JP2014216497A - Optical circuit device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical circuit device capable of improving long-term reliability when monitoring fluctuation of output power.SOLUTION: A fiber laser device 1 includes excitation light sources 20A, 20B for supplying excitation light, and an optical resonator 10 equipped with an amplifying optical fiber 12. The amplifying optical fiber 12 is added with a first rare earth element (Yb) which generates laser oscillation light in a 1000 nm band upon receiving excitation light and a second rare earth element (Er) which generates monitor light in a 1500 nm band. The fiber laser device 1 includes a light radiation part 40 formed with an optical fiber 30 provided inside the optical resonator 10 or between the optical resonator 10 and the laser emitting part 32. The light radiation part 40 has a curvature radius such that no laser oscillation light is substantially radiated outside but monitor light is radiated outside. The fiber laser device 1 further includes a light detector 50 which detects intensity of the light radiated from the light radiation part 40.

Description

  The present invention relates to an optical circuit device, and more particularly to an optical circuit device that can be used as a fiber laser.

In recent years, fiber lasers have been increased in output, and fiber lasers having a single mode kilowatt output from a single optical resonator, or fibers having a multimode combined output of 10 kilowatts or more by combining a plurality of light sources. Lasers have been developed. By replacing laser devices such as solid-state lasers and CO ₂ lasers that have been used so far with such high-power fiber lasers, fiber lasers are increasingly used in the metal processing field.

  In processing using such a fiber laser, stable processing quality is required, but if the output power of the fiber laser changes, the processing quality is also affected. Factors that cause fluctuations in the output power of the fiber laser include the drive environment (mainly temperature) of the device, the failure of one or more pump light sources among the multiple pump light sources mounted on the fiber laser, and reflection from the workpiece. And the effect of light returning to the optical resonator. Therefore, in the conventional fiber laser, in order to obtain stable processing quality, the fluctuation of the output power of the fiber laser is monitored, and the correction control of the device is performed so that the output power becomes a predetermined value when the output power fluctuates. It is carried out.

  Here, as a method of monitoring the power of light propagating in the optical fiber, the power of light propagating in the optical fiber is detected by bending the part of the optical fiber and detecting the intensity of the light leaking from the curved part. A monitoring method is known (see, for example, Patent Documents 1 and 2). Here, the bending loss of the optical fiber has a characteristic that the shorter the wavelength, the smaller the light with the same radius of curvature. Therefore, in order to leak, for example, 1000 nm band laser oscillation light output from the fiber laser through the curved portion of the optical fiber, it is necessary to sufficiently reduce the radius of curvature of the curved portion.

  However, since a residual stress is generated in the curved portion according to the radius of curvature, the optical fiber may be broken at the curved portion when the radius of curvature of the curved portion is small. Therefore, there is a problem that the long-term reliability of the optical fiber cannot be guaranteed as the radius of curvature decreases. In addition, not only the laser oscillation light output from the fiber laser but also the light reflected from the workpiece and returning to the fiber laser is emitted at the curved portion, so only measuring the light leaking from the curved portion outputs it from the fiber laser. It is impossible to accurately monitor the output power of the laser oscillation light.

JP 2001-159580 A Japanese Patent Laid-Open No. 5-224044

  The present invention has been made in view of such problems of the prior art, and an object thereof is to provide an optical circuit device capable of improving long-term reliability when monitoring fluctuations in output power. To do.

  According to one embodiment of the present invention, an optical circuit device capable of improving long-term reliability when monitoring fluctuations in output power is provided. The optical circuit device includes a pumping light source that supplies pumping light, a first rare earth element that receives the pumping light supplied from the pumping light source and generates laser oscillation light in a first wavelength band, and the supply of the pumping light. And an amplification optical fiber to which a second rare earth element that generates monitoring light in a second wavelength band that is longer than the first wavelength band is added, and oscillates the laser oscillation light. An optical resonator, a laser emitting portion for emitting the laser oscillation light, and a light emitting portion formed by an optical fiber provided inside the optical resonator or between the optical resonator and the laser emitting portion. Prepare. The light emitting section has a radius of curvature such that the light in the first wavelength band is not substantially radiated to the outside, but the light in the second wavelength band is radiated to the outside. The optical circuit device further includes a photodetector that detects the intensity of light emitted from the light emitting unit.

  The light emitting unit may be disposed between the laser emitting unit and the amplification optical fiber.

  The optical circuit device may further include a control unit that controls the power of pumping light from the pumping light source based on the intensity of the light detected by the photodetector. In this case, the control unit compares the intensity of the light detected by the photodetector with a preset reference value, and controls the power of the excitation light from the excitation light source based on the comparison result. May be.

  The light emitting part may be constituted by a single part having the radius of curvature, or may be constituted by a plurality of parts having the radius of curvature.

  The optical circuit device may include an additional light emitting unit formed by an optical fiber provided between the light emitting unit and the laser emitting unit. The additional light radiating section has a radius of curvature such that the light in the first wavelength band is not substantially radiated to the outside, but the light in the second wavelength band is radiated to the outside.

  The optical circuit device may further include a monitoring light resonator that oscillates the monitoring light in order to increase the amount of the monitoring light in the light emitting unit.

  Further, light generated by spontaneous emission or stimulated emission of the second rare earth element due to energy transition from the first rare earth element to the second rare earth element due to the supply of the excitation light is used as the monitoring light. be able to. Alternatively, when the absorption band of the first rare earth element and the absorption band of the second rare earth element partially overlap each other, the second rare earth element caused by the supply of the excitation light Light generated by spontaneous emission or stimulated emission can be used as the monitoring light.

  Yb can be used as the first rare earth element, and Er can be used as the second rare earth element. In this case, the wavelength of the excitation light is preferably 970 nm to 980 nm. Further, Tm can be used as the first rare earth element, and Ho can be used as the second rare earth element, or Yb can be used as the first rare earth element and Pr can be used as the second rare earth element.

  The concentration of the second rare earth element is preferably lower than the concentration of the first rare earth element.

  According to the present invention, by using an amplification optical fiber to which two kinds of rare earth elements are added, in addition to laser oscillation light, monitoring light having a longer wavelength can be generated. The light radiating section has a radius of curvature so that light in the wavelength band of the laser oscillation light is not substantially radiated to the outside, but light in the wavelength band of the monitoring light is radiated to the outside. Only the monitoring light can be emitted from the section. Since the intensity of the monitoring light has a correlation with the output power of the optical circuit device, the intensity of the emitted monitoring light is detected by a photodetector so that the intensity of the laser oscillation light can be detected without detecting the intensity of the laser oscillation light. Changes in output power can be monitored.

  In this case, since the wavelength band of the monitoring light is longer than the wavelength band of the laser oscillation light, the radius of curvature of the light emitting portion can be increased as compared with the case where the laser oscillation light is emitted. Therefore, the risk of breakage of the optical fiber can be reduced, and the long-term reliability of the optical circuit device can be improved. In addition, a part of the laser oscillation light emitted from the laser emission part may be reflected by the object to be processed and return to the optical circuit device. However, the returned laser oscillation light is substantially transmitted from the light emission part to the outside. Therefore, accurate and stable detection by the photodetector can be realized without being affected by the returning laser oscillation light.

It is a schematic diagram which shows the structure of the optical circuit device in the 1st Embodiment of this invention. FIG. 2 is an energy transition diagram of an amplification optical fiber in the optical circuit device of FIG. 1. It is a graph which shows the relationship between the bending diameter of an optical fiber, and the bending loss per winding. It is a schematic diagram which shows the structure of the optical circuit device in the 2nd Embodiment of this invention. It is a schematic diagram which shows the structure of the optical circuit device in the 3rd Embodiment of this invention. It is a schematic diagram which shows the structure of the optical circuit device in the 4th Embodiment of this invention. It is a figure which shows the loss wavelength characteristic of the optical fiber to which Yb and Er were added.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of an optical circuit device according to the present invention will be described in detail with reference to FIGS. 1 to 7, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic diagram showing a configuration of a fiber laser device 1 as an optical circuit device according to the first embodiment of the present invention. As shown in FIG. 1, the fiber laser device 1 according to the present embodiment includes an optical resonator 10, a plurality of pumping light sources 20A for introducing pumping light into the optical resonator 10 from one of the optical resonators 10, and a pumping light source 20A. A combiner 22A that combines the excitation light from the optical resonator 10, a plurality of excitation light sources 20B that introduce the excitation light from the other of the optical resonators 10, and a combiner 22B that combines the excitation light from the excitation light source 20B. It has.

  The optical resonator 10 includes an amplification optical fiber 12, and a high reflection fiber Bragg grating (FBG) 14 and a low reflection FBG 16 connected to both sides of the amplification optical fiber 12. A single clad optical fiber (delivery fiber) 30 extending to the outside of the resonator 10 is connected to the combiner 22B, and laser light from the amplification optical fiber 12 is processed at the end of the optical fiber 30, for example, A laser emitting portion 32 that emits toward an object is provided.

  At least two kinds of rare earth elements are added to the core of the amplification optical fiber 12, and in this embodiment, the amplification optical fiber 12 to which Yb (ytterbium) and Er (erbium) are added is used. In this case, the Er concentration is preferably lower than the Yb concentration. For example, it adds so that the ratio of Yb and Er may be set to 30: 1. The amplification optical fiber 12 preferably has a double clad structure including an inner clad and an outer clad lower than the refractive index of the inner clad.

  As the excitation light sources 20A and 20B, for example, a high-power multimode semiconductor laser (LD) having a wavelength of 915 nm can be used. The excitation light from the excitation light source 20A is combined by the combiner 22A and introduced into the amplification optical fiber 12 from the highly reflective FBG 14 side. Similarly, the pumping light from the pumping light source 20B is combined by the combiner 22B and introduced into the amplification optical fiber 12 from the low reflection FBG 16 side.

  In the present embodiment, the excitation light sources 20A and 20B and the combiners 22A and 22B are provided on both the high reflection FBG 14 side and the low reflection FBG 16 side, which is a bidirectional excitation type fiber laser device, but the high reflection FBG 14 It is good also as installing an excitation light source and a combiner only in any one of the side and the low reflection FBG16 side.

  The high reflection FBG 14 and the low reflection FBG 16 in the present embodiment are configured to reflect light having a wavelength of 1000 nm to 1100 nm corresponding to the wavelength of the laser oscillation light. The reflectance of the high reflection FBG 14 is preferably 90% to 100%, and the reflectance of the low reflection FBG 16 is preferably 30% or less. In the present embodiment, an example in which FBG is used as the reflecting means for causing laser oscillation in the optical resonator 10 will be described. However, a mirror can also be used as the reflecting means.

  In such a configuration, when excitation light having a wavelength of, for example, 915 nm is introduced from the excitation light sources 20A and 20B into the amplification optical fiber 12, Yb of the amplification optical fiber 12 is excited, and emitted light having a wavelength of 1000 nm band is emitted. This Yb emission light is laser-oscillated at a wavelength of 1000 nm band by the high reflection FBG 14 and the low reflection FBG 16 arranged so as to satisfy a predetermined resonance condition. A part of the laser oscillation light generated in the optical resonator 10 is reflected by the low reflection FBG 16 and returns to the amplification optical fiber 12, but most of the laser oscillation light passes through the low reflection FBG 16 and is emitted from the laser emission unit 32. The

By the way, two kinds of rare earth elements Yb and Er are added to the core of the amplification optical fiber 12 in the present embodiment. FIG. 2 is an energy transition diagram of the amplification optical fiber 12. As shown in FIG. 2, it is known that an energy transition occurs from the energy level of ² F _5/2 of Yb ³⁺ to the energy level of ⁴ I _15/2 of Er ³⁺ (for example, WLBarnes et al. al. "Er ³⁺ -Yb ³⁺ and Er ³⁺ Doped Fiber Lasers," Journal of Lightwave Technology, Vol. 7, No. 10, October 1989, pp. 1461-1465). Therefore, the excitation light source 20A, the higher the energy levels of Yb ³⁺ by the excitation light from 20B, part of the energy transitions to Er ^3+, the energy levels of the Er ³⁺ is ⁴ I _11/2 Excited. The excited Er ³⁺ relaxes to ⁴ I _13/2 in a non-radiative process, emits amplified spontaneous emission (ASE) in the 1500 nm band, and transitions to the ground state ⁴ I _15/2 . Here, the spontaneous emission light amplified from Er thus emitted or the stimulated emission light generated by the spontaneous emission light is referred to as monitoring light.

  Thus, in the present embodiment, among the rare earth elements added to the amplification optical fiber 12, Yb has a role of amplifying light as a gain medium for laser oscillation light, and Er is a wavelength band of laser oscillation light. It has a role of emitting monitoring light having a longer wavelength than that. For this reason, by supplying excitation light from the excitation light sources 20A and 20B to the amplification optical fiber 12, laser oscillation light in the 1000 nm band (first wavelength band) is generated from Yb, and 1500 nm band (second) from Er. Monitoring wavelength light is generated. Here, since the high reflection FBG 14 and the low reflection FBG 16 are not configured to reflect 1500 nm band light, the monitoring light passes through the high reflection FBG 14 and the low reflection FBG 16.

  As shown in FIG. 1, the optical fiber 30 between the laser emitting portion 32 and the combiner 22B is formed with a light emitting portion including a loop portion 40 having a predetermined radius of curvature. In the vicinity of the loop portion 40, a photodetector 50 is provided that detects the intensity of light emitted to the outside due to the bending of the optical fiber in the loop portion 40. For example, a photodetector can be used as the photodetector 50. Further, the fiber laser device 1 includes a control unit 60 that controls the power of the pumping light from the pumping light sources 20A and 20B based on the intensity of the light detected by the photodetector 50.

  Here, the laser oscillation light has a shorter wavelength than the monitoring light, and has a smaller MFD (Mode Field Diameter) and less evanescent light component than the monitoring light. For this reason, laser oscillation light is strong against radiation caused by bending of the optical fiber, and in order to radiate laser oscillation light to the outside by bending the optical fiber, it is necessary to reduce the radius of curvature of the optical fiber. However, the smaller the radius of curvature of the optical fiber, the greater the risk that the optical fiber will break, making it impossible to guarantee long-term reliability of the optical fiber. In this embodiment, such a problem is solved by using monitoring light having a wavelength longer than that of laser oscillation light as described below.

  FIG. 3 is a graph showing the relationship between the bending diameter of an optical fiber having a core diameter of 10 μm and a relative refractive index difference Δ of 0.35% and bending loss per turn. The solid line in FIG. 3 indicates the bending loss of light (laser oscillation light) having a wavelength of 1080 nm, and the broken line indicates the bending loss of light (monitoring light) having a wavelength of 1550 nm. As can be seen from the graph of FIG. 3, the longer the wavelength, the greater the bending loss at the same radius of curvature. By using this characteristic, by appropriately bending the loop portion 40, short wavelength light (laser oscillation light) is not emitted from the loop portion 40 to the outside substantially, and long wavelength light (monitoring light) is externally emitted. It is possible to radiate. At this time, the laser oscillation light propagates inside the core of the loop unit 40. Here, in this specification, that light does not substantially radiate from the light emitting portion means that the intensity of light emitted from the light radiating portion to the outside is 1 mW or less.

  In this embodiment, by using the amplification optical fiber 12 to which two kinds of rare earth elements Yb and Er are added, monitoring light having a longer wavelength is generated in addition to the laser oscillation light. Of the laser oscillation light and the monitoring light, the monitoring light having a long wavelength is emitted to the outside by bending the loop portion 40. Since the intensity of the monitoring light has a correlation with the output power of the fiber laser apparatus 1, the fluctuation of the output power of the fiber laser apparatus 1 can be monitored by detecting the intensity of the monitoring light emitted from the loop unit 40. it can.

  In other words, the loop portion 40 is configured to have a radius of curvature such that the bending loss of the laser oscillation light is sufficiently smaller than the bending loss of the monitoring light. Thereby, from the loop part 40, laser oscillation light is not substantially radiated | emitted outside, but monitoring light will be radiated | emitted outside. In this case, even if the laser oscillation light is slightly emitted within a range that is not substantially emitted from the loop portion 40, the power of the laser oscillation light is preferably 5% or less of the power of the monitoring light. .

For example, in FIG. 3, when the bending diameter of the optical fiber is 75 mm, the bending loss with respect to light having a wavelength of 1080 nm (laser oscillation light) is 1.4 × 10 ⁻⁶ dB per turn, and light having a wavelength of 1550 nm. The bending loss for (monitoring light) is 7.5 × 10 ⁻¹ dB per roll. As will be described later, even if the Yb and Er concentrations are adjusted and the laser oscillation power is 1 kW and the monitoring light power is 10 ⁻⁴ times 100 mW, the laser oscillation light emitted by the bending of the loop portion 40 The power per turn of the light is 0.32 mW, and the power per turn of the monitoring light is 15.9 mW. Thus, since the power per volume of the laser oscillation light is as low as about 2% of the power per volume of the monitoring light, the monitoring light having a sufficient amount of light is looped without substantially emitting the laser oscillation light to the outside. The light can be emitted from the portion 40.

  The photodetector 50 detects the intensity of the monitoring light emitted from the loop unit 40, and the control unit 60 uses the excitation light from the excitation light sources 20A and 20B based on the intensity of the monitoring light detected by the photodetector 50. To control the power. For example, the control unit 60 compares the detected intensity of the monitoring light with a preset reference value, and when the difference between the detected intensity of the monitoring light and the reference value becomes a certain value or more, the fiber laser device It can be determined that the output power fluctuation of 1 has occurred. And the control part 60 can correct | amend output power by adjusting the drive current to excitation light source 20A, 20B, and can stabilize output power.

  As described above, in this embodiment, the loop portion 40 has a radius of curvature so that the light in the wavelength band of the laser oscillation light is not substantially radiated to the outside, but the light in the wavelength band of the monitoring light is radiated to the outside. Thus, only the monitoring light can be emitted from the loop unit 40. By detecting the intensity of the emitted monitoring light by the photodetector 50, it is possible to monitor the fluctuation of the output power of the fiber laser device 1 without detecting the intensity of the laser oscillation light. In this case, since the wavelength band of the monitoring light is longer than the wavelength band of the laser oscillation light, the radius of curvature of the loop portion 40 can be increased as compared with the case where the laser oscillation light is emitted. Therefore, the risk of breakage of the optical fiber can be reduced, and the long-term reliability of the fiber laser device 1 can be improved. Further, when the laser oscillation light is reflected by the workpiece and returns to the fiber laser device 1, even if the return light varies depending on the material of the workpiece and the processing status, the return light Is not substantially radiated to the outside from the loop part (light emitting part) 40, so that accurate and stable detection by the photodetector 50 can be realized without being affected by the return light.

  Here, it is preferable to add Er to the core of the amplification optical fiber 12 at a concentration sufficiently lower than Yb. When the concentration of Er having the role of emitting the monitoring light is high, the energy transition also increases, the energy contributing to the generation of the laser oscillation light is reduced, and the efficiency of the laser oscillation is reduced. On the other hand, it is necessary to add Er to such an extent that monitoring light can be detected. The amount of these rare earth elements depends on the necessary laser oscillation light power (efficiency), the energy transition probability between the rare earth elements, the bending loss in the loop section 40 at the wavelength of the monitoring light, the amount of light necessary for the photodetector 50, and the like. It is adjusted to the optimum value.

  FIG. 1 shows an example in which the light radiating portion is constituted by a single loop portion 40, but the light radiating portion may be constituted by a plurality of portions having the above-described radius of curvature. By configuring the light emitting section with such a plurality of portions, the amount of monitoring light emitted from the light emitting section can be increased, and the accuracy of detection of monitoring light by the photodetector 50 can be improved. . Further, in the example shown in FIG. 1, an example in which the light emitting portion is configured by a loop portion is shown. However, the radius of curvature is set so that the laser oscillation light is not substantially emitted to the outside but the monitoring light is emitted to the outside. If the light emitting portion includes a portion having the same, it is not always necessary to form a loop. Furthermore, a plurality of light emitting portions themselves may be provided.

  FIG. 4 is a schematic diagram showing a configuration of a fiber laser device 101 as an optical circuit device according to the second embodiment of the present invention. As shown in FIG. 4, in the fiber laser device 101 of this embodiment, the optical fiber 30 between the loop portion 40 and the laser emitting portion 32 is provided with additional light radiation including a loop portion 170 having a predetermined radius of curvature. The part is formed. The loop portion 170 of the additional light emitting portion, like the light emitting portion loop portion 40, does not substantially emit light in the wavelength band of the laser oscillation light to the outside, but does not emit light in the wavelength band of the monitoring light. It has a radius of curvature that is radiated.

  A part of the monitoring light emitted from the laser emitting part may be reflected by the object to be processed and return to the fiber laser device 101. In this embodiment, the loop part (additional light emitting part) 170 is provided. Since it is provided, the returned monitoring light is radiated to the outside by the loop unit 170, and a part thereof is attenuated before reaching the loop unit 40. Therefore, since the component of the monitoring light reflected from the object to be processed and returned from the light emitted from the loop unit 40 can be reduced, the accuracy of detection by the photodetector 50 can be increased.

  Although not shown, a photodetector that detects the intensity of light emitted from the loop unit 170 may be provided in the vicinity of the loop unit (additional light emitting unit) 170. By providing such a photodetector, it is possible to detect the intensity of the monitoring light reflected and returned by the object to be processed, and as a result, the laser oscillation light reflected by the object to be processed and returned to the fiber laser device 101 is detected. Can be monitored.

  FIG. 5 is a schematic diagram showing a configuration of a fiber laser device 201 as an optical circuit device according to the third embodiment of the present invention. As shown in FIG. 5, the fiber laser device 201 according to the present embodiment includes a monitoring optical resonator 210 that oscillates the monitoring light. The monitoring optical resonator 210 includes a high reflection FBG 214 and a low reflection FBG 216 connected to both sides of the amplification optical fiber 12. The high reflection FBG 214 and the low reflection FBG 216 are configured to reflect light having a wavelength of 1500 nm to 1600 nm corresponding to the wavelength of the monitoring light. The reflectance of the high reflection FBG 214 is preferably 90% to 100%, and the reflectance of the low reflection FBG 216 is preferably 30% or less. In the present embodiment, an example in which FBG is used as the reflecting means for causing the monitoring light to oscillate in the monitoring light resonator 210 will be described. However, a mirror may be used as the reflecting means.

  As described above, in this embodiment, since the monitoring light generated in the amplification optical fiber 12 can be laser-oscillated by the monitoring optical resonator 210, the monitoring light emitted from the loop part (light emitting part) 40 can be reduced. The amount of light can be increased, and the accuracy of detection of monitoring light by the photodetector 50 can be improved.

  The positions of the high reflection FBG 214 and the low reflection FBG 216 are not limited to those shown in the figure, and may be anywhere on both sides of the amplification optical fiber 12.

  FIG. 6 is a schematic diagram showing a configuration of a fiber laser device 301 as an optical circuit device according to the fourth embodiment of the present invention. In the first embodiment shown in FIG. 1, the loop portion (light emitting portion) 40 is formed in the optical fiber 30 extending from the combiner 22B to the outside of the optical resonator 10, but the position where the light emitting portion is formed is resonant. It may be anywhere inside the resonator 10 or between the resonator 10 and the laser emitting portion 32. The fourth embodiment shown in FIG. 6 shows an example in which a loop part (light emitting part) 40 is formed inside the resonator 10.

  In the above-described embodiment, as two types of rare earth elements added to the amplification optical fiber 12, Yb (first rare earth element) that generates laser oscillation light upon receiving excitation light supplied from an excitation light source, and Yb Er (second rare earth element) that generates monitoring light having a longer wavelength than laser oscillation light due to energy transition is used, but the combination of these first rare earth element and second rare earth element is limited to this. is not. As a combination of rare earth elements having similar characteristics, a combination of Tm (thulium) as the first rare earth element, a combination of Ho (holmium) as the second rare earth element, or Yb (ytterbium) as the first rare earth element, As the rare earth element 2, a combination of Pr (praseodymium) can be considered.

  In the above-described embodiment, the monitoring light is emitted from Er using the energy transition from Yb to Er generated by supplying the excitation light. However, the monitoring light can be generated from Er by other methods. . FIG. 7 shows loss wavelength characteristics of an optical fiber to which Yb and Er are added and loss wavelength characteristics of an optical fiber to which Er is added. As shown in FIG. Both absorption bands overlap at a wavelength of 980 nm. Therefore, when excitation light having a wavelength of 970 nm to 980 nm is used, both Yb and Er cause spontaneous emission and stimulated emission accompanying spontaneous emission. Light from the Yb has a wavelength of 1000 nm, and from Er has a wavelength of 1500 nm. Light can be emitted, and spontaneous emission light of Er and stimulated emission light accompanying spontaneous emission can be used as monitoring light. As described above, the laser oscillation light and the monitoring light can be generated by utilizing the spontaneous emission of two kinds of rare earth elements and the stimulated emission accompanying the spontaneous emission.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and it goes without saying that the present invention may be implemented in various forms within the scope of the technical idea. For example, in each of the above-described embodiments, the fiber laser device has been described as an example of the optical circuit device. However, the present invention is not limited to the fiber laser, and for example, the present invention can be applied to an optical fiber amplifier. It is. It goes without saying that the above-described embodiments can be appropriately combined.

DESCRIPTION OF SYMBOLS 1 Fiber laser apparatus 10 Optical resonator 12 Optical fiber for amplification 14 High reflection FBG
16 Low reflection FBG
20A, 20B Excitation light source 22A, 22B Combiner 30 Optical fiber 32 Laser emission part 40 Loop part (light emission part)
101 Fiber laser device 170 Loop part (additional light radiation part)
201 Fiber laser device 210 Monitoring optical resonator 214 High reflection FBG
216 Low reflection FBG
301 fiber laser device 330 optical fiber

Claims (13)

An excitation light source for supplying excitation light;
A first rare earth element that generates laser oscillation light in a first wavelength band upon receiving excitation light supplied from the excitation light source; and a longer wavelength than the first wavelength band due to the supply of the excitation light. An optical resonator that includes an amplification optical fiber to which a second rare earth element that generates monitoring light in a second wavelength band is added, and that oscillates the laser oscillation light;
A laser emitting section for emitting the laser oscillation light;
A light emitting section formed by an optical fiber provided inside or between the optical resonator and the laser emitting section, wherein the light in the first wavelength band is radiated substantially outside. A light emitting portion having a radius of curvature such that the light in the second wavelength band is emitted to the outside,
A photodetector for detecting the intensity of light emitted from the light emitting section;
An optical circuit device comprising:   The optical circuit device according to claim 1, wherein the light emitting unit is disposed between the laser emitting unit and the amplification optical fiber.   3. The optical circuit device according to claim 1, further comprising a control unit configured to control power of pumping light from the pumping light source based on the intensity of the light detected by the photodetector.   The control unit compares the intensity of the light detected by the photodetector with a preset reference value, and controls the power of the excitation light from the excitation light source based on the comparison result. The optical circuit device according to claim 3.   5. The optical circuit device according to claim 1, wherein the light emitting portion includes a plurality of portions having the curvature radius.   An additional light emitting portion formed by an optical fiber provided between the light emitting portion and the laser emitting portion, wherein the light in the first wavelength band is not substantially radiated to the outside, but the second 6. The optical circuit device according to claim 1, further comprising an additional light radiating unit having a radius of curvature such that light in the wavelength band is radiated to the outside.   The optical circuit device according to claim 1, further comprising a monitoring optical resonator that oscillates the monitoring light.   The monitoring light is generated by spontaneous emission or stimulated emission of the second rare earth element due to energy transition from the first rare earth element to the second rare earth element due to the supply of the excitation light. The optical circuit device according to any one of claims 1 to 7.   The absorption band of the first rare earth element and the absorption band of the second rare earth element partially overlap each other, and the monitoring light is the second rare earth element resulting from the supply of the excitation light. The optical circuit device according to claim 1, wherein the optical circuit device is generated by spontaneous emission or stimulated emission.   10. The optical circuit device according to claim 1, wherein the first rare earth element is Yb, and the second rare earth element is Er.   The optical circuit device according to claim 10, wherein a wavelength of the excitation light is 970 nm to 980 nm.   The optical circuit device according to claim 1, wherein a concentration of the second rare earth element is lower than a concentration of the first rare earth element.   13. The optical circuit device according to claim 1, wherein the first rare earth element is Tm and the second rare earth element is Ho.

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