JP6522166B2 - Laser device - Google Patents

Description

  The present invention relates to a laser apparatus using a surface emitting laser as a laser light source, and more particularly to a laser apparatus suitable for use in laser processing.

  2. Description of the Related Art In recent years, Vertical Cavity Surface Emitting Lasers (VCSELs) are being widely used mainly in laser application fields such as optical communications, printers, and displays. A surface emitting laser is a type of semiconductor laser that emits a laser beam perpendicular to the substrate surface from a semiconductor substrate, and is higher than a general (single-emitter type) semiconductor laser that emits a laser beam horizontally to the substrate surface. It is attracting attention as a next-generation laser light source advantageous for integration, low power consumption, and mass production.

JP, 2006-114915, A

  Currently available surface emitting lasers have a light emitting surface of 4.7 mm × 4.7 mm, and the diameter of each beam exit formed on the light emitting surface as a two-dimensional array is 18 μm, The laser output of the single laser beam emitted therefrom is several tens mW, and the laser output of the entire two-dimensional array is at most 100 W at most, and the beam quality is not good.

  Although it is a simple solution to increase the diameter of the beam exit and increase the number in order to realize high output of the surface emitting laser, there is also a limitation, and furthermore, the diameter of the beam exit is increased. The problem is that as the number is increased, the beam quality of a single laser beam obtained in the entire two-dimensional array is degraded. For this reason, the conventional surface emitting laser can not currently be used for laser processing which requires a high power and high quality laser beam.

  The present invention has been made in view of the problems of the prior art, and provides a laser device which realizes a high output and high quality laser beam using a surface emitting laser.

  The laser device of the present invention comprises a first surface emitting laser that emits a bundle of first laser beams having a wavelength that matches or approximates a first standard wavelength, and a wavelength that matches or approximates a second standard wavelength. A second surface emitting laser for emitting a bundle of second laser beams, the first laser beam from the first surface emitting laser, and the second from the second surface emitting laser And a coupling unit that spatially multiplexes the laser beam and emits a combined laser beam, and the first and second surface emitting lasers are each formed on a semiconductor substrate and the semiconductor substrate. Active region and a plurality of light emission openings provided two-dimensionally and discretely provided on the active region, each of the light emission openings being perpendicular or oblique to the substrate surface of the semiconductor substrate Match the given standard wavelength in the direction A surface emitting laser element for inducing and emitting light having a similar wavelength, and light emission from the surface emitting laser element for extracting a single laser beam by resonant amplification of the light induced and emitted from each of the light emission ports And an output mirror disposed at a position away from and facing the mouth.

  In the above configuration, the spread angle of the single laser beam obtained from each light emission port is reduced by arranging the output mirror of the laser resonator at a position separated from the light emission port of the surface emitting laser element and facing it. Even if the diameter of the light emission port is increased and the number is increased, the overlapping or mutual interference between single laser beams is minimized in the single laser beam obtained by the entire surface emitting laser device. Both output and beam quality can be achieved. Furthermore, multiplication of laser output, that is, higher output can be realized more efficiently by spatially multiplex-synthesizing each single laser beam obtained from a plurality of surface emitting lasers.

  In a preferred aspect of the present invention, the first surface emitting laser has a first narrowing element for narrowing the wavelength of the single laser beam to a vicinity of a first standard wavelength, and the second surface The light emitting laser has a second narrowing element for narrowing the wavelength of the single laser beam to the vicinity of the second standard wavelength. As described above, by locking the wavelength of the single laser beam in the vicinity of the standard wavelength and narrowing the band in each of the surface emitting lasers, space coupling can be performed stably and with high accuracy. More specifically, the coupling unit may include a wavelength coupling element that multiplexes the first laser beam and the second laser beam by wavelength coupling. According to such a wavelength coupling method, it is possible to easily realize multiplication of the laser output or high output by offsetting the laser oscillation wavelength (standard wavelength) for each surface emitting laser. As another embodiment, it is also possible to multiplex and combine the first and second laser beams by polarization coupling using a polarization coupling element.

  In another preferred aspect, the narrowing element doubles as an output mirror. In this case, the narrowing element functions not only as a narrowing of the wavelength but also as a main external resonator, and emits a single laser beam having a small spread angle and stably locked to the outside.

  In another preferred embodiment, in each light emission port, any thin film provided over the active region has a property of being transparent or non-reflective to stimulated emission light. According to this configuration, the stimulated emission light deviates from the vertical direction (that is, the divergence angle is large) because the light stimulated emission on the active region is reflected by the external output mirror separated by a considerable distance. Can be effectively removed from the single laser beam.

  In another preferred aspect, the coupling unit has a wavelength coupling element that multiplexes by combining the first and second laser beams whose first and second standard wavelengths are offset from each other. . Alternatively, the coupling unit has a polarization coupling element that multiplexes and combines the first and second laser beams whose first and second standard wavelengths are the same by polarization coupling. A configuration in which the wavelength coupling element and the polarization coupling element are used in combination is also possible. With this configuration, it is possible to arbitrarily increase the number of surface emitting lasers used to increase the output of the combined laser beam, and to achieve a significant improvement in the laser output of the surface emitting laser.

  According to the laser apparatus of the present invention, with the above-described configuration and operation, it is possible to realize a high-power and high-quality laser beam using a surface emitting laser.

It is a figure which shows the whole structure of the laser processing apparatus in one Embodiment of this invention. It is a perspective view which shows the external appearance structure of the principal part of the surface emitting laser with which the said laser processing apparatus is equipped. It is a top view which shows typically the two-dimensional array of the light emission surface in the said surface emitting laser. It is sectional drawing which shows the structure of the said surface emitting laser. It is a figure which shows the wavelength-reflectance characteristic of the dichroic mirror used as a wavelength coupling element in the said laser processing apparatus. It is a figure which shows the whole structure of the laser processing apparatus in another embodiment. It is a figure which shows the structure of the principal part of the laser processing apparatus in another embodiment. It is sectional drawing which shows one modification of a structure of the said surface emitting laser. It is sectional drawing which shows the structure of the surface emitting laser in another embodiment.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the attached drawings.

[Device overall configuration]
FIG. 1 shows the configuration of a laser processing apparatus according to an embodiment of the present invention. This laser processing apparatus is a laser apparatus applicable to various laser processing such as laser welding, laser marking, laser cutting, laser drilling, etc., and plural (two in this example) surface emitting lasers (VCSELs) 10A, 10B, It comprises the coupling unit 14, the fiber transmission system 15, the laser emitting unit 16, the stage 18, the control unit 20 and the like.

  The control unit 20 controls the operation of each part and the whole of the laser processing apparatus. In particular, for each of the surface emitting lasers 10A and 10B, the control unit 20 can arbitrarily control the laser oscillation operation (continuous oscillation, pulse oscillation, and the like) through the individual laser power supplies 22A and 22B. When a scanning mechanism such as a galvano scanner is mounted on the laser emission unit 16 or when a feed mechanism such as an XY table is mounted on the stage 18, the control unit 20 synchronizes with the laser oscillation operation. Alternatively, in order to align the processing points, the operation (scanning operation, workpiece feeding operation) of the movement mechanism is controlled. The control unit 20 is also connected with an input / output device (not shown) for man-machine interface.

[Schematic Configuration and Operation of Surface-Emitting Laser]
FIG. 2 schematically shows the appearance of the main part of the surface emitting laser 10A (10B) and the state of the laser emission. The surface emitting laser 10A (10B) includes, for example, a plate-like surface emitting laser element (hereinafter referred to as "VCSEL element") 26 having a rectangular light emitting surface 24 and the light emitting surface 24 above the VCSEL element 26. A plate-like or block-like output mirror 28 disposed in parallel with an appropriate distance, and a plate-like or block-like narrowing element 29 disposed in parallel above the output mirror 28 (FIG. 1, FIG. And 4).

  As shown in FIG. 3, the light emitting surface 24 of the VCSEL element 26 is provided with a large number of light emitting ports 30 arranged discretely or in an array in a two-dimensional direction. The diameter φ of each light emission port 30 is much larger than that of a normal one, and is selected to be, for example, 100 to 1000 μm. The number of light emission ports 30 is illustrated as 16 (4 × 4) in FIG. 3 for simplification, but in practice it is several hundred or more or 1000 or more.

Of the light SB induced and emitted from the light emission ports 30 of the light emission surface 24, the light SB is reflected between the reflection mirror 34 (FIG. 4) contained in the VCSEL element 26 and the external output mirror 28 or the band narrowing element 29. Are repeated and resonantly amplified, and are taken out of the output mirror 28 as one single laser beam LB. Then, all of the single laser beams LB simultaneously taken out of the output mirror 28 are combined to form a bundle of laser beams SLB _A (SLB _B ).

In this embodiment, each single laser beam LB obtained outside the output mirror 28 has a very small divergence angle, and the aperture φ of the light emission port 30 is selected to a considerably large size (100 to 1000 μm), and the density The beam quality is improved by minimizing overlapping or mutual interference of single laser beams LB in one bundle of laser beams SLB _A (SLB _B ).

[Detailed Configuration and Operation of Surface-Emitting Laser]
FIG. 4 shows the internal configuration (cross-sectional configuration) of the surface emitting laser 10A (10B). The VCSEL device 26 uses, for example, a GaAs-based semiconductor substrate 32 as a base material, and a multi-layered reflector such as a distributed Bragg reflector (DBR) 34 or a single-layer or multi-layer lower semiconductor layer 36 formed on the semiconductor substrate 32 by a usual semiconductor process. The active layer 38, the single-layer or multi-layer upper semiconductor layer 40, and the upper electrode 42 are sequentially stacked, and the lower electrode 44 is formed on the back surface of the semiconductor substrate 32. The lower electrode 44 is generally coupled to a heat sink (not shown) for cooling via an insulator (not shown).

  The lower semiconductor layer 36 and the upper semiconductor layer 40 include a carrier injection layer. Furthermore, the upper semiconductor layer 40 also includes an antireflective film. In this embodiment, the thin films constituting the lower semiconductor layer 36 and the upper semiconductor layer 40 both have a non-reflecting property or a transmitting property with respect to light of the oscillation wavelength. The upper electrode 42 is formed with an opening 42 a for forming the light emission port 30. A portion of the active layer 38 located immediately below the light emission port 30 forms an active region 38 a.

When the surface emitting laser 10A (10B) is caused to perform laser oscillation, a driving voltage E is applied between the upper electrode 42 and the lower electrode 44 by the laser power supply 22A (22B). As a result, carriers are injected into the active layer 38 through the lower semiconductor layer 36 and the upper semiconductor layer 40, and the light SB coincident with or close to the predetermined standard wavelength λ _S from the active region 38a is stimulated emission out of the light emission opening 30 Be done.

Here, with respect to the standard wavelength λ _S and the wavelength in the vicinity thereof, the multilayer reflecting mirror 34 inside the VCSEL element 26 has a reflectance of approximately 100% in order to constitute an optical resonator, and an external output mirror 28 has a reflectance of, for example, 1 to 90%, preferably 2 to 30%. Of the light beam SB emitted by induction from the active region 38a, the light beam which is repeatedly reflected between the multi-layer reflecting mirror 34 and the output mirror 28 or the band narrowing element 29 and resonant amplified is output as the single laser beam LB. Taken out of the

  In this case, as shown in FIG. 4, the light emitted from the light emission port 30 of the VCSEL element 26 at an angle perpendicular to or near to the substrate surface of the VCSEL element 26 is the opposing surface of the output mirror 28 as indicated by the solid line SB. The light is reflected approximately vertically on the lower surface and returned into the light emission port 30. However, as shown by the alternate long and short dash line SB ′, the light emitted from the light emission port 30 is reflected obliquely on the opposite surface (lower surface) of the output mirror 28 and does not return to the light emission port 30. . As a result, the light SB propagating at or near an angle perpendicular to the substrate surface of the VCSEL element 26 is repeatedly reflected between the multilayer reflector 34 and the output mirror 28 or the band narrowing element 29 to be resonant amplified. A single laser beam LB with a small spread angle is extracted out of the output mirror 28.

  Thus, in this embodiment, the light SB induced and emitted onto the active region 38a of the VCSEL element 26 is reflected by the external output mirror 28 at a considerable distance, so that it is obliquely shifted from the vertical direction It is possible to effectively remove the stimulated emission light SB '(that is, the spread angle is large) from the single laser beam, thereby effectively reducing the spread angle of the single laser beam LB obtained outside the output mirror 28. can do.

  Furthermore, in this embodiment, a collimator is preferably provided as a means for further reducing the spread angle of the single laser beam LB. For this purpose, for example, as shown in FIG. 4, a spherical convex portion 28a is formed on the upper surface of the portion of the output mirror 28 facing the light emission port 30, and the output mirror 28 is provided with a collimating lens function. Good. Alternatively, although not shown, it is possible to arrange an independent collimating lens in addition to the output mirror 28, for example, between the output mirror 28 and the narrowing element 29 or outside the narrowing element 29.

The narrowing element 29 is made of, for example, VBG (Volume Bragg Grating) or VHG (Volume Holographic Grating), functions also as an external resonator, and emits a single laser beam LB or one of the surface emitting lasers 10A (10B). The wavelength width of the bundle laser beam SLB _A (SLB _B ) is narrowed to a sufficiently narrow band λ _SA ± Δλ _A (λ _SB ± Δλ _B ), and the variation of the central wavelength is suppressed to reduce the standard wavelength λ _SA (λ _SB ) Lock around. Here, between the standard wavelength λ _SA of laser oscillation in one surface emitting laser 10 and the standard wavelength λ _SB of laser oscillation in the other surface emitting laser 10 B, the respective wavelength widths are constant so as not to overlap. Offset λ _K is provided (FIG. 5). As an example, λ _SA = 950 nm, λ _SB = 960 nm, Δλ _A , Δλ _B = 0.1 to 3 nm, λ _K = 10 nm.

According to this embodiment, since the light emission port 30 of the VCSEL element 26 has a large aperture (100 to 1000 μm) and the wavelength of the laser oscillation is stably locked in a narrow band, a single laser with a high output of 100 mW or more It is possible to realize a beam LB. Therefore, by providing 1000 or more of such large aperture light emission ports 30 at 100 mW per one on one chip of the VCSEL element 26, it has a laser output of 100 W or more, and one bundle of high beam quality. A laser beam SLB _A (SLB _B ) can be obtained.

[Function of the entire device]
In this embodiment, as described above, the pair of surface emitting lasers 10A and 10B configured by the VCSEL element 26, the output mirror 28, and the band narrowing element 29 has a narrow beam diameter and a narrow divergence angle. _A bundle of laser beams SLB _A and SLB _B is output, which is composed of a plurality of banded high power single laser beams LB and the respective wavelengths do not overlap each other.

In FIG. 1, a bundle of laser beam SLB _A output from one surface emitting laser 10A and a bundle of laser beam SLB _B output from the other surface emitting laser 10B are orthogonal to each other on the same plane. The light then enters the coupling unit 14. The coupling unit 14 is composed of a dichroic mirror 50 having a reflectance characteristic as shown by a curve M in FIG. 5, and transmits one laser beam SLB _A and at the same time turns the other laser beam SLB _B at a right angle It reflects in the direction in which the beam SLB _A travels. Here, both the laser beam SLB _A, since SLB _B do not overlap each wavelength are spatially multiplexed synthesized by the wavelength coupling. In particular, both the surface-emitting laser 10A, two laser beam _SLB A-narrowing element 29 in 10B, respective standard wavelength lambda _SA wavelength of SLB _B, since the narrowed locking near lambda _SB, dichroic Stable and highly accurate wavelength coupling can be performed in the mirror 50.

The combined laser beam SLB _AB obtained by wavelength coupling of the two laser beams SLB _A and SLB _{B by} the dichroic mirror 50 emits a laser beam through the fiber transmission system 15 having the incident unit (condenser lens) 52 and the optical fiber 54. The light is transmitted to the portion 16, and the work piece W on the stage 18 is focused and irradiated by the condensing lens (not shown) in the laser emission portion 16.

This laser processing apparatus desirably performs various types of laser processing such as laser welding, laser marking, laser cutting, laser drilling, and the like by focusing and irradiating the workpiece W with a synthetic laser beam SLB _AB of high power and high beam quality. You can do well with the specifications.

[Other Embodiments or Modifications]
According to the technical idea of the present invention, various other embodiments are possible as extensions or modifications of the above-described embodiments.

  The embodiment shown in FIG. 6 shows a configuration example in which a polarization coupling element 56 is used as the coupling unit 14 instead of the wavelength coupling element 50.

In this case, the laser beam SLB _A a bundle with a standard wavelength lambda _SA from one of the surface emitting laser 10A is outputted by the P-polarized light, the laser beam SLB _B a bundle having from standard wavelength lambda _B other surface emitting laser 10B Are output as s-polarized light. Here, the standard wavelength λ _SA and the standard wavelength λ _SB are selected to be the same value. Although not shown, a half-wave plate may be used to create P-polarized light or S-polarized light. The polarization coupling element 56 is formed of, for example, a polarization beam splitter, and spatially multiplexes the laser beams SLB _A and SLB _B incident orthogonally to each other by polarization coupling, and advances the laser beam SLB _A on the straight going side A combined laser beam SLB _AB is emitted having a standard wavelength λ _SA (λ _SB ) in the direction.

  In the embodiment shown in FIG. 7, the wavelength coupling element 50 and the polarization coupling element 56 are used in combination in the coupling unit 14 and the number of surface emitting lasers (VCSELs) 10 used to increase the output of the combined laser beam is significantly The example shown is increased to six).

In this case, six surface emitting lasers (VCSELs) 10A to 10F are divided into three pairs (10A / 10B), (10C / 10D), and (10E / 10F). In the first pair (10A / 10B), a laser beam SLB _A having a standard wavelength λ _SA is output as P polarized light from one surface emitting laser 10A, and a standard wavelength λ _SB is output from the other surface emitting laser 10B. (where, λ _SB = λ _SA) laser beam SLB _B a bundle having is output by the S-polarized light. Then, both laser beams SLB _A and SLB _B are orthogonal to each other and are incident on the first polarization coupling element 56 (1), where they are polarization coupled and the combined laser beam SLB having the standard wavelength λ _SB (λ _SB ) _AB is obtained.

Similarly, the second set of pairs (10C / 10D), one of the surface emitting laser 10C than the standard wavelength lambda _{SC (However, λ SC = λ SA + λ} K1) laser beam SLB _C a bundle with the P-polarized light is output, the standard wavelength lambda _SD than other surface-emitting laser 10D (however, λ _SD = λ _SC) laser beam SLB _D a bundle having is output by the S-polarized light. Then, the two laser beam _SLB C, and enters the second polarization coupling elements 56 SLB _D are orthogonal to each other (2), where it is polarization coupling, the combined laser beam SLB with a standard wavelength lambda _SC (lambda _{SD) CD} is obtained. Further, in the third set of pairs (10E / 10F), one of the surface emitting laser 10E than the standard wavelength lambda _{SE (However, λ SE = λ SC + λ} K2) a bundle laser beam SLB _E is output as P-polarized light having is the standard wavelength lambda _SF (although, λ _SF = λ _SE) than the other of the surface emitting laser 10F laser beam SLB _F a bundle having is output by the S-polarized light. Then, the two laser beam _SLB E, incident on the third polarization coupling elements 56 SLB _F are orthogonal to each other (3), where it is polarization coupling, the combined laser beam SLB with a standard wavelength lambda _SE (lambda _{SF) EF} is obtained.

A composite laser beam SLB _AB having a standard wavelength λ _SA (λ _SB ) emitted from the first polarization coupling element 56 (1) and a standard wavelength λ emitted from the second polarization coupling element 56 (2) _The combined laser beam SLB _CD having _SC (λ _SD ) is orthogonal to each other and is incident on the first wavelength coupling element 50 (1), where it is wavelength coupled and two types of standard wavelengths λ _SA (λ _SB And λ _SC (λ _SD ), a combined laser beam SLB _ABCD is obtained.

This composite laser beam SLB _ABCD is incident on the second wavelength coupling element 50 (2), and is a composite laser having a standard wavelength λ _SE (λ _SF ) from the third pair of pairs (10E / 10F) orthogonal thereto. It is wavelength coupled with beam SLB _EF . Thus, three standard wavelengths λ _SA (λ _SB ) and λ _SC (λ _SD ) in which the laser outputs of the six surface emitting lasers 10A to 10F are all added from the second wavelength coupling element 50 (2). , Λ _SE (λ _SF ), a high power combined laser beam SLB _ABCDEF is emitted towards the laser optical system (not shown) in the _subsequent stage.

  The embodiment shown in FIG. 8 is characterized in that in the surface emitting laser (VCSEL) 10, the output mirrors 28 are individually disposed at positions corresponding to the light emission ports 30 of the VCSEL elements 26, respectively. Also in this case, in order to reduce the spread angle of the single laser beam LB as much as possible, each output mirror 28 may be provided with a function of a collimating lens, or an independent collimator may be provided downstream of each output mirror 28. A lens (not shown) may be arranged.

  The embodiment shown in FIG. 9 is characterized in that in the surface emitting laser (VCSEL) 10, the narrowing-down element 29 is also used as the output mirror. That is, since the narrowing element 29 functions not only as a narrowing of the wavelength but also as an external resonator, it can be used as an output mirror. Also in this case, a collimating lens (not shown) can be disposed downstream of the narrowing element 29 in order to reduce the spread angle of the single laser beam LB as much as possible.

  In the above embodiment, as described above, the upper semiconductor layer 40 is provided with an antireflective film, and each layer of the upper semiconductor layer 40 is preferably made nonreflective or transparent. However, it is also possible to provide a reflective film in the upper semiconductor layer 40 as one modification or one configuration example.

  The laser device of the present invention has particularly great advantages when applied to the laser processing device as in the above embodiment, but is also applicable to other applications such as a laser medical device.

10, 10A to 10F surface emitting laser (VCSEL)
14 coupling unit 15 fiber traditional system 16 laser emitting unit 20 control unit 26 surface emitting laser element (VCSEL element)
28 Output mirror 29 Narrowing element (VBG / VHG)
Reference Signs List 30 light emission port 32 semiconductor substrate 38a active region 42a opening 50, 50 (1), 50 (2) wavelength coupling element 56, 56 (1), 56 (2), 56 (3) polarization coupling element

Claims (10)

A first surface emitting laser that emits a bundle of first laser beams having a wavelength that matches or approximates a first standard wavelength;
A second surface emitting laser that emits a bundle of second laser beams having a wavelength that matches or approximates a second standard wavelength;
A coupling unit that spatially multiplexes the first laser beam from the first surface emitting laser and the second laser beam from the second surface emitting laser and emits a combined laser beam Have and
Each of the first and second surface emitting lasers is
A semiconductor substrate, an active region formed on the semiconductor substrate, and a large number of light emission ports provided two-dimensionally and discretely provided on the active region, and the semiconductor substrate from each of the light emission ports A surface-emitting laser element for stimulated emission of light having a wavelength that matches or approximates a predetermined standard wavelength in a direction perpendicular or oblique to the substrate surface of the substrate;
And an output mirror disposed at a position facing away from the light emission port of the surface emitting laser element to resonate amplify light emitted by the light emission ports and extract a single laser beam. , Laser device. The first surface emitting laser has a first narrowing element for narrowing the wavelength of the single laser beam to the vicinity of the first standard wavelength,
The second surface emitting laser has a second narrowing element for narrowing the wavelength of the single laser beam to the vicinity of the second standard wavelength.
The laser device according to claim 1.   The laser device according to claim 2, wherein the first and second narrowing elements are provided independently of the output mirror.   The laser device according to claim 2, wherein the first and second narrowing elements double as the output mirror.   The laser according to claim 1, wherein in each of the light emission ports, any thin film provided over the active region has a characteristic of being transparent or non-reflective to the stimulated emission light. apparatus.   The laser apparatus according to claim 1, wherein the output mirror has a lens function for collimating the single laser beam.   The laser apparatus according to claim 1, further comprising an optical lens for collimating the single laser beam independently of the output mirror.   The laser device according to claim 1, wherein the coupling unit includes a wavelength coupling element that multiplexes and combines the first laser beam and the second laser beam by wavelength coupling.   The laser device according to claim 1, wherein the coupling unit has a polarization coupling element that multiplexes and combines the first laser beam and the second laser beam by polarization coupling. A fiber transmission system for transmitting the combined laser beam emitted from the coupling unit through an optical fiber;
2. A laser apparatus according to claim 1, further comprising: a laser emitting unit for focusing and irradiating the combined laser beam extracted from the other end of the optical fiber toward the object to be processed.

Images