阅读说明：本技术 一种基于级联泵浦结构的多次泵浦全光纤激光器 (Multi-pumping all-fiber laser based on cascade pumping structure ) 是由 陈永骞 岳永高 邓丽娟 崔陆军 于 2020-06-08 设计创作，主要内容包括：本发明公开了一种基于级联泵浦结构的多次泵浦全光纤激光器,包括：一级激光产生模块以及第二光纤光栅、第二增益光纤、以及第三光纤光栅组成的主激光产生模块,一级激光在一级激光模块以及主激光模块之间进行多次反射,使得一级激光多次经过主激光器,形成多次泵浦结构。本发明中实现的主激光模块可以极大的降低光纤所使用的长度,从而降低激光器成本,同时可以降低光纤激光器中的非线性效应,降低激光器的损伤风险。(The invention discloses a multi-pumping all-fiber laser based on a cascade pumping structure, which comprises: the primary laser generates the module and the second fiber grating, the second gain fiber and the third fiber grating constitutes the main laser generation module, the primary laser carries out multiple reflection between the primary laser module and the main laser module, so that the primary laser passes through the main laser many times, and a multiple pumping structure is formed. The main laser module realized in the invention can greatly reduce the used length of the optical fiber, thereby reducing the cost of the laser, simultaneously reducing the nonlinear effect in the optical fiber laser and reducing the damage risk of the laser.)

1. A multi-pumping all-fiber laser based on a cascade pumping structure is characterized by comprising: the device comprises a primary laser generation module, a second fiber grating, a second gain fiber and a third fiber grating, wherein the primary laser generation module generates primary laser and comprises a pumping source, a first fiber grating, a first gain fiber and a second fiber grating, the pumping source is incident to the first gain fiber through the first fiber grating, and the first gain fiber absorbs pumping light to emit the primary laser; the first-order laser enters the second gain fiber through the second fiber grating, is partially absorbed by the second gain fiber and is converted into main laser, and the main laser is emitted through the third fiber grating.

2. The laser of claim 1, wherein the second fiber grating is highly reflective to pump light output by the pump source and highly reflective to the first-order laser light; the second fiber grating is highly transparent to the first-order laser and highly reflective to the main laser.

3. The laser of claim 1, wherein the third fiber grating is highly reflective to the primary laser light 8 and highly transmissive to the primary laser light.

4. The laser of claim 1, wherein the second gain fiber does not absorb the primary laser light.

5. The laser of claim 1, wherein the primary laser is emitted from the second fiber grating into the second gain fiber, a portion of the primary laser is absorbed by the second gain fiber, and the remaining portion of the primary laser is reflected by the third fiber grating, passes through the second gain fiber, the second fiber grating and the first gain fiber, enters the first fiber grating, is reflected by the first fiber grating, returns to the first gain fiber, passes through the second fiber grating, enters the second gain fiber 5, and is repeated for a plurality of times, so as to achieve a plurality of pumping purposes.

6. A multi-pumping all-fiber laser based on a cascade structure is characterized by comprising: the multi-group primary laser generation module, the second fiber grating, the second gain fiber and the third fiber grating comprise a pumping source, a first fiber grating and a first gain fiber; each group of primary laser generation modules generates primary laser to be combined, wherein a pumping source enters a first gain fiber through a first fiber grating, and the first gain fiber absorbs the pumping light to emit the primary laser; the first-order laser enters the second gain fiber through the second fiber grating, is absorbed by the second gain fiber and is converted into main laser, and the main laser is emitted through the third fiber grating.

Technical Field

The invention belongs to the technical field of laser, and particularly relates to a multi-pumping all-fiber laser based on a cascade pumping structure.

Background

With the rapid development of laser technology, fiber lasers are widely applied to continuously operating and quasi-continuously operating lasers with huge cost advantages and performance advantages, the fiber lasers close to the diffraction limit at present have realized the continuous output of a single optical fiber output exceeding 10kW, and quasi-continuous lasers with average power of hundred watt are also widely applied to the industrial fields of cutting, welding and the like.

As the output power of the fiber laser is higher, the generated heat is also higher. Research shows that the larger the surface area-volume of the laser gain medium is, the better the heat dissipation performance is. The surface area-to-volume ratio of the fiber laser can be expressed as

Where L is the length of the gain fiber and r is the radius of the gain fiber. With the development of large mode field fiber and large core diameter photonic crystal fiber, the radius r of the gain fiber is also increasing continuously, and how to reduce the length L of the fiber laser becomes an important issue in order to increase the surface area-volume ratio of the fiber laser.

On the other hand, in a high-power fiber laser, an important factor limiting the power increase is Stimulated Brillouin Scattering (SBS) generated in a quartz fiber, and particularly, the backward SBS effect easily returns laser to a pump source, causing irreversible damage to the laser. The threshold for SBS in a fiber laser can be expressed as,

wherein, g_BIs the Brillouin coefficient, A_effIs the effective area of the fiber core, L_effIs effective length L_effCan be expressed as a number of times,

wherein L is the length of the optical fiber and alpha is the absorption coefficient. As can be seen from equations (2) - (3), the longer the gain fiber length, the smaller the threshold power of SBS, and the more susceptible the fiber laser is to damage from the SBS effect.

In summary, reducing the length of the gain fiber in the fiber laser is an effective solution for further increasing the output power of the fiber laser. Much work has been done in this respect at present, for example, in 2015, b.rosenstein et al realized laser output of a fiber laser with a length of only 10cm using a spatial multiple pumping scheme. But the single-pass loss of the scheme is large (> 15%), and the scheme is not an all-fiber structure and has poor stability. Therefore, how to obtain a short-length fiber laser with high stability and small loss is a very important problem.

Disclosure of Invention

The invention aims to solve the technical problem of providing a multi-pumping all-fiber laser based on a multi-pass pumping structure to realize an all-fiber structure fiber laser with low loss and short length, and aims to solve the problem of SBS damage caused by overlong fiber length in the prior art and provide better heat dissipation performance.

The present invention is achieved in such a way that,

a multi-pumping all-fiber laser based on a cascade structure comprises: the optical fiber grating comprises a pumping source, a first optical fiber grating, a first gain optical fiber, a second optical fiber grating, a second gain optical fiber and a third optical fiber grating, wherein the pumping source is incident to the first gain optical fiber through the first optical fiber grating, and the first gain optical fiber absorbs pumping light to emit primary laser; the first-order laser enters the second gain fiber through the second fiber grating 4, is partially absorbed by the second gain fiber and is converted into main laser, and the main laser is emitted through the third fiber grating.

Furthermore, the second fiber bragg grating has high anti-reflection on the pump light output by the pump source and high reflection on the first-order laser; the second fiber grating is highly transparent to the first-order laser and highly reflective to the main laser.

Further, the third fiber grating is highly reflective to the first-order laser 8 and highly transparent to the main laser.

Further, the second gain fiber does not absorb the primary laser light.

Further, the primary laser is emitted from the second fiber grating to the second gain fiber, one part of the primary laser is absorbed by the second gain fiber, the rest part of the primary laser is reflected by the third fiber grating, enters the first fiber grating through the second gain fiber, the second fiber grating and the first gain fiber, is reflected by the first fiber grating, returns to the first gain fiber, enters the second gain fiber 5 through the second fiber grating, and is repeatedly pumped for multiple times.

A multi-pumping all-fiber laser based on a cascade structure comprises: the multi-group primary laser generation module, the second fiber grating, the second gain fiber and the third fiber grating comprise a pumping source, a first fiber grating and a first gain fiber; each group of primary laser generation modules generates primary laser to be combined, wherein a pumping source enters a first gain fiber through a first fiber grating, and the first gain fiber absorbs the pumping light to emit the primary laser; the first-order laser enters the second gain fiber through the second fiber grating, is absorbed by the second gain fiber and is converted into main laser, and the main laser is emitted through the third fiber grating.

Compared with the prior art, the invention has the beneficial effects that:

(1) the length of the gain fiber in the main laser is reduced, and the cost of the laser is reduced. For the main laser, the gain fiber is generally selected from a large mode field fiber or a large-caliber photonic crystal fiber with high cost. Therefore, the laser cost can be effectively reduced by reducing the length of the gain fiber in the main laser.

(2) The threshold values of Stimulated Brillouin Scattering (SBS) and Stimulated Raman Scattering (SRS) are increased, and the damage probability of the backward SBS is reduced.

(3) Compared with the existing free space multi-pumping fiber laser, the all-fiber structure of the invention not only can take the advantages of multi-pumping into account, but also greatly reduces the coupling loss in the multi-pumping process.

(4) The average heat accumulation of the laser can be effectively reduced. The cascade structure used can distribute the heat accumulation from the quantum defect into one or more primary lasers, as shown in fig. 3. Because the pumping efficiency of the conventional cascade pump laser is low (the pump light only passes through the gain fiber of the main laser once or twice), in order to take account of the quantum defect and the pumping efficiency, the output laser wavelength of the first-order laser of the conventional cascade pump laser is not too long, that is, the quantum defect of the first-order laser and the main laser is not too small. The multiple pumping technology in the invention can increase the pumping efficiency, so that the main laser can pump the primary laser with long wavelength laser with lower absorption efficiency, that is, the total quantum defect (pumping source → main laser) can be more distributed into the primary laser, so that the overall heat accumulation distribution of the laser is more even, and the heat accumulation effect of the main laser is reduced.

Drawings

FIG. 1 is a schematic diagram of a multi-pumped all-fiber laser;

FIG. 2 is a schematic diagram of multiple pumping within a full fiber laser;

fig. 3 is a schematic diagram of a multi-pumped all-fiber laser based on multiple first-order laser beam combining.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.