JP2018129389A - Fiber laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a fiber laser capable of obtaining a monitor value with higher accuracy than the conventional one. SOLUTION: A fiber laser (1) is arranged on an optical path of output light output from one end surface of a delivery fiber (DF) and a delivery fiber (DF) so that a reflecting surface is not orthogonal to the optical path. The mirror (M), the monitor fiber (MF) whose one end face is arranged on the optical path of the output light reflected by the mirror (M), and the output output from the other end face of the monitor fiber (MF). It is equipped with an output light detector (PD) arranged on the optical path of light. The transmittance of the mirror (M) with respect to the output light is larger than the reflectance of the mirror (M) with respect to the output light. [Selection diagram] Fig. 1

Description

  The present invention relates to a fiber laser. In particular, the present invention relates to a fiber laser capable of monitoring the power of output light.

  In recent years, fiber lasers are widely used in the field of material processing. A fiber laser is a laser device that uses an optical fiber (hereinafter referred to as an “amplifying fiber”) in which a rare earth is added to a core as an amplifying medium, and a continuous oscillation type (resonator type) fiber that continuously outputs laser light. There are lasers and pulse oscillation type (MOPA type) fiber lasers that intermittently output laser light.

  In the fiber laser, in addition to the one that uses laser light as output light, it is caused by stimulated Raman scattering in an optical fiber (hereinafter referred to as “Raman fiber”) that is connected downstream of the fiber laser that uses laser light as output light. Some have Stokes light as output light. In either case, the output light is guided to the vicinity of the object to be processed by a delivery fiber (an optical fiber for guiding the output light), and is transmitted to the object to be processed through a head portion connected to the tip of the delivery fiber. Irradiated.

  By the way, in the fiber laser for processing, it is necessary to monitor the power of output light in order to perform feedback control, abnormality detection, and the like. Examples of a method for monitoring the power of output light include the following methods.

  (1) The output light incident on the delivery fiber is branched into irradiation and monitoring by a coupler inserted near the incident end of the delivery fiber, and the output light for monitoring is detected by a photodetector.

  (2) A part of the output light incident on the delivery fiber is leaked from a bent portion or a fusion point formed near the incident end of the delivery fiber, and the leaked output light is detected by a photodetector.

  (3) The output light emitted from the delivery fiber is branched for irradiation and monitoring by a mirror facing the emission end face of the delivery fiber, and the monitoring output light is detected by a photodetector.

  The method (1) has the following problems. In other words, the detection value obtained by the method (1) does not reflect the path loss in the delivery fiber (particularly the portion ahead of the coupler) and the head portion. For this reason, the monitor value (representing the power of the output light) calculated based on the detection value obtained by the method (1) includes an error corresponding to the path loss. Therefore, with the method (1), it is difficult to obtain an accurate monitor value.

  The method (2) has the following problems. That is, the detection value obtained by the method (2) was generated in the delivery fiber (particularly the bent portion or the portion ahead of the fusion point) and the head portion, similarly to the detection value obtained by the method (1). Path loss is not reflected. Furthermore, in the method (2), it is difficult to maintain the leakage rate of output light at the bending point or fusion point of the delivery fiber at a specified value. For this reason, the monitor value calculated based on the detection value obtained by the method (2) includes an error corresponding to the deviation from the specified value of the leakage rate in addition to the error corresponding to the path loss. Therefore, with the method (2), it is more difficult to obtain a monitor value with high accuracy.

  On the other hand, in the method (3), it is possible to obtain a monitor value that does not include an error corresponding to the path loss. However, in the method (3), since it is necessary to incorporate a photodetector or the like in the head portion, there arises a problem that the structure of the head portion is complicated or the size of the head portion is increased.

  As a technique that may contribute to solving such a problem, there is a laser processing machine described in Patent Document 1. In the laser processing machine described in Patent Document 1, the power of output light is monitored by the method (3). However, in the laser processing machine described in Patent Document 1, the monitor output light branched in the head portion is guided to the monitor device via the monitor fiber (the optical fiber for guiding the monitor output light), A configuration is adopted in which detection is performed by a photodetector built in the monitor device. For this reason, in the laser processing machine described in Patent Document 1, it is not necessary to incorporate a photodetector or the like for detecting output light for monitoring in the head unit.

JP 2007-38226 A (publication date: February 15, 2007)

  However, in the laser processing machine described in Patent Document 1, a mirror having a higher reflectivity for output light than a transmittance for output light is used as a mirror for branching the output light in the head portion. That is, a configuration is adopted in which reflected light having a high power reflected by the mirror is irradiated onto the object to be processed, and the transmitted light having a low power transmitted through the mirror is guided to the monitor fiber.

  For this reason, if there is an error in the mounting angle of the mirror, output light having a large power to be irradiated on the workpiece may propagate in an unexpected direction, and a part of the output light may be irregularly reflected in the head portion. If it does so, while the power of the output light irradiated to a workpiece will fall, a part of diffusely reflected output light will inject into a monitor fiber, and the power of the output light detected with a photodetector will rise. Therefore, the monitor value calculated based on the detection value includes an error corresponding to a decrease due to irregular reflection of the power of the output light irradiated to the workpiece and the power of the output light detected by the photodetector. And an error corresponding to an increase due to irregular reflection. For this reason, the laser processing machine described in Patent Document 1 cannot obtain a monitor value with high accuracy.

  The present invention has been made in view of the above problems, and an object of the present invention is to realize a fiber laser capable of obtaining a monitor value with higher accuracy than before.

  In order to achieve the above object, a fiber laser according to the present invention is arranged on a delivery fiber and an optical path of output light output from one end face of the delivery fiber so that a reflection surface is not orthogonal to the optical path. A mirror having a greater transmittance with respect to the output light than a reflectance with respect to the output light, and a monitor fiber disposed on an optical path of the output light having one end surface reflected by the mirror. An output light detector disposed on the optical path of the output light output from the other end face of the monitor fiber.

  As described above, in the fiber laser according to the present invention, a mirror having a higher transmittance for output light than a reflectance for output light is used as a mirror for branching the output light. That is, a configuration is adopted in which transmitted light having a high power transmitted through the mirror is irradiated onto the object to be processed and reflected light having a low power reflected by the mirror is guided to the monitor fiber.

  For this reason, even if there is a deviation in the mounting angle of the mirror, it is difficult to cause a situation in which output light with high power to be irradiated on the object to be processed is irregularly reflected by the casing of the head unit or the like. Therefore, an error corresponding to a decrease due to irregular reflection of the power of the output light irradiated to the workpiece that can be included in the monitor value calculated based on the detection value obtained by the output light detector, and An error corresponding to an increase due to irregular reflection of the power of output light incident on the output light detector can be reduced. Therefore, according to the present invention, it is possible to obtain a monitor value with higher accuracy than the laser processing machine described in Patent Document 1.

  The fiber laser according to the present invention further includes a section including the one end face of the delivery fiber, a section including the one end face of the monitor fiber, and a head portion for storing the mirror, and the output light detection The vessel is preferably arranged outside the head portion.

  According to said structure, laser processing can be easily implement | achieved by handling the said head part. In addition, since the output light detector is disposed outside the head unit, it is possible to prevent the structure of the head unit from becoming complicated and the size of the head unit from increasing.

  In the fiber laser according to the present invention, it is preferable that the delivery fiber and the monitor fiber are bundled with a coating material and constitute a single cable having one end connected to the head portion.

  According to said structure, when handling the said head part, handling of the said delivery fiber and the said monitor fiber can be made easy. Further, the delivery fiber and the monitor fiber can be made difficult to be damaged.

  The fiber laser according to the present invention includes an amplification fiber directly or indirectly connected to the other end face of the delivery fiber, and a monitor representing the power of the output light from the detection value obtained by the output light detector. A main body that stores a control unit that calculates a value, a section that includes the other end face of the amplification fiber, the delivery fiber, a section that includes the other end face of the monitor fiber, the output light detector, and the control section It is preferable that the other end of the cable is connected to the main body.

  According to said structure, the said fiber laser can be made into the structure which consists of the said main-body part, the said head part, and the said cable and is easy to handle. In addition, since the output light detector and the control unit are built in the main body, wiring and a circuit for connecting the output light detector and the control unit can be simplified. .

  In the fiber laser according to the present invention, the one end surface of the monitor fiber is opposed to the reflection surface of the mirror, and the output light reflected by the mirror is transmitted through the one end surface. It is preferable to enter the monitor fiber.

  According to the above configuration, the optical system for branching the output light for irradiation and for monitoring can be configured by the output end of the delivery fiber, the input end of the monitor fiber, and a single mirror. it can. Therefore, the optical system can be manufactured easily and inexpensively.

  The fiber laser according to the present invention further includes another mirror disposed so that a reflection surface thereof faces the reflection surface of the mirror, and the output light reflected by the mirror is the other mirror. It is preferable that the light is incident on the monitor fiber through the one end face after being further reflected.

  According to said structure, the optical axis direction in the incident end of the said monitor fiber can be made parallel or substantially parallel with the optical axis direction in the output end of the said delivery fiber. Therefore, an optical system for branching the output light for irradiation and for monitoring can be realized in a small size.

  The fiber laser according to the present invention has a return light monitoring fiber arranged on the return light path reflected by the mirror on one end face, or on the return light path reflected by the mirror on the light receiving surface. It is preferable that the apparatus further comprises a return light detector disposed in the.

  According to said structure, in addition to the function to monitor the power of output light, the fiber laser which has the function to monitor the power of the power of return light is realizable.

  A fiber laser according to the present invention outputs scattered light of stimulated Raman scattering as the output light and outputs scattered light of stimulated Raman scattering as unnecessary light, and the mirror is subjected to the stimulated Raman scattering. It is preferable that the reflectance with respect to scattered light is higher than the transmittance with respect to the scattered light.

  According to the above configuration, in the fiber laser that uses the scattered light (Stokes light) of stimulated Raman scattering as the output light, a monitor value with higher accuracy than before can be obtained.

  The fiber laser according to the present invention outputs scattered light of stimulated Raman scattering as the output light and outputs scattered light of stimulated Raman scattering as unnecessary light, and the scattered light for detecting the scattered light. A wavelength demultiplexer disposed on an optical path of the output light from the mirror to the light detector, guiding the scattered light to the output light detector, and passing the scattered light to the light detector. It is preferable to further include a wavelength demultiplexer that leads to the scattered light detector.

  According to the above configuration, in the fiber laser that uses the scattered light (Stokes light) of stimulated Raman scattering as the output light, a monitor value with higher accuracy than before can be obtained. Moreover, the power of the scattered light contained in the output light and the power of the scattered light (residual laser light) contained in the output light can be individually monitored.

  According to the present invention, it is possible to obtain a monitor value with higher accuracy than before in a fiber laser.

It is a block diagram which shows the structure of the fiber laser which concerns on the 1st Embodiment of this invention. (A) is a block diagram which shows the structure of the head part with which the fiber laser of FIG. 1 is equipped, (b) is a block diagram which shows the 1st modification, (c) is the 2nd It is a block diagram which shows a modification. It is a block diagram which shows the structure of the fiber laser which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the fiber laser which concerns on the 3rd Embodiment of this invention.

<Embodiment 1>
[Configuration of fiber laser]
The configuration of the fiber laser 1 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the configuration of the fiber laser 1.

  The fiber laser 1 is a fiber laser that uses laser light as output light, and includes a main body B, a head H, and a cable C as shown in FIG.

  The main body portion B includes a plurality of laser diodes LD1 to LDm, a pump combiner PC, a first fiber Bragg grating FBG1, an amplification fiber AF, a second fiber Bragg grating FBG2, and an entrance end of the delivery fiber DF (section including the entrance end face). ) Is stored. Although FIG. 1 illustrates the configuration in the case of m = 6, the number m of the laser diodes LD1 to LDm is arbitrary.

  Each laser diode LDj is configured to generate pump light (j = 1, 2,..., M). Pump light generated by each laser diode LDj is input to the pump combiner PC.

  The pump combiner PC is configured to obtain combined pump light by combining pump light generated by each of the laser diodes LD1 to LDm. The combined pump light obtained by the pump combiner PC is input to the amplification fiber AF via the first fiber Bragg grating FBG1.

  The amplification fiber AF has a configuration for converting the combined pump light obtained by the pump combiner PC into laser light. In the present embodiment, a double clad fiber in which a rare earth element such as Yb is added to the core is used as the amplification fiber AF. The synthetic pump light obtained by the pump combiner PC is used for maintaining the rare earth element in an inverted distribution state.

  A first fiber Bragg grating FBG1 that functions as a mirror at a specific wavelength λ is connected to the input end of the amplification fiber AF, and a first mirror that functions as a half mirror at the specific wavelength λ is connected to the output end of the amplification fiber AF. A two-fiber Bragg grating FBG2 is connected. That is, the amplification fiber AF constitutes a resonator together with the first fiber Bragg grating FBG1 and the second fiber Bragg grating FBG2. In the core of the amplification fiber AF, the rare-earth element maintained in the inversion distribution state repeats stimulated emission, so that the laser beam having the specific wavelength λ is recursively amplified. Of the laser light recursively amplified by the amplification fiber AF, the laser light transmitted through the second fiber Bragg grating FBG2 is input to the delivery fiber DF.

  The head portion H includes an output end (a section including the output end surface) of the delivery fiber DF, a first fiber coupling unit FC1, a mirror M, a second fiber coupling unit FC2, and an incident end (incident end surface) of the monitor fiber MF. Is stored).

  The first fiber coupling unit FC1 is configured to fix the optical axis position and the optical axis direction at the emission end of the delivery fiber DF so that the laser light output from the delivery fiber DF enters the mirror M. In the present embodiment, a fiber positioner is used as the first fiber coupling unit FC1. The first fiber coupling unit FC1 includes a lens for collimating the laser beam output from the delivery fiber DF, in addition to a mechanism for fixing the optical axis position and the optical axis direction at the emission end of the delivery fiber DF. An optical element may be provided. Further, instead of fixing the delivery fiber DF using a fiber positioner, after passing the delivery fiber DF through the glass ferrule that passes through the housing of the head portion H, the configuration in which the delivery fiber DF is bonded to the glass ferrule, A configuration in which the delivery fiber is passed through a metal coated ferrule that penetrates the housing of the head portion H and then the delivery fiber DF is YAG welded to the metal coated ferrule may be employed.

  The mirror M has a configuration for branching the laser beam output from the delivery fiber DF into an irradiation unit and a monitoring unit. The mirror M is arranged on the optical path of the laser beam output from the delivery fiber DF so that the reflection surface thereof is not orthogonal to the optical path of the laser beam. In the mirror M, the transmittance with respect to the laser light as the output light is set higher than the reflectance with respect to the laser light. For this reason, the power of the irradiation laser light transmitted through the mirror M is larger than the power of the monitoring laser light reflected by the mirror M.

  The second fiber coupling unit FC2 is configured to fix the optical axis position and the optical axis direction at the incident end of the monitor fiber MF so that the monitor laser beam reflected by the mirror M enters the monitor fiber MF. It is. In the present embodiment, a fiber positioner is used as the second fiber coupling unit FC2. The second fiber coupling unit FC2 collects the monitoring laser light reflected by the mirror M in addition to the mechanism for fixing the optical axis position and the optical axis direction at the incident end of the monitor fiber MF. An optical element such as a lens may be provided. Further, instead of fixing the monitor fiber MF using a fiber positioner, the monitor fiber MF is passed through a glass ferrule that passes through the housing of the head portion H, and then the monitor fiber MF is bonded to the glass ferrule. A configuration in which the monitor fiber MF is passed through a metal coated ferrule that passes through the housing of the head portion H and then the monitor fiber MF is YAG welded to the metal coated ferrule may be employed.

  The cable C includes a delivery fiber DF, a monitor fiber MF, and a covering material (for example, a SUS pipe) for bundling them. One end is connected to the main body B and the other end is connected to the head H. ing. The delivery fiber DF is an optical fiber for guiding the laser beam generated in the main body part B to the head part H, and its input end and output end are drawn into the main body part B and the head part H, respectively. The monitor fiber MF is an optical fiber for guiding the monitoring laser beam branched in the head part H to the main part B, and its input end and output end are drawn into the head part H and the main part B, respectively. ing.

  The main body B further stores an emission end (section including the emission end face) of the monitor fiber MF, a photodetector (output photodetector) PD, and a control unit CU. The monitoring laser beam branched at the head portion H and guided from the head portion H to the main body portion B by the monitor fiber MF is input to the photodetector PD. The photodetector PD is configured to convert the monitoring laser light into an electric signal representing the power. The electrical signal obtained by the photodetector PD is input to the control unit CU. The control unit CU calculates a monitor value representing the power of the laser beam for irradiation based on the electrical signal obtained by the photodetector PD, and feedback control and abnormality detection based on the calculated monitor value. I do.

  As described above, in the fiber laser 1 according to the present embodiment, the laser light that is the output light is used for irradiation with the laser light having a high power that has passed through the mirror M, and the laser that has been reflected by the mirror M has a low power. A configuration in which light is used for monitoring is employed. For this reason, even if there is a deviation in the mounting angle of the mirror M, the laser beam for irradiation with high power is irregularly reflected in the head part H, or the laser light irregularly reflected in the head part H It is difficult for the incident to the detector PD to occur. Therefore, an error corresponding to a decrease due to irregular reflection of the power of the output light irradiated to the workpiece that can be included in the monitor value calculated based on the electrical signal obtained by the photodetector PD, and the light An error corresponding to an increase due to irregular reflection of the power of the output light detected by the detector PD can be reduced. Therefore, according to the fiber laser 1 according to the present embodiment, a highly accurate monitor value can be obtained as a monitor value representing the power of the laser beam irradiated to the workpiece.

  In addition, in this embodiment, although the structure which arrange | positions photodetector PD in the main-body part B is employ | adopted, this invention is not limited to this. That is, you may employ | adopt the structure which arrange | positions photodetector PD outside the main-body part B. FIG.

[Modification of head part]
A modification of the head portion H provided in the fiber laser 1 will be described with reference to FIG. 2, (a) is a block diagram showing the configuration of the head portion H included in the fiber laser 1, and (b) and (c) are block diagrams showing modifications thereof.

  In this embodiment, as shown in FIG. 2A, an optical system for branching the laser beam output from the delivery fiber DF for irradiation and for monitoring has a reflecting surface that emits the delivery fiber DF. It is composed of a single mirror M facing both the end face and the incident end face of the monitor fiber MF. However, the configuration of the optical system for branching the laser beam output from the delivery fiber DF for irradiation and for monitoring is not limited to this.

  For example, as shown in FIG. 2B, an optical system for branching the laser beam output from the delivery fiber DF for irradiation and for monitoring has a reflecting surface facing the emission end face of the delivery fiber DF. The first mirror M1 and the second mirror M2 whose reflecting surface faces the reflecting surface of the first mirror M1 can be configured. Specifically, in accordance with the example shown in FIG. 2B, the first mirror M1 includes a reflection surface, an optical path of the laser light, and an optical path of the laser light output from the delivery fiber DF. Is arranged such that the angle formed by the laser beam is 45 °, and in the illustrated coordinate system, the traveling direction of the laser beam is converted from the positive x-axis direction to the negative y-axis direction. The second mirror M2 is arranged on the optical path of the laser light reflected by the first mirror M1 so that the angle formed by the reflection surface and the optical path of the laser light is 45 °, and the coordinates shown in the figure. In the system, the traveling direction of the laser beam is changed from the negative y-axis direction to the negative x-axis direction. The delivery fiber DF and the monitor fiber MF are fixed by the fiber coupling unit FC1 and the fiber coupling unit FC2 in the illustrated coordinate system so that the emission end surface and the incident end surface are directed in the positive x-axis direction, respectively. That is, the exit end of the delivery fiber DF and the entrance end of the monitor fiber MF are arranged in parallel to each other.

  When the configuration shown in FIG. 2A is adopted as an optical system for branching the laser beam output from the delivery fiber DF into the irradiation and the monitoring, the optical system is configured by a single mirror M. Therefore, there is an advantage that the head portion H can be manufactured easily and inexpensively. On the other hand, when the configuration shown in FIG. 2B is adopted as the optical system for branching the laser beam output from the delivery fiber DF into the irradiation and the monitoring, the output end of the delivery fiber DF and the monitor fiber Since the MF incident ends are arranged in parallel to each other, there is an advantage that the head portion H can be realized in a small size. Note that one or more mirrors may be further provided in the optical path of the laser light reflected by the mirror M2, and the laser light may be guided to the incident end of the monitor fiber MF by these mirrors.

  Further, when it is necessary to monitor the power of the return light reflected from the object to be processed and re-entered into the head portion H from the outside of the head portion H, the configuration shown in FIG. May be. The configuration shown in (c) of FIG. 2 is the same as the configuration shown in (a) of FIG. 2, (1) after being re-entered from the outside of the head portion H into the head portion H and then reflected by the mirror M. Return light monitor fiber MF2 for guiding light from head part H to main part B, and (2) incidence of return light monitor fiber MF2 so that the return light reflected by mirror M is incident on return light monitor fiber MF2. A fiber coupling portion FC3 for fixing the optical axis position and the optical axis direction at the end is added. The return light guided from the head part H to the main part B by the return light monitor fiber MF2 is converted into an electrical signal by a return light detector (not shown in FIG. 1) built in the main part B, for example. When the configuration shown in FIG. 2C is adopted, the fiber laser 1 can have a function of monitoring the power of the return light in addition to the function of monitoring the power of the output light.

  The return light reflected by the mirror M is converted into an electric signal by a return light detector built in the head portion H, and the obtained electric signal is converted from the head portion H to the main body portion B using a metal cable. A configuration leading to the above may be adopted. Even when such a configuration is adopted, the fiber laser 1 can be provided with a function of monitoring the power of the return light.

  In addition, although the modified example of the head part H with which the fiber laser 1 which concerns on 1st Embodiment mentioned above is provided was demonstrated here, these modified examples are the fiber laser 2 which concerns on 2nd Embodiment mentioned later. The present invention can be applied to the head portion H provided to the head portion H provided in the fiber laser 3 according to the third embodiment to be described later.

<Embodiment 2>
The configuration of the fiber laser 2 according to the second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram showing the configuration of the fiber laser 2.

  The fiber laser 2 is a fiber laser that uses Stokes light as output light, and a Raman fiber RF is inserted between the second fiber Bragg grating FBG2 and the delivery fiber DF of the fiber laser 1 shown in FIG.

  The Raman fiber RF is an optical fiber for converting laser light (scattered light of stimulated Raman scattering) recursively amplified by the amplification fiber AF into Stokes light (scattered light of stimulated Raman scattering) by stimulated Raman scattering. It is. Since the wavelength of the Stokes light that is the scattered light is longer than the wavelength of the laser light that is the scattered light, the Raman fiber RF functions as a wavelength conversion element (Raman shifter). From the Raman fiber RF, Stokes light (illustrated by black triangles in FIG. 3) as output light and residual laser light (illustrated by white triangles in FIG. 3) as unnecessary light are output.

  Also in the present embodiment, the mirror M is used as a configuration for branching the Stokes light and the residual laser light output from the delivery fiber DF for irradiation and for monitoring. The mirror M is arranged on the optical path of the Stokes light and the residual laser light output from the delivery fiber DF so that the reflection surface thereof is not orthogonal to the optical path of the Stokes light and the residual laser light.

  In the mirror M, the transmittance with respect to the Stokes light as the output light is set higher than the reflectance with respect to the Stokes light. For this reason, the power of the Stokes light for irradiation transmitted through the mirror M becomes larger than the power of the Stokes light for monitoring reflected by the mirror M. For example, the mirror M can be configured to transmit substantially all of the Stokes light that is the output light. In this case, the power of the Stokes light for irradiation is substantially the same as the power of the Stokes light output from the delivery fiber DF, and the power of the Stokes light for monitoring is substantially zero.

  On the other hand, in the mirror M, the reflectance with respect to the residual laser light which is unnecessary light is set higher than the transmittance with respect to the residual laser light. For this reason, the power of the residual laser light for monitoring reflected by the mirror M becomes larger than the power of the residual laser light for irradiation transmitted through the mirror M. For example, the mirror M can be configured to reflect substantially all of the laser light that is unnecessary light. In this case, the power of the residual laser light for monitoring is substantially the same as the power of the residual laser light output from the delivery fiber DF, and the power of the residual laser light for irradiation is substantially zero.

  The photodetector PD receives the residual laser light for monitoring or the mixed light in which the residual laser light for monitoring and the Stokes light for monitoring are mixed at a certain ratio. The photodetector PD converts the residual laser light for monitoring or the mixed light in which the residual laser light for monitoring and the Stokes light for monitoring are mixed at a constant ratio into an electric signal representing the power. There is a given correlation between the power of the residual laser light for monitoring and the power of the Stokes light for irradiation. Similarly, there is a given correlation between the power of the mixed light in which the residual laser light for monitoring and the Stokes light for monitoring are mixed at a certain ratio and the power of the Stokes light for irradiation. Therefore, the control unit CU built in the main body B can calculate the power of the Stokes light applied to the object to be processed from the value of the electrical signal obtained by the photodetector PD.

  As described above, also in the fiber laser 2 according to the present embodiment, with respect to the Stokes light as the output light, the Stokes light having a large power transmitted through the mirror M is used for irradiation, and the Stokes having a small power reflected by the mirror M is used. A configuration in which light is used for monitoring is employed. For this reason, as with the fiber laser 1 according to the first embodiment, a highly accurate monitor value can be obtained as a monitor value representing the power of the Stokes light irradiated onto the workpiece.

  Further, in the fiber laser 2 according to the present embodiment, with respect to the residual laser light that is unnecessary light, the residual laser light having a low power transmitted through the mirror M is used for irradiation, and the residual laser light having a high power reflected by the mirror M is used for irradiation. A configuration for monitoring is adopted. For this reason, while the power of the residual laser light irradiated to a workpiece can be made small enough, the power of the residual laser light inputted into photodetector PD can be made large enough.

<Embodiment 3>
The configuration of the fiber laser 3 according to the third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a block diagram showing the configuration of the fiber laser 3.

  The fiber laser 3 is a fiber laser that uses Stokes light as output light, in which a Raman fiber RF is inserted between the second fiber Bragg grating FBG2 and the delivery fiber DF of the fiber laser 1 according to the first embodiment. It is. The fiber laser 2 according to the second embodiment employs a configuration in which the mixed light of the Stokes light and the residual laser light output from the delivery fiber DF is guided to the photodetector PD. In the fiber laser 3, the mixed light output from the delivery fiber DF is demultiplexed into Stokes light and residual laser light by the wavelength demultiplexer WDM, and the Stokes light is detected by the first photodetector PD1 (scattered light detection). And a structure in which the residual laser light is guided to the second photodetector PD2 (scattered light detector).

  Also in the present embodiment, the mirror M is used as a configuration for branching the Stokes light and the residual laser light output from the delivery fiber DF for irradiation and for monitoring. The mirror M is arranged on the optical path of the Stokes light and the residual laser light output from the delivery fiber DF so that the reflection surface thereof is not orthogonal to the optical path of the Stokes light and the residual laser light.

  In the mirror M, the transmittance with respect to the Stokes light as the output light is set higher than the reflectance with respect to the Stokes light. For this reason, the power of the Stokes light for irradiation transmitted through the mirror M becomes larger than the power of the Stokes light for monitoring reflected by the mirror M. For example, the mirror M can be configured to transmit substantially all of the Stokes light that is the output light. In this case, the power of the Stokes light for irradiation is substantially the same as the power of the Stokes light output from the delivery fiber DF, and the power of the Stokes light for monitoring is substantially zero.

  On the other hand, in the mirror M, the reflectance with respect to the residual laser light which is unnecessary light is set higher than the transmittance with respect to the residual laser light. For this reason, the power of the residual laser light for monitoring reflected by the mirror M becomes larger than the power of the residual laser light for irradiation transmitted through the mirror M. For example, the mirror M can be configured to reflect substantially all of the laser light that is unnecessary light. In this case, the power of the residual laser light for monitoring is substantially the same as the power of the residual laser light output from the delivery fiber DF, and the power of the residual laser light for irradiation is substantially zero.

  Stokes light for monitoring is input to the first photodetector PD1. The first photodetector PD1 converts the Stokes light for monitoring into an electric signal representing the power. On the other hand, residual laser light for monitoring is input to the second photodetector PD2. The second photodetector PD2 converts the monitoring laser light into an electrical signal representing its power. There is a given correlation between the power of the Stokes light for monitoring and the power of the Stokes light for irradiation. Similarly, there is a given correlation between the power of the residual laser light for monitoring and the power of the residual laser light for irradiation. Therefore, the control unit CU built in the main body B is configured to detect the Stokes light emitted to the object to be processed and the values of the electrical signals obtained by the first photodetector PD1 and the second photodetector PD2, respectively. The power of the residual laser beam can be calculated individually.

  As described above, also in the fiber laser 3 according to the present embodiment, with respect to the Stokes light that is the output light, the Stokes light having a large power transmitted through the mirror M is used for irradiation and the Stokes having a small power reflected by the mirror M is used. A configuration in which light is used for monitoring is employed. For this reason, as with the fiber laser 1 according to the first embodiment, a highly accurate monitor value can be obtained as a monitor value representing the power of the Stokes light irradiated onto the workpiece.

  Further, in the fiber laser 3 according to the present embodiment, with respect to the residual laser light that is unnecessary light, the residual laser light having a small power transmitted through the mirror M is used for irradiation, and the residual laser light having a high power reflected by the mirror M is used for irradiation. A configuration for monitoring is adopted. For this reason, while the power of the residual laser light irradiated to a workpiece can be made small enough, the power of the residual laser light inputted into photodetector PD can be made large enough.

<Additional notes>
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

1, 2, 3 Fiber laser B Main body part LD1, LD2, ..., LDm Laser diode PC Pump combiner AF Amplifying fiber FBG1, FBG2 Fiber Bragg grating PD, PD1, PD2 Photodetector H Head part FC1, FC2 Fiber coupling part M , M1, M2 Mirror C Cable DF Delivery fiber MF Monitor fiber

Claims (9)

Delivery fiber,
The mirror is arranged on the optical path of the output light output from one end face of the delivery fiber so that the reflection surface is not orthogonal to the optical path, and the transmittance for the output light is higher than the reflectance for the output light. With a big mirror,
A monitor fiber disposed on an optical path of the output light, one end face of which is reflected by the mirror;
An output light detector disposed on the optical path of the output light output from the other end face of the monitor fiber,
A fiber laser characterized by that. A section including the one end face of the delivery fiber, a section including the one end face of the monitor fiber, and a head portion for storing the mirror;
The output light detector is disposed outside the head unit,
The fiber laser according to claim 1. The delivery fiber and the monitor fiber are bundled with a coating material, and constitute a single cable with one end connected to the head part.
The fiber laser according to claim 2. An amplification fiber connected directly or indirectly to the other end face of the delivery fiber;
A control unit that calculates a monitor value representing the power of the output light from the detection value obtained by the output light detector;
A section including the other end face of the amplification fiber, a section including the other end face of the monitor fiber, a main body for storing the output light detector, and the control section; ,
The other end of the cable is connected to the main body.
The fiber laser according to claim 3. The one end surface of the monitor fiber is opposed to the reflecting surface of the mirror,
The output light reflected by the mirror is incident on the monitor fiber through the one end face.
The fiber laser according to any one of claims 1 to 4, wherein: And further comprising another mirror disposed so that the reflecting surface faces the reflecting surface of the mirror,
The output light reflected by the mirror is further reflected by the other mirror, and then enters the monitor fiber through the one end face.
The fiber laser according to any one of claims 1 to 4, wherein: A return light monitoring fiber having one end face disposed on the optical path of the return light reflected by the mirror, or a return light detector having a light receiving surface disposed on the optical path of the return light reflected by the mirror. Further comprising
The fiber laser according to any one of claims 1 to 6, wherein: The fiber laser outputs scattered light of stimulated Raman scattering as the output light and outputs scattered light of stimulated Raman scattering as unnecessary light.
The mirror has a higher reflectance to the scattered light of the stimulated Raman scattering than the transmittance to the scattered light,
The fiber laser according to any one of claims 1 to 7, characterized in that The fiber laser outputs scattered light of stimulated Raman scattering as the output light and outputs scattered light of stimulated Raman scattering as unnecessary light.
The fiber laser includes a scattered light detector for detecting the scattered light, and a wavelength demultiplexer disposed on an optical path of the output light from the mirror to the output light detector, And a wavelength demultiplexer for guiding the scattered light to the scattered light detector.
The fiber laser according to any one of claims 1 to 7, characterized in that

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