JP2021190452A - Laser module and fiber laser device - Google Patents

Abstract

To provide a laser module that can stably output laser light with a narrowed wavelength.SOLUTION: A laser module includes ah optical fiber, a semiconductor laser element 24 that emits a laser beam L from the emission end surface 124B, and a condensing lens that condenses and couples the laser beam to the optical fiber, and wavelength stabilizing elements 40A, 40B, and 40C having reflective surfaces 140A, 140B, and 140C located on the optical path of the laser beam. The reflective surface 140A of the wavelength stabilizing element 40A is arranged at an angle θ1 (=0) with respect to the reference direction D, and the reflecting surface 140B of the wavelength stabilizing element 40B is arranged at an angle θ2 (>θ1) with respect to the reference direction D. -θH≤θ1≤θH, and θ2-θ1≤2θH are satisfied.SELECTED DRAWING: Figure 5

Description

The present invention relates to a laser module and a fiber laser apparatus, and more particularly to a laser module that condenses and outputs laser light emitted from a plurality of semiconductor laser elements.

Conventionally, a laser module that collects laser light emitted from a plurality of semiconductor laser elements and outputs a high-power laser light has been known. Since the oscillation wavelength of the semiconductor laser element used in such a laser module fluctuates due to manufacturing variations and has temperature dependence, in order to stably output laser light of a desired wavelength, each of them is used. It is necessary to narrow the wavelength of the laser beam output from the semiconductor laser element of the above to a specific wavelength. As one of the methods for narrowing the wavelength of the laser light of a plurality of semiconductor laser elements, a wavelength stabilizing element called Volume Bragg Grating (VBG) whose refractive index changes periodically at a predetermined lattice interval is used. A method is known in which an external resonator is formed between a reflecting surface of a wavelength stabilizing element and an emitting end surface of a semiconductor laser element to selectively reflect a specific wavelength (see, for example, FIG. 14A of Patent Document 1). ).

In a conventional laser module using such a wavelength stabilizing element, an optical component such as a mirror for converting an optical path of a laser beam is fixed to a housing by a resin, but the wavelength stabilizing element is adjusted. After the heart is completed, these resins may expand and contract due to temperature changes and the like. In such a case, it is conceivable that the position and angle of the optical component fixed by the resin will change, and the optical path of the laser beam incident on the wavelength stabilizing element will shift. When the deviation of the optical path of the laser beam incident on the wavelength stabilizing element exceeds the allowable range in which an external resonator can be formed between the reflecting surface of the wavelength stabilizing element and the emitting end surface of the semiconductor laser element, The wavelength stabilizing element makes it impossible to narrow the wavelength of the laser beam.

U.S. Patent Application Publication No. 2016/0172823

The present invention has been made in view of the problems of the prior art, and the first object of the present invention is to provide a laser module capable of stably outputting a laser beam having a narrowed wavelength band. do.

A second object of the present invention is to provide a fiber laser apparatus capable of stably amplifying a laser beam.

According to the first aspect of the present invention, there is provided a laser module capable of stably outputting a laser beam having a narrowed wavelength band. This laser module includes an optical fiber, at least one semiconductor laser element that emits laser light from an emission end face, at least one condenser lens that collects the laser light and couples it to the optical fiber, and the laser light. It comprises at least two wavelength stabilizing elements having a reflective surface located on the optical path of. The at least two wavelength stabilizing elements are arranged with the reflecting surface when the reflecting surface is arranged at an angle within the range of _{−θ H} to + θ _{H with} respect to the reference direction perpendicular to the optical axis of the laser beam. An external resonator is formed between the emission end face of the at least one semiconductor laser element and the wavelength of the laser light is narrowed to a specific wavelength. The at least two wavelength stabilizing elements include a first wavelength stabilizing element in which the reflecting surface is arranged at an _{angle θ 1 with respect to the reference direction, and the reflecting surface having the reflecting surface at an angle θ 1 with respect to the reference direction.} It includes a second wavelength stabilizing element arranged at a larger angle θ _2. At least one of _{θ 1} and θ ₂ is in the range _{from −θ H} to + θ _{H , and θ 2} −θ ₁ ≦ 2θ _H.

In the present specification, the term "range from X to Y" means a range including both the value of X and the value of Y.

According to the second aspect of the present invention, there is provided a fiber laser apparatus capable of stably amplifying a laser beam. The fiber laser apparatus includes an excitation light source including the above-mentioned laser module, and an amplification optical fiber having a core optically connected to the above-mentioned optical fiber of the above-mentioned laser module and to which rare earth element ions are added.

According to one aspect of the present invention, it is possible to stably output a laser beam having a narrowed wavelength band.

FIG. 1 is a block diagram schematically showing a configuration of a fiber laser device according to a first embodiment of the present invention. FIG. 2 is a plan view schematically showing a laser module used as an excitation light source in the fiber laser apparatus shown in FIG. FIG. 3 is a cross-sectional view taken along the line AA of FIG. FIG. 4A is a schematic diagram for explaining the operation of the wavelength stabilizing element in the laser module of FIG. FIG. 4B is a schematic diagram for explaining the operation of the wavelength stabilizing element in the laser module of FIG. FIG. 5 is a schematic diagram illustrating the arrangement of wavelength stabilizing elements in the laser module of FIG. FIG. 6 is a schematic diagram illustrating the operation of the wavelength stabilizing element when the optical path of the laser beam changes in the laser module of FIG. FIG. 7 is a schematic diagram showing an example of an effective angle range of the wavelength stabilizing element in the laser module of FIG. 2. FIG. 8 is a schematic diagram showing another example of the effective angle range of the wavelength stabilizing element in the laser module of FIG. FIG. 9 is a plan view schematically showing the laser module according to the second embodiment of the present invention.

Hereinafter, embodiments of the laser module and the fiber laser apparatus according to the present invention will be described in detail with reference to FIGS. 1 to 9. In FIGS. 1 to 9, the same or corresponding components are designated by the same reference numerals, and duplicate description will be omitted. Further, in FIGS. 1 to 9, the scale and dimensions of each component may be exaggerated or some components may be omitted. In the following description, unless otherwise noted, terms such as "first" and "second" are only used to distinguish the components from each other and represent a particular order or order. It's not a thing.

FIG. 1 is a block diagram schematically showing the configuration of the fiber laser apparatus 1 according to the first embodiment of the present invention. As shown in FIG. 1, the fiber laser apparatus 1 of the present embodiment includes an optical resonator 3 including an amplification optical fiber 2 capable of amplifying a laser beam, and an optical resonator from one end side (front) of the optical resonator 3. A plurality of front excitation light sources 4A that supply excitation light to 3, a plurality of rear excitation light sources 4B that supply excitation light to the optical resonator 3 from the other end side (rear) of the optical resonator 3, and a plurality of front excitation light sources. A front light combiner 5A that combines the excitation light output from 4A and introduces it into the optical resonator 3, and a rear light combiner that combines the excitation light output from a plurality of rear excitation light sources 4B and introduces it into the optical resonator 3. It includes a delivery fiber 6 extending from the rear light combiner 5B, and a laser output unit 7 provided at the downstream end of the delivery fiber 6. The front excitation light source 4A and the front optical combiner 5A are connected by an optical fiber 8A, and the rear excitation light source 4B and the rear optical combiner 5B are connected by an optical fiber 8B.

The amplification optical fiber 2 of the optical resonator 3 has a core to which rare earth element ions such as ytterbium (Yb), erbium (Er), thulium (Tr), and neodym (Nd) are added, for example. It is composed of a double clad fiber having an inner clad formed around the core and an outer clad formed around the inner clad.

The optical resonator 3 has a high reflection unit 9A that reflects light in a predetermined wavelength band (for example, 1060 nm to 1100 nm) with a high reflectance, and a low reflection unit 9A that reflects light in this wavelength band with a lower reflectance than the high reflection unit 9A. It includes a reflecting portion 9B. The high reflection unit 9A and the low reflection unit 9B are composed of, for example, a fiber Bragg grating (FBG) or a mirror formed by periodically changing the refractive index of the optical fiber along the light propagation direction. In the example shown in FIG. 1, the high reflection portion 9A and the low reflection portion 9B are configured by a fiber Bragg grating.

The optical fibers 8A and 8B connected to the excitation light sources 4A and 4B each have a core and a cladding that surrounds the core and has a refractive index lower than that of the core, and these optical fibers 8A have a refractive index lower than that of the core. Inside the core of, 8B, an optical waveguide is formed in which the excitation light generated by the excitation light sources 4A and 4B propagates.

As the excitation light sources 4A and 4B, for example, a laser module including a high-power multimode semiconductor laser element capable of emitting a laser beam having a wavelength of 975 nm is used. Details of this laser module will be described later. The excitation light generated by each of the forward excitation light sources 4A propagates through the core of the optical fiber 8A toward the forward optical combiner 5A, is coupled by the forward optical combiner 5A, and is introduced into the optical resonator 3. Further, the excitation light generated by each of the rearward excitation light sources 4B propagates through the core of the optical fiber 8B toward the rear light combiner 5B, is coupled by the rear light combiner 5B, and is introduced into the optical resonator 3. The wavelength of the excitation light generated by the front excitation light source 4A and the wavelength of the excitation light generated by the rear excitation light source 4B may be the same or different.

The excitation light introduced into the optical resonator 3 from the excitation light sources 4A and 4B via the optical combiners 5A and 5B propagates inside the inner clad and the core of the amplification optical fiber 2. This excitation light is absorbed by the rare earth element ions added to the core as it passes through the core, and the rare earth element ions are excited to generate spontaneous emission light. This naturally emitted light is recursively reflected between the high reflection portion 9A and the low reflection portion 9B, and light having a specific wavelength (for example, 1070 nm) is amplified to generate laser oscillation. The laser light amplified by the optical resonator 3 propagates inside the core of the amplification optical fiber 2, and a part thereof passes through the low reflection portion 9B. The laser light transmitted through the low reflection section 9B is introduced into the core of the delivery fiber 6 from the rear light combiner 5B, propagates through the core of the delivery fiber 6, and is an output laser beam from the laser output section 7 as shown in FIG. As P, for example, it is emitted toward an object to be processed.

Next, the laser module used in the above-mentioned excitation light sources 4A and 4B will be described in detail. FIG. 2 is a plan view schematically showing the laser module 10 used in the excitation light sources 4A and 4B, and FIG. 3 is a sectional view taken along the line AA of FIG. In FIGS. 2 and 3, the optical path of the laser beam is shown by a dotted line. The laser module 10 in the present embodiment has a housing 12, a laser generation unit 20 arranged inside the housing 12, an optical fiber 14 extending from the outside to the inside of the housing 12, and a cylinder holding the optical fiber 14. It includes a fiber holding portion 16 in the shape of a fiber. A lid (not shown) is arranged on the upper part of the housing 12, and the internal space of the housing 12 is sealed by the lid. The housing 12 is made of a metal such as copper having excellent thermal conductivity, and a metal thin film having high reflectance such as a gold-plated film or an aluminum film is formed on the bottom surface 12A and the inner side surface 12B of the housing 12. Has been done.

The laser generation unit 20 includes a stepped pedestal 21, and the pedestal 21 has six stepped portions 22A to 22F having different heights in the Z direction. In the present embodiment, the step portions 22A to 22F are formed so as to gradually increase from the first step portion 22A in the −X direction. Submounts 23 are arranged on the respective step portions 22A to 22F, and a semiconductor laser element 24 that emits a laser beam L in the + Y direction is mounted on each of the submounts 23.

Further, on each of the step portions 22A to 22F of the pedestal 21, a first axis collimating lens 25 corresponding to the semiconductor laser element 24 and collimating the laser beam L emitted from the semiconductor laser element 24 in the first axis direction and a first A slow axis collimating lens 26 that collimates the laser beam L transmitted through the axial collimating lens 25 in the slow axis direction and a mirror 27 that reflects the laser beam L transmitted through the slow axis collimating lens 26 are arranged.

The mirror 27 has an inclined surface inclined by 45 degrees with respect to the Y direction, and the inclined surface has a characteristic of reflecting light in the wavelength band of the laser beam L by a dielectric multilayer film, a metal thin film, or the like. The optical thin film to have is formed. As a result, the laser beam L transmitted through the slow axis collimating lens 26 is reflected by the optical thin film of the mirror 27, the propagation direction is changed by 90 degrees, and the laser beam L propagates in the + X direction.

The laser module 10 includes three wavelength stabilizing elements 40A, 40B, 40C arranged on the + X direction side of the laser generation unit 20, and a first-axis condensing lens 51 arranged on the + X direction side of the wavelength stabilizing element 40C. The slow-axis condensing lens 52 arranged on the + X-direction side of the fast-axis condensing lens 51 is provided. The wavelength stabilizing elements 40A, 40B, 40C and the condenser lenses 51, 52 are fixed to the bottom surface 12A of the housing 12 between the end face 14A of the optical fiber 14 extending inside the housing 12 and the laser generation unit 20, respectively. ing.

Since the laser oscillation wavelength of the semiconductor laser element 24 fluctuates due to manufacturing variations and has temperature dependence, in the present embodiment, the wavelength stabilizing elements 40A, 40B, and 40C are used to output the laser module 10. The wavelength of the laser beam is stabilized. More specifically, the wavelength stabilizing elements 40A, 40B, and 40C of the present embodiment are composed of a Volume Bragg Grating (VBG) whose refractive index is periodically changed at a predetermined grating interval to narrow the band. It is configured to output a laser beam of a specific wavelength (eg, 975 nm). Details of these wavelength stabilizing elements 40A, 40B, and 40C will be described later.

The first-axis condensing lens 51 collects the laser light output from the wavelength stabilizing elements 40A, 40B, 40C in the first-axis direction and couples it to the end face 14A of the optical fiber 14, and is a slow-axis condensing lens. In 52, the laser light output from the wavelength stabilizing elements 40A, 40B, 40C is collected in the slow axis direction and coupled to the end face 14A of the optical fiber 14.

In such a configuration, the laser beam L emitted in the + Y direction from each of the semiconductor laser elements 24 of the laser generation unit 20 is emitted in the fast axis direction and the slow axis direction by the fast axis collimating lens 25 and the slow axis collimating lens 26, respectively. It is collimated, turned 90 degrees by the mirror 27, and propagates in the + X direction. The laser beam L reflected by the mirror 27 becomes a laser beam whose wavelength is narrowed by the wavelength stabilizing elements 40A, 40B, and 40C. The laser light having a narrowed band of these wavelengths is focused in the fast axis (Z direction) by the fast axis condensing lens 51, and further condensed in the slow axis (Y direction) by the slow axis condensing lens 52. .. As a result, the laser light L emitted from the plurality of semiconductor laser elements 24 is optically coupled to the end face 14A of the optical fiber 14, and the optical resonator 3 of the fiber laser device 1 described above from the laser module 10 as the excitation light (FIG. 1) is output.

Next, the details of the wavelength stabilizing elements 40A, 40B, and 40C described above will be described. 4A and 4B are schematic views for explaining the operation of the wavelength stabilizing elements 40A, 40B, and 40C. In FIGS. 4A and 4B, the wavelength stabilizing elements 40A, 40B, and 40C are collectively illustrated by reference numeral 40 for ease of understanding.

As shown in FIG. 4A, the semiconductor laser device 24 has an active layer 124 sandwiched between an n-type clad layer and a p-type clad layer. A resonator is formed between the high reflection end face 124A and the low reflection end face 124B of the active layer 124, and the laser beam L laser-oscillated by this resonator is emitted from the low reflection end face 124B (emission end face). It has become like.

The wavelength stabilizing element 40 (40A, 40B, 40C) has a reflecting surface 140 (140A, 140B, 140C) located on the optical path of the laser beam L emitted from the semiconductor laser element 24. The wavelength stabilizing element 40 has a specific wavelength (for example, 975 nm) narrowed by forming an external resonator between the reflecting surface 140 and the emission end surface 124B of the active layer 124 of the semiconductor laser element 24. It outputs laser light.

Here, as shown in FIG. 4B, even when the reflecting surface 140 of the wavelength stabilizing element 40 is inclined with respect to the direction D perpendicular to the optical axis of the laser beam L, it is reflected by the reflecting surface 140. If the laser beam R can reach the emission end surface 124B of the active layer 124 of the semiconductor laser element 24 and form an external resonator between the reflection surface 140 and the emission end surface 124B of the active layer 124 of the semiconductor laser element 24, The wavelength of the laser beam L can be narrowed by the wavelength stabilizing element 40. The wavelength stabilizing element 40 (40A, 40B, 40C) in the present embodiment has an angle formed by the reflection surface 140 and the direction D (reference direction) perpendicular to the optical axis of the laser beam L _{from −θ H} to + θ _H. If it is within the range, an external resonator is formed between the reflection surface 140 and the emission end surface 124B of the semiconductor laser element 24 so that the wavelength of the laser light can be narrowed. Hereinafter, the angle of the reflecting surface 140 with respect to the direction D perpendicular to the optical axis of the laser beam L so that the wavelength stabilizing element 40 can form an external resonator with the emitting end surface 124B of the active layer 124 of the semiconductor laser element 24. The range of is referred to as the "effective angle range" of the wavelength stabilizing element 40.

FIG. 5 is a schematic diagram illustrating the arrangement of the wavelength stabilizing elements 40A, 40B, and 40C in the present embodiment. Hereinafter, the direction in which the laser beam propagates from the semiconductor laser element 24 toward the optical fiber 14 is referred to as “downstream side”, and the direction opposite to that is referred to as “upstream side”.

As shown in FIG. 5, a mirror 27, a wavelength stabilizing element 40A, a wavelength stabilizing element 40B, and a wavelength stabilizing element 40C are downstream on the optical path M of the laser beam L emitted from a certain semiconductor laser element 24. They are arranged in order toward each other. In the present embodiment, the wavelength stabilizing element 40A (first wavelength stabilizing element) arranged on the most upstream side has its reflection surface 140A parallel to the reference direction D perpendicular to the optical axis of the laser beam L. Is located in. _{That is, the angle θ 1} formed by the reflecting surface 140A of the wavelength stabilizing element 40A with respect to the reference direction D is 0. In the present embodiment, the reference direction D is a direction (Z direction) along the first axis of the laser beam L.

The wavelength stabilizing element 40B (second wavelength stabilizing element) arranged on the downstream side of the wavelength stabilizing element 40A is arranged so that the reflecting surface 140B forms _{an angle θ 2 with respect to the reference direction D.} .. Further, the wavelength stabilizing element 40C (third wavelength stabilizing element) arranged on the most downstream side is arranged so that the reflecting surface 140C forms _{an angle θ 3 with respect to the reference direction D.}

Here, θ ₂ is _{larger than θ 1} and is a positive value in this embodiment (θ ₂ > θ ₁ = 0). θ ₃ is _{smaller than θ 1} and is a negative value in this embodiment (θ ₃ <θ ₁ = 0). Further, in the present embodiment, θ ₂ ≤ 2 _{θ H} and θ ₃ ≥ -2 _{θ H.}

For example, when the resin (not shown) fixing the mirror 27 located on the upstream side of the wavelength stabilizing elements 40A, 40B, 40C expands and contracts due to a temperature change or the like, the position and angle of the mirror 27 change. As shown in FIG. 6, it is conceivable that the optical path M'of the laser beam L'reflected by the mirror 27 deviates from the optical path M (see FIG. 5) of the original laser beam L by an angle α. Hereinafter, the angle at which the optical path M'of the laser beam L'reflected by the mirror 27 deviates from the optical path M of the original laser beam L is referred to as the "displacement angle" of the laser beam L'.

If the displacement angle α of the laser beam L'is within the effective angle range of the wavelength stabilizing element 40A described above, that is, within the range _{from −θ H} to + θ _H , the reflecting surface 140A of the wavelength stabilizing element 40A and the semiconductor laser. Since an external resonator can be formed between the element 24 and the emission end surface 124B, the wavelength of the laser beam L'can be narrowed by the wavelength stabilizing element 40A. However, when the displacement angle α of the laser beam L'exceeds the effective angle range of the wavelength stabilizing element 40A, as shown in FIG. 6, the reflecting surface 140A of the wavelength stabilizing element 40A and the emitting end surface 124B of the semiconductor laser element 24 It becomes impossible to form an external resonator between them. That is, the wavelength stabilizing element 40A can narrow the wavelength of the laser beam L'with a displacement angle α within the _{effective angle range (range from −θ H} to + θ _H). The wavelength of the laser beam L'with a displacement angle α smaller than −θ _{H and a displacement angle α larger than + θ H cannot be narrowed.}

On the other hand, in the present embodiment, since the reflection surface 140B of the wavelength stabilizing element 40B is arranged so as to form _{an angle θ 2 with respect to the reference direction D perpendicular to the optical axis of the original laser beam L, the wavelength is stabilized.} The effective angle range of the element 40B is a range from (θ ₂ − θ _H ) to (θ ₂ + θ _H ). Here, since 2 _{θ H} ≧ θ ₂ > θ ₁ = 0, even if the displacement angle α of the laser beam L'is larger than the effective angle range of the wavelength stabilizing element 40A (that is, it becomes larger than _{θ H).} However, if it is within the effective angle range of the wavelength stabilizing element 40B (that is, if it is (θ ₂ + θ _H ) or less), as shown in FIG. 6, the reflecting surface 140B of the wavelength stabilizing element 40B and the semiconductor laser. An external resonator can be formed between the element 24 and the emission end surface 124B, and the wavelength of the laser beam L'can be narrowed.

_{Similarly, since the reflection surface 140C of the wavelength stabilizing element 40C is arranged so as to form an angle θ 3} with respect to the reference direction D perpendicular to the optical axis of the original laser beam L, the wavelength stabilizing element 40C is effective. The angular range is from (θ ₃ − θ _H ) to (θ ₃ + θ _H ). Here, since -2θ _H ≤ θ ₃ <θ ₁ = 0, even if the displacement angle α of the laser beam L'is smaller than the effective angle range of the wavelength stabilizing element 40A (that is, than _{−θ H).} If it is within the effective angle range of the wavelength stabilizing element 40B (that is, if it is (that is, (θ ₃ − θ _H ) or more), the reflecting surface 140C of the wavelength stabilizing element 40C and the emission of the semiconductor laser element 24 are emitted. An external resonator can be formed with the end face 124B to narrow the wavelength of the laser beam L'.

FIG. 7 is a schematic diagram showing an example of the effective angle range of such wavelength stabilizing elements 40A, 40B, 40C. As can be seen from FIG. 7, _{the wavelength of the laser beam L'where the displacement angle α is in the range of −θ H} to + θ _H is narrowed by the wavelength stabilizing element 40A, and the displacement angle α is from + θ _H (θ _2). The wavelength of the laser beam L'in the range up to + θ _H ) is narrowed by the wavelength stabilizing element 40B, and the displacement angle α is in the range _{from (θ 3} −θ _H ) to −θ _H. The wavelength of is narrowed by the wavelength stabilizing element 40C.

As described above, the effective angle range of one wavelength stabilizing element 40 is a range from −θ _H to + θ _H , but in the present embodiment, as described above, the three wavelength stabilizing elements 40A, 40B, 40C. By arranging the reflecting surfaces 140A, 140B, 140C at different angles with respect to the optical axis of the laser beam, the effective angle range of the wavelength stabilizing elements 40A, 40B, 40C as a whole can be changed from (θ ₃ − θ _H ) to (θ 3 − θ H). It can be expanded to the range of θ ₂ + θ _H). Therefore, the laser module 10 in the present embodiment can stably output the laser light having a narrowed wavelength band.

Further, since the fiber laser apparatus 1 shown in FIG. 1 uses the laser light output from the laser module 10 as the excitation light, the excitation light having a stable wavelength is supplied to the amplification optical fiber 2 and is therefore stable. The laser beam can be amplified.

Here, as shown in FIG. _{8, θ 1 = 0, θ} 2 = 2θ H, if θ ₃ = -2θ _H, wavelength stabilization element 40A, 40B, the effective angular range of the entire 40C maximize be able to. At this time, the effective angle range of the wavelength stabilizing elements 40A, 40B, and 40C as a whole ranges from -3θ _H to + 3θ _H.

Generally, the active layer 124 of the semiconductor laser device 24 is shorter in the direction along the first axis than in the direction along the slow axis. Therefore, the laser beam emitted from the semiconductor laser element 24 is more likely to deviate from the effective angle range of the wavelength stabilizing element 40 in the direction along the first axis than in the direction along the slow axis. From this point of view, as in the present embodiment, setting the above-mentioned reference direction D to the direction (Z direction) along the first axis of the laser beam L is better than setting the reference direction D to the direction along the slow axis. It is effective.

Further, it is considered that the effective angle range of the wavelength stabilizing element 40 on the downstream side thereof is narrowed due to the influence of the optical component on the optical path of the laser light emitted from the semiconductor laser element 24, and thus such an influence. Of the wavelength stabilizing elements 40A, 40B, 40C, the wavelength stabilizing element having the smallest absolute value of the angle formed by the reflecting surfaces 140A, 140B, 140C with respect to the reference direction D (in this embodiment, It is preferable to arrange the wavelength stabilizing element 40A) on the most upstream side.

In the above-described embodiment, the reflecting surface 140A of the wavelength stabilizing element 40A is parallel to the reference direction D, and the angle θ ₁ formed by the reflecting surface 140A with respect to the reference direction D is set to 0, but the angle θ ₁ is set to 0. It does not necessarily have to be 0, and θ ₁ can be any value in the range from −θ _H to + θ _H. In this case, in order to obtain the above-mentioned effect,
θ ₃ <θ ₁ <θ ₂
θ ₂ −θ ₁ ≤ 2θ _H
θ ₁ −θ ₃ ≤ 2θ _H
Should be satisfied.

Further, although the laser module 10 in the above-described embodiment includes three wavelength stabilizing elements 40A, 40B, 40C, if at least two of these wavelength stabilizing elements 40A, 40B, 40C are provided. good. For example, the laser module 10 may include only the wavelength stabilizing element 40A and the wavelength stabilizing element 40B. Also in this case, the effective angle range of the wavelength stabilizing element 40A and the wavelength stabilizing element 40B as a whole can be expanded _{from (θ 1} − θ _H ) to (θ ₂ + θ _H).

Further, in the embodiment in which the laser module 10 includes only the wavelength stabilizing element 40A and the wavelength stabilizing element 40B, θ _{2 is set} to an arbitrary value in the range of _{−θ H} to + θ _{H , and θ 1 is set} to θ ₂ −θ. It can also be a negative value that satisfies ₁ ≦ 2θ _H. Also in this case, the effective angle range of the wavelength stabilizing element 40A and the wavelength stabilizing element 40B as a whole can be expanded _{from (θ 1} − θ _H ) to (θ ₂ + θ _H).

Further, it is possible to increase the number of wavelength stabilizing elements 40 to four or more. The number of wavelength stabilizing elements 40 is increased by arranging the reflecting surfaces 140 of each wavelength stabilizing element 40 so as to be offset with respect to the reference direction D so as to expand the effective angle range of the entire wavelength stabilizing element 40. This makes it possible to further expand the effective angle range of the entire wavelength stabilizing element 40.

In the above-described embodiment, the wavelength stabilizing elements 40A, 40B, 40C are arranged between the laser generation unit 20 and the first axis condensing lens 51, but the positions of the wavelength stabilizing elements 40A, 40B, 40C are It is not limited to this. For example, in the laser module 210 shown in FIG. 9, wavelength stabilizing elements 40A, 40B, and 40C are arranged between the fast-axis collimating lens 25 and the slow-axis collimating lens 26 corresponding to the respective semiconductor laser elements 24. .. In this case, even if the optical path of the laser beam L shifts due to the expansion and contraction of the resin fixing the first axis collimating lens 25, the wavelength of the laser beam L is narrowed by these wavelength stabilizing elements 40A, 40B, 40C. It is possible to make a band.

In the above-described embodiment, a plurality of semiconductor laser elements are mounted on the laser generation unit 20, but at least one semiconductor laser element 24 may be mounted on the laser generation unit 20.

Further, the fiber laser apparatus 1 shown in FIG. 1 is provided with excitation light sources 4A and 4B and optical combiners 5A and 5B on both the high reflection portion 9A side and the low reflection portion 9B side of the optical resonator 3, and is bidirectional. Although it is an excitation type fiber laser apparatus, the excitation light source and the optical combiner may be installed only on either the high reflection portion 9A side or the low reflection portion 9B side.

Further, as the fiber laser device, in addition to the configuration as shown in FIG. 1, a MOPA fiber laser device that amplifies the seed light from the seed light source by using the excitation light from the excitation light source is known. The laser module can also be used as an excitation light source for such a MOPA fiber laser device.

Although the preferred embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment and may be implemented in various different forms within the scope of the technical idea.

As described above, according to the first aspect of the present invention, there is provided a laser module capable of stably outputting a laser beam having a narrowed wavelength band. This laser module includes an optical fiber, at least one semiconductor laser element that emits laser light from an emission end face, at least one condenser lens that collects the laser light and couples it to the optical fiber, and the laser light. It comprises at least two wavelength stabilizing elements having a reflective surface located on the optical path of. The at least two wavelength stabilizing elements are arranged with the reflecting surface when the reflecting surface is arranged at an angle within the range of _{−θ H} to + θ _{H with} respect to the reference direction perpendicular to the optical axis of the laser beam. An external resonator is formed between the emission end face of the at least one semiconductor laser element and the wavelength of the laser light is narrowed to a specific wavelength. The at least two wavelength stabilizing elements include a first wavelength stabilizing element in which the reflecting surface is arranged at an _{angle θ 1 with respect to the reference direction, and the reflecting surface having the reflecting surface at an angle θ 1 with respect to the reference direction.} It includes a second wavelength stabilizing element arranged at a larger angle θ _2. At least one of _{θ 1} and θ ₂ is in the range _{from −θ H} to + θ _{H , and θ 2} −θ ₁ ≦ 2θ _H.

The effective angle range of one wavelength stabilizing element is in the range of −θ _H to + θ _H , but the reflection surfaces of the first wavelength stabilizing element and the second wavelength stabilizing element are at different angles with respect to the reference direction. By arranging with, the effective angle range of the wavelength stabilizing element as a whole can be expanded from the range from _{−θ H} to + θ _H. Therefore, it is possible to stably output the laser beam having a narrowed wavelength.

In order to maximize the effective angle range of the first wavelength stabilizing element and the second wavelength stabilizing element as a whole, it is preferable that _{θ 1} = 0 and θ ₂ = 2 _{θ H.}

Further, when _{the absolute value of θ 1} is smaller than the absolute value of θ ₂ , the first wavelength stabilizing element is located upstream of the second wavelength stabilizing element in the optical path of the laser beam. Is preferable. According to such a configuration, it is possible to reduce the influence of the optical component on the optical path of the laser beam emitted from the semiconductor laser element on the effective angle range of the wavelength stabilizing element.

The at least two wavelength stabilizing elements may further include a third wavelength stabilizing element in which the _{reflecting surface is arranged at an angle θ 3} smaller than the _{angle θ 1 with} respect to the reference direction. In this case, θ ₁ − θ ₃ ≦ 2 θ _H. In this way, by arranging the reflection surfaces of the first wavelength stabilizing element, the second wavelength stabilizing element, and the third wavelength stabilizing element at different angles with respect to the reference direction, the wavelength stabilizing element The effective angle range as a whole can be further expanded from the range from _{−θ H} to + θ _H. Therefore, the laser beam having a narrowed wavelength can be output more stably.

In order to maximize the effective angle range of the first wavelength stabilizing element and the third wavelength stabilizing element as a whole, it is preferable that _{θ 1} = 0 and θ ₃ = -2 _{θ H.}

Further, when the absolute value of _{θ 1 is smaller than the absolute value of θ 2 and} the absolute value of θ ₃ , the first wavelength stabilizing element is the second wavelength stabilizing element in the optical path of the laser beam. And, it is preferable that it is located on the upstream side of the third wavelength stabilizing element. According to such a configuration, it is possible to reduce the influence of the optical component on the optical path of the laser beam emitted from the semiconductor laser element on the effective angle range of the wavelength stabilizing element.

In general, the active layer of a semiconductor laser device is shorter in the direction along the first axis than in the direction along the slow axis. Therefore, the laser beam emitted from the semiconductor laser element is more likely to deviate from the effective angle range of the wavelength stabilizing element in the direction along the first axis than in the direction along the slow axis. From this point of view, the reference direction is preferably a direction along the first axis of the laser beam.

According to the second aspect of the present invention, there is provided a fiber laser apparatus capable of stably amplifying a laser beam. The fiber laser apparatus includes an excitation light source including the above-mentioned laser module, and an amplification optical fiber having a core optically connected to the above-mentioned optical fiber of the above-mentioned laser module and to which rare earth element ions are added.

According to such a configuration, since the wavelength of the laser light output from the laser module used as the excitation light source is stable, the laser light can be stably amplified.

1 Fiber laser device 2 Amplification optical fiber 3 Optical resonator 4A, 4B Excitation light source 5A, 5B Optical combiner 6 Delivery fiber 7 Laser output unit 8A, 8B Optical fiber 9A High reflection unit 9B Low reflection unit 10,210 Laser module 12 Body 14 Optical fiber 16 Fiber holder 20 Laser generator 21 Pedestal 22A-22F Step 23 Submount 24 Semiconductor laser element 25 First axis collimating lens 26 Slow axis collimating lens 27 Mirror 40A (1st) Wavelength stabilizing element 40B (1st) Second) wavelength stabilizing element 40C (third) wavelength stabilizing element 51 First axis condensing lens 52 Slow axis condensing lens 124 Active layer 124A Highly reflective end face 124B Emitting end face 140A, 140B, 140C Reflecting surface D Reference direction L laser light

Claims (8)

With optical fiber
At least one semiconductor laser device that emits laser light from the emission end face,
At least one condensing lens that condenses the laser light and couples it to the optical fiber.
At least two wavelength stabilizing elements having a reflecting surface located on the optical path of the laser light, _{from −θ H} to + θ _{H with} respect to the reference direction in which the reflecting surface is perpendicular to the optical axis of the laser light. When arranged at an angle within the range, an external resonator can be formed between the reflection surface and the emission end surface of the at least one semiconductor laser element to narrow the wavelength of the laser light to a specific wavelength. With at least two wavelength stabilizing elements configured as such,
The at least two wavelength stabilizing elements are
A first wavelength stabilizing element in which the _{reflecting surface is arranged at an angle θ 1} with respect to the reference direction,
The reflecting surface includes a second wavelength stabilizing element arranged at an _{angle θ 2} larger than the _{angle θ 1 with} respect to the reference direction.
At least one of _{θ 1} and θ ₂ is in the range _{−θ H} to + θ _H,
θ ₂ −θ ₁ ≤ 2θ _H
Is,
Laser module. The laser module according to claim 1, wherein θ ₁ = 0 and θ ₂ = 2 _{θ H.} The absolute value of θ ₁ is smaller than the absolute value of θ _2,
The first wavelength stabilizing element is located upstream of the second wavelength stabilizing element in the optical path of the laser beam.
The laser module according to claim 1 or 2. The at least two wavelength stabilizing elements further include a third wavelength stabilizing element in which the _{reflecting surface is arranged at an angle θ 3} smaller than the _{angle θ 1 with} respect to the reference direction.
θ ₁ −θ ₃ ≤ 2θ _H
Is,
The laser module according to any one of claims 1 to 3. The laser module according to claim 4, wherein θ ₁ = 0 and θ ₃ = -2 _{θ H.} The absolute value of θ ₁ is smaller than the absolute value of _{θ 2 and} the absolute value of θ _3.
The first wavelength stabilizing element is located upstream of the second wavelength stabilizing element and the third wavelength stabilizing element in the optical path of the laser beam.
The laser module according to claim 4 or 5. The laser module according to any one of claims 1 to 6, wherein the reference direction is a direction along the first axis of the laser beam. An excitation light source including the laser module according to any one of claims 1 to 7.
A fiber laser apparatus comprising an optical fiber for amplification optically connected to the optical fiber of the laser module and having a core to which rare earth element ions are added.

Images