JP6909092B2 - Light source device and laser light irradiation device - Google Patents

Description

The present invention relates to a light source device and a laser light irradiation device including the light source device.

Conventionally, as a technique related to a light source device, for example, a linearly polarized light source described in Patent Document 1 is known. The linearly polarized light source described in Patent Document 1 is between a light source having a reflecting mirror, a polarized beam splitter that separates a light flux from the light source into two light fluxes whose polarization directions are orthogonal to each other, and a light source and a polarized beam splitter. It includes an arranged 1/4 wavelength plate and a luminous flux reflecting element that reflects one of the two luminous fluxes and causes the light flux to be incident on the reflecting mirror of the light source. The linearly polarized light source described in Patent Document 1 is designed to efficiently generate linearly polarized light.

Japanese Unexamined Patent Publication No. 2-264904

In the light source device as described above, for example, a fiber laser that emits randomly polarized laser light may be used because of its low price, high output, high distribution, and the like. In this case, there are the following problems caused by the fiber laser. That is, in the randomly polarized laser light, the polarization direction is not constant but changes. Therefore, when the laser beam is split for each polarization component using a polarizing beam splitter in order to obtain a linearly polarized laser beam, the ratio of each laser beam after the branching is not constant and fluctuates. As a result, the laser output of the obtained linearly polarized laser light may also fluctuate (become unstable).

Therefore, it is an object of the present invention to stably obtain linearly polarized laser light in a light source device and a laser light irradiating device using a fiber laser that emits randomly polarized laser light.

The light source device according to the present invention is a fiber laser that emits randomly polarized laser light, and a polarized beam that branches the laser light emitted by the fiber laser into first-branched laser light and second-branched laser light for each polarization component. The splitter, the wavelength plate that changes the polarization direction of the second-branched laser light so that it is the same as the polarization direction of the first-branch laser light, and the first-branch laser light and the wave plate branched by the polarization beam splitter change the polarization direction. A half mirror that combines the changed second-branch laser beam and outputs it as a combined wave laser beam is provided.

In this light source device, randomly polarized laser light emitted from a fiber laser is split by a polarizing beam splitter for each polarization component. The polarization direction of the second-branch laser beam is changed by the wave plate so as to be the same as the polarization direction of the first-branch laser beam. Then, the first and second branch laser beams having the same polarization direction are combined and output by the half mirror. Therefore, even when a fiber laser that emits randomly polarized laser light is used, it is possible to stably obtain linearly polarized laser light regardless of the polarization characteristics of the fiber laser.

In the light source device according to the present invention, the fiber laser may have a main body portion that amplifies the seed light and a laser head portion that is connected to the main body portion via a light guide fiber and emits laser light. .. In this configuration, the fiber laser constitutes a so-called head-separated type fiber laser. In this case, the polarization of the laser light emitted from the fiber laser is likely to be affected by bending of the light guide fiber or the like. Therefore, the above effect of stably obtaining linearly polarized laser light regardless of the polarization characteristics of the fiber laser used is particularly effective.

In the light source device according to the present invention, the optical path difference between the optical path of the first-branch laser beam and the optical path of the second-branch laser beam may be longer than the coherent distance of the fiber laser. According to this configuration, it is possible to suppress the interference of the first and second branch laser beams combined by the half mirror.

In the light source device according to the present invention, the combined wave laser light may include a first combined wave laser light coaxial with the first branched laser light and a second combined wave laser light coaxial with the second branched laser light. good. According to this configuration, two linearly polarized laser beams can be obtained, so that it can be easily applied to various specifications and the like.

The laser light irradiating device according to the present invention is a laser light irradiating device including the above light source device, and is incident with a first polarizing element to which the first combined wave laser light is incident and a second combined wave laser light. It includes an optical system having a second polarizing element.

Since this laser light irradiation device includes the above-mentioned light source device, it has the above-mentioned effect of stably obtaining linearly polarized laser light when a fiber laser that emits randomly polarized laser light is used. Further, in this laser beam irradiation device, it is possible to perform laser beam irradiation using both of the two linearly polarized laser beams obtained by combining the waves with a half mirror.

The laser light irradiating device according to the present invention is a laser light irradiating device including the above light source device, and is a polarizing element to which either one of the first combined wave laser light and the second combined wave laser light is incident, and An optical system having a beam damper that shields either the first combined wave laser light or the second combined wave laser light is provided.

Since this laser light irradiation device includes the above-mentioned light source device, it has the above-mentioned effect of stably obtaining linearly polarized laser light when a fiber laser that emits randomly polarized laser light is used. Further, in this laser beam irradiation device, it is possible to perform laser beam irradiation using only one of the two linearly polarized laser beams obtained by combining the waves with a half mirror.

According to the present invention, it is possible to stably obtain linearly polarized laser light in a light source device and a laser light irradiating device using a fiber laser that emits randomly polarized laser light.

It is a schematic block diagram which shows the laser light irradiation apparatus which concerns on 1st Embodiment. It is a graph for demonstrating the laser beam emitted from the fiber laser of FIG. It is a graph for demonstrating the combined wave laser light output from the light source apparatus of FIG. It is a schematic block diagram which shows the laser light irradiation apparatus which concerns on 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and duplicate description will be omitted.

[First Embodiment]
FIG. 1 is a schematic configuration diagram showing a laser beam irradiation device 100 according to the first embodiment. The laser beam irradiation device 100 is a device that irradiates an object T with linearly polarized laser light L, and includes a light source device 1 and an optical system 30. Linearly polarized light means a polarized state in which the vibration direction of an electric field (and a magnetic field) is constant.

The light source device 1 includes a fiber laser 10 and a polarization adjusting unit 20. The fiber laser 10 emits a randomly polarized laser beam L0. Randomly polarized light means a polarized state in which the polarization direction is not constant and changes with time, although it is linearly polarized light. The fiber laser 10 has a main body portion 11 that amplifies the seed light, and a laser head portion 13 that is connected to the main body portion 11 via a light guide fiber 12. The fiber laser 10 is a solid-state laser that uses an optical fiber as an amplification medium. The fiber laser 10 here is a so-called head-separated type fiber laser. The main body 11 includes a laser diode 14 that oscillates the seed light, and an amplification unit 15 that amplifies and outputs the seed light. The laser head unit 13 emits a randomly polarized laser beam L0.

The polarization adjusting unit 20 includes a polarization beam splitter 21, a mirror 22, a 1/2 wavelength plate (wave plate) 23, a mirror 24, and a half mirror 25. The polarization beam splitter 21 splits the laser beam L0 emitted by the fiber laser 10 into a first-branch laser beam L1 and a second-branch laser beam L2 for each polarization component. In other words, the polarizing beam splitter 21 splits the optical path P0 of the laser beam L0 into the first optical path P1 which is the optical path of the first branch laser beam L1 and the second optical path P2 which is the optical path of the second branch laser beam L2. Branch.

The polarization directions of the first-branch laser beam L1 and the second-branch laser beam L2 are orthogonal to each other. The first-branch laser beam L1 is a P-polarized laser beam, and has, for example, the vertical direction of the paper surface as the polarization direction. The second-branch laser beam L2 is an S-polarized laser beam, and has, for example, a direction perpendicular to the paper surface as a polarization direction. P-polarized light is linearly polarized light in which an electric field oscillates in the incident plane. What is S-polarized light? S-polarized light is linearly polarized light in which an electric field oscillates perpendicular to the incident surface.

The mirror 22 is arranged in the second optical path P2. The mirror 22 reflects the second branch laser beam L2 toward the 1/2 wavelength plate 23. The 1/2 wavelength plate 23 is arranged on the downstream side of the mirror 22 in the second optical path P2. The 1/2 wave plate 23 rotates the polarization component of the second-branch laser beam L2 to change the polarization direction of the second-branch laser beam L2 so as to be the same as the polarization direction of the first-branch laser beam L1.

The mirror 24 is arranged on the downstream side of the 1/2 wavelength plate 23 in the second optical path P2. The mirror 24 reflects the second branch laser beam L2 toward the half mirror 25. The half mirror 25 is arranged at a confluence portion between the downstream side of the first optical path P1 and the downstream side of the second optical path P2. The half mirror 25 combines the first-branched laser beam L1 branched by the polarizing beam splitter 21 and the second-branched laser beam L2 whose polarization direction is changed by the 1/2 wave plate 23, and the combined wave laser beam L3. Output as. The half mirror 25 is a cube-shaped non-polarized half mirror. The half mirror 25 has a transmittance of 50% and a reflectance of 50%.

The combined wave laser beam L3 is a linearly polarized laser beam, and here. It is a P-polarized laser beam. The combined wave laser beam L3 includes a first combined wave laser beam L31 coaxial with the first branched laser beam L1 and a second combined wave laser beam L32 coaxial with the second branched laser beam L2. The first combined wave laser beam L31 is a laser beam obtained by combining a part of the first branched laser beam L1 transmitted through the half mirror 25 and a part of the second branched laser beam L2 reflected by the half mirror 25. be. The second combined wave laser beam L32 is a laser beam obtained by combining a part of the first branched laser beam L1 reflected by the half mirror 25 and a part of the second branched laser beam L2 transmitted through the half mirror 25. be.

The second optical path P2 includes a third optical path P21 from the polarizing beam splitter 21 to the mirror 22, a fourth optical path P22 from the mirror 24 to the half mirror 25, and a fifth optical path P23 from the mirror 22 to the mirror 24. The fifth optical path P23 has the same optical path length as the first optical path P1. The optical path difference between the first optical path P1 and the second optical path P2 (that is, the optical path lengths of the third optical path P21 and the fourth optical path P22) is longer than the coherent distance of the fiber laser 10. The coherent distance is the upper limit of the distance at which the light interference phenomenon appears when the first-branch laser beam L1 and the second-branch laser beam L2 are combined.

The optical system 30 includes a spatial light modulator (first polarizing element) 31, a 4f optical system 32, a condenser lens 33, a spatial light modulator (second polarizing element) 35, a 4f optical system 36, and a condenser lens 37. Has. Spatial light modulators 31 and 35 are, for example, spatial light modulators (SLMs) of reflective liquid crystals (LCOS: Liquid Crystal on Silicon). The spatial light modulator 31 is a polarizing element to which the first combined wave laser beam L31 is incident. The spatial light modulator 31 modulates and reflects the incident first combined wave laser light L31. The spatial light modulator 35 is a polarizing element to which the second combined wave laser beam L32 is incident. The spatial light modulator 35 modulates and reflects the incident second combined wave laser light L32.

Spatial light modulators 31 and 35 have a display unit capable of displaying a modulation pattern. The spatial light modulator 31 adjusts the wavefront of the first combined wave laser light L31 according to the modulation pattern by incidenting the first combined wave laser light L31 into the modulation pattern. The spatial light modulator 35 adjusts the wavefront of the second combined wave laser light L32 according to the modulation pattern by incidenting the second combined wave laser light L32 into the modulation pattern. In each of the spatial light modulators 31 and 35, the modulation (for example, intensity, amplitude, phase, polarization, etc.) of the first and second combined wave laser beams L31 and L32 can be adjusted by appropriately setting each modulation pattern to be displayed. Modulation) is possible.

The 4f optical system 32 is an adjustment optical system that adjusts (wavefront adjustment) the wavefront shape of the first combined wave laser light L31 modulated by the spatial light modulator 31. The 4f optical system 32 is arranged on the optical path between the spatial light modulator 31 and the condenser lens 33. The 4f optical system 36 is an adjustment optical system that adjusts the wavefront shape of the second combined wave laser light L32 modulated by the spatial light modulator 35. The 4f optical system 36 is arranged on the optical path between the spatial light modulator 35 and the condenser lens 37.

The condensing lens 33 condenses the first combined wave laser beam L31 on the object T. The condensing lens 37 condenses the second combined wave laser beam L32 on the object T. Each of the condenser lenses 33 and 37 may be configured to include a plurality of lenses.

In the laser beam irradiation device 100 described above, in the light source device 1, the randomly polarized laser beam L0 emitted from the fiber laser 10 is branched for each polarization component by the polarization beam splitter 21. The polarization component of the second-branch laser beam L2 is rotated by the 1/2 wave plate 23 so that the polarization direction of the second-branch laser beam L2 is the same (parallel) as the polarization direction of the first-branch laser beam L1. be changed. Then, the first and second branched laser beams L1 and L2 having the same polarization direction are combined by the half mirror 25, and finally output as a combined wave laser beam L3 aligned to a single linearly polarized light. NS.

The first combined wave laser light L31 of the combined wave laser light L3 is incident on the spatial light modulator 31 in the optical system 30 and is modulated according to the modulation pattern displayed on the display unit of the spatial light modulator 31. After that, the wave surface is adjusted by the 4f optical system 32. The first combined wave laser beam L31 whose wavefront is adjusted by the 4f optical system 32 is condensed by the condenser lens 33 and irradiated to the object T as the laser beam L. The second combined wave laser light L32 of the combined wave laser light L3 is incident on the spatial light modulator 35 in the optical system 30 and is modulated according to the modulation pattern displayed on the display unit of the spatial light modulator 35. After that, the wave surface is adjusted by the 4f optical system 36. The second combined wave laser beam L32 whose wavefront is adjusted by the 4f optical system 36 is condensed by the condenser lens 37 and irradiated to the object T as the laser beam L.

FIG. 2 is a graph for explaining the laser beam L0 emitted from the fiber laser 10. The vertical axis is the normalized laser output obtained by dividing the laser output by the reference output value. The horizontal axis is hour. The data label value of "P-polarized light" indicates the standardized laser output of the polarized light component of P-polarized light formed by separating the laser beam L0 emitted by the fiber laser 10 with a polarizer or the like. The data label value of "S-polarized light" indicates the standardized laser output of the polarized light component of S-polarized light formed by separating the laser beam L0 emitted by the fiber laser 10 with a polarizer or the like. The data label value of "total" indicates the total of the polarization component of the P-polarized light and the polarization component of the S-polarized light.

As shown in FIG. 2, the total laser output is stable after a lapse of a predetermined time, while the P-polarized and S-polarized laser outputs vary more than the total. This is because the laser beam L0 emitted from the fiber laser 10 has polarized polarized light of random polarization, and the ratio of the polarized light component of P polarized light to the polarized light component of S polarized light fluctuates. Therefore, the laser outputs of P-polarized light and S-polarized light are affected by the polarization characteristics of the fiber laser 10 and become unstable. For example, in the fiber laser 10, if the fiber such as the light guide fiber 12 is bent or crushed, the polarization of the emitted laser light L0 may be affected. When the light guide fiber 12 is moved, the polarized light may fluctuate during the movement. Therefore, in general, when a fiber laser 10 that emits randomly polarized laser light L0 is used in a light source device, it is difficult to use a polarizing element (spatial light modulator or the like) for the obtained linearly polarized laser light. It turns out that there is.

On the other hand, according to the light source device 1 according to the present embodiment, as described above, the randomly polarized laser beam L0 emitted from the fiber laser 10 is branched into the first and second branched laser beams L1 and L2. , The polarization direction of the second branch laser beam L2 is changed by the 1/2 wave plate 23 so as to be the same as the polarization direction of the first branch laser beam L1, and the first and second branch laser beams L1 and L2 are half mirrors. It is combined at 25 and output as a combined wave laser beam L3. Therefore, even when a fiber laser 10 that emits a randomly polarized laser beam L0 is used, a linearly polarized laser beam L (combined wave laser beam L3) is stably obtained regardless of the polarization characteristics of the fiber laser 10. It becomes possible. It is possible to obtain a light source device 1 which is cheaper and has higher output than the existing light source device.

FIG. 3 is a graph for explaining the combined wave laser beam L3 output from the light source device 1. The vertical axis is the normalized laser output obtained by dividing the laser output by the reference output value. The horizontal axis is time (min). The data label value of "original output" indicates the normalized laser output of the randomly polarized laser beam L0 emitted by the fiber laser 10.

The data label value of the "first-branch laser beam" indicates the standardized laser output of the first-branch laser beam L1 in which the randomly polarized laser beam L0 is simply branched by the polarizing beam splitter 21. The data label value of the "first-branch laser beam" here is the polarization adjustment (that is, the second-branch laser beam whose polarization direction is changed by the first-branch laser beam L1 and the 1/2 wave plate 23 by the half mirror 25. It is a standardized laser output of the first-branched laser beam L1 of P-polarized light before (combining with L2). The data label value of "combined wave laser beam" indicates the normalized laser output of the combined wave laser beam L3. The data label value of the "combined wave laser beam" here is the standardized laser output of the P-polarized first combined wave laser beam L31 after the polarization adjustment. According to the result shown in FIG. 3, it can be confirmed that the laser output of the combined wave laser beam L3 after the polarization adjustment has the same output fluctuation as the stable laser output of the original output.

In the light source device 1, the fiber laser 10 constitutes a so-called head-separated type fiber laser having a main body portion 11 and a laser head portion 13. In this case, bending of the light guide fiber 12 or the like tends to affect the polarization of the laser beam L0 emitted from the fiber laser 10. Therefore, the above effect of stably obtaining linearly polarized laser light L regardless of the polarization characteristics of the fiber laser 10 used is particularly effective.

In the light source device 1, the optical path difference between the first optical path P1 of the first branch laser beam L1 and the second optical path P2 of the second branch laser beam L2 is longer than the coherent distance of the fiber laser 10. According to this configuration, it is possible to suppress the interference of the first and second branch laser beams L1 and L2 that are combined by the half mirror 25. It is possible to output a combined wave laser beam L3 having the same beam profile as the laser beam L0 emitted from the fiber laser 10.

In the light source device 1, the combined wave laser light L3 includes a first combined wave laser light L31 coaxial with the first branched laser light L1 and a second combined wave laser light L32 coaxial with the second branched laser light L2. According to this configuration, two linearly polarized first and second combined wave laser beams L31 and L32 can be obtained, so that they can be easily applied to various specifications and the like.

The laser beam irradiation device 100 also has the above-mentioned effect of stably obtaining the linearly polarized laser beam L when the fiber laser 10 that emits the randomly polarized laser beam L0 is used by the light source device 1. Further, in the laser light irradiation device 100, it is possible to perform laser light irradiation using both the two first and second combined wave laser beams L31 and L32 obtained by combining the waves with the half mirror 25. It is possible to obtain a laser beam irradiation device 100 having specifications of having two ports of laser output (using two beams).

[Second Embodiment]
Next, the laser light irradiation device of the second embodiment will be described. In the description of the present embodiment, the points different from those of the first embodiment will be described.

FIG. 4 is a schematic configuration diagram showing the laser light irradiation device 200 according to the second embodiment. As shown in FIG. 4, the laser beam irradiation device 200 is different from the first embodiment in that the optical system 40 is provided in place of the optical system 30 (see FIG. 1). The optical system 40 includes a spatial light modulator (polarizing element) 31, a 4f optical system 32, a condenser lens 33, and a beam damper 44. The beam damper 44 shields the second combined wave laser beam L32.

In the laser light irradiation device 200, the first combined wave laser light L31 of the combined wave laser light L3 was incident on the spatial light modulator 31 in the optical system 30 and displayed on the display unit of the spatial light modulator 31. After being modulated according to the modulation pattern, the wavefront is adjusted by the 4f optical system 32. The first combined wave laser beam L31 whose wavefront is adjusted by the 4f optical system 32 is condensed by the condenser lens 33 and irradiated to the object T as the laser beam L. On the other hand, the second combined wave laser beam L32 of the combined wave laser light L3 is shielded by the beam damper 44 and terminated.

As described above, the laser beam irradiating device 200 also has the above-mentioned effect of stably obtaining the linearly polarized laser beam L when the fiber laser 10 that emits the randomly polarized laser beam L0 is used by the light source device 1. Further, in the laser light irradiation device 200, it is possible to perform laser light irradiation using only one of the two first and second combined wave laser beams L31 and L32 obtained by combining the waves with the half mirror 25. It is possible to obtain a laser beam irradiation device 200 having a specification of having one port of laser output (using one beam).

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the gist described in each claim is modified or applied to other things without changing the gist. You may.

In the above embodiment, the spatial light modulators 31 and 35 are provided as the polarizing elements, but the polarizing elements applied to the laser light irradiation devices 100 and 200 are not particularly limited, and instead of the spatial light modulators 31 and 35. Alternatively, other polarizing elements may be provided.

In the second embodiment, the first combined wave laser light L31 is incident on the spatial light modulator 31, and the second combined wave laser light L32 is incident on the beam damper 44. The wave laser light L32 may be incident on the spatial light modulator 31, and the first combined wave laser light L31 may be incident on the beam damper 44. In this case, the first combined wave laser light L31 is shielded and terminated by the beam damper 44, while the second combined wave laser light L32 is modulated according to the modulation pattern displayed on the display unit of the spatial light modulator 31. After that, the wavefront is adjusted by the 4f optical system 32, the light is condensed by the condenser lens 33, and the object T is irradiated with the laser beam L.

1 ... Light source device, 10 ... Fiber laser, 11 ... Main body, 12 ... Light guide fiber, 13 ... Laser head, 21 ... Polarized beam splitter, 23 ... 1/2 wave plate (wave plate), 25 ... Half mirror, 30 ... Optical system, 31 ... Spatial light modulator (polarizing element, first polarizing element), 35 ... Spatial light modulator (second polarizing element), 40 ... Optical system, 44 ... Beam damper, 100, 200 ... Laser light Irradiating device, P1 ... 1st optical path (optical path of 1st branched laser beam), P2 ... 2nd optical path (optical path of 2nd branched laser beam).

Claims (6)

A fiber laser that emits randomly polarized laser light,
A polarizing beam splitter that splits the laser beam emitted by the fiber laser into a first-branch laser beam and a second-branch laser beam for each polarization component.
A wave plate that changes the polarization direction of the second-branch laser beam so that it is the same as the polarization direction of the first-branch laser beam.
A half mirror is provided which combines the first-branched laser light branched by the polarization beam splitter and the second-branched laser light whose polarization direction is changed by the wave plate and outputs the combined wave laser light. Light source device. The fiber laser is
The main body that amplifies the seed light and
The light source device according to claim 1, further comprising a laser head portion connected to the main body portion via a light guide fiber and emitting the laser beam. The light source device according to claim 1 or 2, wherein the optical path difference between the optical path of the first-branch laser beam and the optical path of the second-branch laser beam is longer than the coherent distance of the fiber laser. The combined wave laser light includes any of claims 1 to 3 including a first combined wave laser light coaxial with the first branched laser light and a second combined wave laser light coaxial with the second branched laser light. The light source device according to paragraph 1. A laser light irradiation device including the light source device according to claim 4.
A laser light irradiation device including an optical system having a first polarizing element to which the first combined wave laser light is incident and a second polarizing element to which the second combined wave laser light is incident. A laser light irradiation device including the light source device according to claim 4.
The polarizing element to which either one of the first combined wave laser beam and the second combined wave laser light is incident, and the other of the first combined wave laser light and the second combined wave laser light are shielded. A laser beam irradiation device including an optical system having a beam damper.

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