JP2004356421A - Optical fiber laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber laser capable of outputting a high-power laser beam by suppressing heat generation of the optical fiber used as a laser medium. <P>SOLUTION: The optical fiber laser at least comprises an optical fiber 10 having a core to which a laser activating material has been added, and a cylindrical drum 20 wound up with the optical fiber 10. The optical fiber 10 is wound around the outer peripheral surface 20a of the drum 20 so as not to be overlapped, with a thermally conductive material being interposed between the optical fiber 10 and an inner surface of a groove 21 provided in the drum 20. The groove 21 which can accommodate only one optical fiber 10 is spirally provided from one end surface 20b side to the other end surface 20c side. The optical fiber 10 is wound around the outer peripheral surface 20a being accommodated in the groove 21. A cover 30 is provided so as to cover the optical fiber 10 wound around the outer peripheral surface 20a. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical fiber laser using an optical fiber containing a laser active substance in a resonator as a laser medium.
[0002]
[Prior art]
An optical fiber having a core to which a laser active substance is added absorbs the excitation light when the excitation light is incident, and outputs the laser light by stimulated emission. However, the energy of the excitation light absorbed by the optical fiber is not entirely converted into laser light, but is partially converted into heat.
[0003]
The amount of heat generated at this time is an amount that does not matter if the output fiber is a low-output optical fiber. However, when pumping with a large output of several tens of watts or more, the amount of heat becomes extremely large when an optical fiber having a high absorption rate is used.
[0004]
Further, the rate at which the excitation light incident on the optical fiber is converted into heat tends to increase as the temperature of the optical fiber itself increases. Therefore, if excitation is performed with a large output without taking measures against heat, it will cause an increase in heat generation and a decrease in laser output efficiency.
[0005]
In addition, due to the high temperature of the optical fiber itself, there is a danger that the optical fiber is dislocated due to glass dislocation, a function is reduced during operation, melting, and a device is ignited.
[0006]
Patent Document 1 proposes a heat radiation mechanism in a system in which an optical fiber of a laser medium is wound around a drum together with a light guide member to distribute and introduce excitation light. However, since this method requires a light guide member wound around the optical fiber, this method is not suitable when light is incident from the end face of the optical fiber without disposing the light guide member around.
[0007]
[Patent Document 1]
JP 2001-156363 A
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and has as its object to provide an optical fiber laser capable of suppressing heat generation of an optical fiber used as a laser medium and outputting high-power laser light. .
[0009]
[Means for Solving the Problems]
The present invention provides an optical fiber laser comprising at least an optical fiber having a core doped with a laser active substance, and a cylindrical drum around which the optical fiber is wound. An optical fiber laser is provided in which the fibers are wound around the outer periphery of the drum so that they do not overlap each other, and a thermally conductive material is interposed between the optical fiber and the outer periphery of the drum.
[0010]
In the optical fiber laser having the above-described configuration, a groove capable of accommodating only one optical fiber is provided on the outer periphery of the drum in a spiral shape from one end surface side of the drum to the other end surface side, and the optical fiber Is preferably housed in the groove and wound around the outer periphery of the drum.
[0011]
In the optical fiber laser having the above configuration, it is preferable that a cover is provided to cover the optical fiber wound around the outer periphery of the drum.
[0012]
In the optical fiber laser having the above configuration, the depth and width of the cross section of the groove provided on the outer periphery of the drum are equal to or larger than the outer diameter of the optical fiber accommodated in the groove, and the cross sectional shape of the groove is It is preferable that the surface of the optical fiber wound on the side that is in contact with the inner peripheral side forms an arc, and the diameter of the arc is equal to or larger than the outer diameter of the optical fiber.
[0013]
In the optical fiber laser having the above configuration, the laser active substance is selected from Nd ³⁺ , Yb ³⁺ , Er ³⁺ , Pr ³⁺ , Ce ³⁺ , Tm ³⁺ , Ho ³⁺ , Tb ³⁺ , Dy ³⁺ , Eu ³⁺ , and Eu ^2+. Preferably, at least one kind is used.
[0014]
In the optical fiber laser having the above-described structure, it is preferable that a material forming a core of the optical fiber is mainly composed of fluoride glass.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
FIG. 1 is a schematic front view showing an example of the optical fiber laser of the present invention. FIG. 2 is a schematic plan view of the optical fiber laser of FIG. 1 as viewed from the end face of the drum.
1 and 2, reference numeral 10 denotes an optical fiber having a core to which a laser active substance is added, reference numeral 20 denotes a cylindrical drum, and reference numeral 30 denotes a cylindrical cover for covering the optical fiber.
The optical fiber laser of this example is schematically composed of an optical fiber 10, a drum 20, and a cover 30. In the optical fiber laser of this example, the optical fiber 10 is housed in a groove 21 spirally provided on the outer periphery of the drum 20 and wound around the outer periphery of the drum 20 so as not to overlap with each other. A cover 30 is provided so as to cover the optical fiber 10 thus formed.
[0016]
The optical fiber 10 is an optical fiber having a core made of fluoride glass to which a laser active substance is added, and a clad made of fluoride glass provided around the core.
As the optical fiber 10, a bare optical fiber, an optical fiber, or an optical fiber core can be used.
[0017]
As the laser-active substance, ions of rare earth elements are used. For example, Nd ³⁺ , Yb ³⁺ , Er ³⁺ , Pr ³⁺ , Ce ³⁺ , Tm ³⁺ , Ho ³⁺ , Tb ³⁺ , Dy ³⁺ , Eu ³⁺ , Eu ^At least one selected from ²⁺ is used.
The ions of these rare earth elements are added to the core of the optical fiber 10 at about 1,000 ppm to 100,000 ppm (weight ratio).
[0018]
When ions of these rare earth elements are added, excitation light having a specific wavelength is introduced into the core of the optical fiber 10, and stimulated emission allows laser oscillation of light of another wavelength.
[0019]
The drum 20 is a columnar member made of a material having a high heat transfer coefficient such as aluminum alloy, copper, or brass. A groove 21 for receiving the optical fiber 10 is formed on the outer peripheral surface 20a from one end surface 20b to the other. Are provided spirally toward the end face 20c side of the. Further, the drum 20 is provided with four through holes 22 from one end face 20a to the other end face 20b.
[0020]
The outer diameter and height of the drum 20 are appropriately set in accordance with the length of the optical fiber 10 wound around the outer periphery. Usually, the outer diameter is about 150 mm to 200 mm, and the height is about 60 mm to 100 mm. Has become.
[0021]
The groove 21 is provided in such a size that only one optical fiber 10 can be accommodated, and the interval at which the groove 21 is provided is generated in one optical fiber 10 between the optical fibers 10 accommodated in the adjacent grooves 21. Desirably, the heat does not reach the other optical fiber 10.
As described above, the grooves 21 are provided at predetermined intervals, and the optical fibers 10 are accommodated therein, so that the optical fibers 10 are wound around the outer peripheral surface 20 a of the drum 20 so as not to overlap with each other.
[0022]
Further, as shown in FIG. 3, the cross-sectional shape of the groove 21 is substantially U-shaped, and when the optical fiber 10 is wound, a surface (hereinafter, referred to as a side surface) located on the inner periphery of the optical fiber 10 contacts. , "Bottom".) 21a forms an arc.
Here, assuming that the outer diameter of the optical fiber 10 is d, the depth D ₁ and the width W of the cross section of the groove 21 are preferably not less than the outer diameter d, and d ≦ D ₁ ≦ d + 0.1 mm, d ≦ W It is more preferable that ≦ d + 0.1 mm. Moreover, when the diameter of the bottom surface 21a and _{D 2,} the diameter _{D 2} is preferably the outer diameter d or more, and more preferably d ≦ _{D 2} ≦ d + 0.1 mm.
[0023]
When the depth D ₁ and the width W of the cross section of the groove 21 are smaller than the outer diameter d, the outer peripheral surface 10 a of the optical fiber 10 and the outer peripheral surface 20 a of the drum 20 are on the same plane, or the outer peripheral surface 10 a of the optical fiber 10. Of the optical fiber 10 is not inside the groove 21 than the outer peripheral surface 20a, and the optical fiber 10 is easily damaged by an external impact or the like. On the other hand, the depth _{D 1} and the width W is more than the outer diameter d + 0.1 mm, the optical fiber 10 is liable to fall off from the groove 21. In addition, thermal contact between the optical fiber 10 and the drum 20 deteriorates, and the efficiency of heat radiation from the optical fiber 10 to the drum 20 decreases.
[0024]
Further, the diameter _{D 2} of the bottom surface 21a of the cross-section of the groove 21 is less than the outer diameter d, the outer peripheral surface 20a and the same plane on the outer peripheral surface 10a and the drum 20 of the optical fiber 10, or the outer peripheral surface of the optical fiber 10 A part of 10a is not inside the groove 21 than the outer peripheral surface 20a, and the optical fiber 10 is easily damaged by an external impact or the like. On the other hand, the depth _{D 1} and the width W is more than the outer diameter d + 0.1 mm, the optical fiber 10 is liable to fall off from the groove 21. In addition, thermal contact between the optical fiber 10 and the drum 20 deteriorates, and the efficiency of heat radiation from the optical fiber 10 to the drum 20 decreases.
[0025]
Further, a heat conductive material is interposed between the optical fiber 10 and the inner surface 21b of the groove 21. Here, the inner surface 21b includes the bottom surface 21a.
Examples of the heat conductive material include silicon grease, a heat radiation compound, and a heat conductive sheet. Among them, the heat conductive material has a heat conductivity of about 1 to 5 W / mK, and air is provided between the optical fiber 10 and the groove 21. It is desirable to use a material that can improve thermal conductivity by not interposing a gap.
[0026]
The size (inner diameter) of the through hole 22 is not particularly limited. However, in order to efficiently release the heat from the optical fiber 10 to the outside, it is desirable that the position where the through hole 22 is provided is not biased.
[0027]
Note that, in the optical fiber laser of this example, four through holes 22 are provided, but the optical fiber laser of the present invention is not limited to this. In the optical fiber laser of the present invention, a large number of through holes having a small inner diameter may be provided to increase the surface area of the inner surface.
[0028]
The inner diameter of the cover 30 is larger than the outer diameter of the drum 20 by about +0.1 mm to +0.4 mm, and the cover 30 covers the optical fiber 10 wound around the drum 20. It is a cylindrical member appropriately set so as to cover the area of the outer peripheral surface 20a of the drum 20 on which the fiber 10 is arranged.
The cover 30 is formed of a metal such as an aluminum alloy, copper, and brass.
[0029]
In the optical fiber laser of this example, a thin cylindrical member is used as the cover 30, but the optical fiber laser of the present invention is not limited to this. In the optical fiber laser of the present invention, as the cover, a structure provided with a hole having an inner diameter slightly larger than the outer diameter of the drum is used, and the drum around which the optical fiber is wound is housed in this hole. Good.
[0030]
Further, in the optical fiber laser of the present invention, a blower is disposed in the longitudinal direction of the through hole provided in the drum, and the air is blown into the through hole to forcibly cool the drum, thereby improving the heat radiation efficiency of the optical fiber. You may make it raise.
[0031]
In the optical fiber laser of this example, the optical fiber 10 is wound around the outer peripheral surface 20a of the drum 20 so as not to overlap with each other, and a heat conductive material is interposed between the optical fiber 10 and the inner surface 21b of the groove 21. Let me. As a result, the optical fiber 10 is in direct contact with the drum 20 made of a material having a high thermal conductivity over its entire length, or is in contact with the drum 20 to an extent corresponding thereto. The heat radiation area can be made larger than in the case of a single unit. Therefore, the optical fiber laser of this example can efficiently radiate heat from the optical fiber 10, and can output high-power laser light.
[0032]
Further, by interposing a heat conductive material, it is possible to prevent air from intervening between the optical fiber 10 and the inner surface 21b of the groove 21, so that the efficiency of heat radiation from the optical fiber 10 to the drum 20 is improved. Is improved.
[0033]
Furthermore, the provision of the cover 30 not only prevents the optical fiber 10 from being damaged and prevents the optical fiber 10 from coming off the groove 21 after the optical fiber 10 is accommodated in the groove 21, The contact area between the drum 10 and the drum 20 can be improved, and the risk of directly looking at the laser beam leaking from the side surface of the optical fiber 10 can be reduced.
[0034]
Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples.
(Experimental example)
An optical fiber laser as shown in FIGS. 1 to 3 was produced.
A spiral groove 21 provided on the outer peripheral surface of a cylindrical member made of an aluminum alloy having an outer diameter of 150 mm and a height of 60 mm as the drum 20 from one end surface 20b side to the other end surface 20c side; One having four through holes 22 provided from the end face 20b toward the other end face 20c was prepared.
0.5mm depth _{D 1} of the cross-section of the groove 21, 0.5mm width W, 0.25 mm radius r of the bottom surface 21a, 3 mm apart grooves 21, the number of turns of the groove 21 was 20 times.
The inner diameter of the through hole 22 was set to 50 mm.
[0035]
The optical fiber 10 having heat conductive silicon grease applied to the surface thereof was accommodated in the groove 21, and the optical fiber 10 was wound around the outer peripheral surface 20 a of the drum 20.
As the optical fiber 10, a multimode fluoride fiber made of fluoride glass containing 40,000 ppm of erbium ions (Er ³⁺ ) and having a core of 100 μm in outer diameter and 0.5 mm in outer diameter was used.
Further, an aluminum plate having a thickness of 0.5 mm was wound around the outer peripheral surface 20a of the drum 20 around which the optical fiber 10 was wound so as to cover the optical fiber 10, thereby forming a cover 30, thereby obtaining an optical fiber laser.
[0036]
When excitation light having a wavelength of 0.98 μm and an output of 10 W was incident on one end face of the optical fiber 10 of the optical fiber laser of this embodiment, the temperature of the optical fiber 10 was 50 ° C.
On the other hand, when excitation light having a wavelength of 0.98 μm and an output of 10 W was incident on the end face of the optical fiber of the conventional optical fiber laser, the temperature of the optical fiber rose to 200 ° C.
Further, when the output of the laser light output from the optical fiber laser of the example and the output of the laser light output from the conventional optical fiber laser were compared, the output of the example was improved by 5% from the comparative example. Was confirmed.
[0037]
【The invention's effect】
As described above, according to the optical fiber laser of the present invention, the optical fiber is wound around the outer peripheral surface of the drum so as not to overlap with each other, and the heat conduction between the optical fiber and the inner surface of the groove of the drum is performed. By interposing the above material, the optical fiber almost directly contacts the drum over its entire length, so that even if the optical fiber generates heat, the heat radiation area can be made larger than when the optical fiber exists alone. . Therefore, since heat can be efficiently radiated from the optical fiber, high-power laser light can be output.
[0038]
In addition, by interposing a heat conductive material, air can be prevented from intervening between the optical fiber and the inner surface of the groove, so that the efficiency of heat radiation from the optical fiber to the drum is improved.
Further, the provision of the cover not only can damage the optical fiber and facilitate the work of accommodating the optical fiber in the groove of the drum, but also improves the contact area between the optical fiber and the drum. In addition, it is possible to reduce the risk of directly viewing the laser light leaking from the side surface of the optical fiber.
[Brief description of the drawings]
FIG. 1 is a schematic front view showing an example of an optical fiber laser of the present invention.
FIG. 2 is a schematic plan view of the optical fiber laser of FIG. 1 as viewed from an end surface of a drum.
FIG. 3 is a schematic sectional view showing a groove of a drum.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Optical fiber, 20 ... Drum, 20a ... Outer peripheral surface, 20b, 20c ... End surface, 21 ... Groove, 21a ... Bottom surface, 21b ... Inner surface, 22 ... Through hole, 30 ... cover.

Claims (6)

In an optical fiber laser having at least an optical fiber having a core to which a laser active substance is added, and a cylindrical drum around which the optical fiber is wound,
The optical fiber is wound around the outer periphery of the drum so as not to overlap each other, and a heat conductive material is interposed between the optical fiber and the outer periphery of the drum. Optical fiber laser. On the outer peripheral surface of the drum, a groove capable of accommodating only one optical fiber is provided spirally from one end surface side of the drum toward the other end surface, and the optical fiber is accommodated in the groove. 2. The optical fiber laser according to claim 1, wherein the optical fiber laser is wound around the outer periphery of the drum. 3. The optical fiber laser according to claim 1, further comprising a cover that covers the optical fiber wound around the outer periphery of the drum. The depth and width of the cross section of the groove provided on the outer periphery of the drum are not less than the outer diameter of the optical fiber accommodated in the groove, and the cross section of the groove is when the optical fiber is wound. The optical fiber laser according to any one of claims 1 to 3, wherein a surface of which the side surface located at the inner periphery contacts an arc forms an arc, and the diameter of the arc is equal to or larger than the outer diameter of the optical fiber. The laser active material is at least one selected from Nd ³⁺ , Yb ³⁺ , Er ³⁺ , Pr ³⁺ , Ce ³⁺ , Tm ³⁺ , Ho ³⁺ , Tb ³⁺ , Dy ³⁺ , Eu ³⁺ and Eu ^2+. The optical fiber laser according to any one of claims 1 to 4, wherein 6. The optical fiber laser according to claim 5, wherein a material forming a core of said optical fiber is mainly composed of fluoride glass.

Images