CN115483601B - Thulium-doped optical fiber amplifier device based on mode control and non-uniform gain ultra-large mode field - Google Patents

Abstract

Based on mode control and a non-uniform gain ultra-large mode field thulium-doped optical fiber amplifier device, a non-uniform pumping mode is adopted, a second, a third, a fourth, a fifth, a sixth and a seventh multi-mode tail fiber output laser diodes provide sufficient pumping light power for the amplifier, and a second optical fiber beam combiner couples pumping light output by the second, the third, the fourth, the fifth, the sixth and the seventh multi-mode tail fiber output laser diodes and signal light output by an all-fiber oscillator; the front section of highly-doped large-mode-field thulium-doped optical fiber provides enough signal light for the rear section of highly-doped large-mode-field thulium-doped optical fiber, and the rear section of highly-doped large-mode-field thulium-doped optical fiber ensures sufficient pumping absorption and high power generation; the second cladding light filter filters the pump light in the cladding to obtain pure signal light; the end cap with the fiber pigtail reduces the output laser power density at the fiber end face.

Description

Ultra-Large Mode Field Thulium-Doped Fiber Amplifier Device Based on Mode Control and Inhomogeneous Gain

technical field

The invention relates to the field of laser technology, in particular to an ultra-large mode field thulium-doped fiber amplifier device based on mode control and non-uniform gain.

Background technique

In rare earth ion-doped lasers, thulium ions can produce laser output near 2 μm. The 2μm laser is in the safe wavelength band for human eyes, and has excellent performance in atmospheric transmission and smog penetration. It has been widely used in the fields of atmospheric optical communication, _remote sensing and lidar detection. ₂ O molecules and other molecular absorption, used in the earth (planetary) surface water vapor distribution measurement, infrared spectrum analysis, environmental detection, laser microsurgery and special material processing and other fields.

In order to meet the needs of these military, medical and industrial fields, designing and developing high-performance 2μm fiber lasers is the most critical step. In the 2μm fiber laser, due to the reabsorption effect, a high seed optical power is required to effectively suppress the amplified spontaneous emission. The amplified spontaneous radiation power is the main factor affecting the increase of output power. Under the MOPA structure, the amplification of spontaneous emission is accompanied by the entire amplification process, and the multi-stage amplification structure will amplify the spontaneous emission step by step, thereby limiting the power increase, reducing the signal-to-noise ratio of the system, and even inducing parasitic oscillations to burn the amplifier. In addition, large mode field fibers can cause increased modes and degraded beam quality. Therefore, it is necessary to take certain measures to suppress the amplified spontaneous emission and improve the beam quality. How to improve the output power, signal-to-noise ratio, beam quality, and suppress the amplification of spontaneous emission is an urgent problem to be solved.

Contents of the invention

In order to overcome the defects of the prior art, the technical problem to be solved by the present invention is to provide a super-large mode field thulium-doped fiber amplifier device based on mode control and non-uniform gain, which has a compact structure, simplifies the optical path structure, and does not introduce new devices , which greatly enhances the stability and practicability of the laser, improves the output power, beam quality and signal-to-noise ratio without increasing the overall weight of the system, further reduces the volume of the laser, and can be used stably and effectively in various fields for a long time.

The technical solution of the present invention is: the ultra-large mode field thulium-doped fiber amplifier device based on mode control and non-uniform gain, which includes: an all-fiber oscillator (10), a thulium-doped fiber amplifier (20);

The all-fiber oscillator includes: a first multimode pigtail output laser diode (11), a high reflection fiber Bragg grating (12), a first fiber combiner (13), a highly doped single-mode thulium-doped fiber (14), Partially reflective fiber Bragg grating (15), first cladding optical filter (16), first fiber isolator (17); the first fiber combiner outputs the first multimode pigtail output laser diode output pump The light is coupled into the resonant cavity, the high reflective fiber Bragg grating and the partially reflective fiber Bragg grating are used as the two cavity mirrors of the resonant cavity, and the highly doped single-mode thulium-doped fiber is used as the gain medium to absorb the output of the first multimode pigtail output laser diode The pump light generates signal light; the laser generated by the resonator passes through the first cladding optical filter to obtain pure signal light, and the first fiber isolator protects the all-fiber oscillator to prevent the feedback light from being affected;

The thulium-doped fiber amplifier includes: the second multimode pigtail output laser diode (201), the third multimode pigtail output laser diode (202), the fourth multimode pigtail output laser diode (203), the fifth multimode pigtail output laser diode Fiber output laser diode (204), sixth multimode pigtail output laser diode (205), seventh multimode pigtail output laser diode (206), second fiber combiner (207), high doped Thulium-doped optical fiber with hetero large mode field, second cladding optical filter (211), end cap with fiber pigtail (212); second, third, fourth, fifth, sixth, seventh multimode The laser diode output from the pigtail provides sufficient pump light power for the amplifier, and the second, third, fourth, fifth, sixth, and seventh multimode fiber pigtail output laser diodes output the pumping power of the second fiber beam combiner The light is coupled with the signal light output by the all-fiber oscillator; the high-doped large-mode-field thulium-doped fiber in the front section provides enough signal light for the high-doped large-mode-field thulium-doped fiber in the back section, and the high-doped large-mode field doped fiber in the back section Thulium fiber ensures sufficient pump absorption and high power generation; the second cladding optical filter filters out the pump light in the cladding to obtain pure signal light; the end cap with fiber pigtail reduces the output laser at the fiber end face power density.

The present invention proposes a method of non-uniform pumping. The second, third, fourth, fifth, sixth, and seventh multimode pigtail output laser diodes provide sufficient pumping light power for the amplifier. The beamer couples the pump light output by the second, third, fourth, fifth, sixth, and seventh multi-mode pigtails to output the laser diode and the signal light output by the all-fiber oscillator; the high-doped large-mode The field-doped thulium fiber provides enough signal light for the rear highly doped large-mode field-doped thulium fiber, and the rear highly-doped large-mode field thulium-doped fiber ensures sufficient pump absorption and high power generation; the second cladding optical filter The filter removes the pump light in the cladding to obtain pure signal light; the end cap with fiber pigtail reduces the output laser power density of the fiber end face; the structure is compact, the optical path structure is simplified, and no new devices are introduced, which is extremely It greatly enhances the stability and practicability of the laser, improves the output power, beam quality and signal-to-noise ratio without increasing the overall weight of the system, further reduces the volume of the laser, and can be used stably and effectively in various fields for a long time.

Description of drawings

Fig. 1 is a structural schematic diagram of an ultra-large mode field thulium-doped fiber amplifier device based on mode control and non-uniform gain according to the present invention.

FIG. 2 is a schematic structural diagram of the all-fiber oscillator in FIG. 1 .

Fig. 3 is a schematic diagram of the structure of the thulium-doped fiber amplifier in Fig. 1 .

Detailed ways

In order to enable those skilled in the art to better understand the solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only It is an embodiment of a part of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terms "comprising" and any variations in the description and claims of the present invention and the above drawings are intended to cover non-exclusive inclusion, for example, processes, methods, and devices that include a series of steps or units The process, method, product or device are not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to the process, method, product or device.

As shown in Figures 1-3, this ultra-large mode field thulium-doped fiber amplifier device based on mode control and non-uniform gain includes: an all-fiber oscillator 10, a thulium-doped fiber amplifier 20;

The all-fiber oscillator includes: a first multimode pigtail output laser diode 11, a high reflection fiber Bragg grating 12, a first fiber combiner 13, a highly doped single-mode thulium-doped fiber 14, a partially reflecting fiber Bragg grating 15, a first A cladding optical filter 16, the first optical fiber isolator 17; the first optical fiber combiner couples the pumping light output by the first multimode pigtail output laser diode into the resonator, and the high reflection fiber Bragg grating and partial reflection The fiber Bragg grating is used as the two cavity mirrors of the resonator, and the highly doped single-mode thulium-doped fiber is used as the gain medium to absorb the pump light output by the first multimode pigtail output laser diode to generate signal light; the laser generated by the resonator passes through The first cladding optical filter obtains pure signal light, and protects the all-fiber oscillator through the first optical fiber isolator to prevent feedback light from being affected;

The thulium-doped fiber amplifier includes: the second multimode pigtail output laser diode 201, the third multimode pigtail output laser diode 202, the fourth multimode pigtail output laser diode 203, the fifth multimode pigtail output laser diode 204, The sixth multi-mode pigtail output laser diode 205, the seventh multi-mode pigtail output laser diode 206, the second fiber combiner 207, the highly doped large-mode-field thulium-doped fiber with gradually changing gain coefficient, and the second cladding optical filter Divider 211, end cap 212 with optical fiber pigtail; second, third, fourth, fifth, sixth, seventh multimode pigtail output laser diodes provide sufficient pump light power for the amplifier, the second optical fiber The beam combiner couples the pump light output by the second, third, fourth, fifth, sixth, and seventh multimode pigtails output by the laser diode and the signal light output by the all-fiber oscillator; The mode field thulium-doped fiber provides sufficient signal light for the back-end highly-doped large-mode-field thulium-doped fiber, and the back-end highly-doped large-mode-field thulium-doped fiber ensures sufficient pump absorption and high power generation; the second cladding light The filter filters out the pump light in the cladding to obtain pure signal light; the end cap with fiber pigtail reduces the output laser power density of the fiber end face.

The present invention proposes a method of non-uniform pumping. The second, third, fourth, fifth, sixth, and seventh multimode pigtail output laser diodes provide sufficient pumping light power for the amplifier. The beamer couples the pump light output by the second, third, fourth, fifth, sixth, and seventh multi-mode pigtails to output the laser diode and the signal light output by the all-fiber oscillator; the high-doped large-mode The field-doped thulium fiber provides enough signal light for the rear highly doped large-mode field-doped thulium fiber, and the rear highly-doped large-mode field thulium-doped fiber ensures sufficient pump absorption and high power generation; the second cladding optical filter The filter removes the pump light in the cladding to obtain pure signal light; the end cap with fiber pigtail reduces the output laser power density of the fiber end face; the structure is compact, the optical path structure is simplified, and no new devices are introduced, which is extremely It greatly enhances the stability and practicability of the laser, improves the output power, beam quality and signal-to-noise ratio without increasing the overall weight of the system, further reduces the volume of the laser, and can be used stably and effectively in various fields for a long time.

Preferably, the highly doped large-mode-field thulium-doped fiber includes: a first highly-doped large-mode-field thulium-doped fiber 208, a second highly-doped large-mode-field thulium-doped fiber 209, a third highly-doped large-mode field Thulium-doped fibers 210, which have different gain coefficients.

Preferably, the first, second, and third highly doped large-mode-field thulium-doped fibers are gain fibers with different doping concentrations and different lengths, and are polarization-maintaining fibers, non-polarization-maintaining fibers, ultra-large-mode-field fibers or single mode fiber.

Preferably, the highly doped large-mode field thulium-doped optical fiber is an optical fiber with different gain coefficient distributions. The concentration of doped rare earth ions in the optical fiber changes gradually, and the gain absorption caused by the distribution is different. The doped rare earth ion concentration at the pump input end is Low, effectively reducing the thermal effect and ensuring fiber amplification; doping rare earth ions in the middle of the fiber with a high concentration for effective gain extraction; doping rare earth ions at the output end of the fiber with a low concentration to absorb residual pump light, thereby achieving controllable gain enlarge. Because the pump light at the input end is too strong and the amplified signal light at the output end is too strong, it is easy to cause damage to the optical fiber due to too strong light and high power, so the concentration of rare earth ions doped at the input end and output end is low.

Preferably, the highly doped large-mode-field thulium-doped fiber is an ultra-large-mode-field graded fiber with a core diameter between 30 µm and 80 µm; tapering is performed at the output end of the ultra-large-mode-field fiber to reduce the core diameter.

Preferably, the highly doped large-mode field thulium-doped fiber is a variable core diameter gain fiber, including: a single tapered fiber, a spindle fiber and a saddle fiber; the variable core diameter gain fiber is a core diameter along the fiber change in length.

Preferably, the highly doped single-mode thulium-doped optical fiber is a polarization-maintaining optical fiber, a non-polarization-maintaining optical fiber, a large mode field optical fiber or a single-mode optical fiber with different doping concentrations.

Preferably, the all-fiber oscillator is a single-mode polarization-maintaining all-fiber oscillator, a single-mode non-polarization-maintaining all-fiber oscillator, a large-mode field polarization-maintaining all-fiber oscillator or a large-mode field non-polarization-maintaining all-fiber oscillator; The thulium-doped fiber amplifier is a single-mode polarization-maintaining thulium-doped fiber amplifier, a single-mode non-polarization-maintaining thulium-doped fiber amplifier, a large-mode field polarization-maintaining thulium-doped fiber amplifier or a large-mode field non-polarization-maintaining thulium-doped fiber amplifier; the all-fiber oscillation The applicable wavelength range of the device and the thulium-doped fiber amplifier is 1.9µm~2.1µm.

Preferably, the pigtail of the end cap with a fiber pigtail is a polarization-maintaining fiber, a non-polarization-maintaining fiber, an ultra-large mode field fiber or a single-mode fiber.

The concrete work process of device of the present invention is as follows:

The first fiber combiner 13 couples the pump light output by the first multimode pigtail output laser diode 11 into the resonator, and the high reflection fiber Bragg grating 12 and the partially reflective fiber Bragg grating 15 are used as two cavity mirrors of the resonator, The highly doped single-mode thulium-doped fiber 14 acts as a gain medium to absorb the pump light output by the first multimode pigtail output laser diode 11 to generate signal light. The laser light generated by the resonator passes through the first cladding optical filter 16 to obtain pure signal light, and passes through the first optical fiber isolator 17 to protect the all-fiber oscillator and prevent feedback light from being affected.

The second fiber bundle combiner 207 outputs the second multimode pigtail output laser diode 201, the third multimode pigtail output laser diode 202, the fourth multimode pigtail output laser diode 203, and the fifth multimode pigtail output laser diode 204. The pump light output by the sixth multimode pigtail output laser diode 205 and the seventh multimode pigtail output laser diode 206 are coupled with the signal light output by the all-fiber oscillator 10, and the output optical power enters the first high doped Doped large-mode-field thulium-doped fiber 208, the second highly-doped large-mode-field thulium-doped fiber 209, and the third highly-doped large-mode-field thulium-doped fiber 210 generate high-power laser light. The first highly doped large-mode-field thulium-doped fiber 208 is used to provide sufficient signal light for the second highly-doped large-mode-field thulium-doped fiber 209 and the third highly-doped large-mode-field thulium-doped fiber 210; the second high The doped large-mode field thulium-doped fiber 209 and the third highly doped large-mode field thulium-doped fiber 210 are used to ensure sufficient pump absorption and generate high power. Doping rare earth ions at the pump input end has a low concentration, which can effectively reduce the thermal effect and ensure fiber amplification; doping rare earth ions at the middle of the fiber has a high concentration for effective gain extraction; doping rare earth ions at the output end of the fiber has a higher concentration Low, the residual pump light is absorbed, enabling gain-controllable amplification. At the same time, the ultra-large mode field fiber pump has a high absorption coefficient, which can ensure efficient gain extraction, effectively improve the laser amplification efficiency, and reduce the power density of the fiber end face, so as to achieve an order of magnitude increase in output power and ensure long-term effective operation of the laser. . Tapering is performed at the output end of the ultra-large mode field fiber to reduce the core diameter, effectively achieve high power output while ensuring high beam quality, and realize quasi-single-mode laser output. The third highly doped large-mode field thulium-doped fiber 210 is connected to the second cladding light filter 211 to filter out the pump light in the cladding, and after obtaining pure signal light, the end cap 212 with the fiber pigtail is fused to reduce the optical fiber. Medium optical power density, effectively achieve long-term operation.

Beneficial technical effect of the present invention is as follows:

1. The present invention proposes a non-uniform pumping method. One is composed of multiple sections of optical fibers with different gain coefficients. The first section of optical fiber provides sufficient signal light for the second section of optical fiber, the third section of optical fiber, etc., and the second section of optical fiber , The third section of optical fiber ensures sufficient pump absorption and high power generation. An optical fiber with different distributions of gain coefficients. The concentration of doped rare earth ions in the optical fiber changes gradually, and the distribution produces different gain absorption. The concentration of doped rare earth ions at the pump input end is low, which can effectively reduce thermal effects and ensure optical fiber amplification; The middle position of the fiber is doped with a high concentration of rare earth ions for effective gain extraction; the concentration of doped rare earth ions at the output end of the fiber is low to absorb the residual pump light, thereby achieving controllable gain amplification. The technical route has a compact structure, simplifies the optical path structure, and does not introduce new devices, which greatly enhances the stability and practicability of the laser. It does not increase the overall weight of the system while improving the output power, beam quality, and signal-to-noise ratio, and further reduces the cost. The volume of the laser can be used stably and effectively in various fields for a long time.

2. The technical route of the present invention adopts the ultra-large mode field fiber core graded optical fiber, and the core diameter is between 30µm and 80µm. The optical fiber pump has a high absorption coefficient, which can ensure efficient gain extraction, effectively improve the laser amplification efficiency, and reduce the power density of the fiber end face, so as to achieve an order of magnitude increase in output power and ensure long-term effective operation of the laser. Tapering is performed at the output end of the ultra-large mode field fiber to reduce the core diameter, effectively achieve high power output while ensuring high beam quality, and realize quasi-single-mode laser output. At the same time, the device adopts the non-uniform gain method to effectively solve the problem of heat distribution in the optical fiber. The highly doped optical fiber is used to achieve efficient gain extraction, absorb more pumps, and reduce heat accumulation; the low-doped optical fiber is fused at the output end. Relieve the heat accumulation at the output end, protect the output end face, and ensure the normal operation of the laser.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention are still within the scope of this invention. The protection scope of the technical solution of the invention.

Claims (8)

1. Based on mode control and inhomogeneous gain super large mode field thulium-doped fiber amplifier device, its characterized in that: it comprises the following steps: an all-fiber oscillator (10) and a thulium-doped fiber amplifier (20);

the all-fiber oscillator includes: the optical fiber coupling device comprises a first multimode pigtail output laser diode (11), a high-reflectivity fiber Bragg grating (12), a first optical fiber combiner (13), a high-doping single-mode thulium-doped optical fiber (14), a partially-reflective optical fiber Bragg grating (15), a first cladding optical filter (16) and a first optical fiber isolator (17); the first optical fiber beam combiner couples pump light output by the laser diode output by the first multimode pigtail into the resonant cavity, the high-reflection fiber Bragg grating and the part of reflection fiber Bragg grating are used as two cavity mirrors of the resonant cavity, and the high-doping single-mode thulium-doped optical fiber is used as a gain medium and absorbs the pump light output by the laser diode output by the first multimode pigtail to generate signal light; the laser generated by the resonant cavity obtains pure signal light through the first cladding light filter, and the feedback light is prevented from being influenced by the protection of the all-fiber oscillator through the first fiber isolator;

the thulium-doped optical fiber amplifier includes: the multimode pigtail laser comprises a second multimode pigtail output laser diode (201), a third multimode pigtail output laser diode (202), a fourth multimode pigtail output laser diode (203), a fifth multimode pigtail output laser diode (204), a sixth multimode pigtail output laser diode (205), a seventh multimode pigtail output laser diode (206), a second optical fiber combiner (207), a highly-doped large-mode-field thulium-doped optical fiber with gradually-changed gain coefficient, a second cladding optical filter (211) and an end cap (212) with an optical fiber pigtail; the second optical fiber beam combiner couples the pump light output by the second, third, fourth, fifth, sixth and seventh multimode tail fiber output laser diodes and the signal light output by the all-fiber oscillator; the front section of highly-doped large-mode-field thulium-doped optical fiber provides enough signal light for the rear section of highly-doped large-mode-field thulium-doped optical fiber, and the rear section of highly-doped large-mode-field thulium-doped optical fiber ensures sufficient pumping absorption and high power generation; the second cladding light filter filters the pump light in the cladding to obtain pure signal light; the end cap with the fiber pigtail reduces the output laser power density at the fiber end face.

2. The mode-control-and-non-uniform-gain-based ultra-large mode field thulium-doped fiber amplifier device according to claim 1, wherein: the highly doped large mode field thulium doped optical fiber comprises: the high-gain optical fiber comprises a first high-doping large-mode-field thulium-doped optical fiber (208), a second high-doping large-mode-field thulium-doped optical fiber (209) and a third high-doping large-mode-field thulium-doped optical fiber (210), which have different gain coefficients.

3. The mode-control-and-non-uniform-gain-based ultra-large-mode-field thulium-doped fiber amplifier device according to claim 2, wherein: the first, second and third highly doped large mode field thulium doped fibers are gain fibers with different doping concentrations and different lengths, and are single mode fibers.

4. The mode-control-and-non-uniform-gain-based ultra-large mode field thulium-doped fiber amplifier device according to claim 1, wherein: the highly doped large-mode-field thulium-doped optical fiber is an optical fiber with different gain coefficient distributions, the concentration of doped rare earth ions of the optical fiber is gradually changed, the gain absorption generated by the distribution is different, the concentration of the doped rare earth ions at the input end of the pump is lower, the thermal effect is effectively reduced, and the amplification of the optical fiber is ensured; the concentration of doped rare earth ions at the middle position of the optical fiber is high, and effective gain extraction is carried out; the rare earth ions doped at the output end of the optical fiber have low concentration, and the residual pump light is absorbed, so that gain controllable amplification is realized.

5. The mode-control-and-non-uniform-gain-based ultra-large mode field thulium-doped fiber amplifier device according to claim 1, wherein: the highly-doped large-mode-field thulium-doped optical fiber is an ultra-large-mode-field fiber core gradient optical fiber, and the diameter of the fiber core is between 30 mu m and 80 mu m; and tapering at the output end of the ultra-large mode field optical fiber to reduce the diameter of the fiber core.

6. The mode-control-and-non-uniform-gain-based ultra-large mode field thulium-doped fiber amplifier device according to claim 1, wherein: highly dope big mode field thulium-doped optical fiber for becoming core footpath diameter gain optical fiber, include: single-taper optical fibers, spindle-shaped optical fibers, and saddle-shaped optical fibers; the variable core diameter gain fiber has a core diameter that varies along the length of the fiber.

7. The thulium doped fiber amplifier device based on mode control and non-uniform gain ultra-large mode field according to claim 1, wherein: the highly doped single-mode thulium-doped optical fiber is a single-mode optical fiber with different doping concentrations.

8. The mode-control-and-non-uniform-gain-based ultra-large mode field thulium-doped fiber amplifier device according to claim 1, wherein: the tail fiber of the end cap with the optical fiber tail fiber is a single-mode optical fiber.

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