CN214478414U

CN214478414U - Gain fiber cascaded fiber laser amplifier

Info

Publication number: CN214478414U
Application number: CN202120962792.6U
Authority: CN
Inventors: 楚秋慧; 李峰云; 陶汝茂; 舒强; 颜冬林; 张昊宇; 郭超; 董克攻; 林宏奂
Original assignee: Laser Fusion Research Center China Academy of Engineering Physics
Current assignee: Laser Fusion Research Center China Academy of Engineering Physics
Priority date: 2021-05-07
Filing date: 2021-05-07
Publication date: 2021-10-22
Anticipated expiration: 2031-05-07

Abstract

The utility model discloses a gain fiber cascade's optic fibre laser amplifier, this optic fibre laser amplifier includes: the device comprises a seed source, a cladding light stripper I, a pumping source I, a pumping buncher I, a gain fiber II, a pumping buncher II, a pumping source II, a cladding light stripper II and an output end cap, wherein the seed source, the cladding light stripper I, the pumping buncher I, the gain fiber II, the pumping buncher II, the pumping source II, the cladding light stripper II and the output end cap are sequentially connected, and the radius of a fiber core of the gain fiber I is smaller than that of the fiber core of the gain fiber II. The utility model discloses a gain fiber cascade's optic fibre laser amplifier utilizes the different gain fiber cascade of two-stage fibre core diameter, restraines when realizing nonlinear effect and MI effect, improves single mode fiber laser's output, and system structure is simple, and is with low costs, can realize using on a large scale.

Description

Gain fiber cascaded fiber laser amplifier

Technical Field

The utility model belongs to the laser instrument field especially relates to an optic fibre laser amplifier.

Background

The fiber laser has the advantages of high conversion efficiency, good beam quality, convenient heat management, compact structure and the like, and has good application prospect in the fields of remote welding, three-dimensional cutting, laser marking, precision machining and other industries and national defense. In recent years, with the development of a large mode field area double-clad doped fiber manufacturing process and a high-brightness laser diode pumping technology, the output power of a single-mode double-clad fiber laser is continuously improved. However, when the output power of the fiber laser is increased to several kilowatts, the power density in the fiber core is high, and nonlinear effects (such as stimulated raman scattering and stimulated brillouin scattering) are easily generated, thereby limiting the increase of the output power of the fiber laser. In order to suppress the nonlinear effect, a large mode field fiber is generally adopted to reduce the power density, a plurality of laser modes can be simultaneously conducted in the large mode field fiber, and when the output power reaches a threshold value, the Mode Instability (MI) effect can be generated by the laser due to the mutual interference between a fundamental mode and a high-order mode, so that the beam quality of the laser is reduced. Therefore, there is a conflicting relationship between the nonlinear effect and the MI effect in the optical fiber, and the nonlinear threshold is low when the fiber size of the optical fiber amplifier is small, and the MI threshold is low when the fiber size is large.

The conventional fiber laser amplifier usually adopts a single gain fiber as a gain medium, and is not beneficial to the suppression of the nonlinear effect when the fiber core diameter of the fiber is smaller, and is not beneficial to the suppression of MI when the fiber core diameter of the fiber is larger, so that the output power of the single-mode fiber laser is limited. In recent years, in order to simultaneously suppress the nonlinear effect and the MI effect in the optical fiber, researchers have proposed to optimize the optical fiber design by using various schemes such as a center-doped optical fiber, a tapered optical fiber, a low numerical aperture optical fiber, etc., but this has made a high demand on the manufacturing process of the optical fiber, and the optical fiber has high manufacturing cost and complexity, which is not suitable for large-scale use.

Therefore, there is a need for a fiber laser amplifier capable of achieving both suppression of nonlinear effects and MI effects with a simple structure.

Disclosure of Invention

In view of this, the utility model discloses based on current amplifier structure, propose to restrain nonlinear effect and MI effect simultaneously with two kinds of gain fiber cascade's mode, system's simple structure, it is with low costs, can realize extensive application.

To achieve the purpose, the utility model adopts the following technical proposal: a gain fiber cascaded fiber laser amplifier, the fiber laser amplifier comprising: the seed source, the cladding light stripper I, the pumping source I, the pumping buncher I, the gain fiber II, the pumping buncher II, the pumping source II, the cladding light stripper II and the output end cap are connected in sequence, and the fiber core radius of the gain fiber I is smaller than that of the gain fiber II.

Preferably, the lengths and core radii of the gain fibers I and II can be adjusted.

Preferably, the diameter range of the fiber cores of the gain fiber I and the gain fiber II is 10-30 μm, and the diameter of the cladding is 250-900 μm.

Preferably, the gain fibers I and II include, but are not limited to, ytterbium-doped fibers, erbium-doped fibers, thulium-doped fibers, and polarization-maintaining gain fibers.

Preferably, the pump source I and the pump source II include, but are not limited to, a laser diode pump source and a fiber laser pump source.

Preferably, the fiber laser amplifier may be a unidirectional pump fiber laser amplifier in which gain fibers are cascaded, and the unidirectional pump fiber laser amplifier has only one set of cladding light stripper, pump source and pump buncher.

The utility model has the advantages that: the utility model discloses a gain fiber cascaded's optic fibre laser amplifier utilizes the different gain fiber cascades of two-stage fibre core diameter, restraines when realizing nonlinear effect and MI effect, improves single mode fiber laser's output. The fiber core radius of the gain fiber I in the two-stage gain fiber is smaller than that of the gain fiber II, the gain fiber II is more beneficial to inhibiting the nonlinear effect, the gain fiber I is more beneficial to inhibiting the MI effect, and in addition, the lengths of the gain fiber I and the gain fiber II can be adjusted according to the main limited factor of the power increase of the laser amplifier. The utility model discloses a gain fiber cascade's optic fibre laser amplifier system simple structure, it is with low costs, can realize using on a large scale.

Drawings

Fig. 1 is a schematic structural diagram of a bidirectional pumped fiber laser amplifier with a middle gain fiber cascade according to the present invention;

in the figure: 1. the seed source 2, the cladding light stripper I3, the pump source I4, the pump buncher I5, the gain fiber I6, the gain fiber II 7, the pump buncher II 8, the pump source II 9, the cladding light stripper II 10 and the output end cap.

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 it is to be understood that the scope of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the teachings of the present embodiments without departing from the spirit of the present invention, and such modifications and combinations are still within the scope of the present invention.

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

A gain fiber cascaded fiber laser amplifier, the amplifier being a bi-directionally pumped fiber laser amplifier, the laser amplifier comprising: the optical fiber core-pulling type seed source comprises a seed source 1, a cladding light stripper I2, a pumping source I3, a pumping buncher I4, a gain optical fiber I5, a gain optical fiber II 6, a pumping buncher II 7, a pumping source II 8, a cladding light stripper II 9 and an output end cap 10, wherein the seed source 1, the cladding light stripper I2, the pumping source I3, the pumping buncher I4, the gain optical fiber I5, the gain optical fiber I16, the pumping buncher II 7, the pumping source II 8, the cladding light stripper II 9 and the output end cap 10 are sequentially connected, and the core radius of the gain optical fiber I5 is smaller than the core radius of the gain optical fiber II 6. The gain fiber I5 and the gain fiber II 6 are amplification stages of a seed source, the gain fiber of the amplification stage is used as a gain medium to provide amplification, the pump/signal buncher injects pump light into the gain fiber and transmits signal light, the cladding light stripper strips residual pump light and the signal light leaked into the cladding, and the laser is output through the end cap.

The lengths of the gain fibers I5 and II 6 and the core radiuses of the gain fibers I5 and II 6 are adjustable.

In the system, the core diameter of the gain fiber I5 is smaller than that of the gain fiber II 6, so that the pump absorption coefficient per unit length of the gain fiber I5 is smaller than that of the gain fiber II 6 under the same doping concentration, and if the two gain fibers reach the same total absorption, the length of the gain fiber II 6 is shorter. The core size of the gain fiber II 6 is larger and therefore more favorable for suppression of nonlinear effects, while the gain fiber I5 is more favorable for suppression of MI effects. Therefore, when the main limiting factor of laser power increase is nonlinear effect, we should shorten the length of the gain fiber I5 and correspondingly increase the length of the gain fiber II 6, so as to achieve suppression of the nonlinear effect. When the main limiting factor of laser power boost is MI, we should increase the length of gain fiber I5 and decrease the length of gain fiber II 6 to achieve MI suppression. In practical application, the sizes of fiber cores and cladding layers of the gain fibers I5 and II 6 and the lengths of the fibers are optimized, so that the nonlinear effect and the MI effect can be simultaneously inhibited, and the output power of the single-mode fiber laser is improved.

The core diameters of the gain fibers I5 and II 6 are 10-30 μm, and the cladding diameters are 250-900 μm.

The gain fibers I5 and II 6 include, but are not limited to, ytterbium-doped fibers, erbium-doped fibers, thulium-doped fibers, and polarization-maintaining gain fibers.

The pump source I3 and the pump source II 8 include, but are not limited to, a laser diode pump source and a fiber laser pump source.

The optical fiber laser amplifier can be a unidirectional pumping optical fiber laser amplifier with gain optical fiber cascade, and when the optical fiber laser amplifier is the unidirectional pumping optical fiber laser amplifier, the optical fiber laser amplifier only has one group of cladding light stripper, pumping source and pumping buncher.

Claims

1. A gain fiber cascaded fiber laser amplifier, the fiber laser amplifier comprising: the seed source, the cladding light stripper I, the pumping source I, the pumping buncher I, the gain fiber II, the pumping buncher II, the pumping source II, the cladding light stripper II and the output end cap are connected in sequence, and the fiber core radius of the gain fiber I is smaller than that of the gain fiber II.

2. The gain fiber cascaded fiber laser amplifier according to claim 1, wherein the lengths and core radii of the gain fibers I and II are adjustable.

3. The gain fiber cascaded fiber laser amplifier according to claim 1, wherein the core diameters of the gain fiber I and the gain fiber II are in the range of 10-30 μm, and the cladding diameters are in the range of 250-900 μm.

4. The gain fiber cascaded fiber laser amplifier of claim 1, wherein the gain fiber I and the gain fiber II comprise but are not limited to ytterbium-doped fiber, erbium-doped fiber, thulium-doped fiber, and polarization-maintaining gain fiber.

5. The gain fiber cascaded fiber laser amplifier of claim 1, wherein the pump source I and the pump source II comprise, but are not limited to, a laser diode pump source, a fiber laser pump source.

6. The gain fiber cascaded fiber laser amplifier of claim 1, wherein the fiber laser amplifier is a unidirectional pump fiber laser amplifier of the gain fiber cascaded amplifier, and the unidirectional pump fiber laser amplifier has only one set of cladding light stripper, pump source and pump buncher.