Abstract: A fiber laser device includes a pumping light source, an amplifying fiber, an input side fiber fusion-spliced on an input side of the amplifying fiber and formed with a HR-FBG, an output side fiber fusion-spliced on an output side of the amplifying fiber and formed with an OC-FBG having a reflectivity smaller than that of the HR-FBG, an output end, and a mode filter, wherein the input side fiber or an intermediate fiber disposed between the amplifying fiber and the input side fiber is fusion-spliced with the amplifying fiber via a fusion splice portion, and at least a portion of the mode filter is disposed in a region between the fusion splice portion and a position separated from the fusion splice portion by a coherence length of beating caused by mode interference of signal light propagating in the amplifying fiber.

Abstract: A filter device includes: an optical fiber that allows light having a predetermined wavelength to propagate in multimode; a first higher-order mode filter that removes at least part of the light in any higher order mode than a predetermined mode in the light in the multimode propagating in the optical fiber; and a fiber Bragg grating that transmits the light having the predetermined wavelength and reflects light having a particular wavelength longer than the predetermined wavelength.

Abstract: An optical fiber connector includes: amplifying fibers in which an active element activated by excitation light is added to a core of each of the amplifying fibers. The amplifying fibers are connected together such that an absorption amount of excitation light per unit length increases with an increase of a distance from an incident end of the excitation light. A mode field diameter of laser light propagating through the core is same among the amplifying fibers.

Abstract: An optical fiber includes: a center core; an inner ring layer, located outside of the center core in a radial direction, that has a refractive index lower than a refractive index of the center core; an outer core, located outside of the inner ring layer in the radial direction, that has a refractive index higher than the refractive index of the inner ring layer; and an outer ring layer, located outside of the outer core in the radial direction, that has a refractive index lower than the refractive index of the outer core. A relative refractive index difference ?CF between the center core and the inner ring layer varies along a longitudinal direction such that the relative refractive index difference ?CF at a location along the longitudinal direction is smaller than a relative refractive index difference ?PF between the outer core and the outer ring layer.

Abstract: A filter device includes: an optical fiber that allows light having a predetermined wavelength to propagate in multimode; a first higher-order mode filter that removes at least part of the light in any higher order mode than a predetermined mode in the light in the multimode propagating in the optical fiber; and a fiber Bragg grating that transmits the light having the predetermined wavelength and reflects light having a particular wavelength longer than the predetermined wavelength.

Abstract: An optical device includes a core, a first cladding, a second cladding, a slanted fiber Bragg grating, and a high refractive index material. The first cladding covers the core and has a lower refractive index than the core. The second cladding covers the first cladding and has a lower refractive index than the first cladding. The slanted fiber Bragg grating is formed in the core and couples stimulated Raman scattering light, propagating through the core, to the first cladding. The high refractive index material has a higher refractive index than the second cladding and covers an outer peripheral surface of a removal portion where the second cladding is removed and a portion of the first cladding that covers the region where the slanted fiber Bragg grating is formed in the core.

Abstract: A fiber laser device includes a pumping light source, an amplifying fiber, an input side fiber fusion-spliced on an input side of the amplifying fiber and formed with a HR-FBG, an output side fiber fusion-spliced on an output side of the amplifying fiber and formed with an OC-FBG having a reflectivity smaller than that of the HR-FBG, an output end, and a mode filter, wherein the input side fiber or an intermediate fiber disposed between the amplifying fiber and the input side fiber is fusion-spliced with the amplifying fiber via a fusion splice portion, and at least a portion of the mode filter is disposed in a region between the fusion splice portion and a position separated from the fusion splice portion by a coherence length of beating caused by mode interference of signal light propagating in the amplifying fiber.

Abstract: An optical device includes: a thermal conductor; a support that is separated from the thermal conductor and that has a coefficient of thermal expansion lower than a coefficient of thermal expansion of the thermal conductor; and an optical fiber that thermally contacts with the thermal conductor via a resin covering a jacket-removed section of the optical fiber and that is fixed to the support in each of two jacketed sections of the optical fiber, wherein the two jacketed sections are adjacent to the jacket-removed section.

Abstract: An optical fiber combiner 1 has: a plurality of input optical fibers 20; a plurality of divergence angle reducing members 50 which lights emitted from the respective input optical fibers 20 enter and which emits the lights from the input optical fibers 20 at divergence angles made lower than divergence angles upon entrance; a bridge fiber 30 which the lights emitted from the respective divergence angle reducing members 50 enter and which has a tapered portion 34 which has a portion in which the lights propagate and a diameter of which is gradually reduced apart from a divergence angle reducing member 50 side; and an output optical fiber 40 which a light emitted from a side of the bridge fiber 30 opposite to the divergence angle reducing member 50 side enters.

Abstract: An optical fiber combiner 1 has: a plurality of input optical fibers 20; a plurality of divergence angle reducing members 50 which lights emitted from the respective input optical fibers 20 enter and which emits the lights from the input optical fibers 20 at divergence angles made lower than divergence angles upon entrance; a bridge fiber 30 which the lights emitted from the respective divergence angle reducing members 50 enter and which has a tapered portion 34 which has a portion in which the lights propagate and a diameter of which is gradually reduced apart from a divergence angle reducing member 50 side; and an output optical fiber 40 which a light emitted from a side of the bridge fiber 30 opposite to the divergence angle reducing member 50 side enters.

Abstract: [Object] An object of the invention is to provide a fiber laser device capable of stabilizing intensity of laser light output therefrom. [Means to attain the object] A fiber laser device 100 includes: an pumping light source 11 configured to output pumping light; a rare earth-doped fiber 20 to which the pumping light is input; and a first FBG 30 formed on one side of the rare earth-doped fiber 20 and a second FBG 40 formed on the other side of the rare earth-doped fiber 20 that are configured to reflect light amplified in the rare earth-doped fiber 20, wherein the second FBG 40 has a reflectance lower than that of the first FBG 30, a reflection wavelength band in that of the first FBG 30, and Bragg wavelength on short wavelength side of Bragg wavelength of the first FBG 30.

Abstract: There are provided an amplification optical fiber, and an optical fiber amplifier and a resonator using the same capable of outputting light of high beam quality even when a higher-order mode that is axially symmetric is excited in addition to LP01 mode. An amplification optical fiber 50 includes: a core 51; a clad 52 coating the core 51; and an outer clad 53 coating the clad 52, wherein the core 51 has a larger refractive index than the clad 52, the core 51 allows light having a predetermined wavelength to propagate in at least LP01 mode and LP02 mode, and in the core 51, active element that stimulates to emit light of the predetermined wavelength is doped at a higher concentration at a position where an intensity of the LP02 mode becomes zero than center of the core 51.

Abstract: Provided is a fiber laser including a mode filter for selectively attenuating, among modes included in laser light propagating through a multi-mode fiber, any mode other than a radially polarized mode. Among the modes included in the laser light propagating through the multi-mode fiber, the fiber laser causes the radially polarized mode to resonate, so as to emit radially polarized laser light. The mode filter includes a long-period fiber grating obtained by writing, to a multi-mode fiber capable of guiding the radially polarized mode, a grating for selectively attenuating any waveguide mode other than the radially polarized mode.

Abstract: A fiber laser light source is provided with a laser resonator including a pair of fiber gratings optically connected to a fiber in a state that the fiber is interposed between the paired fiber gratings. The reflection center wavelength of a laser-exit side fiber grating, out of the paired fiber gratings, lies in a wavelength range where the reflectance of a fiber grating, out of the paired fiber gratings, closer to the pump laser light source is not smaller than 80% but not larger than 98%.

Abstract: There are provided an amplification optical fiber, and an optical fiber amplifier and a resonator using the same capable of outputting light of high beam quality even when a higher-order mode that is axially symmetric is excited in addition to LP01 mode. An amplification optical fiber 50 includes: a core 51; a clad 52 coating the core 51; and an outer clad 53 coating the clad 52, wherein the core 51 has a larger refractive index than the clad 52, the core 51 allows light having a predetermined wavelength to propagate in at least LP01 mode and LP02 mode, and in the core 51, active element that stimulates to emit light of the predetermined wavelength is doped at a higher concentration at a position where an intensity of the LP02 mode becomes zero than center of the core 51.

Abstract: Provided is a fiber laser including a mode filter for selectively attenuating, among modes included in laser light propagating through a multi-mode fiber, any mode other than a radially polarized mode. Among the modes included in the laser light propagating through the multi-mode fiber, the fiber laser causes the radially polarized mode to resonate, so as to emit radially polarized laser light. The mode filter includes a long-period fiber grating obtained by writing, to a multi-mode fiber capable of guiding the radially polarized mode, a grating for selectively attenuating any waveguide mode other than the radially polarized mode.

Abstract: An object of the invention is to provide a fiber laser device capable of stabilizing intensity of laser light output therefrom. A fiber laser device 100 includes: an pumping light source 11 configured to output pumping light; a rare earth-doped fiber 20 to which the pumping light is input; and a first FBG 30 formed on one side of the rare earth-doped fiber 20 and a second FBG 40 formed on the other side of the rare earth-doped fiber 20 that are configured to reflect light amplified in the rare earth-doped fiber 20, wherein the second FBG 40 has a reflectance lower than that of the first FBG 30, a reflection wavelength band in that of the first FBG 30, and Bragg wavelength on short wavelength side of Bragg wavelength of the first FBG 30.

Abstract: A fiber laser light source is provided with a laser resonator including a pair of fiber gratings optically connected to a fiber in a state that the fiber is interposed between the paired fiber gratings. The reflection center wavelength of a laser-exit side fiber grating, out of the paired fiber gratings, lies in a wavelength range where the reflectance of a fiber grating, out of the paired fiber gratings, closer to the pump laser light source is not smaller than 80% but not larger than 98%.

Abstract: An electric power tool includes a tool body having a rotor, an inner cylindrical body and outer cylindrical body. The rotor is provided with a ventilation space therearound, a body part and a brush contact part, and housed in the inner cylindrical body. The inner cylindrical body is inserted in the outer cylindrical body which has a plurality of groove-like ventilation spaces on its inner face. The rotation of a fan fitted on the rotor circulates air within the tool body through the ventilation spaces so as to cool down the body part and the brush contact part of the rotor. The electric power tool has the rotor with which not only the body part but also other heated parts are fully cooled down. The electric power tool enhances heat dissipation efficiency from a motor case, enables efficient cooling of heated parts and has a long durability.

Abstract: A tool container includes a receiving case with its upper end open and an outer bag with a hang portion, and the receiving case is insertable to and removable from the outer bag. The invention provides a tool container in which, in case of changing articles in the tool container, a worker does not have to put his or her hand or hands into the tool container, or the tool container does not have to be turned upside down, which prevents the worker from being wounded in the hand and which prevents taken-out articles from being damaged or scattering. Further articles in a pocket won't fall out inadvertently. While the container being hung on a worker's waist belt, the worker can readily change articles in the tool container. When having sharp articles such as bits, nails, knives and the like in the tool container, a bottom of the tool container won't tear and fall out.