JP6807662B2 - Method for manufacturing laser oscillator and excitation light detection structure - Google Patents

Description

The present invention relates to a laser oscillator and a method for manufacturing an excitation light detection structure.

In order to cut an object to be processed such as a semiconductor wafer into a plurality of chips, a laser processing apparatus is known that forms a modified region inside the object to be processed along a scheduled cutting line set in a grid pattern ( For example, see Patent Document 1).

Japanese Patent No. 5456510

A fiber laser may be used in the laser oscillator mounted on the laser processing apparatus as described above. The fiber laser amplifies and outputs the seed light by introducing the excitation light and the seed light into the laser fiber. In a fiber laser, it is desirable to detect the excitation light, for example, for detailed failure analysis.

An object of the present invention is to provide a laser oscillator capable of detecting excitation light and a method for manufacturing an excitation light detection structure.

The laser oscillator according to the present invention includes a seed light emitting unit having a seed light source that emits laser light that is seed light, and a first optical fiber for amplifying the laser light emitted from the seed light emitting unit while propagating it. , To detect the excitation light that emits the excitation light for exciting the first optical fiber, the second optical fiber that is optically connected to the first optical fiber and propagates the excitation light at least, and the excitation light. The second optical fiber includes a core, a first clad provided around the core, and a core and a second clad provided around the first clad. And a resin layer provided around the core and the first clad, the first clad covers the core and is covered with the second clad, and is exposed from the second clad while covering the core. The resin layer has a refractive index lower than that of the first clad, and covers the first clad in the exposed portion. The light detection element is the exposed portion via the resin layer. It is arranged so as to face the light.

In this laser oscillator, the first optical fiber is excited by the excitation light propagated by the second optical fiber. As a result, the seed light from the seed light source is amplified while being propagated through the first optical fiber. That is, the first optical fiber is a laser fiber. On the other hand, in the second optical fiber, the first clad covering the core includes an exposed portion exposed from the second clad. The exposed portion of the first clad is covered with a resin layer having a refractive index lower than that of the first clad. Then, the photodetection element is arranged so as to face the exposed portion of the first clad via the resin layer. Therefore, the leakage light of the excitation light propagating through the first clad and emitted from the exposed portion can be detected by the photodetector via the resin layer.

In the laser oscillator according to the present invention, the exposed portion may include a fusion portion with the first optical fiber. In this case, it becomes easy to expose the first clad from the second clad to form an exposed portion, or to cover the exposed portion with a resin layer. That is, in this case, the excitation light can be easily detected by using the fused portion.

In the laser oscillator according to the present invention, the second optical fiber has a refractive index higher than the refractive index of the resin layer, and may include a capillary that further covers the resin layer in the exposed portion. In this case, the excitation light can be easily leaked from the resin layer.

The laser oscillator according to the present invention may include a holder for holding the photodetection element, and the second optical fiber may be positioned by the holder so that the exposed portion faces the photodetection element. In this case, the relative positional relationship between the exposed portion of the second optical fiber and the photodetector can be reliably maintained.

The method for manufacturing an excitation light detection structure according to the present invention includes a first optical fiber that amplifies while propagating laser light, and a second optical fiber that propagates at least excitation light for exciting the first optical fiber. A method for manufacturing an excitation light detection structure for detecting excitation light in a laser oscillator, which is a core, a first clad provided around the core, and a core and a second clad provided around the first clad. In the second optical fiber including, the first step of exposing the first clad by removing the second clad to form an exposed portion, and by cutting the second optical fiber in a part of the exposed portion. It has a second step of forming a cut surface, a third step of fusing and connecting an exposed portion to a first optical fiber on the cut surface to form a fused portion, and a refractive index lower than that of the first clad. The present invention includes a fourth step of forming the resin layer on the first clad so as to cover the exposed portion, and a fifth step of making the exposed portion face the light detection element via the resin layer.

In this method, the first clad is exposed by removing the second clad to form an exposed portion. Subsequently, the second optical fiber is cut, the second optical fiber is fused and connected to the first optical fiber at the cut surface, and the exposed portion is covered with a resin layer having a low refractive index by the first clad. Then, the exposed portion is made to face the photodetection element. As a result, the excitation light detection structure is manufactured. In the excitation light detection structure manufactured in this way, as described above, the leakage light of the excitation light propagating through the first cladding and emitted from the exposed portion can be detected by the photodetector. In particular, according to this method, the second optical fiber is cut after the exposed portion is formed by removing the second clad, so that a good cut surface can be obtained. Therefore, the loss in the fused portion is reduced.

According to the present invention, it is possible to provide a laser oscillator capable of detecting excitation light and a method for manufacturing an excitation light detection structure.

It is a schematic block diagram of the laser processing apparatus used for forming a reforming region. It is a top view of the processing object which is the object of formation of the modification region. It is sectional drawing along the line III-III of the processing object of FIG. It is a top view of the processing object after laser processing. It is sectional drawing along the VV line of the processing object of FIG. It is sectional drawing along the VI-VI line of the processing object of FIG. It is a perspective view of the laser processing apparatus of an embodiment. It is a perspective view of the processing object attached to the support base of the laser processing apparatus of FIG. It is sectional drawing of the laser output part along the XY plane of FIG. It is a perspective view of a part of a laser output part and a laser condensing part in the laser processing apparatus of FIG. It is a figure which shows the optical arrangement relation of the λ / 2 wave plate unit and the polarizing plate unit in the laser output part of FIG. FIG. 9A is a diagram showing the polarization direction of the λ / 2 wave plate unit of the laser output unit of FIG. 9, and FIG. 9B is a diagram showing the polarization direction of the polarizing plate unit of the laser output unit of FIG. It is a figure which shows the whole structure of the laser oscillator of an embodiment. It is a front view of the laser oscillator of an embodiment. It is a figure which shows the internal structure of the laser oscillator of FIG. It is a figure which shows the internal structure of the laser oscillator of FIG. It is a figure which shows the internal structure of the laser oscillator of FIG. It is a figure which shows the internal structure of the laser oscillator of FIG. It is a figure which shows the internal structure of the laser oscillator of FIG. It is a figure which shows the internal structure of the laser oscillator of FIG. It is a bottom view of the excitation light detection structure shown in FIG. It is a schematic enlarged sectional view of the excitation light detection structure shown in FIG. It is an exploded perspective view of the holder shown in FIG. It is a perspective view of the holder shown in FIG.

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

In the laser processing apparatus of the embodiment (described later), a modified region is formed on the processing target along the planned cutting line by condensing the laser light on the processing target. Therefore, first, the formation of the modified region will be described with reference to FIGS. 1 to 6.

As shown in FIG. 1, the laser processing apparatus 100 includes a laser light source 101 that pulse-oscillates the laser beam L, and a dichroic mirror 103 arranged so as to change the direction of the optical axis (optical path) of the laser beam L by 90 °. A condensing lens 105 for condensing the laser beam L is provided. Further, the laser processing apparatus 100 includes a support base 107 for supporting the processing object 1 irradiated with the laser light L focused by the light collecting lens 105, and a stage 111 for moving the support base 107. The laser light source control unit 102 that controls the laser light source 101 to adjust the output of the laser light L, the pulse width, the pulse waveform, and the like, and the stage control unit 115 that controls the movement of the stage 111 are provided.

In the laser processing apparatus 100, the laser beam L emitted from the laser light source 101 is changed in the direction of its optical axis by 90 ° by the dichroic mirror 103, and is inside the processing object 1 placed on the support base 107. It is focused by the focusing lens 105. At the same time, the stage 111 is moved, and the workpiece 1 is moved relative to the laser beam L along the planned cutting line 5. As a result, a modified region along the planned cutting line 5 is formed on the workpiece 1. Although the stage 111 is moved here in order to move the laser beam L relatively, the condensing lens 105 may be moved, or both of them may be moved.

As the object to be processed 1, a plate-shaped member (for example, a substrate, a wafer, etc.) including a semiconductor substrate formed of a semiconductor material, a piezoelectric substrate formed of a piezoelectric material, or the like is used. As shown in FIG. 2, the machining target object 1 is set with a scheduled cutting line 5 for cutting the machining target object 1. The line 5 to be cut is a virtual line extending in a straight line. When a modified region is formed inside the object to be processed 1, as shown in FIG. 3, the laser beam L is cut with the condensing point (condensing position) P aligned inside the object to be processed 1. Move relative to the scheduled line 5 (ie, in the direction of arrow A in FIG. 2). As a result, as shown in FIGS. 4, 5 and 6, the modified region 7 is formed on the workpiece 1 along the scheduled cutting line 5, and the modified region formed along the scheduled cutting line 5. 7 is the cutting starting point region 8.

The condensing point P is a point where the laser beam L condenses. The line 5 to be cut may be not limited to a straight line but may be a curved line, a three-dimensional shape in which these are combined, or a coordinate-designated line 5. The line 5 to be cut is not limited to the virtual line, and may be a line actually drawn on the surface 3 of the object 1 to be processed. The modified region 7 may be formed continuously or intermittently. The modified region 7 may be in a row or a dot shape, and in short, the modified region 7 may be formed at least inside the object to be processed 1. In addition, cracks may be formed starting from the modified region 7, and the cracks and the modified region 7 may be exposed on the outer surface (front surface 3, back surface, or outer peripheral surface) of the object to be processed 1. .. The laser beam incident surface when forming the modified region 7 is not limited to the surface 3 of the object to be processed 1, and may be the back surface of the object to be processed 1.

By the way, when the modified region 7 is formed inside the processing target object 1, the laser beam L passes through the processing target object 1 and is near the focusing point P located inside the processing target object 1. Especially absorbed. As a result, the modified region 7 is formed on the workpiece 1 (that is, internal absorption type laser machining). In this case, since the laser beam L is hardly absorbed by the surface 3 of the object to be processed 1, the surface 3 of the object to be processed 1 is not melted. On the other hand, when the modified region 7 is formed on the surface 3 of the object to be processed 1, the laser beam L is particularly absorbed in the vicinity of the condensing point P located on the surface 3, and is melted and removed from the surface 3. , Holes, grooves, etc. are removed (surface absorption type laser machining).

The modified region 7 refers to a region in which the density, refractive index, mechanical strength, and other physical properties are different from those of the surroundings. The modified region 7 includes, for example, a melting treatment region (meaning at least one of a region once melted and then resolidified, a region in a molten state, and a region in a state of being resolidified from melting) and a crack region. , Dielectric breakdown region, refractive index change region, etc., and there is also a region where these are mixed. Further, the modified region 7 includes a region in which the density of the modified region 7 is changed in comparison with the density of the non-modified region in the material of the object to be processed 1, and a region in which lattice defects are formed. When the material of the object to be processed 1 is single crystal silicon, the modified region 7 can be said to be a high dislocation density region.

The melt-treated region, the refractive index change region, the region where the density of the modified region 7 is changed as compared with the density of the non-modified region, and the region where the lattice defects are formed are further inside those regions and modified. Cracks (cracks, microcracks) may be included at the interface between the region 7 and the non-modified region. The included cracks may extend over the entire surface of the modified region 7, or may be formed only in a part or in a plurality of parts. The object to be processed 1 includes a substrate made of a crystalline material having a crystal structure. For example, the object to be processed 1 includes a substrate formed of at least one of gallium nitride (GaN), silicon (Si), silicon carbide (SiC), LiTaO ₃ , and sapphire (Al ₂ O ₃ ). In other words, the object to be processed 1 includes, for example, a gallium nitride substrate, a silicon substrate, a SiC substrate, a LiTaO ₃ substrate, or a sapphire substrate. The crystal material may be either an anisotropic crystal or an isotropic crystal. Further, the object to be processed 1 may include a substrate made of a non-crystalline material having a non-crystalline structure (amorphous structure), and may include, for example, a glass substrate.

In the embodiment, the modified region 7 can be formed by forming a plurality of modified spots (processing marks) along the planned cutting line 5. In this case, the modified region 7 is formed by gathering a plurality of modified spots. The reforming spot is a reforming portion formed by a one-pulse shot of pulsed laser light (that is, one-pulse laser irradiation: laser shot). Examples of the modified spot include crack spots, melt-treated spots, refractive index change spots, and spots in which at least one of these is mixed. Regarding the modified spot, the size and the length of the crack to be generated are appropriately adjusted in consideration of the required cutting accuracy, the required flatness of the cut surface, the thickness, type, crystal orientation, etc. of the object 1 to be processed. Can be controlled. Further, in the embodiment, the modification spot can be formed as the modification region 7 along the planned cutting line 5.
[Laser Machining Device of the First Embodiment]

Next, the laser processing apparatus of the first embodiment will be described. In the following description, the directions orthogonal to each other in the horizontal plane are the X-axis direction and the Y-axis direction, and the vertical direction is the Z-axis direction.
[Overall configuration of laser processing equipment]

As shown in FIG. 7, the laser machining apparatus 200 includes an apparatus frame 210, a first moving mechanism 220, a support base (support portion) 230, and a second moving mechanism 240. Further, the laser processing apparatus 200 includes a laser output unit 300, a laser condensing unit 500, and a control unit 600.

The first moving mechanism 220 is attached to the device frame 210. The first moving mechanism 220 has a first rail unit 221 and a second rail unit 222, and a movable base 223. The first rail unit 221 is attached to the device frame 210. The first rail unit 221 is provided with a pair of rails 221a and 221b extending along the Y-axis direction. The second rail unit 222 is attached to a pair of rails 221a and 221b of the first rail unit 221 so as to be movable along the Y-axis direction. The second rail unit 222 is provided with a pair of rails 222a and 222b extending along the X-axis direction. The movable base 223 is attached to a pair of rails 222a and 222b of the second rail unit 222 so as to be movable along the X-axis direction. The movable base 223 can rotate about an axis parallel to the Z-axis direction as a center line.

The support base 230 is attached to the movable base 223. The support base 230 supports the object 1 to be processed. The object to be processed 1 has, for example, a plurality of functional elements (light receiving elements such as photodiodes, light emitting elements such as laser diodes, circuit elements formed as circuits, etc.) on the surface side of a substrate made of a semiconductor material such as silicon. It is formed in a matrix. When the object to be processed 1 is supported by the support base 230, for example, the surface 1a (a plurality of functional elements) of the object to be processed 1 is placed on the film 12 stretched on the annular frame 11 as shown in FIG. Side side) is attached. The support base 230 supports the object 1 to be processed by holding the frame 11 by a clamp and sucking the film 12 by a vacuum chuck table. On the support base 230, a plurality of scheduled cutting lines 5a parallel to each other and a plurality of scheduled cutting lines 5b parallel to each other are set in a grid pattern on the workpiece 1 so as to pass between adjacent functional elements. To.

As shown in FIG. 7, the support base 230 is moved along the Y-axis direction by the operation of the second rail unit 222 in the first moving mechanism 220. Further, the support base 230 is moved along the X-axis direction by the operation of the movable base 223 in the first moving mechanism 220. Further, the support base 230 is rotated about an axis parallel to the Z-axis direction as a center line by operating the movable base 223 in the first moving mechanism 220. In this way, the support base 230 is attached to the device frame 210 so as to be movable along the X-axis direction and the Y-axis direction and to be rotatable about an axis parallel to the Z-axis direction as a center line.

The laser output unit 300 is attached to the device frame 210. The laser condensing unit 500 is attached to the device frame 210 via the second moving mechanism 240. The laser condensing unit 500 is moved along the Z-axis direction by operating the second moving mechanism 240. In this way, the laser condensing unit 500 is attached to the device frame 210 so as to be movable along the Z-axis direction with respect to the laser output unit 300.

The control unit 600 is composed of a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The control unit 600 controls the operation of each unit of the laser processing apparatus 200.

As an example, in the laser machining apparatus 200, a modified region is formed inside the machining object 1 along the scheduled cutting lines 5a and 5b (see FIG. 8) as follows.

First, the machining object 1 is supported by the support base 230 so that the back surface 1b (see FIG. 8) of the machining object 1 becomes the laser beam incident surface, and each scheduled cutting line 5a of the machining object 1 is in the X-axis direction. Aligned in a direction parallel to. Subsequently, the laser condensing unit 240 is used by the second moving mechanism 240 so that the condensing point of the laser light L is located inside the processing object 1 at a position separated from the laser beam incident surface of the processing object 1 by a predetermined distance. 500 is moved. Subsequently, the focusing point of the laser light L moves relatively along each scheduled cutting line 5a while the distance between the incident surface of the laser light of the object 1 to be processed and the focusing point of the laser light L is kept constant. Be made to. As a result, a modified region is formed inside the workpiece 1 along each scheduled cutting line 5a.

When the formation of the modified region along each scheduled cutting line 5a is completed, the support base 230 is rotated by the first moving mechanism 220, and each scheduled cutting line 5b of the workpiece 1 is in a direction parallel to the X-axis direction. It is matched to. Subsequently, the laser condensing unit 240 is used by the second moving mechanism 240 so that the condensing point of the laser light L is located inside the processing object 1 at a position separated from the laser beam incident surface of the processing object 1 by a predetermined distance. 500 is moved. Subsequently, the focusing point of the laser light L moves relatively along each scheduled cutting line 5b while the distance between the incident surface of the laser light of the object 1 to be processed and the focusing point of the laser light L is kept constant. Be made to. As a result, a modified region is formed inside the workpiece 1 along each scheduled cutting line 5b.

As described above, in the laser processing apparatus 200, the direction parallel to the X-axis direction is the processing direction (scanning direction of the laser beam L). The relative movement of the focusing point of the laser beam L along each scheduled cutting line 5a and the relative movement of the focusing point of the laser beam L along each scheduled cutting line 5b are the first moving mechanisms. This is carried out by moving the support 230 along the X-axis direction by the 220. Further, the relative movement of the focusing point of the laser beam L between the scheduled cutting lines 5a and the relative movement of the focusing point of the laser beam L between the scheduled cutting lines 5b are performed by the first moving mechanism 220. This is carried out by moving the support base 230 along the Y-axis direction.

As shown in FIG. 9, the laser output unit 300 includes a mounting plate 301, a cover 302, and a plurality of mirrors 303 and 304. Further, the laser output unit 300 includes a laser oscillator 400, a shutter 320, a λ / 2 wave plate unit (output adjustment unit, polarization direction adjustment unit) 330, and a polarizing plate unit (output adjustment unit, polarization direction adjustment unit) 340. It has a beam expander (laser light parallelizing unit) 350 and a mirror unit 360.

The mounting plate 301 supports a plurality of mirrors 303, 304, a laser oscillator 400, a shutter 320, a λ / 2 wave plate unit 330, a polarizing plate unit 340, a beam expander 350, and a mirror unit 360. The plurality of mirrors 303, 304, the laser oscillator 400, the shutter 320, the λ / 2 wave plate unit 330, the polarizing plate unit 340, the beam expander 350, and the mirror unit 360 are mounted on the main surface 301a of the mounting plate 301. The mounting plate 301 is a plate-shaped member and can be attached to and detached from the device frame 210 (see FIG. 7). The laser output unit 300 is attached to the device frame 210 via the attachment plate 301. That is, the laser output unit 300 is removable from the device frame 210.

The cover 302 has a plurality of mirrors 303, 304, a laser oscillator 400, a shutter 320, a λ / 2 wave plate unit 330, a polarizing plate unit 340, a beam expander 350, and a mirror unit 360 on the main surface 301a of the mounting plate 301. Covering. The cover 302 is removable from the mounting plate 301.

The laser oscillator 400 pulse-oscillates a linearly polarized laser beam L along the X-axis direction. As will be described later, the laser oscillator 400 is configured as a MOPA (Master Oscillator Power Amplifier) type fiber laser. Therefore, in the laser oscillator 400, the output of the laser beam L can be switched on and off at high speed by switching the output of the seed light LD (Laser Diode / semiconductor laser) and the excitation LD on and off. The wavelength of the laser beam L emitted from the laser oscillator 400 is included in, for example, any wavelength band of 500 to 550 nm, 1000 to 1150 nm, or 1300 to 1400 nm. The laser beam L in the wavelength band of 500 to 550 nm is suitable for internal absorption type laser machining on a substrate made of sapphire, for example. The laser beam L in each wavelength band of 1000 to 1150 nm and 1300 to 1400 nm is suitable for internal absorption type laser machining on a substrate made of silicon, for example. The polarization direction of the laser beam L emitted from the laser oscillator 400 is, for example, a direction parallel to the Y-axis direction. The laser beam L emitted from the laser oscillator 400 is reflected by the mirror 303 and is incident on the shutter 320 along the Y-axis direction.

The shutter 320 opens and closes the optical path of the laser beam L by a mechanical mechanism. As described above, the switching of ON / OFF of the output of the laser beam L from the laser output unit 300 is performed by switching ON / OFF of the output of the laser beam L in the laser oscillator 400, but the shutter 320 is provided. By doing so, for example, it is possible to prevent the laser beam L from being unexpectedly emitted from the laser output unit 300. The laser beam L that has passed through the shutter 320 is reflected by the mirror 304 and sequentially enters the λ / 2 wave plate unit 330 and the polarizing plate unit 340 along the X-axis direction.

The λ / 2 wave plate unit 330 and the polarizing plate unit 340 function as output adjusting units for adjusting the output (light intensity) of the laser beam L. Further, the λ / 2 wave plate unit 330 and the polarizing plate unit 340 function as polarization direction adjusting units for adjusting the polarization direction of the laser beam L. Details of these will be described later. The laser beam L that has sequentially passed through the λ / 2 wave plate unit 330 and the polarizing plate unit 340 is incident on the beam expander 350 along the X-axis direction.

The beam expander 350 parallelizes the laser beam L while adjusting the diameter of the laser beam L. The laser beam L that has passed through the beam expander 350 is incident on the mirror unit 360 along the X-axis direction.

The mirror unit 360 has a support base 361 and a plurality of mirrors 362 and 363. The support base 361 supports a plurality of mirrors 362 and 363. The support base 361 is attached to the mounting plate 301 so that its position can be adjusted along the X-axis direction and the Y-axis direction. The mirror 362 reflects the laser beam L that has passed through the beam expander 350 in the Y-axis direction. The mirror 362 is attached to the support base 361 so that its reflective surface can be angle-adjusted, for example, around an axis parallel to the Z axis. The mirror 363 reflects the laser beam L reflected by the mirror 362 in the Z-axis direction. The mirror 363 is attached to the support base 361 so that the reflecting surface thereof can be adjusted in angle around an axis parallel to the X axis and can be adjusted in position along the Y axis direction, for example. The laser beam L reflected by the mirror 363 passes through the opening 361a formed in the support base 361 and is incident on the laser condensing unit 500 (see FIG. 7) along the Z-axis direction. That is, the emission direction of the laser beam L by the laser output unit 300 coincides with the moving direction of the laser condensing unit 500.

As described above, each of the mirrors 362 and 363 has a mechanism for adjusting the angle of the reflecting surface. In the mirror unit 360, the position of the support base 361 with respect to the mounting plate 301 is adjusted, the position of the mirror 363 with respect to the support base 361 is adjusted, and the angle of the reflecting surface of each mirror 362, 363 is adjusted, so that the laser output unit 300 can adjust the position. The position and angle of the optical axis of the emitted laser light L are adjusted with respect to the laser condensing unit 500. That is, the plurality of mirrors 362 and 363 are configured to adjust the optical axis of the laser beam L emitted from the laser output unit 300.

The laser condensing unit 500 condenses the laser beam L that has passed through the mirror unit 360 onto the object 1 to be processed. As shown in FIG. 10, the laser condensing unit 500 has a housing 501. A second moving mechanism 240 is attached to the side surface of the housing 501. The housing 501 is provided with a cylindrical light incident portion 501a so as to face the opening 361a of the mirror unit 360 in the Z-axis direction. The light incident unit 501a causes the laser light L emitted from the laser output unit 300 to enter the housing 501. When the laser condensing unit 500 is moved along the Z-axis direction by the second moving mechanism 240 (that is, the laser condensing unit 500 is moved with respect to the mirror unit 360), the mirror unit 360 and the light incident unit 501a are They are separated from each other by a distance that does not come into contact with each other (when moved).

Although not shown, a mirror, a reflective spatial light modulator, and a 4f lens unit are arranged in the housing 501. Further, a condenser lens unit (condensing optical system), a drive mechanism, and a pair of ranging sensors are attached to the housing 501.

The laser beam L traveling in the housing 501 along the Z-axis direction is reflected by the mirror in a direction parallel to the XY plane and incident on the reflective spatial light modulator. The reflective spatial light modulator reflects the laser light L along the XY plane while modulating the laser light L reflected by the mirror. The reflective spatial light modulator is, for example, a spatial light modulator (SLM: Spatial Light Modulator) of a reflective liquid crystal (LCOS: Liquid Crystal on Silicon).

Here, in a plane parallel to the XY plane, the optical axis of the laser light L incident on the reflective spatial light modulator and the optical axis of the laser light L emitted from the reflective spatial light modulator are sharp angles. Make a certain angle α. This is because the incident angle and the reflection angle of the laser beam L are suppressed to suppress the decrease in the diffraction efficiency, and the performance of the reflection type spatial light modulator is fully exhibited. Further, in the reflective spatial light modulator, the laser beam L is reflected as P-polarized light. This is because when a liquid crystal is used for the optical modulation layer of the reflective spatial light modulator, it is in a plane parallel to the plane including the optical axis of the laser beam L entering and exiting the reflective spatial light modulator. This is because when the liquid crystal is oriented so that the liquid crystal molecules are tilted, the laser light L is subjected to phase modulation while the rotation of the polarization plane is suppressed (see, for example, Japanese Patent Application Laid-Open No. 387875). ..

The 4f lens unit constitutes a bilateral telecentric optical system in which the reflective surface of the reflective spatial light modulator and the entrance pupil surface of the condenser lens unit are in an imaging relationship. As a result, the image of the laser beam L on the reflecting surface of the reflective spatial light modulator (the image of the laser beam L modulated in the reflective spatial light modulator) is transferred to the incident pupil surface of the condenser lens unit ( Image).

The condenser lens unit is attached to the housing 501 via a drive mechanism. The condensing lens unit condenses the laser beam L on the processing object 1 (see FIG. 7) supported by the support base 230. The drive mechanism moves the condenser lens unit along the Z-axis direction by the drive force of the piezoelectric element.

The pair of ranging sensors are attached to the housing 501 so as to be located on both sides of the condenser lens unit in the X-axis direction. Each distance measuring sensor emits distance measuring light (for example, laser light) to the laser light incident surface of the workpiece 1 (see FIG. 7) supported by the support base 230, and the laser light incident surface. By detecting the distance-finding light reflected by the object 1, the displacement data of the laser beam incident surface of the workpiece 1 is acquired.

In the laser processing apparatus 200, as described above, the direction parallel to the X-axis direction is the processing direction (scanning direction of the laser beam L). Therefore, when the focusing point of the laser beam L is relatively moved along the lines 5a and 5b to be cut, the distance measuring sensor that precedes the focusing lens unit of the pair of distance measuring sensors is relatively advanced. The sensor acquires displacement data of the laser beam incident surface of the workpiece 1 along the lines 5a and 5b to be cut. Then, the drive mechanism is based on the displacement data acquired by the ranging sensor so that the distance between the laser beam incident surface of the object 1 to be processed and the focusing point of the laser beam L is kept constant. Move the unit along the Z-axis direction.
[Λ / 2 wave plate unit and polarizing plate unit]

As described above, in the laser condensing unit 500, the optical axis of the laser light L incident on the reflective spatial light modulator and the laser light emitted from the reflective spatial light modulator in a plane parallel to the XY plane. The optical axis of L forms an angle α which is a sharp angle. On the other hand, as shown in FIG. 9, in the laser output unit 300, the optical path of the laser beam L is set to be along the X-axis direction or the Y-axis direction. Therefore, in the laser output unit 300, the λ / 2 wave plate unit 330 and the polarizing plate unit 340 are not only used as an output adjusting unit for adjusting the output of the laser light L, but also in the polarization direction for adjusting the polarization direction of the laser light L. It is also necessary to function as an adjustment unit.

As shown in FIG. 11, the λ / 2 wave plate unit 330 has a holder 331 and a λ / 2 wave plate 332. The holder 331 holds the λ / 2 wave plate 332 so that the λ / 2 wave plate 332 can rotate around the axis (first axis) XL parallel to the X-axis direction as the center line. The λ / 2 wave plate 332 rotates the polarization direction by an angle of 2θ with the axis XL as the center line when the laser beam L is incident with the polarization direction tilted by an angle θ with respect to the optical axis (for example, the fast axis). The laser beam L is emitted (see (a) in FIG. 12).

The polarizing plate unit 340 has a holder 341, a polarizing plate (polarizing member) 342, and an optical path correction plate (optical path correction member) 343. The holder 341 holds the polarizing plate 342 and the optical path correction plate 343 so that the polarizing plate 342 and the optical path correction plate 343 can rotate integrally with the axis (second axis) XL as the center line. The light incident surface and the light emitting surface of the polarizing plate 342 are tilted by a predetermined angle (for example, a brewer angle). When the laser beam L is incident, the polarizing plate 342 transmits the P polarization component of the laser beam L corresponding to the polarization axis of the polarizing plate 342, and reflects or absorbs the S polarization component of the laser beam L (FIG. 12). See (b)). The light incident surface and the light emitting surface of the optical path correction plate 343 are inclined to the opposite sides of the light incident surface and the light emitting surface of the polarizing plate 342. The optical path correction plate 343 returns the optical axis of the laser beam L deviated from the axis XL by passing through the polarizing plate 342 to the axis XL.

In the polarizing plate unit 340, the polarizing plate 342 and the optical path correction plate 343 are integrally rotated with the axis XL as the center line, and as shown in FIG. 12B, polarization is performed in a direction parallel to the Y-axis direction. The polarizing axis of the plate 342 is tilted by an angle α. As a result, the polarization direction of the laser beam L emitted from the polarizing plate unit 340 is tilted by an angle α with respect to the direction parallel to the Y-axis direction. As a result, the laser beam L is reflected as P-polarized light in the reflective spatial light modulator of the laser condensing unit 500.

Further, as shown in FIG. 12B, the polarization direction of the laser beam L incident on the polarizing plate unit 340 is adjusted, and the light intensity of the laser beam L emitted from the polarizing plate unit 340 is adjusted. The polarization direction of the laser beam L incident on the polarizing plate unit 340 is adjusted by rotating the λ / 2 wave plate 332 with the axis XL as the center line in the λ / 2 wave plate unit 330, as shown in FIG. 12 (a). By adjusting the angle of the optical axis of the λ / 2 wave plate 332 with respect to the polarization direction (for example, the direction parallel to the Y-axis direction) of the laser beam L incident on the λ / 2 wave plate 332. Will be done.

As described above, in the laser output unit 300, the λ / 2 wave plate unit 330 and the polarizing plate unit 340 are not only used as an output adjusting unit (in the above example, an output damping unit) for adjusting the output of the laser beam L. It also functions as a polarization direction adjusting unit for adjusting the polarization direction of the laser beam L.
[Laser Oscillator of First Embodiment]

As shown in FIG. 13, the laser oscillator 400 includes a seed light emitting unit 410, a preamplifier unit (amplifier unit) 420, a power amplifier unit (amplifier unit) 430, and a laser light emitting unit 440. .. The laser oscillator 400 is configured as a MOPA type fiber laser.

The seed light emitting unit 410 has a seed light LD (seed light source) 411. The seed light LD411 is driven by a pulse generator and pulse-oscillates the laser light L, which is the seed light. The laser beam L emitted from the seed light LD411 is propagated to the preamplifier section 420 by the fiber F1 and the fiber cable FC1. The laser beam L has a predetermined wavelength (for example, 1098 nm).

The preamplifier unit 420 includes an isolator 421, a clad mode stripper 422, a first laser fiber (first optical fiber) 423, for example, one first excitation LD (excitation light source) 424, and a combiner 425. There is. In the preamplifier unit 420, the laser beam L is propagated to the first laser fiber 423 by the fibers F3, F4, F5, amplified by the first laser fiber 423, and then by the fiber (second optical fiber) F6 and the fiber F7. It is propagated to the power amplifier unit 430.

The first excitation LD424 emits the first excitation light PL1 having a predetermined wavelength (for example, 915 nm) for exciting the first laser fiber 423. The first excitation light PL1 emitted from the first excitation LD424 is propagated to the combiner 425 by the fiber F21. The combiner 425 couples the first excitation light PL1 to the fiber F6 between the fiber F6 and the fiber F7. The first excitation light PL1 coupled to the fiber F6 is incident on the first laser fiber 423 and travels in the first laser fiber 423 in the direction opposite to the traveling direction of the laser light L. That is, the fiber F6 is optically connected (coupled) to the first laser fiber 423 and propagates the laser light L and the first excitation light PL1. As described above, the preamplifier unit 420 adopts a rear excitation configuration.

The first laser fiber 423 amplifies the laser light L by propagating the laser light L emitted from the seed light emitting unit 410 in a state of being excited by the first excitation light PL1. That is, the first laser fiber 423 amplifies the laser light L emitted from the seed light emitting unit 410 while propagating it. The isolator 421 blocks the return light (light traveling toward the seed light emitting unit 410 side) between the fiber F3 and the fiber F4. The clad mode stripper 422 removes the first excitation light PL1 that was not absorbed by the first laser fiber 423 between the fiber F5 and the first laser fiber 423.

The power amplifier unit 430 includes an isolator 431, a bandpass filter 432, a clad mode stripper 433, a second laser fiber (first optical fiber) 434, and, for example, a plurality of (six in this case) second excitation LDs (excitations). It has a light source) 435 and a combiner 436. In the power amplifier unit 430, the laser beam L is propagated to the second laser fiber 434 by the fibers F8, F9, and F10, amplified by the second laser fiber 434, and then the fiber (second optical fiber) F11 and. It is propagated to the laser beam emitting unit 440 by the fibers F12 and F13.

Each second excitation LD435 emits a second excitation light PL2 having a predetermined wavelength (for example, 915 nm) for exciting the second laser fiber 434. The second excitation light PL2 emitted from each second excitation LD435 is propagated to the combiner 436 by the fiber F22. The combiner 436 couples the second excitation light PL2 to the fiber F11 between the fiber F11 and the fiber F12. The second excitation light PL2 coupled to the fiber F11 is incident on the second laser fiber 434 and travels in the second laser fiber 434 in the direction opposite to the traveling direction of the laser light L. That is, the fiber F11 is optically connected (coupled) to the second laser fiber 434 and propagates the laser light L and the second excitation light PL2. As described above, the power amplifier unit 430 adopts a rear excitation configuration.

The second laser fiber 434 amplifies the laser light L by propagating the laser light L amplified by the preamplifier unit 420 in a state of being excited by the second excitation light PL2. That is, the second laser fiber 434 amplifies the laser light L emitted from the seed light emitting unit 410 while propagating it. The isolator 431 blocks the return light (light traveling toward the preamplifier unit 420 side) between the fiber F7 and the fiber F8. The bandpass filter 432 removes ASE (Amplified Spontaneous Emission) light generated in the preamplifier unit 420. The clad mode stripper 433 removes the second excitation light PL2 that was not absorbed by the second laser fiber 434 between the fiber F10 and the second laser fiber 434.

The laser light emitting unit 440 has a collimator 441 and an isolator (optical component) 442. The collimator 441 parallelizes the laser beam L emitted from the exit end of the fiber F13. The isolator 442 blocks the return light (light traveling in the laser oscillator 400). The emission end of the isolator 442 constitutes an emission end 443 that emits the laser beam L amplified by the power amplifier unit 430 to the outside.

In the laser oscillator 400, the output of the laser light L emitted from the seed light emitting unit 410, the output of the laser light L amplified by the preamplifier unit 420, the output of the laser light L amplified by the power amplifier unit 430, and the power amplifier The output of the return light in unit 430 is monitored. Further, the output of the first excitation light PL1 emitted from the first excitation LD424 and the output of the second excitation light PL2 emitted from the plurality of second excitation LD435s are monitored.

A part of the laser beam L emitted from the seed light emitting unit 410 enters the fiber F31 via the coupler 451 provided between the fiber F4 and the fiber F5, and the fiber F31 causes the PD (light receiving element) 452. It is propagated and detected by PD452. The output of the laser beam L emitted from the seed light emitting unit 410 is monitored based on the signal output from the PD 452.

A part of the laser beam L amplified by the preamplifier unit 420 enters the fiber F32 via the coupler 454 provided between the fiber F9 and the fiber F10, and propagates to the PD (light receiving element) 455 by the fiber F32. It is detected by PD455. The output of the laser beam L amplified by the preamplifier unit 420 is monitored based on the signal output from the PD455.

A part of the laser beam L amplified by the power amplifier unit 430 enters the fiber F34 via the coupler 458 provided between the fiber F12 and the fiber F13, and propagates to the PD (light receiving element) 459 by the fiber F34. It is made to be detected by PD459. The output of the laser beam L amplified by the power amplifier unit 430 is monitored based on the signal output from the PD459.

When return light (light traveling toward the bandpass filter 432 side) is generated in the second laser fiber 434 of the power amplifier unit 430, a part of the return light is incident on the fiber F33 via the coupler 454 and enters the fiber F33. It is propagated to PD456 and detected by PD456. The output of the return light in the power amplifier unit 430 is monitored based on the signal output from the PD456.

A part of the first excitation light PL1 emitted from the first excitation LD424 is incident on the PD (photodetection element) 453 arranged at the junction between the fiber F6 and the first laser fiber 423 and detected by the PD453. .. The output of the first excitation light PL1 emitted from the first excitation LD424 is monitored based on the signal output from the PD453.

A part of the second excitation light PL2 emitted from the plurality of second excitation LD435s is incident on the PD 457 arranged at the junction between the fiber F11 and the second laser fiber 434 and detected by the PD (photodetection element) 457. Will be done. The output of the second excitation light PL2 emitted from the plurality of second excitation LD435s is monitored based on the signal output from the PD457.

As shown in FIG. 14, the laser oscillator 400 includes a first support plate 461, a second support plate 462, and a housing 470. The housing 470 is provided with a mounting base 471. The housing 470 has a first portion 470a and a second portion 470b. The second portion 470b is removable from the first portion 470a. As an example, the first portion 470a has a rectangular parallelepiped shape, and the mounting base 471 is composed of a lower wall of the first portion 470a. The second portion 470b has a rectangular parallelepiped shape and is attached to the upper surface of the first portion 470a.

The first portion 470a accommodates a preamplifier unit 420, a power amplifier unit 430, and a laser light emitting unit 440. The second portion 470b accommodates the seed light emitting unit 410. The fiber cable FC1 that propagates the laser beam L from the seed light emitting unit 410 to the preamplifier unit 420 is laid between the first portion 470a and the second portion 470b (see FIG. 9).

The first support plate 461 and the second support plate 462 are housed in the first portion 470a so that they face each other (that is, the thickness directions of the first support plate 461 and the second support plate 462 are relative to each other. The first support plate 461 and the second support plate 462 are arranged so as to coincide with each other and to overlap each other when viewed from the thickness direction. The second support plate 462 is arranged above the mounting base 471. The first support plate 461 is arranged above the second support plate 462. More specifically, the front surface 471a of the mounting base 471 and the back surface 462b of the second support plate 462 face each other with a space, and the front surface 462a of the second support plate 462 and the back surface 461b of the first support plate 461 b. Are facing each other through space. The first support plate 461 and the second support plate 462 are each supported by columns (not shown) or the like.

In the laser oscillator 400, the back surface 471b of the mounting base 471 is in contact with the main surface 301a of the mounting plate 301, and the emission end 443 of the laser beam emitting portion 440 is facing the mirror 303, and the laser oscillator 400 is connected to the mounting plate 301 via the mounting base 471. It is attached to (see FIG. 9). That is, the laser oscillator 400 is removable from the mounting plate 301 (and thus the device frame 210).

As shown in FIG. 15 (see FIG. 13), the surface 461a of the first support plate 461 has a fiber connector 401, an isolator 421, a coupler 451 and a clad mode stripper 422, a first laser fiber 423, a PD453, and a combiner 425. An isolator 431, a bandpass filter 432 and a coupler 454 are attached. The fiber connector 401 connects the fiber cable FC1 and the fiber F3 to each other. The first laser fiber 423 is held by a fiber reel (not shown). The fiber F10 that propagates the laser beam L to the second laser fiber 434 passes from the surface 461a of the first support plate 461 to the surface 462a of the second support plate 462 via the notch 461c formed in the first support plate 461. It is postponed.

As shown in FIGS. 16 and 17, the front surface 462a, the back surface 462b, and the side surface 462c of the second support plate 462 include the second laser fiber 434 of the power amplifier unit 430, the plurality of second excitation LD435s, and the preamplifier unit 420. It is an arrangement surface of the 1st excitation LD424 and the like. It should be noted that FIG. 17 is a view of the configuration of the back surface 462b side of the second support plate 462 as viewed from the surface 462a side of the second support plate 462, and in FIG. 17, the configuration of the surface 462a side of the second support plate 462 is It has been omitted.

As shown in FIG. 16 (see FIG. 13), a clad mode stripper 433, a second laser fiber 434, PD457, a combiner 436, a coupler 458 and a PD459 are attached to the surface 462a of the second support plate 462. The second laser fiber 434 is held by a fiber reel (not shown). The fiber F13 that propagates the laser beam L to the laser beam emitting portion 440 extends from the surface 462a of the second support plate 462 to the surface 471a of the mounting base 471 via the notch 462e formed in the second support plate 462. doing.

PD452,455,456 and the first excited LD424 are attached to the side surface 462c of the second support plate 462. The fiber F31 that propagates a part of the laser beam L to the PD452, the fiber F32 that propagates a part of the laser beam L to the PD455, and the fiber F33 that propagates the return light to the PD456 are the first support plate 461 and the housing 470. It extends from the surface 461a of the first support plate 461 to the side surface 462c of the second support plate 462 through a gap formed between the inner surface of the first portion 470a. The fiber F21 for propagating the first excitation light PL1 to the combiner 425 passes the side surface 462c of the second support plate 462 through a gap formed between the first support plate 461 and the inner surface of the first portion 470a of the housing 470. Extends from to the surface 461a of the first support plate 461.

As shown in FIG. 17, a plurality of second excited LD435s are attached to the back surface 462b of the second support plate 462. The fiber F22 for propagating the second excitation light PL2 to the combiner 436 extends from the back surface 462b of the second support plate 462 to the surface 462a of the second support plate 462 via the notch 462d formed in the second support plate 462. Exists.

As shown in FIGS. 16 and 17, a pipe 462f is embedded in the second support plate 462. Cooling water (refrigerant) W is circulated and supplied to the pipe 462f. As a result, the second support plate 462 functions as a cooling plate provided with a flow path for the cooling water W. In the laser oscillator 400, the first laser fiber 423 of the preamplifier unit 420 is arranged on the first support plate 461, while the second laser fiber 434 of the power amplifier unit 430, the plurality of second excited LD435s, and the preamplifier unit The first excited LD424 of 420 is arranged on the second support plate 462. As a result, the second laser fiber 434 of the power amplifier unit 430, the plurality of second excited LD435s, and the first excited LD424 of the preamplifier unit 420 are cooled.

As shown in FIG. 18, a support member 402, a collimator 441, and an isolator 442 are attached to the surface 471a of the attachment base 471. That is, the laser light emitting unit 440 is arranged on the mounting base 471. As shown in FIG. 19, a recess 471c is formed on the back surface 471b of the mounting base 471. On the inner surface of the recess 471c, processing boards 403 and 404 for signals output from PD452,455,456,457,459 and a memory board 405 are attached. Note that FIG. 19 is a view of the configuration on the back surface 471b side of the mounting base 471 as viewed from the front surface 471a side of the mounting base 471, and in FIG. 19, the configuration on the front surface 471a side of the mounting base 471 is omitted.

As shown in FIG. 20, the support member 402 has a support surface 402a. On the support surface 402a, a fiber F13 that propagates the laser light L from the power amplifier unit 430 to the laser light emitting unit 440 is arranged. More specifically, the support surface 402a extends from directly below the notch 462e formed in the second support plate 462 (see FIGS. 16 and 18) toward the incident end of the collimator 441, and the collimator 441 extends. It is inclined so that it is located on the lower side as it gets closer to.

Subsequently, the excitation light detection structure will be described. As shown in FIG. 13, the laser oscillator 400 is formed with a number (here, two) of excitation light detection structures 700, 701 corresponding to the number of laser fibers. The excitation light detection structure 700 detects the first excitation light PL1 emitted from the first excitation LD424. The excitation light detection structure 701 detects the second excitation light PL2 emitted from the second excitation LD435.

As shown in FIG. 15, the excitation light detection structure 700 includes a first laser fiber 423, a fiber F6, a PD453, and a holder 464 holding the PD453, on the surface 461a of the first support plate 461. It is configured. As shown in FIG. 16, the excitation light detection structure 701 includes a second laser fiber 434, a fiber F11, a PD 457, and a holder 469 holding the PD 457, on the surface 462a of the second support plate 462. It is configured. Hereinafter, the excitation light detection structure 700 will be specifically described, but the excitation light detection structure 701 also has the same configuration.

FIG. 21 is a bottom view of the excitation light detection structure shown in FIG. FIG. 22 is a schematic enlarged cross-sectional view of the excitation light detection structure shown in FIG. In FIG. 22, hatching is omitted. As shown in FIGS. 21 and 22, the excitation light detection structure 700 includes a first laser fiber 423, a fiber F6, a PD453, and a holder 464 holding the PD453. The first laser fiber 423 and the fiber F6 are double clad fibers (DCF).

That is, the first laser fiber 423 includes a core 720, a first clad 721 provided around the core 720, a second clad 722 provided around the core 720 and the first clad 721, and a core 720, a first clad. The 1-clad 721 and the outer cover 723 provided around the 2nd clad 722 are included. Further, the fiber F6 includes a core 760, a first clad 761 provided around the core 760, a second clad 762 provided around the core 760 and the first clad 761, and a core 760 and a first clad 761. And the outer cover 763 provided around the second clad 762.

The refractive index of the cores 720 and 760 is, for example, about 1.455. The refractive index of the first clad 721,761 is lower than the refractive index of the cores 720 and 760, for example, about 1.452. The refractive index of the second clad 722,762 is lower than the refractive index of the first clad 721,761, for example, about 1.365 to 1.375. The first clad 721,761 confine the laser beam L in the cores 720 and 760. Therefore, the laser beam L propagates in the cores 720 and 760. The second clad 722,762 confine the first excitation light PL1 in the first clad 721,761. Therefore, the first excitation light PL1 propagates in the first clad 721,761 and the cores 720,760.

The first laser fiber 423 and the fiber F6 are fused and connected to each other. Therefore, the laser beam L propagating through the core 720 of the first laser fiber 423 is incident on the core 760 of the fiber F6 and propagates through the core 760. Further, the first excitation light PL1 propagating through the core 760 and the first clad 761 of the fiber F6 is incident on the core 720 and the first clad 721 of the first laser fiber 423 and propagates through the core 720 and the first clad 721.

The first clad 761 of the fiber F6 includes a covering portion 764 that covers the core 760 and is covered with the second clad 762 and the outer cover 763. Further, the first clad 761 covers the core 760 and includes an exposed portion 765 exposed from the second clad 762 and the outer cover 763. The exposed portion 765 includes a fusion portion M with the first laser fiber 423. That is, the exposed portion 765 is an end portion of the fiber F6 on the first laser fiber 423 side. On the other hand, the covering portion 764 is a portion extending from the exposed portion 765 of the fiber F6 to the side opposite to the fused portion M.

The first clad 721 of the first laser fiber 423 includes a covering portion 724 that covers the core 720 and is covered with the second clad 722 and the outer cover 723. Further, the first clad 721 covers the core 720 and includes an exposed portion 725 exposed from the second clad 722 and the outer cover 723. The exposed portion 725 is an end portion of the first laser fiber 423 on the fiber F6 side. On the other hand, the covering portion 724 is a portion of the first laser fiber 423 extending from the exposed portion 725 to the opposite side of the fiber F6. The first laser fiber 423 and the fiber F6 are connected to each other at the exposed portions 725 and 765 thereof.

The exposed portions 725,765 are formed by removing the second clad 722,762 and the outer cover 723,763, as will be described later. Therefore, at the boundary between the exposed portion 725 and the covering portion 724, uneven (uneven and rough) end faces of the second clad 722 and the outer cover 723 are formed. Further, at the boundary between the exposed portion 765 and the covering portion 764, uneven (uneven and rough) end faces of the second clad 762 and the outer cover 763 are formed.

Here, the first laser fiber 423 and the fiber F6 are provided with a capillary 730 so as to collectively cover the exposed portions 725 and 765. The capillary 730 is provided so as to extend from the exposed portion 725,765 to the covering portion 724,764. A resin layer 740 is filled at least between the exposed portions 725 and 765 and the capillary 730. The refractive index of the resin layer 740 is smaller than the refractive index of the first clad 721,761, for example, about 1.37. The capillary 730 is made of glass, for example, and has a refractive index higher than that of the resin layer 740. The refractive index of the capillary 730 is, for example, about 1.438 to 1.455.

The resin layer 740 is in close contact with the first clad 721 in the exposed portion 725 of the first laser fiber 423 and the first clad 741 covering the first clad 721, and in close contact with the first clad 761 in the exposed portion 765 of the fiber F6. Includes a second portion 742 that covers the first clad 761. In other words, the first laser fiber 423 includes a resin layer 740 (first portion 741) provided around the core 720 and the first clad 721. Further, the fiber F6 includes a resin layer 740 (second portion 742) provided around the core 760 and the first clad 761.

The capillary 730 includes a first portion 731 provided around the first portion 741 of the resin layer 740 and a second portion 732 provided around the second portion 742 of the resin layer 740. In other words, the first laser fiber 423 includes a capillary 730 (first portion 731) that adheres to the resin layer 740 in the exposed portion 725 and further covers the resin layer 740. Further, the fiber F6 includes a capillary (second portion 732) which is in close contact with the resin layer 740 in the exposed portion 765 and further covers the resin layer 740.

The PD453 is arranged so that its light receiving side faces the exposed portion 765 of the fiber F6 via the capillary 730 and the resin layer 740, and is held by the holder 464. FIG. 23 is an exploded perspective view of the holder shown in FIG. FIG. 24 is a perspective view of the holder shown in FIG. The holder 464 includes a main body portion 465 for holding the PD453 and a pair of fixing portions 466 for fixing the main body portion 465 to the surface 461a of the first support plate 461. The main body 465 has a rectangular parallelepiped shape. A through hole 465h for accommodating the PD453 is formed at substantially the center of the main body 465.

The through hole 465h communicates the upper surface 464a and the back surface 464b of the holder 464. The through hole 465h has an annular stepped portion 465c between the upper surface 464a and the back surface 464b. The PD453 is held by the main body portion 465 by being in contact with the step portion 465c and being pressed by the pressing plate 467 from the upper surface 464a side in a state of being accommodated in the through hole 465h. The holding plate 467 is fixed to the upper surface 464a by, for example, a bolt B or the like in a state where the terminal of the PD453 is exposed from the hole 467h.

The fixed portion 466 has a rectangular parallelepiped shape. The fixing portions 466 are provided integrally with the main body portion 465 at both ends of the main body portion 465 in the longitudinal direction. The holder 464 is fixed to the front surface 461a by bolts B or the like inserted through these fixing portions 466 in a state where the back surface 464b is directed to the front surface 461a side of the first support plate 461.

A groove 468 is formed on the back surface 464b of the holder 464. The groove 468 is formed in a straight line over both end faces 464s in the longitudinal direction of the holder 464 so as to pass through the through hole 465h accommodating the PD453. The groove 468 positions the first laser fiber 423 and the fiber F6. More specifically, the first laser fiber 423 and the fiber F6 are positioned by the inner wall of the groove 468 by being housed in the groove 468 in a state of being arranged on the surface 461a of the first support plate 461. .. In particular, since the groove 468 extends so as to pass through the through hole 465h, the fiber F6 is accommodated in the groove 468, so that the exposed portion 765 is positioned so as to face the PD453.

The operation and effect of the laser oscillator 400 will be described with reference to FIG. 22 again. In the laser oscillator 400 (excitation light detection structure 700), the first laser fiber 423 is excited by the excitation light propagated by the fiber F6. As a result, the laser light (seed light) L from the seed light LD411 is amplified while being propagated through the first laser fiber 423. On the other hand, the fiber F6 includes an exposed portion 765 in which the first clad 761 covering the core 760 is exposed from the second clad 762. The exposed portion 765 is covered with a resin layer 740 having a refractive index lower than that of the first clad 761.

Then, PD453 is arranged so as to face the exposed portion 765 of the first clad 761 via the resin layer 740. Therefore, the leakage light PL0 of the first excitation light PL1 propagating through the first clad 761 and emitted from the exposed portion 765 can be detected by the PD453. It is considered that one of the causes of the leakage light PL0 is that the first excitation light PL1 is scattered by the end of the second clad 762 at the boundary between the exposed portion 765 and the covering portion 764.

Further, in the laser oscillator 400 (excitation light detection structure 700), the exposed portion 765 of the fiber F6 includes a fusion portion M with the first laser fiber 423. Therefore, it becomes easy to expose the first clad 761 from the second clad 762 to form the exposed portion 765, or to cover the exposed portion 765 with the resin layer 740. That is, the first excitation light PL1 can be easily detected by using the fused portion M.

Further, in the laser oscillator 400 (excitation light detection structure 700), the fiber F6 has a refractive index higher than that of the resin layer 740, and includes a capillary 730 that further covers the resin layer 740 in the exposed portion 765. .. In this case, the first excitation light PL1 can be easily leaked from the resin layer 740.

Further, the laser oscillator 400 (excitation light detection structure 700) includes a holder for holding the PD453, and the fiber F6 is positioned by the holder 464 so that the exposed portion 765 faces the PD453. Therefore, the relative positional relationship between the exposed portion 765 of the fiber F6 and the PD453 can be reliably maintained.

An example of the manufacturing method of the excitation light detection structure 700 as described above will be described. First, a laser fiber serving as the first laser fiber 423 (hereinafter referred to as the first laser fiber 423) and an optical fiber serving as the fiber F6 (hereinafter referred to as the fiber F6) are prepared. Subsequently, in the first laser fiber 423, the first clad 721 is exposed by removing the second clad 722 and the outer cover 723, and the exposed portion 725 is formed. Further, in the fiber F6, the first clad 761 is exposed by removing the second clad 762 and the outer cover 763, and the exposed portion 765 is formed (first step).

Subsequently, the first laser fiber 423 is cut at a part on the tip end side of the exposed portion 725 to form a cut surface orthogonal to the optical axis. Further, by cutting the fiber F6 at a part on the tip end side of the exposed portion 765, a cut surface orthogonal to the optical axis is formed (second step).

Subsequently, on those cut surfaces, the exposed portion 765 of the fiber F6 is fused to the exposed portion 725 of the first laser fiber 423, whereby the fiber F6 is fused and connected to the first laser fiber 423 to be fused and connected to the fused portion M. (Third step). At this time, before the fiber F6 and the first laser fiber 423 are fused and connected, the capillary 730 is inserted into either the fiber F6 or the first laser fiber 423 in advance.

Subsequently, a resin layer 740 having a refractive index lower than that of the first clad 761 of the fiber F6 is formed on the first clad 761 so as to cover the exposed portion 765 of the fiber F6 (fourth step). Here, the resin layer 74 is also formed on the first clad 721 of the first laser fiber 423. More specifically, as an example, the capillary 730, which has been inserted into either the fiber F6 or the first laser fiber 423 in advance, is arranged at a position covering the exposed portions 725 and 765. Then, the low refractive index resin is poured into the capillary 730 and filled to form the resin layer 740 in the capillary 730.

After that, the exposed portion 765 of the fiber F6 is made to face the PD453 via the resin layer 740 (fifth step). More specifically, the fiber F6 and the first laser fiber 423 are arranged in the groove 468 of the holder 464 on the surface 461a of the first support plate 461 so that the exposed portion 765 of the fiber F6 faces the PD453. Then, the holder 464 is fixed to the surface 461a. As described above, the excitation light detection structure 700 is manufactured. According to this method, the first laser fiber 423 and the fiber F6 are cut after the exposed portions 725,765 are formed by removing the second clad 722,762, so that a good cut surface can be obtained. Therefore, the loss in the fused portion M is reduced.

The above-described embodiment describes an example of the laser oscillator and the excitation light detection structure according to the present invention. Therefore, the laser oscillator and the excitation light detection structure according to the present invention are not limited to the above examples. The laser oscillator and the excitation light detection structure according to the present invention may be arbitrarily modified as described above without changing the gist of each claim.

For example, in the above example, a structure (excitation) for detecting excitation light in a fusion portion between a laser fiber (first laser fiber 423, second laser fiber 434) and a normal optical fiber (fiber F6, fiber F11). An optical detection structure 700,701) was constructed. However, at least a structure for detecting the excitation light may be configured in the fusion portion between ordinary optical fibers that propagate the excitation light.

Further, the exposed portion 725 of the first laser fiber 423 may be arranged so as to face the PD453. Even in this case, it is considered that the first excitation light PL1 (leakage light PL0) can be detected as in the case where the exposed portion 765 of the fiber F6 is opposed to the PD453 as described above. However, in this case, the light generated in the first laser fiber 423 may be detected as noise. Therefore, in this case, it is desirable to arrange a filter for blocking light having a wavelength generated in the first laser fiber 423 in front of the PD453. However, if the exposed portion 765 of the fiber F6 having no amplification function is arranged so as to face the PD453 as in the above example, the first excitation light PL1 can be detected without using a filter.

Further, instead of the capillary 730 made of glass, a high refractive index resin layer having a refractive index higher than that of the resin layer 740 may be provided so as to cover the resin layer 740. Also in this case, the first excitation light PL1 tends to leak from the resin layer 740.

Further, in the above embodiment, the configuration of backward excitation is adopted for the preamplifier unit 420, but in the first laser fiber 423, the first excitation light PL1 travels in the same direction as the traveling direction of the laser light L. The configuration may be adopted. Similarly, in the above embodiment, the rear excitation configuration is adopted for the power amplifier unit 430, but in the second laser fiber 434, the second excitation light PL2 travels in the same direction as the traveling direction of the laser light L. Excitation configurations may be adopted. In these cases, the laser light L does not substantially propagate to the optical fiber (second optical fiber) that propagates the first excitation light PL1 or the second excitation light PL2.

Further, the laser oscillator of the present invention is not limited to the laser machining apparatus 200 that forms a modified region inside the workpiece 1, but is mounted on a laser machining apparatus that performs other laser machining such as ablation machining and welding machining. It is also possible to do.

Further, in the laser processing apparatus 200, the polarizing plate unit 340 may be provided with a polarizing member other than the polarizing plate 342. As an example, a cube-shaped polarizing member may be used instead of the polarizing plate 342 and the optical path correction plate 343. The cube-shaped polarizing member is a member having a rectangular parallelepiped shape, and the side surfaces of the member facing each other are a light incident surface and a light emitting surface, and a layer having a function of a polarizing plate is provided between them. It is a member.

Further, in the laser processing apparatus 200, the axis on which the λ / 2 wave plate 332 rotates and the axis on which the polarizing plate 342 rotates do not have to coincide with each other.

Further, in the laser processing apparatus 200, the laser output unit 300 has mirrors 362 and 363 for adjusting the optical axis of the laser light L emitted from the laser output unit 300, but the laser output unit 300 emits light. It suffices to have at least one mirror for adjusting the optical axis of the laser beam L to be produced.

400 ... Laser oscillator, 410 ... Seed light emitting part, 411 ... Seed light LD (seed light source), 420 ... Preamp part (amplifier part), 423 ... First laser fiber (first optical fiber), 424 ... First excitation LD (Excitation light source), 430 ... Power amplifier unit (amplifier unit), 434 ... Second laser fiber (first optical fiber), 435 ... Second excitation LD (excitation light source), 453,457 ... PD (light detection element), 464,469 ... Holder, F6, F11 ... Fiber (second optical fiber), 700,701 ... Excitation light detection structure, 730 ... Capillary, 740 ... Resin layer, 760 ... Core, 761 ... First clad, 762 ... Second Clad, 764 ... Covering part, 765 ... Exposed part, L ... Laser light, PL1 ... First excitation light (excitation light), PL2 ... Second excitation light (excitation light), M ... Fusion part.

Claims (5)

A seed light emitting unit having a seed light source that emits a laser beam that is a seed light,
A first optical fiber for amplifying the laser light emitted from the seed light emitting unit while propagating, an excitation light source for emitting excitation light for exciting the first optical fiber, and the first optical fiber. An amplifier unit that is optically connected to and has at least a second optical fiber that propagates the excitation light and an optical detection element for detecting the excitation light.
The second optical fiber includes a core, a first clad provided around the core, a second clad provided around the core and the first clad, and around the core and the first clad. Including the resin layer provided in
The first clad includes a covering portion that covers the core and is covered by the second clad, and an exposed portion that covers the core and is exposed from the second clad.
The resin layer has a refractive index lower than that of the first clad, and covers the first clad at the exposed portion.
The photodetector is arranged so as to face the exposed portion via the resin layer.
Laser oscillator. The exposed portion includes a fusion portion with the first optical fiber.
The laser oscillator according to claim 1. The second optical fiber has a refractive index higher than that of the resin layer, and includes a capillary that further covers the resin layer in the exposed portion.
The laser oscillator according to claim 1 or 2. A holder for holding the photodetector is provided.
The second optical fiber is positioned by the holder so that the exposed portion faces the photodetector.
The laser oscillator according to any one of claims 1 to 3. Excitation for detecting the excitation light in a laser oscillator having a first optical fiber that amplifies while propagating the laser light and at least a second optical fiber that propagates the excitation light for exciting the first optical fiber. It is a method of manufacturing a light detection structure.
The second clad is removed in the second optical fiber including the core, the first clad provided around the core, and the core and the second clad provided around the first clad. As a result, the first step of exposing the first clad to form an exposed portion, and
A second step of forming a cut surface by cutting the second optical fiber in a part of the exposed portion, and
A third step of forming a fused portion by fusion-bonding the exposed portion to the first optical fiber on the cut surface.
A fourth step of forming a resin layer having a refractive index lower than that of the first clad on the first clad so as to cover the exposed portion.
A fifth step of making the exposed portion face the photodetector via the resin layer, and
To prepare
A method for manufacturing an excitation light detection structure.

Images