JP2012243789A - Fiber laser processing apparatus and laser processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for an expensive high output optical isolator while surely preventing damage on the light source or the optical components due to reflection return light, in a master oscillator power amplifier (MOPA) system fiber laser processing apparatus.SOLUTION: In the fiber laser processing apparatus, a seed light generation unit 10, an active fiber 12, a wavelength conversion fiber 14 and an optical beam irradiation unit 16 are cascaded optically via an optical isolator 18, an optical coupler 20 and optical filters 22, 24. The first optical filter 22 passes only the wavelength of the seed light selectively. The wavelength conversion fiber 14 functions as a nonlinear medium for generating stimulated Raman scattering light from high power pump light. The second optical filter 24 passes all or a part of the wavelength band of stimulated Raman scattering light(SRS light) selectively out of the light beam output from the output end of the wavelength conversion fiber 14.

Description

  The present invention relates to a MOPA-type fiber laser processing apparatus and a laser processing method for performing desired laser processing by irradiating a workpiece with a light beam obtained by amplifying seed light in an optical fiber.

  Recently, fiber laser processing apparatuses that perform desired laser processing by irradiating a workpiece with laser light generated by a fiber laser have become widespread. Among them, a fiber laser processing apparatus of the MOPA (Master Oscillator_Power Amplifier) method is also attracting attention.

  The fiber MOPA system uses an optical fiber in which a rare earth element such as Yb is added to the core as the active fiber for laser amplification, and the low-power seed light generated by the seed laser enters the core of the active fiber from one end to the other end. The seed light is amplified or converted into a high-power processing light beam in the core by exciting the core with the excitation light while propagating to a high power / light conversion efficiency and beam mode. It has features such as stability.

  However, in the MOPA fiber laser processing apparatus, when the workpiece is irradiated with the processing light beam, a part of the reflected light from the workpiece is directed in the opposite direction to the laser emission optical system and the laser transmission optical system. May propagate and return to the active fiber. Such reflected return light is amplified in the active fiber and damages the active fiber, the seed LD, the excitation light source, and the like.

  Conventionally, with respect to this problem, an optical isolator is inserted into the optical transmission line downstream of the active fiber so that reflected return light from the workpiece is blocked by the optical isolator. This type of optical isolator consists of optical components such as a polarizing element and a Faraday rotator, and has a function of passing forward light (processing light beam) and blocking reverse light (reflected return light). doing.

US Pat. No. 6,275,250

  As described above, the optical isolator provided in the subsequent stage of the active fiber is for a high-power fiber laser, and therefore has a large size and a very high price. In general, the higher the optical power, the more expensive the optical isolator.

  Further, the reverse transmittance or reverse insertion loss of a normal optical isolator is about −30 dB, and a part of the reflected return light is transmitted slightly. However, a slight amount of reflected return light that has passed through the optical isolator is amplified to high power while propagating in the reverse direction through the active fiber, which may cause damage to the light source and optical components in the MOPA laser.

  Further, the reverse transmittance of the optical isolator has a wavelength dependency, and the wavelength to be used is determined. For this reason, for example, when the wavelength of the seed light fluctuates depending on the temperature characteristics of the seed light source, and the wavelength of the reflected return light deviates from the use wavelength, the reverse transmittance decreases from the standard value of −30 dB to, for example, −25 dB, The shut-off performance of the specification is not guaranteed. Furthermore, the optical isolator usually has a forward loss of about 1.0 dB. This forward loss also has the same wavelength dependency as described above. When the wavelength of the seed light deviates from the use wavelength, the forward loss increases at a stretch. In addition, it is very difficult to manufacture an optical isolator to expand the wavelength used.

  The present invention solves the problems of the prior art as described above, eliminates the need for an expensive high-power optical isolator, and more reliably prevents damage to the light source and optical components due to reflected return light. A MOPA type fiber laser processing apparatus and a laser processing method are provided.

  A MOPA fiber laser processing apparatus according to a first aspect of the present invention includes a seed light generation unit that generates seed light and a core to which a rare earth element is added, and the seed light from the seed light generation unit is input to an input terminal. An optical fiber for amplification that is amplified by stimulated emission while propagating the seed light toward the output end, and an excitation light source that generates excitation light for exciting the core of the optical fiber for amplification And an optical coupler that optically couples the seed light generator and the pumping light source to the input end of the amplification optical fiber, and an optically nonlinear core, and is output from the amplification optical fiber. A wavelength conversion that generates a stimulated Raman scattering light while propagating the pump light toward the output end by inserting a light beam having the same wavelength as the seed light into the core from the input end as pump light. An optical fiber, a light beam irradiating unit for condensing and irradiating the workpiece with the stimulated Raman scattered light output from the wavelength converting optical fiber as a processing laser beam, the amplification optical fiber, and the wavelength converting light A wavelength of the stimulated Raman scattering light provided between the first optical filter that transmits only the wavelength of the seed light, the wavelength conversion optical fiber, and the light beam irradiation unit. And a second optical filter that only transmits light.

  In the above configuration, the weak power seed light is amplified by the amplification optical fiber, and the high-power pump light obtained thereby is injected into the wavelength conversion optical fiber through the first optical filter, and the wavelength conversion optical fiber is injected. Stimulated Raman scattered light is generated in the optical fiber. Then, the stimulated Raman scattering light is extracted from the light beam emitted from the output end of the wavelength conversion optical fiber by the second optical filter and used as the processing light beam. During laser processing, part of the reflected light from the workpiece may propagate in the reverse direction through the light beam irradiation unit, the second optical filter, and the wavelength conversion optical fiber as return light. However, such reflected return light is blocked by the first optical filter before entering the amplification optical fiber.

  A MOPA fiber laser processing apparatus according to a second aspect of the present invention includes a seed light generation unit that generates seed light and a first core to which a rare earth element is added, and the seed light from the seed light generation unit. Is input into the first core from the input end, and the first amplification optical fiber that amplifies by stimulated emission while propagating the seed light, and the first core of the first amplification optical fiber are excited. A first pumping light source for generating first pumping light for optically transmitting, a first light source for optically coupling the seed light generating unit and the first pumping light source to an input end of the first optical fiber for amplification And a second core to which a rare earth element is added, and a first-stage amplified light beam output from the output end of the first amplification optical fiber is input from the input end to the second core. And transmit the first stage amplification light beam. A second amplifying optical fiber that amplifies by stimulated emission while generating a second excitation light for exciting a second core of the second amplifying optical fiber, A second optical coupler for optically coupling the output end of the first amplification optical fiber and the second pumping light source to the input end of the second amplification optical fiber, and an optically nonlinear core A second-stage amplification light beam output from the second amplification optical fiber is introduced as pump light into the core from the input end, and the pump light is propagated toward the output end to induce Raman A wavelength conversion optical fiber that generates scattered light, a light beam irradiation unit that condenses and irradiates a workpiece with the stimulated Raman scattered light output from the wavelength conversion optical fiber as a processing laser beam, and the second Amplifying optical fiber and said wavelength A first optical filter that is provided between the optical fiber for replacement and transmits only the wavelength of the seed light; and provided between the optical fiber for wavelength conversion and the light beam irradiation unit, and the stimulated Raman scattering. And a second optical filter that transmits only the wavelength of light.

  In the above configuration, the same effect as the fiber laser processing apparatus in the first aspect can be obtained as a countermeasure against reflected return light, and a plurality of amplification optical fibers, that is, optical amplifiers are cascade-connected, so that The power of the pump light and the processing light beam can be arbitrarily or freely increased while making the power as low as possible.

  The laser processing method of the present invention includes a step of generating seed light having a center wavelength of about 1060 nm using a laser diode, and propagating the seed light together with excitation light in the core of an optical fiber for amplification. The light beam having the same wavelength as the first seed light is extracted as pump light from the light amplified by stimulated emission and the light output from the amplification optical fiber using the first optical filter. A step of introducing the pump light into a wavelength conversion optical fiber having an optically nonlinear core to generate stimulated Raman scattered light in the wavelength conversion optical fiber, and the wavelength conversion optical fiber A step of extracting a wavelength component of 1080 to 1300 nm of the stimulated Raman scattering light as processing laser light from the output light using a second optical filter; The processing laser beam to a given workpiece by irradiating light collecting and a step of subjecting the desired laser processing.

  According to the above configuration, it is possible to achieve both the most efficient and reliable compatibility between the countermeasures for reflected return light and the increase in laser output in the MOPA fiber laser processing.

  According to the fiber laser processing apparatus of the present invention, the light source and optical components in the apparatus are damaged by the configuration and operation as described above without providing an expensive high output optical isolator at the final output end. The reflected return light from the workpiece can be reliably blocked without any problem.

  In addition, according to the laser processing method of the present invention, it is possible to prevent damage to the light source and optical components in the apparatus and to perform high-quality laser processing with a high-power light beam.

It is a block diagram which shows the structure of the MOPA system fiber laser processing apparatus in one Embodiment of this invention. It is a figure which shows the pulse waveform of the power of the light beam in each part of the said MOPA system fiber laser processing apparatus. It is a figure which shows the wavelength spectrum of the light beam in each part of the said MOPA system fiber laser processing apparatus. It is a figure which shows the relationship between the peak power (16 kW) of pump light, and the wavelength spectrum of SRS light. It is a figure which shows the relationship between the peak power (18 kW) of pump light, and the wavelength spectrum of SRS light. It is a figure which shows the relationship between the peak power (20 kW) of pump light, and the wavelength spectrum of SRS light. It is a figure which shows the relationship between the peak power (22 kW) of pump light, and the wavelength spectrum of SRS light. It is a figure which shows the relationship between the peak power (24 kW) of pump light, and the wavelength spectrum of SRS light. It is a figure which shows the relationship between the peak power (26 kW) of pump light, and the wavelength spectrum of SRS light. It is a block diagram which shows the structure of the MOPA system fiber laser processing apparatus in one modification.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows the configuration of a MOPA fiber laser processing apparatus according to an embodiment of the present invention. This MOPA type fiber laser processing apparatus can perform laser processing such as marking and drilling by irradiating a workpiece with a light beam having a pulse waveform obtained by amplifying a pulse waveform of seed light in an optical fiber. It has become.

  The fiber laser processing apparatus mainly includes a seed light generation unit 10, an amplification optical fiber (hereinafter referred to as "active fiber") 12, a wavelength conversion optical fiber (hereinafter referred to as "wavelength conversion fiber") 14, and an optical device. The beam irradiation unit 16 is optically cascaded through an optical isolator 18, an optical coupler 20, and optical filters 22 and 24.

The seed light generator 10 is a laser diode for seeding (hereinafter referred to as “seed LD”) 26 and an LD that drives the seed LD 26 with a pulse waveform current to generate seed light (LD light) having a pulse waveform. Drive circuit 28. Seed LD26 is constructed as a fiber coupling LD, the spectrum center wavelength oscillates and outputs a seed light pulse waveform of 1060nm several W or less low peak power P _A.

  An optical coupler 20 provided between the seed light generator 10 and the active fiber 12 includes a plurality of input ports 20IN (1), 20IN (2), 20IN (3),... And one output port 20OUT. Have. A seed LD 26 is connected to the first input port 20IN (1) via the optical isolator 18. An excitation LD (hereinafter referred to as “pump LD”) 30 for exciting the core of the active fiber 12 is connected to the second and third and subsequent input ports 20N (2), 20IN (3),. Is done. The input port of the active fiber 12 is connected to the output port 20OUT.

  The seed light generation unit 10, the optical isolator 18, and the optical coupler 20 constitute a seed light injection unit for the active fiber 12. The pump LD 30 and the optical coupler 20 constitute an excitation light injection unit for the active fiber 12.

  The optical isolator 18 is small and inexpensive because the seed light of the weak power (usually several W or less) output from the seed LD 26 and its reflected return light are incident light in the forward direction and the reverse direction, respectively. I can do it.

  The active fiber 12 has a core made of quartz added with at least Yb ions and a clad made of, for example, quartz surrounding the core coaxially, and the total length (fiber length) is selected to be, for example, 3 to 15 m. . The gain of the active fiber 12 can be adjusted, for example, in the range of 10 to 40 dB by the total output of the pump LD30.

  The first optical filter 22 provided between the active fiber 12 and the wavelength conversion fiber 14 is composed of, for example, a transmission type or reflection type mirror formed by forming a dielectric multilayer film having wavelength selectivity on a glass substrate. The band-pass filter selectively transmits only the wavelength of the seed light, that is, only the wavelength of the spectrum center wavelength (1060 nm) and the narrow band in the vicinity thereof (for example, 1055 to 1065 nm).

  The light beam output from the active fiber 12 is obtained by amplifying the seed light by stimulated emission in the active fiber 12 as will be described later, and has the same wavelength as the seed light. Therefore, the light beam incident on the optical filter 22 from the output end of the active fiber 12 passes through the optical filter 22 as it is and enters the input end of the wavelength conversion fiber 14 as high-power pump light.

  The wavelength conversion fiber 14 is a nonlinear medium for generating stimulated Raman scattered light from high-power pump light, and preferably has an optically nonlinear core and is excellent in high power resistance. An inexpensive silica-based fiber used for optical transmission, particularly a pure silica-based fiber containing no additive is preferably used.

  In the present invention, as will be described later, in order to adjust the spectral width of the stimulated Raman scattering light (SRS light) to an appropriate range, the core diameter φ of the wavelength conversion fiber 14 is set to 20 to 40 μm, and the total length of the fiber is set to 2 to 10 m. It is preferable to select.

  The second optical filter 24 provided between the wavelength conversion fiber 14 and the light beam irradiation unit 16 is composed of a transmission type or reflection type mirror having the same configuration as the first optical filter 22, and the wavelength conversion fiber 14. A band that selectively transmits all or part of the wavelength band of the SRS light from the light beam output from the output terminal (for example, as described later, when the seed light wavelength is 1060 μm, it is 1080 to 1300 nm). It is configured as a path filter. The operation of the optical filters 22 and 24 and the wavelength conversion fiber 14 will be described in detail later.

  The light beam irradiation unit 16 receives the SRS light having a pulse waveform extracted by the second optical fiber 24, that is, the processing light beam LB through an optical transmission system such as the collimator 32 and the vent mirror 34, and receives the received processing beam. The light beam LB is condensed and applied to a desired position on the surface of the workpiece W on the stage 36. For example, when marking is performed, a galvano scanner is mounted on the light beam irradiation unit 16.

  The control unit 38 includes a microcomputer connected to an input device 40 such as a keyboard or a mouse, a display (not shown), and the like, and controls each unit in the device and the entire device based on a control program stored in a memory. I do.

  Next, the operation of this MOPA fiber laser processing apparatus will be described with reference to FIGS. FIG. 2 shows the pulse waveform of the power of the light beam in each part in the apparatus, and FIG. 3 shows the wavelength spectrum of the light beam in each part in the apparatus.

In this MOPA type fiber laser processing apparatus, when marking is performed, the seed light generator 10 generates seed light (LD light) having a pulse waveform with a spectrum center wavelength of 1060 nm to a desired pulse width (for example, 0.1 to 200 ns). , output in a desired peak power P _a (e.g. 100～2000MW) and the desired repetition frequency (e.g. 20~500kHz). 2A and 3A show the pulse waveform and wavelength spectrum of the seed light. Note that the repetition frequency can be set in the range of 10 kHz to 1 MHz, for example. The seed light having a pulse waveform output from the seed light generator 10 is injected into the core of the active fiber 12 via the isolator 18 and the optical coupler 20.

  On the other hand, the pump LD 30 outputs continuous wave (cw) excitation light having a spectrum center wavelength of a predetermined value, for example, 915 nm (or 940 nm or 975 nm). The continuous wave excitation light output from the pump LD 36 is injected into the core of the active fiber 12 via the optical coupler 24.

  In the active fiber 12, the seed light propagates in the core in the axial direction toward the fiber output end side while being confined by total reflection at the interface between the core and the clad. On the other hand, the excitation light propagates in the active fiber 12 in the axial direction while being confined by total reflection at the cladding outer peripheral interface, and optically excites Yb ions in the core by crossing the core many times during the propagation.

Thus, while the seed light and the pump light propagate through the active fiber 12, the absorption of the pump light spectrum and the stimulated emission of the seed light spectrum are repeatedly performed in the Yb-doped core, which is much higher than the output end of the active fiber 12. A seed light having a pulse waveform amplified to have a high peak power P _B (preferably 10 kW or more, more preferably 20 kW or more), that is, a light beam of an amplified pulse is emitted. The spectral center wavelength of the light beam of this amplified pulse is the same (1060 nm) as the spectral center wavelength of the seed light. FIG. 2B and FIG. 3B show the pulse waveform and wavelength spectrum of the light beam of the amplified pulse obtained at the output end of the active fiber 12.

  The light beam of the amplified pulse emitted from the output end of the active fiber 12 passes through the first optical filter 22 with almost no attenuation, and is injected into the input end of the wavelength conversion fiber 14 as pump light. Even if harmonics or scattered light based on the nonlinear effect is generated in the active fiber 12, it is blocked by the first optical filter 22, and therefore does not enter the wavelength conversion fiber 14 at the subsequent stage.

Thus, when pump light having a power exceeding the Raman threshold is incident on the wavelength conversion fiber 14 which is a nonlinear medium, the wavelength of the pump light (that is, the seed) is caused by stimulated Raman scattering based on molecular vibration or lattice vibration of quartz in the wavelength conversion fiber 14. Light having a wavelength slightly longer than that of the light, so-called Stokes light is generated. In addition, in this embodiment, since the peak power P _B of the pump light is well above the Raman threshold, not only the primary Stokes light shifted from the pump light to a slightly longer wavelength is generated but also slightly longer from the primary Stokes light. Second-order Stokes light shifted to the wavelength, and third-order Stokes light shifted from the second-order Stokes light to a slightly longer wavelength, and so on. Higher-order Stokes light is successively derived until the Raman threshold is not exceeded. A light beam having a pulse waveform having wavelength components of the stimulated Raman scattering light (SRS light) including the first-order and higher-order Stokes lights and the pump light is output from the output end of the wavelength conversion fiber 14.

  FIG. 2C and FIG. 3C show the pulse waveform and wavelength spectrum of the light beam obtained from the output end of the wavelength conversion fiber 14. As shown in FIG. 3C, the wavelength of SRS light is added to the wavelength of pump light in terms of wavelength spectrum. However, in terms of power, since the power of the pump light is only shifted to the power of the SRS light, the power of the entire light beam is hardly changed as shown in FIG.

4A to 4F show the interphase relationship (experimental results) between the peak power P _{B of the} pump light injected into the input end of the wavelength conversion fiber 14 and the wavelength spectrum of the SRS light obtained at the output end of the wavelength conversion fiber 14. Show.

As shown in the figure, it can be seen that the higher the peak power P _B of the pump light, the wider the spectral width (area) of the SRS light, that is, the shift of the optical energy from the pump light to the SRS light increases. However, if the spectrum width of the SRS light is too wide, the following problem occurs.
(i) When the spectrum width of the SRS light is too wide, the wavelength component outside the transmission band of the second optical filter 24 increases. That is, the amount of light that does not pass through the second optical filter 24 (light that cannot be used for laser processing) increases, and the use efficiency of laser energy decreases.
(ii) Conversion loss increases in the process of increasing the spectral width of SRS light, and the wavelength conversion efficiency decreases.
(iii) If the spectral width of the SRS light is excessively widened, chromatic aberration occurs and the light beam cannot be condensed.
(iv) Increasing the transmission band of the second optical filter 24 increases the cost.

From the viewpoints of (i) to (iv) above, in the MOPA fiber laser processing apparatus of this embodiment, when LD light having a spectral center wavelength of 1060 nm is used as seed light, the spectral width of SRS light is adjusted to 1080 to 1300 nm. It was confirmed in various experiments that it was most preferable to do this. Based on this knowledge, in this embodiment, a bandpass filter having a transmission band of 1080 to 1300 nm is used for the second optical filter 24. Then, the core diameter and the total length of the wavelength conversion fiber 14 and the peak power of the pump light are adjusted so that the wavelength spectrum characteristic of the SRS light incident on the second optical filter 24 is adapted (fit) to this specific band (1,080 to 1300 nm). Select P _B.

4A to 4F, a quartz fiber having a core diameter of 20 μm and a total length of 5 m was used for the wavelength conversion fiber 14. In this case, when the peak power P _B of the pump light is selected to be 22 to 26 kW, the wavelength spectrum characteristics (FIG. 4D, FIG. 4E, FIG. 4F) of the SRS light suitable for the specific band (1080 to 1300 nm) are obtained. Obtained.

  In this way, the light beam including the wavelength component of the pump light and the wavelength component of the SRS light enters the second optical filter 24 from the output end of the conversion fiber 14. The second optical filter 24 selectively or limitedly transmits only the wavelength component (preferably 1080 to 1300 nm) of the SRS light, and blocks the wavelength component of the pump light.

  The light beam composed of the wavelength component of the SRS light extracted by the second optical filter 24 is sent to the light beam irradiation unit 16 through the collimator 32 and the vent mirror 34 as a processing light beam LB.

  The light beam irradiation unit 16 includes a galvano scanner for marking and an fθ lens. The galvano scanner has a pair of movable mirrors capable of swinging in two directions orthogonal to each other. Under the control of the control unit 38, the galvano scanner is synchronized with the pulse oscillation operation of the seed light generating unit 10. By controlling the direction to a predetermined angle, the processing light beam LB is condensed and irradiated to a desired position on the surface of the workpiece W on the stage 36. The marking process performed on the surface of the workpiece W typically draws characters, figures, and the like, but surface removal processes such as trimming are also possible.

  During such laser processing, part of the light reflected by the workpiece W propagates in the reverse direction through the light beam irradiation unit 16, the vent mirror 34, and the collimator 32 as reflected return light, so that the second optical filter. May come up to 24. Since this reflected return light has the same wavelength as that of the processing light beam LB, it passes through the second optical filter 24 in the reverse direction, and further passes through the wavelength conversion fiber 14 in the reverse direction. However, the reflected return light is blocked by the first optical filter 22 after leaving the wavelength conversion fiber 14. In this case, the reflected return light reaches the first optical filter 22 without being amplified on the way. Therefore, the optical components (light beam irradiation unit 16, vent mirror 34, collimator 32, second optical filter 24, and wavelength conversion fiber 14) in the middle are not damaged by the reflected return light. On the other hand, the first optical filter 22 can completely block the reflected return light without leaking.

  As described above, in this MOPA type fiber laser processing apparatus, it is possible to use the low-cost optical filters 22 and 24 and the wavelength conversion fiber 14 without providing an expensive high-power optical isolator in the subsequent stage of the active fiber 12. All the light sources (26, 30) and other optical components in the apparatus can be safely and reliably protected from the reflected return light.

  In particular, the optical filters 22 and 24 are easy to design and manufacture, and even if they are general-purpose products, the power resistance is considerably large, so that it is possible to easily promote high output of the fiber laser.

  According to the present invention, as described above, all light sources and optical components in the apparatus can be safely and reliably protected against reflected return light from the workpiece W without using an expensive high-power optical isolator. Since it can be protected, the output of the processing light beam LB can be made as high as possible, and high-quality and high-performance laser processing can be realized.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above does not limit this invention. Those skilled in the art can make various modifications and changes in specific embodiments without departing from the technical idea and technical scope of the present invention.

  For example, as shown in FIG. 5, a configuration in which a plurality (for example, two) of active fibers 12 and 42 are cascade-connected can be suitably employed.

  In this case, the optical coupler 44 provided between the first active fiber 12 and the second active fiber 42 includes a plurality of input ports 44IN (1), 44IN (2), 44IN (3),. And one output port 44OUT. The output end of the first active fiber 12 is connected to the first input port 44IN (1) via the optical isolator 21. An excitation LD 46 for exciting the core of the active fiber 42 is connected to the second and third and subsequent input ports 44N (2), 20IN (3),. The input port of the second active fiber 42 is connected to the output port 44OUT.

  The total gain of such a multistage amplifier is the sum of the gain of the first active fiber 12 (first stage amplifier) and the gain of the second active fiber 42 (second stage amplifier). Therefore, even if the output of the seed LD 26 is lowered to, for example, 300 mW or less, the seed light can be amplified and converted into a required high output light beam without difficulty in a stepwise manner. Also in this case, the reflected light is reliably blocked by the first optical filter 22, the wavelength conversion fiber 14, and the second optical filter 24 provided at the subsequent stage of the second active fiber 42, and the first stage and The light source and optical components of the second stage amplifier can be safely protected.

  Note that the optical isolator 21 provided between the first stage amplifier 12 and the second stage amplifier 42 has a light beam of a first stage amplified pulse having a relatively low peak power (usually 1 kW or less) and its reflected return light. Are incident light in the forward and reverse directions, respectively, so that it can be small and inexpensive.

  As described above, as a result of intensive studies by the inventor of the present invention, the MOPA fiber laser processing apparatus of the above embodiment selects the wavelength of the seed light in the vicinity of 1060 nm as described above. MOPA can select the wavelength of SRS light extracted by the optical filter 24 of No. 2 to 1080 to 1300 nm and adapt the wavelength spectrum characteristic of the SRS light output from the wavelength conversion fiber 14 to the band (1080 to 1300 nm). It was found that the numerical conditions were able to achieve the most efficient and reliable compatibility between countermeasures for reflected return light and high laser output in fiber laser processing. However, other numerical ranges can be selected.

  As the wavelength conversion fiber 14, an inexpensive general silica fiber for optical transmission can be suitably used as described above. However, any non-linear fiber and non-linear power suitable for stimulated Raman scattering can be used. Even a silica fiber can be used.

  The fiber laser processing apparatus of the present invention is not limited to marking processing, and can be used for other laser processing such as drilling, cutting, and welding.

10 Seed light generator 12, 42 Active fiber (amplification optical fiber)
14 Wavelength conversion fiber (wavelength conversion optical fiber)
16 Light Beam Irradiation Unit 20, 44 Optical Coupler 22 First Optical Filter 24 First Optical Filter 26 Seed LD
30, 46 Pump LD

Claims (16)

A seed light generator for generating seed light;
Amplifying for amplification by stimulated emission, having a core added with a rare earth element, putting the seed light from the seed light generating part into the core from the input end, and propagating the seed light toward the output end Optical fiber,
An excitation light source for generating excitation light for exciting the core of the amplification optical fiber;
An optical coupler for optically coupling the seed light generator and the excitation light source to an input end of the amplification optical fiber;
An optically non-linear core is provided, and a light beam having the same wavelength as the seed light output from the amplification optical fiber is introduced as pump light into the core from the input end, and the pump light is directed to the output end. An optical fiber for wavelength conversion that generates stimulated Raman scattered light while propagating
A light beam irradiating unit for condensing and irradiating the workpiece with the stimulated Raman scattering light output from the wavelength conversion optical fiber as a processing laser beam;
A first optical filter provided between the amplification optical fiber and the wavelength conversion optical fiber and transmitting only the wavelength of the seed light;
A MOPA type fiber laser processing apparatus comprising: a second optical filter that is provided between the wavelength conversion optical fiber and the light beam irradiation unit and transmits only the wavelength of the stimulated Raman scattering light. A seed light generator for generating seed light;
A first core to which a rare earth element is added; and the seed light from the seed light generation unit is inserted into the first core from an input end and amplified by stimulated emission while propagating the seed light. 1 optical fiber for amplification;
A first excitation light source that generates first excitation light for exciting the first core of the first amplification optical fiber;
A first optical coupler that optically couples the seed light generator and the first excitation light source to an input end of the first amplification optical fiber;
A second core to which a rare earth element is added; and a first-stage amplified light beam output from an output end of the first amplification optical fiber is inserted into the second core from an input end; A second amplification optical fiber that amplifies by stimulated emission while propagating the first stage amplification light beam;
A second excitation light source for generating second excitation light for exciting the second core of the second amplification optical fiber;
A second optical coupler for optically coupling the output end of the first amplification optical fiber and the second excitation light source to the input end of the second amplification optical fiber;
An optically nonlinear core is provided, and a second stage amplification light beam output from the second amplification optical fiber is input as pump light into the core from the input end, and the pump light is output to the output end. An optical fiber for wavelength conversion that generates stimulated Raman scattered light while propagating toward the
A light beam irradiating unit for condensing and irradiating the workpiece with the stimulated Raman scattering light output from the wavelength conversion optical fiber as a processing laser beam;
A first optical filter that is provided between the second amplification optical fiber and the wavelength conversion optical fiber and transmits only the wavelength of the seed light;
A MOPA type fiber laser processing apparatus comprising: a second optical filter that is provided between the wavelength conversion optical fiber and the light beam irradiation unit and transmits only the wavelength of the stimulated Raman scattering light.   3. The seed light generation unit according to claim 1, wherein the seed light generation unit includes a seed laser diode, and drives the seed laser diode to generate seed light having a center wavelength of a spectrum near 1060 nm. MOPA fiber laser processing equipment.   4. The MOPA fiber laser processing apparatus according to claim 3, wherein a transmission band of the second optical filter is 1080 to 1300 nm.   The MOPA system fiber laser processing apparatus according to any one of claims 1 to 4, wherein the power of the pump light is 10 kW or more.   The MOPA fiber laser processing apparatus according to claim 5, wherein the power of the pump light is 20 kW or more.   The MOPA type fiber laser processing apparatus according to claim 1, wherein the wavelength conversion optical fiber is a silica-based fiber.   The MOPA system fiber laser processing apparatus according to claim 7, wherein the wavelength conversion optical fiber is a pure silica-based fiber not containing an additive.   The MOPA type fiber laser processing apparatus according to claim 1, wherein a core diameter of the wavelength conversion optical fiber is φ20 to 40 μm.   10. The MOPA fiber laser processing apparatus according to claim 1, wherein an overall length of the wavelength conversion optical fiber is 2 to 10 m. Generating seed light having a center wavelength of spectrum near 1060 nm using a laser diode;
Amplifying the seed light by stimulated emission while propagating through the core of the amplification optical fiber together with the excitation light;
Extracting a light beam having the same wavelength as the first seed light from the light output from the amplification optical fiber as a pump light using a first optical filter;
Introducing the pump light into a wavelength conversion optical fiber having an optically nonlinear core, and generating stimulated Raman scattering light in the wavelength conversion optical fiber;
Extracting a wavelength component of 1080 to 1300 nm of the stimulated Raman scattering light as processing laser light from the light output from the wavelength conversion optical fiber using a second optical filter;
A laser processing method comprising: condensing and irradiating a given workpiece with the processing laser beam to perform desired laser processing.   Selecting the core diameter and the total length of the wavelength conversion optical fiber and the output of the pump light so that the spectral characteristics of the stimulated Raman scattering light output from the wavelength conversion optical fiber is suitable for a band of 1080 to 1300 nm; The laser processing method according to claim 11.   The laser processing method according to claim 12, wherein the wavelength conversion optical fiber has a core diameter of φ20 to 40 μm.   The laser processing method according to claim 12 or 13, wherein the wavelength conversion optical fiber has a total length of 2 to 10 m.   The laser processing method according to claim 11, wherein the power of the pump light is 10 kW or more.   The laser processing method according to claim 15, wherein the power of the pump light is 20 kW or more.