CN112688152A - Optical fiber oscillator and optical fiber laser - Google Patents
Optical fiber oscillator and optical fiber laser Download PDFInfo
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- CN112688152A CN112688152A CN202011604572.2A CN202011604572A CN112688152A CN 112688152 A CN112688152 A CN 112688152A CN 202011604572 A CN202011604572 A CN 202011604572A CN 112688152 A CN112688152 A CN 112688152A
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Abstract
The present invention relates to an optical fiber oscillator and an optical fiber laser. The optical fiber oscillator includes: the multimode gain fiber is used for being connected with a pumping source and receiving pumping light output by the pumping source, and the pumping light comprises a multimode beam; and the multimode fiber grating group is connected with the multimode gain fiber and is used for oscillating at least five modes of beams in the multimode beams, and the oscillated multimode beams form multimode laser output. The fiber oscillator can further increase the upper limit of the output power. The fiber laser includes the fiber oscillator.
Description
Technical Field
The invention relates to the technical field of fiber laser, in particular to a fiber oscillator and a fiber laser.
Background
The materials industry requires the use of fiber lasers during processing, such as cutting or welding. The laser generating part of the fiber laser of the all-fiber structure is called a fiber oscillator.
Current fiber oscillators, generally based on the effective reflection of a fundamental transverse mode (single-mode beam), oscillate a single-mode beam to output laser light. In order to achieve effective reflection of a single-mode light beam, generally, a fiber grating based on a single-mode fiber that only supports single-mode light beam transmission, or a gain fiber based on a single-mode laser that only supports single-mode laser, or a means of bending mode selection is adopted to increase loss of a high-order mode in the gain fiber, to achieve oscillation of the single-mode light beam, and thereby to output laser light.
However, the conventional fiber oscillator has a problem of limited output power increase.
Disclosure of Invention
Accordingly, it is necessary to provide a fiber oscillator and a fiber laser that can further increase the upper limit of the output power.
A fiber oscillator comprising:
the multimode gain fiber is used for being connected with a pumping source and receiving pumping light output by the pumping source, and the pumping light comprises a multimode beam;
and the multimode fiber grating group is connected with the multimode gain fiber and is used for oscillating at least five modes of beams in the multimode beams, and the oscillated multimode beams form multimode laser output.
In one embodiment, the light beam of the at least five modes includes a fundamental transverse mode and a higher-order transverse mode, and the fundamental transverse mode and the higher-order transverse mode jointly oscillate in a resonant cavity formed by the multimode fiber grating group to output multimode laser light composed of the fundamental transverse mode and the higher-order transverse mode.
In one embodiment, the multimode fiber grating group comprises:
a first multimode fiber grating disposed at one end of the multimode gain fiber;
the second multimode fiber grating is arranged at the other end of the multimode gain fiber, the reflectivity of the second multimode fiber grating to the multimode beam is smaller than that of the first multimode fiber grating to the multimode beam, the second multimode fiber grating and the first multimode fiber grating form the resonant cavity, and the multimode laser is output through the second multimode fiber grating.
In one embodiment, the reflectivity of the multimode optical fiber grating to the multimode light beam is greater than a first reflectivity threshold value, the first reflectivity threshold value is greater than 90%, the reflectivity of the multimode optical fiber grating to the multimode light beam is less than a second reflectivity threshold value, and the second reflectivity threshold value is less than 15%.
In one embodiment, the multimode gain fiber comprises a double clad gain doped fiber.
In one embodiment, the central wavelength of the multimode fiber grating group is located in the emission spectrum range of the doped ions of the double-clad gain-doped fiber.
In one embodiment, the core size of the multimode fiber grating group is consistent with the core size of the multimode gain fiber, the numerical aperture NA of the multimode fiber grating group is consistent with the numerical aperture NA of the multimode gain fiber, and the beam mode supported by the multimode fiber grating group is the same as the beam mode supported by the multimode gain fiber.
In one embodiment, a difference between a pump light wavelength of the pump light and an absorption peak wavelength of the multimode gain fiber is smaller than a preset wavelength difference.
A fiber laser comprising the fiber oscillator as described above, further comprising:
a pump source for generating the pump light.
In one embodiment, the pump source comprises at least one of a forward pump source and a backward pump source;
when the pump source comprises the forward pump source, the forward pump source is arranged at the input end of the fiber oscillator;
when the pump source comprises the backward pump source, the backward pump source is arranged at the output end of the fiber oscillator.
According to the optical fiber oscillator and the optical fiber laser, the pump light output by the pump source is received through the multimode gain optical fiber, the pump light comprises multimode beams, the beams in at least five modes in the multimode beams are oscillated through the multimode fiber grating group, so that the multimode laser is output, and the optical fiber oscillator oscillates the beams in at least five modes simultaneously so as to output the multimode laser. In addition, the nearly flat-top light spot energy distribution of the multimode laser also solves the problem of poor processing effect during high-power processing, and improves the stability of the processing effect during high-power processing.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an optical fiber oscillator according to an embodiment;
FIG. 2 is a schematic diagram of another fiber oscillator according to an embodiment;
fig. 3 is a schematic structural diagram of a fiber laser according to an embodiment.
Detailed Description
To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, the first multimode fiber grating may be referred to as a second multimode fiber grating, and similarly, the second multimode fiber grating may be referred to as a first multimode fiber grating, without departing from the scope of the present application. The first multimode fiber grating and the second multimode fiber grating are both multimode fiber gratings, but they are not the same multimode fiber grating.
It is to be understood that "connection" in the following embodiments is to be understood as "electrical connection", "communication connection", and the like if the connected circuits, modules, units, and the like have communication of electrical signals or data with each other.
As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, as used in this specification, the term "and/or" includes any and all combinations of the associated listed items.
Referring to fig. 1, fig. 1 is a schematic structural diagram of an optical fiber oscillator according to an embodiment. In one embodiment, as shown in FIG. 1, a fiber oscillator is provided that includes a multimode gain fiber 110 and a multimode fiber grating group 120. Wherein:
the multimode gain fiber 110 is configured to be connected to a pump source 200 and receive pump light output by the pump source 200, where the pump light includes a multimode beam. The multimode fiber grating group 120 is connected to the multimode gain fiber 110, and the multimode fiber grating group 120 is configured to oscillate at least five types of light beams in the multimode light beam, where the oscillated multimode light beam forms a multimode laser output.
The pumping source 200 is used for exciting the laser working substance and pumping the excited particles from a ground state to a high energy level to realize the population inversion. In this embodiment, the pump source 200 is used to provide pump light to the fiber oscillator. The pump light of the present embodiment includes a multimode beam. A multimode beam refers to a beam having multiple modes. Multimode gain fiber 110 refers to a fiber that transmits multiple modes of light at a given operating wavelength. In the present embodiment, since the pump light output by the pump source 200 includes a multimode beam, the beam received by the multimode gain fiber 110 is a multimode beam, i.e., the input of the fiber oscillator is a multimode beam. The multimode fiber grating group 120 refers to a composition of one or more elements that oscillate beams of at least five modes in a multimode beam. In this embodiment, a cavity is formed in the multimode fiber grating group 120, so that at least five modes of the multimode beams oscillate in the cavity to form a multimode laser output.
In the present embodiment, the multimode fiber grating group 120 oscillates at least five modes of the multimode beam, i.e., the multimode fiber grating selectively oscillates some or all of the multimode beam. Specifically, the multimode beam forms a standing wave with the fiber grating as a node under the oscillation action of the multimode fiber grating group 120. As can be seen from the standing wave conditions, the light beam that can be intensified under the action of oscillation needs to satisfy the following conditions:
Therefore, the beam whose wavelength does not satisfy the above condition is quickly eliminated by the attenuation, thereby oscillating the beams of at least five modes among the multimode beams.
Specifically, the multimode gain fiber 110 receives the pump light output from the pump source 200 and transmits the pump light to the multimode fiber grating group 120. The multimode fiber grating group 120 oscillates at least five modes of the multimode beams, and the at least five modes of the multimode beams form multimode laser output after the oscillation is strengthened.
In this embodiment, the multimode gain fiber 110 receives the pump light output by the pump source 200, the pump light includes a multimode beam, and oscillates at least five modes of the multimode beam through the multimode fiber grating group 120, so as to output a multimode laser, and the fiber oscillator oscillates at least five modes of the multimode beam simultaneously, so as to output the multimode laser. In addition, the nearly flat-top light spot energy distribution of the multimode laser also solves the problem of poor processing effect during high-power processing, and improves the stability of the processing effect during high-power processing. In addition, the fiber oscillator structure of the embodiment means that the multimode gain fiber 110 does not need to be subjected to bending mode selection of a small-hole wing, and multimode fiber gratings do not need to be designed to be in a small-hole mode selection, so that the production process is greatly simplified, the product consistency is improved, and the cost is effectively reduced.
In general, the upper limit of output power of a conventional optical fiber oscillator is about 2KW (kilowatt). Specifically, when the power is greater than 2KW, the thermally induced mode instability (TMI) of the fiber is particularly significant, greatly limiting further increases in processing power. The optical fiber oscillator of the present embodiment can increase the upper limit of the output power to 3KW by strengthening the oscillation of at least five modes of the multimode beams, so that the optical fiber oscillator of the present embodiment can also increase the upper limit of the processing power. In addition, the power output is relatively stable even at a machining power of 3 KW.
Optionally, the light beams of at least five modes in this embodiment may be five, ten or fifteen or more, and this embodiment is not particularly limited.
It is understood that the optical fiber oscillator of the present embodiment may be used in a process of cutting or welding a material, and the present embodiment is not limited to the specific application of the optical fiber oscillator.
In one embodiment, the beam of at least five modes includes a fundamental transverse mode and a higher order transverse mode. The fundamental transverse mode and the high-order transverse mode oscillate together in the resonant cavity formed by the multimode fiber grating group 120 to output multimode laser composed of fundamental transverse mode laser and high-order mode laser.
In this embodiment, the light beams of at least five modes include a fundamental transverse mode and a higher-order transverse mode, and then the multimode laser light composed of fundamental transverse mode laser light and higher-order mode laser light is output after the fundamental transverse mode and the higher-order transverse mode are oscillated and strengthened in the resonant cavity formed by the multimode fiber grating group 120.
It should be noted that the fundamental transverse mode and the high-order transverse mode are only examples of the light beams of at least five modes, and the light beams of at least five modes in this embodiment are not limited to the fundamental transverse mode and the high-order transverse mode, and the light beams of at least five modes that need to oscillate may be selected as needed.
In the present embodiment, when the light beam of at least five modes includes a fundamental transverse mode and a high-order transverse mode, the optical fiber oscillator of the present embodiment outputs a light spot shape close to a flat top, which is very advantageous in material processing. Particularly, in the aspect of metal plate cutting, for example, when the power is output at 3kW, the flat-top light spot is faster than the Gaussian light spot in cutting medium and thick plates, and the cut surface is finer and brighter.
In one embodiment, a difference between a pump light wavelength of the pump light and an absorption peak wavelength of the multimode gain fiber 110 is smaller than a predetermined wavelength difference.
In the present embodiment, the preset wavelength difference may be 10 nm. In this embodiment, the difference between the pump light wavelength of the pump light and the absorption peak wavelength of the multimode gain fiber 110 is smaller than the preset wavelength difference, so that the pump light wavelength is ensured to be near the absorption peak of the multimode gain fiber 110, and the fiber can be set as short as possible.
In one embodiment, the core size of the multimode fiber grating group 120 is consistent with the core size of the multimode gain fiber 110, the numerical aperture NA of the multimode fiber grating group 120 is consistent with the numerical aperture NA of the multimode gain fiber 110, and the beam mode supported by the multimode fiber grating group 120 is the same as the beam mode supported by the multimode gain fiber 110.
In the present embodiment, the core size of each multimode fiber grating in the multimode fiber grating group 120 is identical to the core size of the multimode gain fiber 110. In addition, the numerical aperture NA of each multimode fiber grating in the multimode fiber grating group 120 coincides with the numerical aperture NA of the multimode gain fiber 110. The beam mode supported by the multimode fiber grating group 120 refers to a multimode beam that can be reflected by the multimode fiber grating group 120. The beam mode supported by the multimode gain fiber 110 refers to a multimode beam that can be transmitted by the multimode gain fiber 110. For example, the multimode fiber grating group 120 can reflect the fundamental transverse mode and the higher-order transverse mode, and the multimode gain fiber 110 can transmit the fundamental transverse mode and the higher-order transverse mode. In one embodiment, the multimode gain fiber 110 supports more than 5 beam modes.
In one embodiment, the multimode fiber grating group 120 includes at least one multimode fiber grating. The following description will be given by taking an example in which the multimode fiber grating group 120 includes two multimode fiber gratings.
Referring to fig. 2, fig. 2 is a schematic structural diagram of another fiber oscillator according to an embodiment. In one embodiment, as shown in FIG. 2, the multimode fiber grating group 120 includes a first multimode fiber grating 121 and a second multimode fiber grating 122. Wherein:
the first multimode fiber grating 121 is disposed at one end of the multimode gain fiber 110; the second multimode fiber grating 122 is disposed at the other end of the multimode gain fiber 110, a reflectivity of the second multimode fiber grating 122 to the multimode beam is smaller than a reflectivity of the first multimode fiber grating 121 to the multimode beam, the second multimode fiber grating 122 and the first multimode fiber grating 121 form the resonant cavity 120, and the multimode laser is output through the second multimode fiber grating 122.
In the present embodiment, the first and second multimode Fiber gratings 121 and 122 may be Fiber Bragg Gratings (FBGs). The fiber bragg grating forms a spatially phase periodically distributed grating in the core that essentially forms a narrow band (transmissive or reflective) filter or mirror in the core. The first multimode fiber grating 121, the second multimode fiber grating 122, and the multimode gain fiber 110 between the first multimode fiber grating 121 and the second multimode fiber grating 122 form a resonant cavity. Optionally, the reflectivity of the multimode fiber grating 121 to the multimode light beam is greater than a first reflectivity threshold. The first reflectance is not limited herein, and may be 90% or more, for example, 90% or 95%. The reflectivity of the second multimode fiber grating 122 to the multimode beam is less than a second reflectivity threshold. Wherein the second reflectance threshold is below 15%. For example, the second multimode fiber grating 122 has a reflectivity for the multimode beam of between 5% and 15%. Optionally, the core sizes and the numerical apertures NA of the first multimode fiber grating 121 and the second multimode fiber grating 122 are the same. Optionally, the first multimode fiber grating 121 and the second multimode fiber grating 122 are both double-clad multimode fiber gratings. Wherein the 3dB bandwidth of the reflection spectrum of the first multimode fiber grating 121 is generally 4-12 nm; the emission 3dB bandwidth of the second multimode fiber grating 122 is generally 1-7 nm. In general, the 3dB bandwidth of the reflection spectrum of the first multimode fiber grating 121 is greater than the 3dB bandwidth of the reflection spectrum of the second multimode fiber grating 122.
Specifically, since the reflectivity of the first multimode fiber grating 121 for the multimode beam is greater than that of the second multimode fiber grating 122, the beams of at least five modes may oscillate back and forth between the first multimode fiber grating 121 and the second multimode fiber grating 122 and output the multimode laser light through the second multimode fiber grating 122. And part of the second multimode fiber beam is reflected, so that the beam always exists in the resonant cavity and keeps oscillating, and continuous laser output is realized.
In this embodiment, the first multimode fiber grating 121 is disposed at one end of the multimode gain fiber 110, the second multimode fiber grating 122 is disposed at the other end of the multimode gain fiber 110, and the reflectivity of the second multimode fiber grating 122 to the multimode beam is smaller than the reflectivity of the first multimode fiber grating 121 to the multimode beam, so that continuous high-power laser output can be realized.
The following description will be made by taking an example in which the light beam of at least five modes includes a fundamental transverse mode and a higher-order transverse mode, and how the first multimode fiber grating 121 and the second multimode fiber grating 122 oscillate the fundamental transverse mode and the higher-order transverse mode in the light beam of at least five modes simultaneously.
Specifically, the fiber bragg grating acts on the fiber core of the optical fiber through laser with special wavelength or special energy, and applies short-interval axial periodic refractive index modulation, so that forward-propagating fiber core laser and backward-propagating fiber core laser are coupled with each other, and laser with specific wavelength is reflected. By optimizing the maximum refractive index modulation coefficient and the length of the fiber grating and utilizing the one-to-one correspondence relationship between the modes and the wavelengths, the multimode fiber with the reflection peak of the high-order transverse mode and the reflection peak of the fundamental transverse mode can be manufactured. The Bragg wavelength calculation method comprises the following steps:
λB＝2neffΛ；
wherein n iseffIs the core effective index and Λ is the grating period. Multimode fiber gratings have different n for different high-order transverse modes and different fundamental transverse modeseffThus, for a particular grating period, different high-order transverse modes and the fundamental transverse mode correspond to different bragg wavelengths, i.e. different spectral reflection peaks. When designing the multimode fiber grating, the spectral reflection peaks of the different high-order modes and the fundamental transverse mode of the first multimode fiber grating 121 and the second multimode fiber grating 122 are matched, so that an effective grating pair can be formed, and the effective grating pair and the multimode gain fiber 110 in the first multimode fiber grating 121 and the second multimode fiber grating 122 form a fiber oscillator for oscillating light beams of at least five modes.
In one embodiment, the multimode gain fiber 110 comprises a double clad gain doped fiber. The double-clad gain-doped fiber comprises a doped fiber core, an inner cladding, an outer cladding, a protective layer and the like. Compared with the common single-mode fiber, the double-cladding doped fiber has the advantages that the single-mode fiber condition is met between the fiber core and the inner cladding, the outer cladding with a low refractive index is further arranged, a multimode optical waveguide layer is formed between the two cladding layers, the refractive index of the outer cladding is smaller than that of the inner cladding, the refractive index of the inner cladding is smaller than that of the fiber core, the transverse size and the numerical aperture of the inner cladding are far larger than those of the fiber core, and therefore high-power multimode semiconductor laser can be pumped into the fiber easily and is limited to be transmitted in the inner cladding without diffusion, and the high-power density optical pump is kept.
Optionally, the double-clad gain-doped fiber of this embodiment includes, but is not limited to, at least one of thulium-doped, ytterbium-doped, holmium-doped, erbium-doped, and the like.
In one embodiment, the center wavelength of the multimode fiber grating group 120 is located within the emission spectrum of the dopant ions of the double-clad gain-doped fiber.
In this embodiment, the normal output of the multimode laser can be ensured by setting the central wavelength of the multimode fiber grating group 120 to be within the emission spectrum range of the doped ions of the double-clad gain-doped fiber.
In this embodiment, the central wavelength of the multimode fiber grating group 120 is optionally between 1000nm and 2200 nm.
Referring to fig. 3, fig. 3 is a schematic structural diagram of a fiber laser according to an embodiment. In one embodiment, as shown in fig. 3, a fiber laser is provided comprising a fiber oscillator 100 and a pump source 200. The optical fiber oscillator 100 may refer to the description of any of the above embodiments, which is not repeated herein. The pump source 200 is used to generate the pump light.
Specifically, the pump source 200 generates pump light, and the pump light is injected into the fiber oscillator 100 through the multimode gain fiber 110, and the fiber oscillator 100 oscillates at least five modes of light beams according to the pump light injected by the pump source 200, thereby forming multimode laser output. Alternatively, the pump source 200 of the present embodiment may be a semiconductor laser.
In one embodiment, the pump source 200 includes at least one of a forward pump source 200A and a backward pump source 200B. Wherein:
when the pump source 200 includes the forward pump source 200A, the forward pump source 200A is disposed at the input end of the fiber oscillator 100; when the pump source 200 includes the backward pump source 200B, the backward pump source 200B is disposed at the output end of the fiber oscillator 100.
In the present embodiment, the output end of the fiber oscillator 100 refers to an end that outputs multimode laser light. The input end of the fiber oscillator 100 refers to the other end opposite to the output end of the fiber oscillator 100.
In one embodiment, the fiber laser further comprises a pump combiner 300. The internal structure of the pump combiner 300 is generally an all-fiber structure, the fibers are generally bonded by direct fusion, and the structure formed by the direct fusion coupling of the end face and the lateral fusion affinity may be referred to as the pump combiner 300. The pump combiner 300 has high integration level, high stability, high sustainable power and high affinity efficiency. With the development of all-fiber lasers, the pump combiner 300 has been applied to various fiber lasers as the most important means of pump coupling. When the pump source 200 includes a forward pump source 200A and a backward pump source 200B, the pump combiner 300 includes a forward pump combiner 300A and a backward pump combiner 300B.
In one embodiment, the devices of the above embodiments are all fiber-integrated devices, and the fiber-integrated devices are connected together by a fiber fusion technique, so as to ensure that the fiber oscillator 100 of the embodiment has an all-fiber structure.
The multimode ytterbium-doped fiber having a numerical aperture NA of 0.15, an inner core diameter of 20 μm, and an outer core diameter of 400 μm is exemplified as the multimode gain fiber 110. First, the laser beam is injected into the resonant cavity by the forward pump beam combiner 300A and/or the backward pump beam combiner 300B using the pump source 200 with a central wavelength of 973 nm. The specifications of the forward pump combiner 300A and the reverse pump combiner 300B are (6+1) × 1, the number of pump arm fibers is 6, the specification of the pump arm fibers is 200/220um, and the output power of a single pump source 200 is 320W. The total number of the forward pump source 200A and the backward pump source 200B is 12, and a total of 320W 12W 3840W pump light is injected into the resonant cavity. The pump light absorption peak of the ytterbium-doped fiber is 976nm, about 1.5dB/m, the length is about 20 m, and the pump light can be effectively absorbed. The core of the ytterbium-doped fiber has a diameter of 20 μm, and the numerical aperture NA of the core is 0.15, so that the number of modes supporting laser transmission is 12. The diameters and numerical apertures NA of the passive fibers of the first multimode fiber grating 121 and the second multimode fiber grating 122 are the same as those of the gain fiber, so that the loss of the whole resonant cavity is ensured to be low. The first multimode fiber grating 121 has a center wavelength of 1080nm, a 3dB bandwidth of 6nm, and a reflectivity of 97% for multimode beams. The second multimode fiber grating 122 has a center wavelength of 1080nm, a 3dB bandwidth of 1nm, and a reflectivity of 10% for multimode light beams. According to the light conversion efficiency of 80%, the laser with the wavelength of 1080nm of 3072W can be finally obtained, the mode instability phenomenon and stimulated Raman scattering do not exist, the optical nonlinear effect is effectively inhibited, and the upper limit of the output power is improved.
The fiber oscillator and the fiber laser can be used for processing materials, such as cutting or welding, and are not limited herein.
In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A fiber oscillator, comprising:
the multimode gain fiber is used for being connected with a pumping source and receiving pumping light output by the pumping source, and the pumping light comprises a multimode beam;
and the multimode fiber grating group is connected with the multimode gain fiber and is used for oscillating at least five modes of beams in the multimode beams, and the oscillated multimode beams form multimode laser output.
2. The fiber oscillator of claim 1, wherein the beam of at least five modes includes a fundamental transverse mode and a higher-order transverse mode, the fundamental transverse mode and the higher-order transverse mode co-oscillating within a cavity formed by the multimode fiber grating group to output multimode laser light composed of the fundamental transverse mode and the higher-order transverse mode.
3. The fiber oscillator of claim 1, wherein the multimode fiber grating group comprises:
a first multimode fiber grating disposed at one end of the multimode gain fiber;
the second multimode fiber grating is arranged at the other end of the multimode gain fiber, the reflectivity of the second multimode fiber grating to the multimode beam is smaller than that of the first multimode fiber grating to the multimode beam, the second multimode fiber grating and the first multimode fiber grating form the resonant cavity, and the multimode laser is output through the second multimode fiber grating.
4. The fiber oscillator of claim 3, wherein the first multimode fiber grating has a reflectivity for the multimode beam that is greater than a first reflectivity threshold of 90% or greater, and the second multimode fiber grating has a reflectivity for the multimode beam that is less than a second reflectivity threshold of 15% or less.
5. The fiber oscillator of claim 1, wherein the multimode gain fiber comprises a double clad gain doped fiber.
6. The fiber oscillator of claim 5, wherein the center wavelength of the multimode fiber grating group is within the emission spectrum of the dopant ions of the double-clad gain-doped fiber.
7. The fiber oscillator of claim 1, wherein the multimode fiber grating group has a core size corresponding to a core size of the multimode gain fiber, a numerical aperture NA of the multimode fiber grating group corresponds to a numerical aperture NA of the multimode gain fiber, and the multimode fiber grating group supports a beam mode identical to a beam mode supported by the multimode gain fiber.
8. The fiber oscillator of any of claims 1-7, wherein a difference between a pump light wavelength of the pump light and an absorption peak wavelength of the multimode gain fiber is less than a predetermined wavelength difference.
9. A fiber laser comprising the fiber oscillator according to any one of claims 1 to 8, further comprising:
a pump source for generating the pump light.
10. The fiber laser of claim 9, wherein the pump source comprises at least one of a forward pump source and a backward pump source;
when the pump source comprises the forward pump source, the forward pump source is arranged at the input end of the fiber oscillator;
when the pump source comprises the backward pump source, the backward pump source is arranged at the output end of the fiber oscillator.
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| CN114122898A (en) * | 2021-11-25 | 2022-03-01 | 光惠（上海）激光科技有限公司 | Multimode high-power fiber laser and method for inhibiting stimulated Raman scattering effect |
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| CN114122898A (en) * | 2021-11-25 | 2022-03-01 | 光惠（上海）激光科技有限公司 | Multimode high-power fiber laser and method for inhibiting stimulated Raman scattering effect |
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