Laser device

Abstract

Provided is a laser device with which the occurrence of parasitic oscillation can be suppressed. A laser device 1 comprises: a light generation unit 10 that supplies excitation light Q1 from an excitation light source 12 to an inner cladding 152 of an amplification optical fiber 15 to generate seed signal light S1; and an optical amplification unit 20 that supplies the seed signal light S1 to a core 211 of an amplification optical fiber 21 and supplies excitation light Q2 from an excitation light source 22 to an inner cladding 212, thereby amplifying the seed signal light S1 to generate amplified signal light S2. The laser device 1 includes: a photodetector 71 capable of detecting a light quantity PMO of the seed signal light S1; a photodetector 72 capable of detecting a light quantity PPA of the amplified signal light S2; and a control unit 40 that controls the excitation light sources 12, 22 so that a ratio PMO / PPA is equal to or greater than a threshold α when the amplified signal light S2 is being emitted from a light emission unit 30.

Description

laser device

[0001] The present invention relates to a laser device.

[0002] High-power fiber laser devices are increasingly being used in fields such as laser processing, and a known example of such a fiber laser device is a master oscillator power amplifier (MOPA) laser having a master oscillator and a power amplifier (see, for example, Patent Document 1). In such a MOPA laser device, deterioration of components such as the optical fiber and the laser diode during laser output can cause a change in the amount of signal light output from the MO and the amount of signal light output from the PA. If the amount of signal light output from the MO becomes smaller than the amount of signal light output from the PA, undesirable laser oscillation called parasitic oscillation can occur, potentially causing the device to malfunction.

[0003] Japanese Patent Application Laid-Open No. 2017-224679

[0004] The present invention has been made in view of the above problems of the prior art, and has as its object to provide a laser device capable of suppressing the occurrence of parasitic oscillation.

[0005] According to one aspect of the present invention, there is provided a laser device capable of suppressing occurrence of parasitic oscillation, the laser device including a light generating unit capable of generating seed signal light, an optical amplifier unit capable of amplifying the seed signal light to generate amplified signal light, a light emitting unit capable of emitting the amplified signal light, and a light amount P of the seed signal light propagating from the light generating unit to the optical amplifier unit. MO and a first photodetector capable of detecting the amount of light P of the amplified signal light propagating from the optical amplifier unit toward the light emitting unit. PAand a control unit that controls at least the light generation unit and the optical amplification unit. The light generation unit includes a first amplification optical fiber including a first core doped with a first active element and a first cladding that surrounds the first core and has a refractive index lower than that of the first core, and a first pumping light source that can generate first pumping light that excites the first active element. The light generation unit is configured to supply the first pumping light to the first cladding. The optical amplification unit includes a second amplification optical fiber including a second core doped with a second active element and a second cladding that surrounds the second core and has a refractive index lower than that of the second core, and a second pumping light source that can generate second pumping light that excites the second active element. The optical amplifier is configured to supply the seed signal light generated by the light generation unit to the second core and the second pump light to the second clad, respectively. The control unit calculates the amount of light P of the amplified signal light detected by the second photodetector when the amplified signal light is emitted from the light emission unit. PA The amount of light P of the seed signal light detected by the first photodetector relative to MO The ratio (P MO / P PA The first pumping light source and the second pumping light source are controlled so that the difference (i.e., ...

[0006] Fig. 1 is a schematic block diagram showing the configuration of a laser device according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view showing the structure of a first amplification optical fiber in the laser device shown in Fig. 1. Fig. 3 is a cross-sectional view showing the structure of a second amplification optical fiber in the laser device shown in Fig. 1. Fig. 4A is a cross-sectional view showing the structure of a P MO 4B is a graph showing the change in the power of the output laser light when P = 0 W in the laser device shown in FIG. MO = 3W, P PA 4C is a graph showing the change in the power of the output laser light when P = 50.1 W. MO = 11W, P PA4D is a graph showing the change in the power of the output laser light when P = 74.2 W. MO = 20W, P PA 4E is a graph showing the change in the power of the output laser light when P = 84.0 W. MO = 30W, P PA 4F is a graph showing the change in the power of the output laser light when P = 94.5 W. MO = 49W, P PA 5 is a graph showing a change in the power of the output laser light when the power of the output laser light is 113.1 W. Fig. 5 is a schematic block diagram showing the configuration of a laser device according to a second embodiment of the present invention. Fig. 6 is a schematic block diagram showing the configuration of a laser device according to a third embodiment of the present invention.

[0007] Hereinafter, an embodiment of a laser device according to the present invention will be described in detail with reference to FIGS. 1 to 6. In FIGS. 1 to 6, identical or corresponding components are designated by the same reference numerals, and redundant description will be omitted. In addition, in FIGS. 1 to 6, the scale and dimensions of each component may be exaggerated, and some components may be omitted. In the following description, unless otherwise specified, terms such as "first" and "second" are used merely to distinguish components from one another, and do not represent a specific order or sequence.

[0008] FIG. 1 is a schematic block diagram showing the configuration of a laser device 1 according to a first embodiment of the present invention. This laser device 1 is configured as a fiber laser laser, particularly as an oscillator power amplifier (MOPA) type laser. As shown in FIG. 1 , the laser device 1 includes a light generation unit 10 (MO) capable of generating a seed signal light S, an optical amplifier 20 (PA) capable of amplifying the seed signal light S generated by the light generation unit 10 to generate an amplified signal light S, a light output unit 30 capable of outputting the amplified signal light S generated by the optical amplifier 20, and a control unit 40 that controls various components including the light generation unit 10 and the optical amplifier 20. In this specification, unless otherwise specified, the direction in which light propagates from the light generation unit 10 toward the light output unit 30 will be referred to as the “downstream side,” and the opposite direction will be referred to as the “upstream side.”

[0009] The light generating unit 10 includes an optical resonator 11, one or more pumping light sources 12 (first pumping light sources) capable of generating pumping light Q1 (first pumping light), optical fibers 13 extending from each pumping light source 12, and an optical combiner 14 that combines the pumping light Q1 propagating through the optical fiber 13 and introduces the combined light into the optical resonator 11. A delivery fiber 51 is connected downstream of the optical resonator 11.

[0010] Each of the pumping light sources 12 includes a Fabry-Perot type semiconductor laser element made of, for example, a GaAs-based semiconductor, and can generate laser light with a center wavelength of, for example, 915 nm or 976 nm as the pumping light Q1. In this embodiment, the pumping light source 12 is connected upstream of the optical resonator 11, but the pumping light source 12 may also be connected downstream of the optical resonator 11, or the pumping light source 12 may also be connected both upstream and downstream of the optical resonator 11. The number of pumping light sources 12 is not limited to a specific value.

[0011] The optical resonator 11 includes an amplifying optical fiber 15 (first amplifying optical fiber) capable of amplifying laser light, a high-reflection portion 16 that reflects light in a predetermined wavelength band (e.g., 1070 nm) with a high reflectivity (e.g., a reflectivity close to 100%), and a low-reflection portion 17 that reflects light of this wavelength with a lower reflectivity (e.g., a reflectivity of 10%) than the high-reflection portion 16. The high-reflection portion 16 and the low-reflection portion 17 are formed, for example, by a fiber Bragg grating (FBG) or a mirror formed by periodically changing the refractive index of the optical fiber along the light propagation direction. The high-reflection portion 16 and the low-reflection portion 17 shown in FIG. 1 are each formed by a double-clad fiber or a triple-clad fiber on which a fiber Bragg grating is formed.

[0012] FIG. 2 is a cross-sectional view schematically illustrating the structure of the amplification optical fiber 15. As shown in FIG. 2, the amplification optical fiber 15 has a core 151 (first core), an inner cladding 152 (first cladding) that surrounds the core 151, and an outer cladding 153 that surrounds the inner cladding 152. The core 151 is formed, for example, by doping quartz with an element such as aluminum that increases the refractive index, and further doping at least a portion of the core with an active element (first active element). Examples of active elements that can be doped into the core 151 include rare earth elements such as ytterbium (Yb), erbium (Er), thulium (Tm), and neodymium (Nd), as well as bismuth (Bi), chromium (Cr), and the like. In this embodiment, an example in which Yb is doped into the core 151 of the amplification optical fiber 15 will be described, but the present invention is not limited to this.

[0013] The inner cladding 152 is made of, for example, quartz to which no dopant is added. The refractive index of the inner cladding 152 is lower than that of the core 151, and an optical waveguide is formed inside the core 151. The outer cladding 153 is made of, for example, an ultraviolet curing resin. The refractive index of the outer cladding 153 is lower than that of the inner cladding 152, and an optical waveguide is also formed inside the inner cladding 152.

[0014] The optical combiner 14 and the high-reflectivity portion 16 are fusion-spliced ​​to each other at a fusion splice 61 so that the core of the optical fiber 13 is optically coupled to the inner cladding of the high-reflectivity portion 16. Furthermore, the high-reflectivity portion 16 and the amplification optical fiber 15 are fusion-spliced ​​to each other at a fusion splice 62 so that the core of the high-reflectivity portion 16 is optically coupled to a core 151 of the amplification optical fiber 15 and the inner cladding of the high-reflectivity portion 16 is optically coupled to an inner cladding 152 of the amplification optical fiber 15. Therefore, as shown in FIG. 1 , the pumping light Q1 generated by the pumping light source 12 propagates through the core of the optical fiber 13, is introduced into the inner cladding of the high-reflectivity portion 16 by the optical combiner 14, is introduced into the inner cladding 152 of the amplification optical fiber 15, and propagates inside the inner cladding 152 and the core 151 of the amplification optical fiber 15.

[0015] The amplification optical fiber 15 and the low-reflection portion 17 are fusion-spliced ​​to each other at a fusion splice 63 so that the core of the low-reflection portion 17 is optically coupled to a core 151 of the amplification optical fiber 15 and the inner clad of the low-reflection portion 17 is optically coupled to an inner clad 152 of the amplification optical fiber 15. Furthermore, the low-reflection portion 17 and the delivery fiber 51 are fusion-spliced ​​to each other at a fusion splice 64 so that the core of the low-reflection portion 17 is optically coupled to a core of the delivery fiber 51.

[0016] The pumping light Q1 propagating through the inner cladding 152 and core 151 of the amplification optical fiber 15 is absorbed by the active element (Yb) as it passes through the core 151, exciting the active element and generating spontaneous emission light. The spontaneous emission light generated by the excitation of the active element is retroreflected between the high-reflection portion 16 and the low-reflection portion 17, amplifying light of a specific wavelength (e.g., 1070 nm) and generating laser oscillation. The laser light amplified by the optical resonator 11 propagates through the core 151 of the amplification optical fiber 15, a portion of which passes through the low-reflection portion 17 and enters the core of the delivery fiber 51 as the seed signal light S1. In this way, the light generating unit 10 is configured to supply the pumping light generated by the pumping light source 12 to the inner cladding 152 of the amplification optical fiber 15 to generate the seed signal light S1.

[0017] The optical amplification unit 20 includes an amplification optical fiber 21 (second amplification optical fiber) capable of amplifying the seed signal light S generated in the light generation unit 10, one or more pumping light sources 22 (second pumping light sources) that generate pumping light Q (second pumping light), optical fibers 23 extending from each pumping light source 22, and an optical combiner 24 that combines the pumping light Q propagating through the optical fiber 23 and introduces it into the amplification optical fiber 21. A delivery fiber 52 is connected downstream of the optical combiner 24, and the light emitting unit 30 is disposed at the downstream end of this delivery fiber 52.

[0018] Each of the pumping light sources 22 includes a Fabry-Perot type semiconductor laser element made of, for example, a GaAs-based semiconductor, and can generate laser light with a center wavelength of, for example, 915 nm or 976 nm as the pumping light Q2. In this embodiment, the pumping light source 22 is connected to the downstream side of the amplification optical fiber 21, but the pumping light source 22 may also be connected to the upstream side of the amplification optical fiber 21, or the pumping light source 22 may also be connected to both the upstream side and downstream side of the amplification optical fiber 21. Furthermore, the number of pumping light sources 22 is not limited to a specific value.

[0019] 3 is a cross-sectional view schematically illustrating the structure of the amplification optical fiber 21. As shown in FIG. 3, the amplification optical fiber 21 has a core 211 (second core), an inner cladding 212 (second cladding) that surrounds the core 211, and an outer cladding 213 that surrounds the inner cladding 212. The core 211 is formed, for example, by doping quartz with an element such as aluminum that increases the refractive index, and further doping at least a portion of the core 211 with an active element (second active element). Examples of the active element that can be doped into the core 211 include rare earth elements such as ytterbium (Yb), erbium (Er), thulium (Tm), and neodymium (Nd), bismuth (Bi), and chromium (Cr). In this embodiment, an example in which Yb is doped into the core 211 of the amplification optical fiber 21 will be described, but the present invention is not limited to this.

[0020] The inner cladding 212 is made of, for example, quartz to which no dopant is added. The refractive index of the inner cladding 212 is lower than that of the core 211, and an optical waveguide is formed inside the core 211. The outer cladding 213 is made of, for example, an ultraviolet curing resin. The refractive index of the outer cladding 213 is lower than that of the inner cladding 212, and an optical waveguide is also formed inside the inner cladding 212.

[0021] The delivery fiber 51 and the amplification optical fiber 21 are fusion-spliced ​​to each other at a fusion splice section 65 so that the core of the delivery fiber 51 and the core 211 of the amplification optical fiber 21 are optically coupled, and the amplification optical fiber 21 and the optical combiner 24 are connected to each other at a fusion splice section 66 so that the inner clad 212 of the amplification optical fiber 21 and the core of the optical fiber 23 are optically coupled, and the core 211 of the amplification optical fiber 21 and the core of the delivery fiber 52 are optically coupled.

[0022] The seed signal light S1 generated by the light generating unit 10 and propagating through the core of the delivery fiber 51 is incident on the core 211 of the amplification optical fiber 21 and propagates inside the core 211. Furthermore, the pumping light Q2 generated by the pumping light source 22 is introduced into the inner clad 212 of the amplification optical fiber 21 by the optical combiner 24 and propagates inside the inner clad 212 and the core 211 of the amplification optical fiber 21. As this pumping light Q2 passes through the core 211, an active element (e.g., Yb) doped in the core 211 absorbs the pumping light Q2 and is excited, and the seed signal light S1 propagating through the core 211 is amplified by stimulated emission to generate amplified signal light S2. This amplified signal light S2 is introduced into the core of the delivery fiber 52 via the optical combiner 24 and emitted from the light emitting unit 30.

[0023] The control unit 40 is configured to control the outputs of the pumping light sources 12 and 22, for example, by controlling the current supplied to the pumping light sources 12 and 22. That is, the control unit 40 controls the drive current supplied to the pumping light source 12 of the light generating unit 10, thereby controlling the output of the pumping light source 12, and as a result, can control the light intensity of the seed signal light S1 generated in the light generating unit 10. Furthermore, the control unit 40 controls the drive current supplied to the pumping light source 22 of the optical amplifying unit 20, thereby controlling the output of the pumping light source 22, and as a result, can control the light intensity of the amplified signal light S2 amplified in the optical amplifying unit 20.

[0024] As shown in FIG. 1, the laser device 1 in this embodiment has a light intensity (P MO ) and a photodetector 71 (first photodetector) capable of detecting the amount of light (P PA The light detectors 71 and 72 are communicably connected to the control unit 40, and detection signals from the light detectors 71 and 72 are sent to the control unit 40.

[0025] In this embodiment, a photodetector capable of detecting Rayleigh scattering of the seed signal light S1 propagating through the delivery fiber 51 is used as the photodetector 71, and this photodetector 71 is disposed in the vicinity of the delivery fiber 51. The photodetector 71 calculates the light amount P of the seed signal light S1 propagating through the core of the delivery fiber 51 from the detected Rayleigh scattering. MO Furthermore, a photodetector capable of detecting Rayleigh scattering of the amplified signal light S2 propagating through the delivery fiber 52 is used as the photodetector 72, and this photodetector 72 is disposed in the vicinity of the delivery fiber 52. The photodetector 72 calculates the light amount P of the amplified signal light S2 propagating through the core of the delivery fiber 52 from the detected Rayleigh scattering. PA It is now possible to calculate the following.

[0026] In this embodiment, the light amount P of the seed signal light S1 is detected by the photodetector 71.MO is calculated, and the light amount P of the amplified signal light S2 is detected by the photodetector 72. PA The detection results of Rayleigh scattering by the photodetector 71 and the detection results of Rayleigh scattering by the photodetector 72 are sent to the control unit 40, and the control unit 40 calculates the light amount P of the seed signal light S1. MO and the light amount P of the amplified signal light S2 PA It is also possible to calculate

[0027] During operation of the laser device 1, that is, while the amplified signal light S2 is being emitted from the light emitting unit 30, the control unit 40 determines the light amount P MO and the light amount P of the amplified signal light S2 sent from the photodetector 72 PA Tokara P PA P for MO The ratio (P MO / P PA The control unit 40 has a memory that stores a predetermined threshold value α therein, and calculates P MO / P PA The excitation light sources 12 and 22 (the driving currents supplied to the excitation light sources 12 and 22) can be controlled so that P becomes equal to or greater than this threshold value α. This threshold value α is the P MO / P PA As described above, the control unit 40 determines the lower limit value of P MO / P PA The excitation light sources 12 and 22 are controlled so that P is equal to or greater than the threshold value α. MO / P PA The value of is always maintained within a range in which parasitic oscillation is suppressed, thereby suppressing parasitic oscillation within the laser device 1. This prevents failure of the laser device 1.

[0028] More specifically, the control unit 40 determines whether P MO / P PA When becomes less than α, the light amount P MO For example, the drive current supplied to the pump light source 12 is increased to increase the amount of light P PAFor example, the drive current supplied to the pump light source 22 is reduced to reduce the amount of light P MO and the light amount P PA In order to reduce the .DELTA..times ...

[0029] Alternatively, the control unit 40 may, for some reason, MO / P PA When (P MO / P PA When the laser device 1 is stopped (regardless of whether P is less than α), it is preferable to stop the drive current to the pumping light source 12 after stopping the drive current to the pumping light source 22. PA After decreasing, P MO will decrease, so P MO / P PA Therefore, the laser device 1 can be stopped while maintaining a high power consumption, that is, while suppressing parasitic oscillation.

[0030] P MO and P PA When the value of was changed, the change in the power of the amplified signal light S2 emitted from the light emitting portion 30 was observed. The results are shown in Figures 4A to 4F. The conditions for each graph in Figures 4A to 4F are as shown in the table below.

[0031] 4A and 4B show that large pulses are generated, indicating the occurrence of parasitic oscillation. In FIGS. 4C to 4F, no large pulses are generated, indicating that parasitic oscillation is suppressed. Therefore, it is considered preferable that the threshold value α be 0.148 or more and 0.433 or less.

[0032] As described above, the laser device 1 in this embodiment includes a light generation unit 10 configured to supply pumping light Q1 (first pumping light) from a pumping light source 12 (first pumping light source) to the inner clad 152 (first clad) of an amplification optical fiber 15 (first amplification optical fiber) to generate a seed signal light S1, and an optical amplification unit 20 configured to supply the seed signal light S1 to the core 211 (second core) of an amplification optical fiber 21 (second amplification optical fiber) and supply pumping light Q2 (second pumping light) from a pumping light source 22 (second pumping light source) to the inner clad 212 (second clad) to amplify the seed signal light S1 and generate amplified signal light S2. MO and a photodetector 71 (first photodetector) capable of detecting the amount of light P PA and a photodetector 72 (second photodetector) capable of detecting the ratio P MO / P PA The control unit 40 controls the pump light sources 12 and 22 so that P becomes equal to or greater than a predetermined threshold value α. The threshold value α is the P when parasitic oscillation is suppressed. MO / P PA is set as the lower limit of

[0033] According to this configuration, when the amplified signal light S2 is emitted from the light emitting unit 30, the control unit 40 controls the P MO / P PA The excitation light sources 12 and 22 are controlled so that P is equal to or greater than the threshold value α. MO / P PA The value of is always maintained within a range in which parasitic oscillation is suppressed, thereby suppressing parasitic oscillation within the laser device 1. This prevents failure of the laser device 1.

[0034] In this case, the control unit 40 determines the ratio P MO / P PA When the ratio P becomes less than the threshold value α, the pump light sources 12 and 22 may be controlled to increase the light intensity of the seed signal light S1 or decrease the light intensity of the amplified signal light S2. MO / P PAbecomes less than the threshold value α, the supply of current to the pump light sources 12, 22 may be stopped. By these controls, parasitic oscillations in the laser device 1 can be suppressed, and breakdowns in the laser device 1 can be suppressed.

[0035] 5 is a schematic block diagram showing the configuration of a laser device 2 according to a second embodiment of the present invention. As shown in FIG. 5, the delivery fiber 51 according to this embodiment is provided with two cladding mode strippers 81 and 82 that remove cladding modes propagating through the delivery fiber 51. The cladding mode stripper 81 is arranged closer to the light generation unit 10 than the photodetector 71, and the cladding mode stripper 82 is arranged closer to the optical amplifier 20 than the photodetector 71. Furthermore, the delivery fiber 52 according to this embodiment is provided with a cladding mode stripper 83 that removes cladding modes propagating through the delivery fiber 52. The cladding mode stripper 83 is arranged closer to the optical amplifier 20 than the photodetector 72. These cladding mode strippers 81, 82, and 83 can be configured in a known manner to remove cladding modes.

[0036] In the delivery fiber 51, it is conceivable that pumping light that has not been absorbed in the amplification optical fiber 15 and leaked signal light generated upstream of the fusion splice 64 propagate through the cladding as cladding modes. However, since the cladding mode stripper 81 can remove such cladding modes, the influence of the cladding modes is reduced in the photodetector 71 located downstream of the cladding mode stripper 81, and the light amount P of the seed signal light S1 is reduced. MO The detection accuracy can be improved.

[0037] It is also conceivable that a portion of the pumping light Q2 that is not absorbed by the amplification optical fiber 21 propagates in the delivery fiber 51 as a cladding mode. However, since the cladding mode stripper 82 can remove such a cladding mode, the influence of the cladding mode is reduced in the photodetector 71 located upstream of the cladding mode stripper 82, and the light amount P of the seed signal light S1 is reduced. MO The detection accuracy can be improved.

[0038] It is also conceivable that a portion of the amplified signal light S2 leaks into the clad of the delivery fiber 52 and becomes a clad mode. However, since the clad mode stripper 83 can remove such a clad mode, the influence of the clad mode is reduced in the photodetector 72 located downstream of the clad mode stripper 83, and the light amount P of the amplified signal light S2 PA The detection accuracy can be improved.

[0039] 6 is a schematic block diagram showing the configuration of a laser device 3 according to the third embodiment of the present invention. As shown in FIG. 6, a photodetector 71 according to this embodiment includes an optical filter 75 (first optical filter) that selectively transmits light in a wavelength range corresponding to the Rayleigh scattering of the seed signal light S1. The photodetector 71 detects the light amount P MO The optical filter 75 makes it difficult for the photodetector 71 to detect light outside the wavelength range corresponding to the Rayleigh scattering of the seed signal light S1. MO The detection accuracy is improved.

[0040] Similarly, the photodetector 72 includes an optical filter 76 (second optical filter) that selectively transmits light in a wavelength range corresponding to the Rayleigh scattering of the amplified signal light S2. PA The optical filter 76 makes it difficult for the photodetector 72 to detect light outside the wavelength range corresponding to the Rayleigh scattering of the amplified signal light S2. PA The detection accuracy is improved.

[0041] In the second embodiment described above, these optical filters 75 and 76 can also be provided in the photodetectors 71 and 72. In this case, the influence of cladding modes in the photodetectors 71 and 72 is reduced, and the influence of light other than the light to be detected is also reduced, further improving the detection accuracy of the light amount of the signal light.

[0042] In the above-described embodiment, an example has been described in which photodetectors capable of detecting Rayleigh scattering of signal light are used as the photodetectors 71 and 72. However, the types of the photodetectors 71 and 72 are not limited to this. For example, the photodetector 71 may be configured to branch the seed signal light S propagating through the delivery fiber 51 using an optical coupler and detect the branched light to detect the amount of the seed signal light S. Alternatively, the photodetector 72 may be configured to branch the amplified signal light S propagating through the delivery fiber 52 using an optical coupler and detect the branched light to detect the amount of the amplified signal light S. Alternatively, the photodetector 71 may be configured to detect the amount of the seed signal light S by detecting light leaking from the fusion splice 64 or 65, and the photodetector 72 may be configured to detect the amount of the amplified signal light S by detecting light leaking from the fusion splice 66.

[0043] As described above, the present invention includes the following aspects.

[0044] A first aspect of the present invention provides a light generating unit capable of generating seed signal light, the light generating unit including: a first amplification optical fiber including a first core doped with a first active element and a first clad surrounding the first core and having a refractive index lower than that of the first core; and a first pumping light source capable of generating first pumping light that excites the first active element, the light generating unit being configured to supply the first pumping light to the first clad; an optical amplifying unit capable of amplifying the seed signal light to generate amplified signal light, the light generating unit including: a second amplification optical fiber including a second core doped with a second active element and a second clad surrounding the second core and having a refractive index lower than that of the second core; and a second pumping light source capable of generating second pumping light that excites the second active element. an optical amplification unit configured to supply the seed signal light generated by the light generation unit to the second core and the second pump light to the second clad, respectively; a light emission unit capable of emitting the amplified signal light; and a light amount P of the seed signal light propagating from the light generation unit toward the optical amplification unit. MOa first photodetector capable of detecting the amount of light P of the amplified signal light propagating from the optical amplifier unit toward the light emitting unit; PA and a control unit that controls at least the light generation unit and the optical amplification unit, wherein the control unit detects a light amount P of the amplified signal light detected by the second photodetector when the amplified signal light is emitted from the light emission unit. PA The amount of light P of the seed signal light detected by the first photodetector relative to MO The ratio (P MO / P PA and controlling the first excitation light source and the second excitation light source so that the difference (i.e., ...

[0045] Aspect 2 of the present invention is the laser device according to aspect 1, wherein the control unit controls the ratio (P MO / P PA ) becomes less than the predetermined threshold, the first pumping light source and the second pumping light source are controlled to increase the amount of light of the seed signal light generated by the light generation unit or to decrease the amount of light of the amplified signal light generated by the optical amplification unit.

[0046] Aspect 3 of the present invention is the laser device according to aspect 1, wherein the control unit controls the ratio (P MO / P PA ) becomes less than the predetermined threshold, the supply of current to the first excitation light source and the second excitation light source is controlled to be stopped.

[0047] A fourth aspect of the present invention is the laser device according to any one of the first to third aspects, wherein the first photodetector includes a first optical filter that selectively transmits light in a wavelength range corresponding to the seed signal light, and detects a light amount P of the seed signal light through the first optical filter. MO The device is configured to detect:

[0048] Aspect 5 of the present invention is the laser device according to any one of aspects 1 to 4, wherein the second photodetector includes a second optical filter that selectively transmits light in a wavelength range corresponding to the amplified signal light, and a light amount P of the amplified signal light is detected via the second optical filter. PA The device is configured to detect:

[0049] A sixth aspect of the present invention is the laser device according to any one of the first to fifth aspects, further comprising a first cladding mode stripper capable of removing a cladding mode on the light generating unit side of the first photodetector.

[0050] A seventh aspect of the present invention is the laser device according to any one of the first to sixth aspects, further comprising a second cladding mode stripper capable of removing a cladding mode on the optical amplification section side of the second photodetector.

[0051] Aspect 8 of the present invention is the laser device according to any one of aspects 1 to 7, wherein the predetermined threshold value is equal to or greater than 0.148 and equal to or less than 0.433.

[0052] A ninth aspect of the present invention is directed to the laser device of any one of the first to eighth aspects, wherein when the device is shut down, the control unit stops the supply of drive current to the second excitation light source and then stops the supply of drive current to the first excitation light source.

[0053] Although the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-described embodiments and may be embodied in various different forms within the scope of the technical concept thereof.

[0054] This application is based on and claims priority from Japanese Patent Application No. 2024-075112, filed on May 7, 2024, the disclosure of which is incorporated herein by reference in its entirety.

[0055] The present invention is suitably used in a laser device.

[0056] 1, 2, 3 Laser device 10 Light generation unit 11 Optical resonator 12 Pumping light source (first pumping light source) 15 Amplification optical fiber (first amplification optical fiber) 20 Optical amplification unit 21 Amplification optical fiber (second amplification optical fiber) 22 Pumping light source (second pumping light source) 30 Light emission unit 40 Control unit 71 Photodetector (first photodetector) 72 Photodetector (second photodetector) 75 Optical filter (first optical filter) 76 Optical filter (second optical filter) 81 Cladding mode stripper (first cladding mode stripper) 82 Cladding mode stripper 83 Cladding mode stripper (second cladding mode stripper) 151 Core (first core) 152 Inner cladding (first cladding) 153 Outer cladding 211 Core (second core) 212 Inner cladding (second cladding) 213 Outer cladding Q1 Pumping light (first pumping light) Q2 Pumping light (second pumping light) S1 Seed signal light S2 Amplified signal light

Claims

1. A light generation unit capable of generating seed signal light, comprising: a first amplification optical fiber including a first core doped with a first active element and a first clad surrounding the first core and having a refractive index lower than that of the first core; and a first pumping light source capable of generating first pumping light that excites the first active element, the light generation unit configured to supply the first pumping light to the first clad; an optical amplification unit capable of amplifying the seed signal light to generate amplified signal light, comprising: a second amplification optical fiber including a second core doped with a second active element and a second clad surrounding the second core and having a refractive index lower than that of the second core; and a second pumping light source capable of generating second pumping light that excites the second active element, the optical amplification unit configured to supply the seed signal light generated by the light generation unit to the second core and the second pumping light to the second clad, a light output unit capable of outputting the amplified signal light; and a light amount P of the seed signal light propagating from the light generation unit toward the optical amplification unit. MO a first photodetector capable of detecting the amount of light P of the amplified signal light propagating from the optical amplifier unit toward the light emitting unit; PA and a control unit that controls at least the light generation unit and the optical amplification unit, wherein the control unit is configured to detect a light amount P of the amplified signal light detected by the second photodetector when the amplified signal light is emitted from the light emission unit. PA The amount of light P of the seed signal light detected by the first photodetector MO The ratio (P MO / P PA a laser device controlling the first excitation light source and the second excitation light source so that the difference between the excitation light source and the second excitation light source is equal to or greater than a predetermined threshold value.

2. The control unit controls the ratio (P MO / P PA 2. The laser device according to claim 1, wherein when a difference between the first pumping light source and the second pumping light source is less than the predetermined threshold, the laser device controls the first pumping light source and the second pumping light source so as to increase the amount of the seed signal light generated by the light generating unit or to decrease the amount of the amplified signal light generated by the optical amplifying unit.

3. The control unit controls the ratio (P MO / P PA 2. The laser device according to claim 1, wherein when a difference between the first excitation light source and the second excitation light source is less than the predetermined threshold, the supply of current to the first excitation light source and the second excitation light source is stopped.

4. The first photodetector includes a first optical filter that selectively transmits light in a wavelength range corresponding to the seed signal light, and detects the amount of light P of the seed signal light through the first optical filter. MO The laser device according to claim 1 , configured to detect:

5. The second photodetector includes a second optical filter that selectively transmits light in a wavelength range corresponding to the amplified signal light, and detects the amount of light P of the amplified signal light through the second optical filter. PA 5. The laser device according to claim 1, configured to detect:

6. A laser device according to any one of claims 1 to 5, further comprising a first cladding mode stripper capable of removing a cladding mode on the light generating section side of the first photodetector.

7. A laser device according to any one of claims 1 to 6, further comprising a second cladding mode stripper capable of removing cladding modes on the optical amplifier side of the second photodetector.

8. A laser device according to any one of claims 1 to 7, wherein the predetermined threshold is equal to or greater than 0.148 and equal to or less than 0.

433.

9. A laser device described in any one of claims 1 to 8, wherein when the device is shut down, the control unit stops supplying drive current to the second excitation light source and then stops supplying drive current to the first excitation light source.

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