Laser beam irradiation apparatus and laser beam irradiation system

A laser beam irradiation apparatus including: a plurality of laser light sources emitting first laser beams; and a light-condensing optics system having an incident face on which the first laser beams are made incident and performing an optical operation on the first laser beams to emit second laser beams. The plurality of laser light sources are configured to emit the first laser beams so that beam diameters are expanded towards the incident face. Each first laser beam overlaps at least one of the other laser beams on the incident face. The light-condensing optics system is configured so that beam diameters of second laser beams emitted from the light-condensing optics system are minimal on a target face, and a distance between a center of each second laser beam and the optical axis on the target face is smaller than a beam radius of each second laser beam on the target face.

TECHNICAL FIELD

The present invention relates to a laser beam irradiation apparatus and a laser beam irradiation system, more particularly, to a laser beam irradiation apparatus and a laser beam irradiation system configured to irradiate on a target a high-power laser beam obtained by combining a plurality of laser beams.

BACKGROUND ART

One method to obtain a high-power laser is to combine a plurality of laser beams which are separately generated. Methods of combining a plurality of laser beams can be generally classified into two types.

A first method is to combine a plurality of laser beams on the target. In this method, a plurality of laser beams are emitted from different positions at slightly different angles and irradiated on the target so that the plurality of laser beams are condensed at the same position defined on the target. When this method is used, the number of laser beams is in a trade-off relation with the beam diameters of the respective laser beams and the physical size of the irradiation apparatus. Although an increase in the number of emitted laser beams achieves high power, this is accompanied by an increase in the physical size of the irradiation apparatus (for example, the diameter of a lens barrel accommodating the optics system) for a fixed beam diameter, causing an increase in the weight. An increase in the weight of the irradiation apparatus may increase the manufacture cost and cause a problem of difficulty in the design of a mechanical drive mechanism (e.g., a drive mechanism of the lens barrel) of the irradiation apparatus. When the number of emitted laser beams is increased for a fixed physical size of the irradiation apparatus, on the other hand, the beam diameters of the respective laser beams are reduced, and this causes a problem of deterioration in the light-condensing ability, that is, increase in the focal spot diameter on the target.

A second method is to combine a plurality of laser beams internally in the irradiation apparatus. This method allows the diameters of the respective laser beams to be increased approximately up to the diameter of the lens barrel, since all the laser beams are coaxially emitted from the lens barrel.

The spectrum combination is a known method to combine a plurality of laser beams internally in an irradiation apparatus. The spectrum combination is a technique which combines a plurality of laser beams with a diffractive optical element such as a diffractive grating. A set of laser beams with slightly-different emitting angles are generated by irradiating a plurality of laser beams of slightly-different center wavelengths on an diffractive optical element which exhibits wavelength dependencies on the reflection angle and the diffraction angle, and the set of laser beams are coaxially combined in a light-emitting optics system by making use of the differences in the emitting angle. A technique for obtaining a high-power laser beam through spectrum combination is disclosed in JP 2015-72955A, for example.

One issue in the spectrum combination is that it is generally difficult to provide a large-sized diffractive optical element used for spectrum combination with high laser power tolerance. This implies there are limitations on the number of laser beams and the powers thereof. Additionally, it is necessary to sufficiently reduce the linewidths of the respective laser beams for increasing the number of laser beams, and this is generally contradictory to high power.

As discussed above, there is room for improvement in the technology for obtaining a high-power synthesized laser beam by combining a plurality of laser beams.

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Accordingly, an objective of the present invention is to provide a technique for obtaining a high-power synthesized laser beams by combining a plurality of laser beams. Other objectives and new features of the present invention would be understood by a person skilled in the art from the following disclosure.

In one embodiment of the present invention, a laser beam irradiation apparatus comprises: a plurality of laser light sources emitting first laser beams, respectively; and a light-condensing optics system comprising an incident face on which the first laser beams are made incident and performing an optical operation on the first laser beams to emit second laser beams associated with the first laser beams, respectively. The plurality of laser light sources are configured to emit the first laser beams from different positions so that beam diameters of the first laser beams are expanded towards the incident face of the light-condensing optics system. Each of the first laser beams emitted from the plurality of laser light sources overlaps at least one of the other first laser beams on the incident face of the light-condensing optics system.

The light-condensing optics system is configured so that beam diameters of all the second laser beams emitted from the light-condensing optics system are minimal on a target face which is a plane defined to be orthogonal to an optical axis of the light-condensing optics system, and a distance between a center of each of the second laser beams and the optical axis on the target face is smaller than a beam radius which is half a beam diameter of each of the second laser beams on the target face.

It is preferable that each of the first laser beams emitted from the plurality of laser light sources overlaps all other first laser beams on the incident face of the light-condensing optics system.

In one embodiment, the plurality of laser light sources respectively comprise phase control devices controlling phases of the first laser beams emitted therefrom. In this case, the phase control devices may control the phases of the first laser beams so that phases of the second laser beams are made the same on an emitting face of the light-condensing optics system.

In one embodiment, the laser beam irradiation apparatus may further comprise a beam shaping optics system shaping wave fronts of the first laser beams. When the plurality of laser light sources respectively comprise phase control devices controlling phases of the first laser beams emitted therefrom, the laser beam irradiation apparatus may comprise a plurality of beam shaping optics systems respectively shaping wave fronts of the first laser beams emitted from the plurality of laser light sources.

In one embodiment, the plurality of laser light-sources may respectively comprise optical fibers emitting the first laser beams from respective ends thereof, and the laser beam irradiation apparatus may further comprise a coupling optical element. The coupling optical element is coupled to the optical fibers of the plurality of laser light sources and configured to guide the first laser beams emitted from the optical fibers to the incident face of the light-condensing optics system.

In another embodiment, a laser beam irradiation apparatus comprises: a plurality of laser light sources emitting first laser beams, respectively; and a collimating optics system comprising an incident face on which the first laser beams are made incident and performing an optical operation on the first laser beams to emit second laser beams which are collimated beams, the second laser beams being associated with the first laser beams, respectively. The plurality of laser light sources are configured to emit the first laser beams from different positions so that beam diameters of the first laser beams are expanded towards the incident face of the collimating optics system. Each of the first laser beams emitted from the plurality of laser light sources overlaps at least one of the other first laser beams on the incident face of the collimating optics system. The collimating optics system is configured so that a distance between a center of each of the second laser beams and an optical axis of the collimating optics system is smaller than a beam radius which is half a beam diameter of each of the second laser beams.

The laser beam irradiation apparatus may further comprise a solid-state laser amplifier receiving the plurality of second laser beams emitted from the collimating optics system and performing laser amplification on the plurality of second laser beams to generate an amplified laser beam. This configuration is useful especially when each of the laser light sources comprises a fiber laser.

In still another embodiment, a laser beam irradiation system comprises a plurality of laser beam irradiation apparatuses and a light-condensing optics system. Each of the plurality of laser beam irradiation apparatuses comprises: a plurality of laser light sources emitting first laser beams, respectively; and a collimating optics system comprising an incident face on which the first laser beams are made incident and performing an optical operation on the first laser beams to emit second laser beams which are collimated beams, the second laser beams being associated with the first laser beams, respectively. The plurality of laser light sources are configured to emit the first laser beams from different positions so that beam diameters of the first laser beams are expanded towards the incident face of the collimating optics system. Each of the first laser beams emitted from the plurality of laser light sources overlaps at least one of the other first laser beams on the incident face of the collimating optics system. The collimating optics system is configured so that a distance between a center of each of the second laser beams and an optical axis of the collimating optics system is smaller than a beam radius which is half a beam diameter of each of the second laser beams. Synthesized beams each composed of the plurality of the second laser beams emitted from each of the plurality of laser beam irradiation apparatuses are made incident on an incident face of the light-condensing optics system. The light-condensing optics system is configured to perform an optical operation on the synthesized beams to emit third laser beams respectively associated with the synthesized beams. The light-condensing optics system is configured so that beam diameters of all the third laser beams emitted from the light-condensing optics system are minimal on a target face which is a plane defined to be orthogonal to an optical axis of the light-condensing optics system, and a distance between a center of each of the third laser beams and the optical axis on the plane is smaller than a beam radius which is half a beam diameter of each of the third laser beams on the target face.

In still another embodiment, a laser beam irradiation system comprises a plurality of laser beam irradiation apparatuses; and a first collimating optics system. Each of the plurality of laser beam irradiation apparatuses comprises: a plurality of laser light sources emitting first laser beams, respectively; and a second collimating optics system comprising an incident face on which the first laser beams are made incident and performing an optical operation on the first laser beams to emit second laser beams which are collimated beams, the second laser beams being associated with the first laser beams, respectively. The plurality of laser light sources are configured to emit the first laser beams from different positions so that beam diameters of the first laser beams are expanded towards the incident face of the collimating optics system. Each of the first laser beams emitted from the plurality of laser light sources overlaps at least one of the other first laser beams on the incident face of the second collimating optics system. The second collimating optics system is configured so that a distance between a center of each of the second laser beams and an optical axis of the second collimating optics system is smaller than a beam radius which is half a beam diameter of each of the second laser beams. Synthesized beams each composed of the plurality of the second laser beams emitted from each of the plurality of laser beam irradiation apparatuses are made incident on an incident face of the first collimating optics system. The first collimating optics system is configured to perform an optical operation on the synthesized beams to emit third laser beams which are collimated beams, the third laser beams being associated with the synthesized beams, respectively.

The present invention effectively provides a technique for obtaining a high-power synthesized laser beams by combining a plurality of laser beams.

DESCRIPTION OF EMBODIMENTS

In the following, a description is given of embodiments of the present invention with reference to the attached drawings. In the attached drawings, the same elements are denoted by the same reference numerals. Suffixes may be attached to distinguish the same elements from each other. In the following description, an XYZ Cartesian coordinate system is introduced to define directions.

First Embodiment

FIG. 1is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus100, according to a first embodiment. The laser beam irradiation apparatus100comprises a plurality of laser light sources10and a light-condensing optics system20. The laser light sources10and the light-condensing optics system20are housed in a lens barrel30. In the following, suffixes are attached when the plurality of laser light sources10are distinguished from each other. InFIG. 1, three laser light sources101to103are illustrated. The number of the laser light sources10is not limited to three; four or more laser light sources10may be provided.

Each laser light source10emits a laser beam11. In detail, each laser light source10comprises a laser device12and an optical fiber13in this embodiment. A laser beam generated by a laser device12is made incident on one end of an optical fiber13, and emitted from the other end as a laser beam11. In the following, the laser beams11emitted from the laser light sources101to103may be referred to as laser beams111to113, respectively. In this embodiment, the laser light sources10emit the laser beams11from different positions in the Y axis direction. The laser beams11emitted from the laser light source10are made incident on an incident face20aof the light-condensing optics system20.

The light-condensing optics system20generates laser beams21by performing an optical operation on the laser beams11incident on the incident face20a, and emits the generated laser beams21from an emitting face20b. The optical operation performed by the light-condensing optics system20comprises an operation for condensing the respective laser beams21. In the following, the laser beams21generated from the laser beams111to113and emitted from the emitting face20bmay be referred to as laser beams211to213, respectively. In this embodiment, the light-condensing optics system20is arranged so that the optical axis22thereof is parallel to the Z axis direction. The laser beams21emitted from the emitting face20bof the light-condensing optics system20are irradiated on a desired target, overlapping each other.

In the laser beam irradiation apparatus100according to this embodiment, each laser light source10is configured to emit a laser beam11so that the beam diameter of the laser beam11is expanded toward the incident face20aof the light-condensing optics system20. In general, when a laser beam is emitted from an optical fiber, the emitted laser beam naturally has an expanding angle. In one embodiment, this phenomenon may be used to expand the beam diameters of the laser beams11emitted from the optical fibers13towards the incident face20aof the light-condensing optics system20. Alternatively, an optical element such as a lens may be coupled to an optical fiber13to expand the beam diameter of a laser beam11emitted from the optical fiber13towards the incident face20aof the light-condensing optics system20.

Additionally, the laser light sources10are arranged so that the laser beam11emitted from each laser light source10overlaps at least one of the laser beams11emitted from the other laser light sources10on the incident face20a. This configuration is advantageous for generating a high-power synthesized laser beam, while suppressing an increase in the physical size of the laser beam irradiation apparatus100. Under this aim, when the number of the laser light sources10is three or more, it is preferable that the laser light sources10are arranged so that the laser beam11emitted from each laser light source10overlaps all the laser beams11emitted from the other laser light sources10on the incident face20a.

The light-condensing optics system20is configured as follows. First, the light-condensing optics system20is configured so that, when a laser beam11of a beam shape circular symmetric about the optical axis22is made incident on the incident face20a, the beam shape of a laser beam21generated from the laser beam11and emitted from the emitting face20bis circular symmetric about the optical axis22.

The light-condensing optics system20is further configured so that the beam diameters (or the spot diameters) of all the laser beams21emitted from the emitting face20bare minimal on a target face40which is a plane defined orthogonally to the optical axis22of the light-condensing optics system20. In this embodiment, the target face40is parallel to the XY plane. When the laser beams21are irradiated on a target, the target face40is set so that the target face40crosses the target. This implies that the light-condensing optics system20is configured to focus the respective laser beams21on the target face40. The light-condensing optics system20may be configured so that the position of the target face40is adjustable in a direction parallel to the optical axis22.

The light-condensing optics system20is further configured so that the distance between the optical axis22and the center of each laser beam21on the target face40is smaller than the beam radius of each laser beam21on the target face40, where the beam radius is half the beam diameter. In this embodiment, the beam diameter on the target face40is defined as the D86 width (the diameter of the circle encompassing 86% of the beam power, the center of the circle being positioned at the geometric center of the beam profile). In this embodiment, the position of the center of each laser beam21on the target face40is defined as the position of the geometric center of the beam profile of each laser beam21on the target face40.FIGS. 2A to 2Care diagram illustrating the beam shapes of the respective laser beams21, according to this embodiment.

FIG. 2Aillustrates the beam shape of the laser beam211generated by the light-condensing optics system20from the laser beam111emitted from the laser light source101. As illustrated inFIG. 2A, the beam diameter of the laser beam211is minimal on the target face40. The distance d1between the optical axis22and the center231of the laser beam211on the target face40is smaller than the beam radius r1of the laser beam211on the target face40(that is, half the beam diameter of the laser beam211on the target face40). In other words, the following expression (1) holds:
d1<r1.  (1)

FIG. 2Billustrates the beam shape of the laser beam212generated by the light-condensing optics system20from the laser beam112emitted from the laser light source102. The beam shape of the laser beam112emitted from the laser light source102is circular symmetric about the optical axis22, and accordingly the beam shape of the laser beam212, which is emitted from the light-condensing optics system20, is also circular symmetric about the optical axis22.

As illustrated inFIG. 2B, the beam diameter of the laser beam211is minimal on the target face40, as is the case with the laser beam211. The center232of the laser beam212on the target face40is positioned on the optical axis22, and the distance d2between the optical axis22and the center231of the laser beam212on the target face40is zero. Accordingly, the following expression (2) holds also for the laser beam212:
d2<r2,  (2)
where r2is the beam radius of the laser beam212on the target face40(that is, half the beam diameter of the laser beam212on the target face40).

FIG. 2Cillustrates the beam shape of the laser beam213generated by the light-condensing optics system20from the laser beam113emitted from the laser light source103. As illustrated inFIG. 2C, the beam diameter of the laser beam213is also minimal on the target face40. The distance d3between the optical axis22and the center233of the laser beam213on the target face40is smaller than the beam radius r3of the laser beam213on the target face40(that is, half the beam diameter of the laser beam213on the target face40). In other words, the following expression (3) holds:
d3<r3.  (3)

The condition that the distance between the optical axis22and the center of each laser beam21on the target face40is smaller than the beam radius of each laser beam21is for maintaining the combination of the laser beams21on the target face40. In this embodiment, since the laser beams11are made incident on the incident face20aat different positions, the positions of the beam centers on the target face40of the laser beams21emitted from the emitting face20bmay be different from each other; however, when the distance between the optical axis22and the center of each laser beam21on the target face40is smaller than the beam radius of each laser beam21on the target face40, each laser beam21overlaps all other laser beams21on the target face40. This achieves beam combination.

The above-described configuration according to this embodiment makes it possible to irradiate a high-power synthesized laser beam on the target, while achieving suppression of an increase in the physical size of the laser beam irradiation apparatus100and improvement in the light-condensing ability.

In detail, the laser light sources10are arranged so that the laser beam11emitted from each laser light source10overlaps at least one of the laser beams11emitted from the other laser light sources10on the incident face20a, in this embodiment. This achieves generation of a high-power synthesized laser beam while suppressing an increase in the physical size of the laser beam irradiation apparatus100. When the number of the laser beams11is three or more, from the viewpoint of suppression in an increase in the physical size and generation of a high-power synthesized laser beam, it is preferable that the laser beam11emitted by each laser light source10overlaps the laser beams11emitted by all other laser light sources10on the incident face20a.

Additionally, in the laser beam irradiation apparatus100according to this embodiment, each of the laser light sources10is configured to emit the laser beam11so that the beam diameter of the laser beam11is expanded towards the incident face20aof the light-condensing optics system20. Accordingly, the beam diameter of each laser beam21is enlarged on the emitting face20bof the light-condensing optics system20. This implies that the focal spot diameter of each laser beam21can be reduced on the target face40. This effectively improves the light-condensing ability.

It should also be noted that the laser beam irradiation apparatus100offers laser beam combination without using a special optical element such as a diffraction optical element. The laser beam irradiation apparatus100according to this embodiment can generate a high-power synthesized laser beam without using a special optical element, while achieving suppression in an increase in the physical size and improvement in the light-condensing ability.

Second Embodiment

FIG. 3is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus100A, according to a second embodiment. The laser beam irradiation apparatus100A according to the second embodiment is configured similarly to the laser beam irradiation apparatus100according to the first embodiment; a difference from the laser beam irradiation apparatus100according to the first embodiment is that each laser light source10comprises a phase control device14controlling the phase of the laser beam11emitted from the laser light source10. In this embodiment, the phase control device14is inserted into the optical fiber13of each laser light source10.

In the laser beam irradiation apparatus100A according to the second embodiment, the phases of the laser beams11incident on the light-condensing optics system20are controlled by the phase control devices14and this achieves control of the shapes of the wave fronts of the laser beams21emitted from the light-condensing optics system20to shapes suitable for propagation. This effectively improves the light-condensing ability. The phases of the laser beams21may be made the same on the emitting face20bof the light-condensing optics system20, for example, by controlling the phases of the laser beams11emitted from the laser light sources10with the phase control devices14. This achieves aperture synthesis, improving the light-condensing ability.

Third Embodiment

FIG. 4is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus100B, according to a third embodiment. The laser beam irradiation apparatus100B according to the third embodiment is configured similarly to the laser beam irradiation apparatus100according to the first embodiment; a difference from the laser beam irradiation apparatus100according to the first embodiment is that the laser beam irradiation apparatus100B according to the third embodiment comprises beam shaping optics systems15which respectively shape the wave fronts of the laser beams11emitted from the laser light sources10. In this embodiment, the beam shaping optics systems15are coupled to light-emitting ends of the optical fibers13of the respective laser light sources10, the laser beams11being emitted from the light-emitting ends. Optical elements such as concave lenses and convex lenses may be used as the beam shaping optics systems15.

In the third embodiment, the wave fronts of the laser beams11emitted from the respective laser light sources10are shaped by the beam shaping optics systems15and this successfully controls the shapes of the wave fronts of the laser beams21emitted from the light-condensing optics system20to shapes suitable for propagation. This effectively improves the light-condensing ability.

AlthoughFIG. 4illustrates the configuration in which each laser light source10comprises a beam shaping optics system15, a common beam shaping optics system16may instead be provided for a plurality of laser light sources10as illustrated inFIG. 5. The beam shaping optics system16shapes the wave fronts of the laser beams11emitted from the respective laser light sources10and thereby controls the shapes of the wave fronts of the laser beams21emitted from the light-condensing optics system20to shapes suitable for propagation.

As illustrated inFIG. 6, the laser beam irradiation apparatus100B according to the second embodiment, which comprises the phase control devices14, may further comprise the beam shaping optics systems15(or the beam shaping optics system16). In this case, since the phases of the laser beams11incident on the respective beam shaping optics systems15are controlled, it is possible to control the shapes of the wave fronts of the laser beams21emitted from the light-condensing optics system20to shapes suitable for propagation, while the configurations of the beam shaping optics systems15are simplified.

Fourth Embodiment

FIG. 7is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus100C, according to a fourth embodiment. The laser beam irradiation apparatus100C according to the fourth embodiment is configured similarly to the laser beam irradiation apparatus100according to the first embodiment; a difference from the laser beam irradiation apparatus100according to the first embodiment is that the laser light sources10are coupled to the incident face20aof the light-condensing optics system20with a coupling optical element17. In this embodiment, the coupling optical element17is coupled to the light-emitting ends of the optical fibers13of the respective laser light sources10, the laser beams11being emitted from the light-emitting ends. Examples of the coupling optical element17include a tapered lens. The coupling optical element17may be coupled to the optical fibers13by fusion bonding. The coupling optical element17is configured to guide the laser beams11emitted from the optical fibers13of the respective laser light sources10to the incident face20aof the light-condensing optics system20.

In this embodiment, the coupling optical element17, which is coupled to the light-emitting ends of the optical fibers13, effectively facilitates the alignment of the optical fibers13. Note that the coupling optical element17may have the function of shaping the wave fronts of the laser beams11emitted from the respective laser light sources10. This is useful for controlling the shapes of the wave fronts of the laser beams21emitted from the light-condensing optics system20to shapes suitable for propagation.

Also in this embodiment, as illustrated inFIG. 8, the laser light sources10may respectively comprise phase control devices14which control the phases of the laser beams11, which are respectively emitted from the laser light sources10. This effectively controls the shapes of the wave fronts of the laser beams21emitted from the light-condensing optics system20to shapes suitable for propagation.

Fifth Embodiment

FIG. 9is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus100D, according to a fifth embodiment. In the fifth embodiment, a collimating optics system50generating a collimated laser beam51from each laser beam11is used in place of the light-condensing optics system20differently from the above-described embodiments, in which the light-condensing optics system20is used. The laser light sources10and the collimating optics system50are housed in the lens barrel30. In the following, a detailed description is given of the configuration of the laser beam irradiation apparatus100D according to this embodiment.

The laser light sources10respectively emit laser beams11. The laser beams11emitted from the laser light sources10are made incident on an incident face50aof the collimating optics system50. As is the case with the first to fourth embodiments, each laser light source10is configured to emit a laser beam11so that the beam diameter of the laser beam11is expanded towards the incident face50aof the collimating optics system50. Additionally, the laser light sources10are arranged so that the laser beam11emitted from each laser light source10overlaps at least one of the laser beams11emitted from the other laser light sources10on the incident face50a. This configuration is useful for generating a high-power synthesized laser beam, while suppressing an increase in the physical size of the laser beam irradiation apparatus100D. Under this aim, when the number of the laser light sources10is three or more, it is preferable that the laser light sources10are arranged so that the laser beam11emitted from each laser light source10overlaps all the laser beams11emitted from the other laser light sources10on the incident face50a.

The collimating optics system50generates laser beams51by performing a predetermined optical operation on the laser beams11incident on the incident face50a, and emits the generated laser beams51from an emitting face50b. Here, the collimating optics system50is configured so that the laser beams51emitted from the emitting face50bare collimated beams. The collimating optics system50is configured so that, when a laser beam11of a beam shape circular symmetric about the optical axis52thereof is made incident on the incident face50a, the beam shape of the laser beam51generated from the laser beam11and emitted from the emitting face50bis circular symmetric about the optical axis52.

In the following, the laser beams51generated from the laser beams111to113and emitted from the emitting face50bmay be referred to as laser beams511to513, respectively. In this embodiment, the collimating optics system50is arranged so that the optical axis52thereof is parallel to the Z axis direction. The laser beams51emitted from the emitting face50bof the collimating optics system50are irradiated on a desired target, overlapping each other. In other words, the laser beams51emitted from the emitting face50bof the collimating optics system50are synthesized to generate a synthesized beam53to be irradiated on the target.

FIG. 10is a diagram illustrating one example intensity distribution of the respective laser beams on the emitting face50bof the collimating optics system50. The intensity distribution of the synthesized laser beam obtained by synthesizing the laser beams51is the superposition of the intensity distributions of the respective laser beams51. When the laser beams11incident on the incident face50aare Gaussian beams and accordingly the laser beams51emitted from the emitting face50bare also Gaussian beams, the intensity distribution of the synthesized laser beam is in a relatively broad Gaussian distribution. In the fifth embodiment, the laser beams51are propagated along the optical axis52so that the intensity distributions of the respective laser beams51are kept unchanged from those on the emitting face50b.

Additionally, in the fifth embodiment, the laser light source10and the collimating optics system50are arranged so that the distance between the optical axis52and the center of each laser beam51emitted from the emitting face50bis smaller than the beam radius of each laser beam51, which is half of the beam diameter (or the spot diameter) of each laser beam51. Also in this embodiment, the beam diameter is defined as the D86 width (the diameter of the circle encompassing 86% of the beam power, the center of the circle being positioned at the geometric center of the beam profile), and the position of the center of each laser beam51is defined as the position of the geometric center of the beam profile of each laser beam51on a plane orthogonal to the optical axis52. This effectively maintains the combination of the laser beams51on the target. Also in this embodiment, in which the laser beams11are made incident on the incident face50aat different positions, the positions of the beam centers of the laser beams51emitted from the emitting face50bmay be different from each other; however, when the distance between the optical axis52and the center of each laser beam51is smaller than the beam radius of each laser beam51, each laser beam51overlaps other laser beams51. This achieves beam combination.

AlthoughFIG. 9illustrates the configuration in which the light-condensing optics system20of the laser beam irradiation apparatus100according to the first embodiment is replaced with the collimating optics system50, the light-condensing optics systems20of the laser beam irradiation apparatuses100A to100C according to the second to fourth embodiments may be replaced with the collimating optics system50.

Multiple laser beam irradiation apparatuses100D according to this embodiment may be provided and synthesized laser beams respectively generated by the laser beam irradiation apparatuses100D may be further combined by using a light-condensing optics system.FIG. 11Ais a diagram schematically illustrating one example configuration of a laser beam irradiation system200A thus configured.

The laser beam irradiation system200A illustrated inFIG. 11Acomprises two laser beam irradiation apparatuses100D. In the following, to distinguish the two laser beam irradiation apparatuses100D from each other, one of the laser beam irradiation apparatuses100D may be referred to as laser beam irradiation apparatus100D1and the other may be may be referred to as laser beam irradiation apparatus100D2.

Each of the two laser beam irradiation apparatuses100D emits a synthesized beam53from the collimating optics system50. In the following, the collimating optics system50of the laser beam irradiation apparatus100D1may be referred to as collimating optics system501and the synthesized beam53emitted from the collimating optics system501may be referred to as synthesized beam531. Correspondingly, the collimating optics system50of the laser beam irradiation apparatus100D2may be referred to as collimating optics system502and the synthesized beam53emitted from the collimating optics system502may be referred to as synthesized beam532.

The synthesized beams531and532emitted from the laser beam irradiation apparatuses100D1and100D2are combined by a beam shaping optical element54and a light-condensing optics system60. In detail, the beam shaping optical element54shapes the wave fronts of the synthesized beams531and532emitted from the laser beam irradiation apparatuses100D1and100D2, respectively. The synthesized beams531and532emitted from the beam shaping optical element54are made incident on an incident face60aof the light-condensing optics system60. The beam shaping optical element54is configured so that the beam diameters of the synthesized beams531and532emitted from the beam shaping optical element54are expanded towards the incident face60a.

The light-condensing optics system60generates laser beams611and612by performing an optical operation on the synthesized beams531and532incident on the incident face60aand emits the generated laser beams611and612from an emitting face60b. The optical operation performed by the light-condensing optics system20comprises an operation for condensing the respective laser beams611and612. In this embodiment, the light-condensing optics system60is arranged so that the optical axis62thereof is parallel to the Z axis direction. The laser beams611and612emitted from the emitting face60bof the light-condensing optics system60are irradiated on a desired target, overlapping with each other.

Similarly to the light-condensing optics system20used in the first embodiment, the light-condensing optics system60is configured so that the laser beams611and612have beam waists on a common target face (that is, the spot diameters are minimal on the common target face), where the target face is a plane defined to be orthogonal to the optical axis62of the light-condensing optics system60; the target face is parallel to the XY plane, in this embodiment. To irradiate the laser beams611and612on a target, the target face is defined to cross the target.

The light-condensing optics system60is further configured so that the beam diameters (or the spot diameters) of both the laser beams611and612are minimal on the target face, which is a plane defined orthogonally to the optical axis62of the light-condensing optics system60, and the distance between the optical axis62and the center of each of the laser beams611and612on the target face is smaller than the beam radius of each of the laser beams611and612on the target face40, where the beam radius of each of the laser beams611and612is half the beam diameter on the target face. As described in the first embodiment, such configuration maintains the combination of the laser beams611and612on the target face.

The laser beam irradiation system200A configured as illustrated inFIG. 11Acan combine an increased number of laser beams while maintaining the light-condensing ability, facilitating generation of a high-power synthesized laser beam.

Multiple laser beam irradiation apparatuses100D according to this embodiment may be provided and synthesized laser beams respectively generated by the laser beam irradiation apparatuses100D may be further combined by using a collimating optics system.FIG. 11Bis a diagram schematically illustrating one example configuration of a laser beam irradiation system.200B thus configured.

The laser beam irradiation system200B illustrated inFIG. 11Bis configured similarly to the laser beam irradiation system200A illustrated inFIG. 11A; a difference is that a collimating optics system70is provided in place of the light-condensing optics system60. The synthesized beams531and532emitted from the beam shaping optical element54are made incident on an incident face70aof the collimating optics system70. The beam shaping optical element54is configured so that the beam diameters of the synthesized beams531and532emitted from the beam shaping optical element54are expanded towards the incident face70a.

The collimating optics system70generates collimated laser beams711and712from the synthesized beams531and532incident on the incident face70a, and emits the generated laser beams711and712from an emitting face70b. In this embodiment, the collimating optics system70is arranged so that the optical axis72thereof is parallel to the Z axis direction. The laser beams711and712emitted from the emitting face70bof the collimating optics system70are irradiated on a desired target, overlapping with each other. In other words, a synthesized beam to be irradiated on the target is generated by synthesizing the laser beams711and712emitted from the emitting face70bof the collimating optics system70. The laser beam irradiation apparatuses100D, the beam shaping optical element54, and the collimating optics system70are arranged so that the distance between the optical axis72and the center of each of the laser beams711and712emitted from the emitting face70bis smaller than the beam radius of each of the laser beams711and712, where the beam radius of each of the laser beams711and712is half the beam diameter (or the spot diameter) of the same.

The laser beam irradiation system200B configured as illustrated inFIG. 11Bcan combine an increased number of laser beams, facilitating generation of a high-power synthesized laser beam.

Sixth Embodiment

FIG. 12is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus100E, according to a sixth embodiment. The laser beam irradiation apparatus100E according to the sixth embodiment is configured similarly to the laser beam irradiation apparatus100D according to the fifth embodiment (seeFIG. 9); a difference is that the laser beam irradiation apparatus100E according to the sixth embodiment additionally comprises a solid state laser amplifier80. The solid state laser amplifier80generates an amplified laser beam81by performing laser amplification on the laser beams51emitted from the emitting face50bof the collimating optics system50. The configuration of the laser beam irradiation apparatus100E according to the sixth embodiment is advantageous for generating a high-power laser beam while reducing the number of laser light sources10included in the laser beam irradiation apparatus100E.

The laser beam irradiation apparatus100E according to this embodiment is especially useful when fiber lasers are used as the laser devices12of the laser light sources10, especially when fiber lasers generating pulsed light or laser light of a narrow linewidth are used. The allowed maximum pulse energy of a fiber laser is small although a fiber laser has a higher efficiency than a solid-state laser in a low power region. In contrast, the allowed maximum pulse energy of a solid-state laser is large. A fiber laser suffers from a reduced upper limit of the output power for a reduced line width due to significant non-linear effects, while a solid-state laser, which exhibits reduced non-linear effects, can offer both of a narrow linewidth and a high power at the same time. A configuration in which laser light generated by a fiber laser is amplified by a solid-state laser is advantageous for making use of such properties of the fiber laser and the solid state laser. The laser beam irradiation apparatus100E according to this embodiment, which uses fiber lasers as the laser devices12of the laser light sources10, effectively provides a configuration in which a plurality of laser beams generated by the fiber lasers are combined and amplified by the solid state laser amplifier80.

Although embodiments of the present invention have been specifically described in the above, the present invention is not limited to the above-described embodiments. A person skilled in the art would understand that the present invention may be implemented with various modifications. It should also be noted that the above-described embodiments may be combined in an actual implementation as long as there is no technical inconsistency.

The present application, which is based on Japanese patent application No. 2017-145402, filed on Jul. 27, 2017, claims priority based on the convention. The disclosure of the same is incorporated herein by reference in its entirety.