阅读说明：本技术 一种低温升光纤泵浦合束器 (Low-temperature-rise optical fiber pumping beam combiner ) 是由 刘玙 李雨薇 黄珊 黎玥 吴文杰 王建军 林宏奂 欧光亮 李好 黎沁 于 2021-09-27 设计创作，主要内容包括：本发明公开了一种低温升光纤泵浦合束器,所述合束器包括：输入光纤束、吸光器以及多包层输出光纤,所述输入光纤束拉锥后与多包层输出光纤熔接,所述吸光器在输入光纤束的外面,与输入光纤束在特定直径的平直段上具有光学接触,所述输入光纤束的拉锥结构和吸光器的放置位置根据吸光器的折射率与输入光纤束中的光纤的包层折射率不同而不同。本发明提供的低温升光纤泵浦合束器,通过设计吸光器折射率和合束器结构,实现泵浦废光和可传导光分开传输,并将泵浦废光在进入多包层输出光纤之前进行提前滤除,降低了由于泵浦废光进入多包层输出光纤所造成的涂覆层发热,为提高激光器的功率输出提供了可能。(The invention discloses a low temperature rise optical fiber pumping beam combiner, which comprises: the optical fiber bundle comprises an input optical fiber bundle, a light absorber and a multi-cladding output optical fiber, wherein the input optical fiber bundle is fused with the multi-cladding output optical fiber after being tapered, the light absorber is arranged outside the input optical fiber bundle and is in optical contact with the input optical fiber bundle on a straight section with a specific diameter, and the tapered structure of the input optical fiber bundle and the placement position of the light absorber are different according to the difference between the refractive index of the light absorber and the cladding refractive index of the optical fiber in the input optical fiber bundle. According to the low-temperature-rise optical fiber pumping beam combiner, the refractive index of the light absorber and the structure of the beam combiner are designed, pumping waste light and conductable light are transmitted in a split mode, the pumping waste light is filtered out in advance before entering the multi-clad output optical fiber, heating of a coating layer caused by the fact that the pumping waste light enters the multi-clad output optical fiber is reduced, and the possibility of improving the power output of a laser is provided.)

1. A low temperature rise fiber pump combiner, comprising: an input optical fiber bundle (1), a light absorber (2) and a multi-clad output optical fiber (3);

the cladding refractive index of the optical fibers in the input optical fiber bundle (1)Is smaller than the refractive index of the light absorber (2)And the input optical fiber bundle (1) is tapered and thenThe multi-clad output optical fiber (3) is welded;

tapering the input optical fiber bundle (1) to sequentially form a tapered area I (21), a straight section I (22), a tapered area II (23) and a straight section II (24); the outer diameter of the straight section I (22) is set to beWhereinAndthe outer diameter and the numerical aperture of the cladding layer of the multi-clad output fiber (3) for conducting the pump light,setting the outer diameter of a straight section II (24) to be equal to the outer diameter of a layer of cladding conducted by pump light in the multi-cladding output optical fiber (3) for the numerical aperture of a fiber core of the optical fiber in the input optical fiber bundle (1);

the surface of the light absorber (2) is provided with a light anti-reflection structure or a light scattering structure, the light absorber (2) is sleeved outside the input optical fiber bundle (1) and is in optical contact with the input optical fiber bundle (1) on the straight section I (22).

2. The low temperature rise fiber pump beam combiner according to claim 1, wherein the light anti-reflection structure of the light absorber (2) is an optical anti-reflection film.

3. The low temperature rise fiber pump beam combiner according to claim 1, wherein the light scattering structure of the light absorber (2) is a surface texturing structure obtained by physical or chemical means.

4. A low temperature rise fiber pump combiner, comprising: an input optical fiber bundle (1), a light absorber (2) and a multi-clad output optical fiber (3);

the cladding refractive index of the optical fibers in the input optical fiber bundle (1)Is greater than the refractive index of the light absorber (2)And the input optical fiber bundle (1) is fused with the multi-cladding output optical fiber (3) after tapering;

the input optical fiber bundle (1) is tapered to sequentially form a tapered area (25) and a flat section (26), and the outer diameter of the flat section (26) and the outer diameter of the layer of cladding which is conducted by the pump light in the multi-cladding output optical fiber (3)The same;

the refractive index of the light absorber (2) isWhereinIs the cladding numerical aperture of the layer of the multi-cladding output fiber (3) in which the pump light is conducted; the surface of the light absorber (2) is provided with a light anti-reflection structure or a light scattering structure, the light absorber (2) is sleeved outside the input optical fiber bundle (1) and is in optical contact with the straight section (26) of the input optical fiber bundle (1).

5. The low temperature rise fiber pump beam combiner according to claim 4, wherein the light anti-reflection structure of the light absorber (2) is an optical anti-reflection film.

6. The low temperature rise fiber pump beam combiner according to claim 4, wherein the light scattering structure of the light absorber (2) is a surface texturing structure obtained by physical or chemical means.

Technical Field

The invention belongs to the field of lasers, and particularly relates to a low-temperature-rise optical fiber pumping beam combiner.

Background

In recent years, fiber lasers have been widely used in the industrial and defense fields due to the advantages of good beam quality, high integration degree, and the like. With the development of technology, these application fields continuously put higher demands on the output power of the fiber laser. In order to realize the increase of the output power of the fiber laser, what needs to be solved is how to inject more pump power into the laser, and therefore, the improvement of the power combining capability of the fiber pump beam combiner, which is a key element of the laser, is crucial to realizing the breakthrough of the output power of the fiber laser.

The existing pumping beam combiner generally adopts multi-clad optical fibers as output optical fibers, the multi-clad optical fibers adopt polymer materials with lower refractive indexes than cladding materials as surface coating layers, and the tolerance temperature of the surface coating layers is generally over one hundred degrees centigrade. In the beam combining process, due to theoretical intrinsic loss of the pump beam combiner and defects in the aspects of materials and processes, a light leakage phenomenon is inevitably generated, light leakage (pump waste light) is partially converted into heat energy to be deposited on a coating layer of the multi-cladding output optical fiber of the pump beam combiner, so that the coating layer is heated, the heating condition tends to be serious along with the increase of power, and the improvement of the pump power and even the output power of the optical fiber laser is seriously limited.

If do not solve the problem of generating heat of the many claddings output fiber of pumping beam combiner earlier, and only realize the increase of fiber laser output power through improving input pump optical power, this is unrealistic, because along with the improvement of input pump optical power, the generating heat of the many claddings output fiber of pumping beam combiner also tends to seriously, when the temperature that generates heat exceeds the temperature of the coating of the many claddings output fiber, inevitably causes the damage to many claddings output fiber, can lead to whole system to damage when serious.

Therefore, in order to increase the power of the fiber laser, it is necessary to improve the heating condition of the multi-clad fiber in the pump beam combiner, and the prior art mainly reduces the temperature rise of the beam combiner by increasing the brightness of the pump light source (pump source), for example, the fiber laser in the pump band is used to replace the Laser Diode (LD) as the pump source, however, this method has the disadvantages of high cost, large volume, low electro-optical conversion efficiency, and being unable to meet the requirements of most laser applications, so the use is limited.

Therefore, it is necessary to solve the above-mentioned heat generation problem of the multi-clad output fiber of the pump combiner from the improvement of the structure of the pump combiner itself.

Disclosure of Invention

In view of the above, the present invention provides a low temperature rise optical fiber pump beam combiner, which separates pump waste light from a light path capable of conducting light by designing a suitable structure and setting refractive indexes of components, and filters the pump waste light in advance before entering a multi-clad output optical fiber to solve the problem of heat generation of the multi-clad output optical fiber of the pump beam combiner.

In order to achieve the purpose, the invention adopts the following technical scheme: a low temperature rise fiber pump combiner, the combiner comprising: an input fiber bundle, a light absorber and a multi-clad output fiber; cladding refractive index of optical fibers in the input optical fiber bundleLess than the refractive index of the absorber(ii) a The input optical fiber bundle is tapered and then is coated with multiple layersThe output optical fibers are welded, and the input optical fiber bundle is tapered to sequentially form a tapered area I, a straight section I, a tapered area II and a straight section II; the outer diameter of the straight section I is set toWhereinAndthe outer diameter and the numerical aperture of the cladding layer that conducts the pump light in the multi-clad output fiber,setting the outer diameter of the straight section II (24) to be equal to the outer diameter of the layer of cladding conducted by the pump light in the multi-cladding output optical fiber (3) for the numerical aperture of the fiber core of the optical fiber in the input optical fiber bundle;

the surface of the light absorber is provided with a light anti-reflection structure or a light scattering structure, the light absorber is sleeved outside the input optical fiber bundle and is in optical contact with the input optical fiber bundle on the straight section I.

Preferably, the light reflection reducing structure of the light absorber is an optical reflection reducing film.

Preferably, the light scattering structure provided on the outer surface of the light absorber is a surface texturing structure obtained by physical or chemical means.

A low temperature rise fiber pump combiner, the combiner comprising: an input fiber bundle, a light absorber and a multi-clad output fiber; cladding refractive index of optical fibers in the input fiber bundleGreater than the refractive index of the absorberAnd the input optical fiber bundle is fused with the multi-cladding output optical fiber after being tapered, and the input optical fiber bundle is tapered into a tapered area and a flat section and is flat and straightThe outer diameter of the segment is the outer diameter of the cladding layer that is in optical conduction with the pump light in the multi-clad output fiberThe same;

the refractive index of the light absorber isWhereinThe optical fiber is a cladding numerical aperture of a layer conducted by pump light in a multi-cladding output optical fiber, a light anti-reflection structure or a light scattering structure is arranged on the surface of a light absorber, and the light absorber is sleeved outside an input optical fiber bundle and is in optical contact with a straight section of the input optical fiber bundle.

Preferably, the light reflection reducing structure of the light absorber is an optical reflection reducing film.

Preferably, the light scattering structure provided on the outer surface of the light absorber is a surface texturing structure obtained by physical or chemical means.

The invention has the beneficial effects that: according to the low-temperature-rise optical fiber pumping beam combiner, the light absorption device refractive index and the beam combiner structure are designed, pumping waste light and light-conducting light paths are separately transmitted, the pumping waste light is filtered in advance before entering the multi-clad output optical fiber, the heat load of a coating layer of the multi-clad output optical fiber is greatly relieved, the limitation of the pumping beam combiner on the improvement of the power of an optical fiber laser is reduced, and the output power of the optical fiber laser can be greatly improved by applying the low-temperature-rise optical fiber pumping beam combiner disclosed by the invention.

Drawings

Fig. 1 is a schematic structural diagram of a low temperature rise optical fiber pump beam combiner in embodiment 1 of the present invention;

fig. 2 is a schematic structural diagram of a low temperature rise optical fiber pump beam combiner in embodiment 2 of the present invention;

in the figure: 1. an input optical fiber bundle 2, a light absorber 3, a multi-clad output optical fiber 21, a cone region I22, a straight section I23, a cone region II24, a straight section II 25, a cone region 26 and a straight section.

Detailed Description

It will be appreciated by those of ordinary skill in the art that the embodiments described herein are intended to assist the reader in understanding the principles of the invention and are to be construed as being without limitation to such specifically recited embodiments and examples. Those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.

The invention is described in detail below with reference to the figures and specific embodiments.

A low temperature rise fiber pump combiner as shown in fig. 1 or fig. 2, the combiner comprising: the optical fiber bundle comprises an input optical fiber bundle 1, a light absorber 2 and a multi-cladding output optical fiber 3, wherein the input optical fiber bundle 1 is tapered and then is welded with the multi-cladding output optical fiber 3, and the light absorber 2 is arranged outside the input optical fiber bundle 1 and has good optical contact with the input optical fiber bundle 1 on a straight section with a specific diameter.

As an example, the cladding refractive index of the optical fiber in the input optical fiber bundle 1Less than the refractive index of the absorber 2The input optical fiber bundle 1 is fused with the multi-cladding output optical fiber 3 after being tapered, the tapered input optical fiber bundle 1 sequentially forms a tapered area I21, a straight section I22, a tapered area II23 and a straight section II24 as shown in figure 1, wherein the outer diameter of the straight section I22 isWhereinAndare respectively a plurality of bagsThe outer diameter and numerical aperture of the cladding of the layer output fiber 3 in which the pump light is conducted,is the numerical aperture of the fiber core of the optical fiber in the input optical fiber bundle 1; setting the outer diameter of the straight section II (24) equal to the outer diameter of the layer of cladding conducted by the pump light in the multi-cladding output fiber (3); the surface of the light absorber 2 is provided with a light anti-reflection structure or a light scattering structure, the light anti-reflection structure can adopt an optical anti-reflection film, the light scattering structure is a surface texturing structure obtained by using a physical or chemical means, and the light absorber 2 is sleeved outside the input optical fiber bundle 1 and has good optical contact with the input optical fiber bundle 1 on a straight section I22.

The cone pulling ratio of the beam combiner structureWhereinIn order to achieve the original outer diameter of the input optical fiber bundle 1, if the lossless transmission from the core of the input optical fiber bundle 1 to the cladding of the multi-clad output optical fiber 3 is to be realized by the beam combiner structure, the initial numerical aperture of the pump light should satisfy the following condition。

For the pumping light which can not satisfy the lossless transmission condition, the numerical apertureIf the conventional beam combiner structure is adopted, the part of light can be coupled into the coating layer of the multi-clad output fiber 3 from the fiber core of the input fiber bundle 1, which causes power loss and heating of the coating layer of the multi-clad output fiber 3, that is, pumping waste light. By adopting the structural design of the beam combiner, after the part of light passes through the cone area I21 of the beam combiner, the propagation angle is increased, and the numerical aperture is increasedBecome into，The numerical aperture of the pump light is larger than the numerical aperture of the core of the input optical fiber bundle 1, which will cause that part of the light cannot continue to be conducted in the core of the input optical fiber bundle 1, and since the refractive index of the light absorber 2 is higher than the refractive index of the fiber cladding of the input optical fiber bundle 1, the part of the light will leak from the core of the input optical fiber bundle 1 to the light absorber 2 through the cladding, and the light anti-reflection or light scattering structure on the light absorber 2 will guide the leaked light to the free space. Therefore, the pump waste light which cannot meet the lossless transmission condition is filtered out of the beam combiner before the cone region II23, and cannot be continuously conducted to the multi-clad output optical fiber 3 to heat the coating layer of the multi-clad output optical fiber.

For the pumping light rays meeting the lossless transmission condition, the numerical aperture of the pumping light raysThe numerical aperture becomes after passing through the taper region I21This portion of the light will remain in the core of the input fiber bundle 1 and will not contact the absorber 2 on the straight section I22, and the numerical aperture of this portion of the light will increase to the point where it passes through the tapered region II23But still satisfies the cladding light conduction condition of the multi-cladding output fiber 3, and can be coupled into the cladding of the output fiber 3 for conduction, that is, the light can be conducted. Thus, the refractive index of the absorber 2 is setIs larger than the cladding refractive index of the optical fibers in the input optical fiber bundle 1The beam combiner structure shown in fig. 1 can separate pumping waste light from light paths capable of conducting and guiding light, and the pumping waste light is filtered in advance, so that the heat load of the coating layer of the multi-cladding output optical fiber is greatly relieved.

As an example, as shown in FIG. 2, the refractive index of the absorber 2 in this exampleLess than the cladding index of the fibers in the input bundle 1And the refractive index of the absorber 2 isWhereinIs the cladding numerical aperture of the layer in which the multi-clad output fiber pump light is conducted. As shown in FIG. 2, the input optical fiber bundle 1 is tapered and then fused with the multi-clad output optical fiber 3, and the input optical fiber bundle 1 is tapered into a tapered region 25 and a flat section 26, and the outer diameter of the flat section 26 is set to be the outer diameter of the cladding layer conducting the pump light in the multi-clad output optical fiber 3Similarly, the light absorber 2 is sleeved outside the input optical fiber bundle 1 and has good optical contact with the input optical fiber bundle 1 on the straight section 26, and the surface of the light absorber 2 is provided with an optical anti-reflection film and an external surface roughening light anti-reflection or light scattering structure realized by using a physical or chemical means.

The cone pulling ratio of the beam combiner structureWhereinIs the original outer diameter of the input fiber bundle 1; for the pumping light which can not satisfy the lossless transmission condition, the numerical apertureAfter passing through the cone 25, the numerical aperture becomesDue to the clad numerical aperture of the multi-clad output fiber of the combinerNot less than the core numerical aperture of the optical fibers in the input optical fiber bundleI.e. byTherefore, the part of the light cannot be conducted in the core of the input optical fiber bundle 1, but leaks to the cladding of the input optical fiber bundle 1, and the leaked light is guided to the free space by the light anti-reflection or light scattering structure on the light absorber 2 because the total reflection condition of the cladding-light absorber interface is not satisfied and leaks to the light absorber 2. Therefore, the pump waste light which cannot meet the lossless transmission condition is filtered out of the beam combiner before the melting point, and is not continuously transmitted to the multi-clad output optical fiber 3 to heat the coating layer of the multi-clad output optical fiber.

For the pumping light rays meeting the lossless transmission condition, the numerical aperture of the pumping light raysThe numerical aperture becomes after passing through the taper region 25The numerical aperture of the part of light does not exceed the limit of the total reflection condition of the cladding-light absorber interface, and the part of light is bound in the pumping optical fiber bundle to be conducted and does not enter the light absorber 2, and the numerical aperture of the part of light also meets the cladding light conduction condition of the multi-cladding output optical fiber 3, so the part of light meets the cladding light conduction condition of the multi-cladding output optical fiber 3The split light can be successfully coupled into the cladding of the multi-clad output fiber 3 by melting point. Thus, the refractive index of the absorber 2 is setLess than the cladding index of the fibers in the input bundle 1And isAndsatisfyThe beam combiner structure shown in fig. 2 can separate the pumping waste light from the light path capable of conducting light, and the pumping waste light is filtered in advance, so that the heat load of the coating layer of the multi-cladding output fiber is greatly relieved.

In summary, the low temperature rise optical fiber pump beam combiner disclosed by the invention can filter the pump waste light in advance before the pump waste light enters the multi-clad output optical fiber, reduces the coating heating caused by the pump waste light entering the multi-clad output optical fiber, and provides possibility for improving the power output of the laser.