JP4540773B2 - Optical fiber laser device and optical amplification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical fiber laser device that generates laser light by introducing excitation light into a laser active material, and an optical amplification device that amplifies light by introducing excitation light into a laser active material, and in particular, a cooling mechanism for a main body The present invention relates to an optical fiber laser device and an optical amplification device.
[0002]
[Prior art]
In the fields of optical communication and laser processing, there is a demand for the development of a high-power and cheaper laser apparatus. An optical fiber laser device using an optical fiber is known to satisfy such a demand.
[0003]
An optical fiber laser device includes an optical fiber composed of a core having a laser active material and a cladding layer surrounding the core, and a pumping light introducing unit for introducing pumping light into the laser active material. Laser light is generated by introducing excitation light into the core of the fiber. The refractive index of the core is set to be larger than the refractive index of the cladding, and the laser light generated by introducing the pumping light into the laser active material in the core travels through the core while repeating total reflection at the boundary line between the core and the cladding layer. And output from the end face of the optical fiber.
[0004]
When trying to increase the generation efficiency of laser light in an optical fiber laser device, the problem is how efficiently pump light can be introduced into the laser active substance in the core. As a method for increasing the efficiency of introducing excitation light into the laser active material, there is a method of generating laser light by bundling a single optical fiber having a laser active material in a core and introducing the excitation light into the bundle. In an optical fiber laser device using this method, a bundle of optical fibers is formed by diffusing a single continuous optical fiber multiple times around a certain region or by winding it around a disc-like or cylindrical region. An optical fiber structure is formed by covering the bundle of optical fibers with a curable material such as an ultraviolet curable resin having the same refractive index as that of the cladding layer without any gap. The optical fiber structure is covered with a low refractive index layer having a refractive index lower than that of the cladding layer, and a plurality of LD light sources serving as excitation light introducing portions are disposed around the optical fiber structure. Then, excitation light is introduced into the optical fiber structure by these LD light sources, and a laser active substance located inside the optical fiber structure is excited to generate laser light. The pumping light introduced into the optical fiber structure is confined inside the optical fiber structure while repeating total reflection at the interface between the optical fiber structure and the low refractive index layer, thereby forming the optical fiber structure. The excitation light is introduced into the laser active material while traversing the bundle of optical fibers many times. As a result, excitation light is efficiently introduced into the laser active substance, and high laser light generation efficiency can be obtained.
[0005]
When laser light is generated in such an optical fiber laser device, the optical fiber structure generates heat due to the introduction of excitation light. The heat generated by the introduction of the excitation light needs to be dissipated by water cooling using a water cooling unit provided with a water passage for circulating cooling water, or air cooling using an air cooling unit provided with heat radiation fins. Such a cooling unit such as a water cooling unit may be integrated with the optical fiber structure. In this case, for example, the component of the optical fiber structure cannot be repaired or replaced alone, or the cooling unit When trouble occurs, problems such as the inability to replace only the cooling unit or the like arise. For this reason, it is desirable that the cooling unit is configured separately from the optical fiber structure, and the optical fiber laser device is configured by combining them.
[0006]
[Problems to be solved by the invention]
However, since the optical fiber structure is formed by bundling a plurality of optical fibers by bending or wrapping them with resin or the like, irregularities reflecting the shape of the optical fiber appear on the surface. End up. As a result, the adhesion between the optical fiber structure and the cooling unit attached to the optical fiber structure decreases, and this reduces the thermal conductivity from the optical fiber structure to the cooling unit, resulting in a sufficient heat dissipation effect. There is no problem.
[0007]
The present invention has been made in view of these points, and an object of the present invention is to provide an optical fiber laser device capable of efficiently radiating heat generated by the introduction of excitation light.
[0008]
Another object of the present invention is to provide an optical amplifying device capable of efficiently radiating heat generated by introduction of excitation light.
[0009]
[Means for Solving the Problems]
In the present invention, in order to solve the above-described problem, an optical fiber laser device that generates laser light by introducing excitation light into a laser active material includes a core having the laser active material and a cladding layer surrounding the core. An optical fiber structure in which an optical fiber is disposed and transmits a pumping light, and a sealing material having a refractive index equal to that of the cladding layer covers the optical fiber; and the laser active material includes the pumping light. an excitation light introducing part for introducing a and having a smaller refractive index than the refractive index of at least the cladding layer and the fluidity, the transparent fluorine resin is used for transmitting the excitation light, the light of the optical fiber structure fibers are provided in close contact with the unevenness of the arrangement surface spirally, and the low refractive index portion to confine said pumping light inside the optical fiber structure, before Optical fiber laser device, characterized in that it comprises a cooling unit disposed in close contact with the low refractive index portion, is provided.
[0010]
Here, the optical fiber generates laser light by introducing pumping light into the laser active material, the pumping light introducing unit introduces pumping light into the laser active material, and the low refractive index unit transmits the pumping light to the optical fiber structure. The cooling unit is confined inside the body and disposed in close contact with the irregularities on the outside of the optical fiber structure, whereby heat generated in the optical fiber structure is efficiently transmitted and the transmitted heat is radiated.
[0011]
Further, in an optical amplifying apparatus for amplifying light by introducing excitation light into a laser active material, an optical fiber having a core having the laser active material and a clad layer surrounding the core is disposed, and the excitation light is An optical fiber structure that is formed by covering the optical fiber with a sealing material that is transparent and has a refractive index equal to that of the cladding layer; an excitation light introduction unit that introduces the excitation light into the laser active material; A transparent fluororesin having a refractive index and fluidity smaller than the refractive index of the cladding layer and transmitting the excitation light is used, and the surface of the optical fiber structure on which the optical fibers are arranged in a spiral shape is used . provided in close contact with irregularities, the low refractive index portion confined within the pumping light the optical fiber structure, a cooling unit disposed in close contact with the low refractive index portion , Optical amplifier, characterized in that it comprises a are provided.
[0012]
Here, the optical fiber generates laser light by introducing pumping light into the laser active material, the pumping light introducing unit introduces pumping light into the laser active material, and the low refractive index unit transmits the pumping light to the optical fiber structure. The cooling unit is confined inside the body and is provided in close contact with the irregularities on the outside of the optical fiber structure, whereby heat generated in the optical fiber structure is efficiently transmitted and the transmitted heat is radiated.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, a first embodiment of the present invention will be described.
[0014]
FIG. 2 is a plan view of the optical fiber laser device 1 according to this embodiment, and FIG. 1 is a cross-sectional view taken along line AA of the optical fiber laser device 1 in FIG.
The optical fiber laser device 1 is fixed in close contact with an optical fiber structure 3 that generates laser light, a lens duct 2 that is a pumping light introduction unit that introduces pumping light into the optical fiber structure 3, and the optical fiber structure 3. The heat-conducting sheet 4 functions as a heat-conducting section, and the water-cooling unit 5 that is a cooling unit that cools the optical fiber structure 3 that generates heat by the introduction of excitation light.
[0015]
The optical fiber structure 3 is a continuous optical fiber composed of a core 3ca having a laser active material such as a laser active ion typified by Nd ions and the like, a dye, and other emission centers, and a cladding layer 3cb surrounding the core 3ca. 3c, a laser extraction optical fiber 3f for extracting the generated laser, a reflecting mirror 3e attached to one end of the optical fiber, a sealing resin 3d having substantially the same refractive index as that of the cladding layer 3cb and transparent to the excitation light, and the cladding The low refractive index layer 3a functioning as a low refractive index portion such as a transparent fluororesin having a refractive index smaller than that of the layer 3cb. Here, it is desirable that the reflecting mirror 3e has a high reflectance with respect to the wavelength of the generated laser light. The cladding layer 3cb has a refractive index smaller than that of the core 3ca.
[0016]
The optical fiber 3c is arranged centered on one end and is wound in a single layer from the center to the outside in order to form a disk-shaped plane. A reflecting mirror 3e is attached to one end of the optical fiber 3c located at the center of the disk, and a laser extraction optical fiber 3f is attached to the other end located outside the disk shape.
[0017]
Thus, the optical fiber 3c and the reflecting mirror 3e arranged in a disk shape are sealed in a disk shape by the sealing resin 3d. Thus, the low refractive index layer 3a is disposed on the surface of the sealing resin 3d that seals the optical fiber 3c, whereby the disk-shaped optical fiber structure 3 is formed.
[0018]
A plurality of lens ducts 2 are arranged at certain intervals along the disk side surface on the disk side surface of the optical fiber structure 3 formed in a disk shape, and the excitation light is output to each lens duct 2. An LD light source (not shown) is attached. Here, the direction in which each lens duct 2 is arranged is a direction in which excitation light output from the LD light source is introduced from the disk side surface of the optical fiber structure 3 toward the center.
[0019]
A heat conductive sheet 4 is disposed in close contact with the bottom surface of the optical fiber structure 3.
As a material of the heat conductive sheet 4, any material can be used without particular limitation as long as it has high heat conductivity and flexibility capable of sufficiently adhering to irregularities such as the surface of the optical fiber structure 3. Moreover, it is more desirable if it has the non-adhesiveness which does not adhere to the optical fiber structure 3 and the water cooling unit 5 even if it exposes to the high temperature at the time of apparatus operation for a long time. An example of a sheet satisfying such a condition is a sheet in which a material having a higher thermal conductivity than that of a rubber is dispersed in a heat-resistant rubber. Specifically, for example, silicon rubber is used as the heat resistant rubber, and boron nitride is dispersed therein. Furthermore, in order to improve mechanical strength, you may use what added glass fiber to them.
[0020]
The water cooling unit 5 is disposed in close contact with the bottom surface of the heat conductive sheet 4 disposed in close contact with the bottom surface of the optical fiber structure 3.
The water cooling unit 5 has a plurality of water channels therein, and cools the apparatus by circulating cooling water through the water channels.
[0021]
It is desirable that the water cooling unit 5 has a flat plate structure in order to increase the cooling efficiency of the apparatus. As a material, it can be used without particular limitation as long as it has high thermal conductivity and a certain degree of heat resistance, but aluminum is desirable in consideration of thermal conductivity and light weight. Further, other metals having high thermal conductivity, such as copper, may be used depending on the use environment.
[0022]
Next, the operation of the optical fiber laser device 1 will be described with reference to FIGS. 1 and 2.
When laser light is output using the optical fiber laser device 1, first, excitation light is introduced into the lens duct 2 by an LD light source (not shown). The excitation light introduced into the lens duct 2 is introduced from the disk side surface of the optical fiber structure 3 toward the center of the optical fiber structure 3 by the lens duct 2.
[0023]
Since the refractive index of the low refractive index layer 3a is smaller than the refractive index of the sealing resin 3d, the excitation light introduced into the optical fiber structure 3 is totally reflected at the boundary between the low refractive index layer 3a and the sealing resin 3d. Then, it is confined inside the optical fiber structure 3. At this time, the excitation light confined inside the optical fiber structure 3 crosses the core 3ca formed inside the optical fiber structure 3 while repeating total reflection at this boundary portion, and exists inside the core 3ca. Excites the laser active material. As a result, the excitation light introduced into the optical fiber structure 3 is absorbed by the laser active material or remains in the optical fiber structure until the energy is lost due to other loss, and the core 3ca. Thus, the laser active substance inside is continuously excited.
[0024]
The laser active material into which the excitation light is introduced in this way generates laser light, and the generated laser light travels inside the core 3ca while being totally reflected at the boundary surface between the core 3ca and the cladding layer 3cb. The laser light traveling inside the core 3ca reaches both ends of the optical fiber 3c, and the laser light reaching one end where the reflecting mirror 3e located at the center of the optical fiber structure 3 is attached is totally reflected by the reflecting mirror 3e. As a result, the traveling direction is changed, and the interior of the core 3ca travels again. Thus, the generated laser light can be collected at one end to which the laser extraction optical fiber 3f is attached, and the laser light reaching the one end is extracted from the laser extraction optical fiber 3f.
[0025]
As described above, the excitation light introduced into the optical fiber structure 3 is used for excitation of the laser active substance, part of which is a boundary surface between the low refractive index layer 3a and the sealing resin 3d, It is converted into heat due to loss in the boundary surface between the clad layer 3ca and the sealing resin 3d, the laser active material, impurities present inside, and the like. At this time, the LD light source itself that introduces excitation light into the lens duct also generates heat. Thus, the heat generated in the optical fiber structure 3 or the like is efficiently transmitted to the heat conductive sheet 4 that is in close contact with the optical fiber structure 3, and the heat transmitted to the heat conductive sheet 4 is transmitted to the water cooling unit 5. . The heat that has reached the water cooling unit 5 is transmitted to the cooling water flowing inside, and is released to the outside by the flow of the cooling water. Thereby, it becomes possible to efficiently release the heat of the optical fiber structure 3 generated by the introduction of the excitation light.
[0026]
FIG. 3 is an assembly diagram illustrating a specific configuration example of the optical fiber laser device 1 according to the present embodiment.
In the example of FIG. 3, the water cooling unit 5 is provided with a water supply port 5a and a discharge port 5b. Cooling water is introduced into the water cooling unit 5 from the water supply port 5a, and the introduced cooling water flows through the water cooling unit 5. After that, it is discharged from the discharge port 5b. The heat conductive sheet 4 is disposed in close contact with the upper surface of the water cooling unit 5, and the optical fiber structure 3 is disposed in close contact with the upper surface of the heat conductive sheet 4. A main body cover 6 for protecting the inside is disposed on the upper surface.
[0027]
Thus, in this embodiment, the heat conductive sheet 4 is disposed in close contact with the bottom surface of the optical fiber structure 3, and the water cooling unit 5 is disposed in close contact with the bottom surface of the heat conductive sheet 4, Even when the external surface of the optical fiber structure 3 is uneven, it is possible to efficiently transfer the heat generated in the optical fiber structure 3 to the water cooling unit 5 when pump light is introduced, and to efficiently dissipate heat from the apparatus. Can be done.
[0028]
In this embodiment, the optical fiber 3c is wound and arranged in a spiral shape, and the optical fiber structure 3 is formed by sealing with a sealing resin 3d. Alternatively, the optical fiber structure 3 may be configured by arranging the optical fiber in a planar shape by pushing down the optical fiber wound in a cylindrical shape and sealing it in a plate shape with a sealing resin. .
[0029]
In this embodiment, the optical fiber 3c is sealed with the sealing resin 3d to form the optical fiber structure 3. However, the sealing resin 3d is not used, and the optical fibers are welded, or The optical fiber structure 3 may be configured by filling a gap between optical fibers with oil having a refractive index equal to that of the cladding layer 3cb.
[0030]
Furthermore, in this embodiment, the heat conductive sheet 4 is disposed only on the bottom surface of the optical fiber structure 3, and the water cooling unit 5 is disposed on the bottom surface. Alternatively, a heat conductive sheet may be disposed on the side surface, and a water cooling unit may be disposed in close contact with the sheet.
[0031]
Further, in this embodiment, the heat conductive sheet 4 is interposed between the low refractive index layer 3a and the water cooling unit 5, but the water cooling unit 5 is directly attached to the low refractive index layer 3a without using the heat conductive sheet 4. It is good also as a structure arrange | positioned closely. In this case, as the low refractive index layer 3a, it is desirable to use a material that has fluidity, has a refractive index smaller than that of the cladding layer 3cb and the sealing resin 3d of the optical fiber 3c, and transmits excitation light. By adopting such a configuration, the low refractive index layer 3a serves both to confine the excitation light in the optical fiber structure 3 and to increase the thermal conductivity from the optical fiber structure 3 to the water cooling unit 5. Thus, the number of parts can be reduced. In this case, the thickness of the low refractive index layer 3a is desirably 100 μm or less.
[0032]
Furthermore, in this embodiment, the optical fiber laser device 1 that generates laser light has been described. However, the present invention eliminates the reflecting mirror 3e from the configuration of the optical fiber laser device 1, and receives input light from one end of the optical fiber 3c. The present invention may be applied to an optical amplifying apparatus that amplifies input light and outputs the amplified light from the other end.
[0033]
Next, a second embodiment of the present invention will be described.
This embodiment is a modification of the optical fiber laser device 1 in the first embodiment. In the first embodiment, the optical fiber laser device 1 is cooled by water cooling. However, in the second embodiment, the optical fiber laser device is cooled by air cooling. In the following description, differences from the first embodiment will be mainly described, and description of matters common to the first embodiment will be omitted.
[0034]
FIG. 4 is an assembly diagram showing the configuration of the optical fiber laser device 10 in this embodiment.
In the optical fiber laser device 10, the heat conductive sheets 14a and 14b are disposed in close contact with the upper and lower surfaces of the optical fiber structure 3, and the air cooling units 15 and 16 are disposed in close contact with the respective heat conductive sheets 14a and 14b. To do.
[0035]
The air cooling units 15 and 16 desirably have flat inner surfaces in order to improve adhesion to the heat conductive sheets 14a and 14b. On the other hand, a plurality of heat radiation fins 15a and 16a are formed on each outer surface. The radiating fins 15a and 16a are pleated projections formed on the outer surfaces of the air cooling units 15 and 16, and the air cooling units 15 and 16 have a large surface area in contact with the outside air. Work to raise. The shape of the radiating fins 15a and 16a is not particularly limited as long as it has a structure that can take a large surface area with respect to the outside air. As a material, it can be used without particular limitation as long as it has high thermal conductivity and a certain degree of heat resistance, but aluminum is desirable in consideration of thermal conductivity and light weight. Further, other metals having high thermal conductivity, such as copper, may be used depending on the use environment.
[0036]
By adopting such a configuration, the heat generated in the optical fiber structure 3 by introducing the excitation light is efficiently transmitted to the heat conductive sheets 14a and 14b in close contact with the optical fiber structure 3, and further, the heat conductive sheet 14a. , 14b is efficiently transmitted to the air-cooling units 15 and 16 that are in close contact therewith, and radiated to the outside air from the respective radiation fins 15a and 16a.
[0037]
Thus, even if it cools by the air cooling units 15 and 16, it becomes possible to acquire the effect similar to 1st Embodiment.
In this embodiment, the cooling is performed only by the air cooling units 15 and 16, but the cooling water may flow inside the air cooling units 15 and 16, and the cooling may be performed by air cooling and water cooling.
[0038]
In this embodiment, the air cooling units 15 and 16 are disposed above and below the optical fiber structure 3, but the air cooling units may be disposed only on either the upper or lower side.
[0039]
Further, in this embodiment, the heat conductive sheets 14a and 14b are interposed between the low refractive index layer 3a of the optical fiber structure 3 and the air cooling units 15 and 16, but the heat conductive sheets 14a and 14b are not used. The air cooling units 15 and 16 may be arranged in close contact with the low refractive index layer 3a. In this case, as the low refractive index layer 3a, it is desirable to use a material that has fluidity, has a refractive index smaller than that of the cladding layer 3cb and the sealing resin 3d of the optical fiber 3c, and transmits excitation light. With such a configuration, the low refractive index layer 3a functions to confine the excitation light in the optical fiber structure 3 and to increase the thermal conductivity from the optical fiber structure 3 to the air cooling units 15 and 16. This also serves as a reduction in the number of parts. In this case, the thickness of the low refractive index layer 3a is desirably 100 μm or less.
[0040]
In the present embodiment, the optical fiber laser device 10 that generates laser light has been described. However, the present invention may be applied to an optical amplifying device.
[0041]
【The invention's effect】
As described above, in the optical fiber laser device of the present invention, the low refractive index portion is provided on the irregularities outside the optical fiber structure, and the cooling unit is closely attached to the low refractive index portion. Even when the external surface is uneven, it is possible to efficiently transfer the heat generated in the optical fiber structure to the cooling unit when pump light is introduced, and to efficiently dissipate the device without increasing the number of parts. be able to.
[0042]
Further, in the optical amplifying device of the present invention, since the low refractive index portion is provided on the irregularities outside the optical fiber structure, and the cooling unit is adhered to the low refractive index portion, the irregularities are formed on the external surface of the optical fiber structure. Even when there is a laser beam, the heat generated in the optical fiber structure at the time of introducing the pumping light can be efficiently transmitted to the cooling unit, and the device can be efficiently radiated without increasing the number of components.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an optical fiber laser device.
FIG. 2 is a plan view of an optical fiber laser device.
FIG. 3 is an assembly diagram showing a configuration of an optical fiber laser device.
FIG. 4 is an assembly diagram illustrating a configuration of an optical fiber laser device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 10 Optical fiber laser apparatus 2 Lens duct 3 Optical fiber structure 3a Low refractive index layer 3c Optical fiber 3ca Core 3cb Clad layer 3d Sealing resin 4, 14a, 14b Thermal conductive sheet 5 Water cooling unit 15, 16 Air cooling unit 15a, 16a Heat radiation fin

Claims (2)

In an optical fiber laser device for generating laser light by introducing excitation light into a laser active substance,
An optical fiber having a core having the laser active material and a cladding layer surrounding the core is disposed, and a sealing material that transmits the excitation light and has a refractive index equal to that of the cladding layer covers the optical fiber. An optical fiber structure constituted by:
An excitation light introducing portion for introducing the excitation light into the laser active material;
A surface having a refractive index smaller than the refractive index of the cladding layer and fluidity, and using a transparent fluororesin that transmits the excitation light, and the optical fiber of the optical fiber structure is disposed in a spiral shape A low-refractive-index part that is provided in close contact with the irregularities of the optical fiber structure to confine the excitation light inside the optical fiber structure;
A cooling unit disposed in close contact with the low refractive index portion;
An optical fiber laser device comprising: In an optical amplifier that amplifies light by introducing excitation light into a laser active substance,
An optical fiber having a core having the laser active material and a cladding layer surrounding the core is disposed, and a sealing material that transmits the excitation light and has a refractive index equal to that of the cladding layer covers the optical fiber. An optical fiber structure constituted by:
An excitation light introducing portion for introducing the excitation light into the laser active material;
A surface having a refractive index smaller than the refractive index of the cladding layer and fluidity, and using a transparent fluororesin that transmits the excitation light, and the optical fiber of the optical fiber structure is disposed in a spiral shape A low-refractive-index part that is provided in close contact with the irregularities of the optical fiber structure to confine the excitation light inside the optical fiber structure;
A cooling unit disposed in close contact with the low refractive index portion;
An optical amplifying device comprising:

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