Patent Description:
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 <CIT>, for example.

Another example of a method and laser beam irradiation system for irradiating a target is disclosed in <CIT>. In the method and system, at least one fiber laser comprising a pump source and a laser fiber has an infeed end, an outfeed end, and a core surrounded by a pump core, the pump source being positioned at the infeed end, and the laser fiber outputting a continuous wave laser beam at the outfeed end. A focusing optics is provided through which the laser beam passes. The laser beam output from the laser fiber is diffraction-limited to permit the focusing optics to focus the laser beam onto a target surface as a spot having a spot size sufficiently small to create a fine structure by processing target material at the target surface.

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.

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.

According to the present invention, there is provided a laser beam irradiation apparatus as set out in independent claim <NUM> Advantageous developments are defined in the dependent claims.

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.

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 not claimed embodiment useful for understanding the present invention, 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 not claimed embodiment useful for understanding the present invention, 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 anothernot claimed embodiment useful for understanding the present invention, 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 present invention effectively provides a technique for obtaining a high-power synthesized laser beams by combining a plurality of laser beams.

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.

<FIG> is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus <NUM>, according to a first embodiment. The laser beam irradiation apparatus <NUM> comprises a plurality of laser light sources <NUM> and a light-condensing optics system <NUM>. The laser light sources <NUM> and the light-condensing optics system <NUM> are housed in a lens barrel <NUM>. In the following, suffixes are attached when the plurality of laser light sources <NUM> are distinguished from each other. In <FIG>, three laser light sources <NUM><NUM> to <NUM><NUM> are illustrated. The number of the laser light sources <NUM> is not limited to three; four or more laser light sources <NUM> may be provided.

Each laser light source <NUM> emits a laser beam <NUM>. In detail, each laser light source <NUM> comprises a laser device <NUM> and an optical fiber <NUM> in this embodiment. A laser beam generated by a laser device <NUM> is made incident on one end of an optical fiber <NUM>, and emitted from the other end as a laser beam <NUM>. In the following, the laser beams <NUM> emitted from the laser light sources <NUM><NUM> to <NUM><NUM> may be referred to as laser beams <NUM><NUM> to <NUM><NUM>, respectively. In this embodiment, the laser light sources <NUM> emit the laser beams <NUM> from different positions in the Y axis direction. The laser beams <NUM> emitted from the laser light source <NUM> are made incident on an incident face 20a of the light-condensing optics system <NUM>.

The light-condensing optics system <NUM> generates laser beams <NUM> by performing an optical operation on the laser beams <NUM> incident on the incident face 20a, and emits the generated laser beams <NUM> from an emitting face 20b. The optical operation performed by the light-condensing optics system <NUM> comprises an operation for condensing the respective laser beams <NUM>. In the following, the laser beams <NUM> generated from the laser beams <NUM><NUM> to <NUM><NUM> and emitted from the emitting face 20b may be referred to as laser beams <NUM><NUM> to <NUM><NUM>, respectively. In this embodiment, the light-condensing optics system <NUM> is arranged so that the optical axis <NUM> thereof is parallel to the Z axis direction. The laser beams <NUM> emitted from the emitting face 20b of the light-condensing optics system <NUM> are irradiated on a desired target, overlapping each other.

In the laser beam irradiation apparatus <NUM> according to this embodiment, each laser light source <NUM> is configured to emit a laser beam <NUM> so that the beam diameter of the laser beam <NUM> is expanded toward the incident face 20a of the light-condensing optics system <NUM>. 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 beams <NUM> emitted from the optical fibers <NUM> towards the incident face 20a of the light-condensing optics system <NUM>. Alternatively, an optical element such as a lens may be coupled to an optical fiber <NUM> to expand the beam diameter of a laser beam <NUM> emitted from the optical fiber <NUM> towards the incident face 20a of the light-condensing optics system <NUM>.

Additionally, the laser light sources <NUM> are arranged so that the laser beam <NUM> emitted from each laser light source <NUM> overlaps at least one of the laser beams <NUM> emitted from the other laser light sources <NUM> on the incident face 20a. 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 apparatus <NUM>. Under this aim, when the number of the laser light sources <NUM> is three or more, it is preferable that the laser light sources <NUM> are arranged so that the laser beam <NUM> emitted from each laser light source <NUM> overlaps all the laser beams <NUM> emitted from the other laser light sources <NUM> on the incident face 20a.

The light-condensing optics system <NUM> is configured as follows. First, the light-condensing optics system <NUM> is configured so that, when a laser beam <NUM> of a beam shape circular symmetric about the optical axis <NUM> is made incident on the incident face 20a, the beam shape of a laser beam <NUM> generated from the laser beam <NUM> and emitted from the emitting face 20b is circular symmetric about the optical axis <NUM>.

The light-condensing optics system <NUM> is further configured so that the beam diameters (or the spot diameters) of all the laser beams <NUM> emitted from the emitting face 20b are minimal on a target face <NUM> which is a plane defined orthogonally to the optical axis <NUM> of the light-condensing optics system <NUM>. In this embodiment, the target face <NUM> is parallel to the XY plane. When the laser beams <NUM> are irradiated on a target, the target face <NUM> is set so that the target face <NUM> crosses the target. This implies that the light-condensing optics system <NUM> is configured to focus the respective laser beams <NUM> on the target face <NUM>. The light-condensing optics system <NUM> may be configured so that the position of the target face <NUM> is adjustable in a direction parallel to the optical axis <NUM>.

The light-condensing optics system <NUM> is further configured so that the distance between the optical axis <NUM> and the center of each laser beam <NUM> on the target face <NUM> is smaller than the beam radius of each laser beam <NUM> on the target face <NUM>, where the beam radius is half the beam diameter. The beam diameter on the target face <NUM> is defined as the D86 width (the diameter of the circle encompassing <NUM>% of the beam power, the center of the circle being positioned at the geometric center of the beam profile). The position of the center of each laser beam <NUM> on the target face <NUM> is defined as the position of the geometric center of the beam profile of each laser beam <NUM> on the target face <NUM>. <FIG> are diagram illustrating the beam shapes of the respective laser beams <NUM>, according to this embodiment.

<FIG> illustrates the beam shape of the laser beam <NUM><NUM> generated by the light-condensing optics system <NUM> from the laser beam <NUM><NUM> emitted from the laser light source <NUM><NUM>. As illustrated in <FIG>, the beam diameter of the laser beam <NUM><NUM> is minimal on the target face <NUM>. The distance d<NUM> between the optical axis <NUM> and the center <NUM><NUM> of the laser beam <NUM><NUM> on the target face <NUM> is smaller than the beam radius r<NUM> of the laser beam <NUM><NUM> on the target face <NUM> (that is, half the beam diameter of the laser beam <NUM><NUM> on the target face <NUM>). In other words, the following expression (<NUM>) holds: <MAT>.

<FIG> illustrates the beam shape of the laser beam <NUM><NUM> generated by the light-condensing optics system <NUM> from the laser beam <NUM><NUM> emitted from the laser light source <NUM><NUM>. The beam shape of the laser beam <NUM><NUM> emitted from the laser light source <NUM><NUM> is circular symmetric about the optical axis <NUM>, and accordingly the beam shape of the laser beam <NUM><NUM>, which is emitted from the light-condensing optics system <NUM>, is also circular symmetric about the optical axis <NUM>.

As illustrated in <FIG>, the beam diameter of the laser beam <NUM><NUM> is minimal on the target face <NUM>, as is the case with the laser beam <NUM><NUM>. The center <NUM><NUM> of the laser beam <NUM><NUM> on the target face <NUM> is positioned on the optical axis <NUM>, and the distance d<NUM> between the optical axis <NUM> and the center <NUM><NUM> of the laser beam <NUM><NUM> on the target face <NUM> is zero. Accordingly, the following expression (<NUM>) holds also for the laser beam <NUM><NUM>: <MAT> where r<NUM> is the beam radius of the laser beam <NUM><NUM> on the target face <NUM> (that is, half the beam diameter of the laser beam <NUM><NUM> on the target face <NUM>).

<FIG> illustrates the beam shape of the laser beam <NUM><NUM> generated by the light-condensing optics system <NUM> from the laser beam <NUM><NUM> emitted from the laser light source <NUM><NUM>. As illustrated in <FIG>, the beam diameter of the laser beam <NUM><NUM> is also minimal on the target face <NUM>. The distance d<NUM> between the optical axis <NUM> and the center <NUM><NUM> of the laser beam <NUM><NUM> on the target face <NUM> is smaller than the beam radius r<NUM> of the laser beam <NUM><NUM> on the target face <NUM> (that is, half the beam diameter of the laser beam <NUM><NUM> on the target face <NUM>). In other words, the following expression (<NUM>) holds: <MAT>.

The condition that the distance between the optical axis <NUM> and the center of each laser beam <NUM> on the target face <NUM> is smaller than the beam radius of each laser beam <NUM> is for maintaining the combination of the laser beams <NUM> on the target face <NUM>. In this embodiment, since the laser beams <NUM> are made incident on the incident face 20a at different positions, the positions of the beam centers on the target face <NUM> of the laser beams <NUM> emitted from the emitting face 20b may be different from each other; however, when the distance between the optical axis <NUM> and the center of each laser beam <NUM> on the target face <NUM> is smaller than the beam radius of each laser beam <NUM> on the target face <NUM>, each laser beam <NUM> overlaps all other laser beams <NUM> on the target face <NUM>. 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 apparatus <NUM> and improvement in the light-condensing ability.

In detail, the laser light sources <NUM> are arranged so that the laser beam <NUM> emitted from each laser light source <NUM> overlaps at least one of the laser beams <NUM> emitted from the other laser light sources <NUM> on the incident face 20a, 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 apparatus <NUM>. When the number of the laser beams <NUM> is 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 beam <NUM> emitted by each laser light source <NUM> overlaps the laser beams <NUM> emitted by all other laser light sources <NUM> on the incident face 20a.

Additionally, in the laser beam irradiation apparatus <NUM> according to this embodiment, each of the laser light sources <NUM> is configured to emit the laser beam <NUM> so that the beam diameter of the laser beam <NUM> is expanded towards the incident face 20a of the light-condensing optics system <NUM>. Accordingly, the beam diameter of each laser beam <NUM> is enlarged on the emitting face 20b of the light-condensing optics system <NUM>. This implies that the focal spot diameter of each laser beam <NUM> can be reduced on the target face <NUM>. This effectively improves the light-condensing ability.

It should also be noted that the laser beam irradiation apparatus <NUM> offers laser beam combination without using a special optical element such as a diffraction optical element. The laser beam irradiation apparatus <NUM> according 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.

<FIG> is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus 100A, according to a second embodiment. The laser beam irradiation apparatus 100A according to the second embodiment is configured similarly to the laser beam irradiation apparatus <NUM> according to the first embodiment; a difference from the laser beam irradiation apparatus <NUM> according to the first embodiment is that each laser light source <NUM> comprises a phase control device <NUM> controlling the phase of the laser beam <NUM> emitted from the laser light source <NUM>. In this embodiment, the phase control device <NUM> is inserted into the optical fiber <NUM> of each laser light source <NUM>.

In the laser beam irradiation apparatus 100A according to the second embodiment, the phases of the laser beams <NUM> incident on the light-condensing optics system <NUM> are controlled by the phase control devices <NUM> and this achieves control of the shapes of the wave fronts of the laser beams <NUM> emitted from the light-condensing optics system <NUM> to shapes suitable for propagation. This effectively improves the light-condensing ability. The phases of the laser beams <NUM> may be made the same on the emitting face 20b of the light-condensing optics system <NUM>, for example, by controlling the phases of the laser beams <NUM> emitted from the laser light sources <NUM> with the phase control devices <NUM>. This achieves aperture synthesis, improving the light-condensing ability.

<FIG> is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus 100B, according to a third embodiment. The laser beam irradiation apparatus 100B according to the third embodiment is configured similarly to the laser beam irradiation apparatus <NUM> according to the first embodiment; a difference from the laser beam irradiation apparatus <NUM> according to the first embodiment is that the laser beam irradiation apparatus 100B according to the third embodiment comprises beam shaping optics systems <NUM> which respectively shape the wave fronts of the laser beams <NUM> emitted from the laser light sources <NUM>. In this embodiment, the beam shaping optics systems <NUM> are coupled to light-emitting ends of the optical fibers <NUM> of the respective laser light sources <NUM>, the laser beams <NUM> being emitted from the light-emitting ends. Optical elements such as concave lenses and convex lenses may be used as the beam shaping optics systems <NUM>.

In the third embodiment, the wave fronts of the laser beams <NUM> emitted from the respective laser light sources <NUM> are shaped by the beam shaping optics systems <NUM> and this successfully controls the shapes of the wave fronts of the laser beams <NUM> emitted from the light-condensing optics system <NUM> to shapes suitable for propagation. This effectively improves the light-condensing ability.

Although <FIG> illustrates the configuration in which each laser light source <NUM> comprises a beam shaping optics system <NUM>, a common beam shaping optics system <NUM> may instead be provided for a plurality of laser light sources <NUM> as illustrated in <FIG>. The beam shaping optics system <NUM> shapes the wave fronts of the laser beams <NUM> emitted from the respective laser light sources <NUM> and thereby controls the shapes of the wave fronts of the laser beams <NUM> emitted from the light-condensing optics system <NUM> to shapes suitable for propagation.

As illustrated in <FIG>, the laser beam irradiation apparatus 100B according to the second embodiment, which comprises the phase control devices <NUM>, may further comprise the beam shaping optics systems <NUM> (or the beam shaping optics system <NUM>). In this case, since the phases of the laser beams <NUM> incident on the respective beam shaping optics systems <NUM> are controlled, it is possible to control the shapes of the wave fronts of the laser beams <NUM> emitted from the light-condensing optics system <NUM> to shapes suitable for propagation, while the configurations of the beam shaping optics systems <NUM> are simplified.

<FIG> is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus 100C, according to a fourth embodiment. The laser beam irradiation apparatus 100C according to the fourth embodiment is configured similarly to the laser beam irradiation apparatus <NUM> according to the first embodiment; a difference from the laser beam irradiation apparatus <NUM> according to the first embodiment is that the laser light sources <NUM> are coupled to the incident face 20a of the light-condensing optics system <NUM> with a coupling optical element <NUM>. In this embodiment, the coupling optical element <NUM> is coupled to the light-emitting ends of the optical fibers <NUM> of the respective laser light sources <NUM>, the laser beams <NUM> being emitted from the light-emitting ends. Examples of the coupling optical element <NUM> include a tapered lens. The coupling optical element <NUM> may be coupled to the optical fibers <NUM> by fusion bonding. The coupling optical element <NUM> is configured to guide the laser beams <NUM> emitted from the optical fibers <NUM> of the respective laser light sources <NUM> to the incident face 20a of the light-condensing optics system <NUM>.

In this embodiment, the coupling optical element <NUM>, which is coupled to the light-emitting ends of the optical fibers <NUM>, effectively facilitates the alignment of the optical fibers <NUM>. Note that the coupling optical element <NUM> may have the function of shaping the wave fronts of the laser beams <NUM> emitted from the respective laser light sources <NUM>. This is useful for controlling the shapes of the wave fronts of the laser beams <NUM> emitted from the light-condensing optics system <NUM> to shapes suitable for propagation.

Also in this embodiment, as illustrated in <FIG>, the laser light sources <NUM> may respectively comprise phase control devices <NUM> which control the phases of the laser beams <NUM>, which are respectively emitted from the laser light sources <NUM>. This effectively controls the shapes of the wave fronts of the laser beams <NUM> emitted from the light-condensing optics system <NUM> to shapes suitable for propagation.

<FIG> is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus 100D, according to a fifth embodiment. In the fifth embodiment, a collimating optics system <NUM> generating a collimated laser beam <NUM> from each laser beam <NUM> is used in place of the light-condensing optics system <NUM> differently from the above-described embodiments, in which the light-condensing optics system <NUM> is used. The laser light sources <NUM> and the collimating optics system <NUM> are housed in the lens barrel <NUM>. In the following, a detailed description is given of the configuration of the laser beam irradiation apparatus 100D according to this embodiment.

The laser light sources <NUM> respectively emit laser beams <NUM>. The laser beams <NUM> emitted from the laser light sources <NUM> are made incident on an incident face 50a of the collimating optics system <NUM>. As is the case with the first to fourth embodiments, each laser light source <NUM> is configured to emit a laser beam <NUM> so that the beam diameter of the laser beam <NUM> is expanded towards the incident face 50a of the collimating optics system <NUM>. Additionally, the laser light sources <NUM> are arranged so that the laser beam <NUM> emitted from each laser light source <NUM> overlaps at least one of the laser beams <NUM> emitted from the other laser light sources <NUM> on the incident face 50a. 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 apparatus 100D. Under this aim, when the number of the laser light sources <NUM> is three or more, it is preferable that the laser light sources <NUM> are arranged so that the laser beam <NUM> emitted from each laser light source <NUM> overlaps all the laser beams <NUM> emitted from the other laser light sources <NUM> on the incident face 50a.

The collimating optics system <NUM> generates laser beams <NUM> by performing a predetermined optical operation on the laser beams <NUM> incident on the incident face 50a, and emits the generated laser beams <NUM> from an emitting face 50b. Here, the collimating optics system <NUM> is configured so that the laser beams <NUM> emitted from the emitting face 50b are collimated beams. The collimating optics system <NUM> is configured so that, when a laser beam <NUM> of a beam shape circular symmetric about the optical axis <NUM> thereof is made incident on the incident face 50a, the beam shape of the laser beam <NUM> generated from the laser beam <NUM> and emitted from the emitting face 50b is circular symmetric about the optical axis <NUM>.

In the following, the laser beams <NUM> generated from the laser beams <NUM><NUM> to <NUM><NUM> and emitted from the emitting face 50b may be referred to as laser beams <NUM><NUM> to <NUM><NUM>, respectively. In this embodiment, the collimating optics system <NUM> is arranged so that the optical axis <NUM> thereof is parallel to the Z axis direction. The laser beams <NUM> emitted from the emitting face 50b of the collimating optics system <NUM> are irradiated on a desired target, overlapping each other. In other words, the laser beams <NUM> emitted from the emitting face 50b of the collimating optics system <NUM> are synthesized to generate a synthesized beam <NUM> to be irradiated on the target.

<FIG> is a diagram illustrating one example intensity distribution of the respective laser beams on the emitting face 50b of the collimating optics system <NUM>. The intensity distribution of the synthesized laser beam obtained by synthesizing the laser beams <NUM> is the superposition of the intensity distributions of the respective laser beams <NUM>. When the laser beams <NUM> incident on the incident face 50a are Gaussian beams and accordingly the laser beams <NUM> emitted from the emitting face 50b are also Gaussian beams, the intensity distribution of the synthesized laser beam is in a relatively broad Gaussian distribution. In the fifth embodiment, the laser beams <NUM> are propagated along the optical axis <NUM> so that the intensity distributions of the respective laser beams <NUM> are kept unchanged from those on the emitting face 50b.

Additionally, in the fifth embodiment, the laser light source <NUM> and the collimating optics system <NUM> are arranged so that the distance between the optical axis <NUM> and the center of each laser beam <NUM> emitted from the emitting face 50b is smaller than the beam radius of each laser beam <NUM>, which is half of the beam diameter (or the spot diameter) of each laser beam <NUM>. Also in this embodiment, the beam diameter is defined as the D86 width (the diameter of the circle encompassing <NUM>% 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 beam <NUM> is defined as the position of the geometric center of the beam profile of each laser beam <NUM> on a plane orthogonal to the optical axis <NUM>. This effectively maintains the combination of the laser beams <NUM> on the target. Also in this embodiment, in which the laser beams <NUM> are made incident on the incident face 50a at different positions, the positions of the beam centers of the laser beams <NUM> emitted from the emitting face 50b may be different from each other; however, when the distance between the optical axis <NUM> and the center of each laser beam <NUM> is smaller than the beam radius of each laser beam <NUM>, each laser beam <NUM> overlaps other laser beams <NUM>. This achieves beam combination.

Although <FIG> illustrates the configuration in which the light-condensing optics system <NUM> of the laser beam irradiation apparatus <NUM> according to the first embodiment is replaced with the collimating optics system <NUM>, the light-condensing optics systems <NUM> of the laser beam irradiation apparatuses 100A to 100C according to the second to fourth embodiments may be replaced with the collimating optics system <NUM>.

Multiple laser beam irradiation apparatuses 100D according to this embodiment may be provided and synthesized laser beams respectively generated by the laser beam irradiation apparatuses 100D may be further combined by using a light-condensing optics system. <FIG> is a diagram schematically illustrating one example configuration of a laser beam irradiation system 200A thus configured.

The laser beam irradiation system 200A illustrated in <FIG> comprises two laser beam irradiation apparatuses 100D. In the following, to distinguish the two laser beam irradiation apparatuses 100D from each other, one of the laser beam irradiation apparatuses 100D may be referred to as laser beam irradiation apparatus 100D<NUM> and the other may be may be referred to as laser beam irradiation apparatus 100D<NUM>.

Each of the two laser beam irradiation apparatuses 100D emits a synthesized beam <NUM> from the collimating optics system <NUM>. In the following, the collimating optics system <NUM> of the laser beam irradiation apparatus 100D<NUM> may be referred to as collimating optics system <NUM><NUM> and the synthesized beam <NUM> emitted from the collimating optics system <NUM><NUM> may be referred to as synthesized beam <NUM><NUM>. Correspondingly, the collimating optics system <NUM> of the laser beam irradiation apparatus 100D<NUM> may be referred to as collimating optics system <NUM><NUM> and the synthesized beam <NUM> emitted from the collimating optics system <NUM><NUM> may be referred to as synthesized beam <NUM><NUM>.

The synthesized beams <NUM><NUM> and <NUM><NUM> emitted from the laser beam irradiation apparatuses 100D<NUM> and 100D<NUM> are combined by a beam shaping optical element <NUM> and a light-condensing optics system <NUM>. In detail, the beam shaping optical element <NUM> shapes the wave fronts of the synthesized beams <NUM><NUM> and <NUM><NUM> emitted from the laser beam irradiation apparatuses 100D<NUM> and 100D<NUM>, respectively. The synthesized beams <NUM><NUM> and <NUM><NUM> emitted from the beam shaping optical element <NUM> are made incident on an incident face 60a of the light-condensing optics system <NUM>. The beam shaping optical element <NUM> is configured so that the beam diameters of the synthesized beams <NUM><NUM> and <NUM><NUM> emitted from the beam shaping optical element <NUM> are expanded towards the incident face 60a.

The light-condensing optics system <NUM> generates laser beams <NUM><NUM> and <NUM><NUM> by performing an optical operation on the synthesized beams <NUM><NUM> and <NUM><NUM> incident on the incident face 60a and emits the generated laser beams <NUM><NUM> and <NUM><NUM> from an emitting face 60b. The optical operation performed by the light-condensing optics system <NUM> comprises an operation for condensing the respective laser beams <NUM><NUM> and <NUM><NUM>. In this embodiment, the light-condensing optics system <NUM> is arranged so that the optical axis <NUM> thereof is parallel to the Z axis direction. The laser beams <NUM><NUM> and <NUM><NUM> emitted from the emitting face 60b of the light-condensing optics system <NUM> are irradiated on a desired target, overlapping with each other.

Similarly to the light-condensing optics system <NUM> used in the first embodiment, the light-condensing optics system <NUM> is configured so that the laser beams <NUM><NUM> and <NUM><NUM> have 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 axis <NUM> of the light-condensing optics system <NUM>; the target face is parallel to the XY plane, in this embodiment. To irradiate the laser beams <NUM><NUM> and <NUM><NUM> on a target, the target face is defined to cross the target.

The light-condensing optics system <NUM> is further configured so that the beam diameters (or the spot diameters) of both the laser beams <NUM><NUM> and <NUM><NUM> are minimal on the target face, which is a plane defined orthogonally to the optical axis <NUM> of the light-condensing optics system <NUM>, and the distance between the optical axis <NUM> and the center of each of the laser beams <NUM><NUM> and <NUM><NUM> on the target face is smaller than the beam radius of each of the laser beams <NUM><NUM> and <NUM><NUM> on the target face <NUM>, where the beam radius of each of the laser beams <NUM><NUM> and <NUM><NUM> is half the beam diameter on the target face. As described in the first embodiment, such configuration maintains the combination of the laser beams <NUM><NUM> and <NUM><NUM> on the target face.

The laser beam irradiation system 200A configured as illustrated in <FIG> can 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 apparatuses 100D according to this embodiment may be provided and synthesized laser beams respectively generated by the laser beam irradiation apparatuses 100D may be further combined by using a collimating optics system. <FIG> is a diagram schematically illustrating one example configuration of a laser beam irradiation system 200B thus configured.

The laser beam irradiation system 200B illustrated in <FIG> is configured similarly to the laser beam irradiation system 200A illustrated in <FIG>; a difference is that a collimating optics system <NUM> is provided in place of the light-condensing optics system <NUM>. The synthesized beams <NUM><NUM> and <NUM><NUM> emitted from the beam shaping optical element <NUM> are made incident on an incident face 70a of the collimating optics system <NUM>. The beam shaping optical element <NUM> is configured so that the beam diameters of the synthesized beams <NUM><NUM> and <NUM><NUM> emitted from the beam shaping optical element <NUM> are expanded towards the incident face 70a.

The collimating optics system <NUM> generates collimated laser beams <NUM><NUM> and <NUM><NUM> from the synthesized beams <NUM><NUM> and <NUM><NUM> incident on the incident face 70a, and emits the generated laser beams <NUM><NUM> and <NUM><NUM> from an emitting face 70b. In this embodiment, the collimating optics system <NUM> is arranged so that the optical axis <NUM> thereof is parallel to the Z axis direction. The laser beams <NUM><NUM> and <NUM><NUM> emitted from the emitting face 70b of the collimating optics system <NUM> are 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 beams <NUM><NUM> and <NUM><NUM> emitted from the emitting face 70b of the collimating optics system <NUM>. The laser beam irradiation apparatuses 100D, the beam shaping optical element <NUM>, and the collimating optics system <NUM> are arranged so that the distance between the optical axis <NUM> and the center of each of the laser beams <NUM><NUM> and <NUM><NUM> emitted from the emitting face 70b is smaller than the beam radius of each of the laser beams <NUM><NUM> and <NUM><NUM>, where the beam radius of each of the laser beams <NUM><NUM> and <NUM><NUM> is half the beam diameter (or the spot diameter) of the same.

The laser beam irradiation system 200B configured as illustrated in <FIG> can combine an increased number of laser beams, facilitating generation of a high-power synthesized laser beam.

<FIG> is a diagram schematically illustrating the configuration of a laser beam irradiation apparatus 100E, according to a sixth embodiment. The laser beam irradiation apparatus 100E according to the sixth embodiment is configured similarly to the laser beam irradiation apparatus 100D according to the fifth embodiment (see <FIG>); a difference is that the laser beam irradiation apparatus 100E according to the sixth embodiment additionally comprises a solid state laser amplifier <NUM>. The solid state laser amplifier <NUM> generates an amplified laser beam <NUM> by performing laser amplification on the laser beams <NUM> emitted from the emitting face 50b of the collimating optics system <NUM>. The configuration of the laser beam irradiation apparatus 100E according to the sixth embodiment is advantageous for generating a high-power laser beam while reducing the number of laser light sources <NUM> included in the laser beam irradiation apparatus 100E.

The laser beam irradiation apparatus 100E according to this embodiment is especially useful when fiber lasers are used as the laser devices <NUM> of the laser light sources <NUM>, 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 linewidth 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 apparatus 100E according to this embodiment, which uses fiber lasers as the laser devices <NUM> of the laser light sources <NUM>, 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 amplifier <NUM>.

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.

Claim 1:
A laser beam irradiation apparatus (<NUM>, 100A-E) configured to irradiate a target, comprising:
a plurality of laser light sources (<NUM>, <NUM>-<NUM>) configured for emitting first laser beams, respectively; and
a light-condensing optics system (<NUM>, <NUM>) comprising an incident face (20a, 50a, 60a, 70a) configured for making the first laser beams incident thereon and performing an optical operation on the first laser beams to emit second laser beams associated with the first laser beams, respectively,
wherein the plurality of laser light sources (<NUM>, <NUM>-<NUM>) 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 (20a, 50a, 60a, 70a) of the light-condensing optics system (<NUM>, <NUM>),
wherein each of the first laser beams when emitted from the plurality of laser light sources (<NUM>, <NUM>-<NUM>) overlaps at least one of the other first laser beams on the incident face (20a, 50a, 60a, 70a) of the light-condensing optics system (<NUM>, <NUM>), and
wherein the light-condensing optics system (<NUM>, <NUM>) is configured so that beam diameters of all the second laser beams when emitted from the light-condensing optics system (<NUM>, <NUM>) are minimal on a target face (<NUM>) of the target which is a plane defined to be orthogonal to an optical axis (<NUM>, <NUM>, <NUM>, <NUM>) of the light-condensing optics system (<NUM>, <NUM>), and a distance between a center (<NUM>-<NUM>) of each of the second laser beams and the optical axis (<NUM>, <NUM>, <NUM>, <NUM>) on the target face (<NUM>) is smaller than a beam radius which is half a beam diameter of each of the second laser beams on the target face (<NUM>), the beam diameter on the target face (<NUM>) being defined as a diameter of a circle encompassing <NUM>% of the beam power, where the center of the circle being positioned at the geometric center of the beam profile; and wherein each of the first laser beams when emitted from the plurality of laser light sources (<NUM>, <NUM>-<NUM>) overlaps all other first laser beams on the incident face (20a, 50a, 60a, 70a) of the light-condensing optics system (<NUM>, <NUM>).