast-axis direction and the slow-axis direction of the light from the fast-axis collimator lens FAC. The 90° image rotation optical system BT exchanges the fast-axis direction and the slow-axis direction of the light by rotating the image of the incident light by 90° about the optical axis. The semiconductor laser device 301 according to the present embodiment includes the 90° image rotation optical system BT, and thus can convert a plurality of lights arranged in the slow-axis direction into a plurality of lights arranged in the fast-axis direction. Thereby, a plurality of lights can be arranged in the fast-axis direction. Therefore, the grating arrangement direction of the diffraction grating 50 can be made to coincide with the arrangement direction of the plurality of lights and the fast-axis direction of the light. Thereby, as described in Embodiment 1, the synthesis efficiency of the plurality of lights in the diffraction grating 50 can be increased.

[0068] The slow-axis collimator lens SAC is an example of a lens that collimates the light emitted from the optical amplification section, and suppresses the divergence in the slow-axis direction of the light. In the present embodiment, the divergence in the slow-axis direction of the light emitted from the 90° image rotation optical system BT is suppressed. As the slow-axis collimator lens SAC, for example, a cylindrical lens can be used.

[0069] The heat dissipation block BL is a metal block on which the semiconductor laser array 311 is disposed, and dissipates the heat generated by the semiconductor laser array 311. The heat dissipation block BL is formed of a metal having a high thermal conductivity such as copper, for example.

[0070] The laser units LU2 to LU8 shown in FIG. 10 have the same configuration as the laser unit LU1 shown in FIG. 11. Further, the laser units LU1 to LU4 are disposed on the heat sink HS1, and the laser units LU5 to LU8 are disposed on the heat sink HS2.

[0071] A current is applied from the power supply 82 to the semiconductor laser arrays 311 included in each of the laser units LU1 to LU8 in the same manner as the semiconductor laser elements 11 included in the laser modules CP1 to CP8 according to Embodiment 1.

[0072] By having the above-described configuration, the semiconductor laser device 301 according to the present embodiment exhibits the same effects as the semiconductor laser device 1 according to the first embodiment. Further, the semiconductor laser device 301 according to the present embodiment includes a plurality of semiconductor laser arrays 311, and a plurality of semiconductor laser elements 11 included in the semiconductor laser arrays 311 are used as a plurality of optical amplification units. Therefore, the optical amplification units can be arranged at a high density. Accordingly, in the semiconductor laser device 301, miniaturization and high output are possible.

[0073] (Embodiment 5) A semiconductor laser device and its control method according to Embodiment 5 will be described. The semiconductor laser device according to the present embodiment differs from the semiconductor laser device 301 according to Embodiment 4 in that it includes a partial reflection mirror that functions as an output coupler. Hereinafter, the semiconductor laser device and its control method according to the present embodiment will be described with reference to FIG. 13, focusing on the differences from Embodiment 4.

[0074] FIG. 13 is a schematic diagram showing the overall configuration of the semiconductor laser device 401 according to the present embodiment. As shown in FIG. 13, the semiconductor laser device 401 according to the present embodiment includes the same components as the semiconductor laser device 301 according to Embodiment 4 and a partial reflection mirror 60.

[0075] Similar to the partial reflection mirror 60 according to Embodiment 2, the partial reflection mirror 60 is a mirror that transmits a part of the light emitted from the diffraction grating 50 and reflects the other part. The partial reflection mirror 60 forms an external resonator with the rear end face 11R of each semiconductor laser element 11 included in each of the laser units LU1 to LU8 of the semiconductor laser device 401 and functions as an output coupler.

[0076] In the semiconductor laser device 401 according to the present embodiment, the same effects as those of the semiconductor laser device 301 according to the fourth embodiment are also achieved. Further, in the present embodiment, since the partial reflection mirror 60 that functions as an output coupler is provided, the degree of freedom in designing the reflectivity, curvature, etc. of the output coupler can be increased as compared with the case where the diffraction grating 50 is used as the output coupler.

[0077] (Embodiment 6) The semiconductor laser device and its control method according to the sixth embodiment will be described. The semiconductor laser device according to the present embodiment is different from the semiconductor laser device 401 according to the fifth embodiment in that it includes a coupling optical system. Hereinafter, the semiconductor laser device and its control method according to the present embodiment will be described with reference to FIG. 14, centering on the differences from the fifth embodiment.

[0078] FIG. 14 is a schematic diagram showing the overall configuration of the semiconductor laser device 501 according to the present embodiment. As shown in FIG. 14, the semiconductor laser device 501 according to the present embodiment includes the same components as the semiconductor laser device 401 according to the fifth embodiment and a coupling optical system 70.

[0079] The coupling optical system 70 is an optical system that superimposes the light emitted from each of the plurality of semiconductor laser elements 11, which are a plurality of optical amplification units, by the diffraction grating 50, in the same manner as the coupling optical system 70 according to the third embodiment. The coupling optical system 70 is disposed on the optical path between the plurality of optical amplification units and the diffraction grating 50. In the present embodiment, the coupling optical system 70 is a cylindrical lens and is disposed on the optical path between the fourth mirror MR4 and the diffraction grating 50.

[0080] In the semiconductor laser device 501 according to the present embodiment, the same effects as those of the semiconductor laser device 401 according to the fifth embodiment are also achieved. Further, in the present embodiment, by providing the coupling optical system 70, the degree of freedom in designing the configuration of each mirror, the optical path length between the diffraction grating 50 and the semiconductor laser array 311, etc. can be increased.

[0081] (Embodiment 7) A semiconductor laser device and a control method thereof according to Embodiment 7 will be described. The semiconductor laser device according to the present embodiment is different from the semiconductor laser device 501 according to Embodiment 6 mainly in that it includes a single semiconductor laser array. Hereinafter, the semiconductor laser device and the control method thereof according to the present embodiment will be described with reference to FIG. 15, centering on the differences from Embodiment 6.

[0082] FIG. 15 is a schematic diagram showing the overall configuration of the semiconductor laser device 601 according to the present embodiment. As shown in FIG. 15, the semiconductor laser device 601 according to the present embodiment includes a single laser unit LU1, a mirror MR5, a third mirror MR3, a fourth mirror MR4, and a diffraction grating 50. In the present embodiment, the semiconductor laser device 601 includes a controller 80, a power supply 82, driving devices ST3 and ST4, a partial reflection mirror 60, and a coupling optical system 70.

[0083] The laser unit LU1 has the same configuration as the laser unit LU1 according to Embodiments 4 to 6. A current is applied to the laser unit LU1 from the power supply 82.

[0084] The mirror MR5 is a mirror having the same configuration as each of the first mirrors MR11 to MR18 according to Embodiments 1 to 6. The mirror MR5 receives a plurality of lights emitted from the laser unit LU1 and reflects them toward the third mirror MR3. The mirror MR5 is used to reduce the space in which the semiconductor laser device 601 is disposed. That is, the semiconductor laser device 601 can effectively utilize the space by including the mirror MR5. Note that the semiconductor laser device 601 may not include the mirror MR5.

[0085] The other components of the semiconductor laser device 601 according to the present embodiment have the same configuration as the components of the semiconductor laser device 501 according to Embodiment 6.

[0086] Also in the semiconductor laser device 601 according to the present embodiment, the same effects as those of the semiconductor laser device 501 according to Embodiment 6 are achieved.

[0087] (Embodiment 8) A semiconductor laser device and a control method thereof according to Embodiment 8 will be described. The semiconductor laser device according to the present embodiment is different from the semiconductor laser device 501 according to Embodiment 6 in that the positions where a plurality of lights in the diffraction grating 50 are superimposed can be changed. Hereinafter, the semiconductor laser device and the control method thereof according to the present embodiment will be described with reference to FIG. 16, centering on the differences from Embodiment 6.

[0088] FIG. 16 is a schematic diagram showing the overall configuration of the semiconductor laser device 701 according to the present embodiment. As shown in FIG. 16, the semiconductor laser device 701 according to the present embodiment is different from the semiconductor laser device 501 according to Embodiment 6 in the configuration of the driving devices ST73 and ST74.

[0089] The driving device ST73 is controlled by the controller 80 to rotate the third mirror MR3 and move the position of the third mirror MR3. In the present embodiment, the driving device ST73 moves the position of the third mirror MR3 in the optical axis direction.

[0090] The driving device ST74 is controlled by the controller 80 to rotate the fourth mirror MR4 and move the position of the fourth mirror MR4. In the present embodiment, the driving device ST74 moves the position of the fourth mirror MR4 in the optical axis direction.

[0091] In this way, the controller 80 according to the present embodiment moves the positions of the third mirror MR3 and the fourth mirror MR4, which are rotating mirrors, by controlling the driving devices ST73 and ST74. Note that the controller 80 moves the positions of the third mirror MR3 and the fourth mirror MR4 by controlling the driving devices ST 73 and ST 74 is also expressed as the controller 80 moving the positions of the third mirror MR3 and the fourth mirror MR4 by controlling the driving devices ST73 and ST74.

[0092] In this embodiment, by moving the positions of the third mirror MR3 and the fourth mirror MR4, the position where a plurality of lights reflected by the fourth mirror MR4 are superimposed on the diffraction grating 50 can be moved. In this embodiment, the positions of both the third mirror MR3 and the fourth mirror MR4 are movable, but the position of only one of them may be movable.

[0093] As described above, in this embodiment, the controller 80 moves the position of the rotating mirror, and the position where the lights emitted from each of the plurality of optical amplification units are superimposed on the diffraction grating 50 is moved along with the movement of the position of the rotating mirror. Since a high heat load is applied to the position where the plurality of lights of the diffraction grating 50 according to this embodiment are superimposed, damage is likely to occur. However, in this embodiment, since the position where the plurality of lights are superimposed can be moved, it is possible to suppress a high heat load from being continuously applied to a specific position of the diffraction grating 50. Therefore, damage to the diffraction grating 50 can be reduced.

[0094] (Modification example, etc.) As described above, the semiconductor laser device and its control method according to the present disclosure have been described based on each embodiment, but the present disclosure is not limited to the above-described embodiments.

[0095] For example, in each of the above embodiments, the semiconductor laser device includes the controller 80, but the semiconductor laser device may not include the controller 80. In other words, the controller 80 may control the semiconductor laser device from outside the semiconductor laser device.

[0096] Also, in each of the above embodiments, both the third mirror MR3 and the fourth mirror MR4 rotate, but only one of them may rotate. Also, the first mirrors MR11 to MR18, the mirrors MR21 to MR28 of the second mirror MR2, the mirror MR5, etc. may rotate.

[0097] Also, in each of the above embodiments, a transmission-type diffraction grating is used as the diffraction grating 50, but a reflection-type diffraction grating may be used as the diffraction grating 50.

[0098] In addition, forms obtained by applying various modifications that occur to those skilled in the art to each of the above embodiments, and forms realized by arbitrarily combining the components and functions in each of the above embodiments without departing from the spirit of the present disclosure are also included in the present disclosure.

Industrial Applicability

[0099] The semiconductor laser device of the present disclosure can be applied, for example, as a high-output and high-efficiency light source to a light source such as a laser processing machine.

Explanation of Signs

[0100] 1, 101, 201, 301, 401, 501, 601, 701 Semiconductor laser device 11 Semiconductor laser element 11F Front end face 11R Rear end face 50 Diffraction grating 60 Partial reflection mirror 70 Coupling optical system 80 Controller 82 Power supply 111 Active layer 112 N-type clad layer 113 P-type clad layer 114 Substrate 115 Contact layer 116N, 116P Electrodes 117 Light-emitting region 118a, 118b Axes 120 Insulating layer 311 Semiconductor laser array 320 Common substrate B20 Light BL Heat sink BT 90° image rotation optical system CP1, CP2, CP3, CP4, CP5, CP6, CP7, CP8 Laser module FAC, FAC1, FAC2, FAC3, FAC4, FAC5, FAC6, FAC7, FAC8 Fast-axis collimator lens HS1, HS2 Heat sink L10 Output light LU1, LU2, LU3, LU4, LU5, LU6, LU7, LU8 Laser units MR11, MR12, MR13, MR14, MR15, MR16, MR17, MR18 First mirrors MR2 Second mirror MR5, MR21, MR22, MR23, MR24, MR25, MR26, MR27, MR28 Mirrors MR3 Third mirror MR4 Fourth mirror SAC Slow-axis collimator lens ST3, ST4, ST73, ST74 Driving devices

Claims

1. A semiconductor laser device controlled by a controller, comprising: a plurality of optical amplification sections each emitting light; a diffraction grating onto which the light from each of the plurality of optical amplification sections is incident; a rotatable rotation mirror disposed on the optical path between the plurality of optical amplification sections and the diffraction grating, wherein the controller rotates the rotation mirror in response to an applied current to the plurality of optical amplification sections, and an incident angle of the light with respect to the diffraction grating changes in response to the applied current semiconductor laser device.

2. The incident angle with respect to the diffraction grating increases as the applied current increases The semiconductor laser device according to claim 1.

3. The rotation mirror changes the incident angle so that a diffraction angle of the light with respect to the diffraction grating is maintained The semiconductor laser device according to claim 1 or 2.

4. The controller moves the position of the rotation mirror, and a position where the light emitted from each of the plurality of optical amplification sections is superimposed on the diffraction grating is moved as the position of the rotation mirror is moved The semiconductor laser device according to any one of claims 1 to 3.

5. A coupling optical system for superimposing the light emitted from each of the plurality of optical amplification sections on the diffraction grating, wherein the coupling optical system is disposed on the optical path between the plurality of optical amplification sections and the diffraction grating The semiconductor laser device according to any one of claims 1 to 4.

6. The semiconductor laser device includes one or more semiconductor laser arrays, and the one or more semiconductor laser arrays have the plurality of optical amplification sections The semiconductor laser device according to any one of claims 1 to 5.

7. A collimator lens for collimating the light emitted from each of the plurality of optical amplification sections is provided The semiconductor laser device according to any one of claims 1 to 6.

8. A 90° image rotation optical system is provided which is disposed on the optical path between the collimator lens and the diffraction grating and exchanges the fast axis direction and the slow axis direction of the light The semiconductor laser device according to claim 7.

9. A partial reflection mirror is provided which transmits a part of the light emitted from the diffraction grating and reflects the other part The semiconductor laser device according to any one of claims 1 to 8.

10. A control method for a semiconductor laser device, comprising: the semiconductor laser device includes a plurality of optical amplification sections each emitting light; a diffraction grating onto which the light from each of the plurality of optical amplification sections is incident; A rotatable rotation mirror disposed on the optical path between the plurality of optical amplification units and the diffraction grating is provided. The control method of the semiconductor laser device is as follows. A determination step of determining an applied current to the plurality of optical amplification units. A rotation step of rotating the rotation mirror according to the applied current. The incident angle of the light with respect to the diffraction grating changes according to the applied current. A control method of a semiconductor laser device.

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