JP2012114299A - Fiber laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber laser device in which output of unnecessary light can be minimized while shortening the start-up period of laser light to be output.SOLUTION: The fiber laser device 100 comprises a seed laser light source 10, an excitation light source 20, an optical fiber 30 for amplification, a control unit 60, and an instruction unit 65. The seed laser light source 10 and the excitation light source 20 are brought into the output state after a predetermined period of time after an output instruction is input to the control unit 60, and the output state is terminated after the predetermined period of time after an output stop instruction is input to the control unit 60. A preliminary excitation state is brought about after termination of an output state before start of next output state if the period after input of an output stop instruction before next output instruction is shorter than the predetermined period of time. The preliminary excitation state is brought about only during a specified period after input of an output instruction if the period after input of an output stop instruction before the output instruction is longer than the predetermined period of time.

Description

  The present invention relates to a fiber laser device.

  In recent years, fiber laser devices have been used in processing machines that perform processing using laser light and medical equipment such as a scalpel using laser light. In the fiber laser device, laser light and excitation light generated by a laser oscillator are input to an amplification optical fiber, and the amplified laser light is output from an output unit.

  In such a fiber laser device, it takes a certain period of time until the intensity of the laser beam is stabilized after the laser beam starts to be output from the fiber laser device. That is, a certain period is required for the rise of the laser light.

  The shorter the rise time of the laser light, the better the work efficiency. Patent Document 1 listed below describes a fiber laser device in which the period until the intensity of such laser light is stabilized is short.

  In the fiber laser device described in Patent Document 1 below, in a period other than the time when laser light is output from the fiber laser device, a constant intensity of weak excitation light is input to the amplification optical fiber and added to the amplification optical fiber. The rare earth element is excited. That is, preliminary excitation is performed in a period other than when the laser beam is output from the fiber laser device. Next, when the laser beam is output from the fiber laser device, the seed laser beam and the strong excitation light are input to the amplification optical fiber, and the amplified laser beam is output. In this way, when the laser beam is output from the fiber laser device, the rare-earth element of the amplification optical fiber is excited by pre-excitation, so that the rise period of the laser beam output from the fiber laser device is short. (Patent Document 1).

JP 2008-91773 A

  However, although the fiber laser device described in Patent Document 1 has a short rise time of the laser beam, it oscillates if the excited state of the rare earth element of the amplification optical fiber becomes too high during the preliminary excitation period, and the spire There was a case where unnecessary light having a high value was output. When such unnecessary light with a high spire value is output, the workpiece or the like to which the laser beam is irradiated may be irradiated with unnecessary high-intensity laser light and the workpiece or the like may be damaged.

  Therefore, the present invention provides a fiber laser device that can suppress the output of unnecessary light having a high spire value during a period other than the period in which the laser beam is output, while shortening the rising period of the output laser beam. With the goal.

  The fiber laser device of the present invention receives a seed laser light source that outputs seed laser light, an excitation light source that outputs pump light, the seed laser light and the pump light, and is excited by the pump light. A rare-earth element added, an amplification optical fiber for amplifying the seed laser light to output laser light, an output unit for outputting the laser light output from the amplification optical fiber, and at least the seed laser light source; A control unit for controlling the excitation light source, an output command for outputting the laser beam from the output unit, and a command for inputting an output stop command for stopping the output of the laser beam from the output unit to the control unit The seed laser light source and the excitation light source are in an output state after a predetermined period after the output command is input to the control unit, and the output stop command is The output state is terminated after a certain period of time after being input to the control unit, and the period from when the output stop command is input to the control unit to when the output command is next input to the control unit is If it is shorter than the predetermined period, it is in a pre-excitation state from the end of the output state to the next output state, and after the output stop command is input to the control unit, the output command is When the period until the command is input to the control unit is longer than the predetermined period, it is stopped from the end of the output state until the next output command is input to the control unit. At the same time, from the time when the output command is input to the control unit to the next output state, the preliminary excitation state is set, and in the preliminary excitation state, the seed laser light is input to the amplification optical fiber. Not The seed laser light is input to the amplification optical fiber so that the electromotive force is input to the amplification optical fiber with a predetermined intensity and, in the output state, the laser light is output from the output unit. In addition, the pumping light is input to the amplification optical fiber, and the predetermined intensity of the pumping light is input to the amplification optical fiber in the preliminary pumping state for a certain period of time, so that the resonator of the fiber laser device This is characterized in that the period is shorter than the period in which the gain is positive.

  According to such a fiber laser device, since the excitation light having a predetermined intensity is input to the amplification optical fiber before the output state is set, the rising period of the laser light can be shortened, and The period of this pre-pumping state is shorter than the period in which the pump light of the predetermined intensity is input to the amplifying optical fiber and the gain of the resonator of the fiber laser apparatus is positive, so that the fiber laser apparatus oscillates. Can be prevented. For this reason, it is possible to suppress the output of unnecessary light having a high spire value outside the period in which the laser light is output.

  In addition, when the period from the output stop command to the next output command is longer than the above-mentioned fixed period, the seed laser light source and the excitation light source are in the pre-excitation state only for a fixed period from the input of the output command to the output state. It is said. That is, the seed laser light source and the excitation light source are stopped and not in the preliminary excitation state during the period from the end of the output state before the output command is input until the output command is input. The pre-excitation state is set only for a certain period of time after the input. The predetermined period of time in the preliminary excitation state is shorter than the period in which the pump light in the preliminary excitation state is input to the amplification optical fiber and the gain of the resonator of the fiber laser device is positive. . In this way, by setting the seed laser light source and the excitation light source in the preliminary excitation state for a certain period, the rising period of the laser light in the output state can be shortened. Furthermore, since the gain of the resonator of the fiber laser device does not become positive in the pre-pumped state, unintentional oscillation can be suppressed and output of unnecessary light having a high spire value can be suppressed. On the other hand, if the period from the output stop command to the next output command is shorter than the above-mentioned fixed period, the seed laser light source and the excitation light source are spared between the end time of the output state and the start time of the next output state. Excited state. Thus, even when the interval between output states is short, the rise of the laser beam in the output state can be accelerated by performing preliminary excitation during that interval. Thus, according to the fiber laser device of the present invention, it is possible to suppress the output of unnecessary light having a high spire value during a period other than the period in which the laser beam is output, while shortening the rising period of the output laser beam. it can.

  In the fiber laser device, the wavelength of the light generated and output from the amplification optical fiber by the excitation light in the preliminary excitation state is provided between the amplification optical fiber and the output unit. The wavelength converter that converts the wavelength of the laser light output from the amplification optical fiber by the seed laser light and the excitation light in the output state, and is provided between the wavelength converter and the output unit. When light having the same wavelength band as that of the seed laser light is input to the wavelength converter, light that is wavelength-converted by the wavelength converter is transmitted, and transmission of light that is not wavelength-converted by the wavelength converter is suppressed. It is preferable to further include a wavelength selection filter.

  The wavelength converter is composed of, for example, an optical fiber that causes stimulated Raman scattering. This wavelength converter converts incident light into light having a longer wavelength when the spire value of incident light intensity is large and outputs it, and does not convert the wavelength of incident light when the spire value of incident light intensity is small. Output as is. According to such a fiber laser device, when the amplified laser light is output from the amplification optical fiber in the output state, the laser light has a high spire value, and is therefore wavelength-converted by the wavelength converter. Accordingly, the wavelength-converted laser light passes through the wavelength selection filter and is output from the output unit. On the other hand, in the pre-pumped state, the rare earth element of the amplification optical fiber is excited by the pumping light, but the seed laser light is not input to the amplification optical fiber. ASE (Amplified Spontaneous Emission) in which spontaneous emission light emitted from the element is amplified is output. Since the spontaneous emission light has a wide spectrum and the intensity of the spire value is small, even if this ASE is input from the amplification optical fiber, the input light is not wavelength-converted in the wavelength converter. For this reason, even when ASE is output from the amplification optical fiber, transmission of light output from the wavelength converter and input to the wavelength selection filter is suppressed in the wavelength selection filter. Thus, it is possible to suppress unnecessary light from being output from the output unit in the preliminary excitation state.

  Alternatively, the fiber laser device of the present invention includes a seed laser light source that outputs seed laser light, an excitation light source that outputs excitation light, the seed laser light and the excitation light, and is excited by the excitation light. An amplification optical fiber to which the rare earth element is added and amplifies the seed laser light to output the laser light, an output unit to output the laser light output from the amplification optical fiber, and at least the seed laser A control unit for controlling the light source and the excitation light source, an output command for outputting the laser beam from the output unit, and an output stop command for stopping the output of the laser beam from the output unit are input to the control unit The seed laser light source and the excitation light source are in an output state after a predetermined period after the output command is input to the control unit, and the output stop After the command is input to the control unit, the output state is terminated after the predetermined period, and from when the output stop command is input to the control unit until the next output command is input to the control unit. When the period is shorter than the predetermined period, the preliminary excitation state is set from the end of the output state to the next output state, and the output stop command is input to the control unit and then the When the period until the output command is input to the control unit is longer than the predetermined period, the output state is stopped from the end of the output state until the next time the output command is input to the control unit. In addition, during the period from when the output command is input to the control unit until the next output state is reached, the pre-excitation state is set, and in the pre-excitation state, the seed laser light having a small spire value is used for the amplification. Enter optical fiber At the same time, the seed laser beam is input to the amplification optical fiber with a predetermined intensity, and in the output state, the seed laser beam is output from the output unit so that the seed laser beam is output from the output unit. The pumping light is input to the optical fiber for amplification, and the seed laser light having a small spire value and the pumping light having the predetermined intensity are input in the preliminary pumping state for a certain period of time. The period is shorter than the period when the gain of the resonator of the fiber laser device is positive when input to the amplification optical fiber.

  According to such a fiber laser device, seed laser light having a small spire value is input to the amplification optical fiber in the pre-pumped state, so that the rare earth element is excited by the pump light and the rare earth element is relaxed by the seed laser light. Can balance. Therefore, according to the required specifications of the fiber laser device, the seed laser light intensity, the pumping light intensity in the pre-pumped state, and the predetermined period are optimized within the range where the gain of the resonator of the fiber laser device is not positive in the pre-pumped state. Can be set.

  Further, in the fiber laser device, the seed laser light output from the seed laser light source in the output state is pulsed light, and the seed laser light output from the seed laser light source in the preliminary excitation state is continuous light. It may be.

  In the fiber laser device, the optical fiber for amplification is provided between the amplification optical fiber and the output unit, and is output from the amplification optical fiber by the seed laser light and the excitation light having a small spire value in the preliminary excitation state. A wavelength converter that converts the wavelength of the laser light output from the amplification optical fiber by the seed laser light and the excitation light in the output state without converting the wavelength of the light to be output, the wavelength converter, and the output unit When the light having the same wavelength band as that of the seed laser light is input to the wavelength converter, the light that is wavelength-converted by the wavelength converter is transmitted and is not wavelength-converted by the wavelength converter. It is preferable to further include a wavelength selective filter that suppresses the transmission of.

  According to such a fiber laser device, in the pre-pumped state, the seed laser light having a small spire value input to the amplification optical fiber is amplified by stimulated emission of rare earth elements and output from the amplification optical fiber. However, the wavelength converter is configured not to convert the wavelength of the light output from the amplification optical fiber and input to the wavelength converter at this time. Accordingly, it is possible to suppress laser light from being output from the output unit in the preliminary excitation state.

  In the fiber laser device, it is preferable that the intensity of the excitation light in the preliminary excitation state is equal to or less than the intensity of the excitation light in the output state.

  ADVANTAGE OF THE INVENTION According to this invention, the fiber laser apparatus which can suppress the output of the unnecessary light with a high spire value except the period when a laser beam is output is provided, shortening the rising period of the output laser beam. .

1 is a diagram illustrating a fiber laser device according to a first embodiment of the present invention. It is a figure which shows the seed laser light source of FIG. 2 is a timing chart schematically showing the operation of the fiber laser device of FIG. 1. It is a figure which shows the fiber laser apparatus which concerns on 2nd Embodiment of this invention. It is the timing chart which showed typically operation | movement of the fiber laser apparatus which concerns on 3rd Embodiment of this invention. It is a figure which shows the fiber laser apparatus which concerns on 4th Embodiment of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a fiber laser device according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a fiber laser device according to a first embodiment of the present invention.

  As shown in FIG. 1, a fiber laser device 100 includes a seed laser light source 10 that outputs seed laser light having a wavelength λ1, an excitation light source 20 that outputs pump light, and an amplification that receives the pump light and the seed laser light. An optical fiber 30; an optical coupler 40 that inputs pumping light and seed laser light to the amplification optical fiber 30; an output unit 50 that outputs light output from the amplification optical fiber 30; A control unit 60 that controls the excitation light source 20, a command unit 65 that inputs a command to output and stop laser light from the output unit 50, and the intensity of excitation light output from the excitation light source 20 As a main configuration.

  FIG. 2 is a diagram showing the seed laser light source 10 of FIG. In the present embodiment, a Fabry-Perot type laser output device is used as the seed laser light source 10. As shown in FIG. 2, the seed laser light source 10 includes a laser oscillator 11 that outputs excitation light, a rare earth-doped fiber 13 that receives excitation light from the laser oscillator 11, and a rare earth-doped fiber 13 and the laser oscillator 11. A first FBG (Fiber Bragg Grating) 12 provided, a second FBG 15 provided on the opposite side of the rare earth-doped fiber 13 from the laser oscillator 11, and an AOM (Acoustic Optical Modulator) provided between the second FBG 15 and the rare earth doped fiber 13. Acousto-optic element) 14.

  The laser oscillator 11 is a semiconductor laser, for example, and outputs excitation light. The output excitation light has a wavelength of 975 nm, for example. The excitation light output from the laser oscillator 11 is input to the rare earth doped fiber 13 via the first FBG 12. The excitation light is absorbed by the rare earth element added to the rare earth doped fiber 13. For this reason, the rare earth element is in an excited state. The rare earth element in the excited state emits spontaneous emission light in a wavelength band including the wavelength λ1. The wavelength λ1 of the spontaneous emission light at this time is, for example, a wavelength of 1064 nm when the excitation light having the above-described wavelength of 975 nm is input to the rare earth fiber. This spontaneously emitted light propagates through the rare earth doped fiber 13 and is input to the AOM 14. The AOM 14 is controlled so as to periodically repeat a low-loss state and a high-loss state, or controlled so as to maintain a low-loss state.

  The AOM 14 suppresses transmission of light of a specific wavelength in a high loss state, and transmits light of a specific wavelength in a low loss state. For this reason, when the AOM 14 is in a low loss state, the spontaneous emission light is input to the second FBG 15 via the AOM 14. The second FBG 15 selectively reflects light in a wavelength band including the wavelength λ1 with a reflectance of about 50% or less, for example. Therefore, the reflected spontaneous emission light is input again to the rare earth doped fiber 13 via the AOM 14 and is amplified by the stimulated emission of the rare earth element of the rare earth doped fiber 13. Thereafter, the amplified light reaches the first FBG 12. The first FBG 12 selectively reflects light in a wavelength band including the wavelength λ1 with a reflectivity of 99.5%, for example. For this reason, the light reflected by the first FBG 12 is input again to the rare earth doped fiber 13 and further amplified. Thereafter, the amplified light is input to the second FBG 15 via the AOM 14, and a part of the light passes through the second FBG 15. In this way, the first FBG 12 and the second FBG 15 constitute a Fabry-Perot oscillator, and the pulsed light is amplified in synchronization with the operation in which the AOM 14 repeats a low loss state and a high loss state. Shaped light is output from the second FBG 15 as seed laser light. At this time, the wavelength λ1 of the seed laser light output from the seed laser light source 10 is, for example, a wavelength of 1064 nm, and the pulse repetition frequency is, for example, 100 kHz.

  When the AOM 14 is controlled to maintain a low loss state, the seed laser light source 10 outputs seed laser light that is continuous light at the same wavelength.

  In the seed laser light source 10, the output of the seed laser light as pulsed light or continuous light is controlled or the intensity thereof is controlled by controlling the AOM 14 with a control signal from the control unit 60. .

  The seed laser light output from the seed laser light source 10 is input to the optical coupler 40.

  On the other hand, the excitation light source 20 includes a plurality of laser diodes that output excitation light, and the intensity of the excitation light to be output is adjusted by a control signal from the control unit 60. The excitation light source 20 outputs excitation light that makes the rare earth element of the amplification optical fiber 30 excited, and the excitation light output from the excitation light source 20 is input to the optical coupler 40. The excitation light output from the excitation light source 20 has a wavelength of 975 nm, for example.

  The optical coupler 40 outputs an input port 41 to which seed laser light from the seed laser light source 10 is input, a pumping light input port 42 to which pumping light from the pumping light source 20 is input, and input seed laser light and pumping light. Output port 43. The input port 41 is composed of a single mode fiber that propagates seed laser light from the seed laser light source 10 as single mode light. The pumping light input port 42 is composed of a multimode fiber that propagates pumping light output from the pumping light source 20 as multimode light. The output port 43 is composed of a double clad fiber having a core, a clad that coats the core, and a resin clad that coats the clad, and propagates seed laser light as single-mode light through the core, and pumping light through the core and the clad. Is propagated as multimode light. The seed laser light and the pumping light output from the output port 43 are input to the amplification optical fiber 30.

  The amplification optical fiber 30 includes a double clad fiber having a core to which a rare earth element is added, a clad for covering the core, and a resin clad for covering the clad. The core propagates the seed laser light output from the optical coupler 40 as single mode light, and propagates the pumping light output from the optical coupler 40 by the core and the clad as multimode light. When the excitation light passes through the core, a part of the excitation light is absorbed by the rare earth element, and the excited state of the rare earth element is increased. The rare earth element in a high excitation state and inversion distribution state undergoes stimulated emission by the seed laser light propagating through the core, the seed laser light is amplified by this stimulated emission, and the laser light amplified from the amplification optical fiber 30. Is output. As such an optical fiber for amplification, for example, the core portion has a diameter of 10 μm, the cladding portion has an outer diameter of 125 μm, the core is made of quartz to which ytterbium is added as a rare earth element, and the cladding is made of a dopant. And those made of quartz to which no is added. When the output of laser light from the amplification optical fiber 30 is stopped, the excited state of the rare earth element is not immediately lowered even if the input of the excitation light to the amplification optical fiber 30 is stopped, and is constant. Gradually lowers over time.

  The output unit 50 outputs the laser light amplified by the amplification optical fiber 30 to the outside of the fiber laser device 100. When the pulsed seed laser light is output from the seed laser light source 10 as described above, the output unit 50 outputs a pulsed laser light synchronized with the seed laser light output from the seed laser light source 10. Is done.

  The command unit 65 inputs an output command for outputting laser light from the output unit 50 and an output stop command for stopping output of laser light from the output unit 50 to the control unit 60.

  The control unit 60 controls the seed laser light source 10 and the excitation light source 20 based on the output command from the command unit 65 and the output stop command. Specifically, the control unit 60 controls the laser oscillator 11 and the AOM 14 in the seed laser light source 10 to control the presence / absence and intensity of the output of the seed laser light source 10 and the seed laser light to be pulsed light or continuous light. I do. Further, the control unit 60 controls the excitation light source 20 to control the presence or absence of excitation light output from the excitation light source 20 and the intensity of excitation light output from the excitation light source 20.

  The memory 67 includes the intensity of the excitation light for outputting the laser light from the output unit 50 in the output state, and the excitation light (hereinafter referred to as preliminary excitation before the laser light is output from the output unit 50 in the preliminary excitation state). Light) intensity, a predetermined period during which preliminary excitation light is output, and the like are stored in advance. During this fixed period, when the preliminary pumping light having a preset intensity is input to the amplification optical fiber 30, the gain of the resonator of the fiber laser device is increased after the preliminary pumping light is input to the amplification optical fiber 30. This is a shorter period than the positive period. The preliminary excitation light intensity and the predetermined period are determined in advance by being measured in advance and stored in the memory 67.

  Here, the gain of the resonator of the fiber laser device 100 becomes positive, in other words, the gain in the laser resonator that can cause parasitic oscillation using the amplification optical fiber 30 as a gain medium exceeds the loss. In the fiber laser device 100, it is possible to grasp how much pre-pumping light of which intensity is input to the amplification optical fiber 30 and how much unintentional (parasitic) oscillation occurs by a prior experiment. The occurrence of parasitic oscillation means that the gain is positive in the oscillation resonator. Here, the resonator includes at least a part of the amplifying optical fiber 30, and is formed by light reflecting elements at both ends of the amplifying optical fiber 30 so as to cause parasitic oscillation. It refers to a resonator. Specifically, the light reflecting element includes a connection portion (fusion portion) between the seed laser light source 10 and the input port 41, a connection portion (fusion portion) between the amplification optical fiber 30 and the output port 43, and amplification. This is caused by a difference in refractive index existing in a connection portion between the optical fiber 30 and the output unit 50, Rayleigh scattering in the amplification optical fiber 30, and the like.

  The period during which the gain of the resonator is positive is, for example, in the case of the above-described amplification optical fiber 30, when the intensity of the preliminary pumping light is 4 W, after the preliminary pumping light is input to the amplification optical fiber 30 The period until the resonator gain of the fiber laser device 100 becomes positive and oscillates was 400 μs. For this reason, in the fiber laser device 100 according to the present embodiment, the certain period T is, for example, 200 μs shorter than the period 400 μs in which the gain of the resonator is positive.

  Here, the period during which the gain of the resonator is positive differs depending on the intensity of the preliminary pumping light. Therefore, it is preferable to set this certain period according to the intensity of the preliminary excitation light. Then, the laser output from the fiber laser device 100 is set by setting the certain period according to the intensity of the preliminary excitation light so that the excited state of the rare earth element after the certain period elapses to a predetermined certain level. It is possible to suppress variations in the rise time of light.

  Also, with the above-described amplification optical fiber 30, when the intensity of the preliminary pumping light is 2 W, the gain can be prevented from exceeding the loss even in a steady state where sufficient time has passed. The excited state of the element is at a predetermined constant level. In this case, this fixed period can be set to 5 ms, which is longer than the relaxation time of the rare earth element in the amplification optical fiber 30. Thus, by making the fixed period longer than the relaxation time of the rare earth element of the amplification optical fiber 30, the gain can be made constant, and the rise time of the output laser light can be shortened while the laser light is It is possible to suppress the output of unnecessary light having a high spire value outside the output period.

  In the counter 69, the control unit calculates a period after the output command from the command unit 65 is input to the control unit 60, a period after the output command is not input from the command unit 65 to the control unit 60, and the like. Output information for

  Next, the operation of the fiber laser device 100 will be described with reference to FIG.

  FIG. 3 is a timing chart schematically showing the operation of the fiber laser device 100.

  FIG. 3 shows an output command input from the command unit 65 to the control unit 60, the intensity of the excitation light output from the excitation light source 20, the intensity of the seed laser light output from the seed laser light source 10, and the amplification light. The rare-earth element excited state of the fiber 30 and the intensity of the laser beam output from the output unit 50 are schematically shown. In FIG. 3, a state in which the output command is H represents a state in which an output command is issued from the command unit 65 to the control unit 60, and the higher the excitation light intensity, the stronger the excitation light. A state in which the pumping light source 20 is output is shown, and the higher the intensity of the laser beam from the seed laser light source is, the more intense the seed laser light is output from the seed laser light source 10. The higher the excited state of the element, the higher the rare earth element of the amplification optical fiber 30 is in the excited state. The higher the intensity of the output laser light, the higher the output from the output unit 50. This shows a state where the intensity of the laser beam is high.

  First, a power supply (not shown) of the fiber laser device 100 is turned on, and power is supplied to the control unit 60. When power is supplied, the control unit 60 waits for an output command from the command unit 65.

  Next, at time t1, an output command is input from the command unit 65. The output command at time t1 is the first output command when the power of the fiber laser device 100 is turned on. In this case, the control unit 60 reads the intensity Rp of the preliminary excitation light from the memory 67, and the seed laser light source 10 and the excitation light source 20 are in the preliminary excitation state only for a predetermined period T using the signal from the counter 69. To control. Then, when the excitation light source 20 is in the preliminary excitation state, the excitation light source 20 is controlled to output the preliminary excitation light having the intensity Rp, and the seed laser light source 10 is controlled so that the seed laser light is not output. Note that the control of the seed laser light source 10 includes not instructing the seed laser light source 10 in particular. Thus, the excited state of the rare earth element in the amplification optical fiber 30 is gradually increased. However, as described above, the predetermined period T is shorter than the period in which the gain of the resonator of the fiber laser device 100 is positive after the preliminary pumping light having the intensity Rp is input to the amplification optical fiber 30. . Accordingly, it is possible to suppress the fiber laser device 100 from causing unintended oscillation in the preliminary excitation state.

  Next, at time t2 when a predetermined period T elapses from time t1, the control unit 60 controls the seed laser light source 10 and the excitation light source 20 to be in an output state. At this time, the control unit 60 reads the intensity Rs of the excitation light in the output state from the memory 67 and controls the excitation light source 20 to output the excitation light having a predetermined intensity Rs from the excitation light source 20. Further, the control unit 60 controls the seed laser light source 10 to output pulsed seed laser light having a spire value of intensity H and a wavelength λ1 from the seed laser light source 10. At this time, the intensity Rs of the excitation light and the intensity H of the spire value of the seed laser light are such that the laser light is output from the output unit 50. Specifically, the intensity Rs of the excitation light in the output state is 6 W, for example, and the intensity H of the spire value of the seed laser light is 4 W, for example.

  In the output state, when the excitation light of intensity Rs is output from the excitation light source 20 and the pulsed seed laser light is output from the seed laser light source 10, the rare earth element of the amplification optical fiber 30 is set to a higher excitation state. However, stimulated emission is caused to amplify the intensity of the seed laser beam. Therefore, the amplified pulsed laser light is output from the amplification optical fiber 30, and the amplified pulsed laser light is output from the output unit 50.

  However, the intensity of the laser beam output from the output unit 50 does not reach the predetermined intensity P at a time point immediately after the time t2. When a predetermined period elapses from time t2, the excited state of the rare earth element is further increased, and laser light having a predetermined intensity P is output from the output unit 50, and the output of the laser light is stabilized. This predetermined period is a rising period of the laser light output from the output unit 50. For example, when the power is turned on and the first laser beam is output, the preliminary pumping light intensity Rp is set to 2 W as described above, the fixed period T is set to 100 μsec, and the pumping light intensity Rs in the output state is set to When the intensity H of the spire value of the seed laser beam is 4 W, the rising period of the laser beam is 50 μsec or less.

  Next, when an output command is no longer input from the command unit 65 at time t3, the control unit 60 uses the information in the counter 69 to calculate a certain period T from time t3, and the certain period T has elapsed from time t3. At time t4, the output states of the seed laser light source 10 and the excitation light source 20 are terminated. At this time, the output of the seed laser light from the seed laser light source 10 and the output of the excitation light from the excitation light source 20 are stopped. For this reason, the output of the laser beam from the output unit 50 is stopped. Then, the control unit 60 waits for the output command from the command unit 65 again.

  In the present embodiment, the command unit 65 continues to input the output command to the control unit 60 and stops the output of the laser beam during the period in which the laser beam is to be output as described above. The input of the output command to the control unit 60 is stopped. Therefore, in the present embodiment, the command unit 65 stopping the input of the output command to the control unit 60 corresponds to the command unit 65 inputting the output stop command to the control unit 60.

  As shown in FIG. 3, the excited state of the rare earth element in the amplification optical fiber 30 gradually decreases from the end time t4 of the output state, and becomes a ground state after a predetermined period has elapsed from the time t4.

  Next, an output command is input from the command unit 65 to the control unit 60 at time t5 after a period Ta longer than the predetermined period T from time t3. That is, the output command is input to the control unit 60 at time t5 after time t4 when a certain period T elapses from time t3. At this time, at time t5, the output states of the seed laser light source 10 and the excitation light source 20 have already been completed. In this case, the control unit 60 reads the intensity Rp of the preliminary pumping light from the memory 67 and uses the signal from the counter 69 so that the seed laser light source 10 and the pumping light source 20 are used for a predetermined period T from time t5. Control is performed so as to be in a pre-excited state. The excitation light source 20 is controlled so as to output the preliminary excitation light having the intensity Rp, and the seed laser light source 10 is controlled so as not to output the seed laser light. In this way, as in the case of the preliminary pumping from time t1 to time t2, the excited state of the rare earth element in the amplification optical fiber 30 is gradually increased. However, the preliminary pumping light having the intensity Rp is maintained for a certain period T from t5 to t6. Since it is shorter than the period in which the gain of the resonator of the fiber laser device 100 is positive after being input to the amplification optical fiber 30, the fiber laser device 100 causes unintended oscillation in this preliminary excitation state. Is suppressed.

  Next, at time t6 when a certain period T elapses from time t5, the control unit 60 controls the seed laser light source 10 and the excitation light source 20 to be in an output state. At this time, the control unit 60 reads the intensity Rs of the excitation light in the output state from the memory 67 and controls the excitation light source 20 to output the excitation light having a predetermined intensity Rs from the excitation light source 20. Further, the control unit 60 controls the seed laser light source 10 to output pulsed seed laser light having a spire value of intensity H and a wavelength λ1 from the seed laser light source 10.

  Thus, the rare earth element of the amplification optical fiber 30 is stimulated to emit by the seed laser light while being in a higher excitation state, and amplifies the intensity of the seed laser light input from the seed laser light source 10. Then, the amplified pulsed laser beam is output from the output unit 50. At this time, similarly to the laser light output after the elapse of time t2, when a predetermined period elapses from time t6, the excited state of the rare earth element is further increased, and the laser light output from the output unit 50 rises. .

  Next, when an output command is not input from the command unit 65 to the control unit 60 at time t7, the control unit 60 outputs the seed laser light source 10 and the excitation light source 20 at time t9 when a certain period T has elapsed from time t7. In order to end the state, a predetermined period T is calculated from time t7 using information of the counter 69.

  Next, at time t8 before time t9 when a certain period T elapses from time t7, the output command is input from the command unit 65 to the control unit 60 again. That is, the output command is input from the command unit 65 to the control unit 60 at a time t8 when a period Tb that is shorter than the fixed period T has elapsed after the output stop command is input to the control unit 60 at the time t7. . At this time, since the time t8 is a time before the fixed period T has elapsed from the time t7, the output states of the seed laser light source 10 and the excitation light source 20 have not ended. In this case, the control unit 60 determines that the period Tb is shorter than the predetermined period T stored in the memory 67 in advance, and leaves the seed laser light source 10 and the excitation light source 20 in the output state, and from the command unit 65 The output states of the seed laser light source 10 and the excitation light source 20 are terminated at time t9 when a predetermined period T elapses from time t7 when no output command is input to the control unit 60.

  At time t9 when the output states of the seed laser light source 10 and the excitation light source 20 are terminated, the control unit 60 reads the intensity Rp of the preliminary excitation light from the memory 67 and inputs an output command using the information of the counter 69. The seed laser light source 10 and the excitation light source 20 are set in the pre-excitation state from the time t8 to the time t10 when the predetermined period T elapses. Then, when the excitation light source 20 is in the preliminary excitation state, the excitation light source 20 is controlled to output the preliminary excitation light having the intensity Rp, and the seed laser light source 10 is controlled so that the seed laser light is not output. In this way, the seed laser light source 10 and the excitation light source 20 are controlled so as to change from the output state to the preliminary excitation state, and are in the preliminary excitation state from time t9 to time t10. The period Tb from t10 to t11 is shorter than the predetermined period T, and is shorter than the period in which the gain of the resonator of the fiber laser device 100 is positive after the preliminary pumping light having the intensity Rp is input to the amplification optical fiber 30. Therefore, in this preliminary excitation state, the fiber laser device 100 is prevented from causing unintended oscillation.

  When the seed laser light source 10 and the pumping light source 20 are set in the preliminary pumping state, the intensity of the pumping light input to the amplification optical fiber 30 becomes weak, so that the pumping state of the rare earth element in the amplification optical fiber is gradually lowered. However, at the time t10, the excited state of the rare earth element can be brought closer to the predetermined excited state as compared with the case where the pre-excitation is not performed.

  Next, at time t10, the control unit 60 sets the seed laser light source 10 and the excitation light source 20 to the output state. For this reason, pulsed laser light rises and is output from the output unit 50.

  Next, when an output command is not input from the command unit 65 to the control unit 60 at time t11, the control unit 60 uses the information of the counter 69, and at time t12 when a certain period T has elapsed from time t11, the seed laser The output states of the light source 10 and the excitation light source 20 are terminated.

  As described above, when the period from the time t3 when the output stop command is input to the time t5 when the next output command is input is the period Ta longer than the predetermined period T, the seed laser light source 10 and the excitation The light source 20 is in a pre-excitation state only for a certain period T from when the output command is input until it enters the output state. That is, the seed laser light source 10 and the excitation light source 20 are set in the preliminary excitation state only for a certain period T during which time shift is performed after the output command is input, and the output command is output from the end time t4 of the output state before the output command is input. The period up to input time t5 is not in the pre-excitation state. The fixed period T in which the preliminary pumping state is set is shorter than a period in which the gain of the resonator of the fiber laser device 100 is positive after the preliminary pumping light having the intensity Rp is input to the amplification optical fiber 30. It is. As described above, the seed laser light source 10 and the excitation light source 20 are set in the preliminary excitation state, thereby bringing the excitation state of the rare earth element close to a predetermined high level at the start of the output state and suppressing variations in the rising period of the laser light. However, it can be shortened. That is, the excited state (inversion distribution state) of the rare earth element at the start of the output state can be controlled to be constant regardless of the length of the stop state of the fiber laser device 100. It can be shortened while suppressing variations. Further, the gain of the resonator of the fiber laser device 100 becomes positive after the seed laser light source 10 and the pumping light source 20 are input to the amplification optical fiber 30 for a predetermined period T, that is, when the preliminary pumping light having the intensity Rp is input. Since the preliminary pumping state is set for a period shorter than the period, unintentional oscillation of the fiber laser device 100 can be suppressed, and output of unnecessary light having a high spire value can be suppressed. On the other hand, when the period Tb from the time t7 when the output stop command is input to the time t8 when the next output command is input is shorter than the fixed period T, the output state is changed from the time t9 when the output state ends. Until the start time t10, the seed laser light source 10 and the excitation light source 20 are in a preliminary excitation state. In this way, even when the preliminary excitation period T cannot be secured sufficiently, by performing preliminary excitation during that period, the rise of the laser beam in the output state can be accelerated compared to the case where preliminary excitation is not performed. As described above, according to the fiber laser device 100 of the present embodiment, the output period of the output laser light is shortened, and the output of unnecessary light having a high spire value is suppressed outside the period in which the laser light is output. be able to.

  Further, according to such a fiber laser device 100, the seed laser light source 10 and the excitation light source 20 are set in the output state after a predetermined period T after the output command is input to the control unit 60, and the output stop command is issued. Is input to the control unit 60, and the output state is terminated after a certain period T. That is, until the seed laser light source 10 and the excitation light source 20 are set in the output state after the output command is input to the control unit 60, and after the output stop command is input to the control unit 60, the seed laser light source 10 and Each time until the excitation light source 20 ends the output state, the time shifts by a certain period T. Therefore, the period from when the output command is input to the control unit 60 until the output stop command is input is the same as the period during which the seed laser light source 10 and the excitation light source 20 are in the output state. The fiber laser device 100 can be used without a sense of incongruity.

(Second Embodiment)
Next, a second embodiment of the present invention will be described in detail with reference to FIG. In addition, about the component same or equivalent to 1st Embodiment, the same referential mark is attached | subjected and the overlapping description is abbreviate | omitted. FIG. 4 is a diagram showing a fiber laser device according to the second embodiment of the present invention.

  As shown in FIG. 4, the fiber laser device 110 includes a wavelength converter 71 that is provided between the amplification optical fiber 30 and the output unit 50, and that receives light output from the amplification optical fiber 30, and a wavelength converter. It differs from 1st Embodiment by the point provided with the wavelength selection filter 73 which is provided between 71 and the output part 50 and into which the light output from the wavelength converter 71 inputs.

  The wavelength converter 71 is composed of an optical fiber that causes stimulated Raman scattering. This wavelength converter converts incident light into light having a longer wavelength when the spire value of the incident light is large, and outputs it without converting the wavelength of the incident light when the spire value of the incident light is small. In the present embodiment, the wavelength converter 71 is constituted by a wavelength conversion optical fiber, and converts light wavelength when light having a predetermined intensity or more is input. Specifically, when the wavelength converter 71 performs wavelength conversion, when laser light having a wavelength of λ1 is input, the light input to the wavelength converter 71 by stimulated Raman scattering is light having a wavelength λ2 that is longer than the wavelength λ1. Convert to For this reason, the wavelength converter 71 outputs light having a longer wavelength than the input light.

  In the preliminary excitation state, when preliminary excitation light is input from the excitation light source 20 to the amplification optical fiber 30, spontaneous emission light is generated in the amplification optical fiber 30. This spontaneously emitted light is amplified by the amplification optical fiber 30 and output as ASE, and then input to the wavelength converter 71. However, the light output from the amplification optical fiber 30 at this time is not wavelength-converted by the wavelength converter 71 because the spire value is small. On the other hand, in the output state, the seed laser light is output from the seed laser light source 10, the pump light is output from the pump light source 20, the seed laser light is amplified in the amplification optical fiber 30, and the laser light is output. This is input to the wavelength converter 71. At this time, the laser light output from the amplification optical fiber 30 is wavelength-converted by the wavelength converter 71 because the spire value is large.

  Examples of such an optical fiber for wavelength conversion include an optical fiber composed of a core and a clad, and an optical fiber to which a dopant that increases the nonlinear optical constant is added. Examples of such a dopant include germanium and phosphorus. For example, the wavelength converter 71 is a single mode fiber having a core added with 7 to 8% by mass of germanium, a core diameter of 5 μm, and a length of 20 m, and has a wavelength of a spire value of pulsed light of 70 W or more. When light having a wavelength λ1 of 1064 nm is input, light having a wavelength λ2 of 1120 nm is output, and when light having an intensity lower than 70 W is input, wavelength conversion is not performed. The threshold value of the wavelength conversion spire value of the wavelength converter 71 can be changed according to the diameter of the core, the dopant concentration, the length, and the like. Therefore, the diameter of the core, the dopant concentration, and the length of the wavelength converter 71 of the present embodiment are such that wavelength conversion occurs when the spire value of light having a wavelength of 1120 nm is larger than 70 W, and is smaller than that. Is set so that wavelength conversion does not occur. On the other hand, when the core diameter, the dopant addition concentration, and the length of the wavelength converter 71 are determined in advance, the input light that does not undergo wavelength conversion in the preliminary excitation state and undergoes wavelength conversion in the output state. The outputs of the seed laser light source 10 and the excitation light source 20 are set so as to have a spire value.

  When wavelength laser light output from the seed laser light source 10 is input via the wavelength converter 71, the wavelength selection filter 73 transmits the laser light that has been wavelength-converted by the wavelength converter 71 and is input. In 71, transmission of the laser beam inputted without wavelength conversion is suppressed. Therefore, when laser light with high intensity is output from the amplification optical fiber 30 and wavelength conversion of the laser light is performed by the wavelength converter 71, the laser light input to the wavelength selection filter 73 passes through the wavelength selection filter 73. On the other hand, when a laser beam with low intensity is output from the amplification optical fiber 30 and the wavelength of the laser beam is not converted by the wavelength converter 71, the transmission of the laser beam input to the wavelength selection filter 73 is suppressed by the wavelength selection filter 73. The

  The wavelength selection filter 73 is composed of, for example, a dielectric multilayer filter, a photonic band gap fiber, or the like. Then, for example, as described above, the laser beam having the wavelength λ1 of 1064 nm is input to the wavelength converter 71 and is converted by the wavelength converter 71 to be converted into the laser beam having the wavelength λ2 of 1120 nm. When the laser beam is input to the laser beam, the laser beam passes through the wavelength selection filter 73. On the other hand, when a laser beam having a wavelength λ1 of 1064 nm is input to the wavelength converter 71 and the 1064 nm laser beam is directly input to the wavelength selection filter 73 without being wavelength-converted by the wavelength converter 71, the laser beam is wavelength-selected. Transmission by the filter 73 is suppressed. Note that the intensity of the preliminary excitation light and the predetermined time T are set in the same manner as in the first embodiment.

  Next, the operation of the fiber laser device 110 will be described.

  In the fiber laser device 110, similarly to the fiber laser device 100 of the first embodiment, periods in which the excitation light source 20 and the seed laser light source 10 are in the preliminary excitation state (t1 to t2, t5 to t6, t9 to t10). The preliminary pumping light is output from the pumping light source 20.

  At this time, spontaneous emission light is generated in the amplification optical fiber 30 by the preliminary pumping light input to the amplification optical fiber 30. This spontaneously emitted light is amplified by the amplification optical fiber 30 and output as ASE, and then input to the wavelength converter 71. However, the light output from the amplification optical fiber 30 is not wavelength-converted by the wavelength converter 71 as described above because the spier value is smaller than the spier value threshold of the wavelength converter 71. Therefore, transmission of light input from the wavelength converter 71 to the wavelength selection filter 73 is suppressed in the wavelength selection filter. For this reason, no light is output from the output unit 50 in the preliminary excitation state.

  As described above, when the wavelength converter 71 is a single-mode fiber having a length of 20 m, the core is made of quartz to which 7 to 8% by mass of germanium is added, and the diameter of the core is 5 μm, for example, preliminary excitation light If the intensity R1 is 2 W, the light that is amplified and output in the amplification optical fiber 30 and input to the wavelength converter 71 has a spier value smaller than the wavelength conversion spier value threshold of the wavelength converter 71. Wavelength conversion is not performed by the wavelength converter 71.

  Next, in the period (t2 to t4, t6 to t9, t10 to t12) in which the excitation light source 20 and the seed laser light source 10 are in the output state, the excitation light with the intensity Rs is output from the excitation light source 20 and the seeds. The laser light source 10 outputs a pulsed seed laser beam having a spire value of intensity H and a wavelength λ1. At this time, since the laser light output from the amplification optical fiber 30 is larger than the spier value threshold of wavelength conversion of the wavelength converter 71, the wavelength conversion is performed in the wavelength converter 71. Accordingly, the laser light input from the wavelength converter 71 to the wavelength selection filter 73 passes through the wavelength selection filter and is output from the output unit 50. As described above, also in the fiber laser device 110 according to the present embodiment, as in the first embodiment, during the preliminary pumping state, pump light having a predetermined intensity is input to the amplification optical fiber and the fiber laser device. Therefore, the fiber laser device does not oscillate unintended. For this reason, it is possible to suppress the output of unnecessary light having a high spire value outside the period in which the laser light is output. For example, as described above, the wavelength converter 71 is a single-mode fiber having a length of 20 m, the core is made of quartz to which 7 to 8% by mass of germanium is added, and the diameter of the core is 5 μm. When the intensity of the excitation light Rs in the output state is 6 W and the intensity H of the spire value of the seed laser light is 4 W, the spire value of the laser light is 185 W, and the laser light input to the wavelength converter 71 Is wavelength converted.

  According to such a fiber laser device 110, when the laser light amplified by the amplification optical fiber 30 is output in the output state, the wavelength of the laser light is converted by the wavelength converter 71. The laser beam converted in wavelength by the wavelength converter 71 is input to the wavelength selection filter 73, passes through the wavelength selection filter 73, and is output from the output unit 50. On the other hand, in the preliminary excitation state, the rare earth element of the amplification optical fiber 30 is excited by the preliminary excitation light. Meanwhile, the amplification optical fiber 30 is configured such that the seed laser light output from the seed laser light source 10 is amplified by stimulated emission of a rare earth element that is excited by excitation light. However, since the seed laser light is not input to the amplification optical fiber 30 in the preliminary excitation state, ASE obtained by amplifying the spontaneous emission light emitted from the excited rare earth element is output from the amplification optical fiber. Since the spontaneous emission light has a wide spectrum and the intensity of the spire value is small, even if ASE is input from the amplification optical fiber 30 in the wavelength converter 71, the wavelength of the input light is not converted. For this reason, even when ASE is output from the amplification optical fiber 30, transmission of light output from the wavelength converter 71 and input to the wavelength selection filter 73 is suppressed in the wavelength selection filter 73. Thus, unnecessary light output from the output unit 50 can be suppressed in the preliminary excitation state.

In the present embodiment, the wavelength converter 71 is configured by an optical fiber that causes stimulated Raman scattering. However, when the wavelength converter 71 has a high spire value of the intensity of input light, If this light is converted into light of a different wavelength and output, and the spire value of the intensity of the input light is small, it is limited to an optical fiber as long as it has a function to output the light without converting it. Absent. For example, the wavelength converter 71 may be a nonlinear optical crystal that generates second harmonics such as lithium triborate (LiB ₃ O ₅ ). Such a nonlinear optical crystal outputs a second harmonic (light having a wavelength of 1/2) when light having an intensity equal to or higher than a predetermined spire value is input. When a nonlinear optical crystal that generates the second harmonic is used as the wavelength converter 71, the latter wavelength selection filter 73 suppresses the transmission of the wavelength of the light input to the wavelength converter 71. A filter that transmits a second harmonic wavelength is used.

(Third embodiment)
Next, a third embodiment of the present invention will be described in detail with reference to FIG. In addition, about the component same or equivalent to 2nd Embodiment, the same referential mark is attached | subjected and the overlapping description is abbreviate | omitted. The present embodiment is a fiber laser device using the fiber laser device 110 described in the second embodiment.

  FIG. 5 is a timing chart showing the operation of the fiber laser device 110 according to the third embodiment of the present invention. The fiber laser apparatus 110 of the present embodiment is the second embodiment in that preliminary pumping light is output from the pumping light source 20 and seed laser light having a small spire value is output from the seed laser light source 10 in the preliminary pumping state. This is different from the embodiment of the fiber laser device 110.

  Specifically, as shown in FIG. 5, when an output command is input from the command unit 65 at time t1 (t5, t8), the control unit 60 causes the seed laser light source for the same period as in the second embodiment. 10 and the excitation light source 20 are controlled to be in a preliminary excitation state. Then, the control unit 60 reads the intensity Rp of the preliminary pumping light from the memory 67 and outputs the preliminary pumping light having the intensity Rp from the pumping light source 20 using the signal from the counter 69 as in the second embodiment. Further, in the present embodiment, in the preliminary excitation state, the control unit 60 controls the seed laser light source 10 to output seed laser light having a small spire value of intensity L. In the present embodiment, the seed laser light having a small spire value is continuous light.

  The excitation light output from the excitation light source 20 and the seed laser light output from the seed laser light source 10 with a small spire value are input to the amplification optical fiber 30. Then, in the amplification optical fiber 30, the seed laser light is amplified and output from the amplification optical fiber 30 by the stimulated emission by the seed laser light having a small spire value, and is input to the wavelength converter 71. However, the wavelength converter 71 is configured not to convert the wavelength of the input light even if the light output after the seed laser light is amplified in the amplification optical fiber 30 is input to the wavelength converter 71. For example, as described above, when the wavelength converter 71 is a single-mode fiber having a length of 20 m, the core is made of quartz to which 7 to 8% by mass of germanium is added, and the diameter of the core is 5 μm, When the intensity L of the seed laser light having a small spire value in the excited state is 1 W and the intensity of the preliminary excitation light is 2 W, the wavelength converter 71 is configured not to perform wavelength conversion.

  According to the fiber laser device 110 of the present embodiment, since the seed laser light is input to the amplification optical fiber 30 in the preliminary pumping state, the rare earth element is excited by the pump light and the rare earth element is relaxed by the seed laser light. Can be balanced. That is, according to the required specifications of the fiber laser device, the seed laser light intensity, the pumping light intensity in the pre-pumped state, and the predetermined period are optimized within a range where the gain of the fiber laser device resonator is not positive in the pre-pumped state. Can be set. Therefore, it is possible to suppress the fiber laser device 100 from causing unintended oscillation, and it is possible to further suppress the output of unnecessary light having a high spire value in the preliminary excitation state.

  Further, in the preliminary excitation state, the seed laser light having a small spire value is amplified by the stimulated emission of the amplification optical fiber 30, and the light having the wavelength λ1 is output. However, in the preliminary excitation state, the light output from the amplification optical fiber 30 is not wavelength-converted by the wavelength converter 71. Therefore, the transmission of the laser light input from the wavelength converter 71 to the wavelength selection filter 73 is suppressed in the wavelength selection filter 73. Therefore, unnecessary light output can be suppressed in the preliminary excitation state.

(Fourth embodiment)
Next, a fourth embodiment of the present invention will be described in detail with reference to FIG. In addition, about the component same or equivalent to 1st Embodiment, the same referential mark is attached | subjected and the overlapping description is abbreviate | omitted. FIG. 6 is a diagram showing a fiber laser device according to the fourth embodiment of the present invention.

  As shown in FIG. 6, the fiber laser device 130 is provided between the seed laser light source 10 and the optical coupler 40, and includes a wavelength converter 75 that receives the seed laser light output from the seed laser light 10, and a wavelength converter. It differs from 1st Embodiment by the point provided with the wavelength selection filter 76 which is provided between 75 and the optical coupler 40, and the light output from the wavelength converter 75 inputs into it.

  The wavelength converter 75 has the same configuration as the wavelength converter 71 of the second embodiment, and converts the wavelength when the spire value of the input light is larger than a predetermined value, and the spire value is smaller than the predetermined value. The wavelength converter 71 is common to the wavelength converter 71 of the second embodiment in that the wavelength is not converted, but the wavelength converter 71 of the second embodiment is set so as to convert the wavelength even with light having a smaller spire value than the light subjected to wavelength conversion. This is different from the wavelength converter 71 of the second embodiment. Specifically, when seed laser light having a low spire value is output from the seed laser light source 10 in the preliminary excitation state, the wavelength converter 75 does not convert the wavelength of the seed laser light. When seed laser light having a predetermined intensity or more is input in the output state, the seed laser light input to the wavelength converter 75 is converted into light having a longer wavelength by stimulated Raman scattering or the like. For this reason, when seed laser light having a steeple value higher than a predetermined steeple value is output from the seed laser light source 10, seed laser light having a wavelength longer than that of the seed laser light is output from the wavelength converter 75.

  The wavelength selection filter 76 has the same configuration as the wavelength selection filter 73 of the second embodiment. When the seed laser light output from the seed laser light source 10 is input via the wavelength converter 75, the wavelength converter 75 The wavelength-converted laser beam that is input is transmitted, and the wavelength converter 75 suppresses the transmission of the input laser beam without wavelength conversion. Accordingly, when seed laser light having a high spire value is output from the seed laser light source, wavelength conversion is performed by the wavelength converter 75, so that the wavelength selection filter 76 transmits the seed laser light. On the other hand, when the seed laser light having a small spire value is output from the seed laser light 10 and the laser light is not wavelength-converted by the wavelength converter 75, the seed laser light input to the wavelength selection filter 76 is transmitted through the wavelength selection filter 76. It is suppressed. Note that the intensity of the preliminary excitation light and the predetermined time T are set in the same manner as in the first embodiment.

  The operation of the fiber laser device 130 in the present embodiment may be read as “seed laser light from the seed laser light source” in FIG. 3 as “seed laser light from the wavelength selection filter 76”. That is, in the fiber laser device 130 according to the present embodiment, the seed laser light does not have to be output from the seed laser light source 10 in the preliminary excitation state, and the spire is not subjected to wavelength conversion by the wavelength converter 75 from the seed laser light source 10. A seed laser beam having a value may be output. In these cases, since the seed laser beam is not output from the wavelength selection filter 76 as described above, the excited state of the rare earth element in the amplification optical fiber 30 is gradually increased in the preliminary excitation state as shown in FIG. In the output state, seed laser light having a high spire value is output from the seed laser light source 10. Accordingly, the seed laser light is wavelength-converted by the wavelength converter 75 and passes through the wavelength selection filter 76. Thus, the seed laser light is input to the amplification optical fiber 30, the seed laser light is amplified in the amplification optical fiber 30, and the seed laser light amplified from the output unit 50 is output as output light. For example, in the preliminary excitation state, the seed laser light output from the seed laser light source 10 is continuous light, and the seed laser light in the output state is pulsed light. In this case, since pulse light generally has a steeple value higher than that of continuous light, it is only necessary to control the operation of the AOM 14 shown in FIG. 2, and the control of the operation can be simplified.

  The present invention has been described above by taking the first to fourth embodiments as examples. However, the present invention is not limited to this.

  For example, in the first embodiment, in the preliminary excitation state, the control unit 60 performs control so that laser light is not output from the seed laser light source 10, but the present invention is not limited to this. For example, in the preliminary excitation state, the control unit 60 may perform control so that seed laser light having a small spire value is output from the seed laser light source 10. With this configuration, since the seed laser light is input to the amplification optical fiber 30 in the pre-pumped state, the excitation of the rare earth element by the excitation light and the relaxation of the rare earth element by the seed laser light are balanced. Can do. Therefore, according to the required specifications of the fiber laser device, the seed laser light intensity, the pumping light intensity in the pre-pumped state, and the predetermined period are optimized within the range where the gain of the resonator of the fiber laser device is not positive in the pre-pumped state. Can be set. Thereby, it can suppress that the fiber laser apparatus 100 raise | generates the oscillation which is not intended, and can suppress further that unnecessary light with a high spire value is output in a preliminary | backup excitation state.

  In this case, since the pumping light and the seed laser light having a small spire value are input to the amplification optical fiber 30 in the preliminary pumping state, the laser light obtained by amplifying the seed laser light having a small spire value is amplified from the amplification optical fiber 30. Is output. However, since the intensity of the seed laser light having a small spire value input to the amplification optical fiber 30 is very weak, the laser light output from the amplification optical fiber 30 is also weak, which may be a problem depending on the application of the fiber laser device 100. Must not.

  In the first to fourth embodiments, the seed laser light source 10 is a Fabry-Perot type laser output device, but may be a fiber ring type laser output device. Further, in the output state, the seed laser light output from the seed laser light source 10 is pulsed light, but may be continuous light.

  In the first to fourth embodiments, the intensity of the excitation light output from the excitation light source 20 in the preliminary excitation state is weaker than the excitation light output from the excitation light source 20 in the output state. The present invention is not limited to this. The excitation light output from the excitation light source 20 in the preliminary excitation state and the excitation light output from the excitation light source 20 in the output state may be excitation light having the same intensity. In this case, the excitation light source 20 may be in the same state in the preliminary excitation state and the output state, so that the load on the control unit can be reduced.

  Further, although the amplification optical fiber 30 propagates laser light as single mode light, the present invention is not limited to this, and may have a configuration capable of propagating several modes of light, for example.

  The command unit 65 may be configured to input an output command to the control unit 60, and the output command is generated outside the fiber laser device and is input to the control unit 60 via the command unit 65. There may be.

  Furthermore, in the above-described embodiment, the command unit 65 continues to input an output command to the control unit 60 for a period of time during which laser light is to be output, and at the time of stopping the output of laser light, the command unit 65. The input of the output command to the control unit 60 was stopped. The stop of the input of the output command from the command unit 65 to the control unit 60 is the input of the output stop command from the command unit 65 to the control unit 60. However, the present invention is not limited to this. For example, at the time when the laser beam is to be output, a pulse signal as an output command is input from the command unit 65 to the control unit 60, and the output of the laser beam is further stopped. A pulse signal as an output stop command may be input from the command unit 65 to the control unit 60 at the time to be performed.

  Further, in the first to fourth embodiments, the pumping light intensity in the preliminary pumping state is set to a predetermined value. However, the pumping state of the rare earth element in the amplification optical fiber 30 in the preliminary pumping state is monitored, and the predetermined pumping state is set. The excitation light intensity in the preliminary excitation state may be controlled so that The monitoring of the excited state of the rare earth element in the amplification optical fiber 30 can control the excitation light intensity, for example, by receiving the ASE light intensity from the amplification optical fiber 30 with a photodiode (PD) or the like.

  In the second embodiment, the same wavelength change 75 and wavelength selection filter 76 as those in the fourth embodiment may be provided in the same manner as in the fourth embodiment.

  ADVANTAGE OF THE INVENTION According to this invention, the fiber laser apparatus which can suppress the output of the unnecessary light with a high spire value except the period when a laser beam is output is provided, shortening the rising period of the output laser beam. .

DESCRIPTION OF SYMBOLS 10 ... Laser light source 11 ... Excitation light source 12 ... 1st FBG
13 ... rare earth doped fiber 14 ... AOM
15 ... 2nd FBG
DESCRIPTION OF SYMBOLS 20 ... Excitation light source 30 ... Amplifying optical fiber 40 ... Optical coupler 50 ... Output part 60 ... Control part 65 ... Command part 67 ... Memory 69 ... Counter 71, 75 ... wavelength converter 73, 76 ... wavelength selection filter 100, 110, 130 ... fiber laser device

Claims (6)

A seed laser light source for outputting seed laser light;
An excitation light source that outputs excitation light;
An amplification optical fiber that receives the seed laser light and the excitation light, adds a rare earth element that is excited by the excitation light, amplifies the seed laser light, and outputs the laser light;
An output unit for outputting the laser beam output from the amplification optical fiber;
A control unit that controls at least the seed laser light source and the excitation light source;
An output command for outputting the laser beam from the output unit, and a command unit for inputting an output stop command for stopping the output of the laser beam from the output unit to the control unit;
With
The seed laser light source and the excitation light source are:
The output state is set to an output state after a predetermined period after the output command is input to the control unit, the output state is ended after the predetermined period after the output stop command is input to the control unit, and
When a period from when the output stop command is input to the control unit to when the output command is input to the control unit is shorter than the predetermined period, the output state is output after the end of the output state. Until it becomes a pre-excited state,
When a period from when the output stop command is input to the control unit to when the output command is input to the control unit is longer than the certain period, the output is next performed after the output state ends. Until the command is input to the control unit, it is in a stopped state, and from the time when the output command is input to the control unit to the next output state, it is in the preliminary excitation state,
In the preliminary excitation state, the seed laser light is not input to the amplification optical fiber, the excitation light is input to the amplification optical fiber with a predetermined intensity, and in the output state, the laser light is The seed laser light is input to the amplification optical fiber and the excitation light is input to the amplification optical fiber so that it is output from the output unit,
The fixed period is a period shorter than a period shorter than a period in which the gain of the resonator of the fiber laser device is positive because the pump light of the predetermined intensity is input to the amplification optical fiber in the preliminary pumping state. A fiber laser device characterized by the above. Provided between the amplification optical fiber and the output unit, the light generated and output from the amplification optical fiber by the pumping light in the preliminary pumping state is not wavelength-converted, and the seed is output in the output state. A wavelength converter for wavelength-converting the laser light output from the amplification optical fiber by laser light and the excitation light;
Provided between the wavelength converter and the output unit, when light having the same wavelength band as the seed laser light is input to the wavelength converter, the light that is wavelength-converted in the wavelength converter is transmitted, A wavelength selective filter that suppresses transmission of light that is not wavelength-converted in the wavelength converter;
The fiber laser device according to claim 1, further comprising: A seed laser light source for outputting seed laser light;
An excitation light source that outputs excitation light;
An amplification optical fiber that receives the seed laser light and the excitation light, adds a rare earth element that is excited by the excitation light, amplifies the seed laser light, and outputs the laser light;
An output unit for outputting the laser beam output from the amplification optical fiber;
A control unit that controls at least the seed laser light source and the excitation light source;
An output command for outputting the laser beam from the output unit, and a command unit for inputting an output stop command for stopping the output of the laser beam from the output unit to the control unit;
With
The seed laser light source and the excitation light source are:
The output state is set to an output state after a predetermined period after the output command is input to the control unit, the output state is ended after the predetermined period after the output stop command is input to the control unit, and
When a period from when the output stop command is input to the control unit to when the output command is input to the control unit is shorter than the predetermined period, the output state is output after the end of the output state. Until it becomes a pre-excited state,
When a period from when the output stop command is input to the control unit to when the output command is input to the control unit is longer than the certain period, the output is next performed after the output state ends. Until the command is input to the control unit, it is in a stopped state, and from the time when the output command is input to the control unit to the next output state, it is in a pre-excitation state,
In the preliminary excitation state, seed laser light having a small spire value is input to the amplification optical fiber, and the excitation light is input to the amplification optical fiber with a predetermined intensity. In the output state, The seed laser light is input to the amplification optical fiber and the excitation light is input to the amplification optical fiber so that the laser light is output from the output unit.
During the predetermined period, in the preliminary excitation state, the seed laser light having a small spire value and the excitation light having the predetermined intensity are input to the amplification optical fiber, and the gain of the resonator of the fiber laser device is positive. A fiber laser device characterized in that the period is shorter than the period.   The seed laser light output from the seed laser light source in the output state is pulsed light, and the seed laser light output from the seed laser light source in the preliminary excitation state is continuous light. Item 4. The fiber laser device according to Item 3. Without being wavelength-converted the light output from the amplification optical fiber by the seed laser light and the excitation light that are provided between the amplification optical fiber and the output unit and have a small spire value in the preliminary excitation state, A wavelength converter for wavelength-converting the laser light output from the amplification optical fiber by the seed laser light and the excitation light in the output state;
Provided between the wavelength converter and the output unit, when light having the same wavelength band as the seed laser light is input to the wavelength converter, the light that is wavelength-converted in the wavelength converter is transmitted, A wavelength selective filter that suppresses transmission of light that is not wavelength-converted in the wavelength converter;
The fiber laser device according to claim 3, further comprising:   6. The fiber laser device according to claim 1, wherein an intensity of the excitation light in the preliminary excitation state is equal to or less than an intensity of the excitation light in the output state.

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