WO2018173109A1

WO2018173109A1 - Laser oscillator, and laser processing device

Info

Publication number: WO2018173109A1
Application number: PCT/JP2017/011160
Authority: WO
Inventors: 大嗣森田; 智毅桂; 裕章黒川
Original assignee: 三菱電機株式会社
Priority date: 2017-03-21
Filing date: 2017-03-21
Publication date: 2018-09-27
Also published as: JPWO2018173109A1

Abstract

This laser oscillator (100-1) is characterized by being provided with: a semiconductor laser stack (10) which is formed by stacking, in a fast axis direction, a plurality of semiconductor laser arrays (11) having, provided in a slow axis direction, a plurality of light-emission points (12) for generating beams having different wavelengths; a plurality of fibres (21) which are attached to each of the plurality of light-emission points (12); a wavelength dispersion element (33); and a condensing optical element (32) which condenses the beams emitted from the plurality of fibres (21) so as to superpose the beams on the wavelength dispersion element (33). The laser oscillator is further characterized in that the wavelength dispersion element (33) is installed in a position where the plurality of beams are superposed by the condensing optical element (32), and combines and outputs the plurality of condensed fast-axis-direction and slow-axis-direction beams.

Description

Laser oscillator and laser processing apparatus

The present invention relates to a laser oscillator and a laser processing apparatus including a laser stack composed of a plurality of laser arrays.

The semiconductor laser stack is a laser oscillator configured by stacking a plurality of semiconductor laser arrays. A plurality of light emitting points are arranged in one semiconductor laser array. A semiconductor laser stack using a plurality of semiconductor laser arrays can obtain a high-power laser as compared with a semiconductor laser stack using a single semiconductor laser array, and is of the order of several hundreds [W] to several [kW]. It is one of the cheapest laser oscillators in the high-power laser field. However, since the semiconductor laser stack has a structure in which a plurality of semiconductor laser arrays are simply arranged in the fast axis direction, the beam output from each of the plurality of light emitting points of the semiconductor laser array spreads, and the beam quality decreases. In general, BPP (Beam Parameter Products) is used for evaluation of beam quality, and BPP is a numerical value represented by the product of the beam divergence angle and the minimum beam diameter. The smaller the BPP beam, the narrower the beam, and the higher the energy density of light on the processed surface, so that it is suitable for laser processing. Therefore, a semiconductor laser stack with low beam quality is not suitable for applications such as sheet metal cutting and welding that require high beam quality, and is limited to applications such as cladding and surface treatment.

Japanese Patent Application Laid-Open No. H10-228561 discloses a technique of increasing the beam brightness by wavelength-coupling a laser array composed of a plurality of stacked semiconductors with an external resonator.

Special table 2012-508453 gazette

However, since the wavelength combination of the beam disclosed in Patent Document 1 is performed only in the slow axis direction, there are a plurality of beams that do not contribute to the improvement of the brightness in the fast axis direction, so that the brightness of the beam is sufficiently improved. There was a problem that it was not possible.

The present invention has been made in view of the above, and an object thereof is to obtain a laser oscillator capable of improving the luminance of a beam.

In order to solve the above-described problems and achieve the object, a laser oscillator according to the present invention is formed by laminating a plurality of laser arrays in the fast axis direction, each having a plurality of light emitting points that generate beams having different wavelengths. Laser stack configured, a plurality of fibers attached to each of a plurality of light emitting points, a wavelength dispersion element, and an optical element for condensing beams emitted from the plurality of fibers so as to overlap on the wavelength dispersion element The wavelength dispersion element is installed at a position where a plurality of beams are superimposed by an optical element, and combines and outputs a plurality of condensed beams in the fast axis direction and the slow axis direction. To do.

The laser oscillator according to the present invention has an effect that the brightness of the beam can be improved.

Configuration diagram of laser oscillator according to Embodiment 1 Configuration diagram of laser oscillator according to second embodiment Configuration of Laser Oscillator according to Embodiment 3 Configuration of Laser Oscillator according to Embodiment 4 The figure which shows the structural example of the fiber Bragg grating (Fiber Bragg Grating: FBG) extending | stretching mechanism shown in FIG. Configuration diagram of laser oscillator according to embodiment 5

Hereinafter, a laser oscillator and a laser processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a laser oscillator according to the first embodiment. The laser oscillator 100-1 according to the first embodiment includes a semiconductor laser configured by laminating a plurality of semiconductor laser arrays 11 having a plurality of light emitting points 12 that generate beams having different wavelengths in the slow axis direction in the fast axis direction. A stack 10; a plurality of fibers 21 each having one end attached to each of a plurality of light emitting points 12; a plurality of wavelength dispersion elements 33 that combine and output a plurality of condensed beams in a fast axis direction and a slow axis direction; And a condensing optical element 32 which is an optical element that condenses the oscillation beam 31 emitted from each of the fibers 21 so as to be superimposed on the wavelength dispersion element 33. Each of the plurality of fibers 21 transmits a beam emitted from the light emitting point 12.

The semiconductor laser stack 10 is configured by stacking a plurality of semiconductor laser arrays 11. The semiconductor laser array 11 has a plurality of light emitting points 12, and each of the plurality of fibers 21 is arranged so that beams emitted from each of the plurality of light emitting points 12 are coupled to the core of the fiber 21. At this time, the coupling efficiency can be improved by forming the end face shape of the fiber 21 into a lens shape. Further, the coupling efficiency can be improved by arranging a small optical element between the light emitting point 12 and the fiber 21.

In FIG. 1, in the right-handed XYZ coordinates, the arrangement direction of the plurality of light emitting points 12 included in one semiconductor laser array 11 is the X-axis direction, the stacking direction of the plurality of semiconductor laser arrays 11 is the Y-axis direction, and the X-axis A direction perpendicular to both the direction and the Y-axis direction is taken as a Z-axis direction. The X-axis direction is equal to the slow axis, and the Y-axis direction is equal to the fast axis. The slow axis is equal to the direction in which a plurality of light emitting points 12 provided in one semiconductor laser array 11 are arranged. The fast axis is an axis orthogonal to the slow axis and is equal to the direction in which the plurality of semiconductor laser arrays 11 are stacked.

The other ends of the plurality of fibers 21 are routed toward the condensing optical element 32, and the termination regions 21b of the plurality of fibers 21 are arranged in parallel on the same plane, that is, on the XZ plane of FIG. At this time, it is desirable that the emission ends 21a of the plurality of fibers 21 have the same position in the Z-axis direction.

In the laser oscillator 100-1 configured as described above, the beams emitted from the respective light emission points 12 of the semiconductor laser stack 10 are emitted as the oscillation beam 31 from the emission end 21 a of the fiber 21. The plurality of oscillation beams 31 are superimposed on the wavelength dispersion element 33 by the condensing optical element 32, and the wavelength dispersion element 33 is installed at a position where the plurality of oscillation beams 31 are superimposed by the condensing optical element 32, A plurality of oscillation beams 31 condensed by the condensing optical element 32 are output as a combined beam 34 having one optical axis.

Hereinafter, the principle of combining a plurality of oscillation beams 31 into one by the wavelength dispersion element 33 will be briefly described.

Since the plurality of fibers 21 arranged in the XZ plane are arranged apart from each other in the X-axis direction, the oscillation beams 31 emitted from the plurality of fibers 21 are collected from different positions on the XZ plane. The light enters the optical optical element 32. Therefore, the beams collected by the condensing optical element 32 are incident on the wavelength dispersion element 33 at different angles α1 to α9 in the XZ plane. Angles α1 to α9 are incident angles of the plurality of outgoing beams with respect to the normal line of the surface of the wavelength dispersion element 33, respectively.

The oscillation beam 31 incident on the wavelength dispersion element 33 is diffracted by the wavelength dispersion element 33. When the wavelength dispersion element 33 is a diffraction grating, the diffraction angle β of the wavelength dispersion element 33 can be obtained from Nλ = sin α + sin β. N is the groove number density, and λ is the oscillation wavelength.

As a specific example, when the groove density N is 1850 [lines / mm], the oscillation wavelength λe is 980 [nm], and the incident angle α3 is 65.03 degrees, the diffraction angle β is Nλ = sin α + sin β. It is 65.03 degrees. Here, the overall width D in the X-axis direction of each of the plurality of fibers 21 is 8 [mm], the separation distance d between adjacent fibers 21 is 1 [mm], and the focal length of the condensing optical element 32 is 100 [mm]. mm], the distance L from the emission end 21a of the fiber 21 to the condensing optical element 32 is 100 [mm], and the oscillation wavelengths of the plurality of oscillation beams 31 are λa to λi. Furthermore, the oscillation wavelength λa is 988.7 [nm], the oscillation wavelength λb is 986.6 [nm], the oscillation wavelength λc is 984.4 [nm], the oscillation wavelength λd is 982.3 [nm], and the oscillation wavelength λe is 980.0 [nm], oscillation wavelength λf of 977.7 [nm], oscillation wavelength λg of 975.3 [nm], oscillation wavelength λh of 972.9 [nm], oscillation wavelength λi of 970.5 [nm] And In this case, the diffraction angle β is 65.03 degrees, and the outgoing beam superimposed on the wavelength dispersion element 33 is combined by the wavelength dispersion effect of the wavelength dispersion element 33 into one combined beam 34.

The combined beam 34 is transmitted by a processing head via a transmission fiber (not shown), and is irradiated onto the processing object from the processing head.

As described above, in the laser oscillator 100-1 according to the first embodiment, laser beams emitted from the plurality of light emitting points 12 included in each of the plurality of semiconductor laser arrays 11 constituting the semiconductor laser stack 10 can be output as the combined beam 34. Therefore, compared with the case where the beam combining method disclosed in Patent Document 1 is used, a laser beam with high output and high brightness can be obtained. Further, by using a laser processing apparatus including the laser oscillator 100-1 according to the first embodiment and a processing head (not shown), it is possible to process a processing target using a high-power and high-intensity beam.

Embodiment 2. FIG.
FIG. 2 is a configuration diagram of the laser oscillator according to the second embodiment. The difference between the laser oscillator 100-2 according to the second embodiment and the laser oscillator 100-1 according to the first embodiment is that the laser oscillator 100-2 is arranged on the optical path of the beam synthesized by the wavelength dispersion element 33. The partial reflection mirror 43 having wavelength selectivity is used. In the laser oscillator 100-2, an external resonator is configured between the light emitting point 12 and the partial reflection mirror 43.

The intracavity outgoing beam 31 a emitted from each of the plurality of fibers 21 is condensed by the condensing optical element 32 and superimposed on the wavelength dispersion element 33. Each of the plurality of intracavity beams 31 a diffracted by the wavelength dispersion element 33 returns to the light emitting point 12 only when it enters the partial reflection mirror 43 perpendicularly. As a result, laser oscillation occurs between the light emitting point 12 and the partial reflection mirror 43. Therefore, in the laser oscillator 100-2, the oscillation wavelengths λa to λi of each of the plurality of intracavity outgoing beams 31a are selected so as to enter the partial reflection mirror 43 perpendicularly.

In the laser oscillator 100-2, each of the plurality of intracavity outgoing beams 31a is configured to be superimposed on the wavelength dispersive element 33. Therefore, the plurality of intracavity outgoing beams 31a are combined to form a single beam. The intracavity coupled beam 42 is obtained, and the intracavity coupled beam 42 is extracted as an output beam 44.

In the laser oscillator 100-2 according to the second embodiment, it is not necessary to prepare elements having different refractive index distributions such as FBG and VBG, which will be described later, according to each light emitting point. The assembly time of the oscillator 100-2 is shortened, and the manufacturing cost of the laser oscillator 100-2 can be reduced.

Embodiment 3 FIG.
FIG. 3 is a configuration diagram of a laser oscillator according to the third embodiment. The difference between the laser oscillator 100-3 according to the third embodiment and the laser oscillator 100-1 according to the first embodiment is that, in the laser oscillator 100-3, an FBG 23 is provided for each of the plurality of fibers 21. It is. In the laser oscillator 100-3, the wavelengths of the beams emitted from the plural light emitting points 12 may be the same, or the wavelengths of the beams emitted from the plural light emitting points 12 may be different.

The FBG 23 is an element in which a periodic refractive index change is formed inside the glass. The refractive index change works as a diffraction grating, and can reflect only light having a wavelength that satisfies the Bragg reflection condition created by the period of the diffraction grating. By using the FBG 23 as a partial reflection mirror of the external resonator, it is possible to oscillate at a specific wavelength. In the third embodiment, since the refractive index changes of the plurality of FBGs 23 are formed at different periods, each of them can be oscillated at different wavelengths.

In the third embodiment, the wavelength of the oscillation beam 31 is fixed using the FBG 23. However, the wavelength fixing method is not limited to this, and VBG (Volume Bragg Grating), DBR (Distributed Bragg Reflector) or DFB (Distributed Feedback) may be used.

VBG, like FBG23, is an element in which a periodic refractive index change is formed inside the glass. When using VBG, VBG is arrange | positioned between the light emission point 12 and the fiber 21, or VBG is arrange | positioned at the back surface of the semiconductor laser stack 10. FIG. As a result, the oscillation wavelength is fixed. The DBR forms a diffraction grating structure on the extension of the waveguide of the active layer at the light emitting point 12, and the oscillation wavelength is fixed by the wavelength selectivity of the diffraction grating. The DFB is formed by forming diffraction gratings on the upper and lower surfaces of the active layer of the light emitting point 12, and the oscillation wavelength is fixed by the wavelength selectivity of the diffraction grating. However, when a plurality of VBGs, DBRs, or DFBs are used in the laser oscillator 100-3 of the third embodiment, the intervals between the diffraction gratings need to be different.

Embodiment 4 FIG.
FIG. 4 is a configuration diagram of a laser oscillator according to the fourth embodiment. In the laser oscillator 100-4 according to the fourth embodiment, a plurality of FBG stretching mechanisms 51 are used in addition to the configuration shown in FIG. Each of the plurality of FBG stretching mechanisms 51 is attached to each of the plurality of fibers 21. The FBG stretching mechanism 51 is attached across the FBG 23 of FIG. The effective refractive index n and the diffraction grating period Λ can be changed inside each of the plurality of FBGs 23 by the FBG stretching mechanism 51. Details of a configuration example of the FBG stretching mechanism 51 will be described later.

Examples of the FBG stretching mechanism 51 include one that stretches the FBG 23 by physically extending the fiber 21, and one that stretches the FBG 23 by applying heat to the fiber 21. Specifically, when the FBG stretching mechanism 51 causes distortion in the formation location of the FBG 23 or a temperature change occurs in the formation location of the FBG 23, the effective refractive index and the diffraction grating period of the FBG 23 change. The reflection wavelength changes. Accordingly, the oscillation wavelength of the oscillation beam 31 emitted from each of the plurality of fibers 21 changes.

Thus, it is not necessary to form the FBGs 23 having different diffraction grating periods in each of the plurality of fibers 21, and the types of FBGs 23 to be manufactured can be reduced. Therefore, the manufacturing cost of the laser oscillator can be reduced as compared with the laser oscillator provided with the FBG 23 each having a different diffraction grating period. In the fourth embodiment, since the oscillation wavelength can be adjusted by the FBG stretching mechanism 51, the manufacturing error of the FBG 23 can be allowed, the yield of the FBG 23 is improved, and the manufacturing cost of the laser oscillator provided with the FBG 23 can be reduced.

When the effective refractive index and the diffraction grating period of the FBG 23 are changed by applying physical strain, the oscillation wavelength can be changed around 5 [nm]. In the first embodiment, the entire oscillation wavelength width corresponding to the difference between the oscillation wavelength λa and the oscillation wavelength λi is 18.2 [nm]. In this case, it is sufficient to form three to four types of FBGs 23. It will be. When increasing the output from several hundreds [W] to several [kW], the number of light emitting points 12 included in one semiconductor laser array 11 is several tens to several hundreds. Can be covered by four types of FBG23.

FIG. 5 is a diagram showing a configuration example of the FBG stretching mechanism shown in FIG. FIG. 5 illustrates an FBG stretching mechanism 51 that causes strain at the formation site of the FBG 23 by physically pulling the fiber 21.

The FBG stretching mechanism 51 shown in FIG. 5 includes a plate-like glass substrate 51d arranged in parallel with the fiber 21, a fixing member 51b installed on the glass substrate 51d by an adhesive 51a, and an adhesive 51a from the fixing member 51b. And an adjustment member 51c installed at a position separated by a certain distance. The fixing member 51b and the adjustment member 51c are arranged so as to sandwich the FBG 23. The fiber 21 on one end side of the FBG 23 is fixed to the fixing member 51b by an adhesive 51a. The fiber 21 on the other end side of the FBG 23 is fixed to the adjustment member 51c with an adhesive 51a. An example of the material of the fixing member 51b and the adjustment member 51c is glass. This is because it is desirable to align the thermal expansion coefficients of the fiber 21, the fixing member 51b, and the adjusting member 51c.

When adjusting the oscillation wavelength in the FBG stretching mechanism 51 configured as described above, the adjustment member 51c is slid with a member extending from a stage (not shown), and the adjustment member 51c is bonded to the adhesive 51a when a specific oscillation wavelength is reached. Is fixed to the glass substrate 51d. An example of the stage is an electric stage that is driven in one axial direction. In the FBG stretching mechanism 51 shown in FIG. 5, distortion can be generated at the location where the FBG 23 of the fiber 21 is formed simply by adjusting the position of the adjustment member 51 c, so that a complicated mechanism such as a ball screw mechanism is used. The oscillation wavelength can be adjusted without using it. Therefore, the manufacturing cost of the laser oscillator can be reduced, and even when the laser oscillator is used for a long time, the fluctuation of the oscillation wavelength is small, and a high-power and high-luminance beam can be maintained.

Embodiment 5 FIG.
FIG. 6 is a configuration diagram of a laser oscillator according to the fifth embodiment. The difference between the laser oscillator 100-2 according to the second embodiment and the laser oscillator 100-5 according to the fifth embodiment is that, in the laser oscillator 100-5, the partial reflection mirror 43 is omitted and the wavelength dispersion is a diffraction grating. The element 33 is arranged in a Littrow arrangement. In the Littrow arrangement, the number of grooves and the installation angle of the diffraction grating are set so that the diffraction angles of the second-order diffracted lights of the plurality of laser beams and the incident angles of the plurality of laser beams coincide with each other at an assumed wavelength. Refers to the arrangement. In the laser oscillator 100-5 including the wavelength dispersion element 33 arranged in the Littrow arrangement, the second-order diffracted light generated by the wavelength dispersion element 33 becomes feedback light that returns to the semiconductor laser stack 10 along the incident beam, and the plurality of semiconductor laser arrays 11 Resonators that operate at different wavelengths for each beam are configured between each of these and the wavelength dispersion element 33. The first-order diffracted light of the laser beam is used as the output beam of the laser oscillator 100-5.

In the laser oscillator 100-2 according to the second embodiment, an external resonator is configured between the light emitting point 12 and the partial reflection mirror 43, and partial reflection is performed on the first-order diffracted light of the laser beam generated by the wavelength dispersion element 33. A mirror 43 is installed. The beam reflected by the partially reflecting mirror 43 returns to the semiconductor laser stack 10, and the transmitted beam of the partially reflecting mirror 43 is used as the output beam of the laser oscillator 100-2.

In the laser oscillator 100-5 according to the fifth embodiment, the second-order diffracted light of the laser beam generated by the wavelength dispersion element 33 returns to the semiconductor laser stack 10. The first-order diffracted light is diffracted when the diffraction angle β of the wavelength dispersion element 33 is 0 degree. That is, the first-order diffracted light is emitted perpendicular to the diffraction grating. It is this first-order diffracted light that is used as the output beam of the laser oscillator 100-5. Even when there are a plurality of laser beams, the first-order diffracted light is emitted perpendicular to the diffraction grating, so that the plurality of laser beams can be superimposed on one beam.

As described above, in the laser oscillator 100-5 according to the fifth embodiment, the wavelength dispersion element 33 returns a part of the plurality of beams to the laser stack 10 as the first laser beam, and a part of the plurality of beams. Are output as a second laser beam having one optical axis, and the wavelength dispersion element 33 is arranged in a Littrow arrangement with respect to the first laser beam. In the fifth embodiment, since the partial reflection mirror 43 is not used, the configuration of the laser oscillator 100-5 is simplified, and not only the laser oscillator 100-5 can be miniaturized, but also the loss in the resonator is reduced. Efficient laser oscillation is possible.

The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

10 semiconductor laser stack, 11 semiconductor laser array, 12 emission point, 21 fiber, 21a exit end, 21b termination region, 23 FBG, 31 oscillation beam, 31a exit beam in resonator, 32 condensing optical element, 33 wavelength dispersion element, 34 coupled beam, 42 intracavity coupled beam, 43 partial reflection mirror, 44 output beam, 51 FBG stretching mechanism, 51a adhesive, 51b fixing member, 51c adjustment member, 51d glass substrate, 100-1, 100-2, 100-3, 100-4, 100-5 laser oscillator.

Claims

A laser stack configured by laminating a plurality of laser arrays in the slow axis direction having a plurality of light emitting points that generate beams having different wavelengths from each other; and
A plurality of fibers attached to each of the plurality of light emitting points;
A wavelength dispersion element;
An optical element that focuses the beams emitted from the plurality of fibers so as to be superimposed on the wavelength dispersion element, and
The wavelength dispersive element is installed at a position where the plurality of beams are superimposed by the optical element, and combines and outputs a plurality of condensed beams in the fast axis direction and the slow axis direction. Laser oscillator.
The laser oscillator according to claim 1, further comprising a partial reflection mirror disposed on an optical path of the beam synthesized by the wavelength dispersion element and having wavelength selectivity.
A laser stack configured by laminating a plurality of laser arrays having a plurality of light emitting points in the slow axis direction in the fast axis direction;
A plurality of fibers attached to each of the plurality of light emitting points;
A wavelength dispersion element;
An optical element that focuses the beams emitted from the plurality of fibers so as to be superimposed on the wavelength dispersion element, and
The wavelength dispersion element is installed at a position where the plurality of beams are superimposed by the optical element, and combines and outputs a plurality of condensed beams in the fast axis direction and the slow axis direction,
The plurality of fibers have wavelength selectivity;
The laser oscillator according to claim 1, wherein the wavelength selectivity is generated by a diffraction grating formed inside the plurality of fibers.
A laser stack configured by laminating a plurality of laser arrays having a plurality of light emitting points in the slow axis direction in the fast axis direction;
A plurality of fibers attached to each of the plurality of light emitting points;
A wavelength dispersion element;
An optical element that focuses the beams emitted from the plurality of fibers so as to be superimposed on the wavelength dispersion element, and
The wavelength dispersion element is installed at a position where the plurality of beams are superimposed by the optical element, and combines and outputs a plurality of condensed beams in the fast axis direction and the slow axis direction,
Each of the plurality of fibers is provided with a fiber Bragg grating.
A drawing mechanism for drawing the fiber Bragg grating;
The laser oscillator according to claim 4, wherein the drawing mechanism extends the fiber Bragg grating by physically extending the fiber.
A drawing mechanism for drawing the fiber Bragg grating;
The laser oscillator according to claim 4, wherein the drawing mechanism extends the fiber Bragg grating by applying heat to the fiber.
The wavelength dispersion element returns a part of the plurality of beams as a first laser beam to the laser stack, and outputs a part of the plurality of beams as a second laser beam having one optical axis,
The laser oscillator according to claim 1, wherein the wavelength dispersion element is arranged in a Littrow arrangement with respect to the first laser beam.
A laser processing apparatus comprising the laser oscillator according to any one of claims 1 to 7.