JP2010080642A - Fiber laser device, laser processing apparatus, and laser processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber laser device, a laser processing apparatus, and a laser processing method, capable of obtaining high power pulse laser beams efficiently. <P>SOLUTION: In the fiber laser device, the laser processing apparatus, and the laser processing method, the fiber laser device includes: a first seed light source for emitting first pulse seed beams; a second seed light source for emitting second pulse seed beams having a wavelength different from that of the first pulse seed beams; an excitation light source for emitting an excitation light; and an optical fiber in which a rare-earth element added to a core absorbs the excitation light, and which emits first laser beams having first amplified beams in which the first pulse seed beams are amplified and second amplified beams in which the second pulse seed beams are amplified. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fiber laser device, a laser processing device, and a laser processing method.

  A laser processing apparatus requires high-power pulsed laser light. For this reason, pulse seed light from a solid state laser or semiconductor laser is often amplified by a fiber amplifier to obtain high output pulse laser light.

  In the fiber amplifier, the excitation light is absorbed by the rare earth element added to the core, and gain is generated by stimulated emission to amplify the pulse seed light. However, since fiber amplifiers generally have a wide wavelength range that produces gain, it is difficult to efficiently extract the energy that is excited to a high output level and stored.

There is a technology disclosure example regarding an optical amplifier with good amplification efficiency (Patent Document 1). In this technical disclosure example, an optical fiber in which thulium and neodymium are added to the core is used as a gain medium, and spontaneous emission light having a wavelength of 0.8 μm generated during light amplification by thulium is absorbed by neodymium. Amplifies light efficiently.
However, using this example of technical disclosure is not sufficient to obtain the output required for the laser processing apparatus. For example, when it is necessary to perform laser processing after converting the wavelength of the pulse seed light using a nonlinear crystal, there is a problem that the conversion efficiency is lowered because the allowable wavelength width of the nonlinear crystal is narrow.
JP 2002-246673 A

  Provided are a fiber laser device, a laser processing device, and a laser processing method capable of extracting high-power pulsed laser light with high efficiency.

  According to one aspect of the present invention, a first seed light source capable of emitting a first pulse seed light and a second pulse seed light having a wavelength different from the wavelength of the first pulse seed light can be emitted. A second seed light source, an excitation light source capable of emitting excitation light, a first amplified light in which the rare earth element added to the core absorbs the excitation light and the first pulse seed light is amplified, There is provided a fiber laser device comprising: an optical fiber capable of emitting a first laser light having a second amplified light obtained by amplifying the second pulse seed light.

  According to another aspect of the present invention, the above-described fiber laser device, an irradiation optical unit that shapes the first laser light to form a beam, and a workpiece to be processed by the beam are mounted. There is provided a laser processing apparatus comprising a possible stage.

  According to still another aspect of the present invention, the first laser light emitted from the fiber laser device is shaped to form a beam, and the workpiece is irradiated while scanning the beam. A laser processing method is provided.

  Provided are a fiber laser device, a laser processing device, and a laser processing method capable of extracting high-power pulsed laser light with high efficiency.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a fiber laser device according to a first embodiment of the present invention. That is, FIG. 1A is a configuration diagram, FIG. 1B is a free-run spectrum from an optical fiber, FIG. 1C is a pulse seed light spectrum, and FIG. 1D is an amplified light spectrum. To express.

  The seed light source 10 has at least two light sources. The pulse seed light S1 from the first seed light source 10a and the pulse seed light S2 from the second seed light source 10b are combined by the first combiner 12 and can enter the optical fiber 18. In the case of a laser processing apparatus, infrared light is often used as the wavelength of pulse seed light, but in particular, the vicinity of 1000 nm is often used. Further, when the seed light source 10 is a semiconductor laser, its spectral width (Δλ) can usually be in the range of 1 to 2 nm. Note that the spectrum width Δλ is represented by a wavelength width at which the relative light intensity is one half of the peak value.

  A second combiner 14 is disposed between the first combiner 12 and the optical fiber 18. The second combiner 14 is provided to allow the excitation light E from the excitation light source 16 to enter the optical fiber 18. That is, the pulse seed lights S 1 and S 2 pass through the second combiner 14 and enter the core of the optical fiber 18 from the input end 18 a of the optical fiber 18. The pumping light E can enter the core and the clad from the input end 18a of the optical fiber 18 via the second combiner 14.

  Further, the wavelength of the excitation light E is, for example, in the range of 800 to 1100 nm. When the excitation light source 16 is composed of a semiconductor laser, a high output can be easily obtained by combining the outputs using a combiner (not shown). The mark ● represents the position where the fiber is fused.

  The optical fiber 18 has a core to which a rare earth element such as Yb (ytterbium) or Tm (thulium) is added, and a part of the excitation light E is absorbed by the rare earth element while passing through the core. The pulse seed lights S1 and S2 are amplified due to the gain generated by stimulated emission from the excited rare earth element, and can be emitted from the output end 18b of the optical fiber 18.

  When the fiber amplifier 19 is configured using the optical fiber 18 made of Yb-doped silica fiber, the free-run spectrum has spectral maximum values in the vicinity of about 1040 nm and about 1075 nm as shown in FIG. The gain width is several tens of nanometers, for example, and is at least several times wider than the spectral width of the semiconductor laser.

  As shown in FIG. 1C, when the average output Ps of the pulse seed lights S1 and S2 is lowered to 2 W or the like, the spectrum width is narrower than 2 nm, for example, 1.5 nm. Further, the center wavelengths of the pulse seed lights S1 and S2 are within the range of the gain width of FIG. 1B, and the difference between the center wavelengths is larger than any of the respective spectrum widths.

  If the average output Pg of the amplified light G1 and G2 of the pulse seed light S1 and S2 is 15 W, for example, the spectrum width is approximately 2 nm, and the spectrum is as shown in FIG.

  In the first embodiment, in the fiber amplifier 19 having a wide gain width, two or more pulse seed lights are used, and the difference between the respective center wavelengths is made larger than any of the spectral widths of the pulse seed lights S1 and S2. It is possible to effectively widen the wavelength width of the pulse seed light. For this reason, it becomes easy to efficiently extract the energy stored in the wide gain range of the optical fiber 18.

FIG. 2 is a diagram for explaining the spectrum of the fiber laser device according to the comparative example. That is, FIG. 2A shows a spectrum of pulse seed light, and FIG. 2B shows a spectrum of amplified light in a highly excited state.
As shown in FIG. 2A, the pulse seed light S11 has a spectral width narrower than 2 nm, for example. In the case of high excitation such as an average output of 70 W, the amplified light G11 has a spectrum width that extends to approximately 5 nm. The fiber amplifier has a wide gain range, and there is gain even at a wavelength away from the center wavelength of the pulse seed light S11. For this reason, it is easy to extract the amplified light at the center wavelength, but it becomes difficult to extract the energy accumulated in the optical fiber at a wavelength away from the center wavelength.

FIG. 3 is a graph showing the excitation level dependence of the spectral width of the amplified light. 3A shows the relative light intensity of the pulse seed light of Ps = 2 W, FIG. 3B shows the amplified light of Pg = 15 W, and FIG. 3C shows the amplified light of Pg = 70 W.
The pulse seed light Ps is emitted light from the semiconductor laser, and its spectral width Δλ is 1.5 nm, for example. When the excitation is increased and the average output Pg of the amplified light is increased to 15, 70 W, the average output Pg gradually saturates and the gain decreases at the center wavelength. That is, as the excitation is increased, the output is saturated at the center wavelength, so that the energy that can be extracted by stimulated emission using one pulse seed light is limited, and the efficiency decreases. Further, a gain remains in the vicinity slightly away from the center wavelength, and the spectrum width Δλ gradually widens to 2 nm (Pg = 15 W) and 5 nm (Pg = 70 W).

  In the first embodiment, the average output Pg is suppressed to 15 W or the like so that the amplified lights G1 and G2 of the pulse seed lights S1 and S2 are not saturated. In addition, at least two pulse seed lights S1 and S2 having a center wavelength separated by a spectrum width or more are incident on the fiber amplifier 19 and are amplified at the respective wavelengths. Since the two amplified lights G1 and G2 can suppress the output saturation and keep the gain high, the energy stored in the optical fiber 18 can be extracted with high efficiency.

  When this fiber laser device 5 is used as a light source of a laser processing apparatus, the amplified lights G1 and G2 are efficiently absorbed by the workpiece. The number of pulse seed lights is not limited to two, and third pulse seed light S3 or the like may be used. When the number of pulse seed lights is increased within the gain width of the fiber amplifier 19, the energy irradiated and absorbed on the workpiece can be increased.

FIG. 4 is a configuration diagram of a fiber laser device according to the second embodiment.
In this embodiment, the second harmonic (wavelength is one half of the fundamental wave) or the third harmonic (wavelength is one third of the fundamental wave) can be generated using a nonlinear crystal. It is. The fiber laser device 5 of this figure further includes a distributor 40 that separates at least two amplified lights G1 and G2 having different center wavelengths, a wavelength converter 50, and a timing controller 30.

The wavelength conversion unit 50 includes nonlinear crystal elements 52 and 54 such as a SHG (Second Harmonic Generation) element and a THG (Third Harmonic Generation) element. The material of the nonlinear crystal elements 52 and 54 can be, for example, LBO: LiB ₃ O ₅ or the like. When the wavelengths of the pulse seed lights S1 and S2 are in the infrared light range, the wavelengths of the wavelength converted lights H1 and H2 can be in the wavelength range of ultraviolet to visible light.

FIG. 5 is a diagram illustrating the spectral widths of the amplified light and the wavelength converted light in the present embodiment. 5A is a timing diagram of pulse seed light, FIG. 5B is a spectrum of amplified light, and FIG. 5C is a spectrum of wavelength converted light.
The pulse seed lights S1 and S2 are alternately emitted by the timing controller 30, and the spectral width Δλ is set to 2 nm or less, and the difference between the central wavelengths is determined by any of the spectral widths of the respective pulse seed lights S1 and S2. Is also assumed to be large.

  In this case, when the average output Pg of the amplified lights G1 and G2 is about 15 W, the spectrum width Δλ becomes slightly larger than 2 nm as shown in FIG. For this reason, the effective spectral width Δλ obtained by combining the amplified lights G1 and G2 becomes larger than 5 nm. In the present embodiment, since the output saturation of the two amplified lights G1 and G2 can be suppressed, it is easy to keep the extraction efficiency high.

  When laser processing is performed using the output from the output end 18b of the optical fiber 18, a beam may be formed using the laser light GT having the amplified light G1 and G2, and the workpiece may be irradiated.

  As shown in FIG. 5C, the allowable wavelength width of the nonlinear crystal elements 52 and 54 is as narrow as 1 nm, for example. Since this spectral width Δλ is usually narrower than the spectral width of the amplified light, the nonlinear crystal element 52 that converts the wavelength of the amplified light G1 and the nonlinear crystal element 54 that converts the wavelength of the amplified light G2 are separated into different optical paths. It is preferable to do. That is, by using the EO element 42 synchronized with the seed light source 10 by the timing controller 30, the optical path including the nonlinear crystal element 52 or the optical path including the nonlinear crystal element 54 is switched.

FIG. 6 is a graph showing the spectrum of wavelength converted light. 6A shows the relative light intensity of the fundamental wave, FIG. 6B shows the second harmonic, and FIG. 6C shows the relative light intensity of the third harmonic.
When the spectrum width Δλ of the fundamental wave is approximately 4 nm, the spectrum width Δλ of the second harmonic is as narrow as approximately 1 nm, and the spectrum width Δλ of the third harmonic is as narrow as approximately 0.5 nm. The allowable wavelength width for wavelength conversion is determined by the length of the nonlinear crystal, but is usually narrow in this way. For this reason, it is difficult to use the energy accumulated in the optical fiber with high conversion efficiency even when the excitation light G1 and G2 are excited so that the spectral width is as wide as 5 nm as shown in FIG. It becomes.

  In contrast, in the present embodiment, the spectral width Δλ of the amplified light S1 and S2 whose generation timings are alternated is narrowed so as to approach the allowable wavelength width of the nonlinear crystal element 52. If it does in this way, it will become easy to raise the conversion efficiency to wavelength conversion light H1 and H2. Further, since at least two amplified lights G1 and G2 are used, the energy accumulated in the optical fiber 18 can be extracted efficiently. In this way, it is possible to emit the laser light GT having the wavelength conversion lights H1 and H2. Use of laser light in the ultraviolet to visible wavelength range generated by wavelength conversion facilitates laser annealing of the semiconductor layer and processing of the liquid crystal display device.

In FIG. 4, the EO (Electro-Optic) element 42 and the timing controller 30 are synchronized. That is, using the EO element 42, the amplified light G1 and G2 can be separated by the polarizer 44 depending on the difference between when the polarization is rotated 90 degrees and when the polarization is not rotated. Even in the case of two or more amplified lights, separation can be performed by arranging the polarizers 44 in series with respect to the EO element 42 in multiple stages. As a material for the EO element 42, KH ₂ PO ₄ , LiNbO ₃ or the like can be used.

Further, using an AO (Acousto-Optic) element instead of the EO element, the amplified lights G1 and G2 can be separated even if the refraction angle is changed. The AO element is made of a material such as LiTaO ₃ , LINbO ₃ , TeO ₂ , and CdS. The refractive index is periodically changed by ultrasonic waves generated by a high frequency voltage, and the direction of polarization can be controlled.

   Further, in the case of a Tm-doped optical fiber having a wide gain width, when the center wavelength difference between the amplified lights G1 and G2 is increased, the amplified lights G1 and G2 can be separated and combined using a dichroic mirror.

  For example, a polarizer (in the case of an EO element), a combiner, a dichroic mirror, or the like can be used as the laser beam GT (combining) means 45 by combining the optical axes of the wavelength-converted lights H1 and H2 by the nonlinear crystal elements 52 and 54. .

FIG. 7 is a configuration diagram of the laser processing apparatus according to the present embodiment.
FIG. 8 is a flowchart showing the laser processing method.
The laser processing apparatus can mount a fiber laser apparatus 5 as shown in FIG. 1 or 4, an irradiation optical unit 60 that forms a beam BT in a desired shape and enables beam scanning, and a workpiece 64. A stage 62 is provided.

  Two pulse seed lights S1 and S2 whose center wavelengths are separated by more than the respective spectral widths are generated from the seed light source and amplified by a fiber amplifier (S102).

  Subsequently, it is determined whether or not wavelength conversion of the amplified light G1 and G2 is performed (S104). If YES, the pulse seed light S1 and S2 are separated by a distributor (S106), and wavelength conversion is performed by a nonlinear crystal element. Perform (S108). If NO, the process proceeds to beam shaping (S112).

  The wavelength converted lights H1 and H2 that have undergone wavelength conversion are aligned again (S110) to become laser light GT. The laser beam GT is shaped into a beam BT having a desired shape by the irradiation optical unit 60 (S112). The shape of the beam BT can be formed in, for example, a line shape or a spot shape. When the line-shaped beam BT is used, if the width is several to 50 μm and the line beam length is 500 nm, the workpiece 64 can be processed with high throughput.

  The beam BT is irradiated while being scanned onto the workpiece 64 placed on the stage 62 (S114). In this way, annealing of a semiconductor or the like, processing of a liquid crystal device, processing of glass, and the like can be performed, and it becomes easy to increase productivity in the manufacturing process of an electronic device.

  Further, the laser processing apparatus according to the present embodiment is a solid-state laser system, and it is not necessary to use halogen gas or the like, and maintenance of the apparatus is easy. In addition, although the pulse width is approximately 30 ns in the excimer laser, in the present embodiment, the pulse width can be made variable, for example, it can be easily increased.

  The embodiment of the present invention has been described above with reference to the drawings. However, the present invention is not limited to these embodiments. Those skilled in the art made various design changes regarding materials, shapes, sizes, arrangements, etc. of the optical fiber, seed light source, distributor, wavelength conversion unit, irradiation optical unit, excitation light source, and timing controller constituting the present invention. However, it is included in the scope of the present invention without departing from the gist of the present invention.

The figure showing the fiber laser apparatus concerning a 1st embodiment The figure explaining the spectrum of the fiber laser apparatus concerning a comparative example A graph showing the excitation level dependence of the spectral width of the amplified light The block diagram of the fiber laser apparatus concerning 2nd Embodiment The figure explaining the spectrum width of amplified light and wavelength conversion light Graph showing the spectrum of wavelength converted light Configuration diagram of laser processing equipment Flow diagram showing laser processing method

Explanation of symbols

  5 fiber laser device, 10 seed light source, 16 excitation light source, 18 optical fiber, 30 timing controller, 40 distributor, 42 EO element, 50 wavelength conversion unit, 52, 54 nonlinear crystal element, 60 irradiation optical unit, 62 stage, 64 Workpiece, S1, S2 Pulse seed light, G1, G2 amplified light, H1, H2 wavelength conversion light, GT laser light, BT beam, E excitation light

Claims (8)

A first seed light source capable of emitting a first pulse seed light;
A second seed light source capable of emitting a second pulse seed light having a wavelength different from the wavelength of the first pulse seed light;
An excitation light source capable of emitting excitation light;
A rare earth element added to the core absorbs the excitation light, and a first amplified light obtained by amplifying the first pulse seed light and a second amplified light obtained by amplifying the second pulse seed light. An optical fiber capable of emitting a first laser beam having;
A fiber laser device comprising: A distributor capable of separating the first amplified light and the second amplified light;
A wavelength conversion unit including: a first nonlinear crystal element that converts the first amplified light into a harmonic; and a second nonlinear crystal element that converts the second amplified light into a harmonic;
Further comprising
2. The second laser light having a first converted light by the first nonlinear crystal element and a second converted light by the second nonlinear crystal element can be emitted. The fiber laser device described. The difference between the wavelength of the first pulse seed light and the wavelength of the second pulse seed light is:
3. The fiber laser device according to claim 1, wherein the fiber laser device is larger than both of a spectrum width of the first pulse seed light and a spectrum width of the second pulse seed light.   4. The fiber laser device according to claim 1, wherein the spectrum width of the first pulse seed light and the spectrum width of the second pulse seed light are 2 nm or less. 5. .   The fiber according to any one of claims 1 to 4, further comprising a timing controller that shifts the incident timing of the first and second pulse seed lights so that the first and second pulse seed lights can enter the optical fiber. Laser device.   The distributor includes any one selected from the group consisting of an electro-optic element that can be controlled by the timing controller, an acousto-optic element that can be controlled by the timing controller, and a dichroic mirror. Item 6. The fiber laser device according to Item 5. The fiber laser device according to any one of claims 1 to 6,
An irradiation optical unit that shapes the first or second laser beam to form a beam;
A stage on which a workpiece to be processed by the beam can be placed;
A laser processing apparatus comprising: A beam is formed by shaping the first or the second laser light emitted from the fiber laser device according to any one of claims 1 to 6.
A laser processing method for irradiating a workpiece while scanning the beam.

Images