CN114944586A - 1907nm single-mode polarization-maintaining all-fiber laser - Google Patents

Abstract

A 1907nm single-mode polarization-maintaining all-fiber laser belongs to the field of optics. The invention solves the problem of low output power of the existing polarization-maintaining single-mode thulium-doped fiber laser. It includes: a fiber oscillator and a fiber amplifier; a high-reflection fiber Bragg grating is sequentially connected to a first forward pump optical combiner, a first low-doped single-mode thulium-doped gain fiber, and a low-reflectivity fiber Bragg grating; the first pump The pump light source is connected to the pump fiber of the first forward pump optical combiner; the output end of the low-reflection fiber Bragg grating is connected to the input end of the first cladding pump optical stripper; the first cladding pump optical stripper is connected to the optical isolation in turn a second forward pump optical combiner, a second low-doped single-mode thulium-doped gain fiber and a second cladding pump light stripper, and the second pump light source is connected to the second forward pump Optical combiner pump fiber; optical isolator pigtails output linearly polarized light on the slow axis; all devices are polarization-maintaining devices. The present invention is used for fiber lasers.

Description

A 1907nm single-mode polarization-maintaining all-fiber laser

technical field

The invention relates to a 1907nm single-mode polarization-maintaining all-fiber laser, which belongs to the field of optics.

Background technique

Fiber lasers are the third generation of new lasers after traditional gas lasers and solid-state lasers. They have the advantages of compact structure, stable power, long life, maintenance-free, excellent thermal management and good beam quality. The application range of fiber lasers is very wide, including laser fiber optic communication, laser space telecommunication, industrial shipbuilding, automobile manufacturing, laser engraving, laser marking, laser cutting, printing roller, metal and non-metal drilling/cutting/welding (brazing, water quenching, cladding and deep welding), military defense security, medical equipment and equipment, large-scale infrastructure, as a pump source for other lasers, etc. Among them, the more special single-mode polarization-maintaining fiber lasers can be mainly used in communications and lasers Measurement.

A high-power thulium-doped continuous fiber laser operating in the 1.9μm eye-safe special band, with a gain bandwidth covering 1.7-2.1μm, can usually be obtained by using an erbium-ytterbium co-doped fiber laser with an output wavelength of 1550nm and a core-pumped thulium-doped fiber. 1.7 ~ 1.9μm laser, but the theoretical quantum efficiency is high when the mature 790nm laser diode cladding-pumped thulium fiber is used. Compared with the erbium-ytterbium co-doped fiber laser as the pump source, it has higher electro-optical efficiency. In terms of output power It is also more advantageous, so it has always been one of the important directions in the field of high-power laser technology. At present, random polarization multi-mode thulium-doped fiber amplifiers can achieve a power output of the kilowatt order, and the power level of random polarization single-mode thulium-doped fiber lasers has also been advanced to the order of 300W, which can meet the requirements of special material processing, clinical surgery, Requirements in many fields such as mid- and long-range lidar, holmium-doped solid-state lasers, and mid-infrared spectrum generation.

However, the existing thulium-doped polarization-maintaining single-mode fiber lasers have the problem of low output power.

When the output wavelength of the thulium-doped fiber laser is less than 1950 nm, due to the overlapping of the absorption spectrum and the emission spectrum of the thulium-doped fiber laser, there is reabsorption loss at these wavelengths, which reduces the output efficiency of the laser. In contrast, laser wavelengths longer than 1950 nm can obtain greater gain, which leads to the fact that thulium-doped lasers are prone to generate amplified spontaneous emission and parasitic oscillation when operating at short wavelengths, and high power output cannot be obtained. At the same time, the existing large-mode field gain fibers are all few-mode fibers, and high-order modes can exist in the core and gain gain to achieve amplification, but in the high-power strong nonlinear working state, due to the mode field diameter of such fibers The core diameter ratio (MFD/D) value is less than 1, the signal light field area on the cross section of the core is smaller than the core area, the laser energy density is large, the nonlinear phase difference between multiple modes is related to the power, and the self-phase modulation and Cross-phase modulation makes multiple modes superimposed coherently, which will cause the output spot distribution to no longer be Gaussian, or even the excitation mode is unstable. The direction of the output laser and the beam quality evolve randomly, limiting the further improvement of the power.

SUMMARY OF THE INVENTION

The purpose of the invention is to provide a 1907nm single-mode polarization-maintaining all-fiber laser in order to solve the problem of low output power of the existing polarization-maintaining single-mode thulium-doped fiber laser.

A 1907nm single-mode polarization-maintaining all-fiber laser proposed by the present invention comprises: a fiber oscillator and a fiber amplifier;

The fiber oscillator includes a high reflectivity fiber Bragg grating, a first forward pumping optical combiner, a first pump light source, a first low-doped single-mode thulium-doped gain fiber, and a low-reflectivity fiber Bragg grating;

The fiber amplifier includes a first cladding pump optical stripper, a second cladding pump optical stripper, an optical isolator, a mode field adapter, a second forward pump optical combiner, and a second low-doped single-mode A thulium-doped gain fiber and a second pump light source;

The output end of the high-reflectivity fiber Bragg grating is connected to the input end of the first forward pump optical combiner, the first pump light source is connected to the pump fiber of the first forward pump optical combiner, and the first forward pump optical combiner is connected. The output end of the bundler is connected to one end of the first low-doped single-mode thulium-doped gain fiber, and the other end of the first low-doped single-mode thulium-doped gain fiber is connected to the input end of the low-reflection fiber Bragg grating;

The output end of the low reflectivity fiber Bragg grating is connected to the input end of the first cladding pump light stripper;

The output end of the first cladding pumping optical stripper is connected to the optical isolator, the output pigtail of the optical isolator is connected to the mode field adapter, the output end of the mode field adapter is connected to the second forward pumping optical combiner, the second pumping The light source is connected to the pump fiber of the second forward pump optical combiner, and the signal light output pigtail of the second forward pump optical combiner is connected to one end of the second low-doped single-mode thulium-doped gain fiber. The other end of the hetero single-mode thulium-doped gain fiber is connected to the output end of the second cladding pump light stripper; the slow axis of the pigtail fiber of the optical isolator outputs linearly polarized light;

All devices are polarization maintaining devices.

Preferably, the high reflectivity fiber Bragg grating, the low reflectivity fiber Bragg grating, the first low-doped single-mode thulium-doped gain fiber and the second low-doped single-mode thulium-doped gain fiber are respectively fixed on the heat dissipation base.

Preferably, the high-reflection fiber Bragg grating and the low-reflection fiber Bragg grating are respectively fixed on different cooling platforms, and the cooling platforms are cooled by semiconductor refrigerators, and the temperature control range is -5 to 40°C.

Preferably, the other end of the first low-doped single-mode thulium-doped gain fiber is orthogonally spliced with the input end of the low-reflection fiber Bragg grating;

The output end of the low reflectivity fiber Bragg grating is orthogonally spliced with the input end of the first cladding pump light stripper;

Horizontal welding is performed between other devices.

Preferably, the fast-axis Bragg wavelength of the high-reflection fiber Bragg grating is 1907nm±0.2nm, the reflectivity is >99.5%, the transmission bandwidth is 0.5nm±0.1nm, and the pump power can be higher than 200W;

The slow-axis Bragg wavelength of the low-reflection fiber Bragg grating is 1907nm±0.2nm, the reflectivity=10±2%, the reflection bandwidth is 0.3nm±0.1nm, and the maximum signal optical power that can be tolerated is 50W;

The spectral side mode suppression ratio is >20dB, and the Bragg wavelength mismatch between the fast axis and the slow axis is <0.1nm.

Preferably, the first forward pump beam combiner is a (6+1)×1 beam combiner, the pumping efficiency is >95%, the signal light transmission loss is <0.7dB, and the core diameter of the signal fiber of the beam combiner And the cladding diameter is 10/130μm, and the pump fiber is 105/125μm;

The second forward pump optical beam combiner is a (6+1)×1 beam combiner, the pumping efficiency is >95%, the signal light transmission loss is <2dB, the polarization extinction ratio is >18dB, and the single-arm withstand power is >150W, The signal fiber is 15/250μm and the pump fiber is 200/220μm.

Preferably, the core/cladding of the first low-doped single-mode thulium-doped gain fiber is 10/130 μm, the numerical apertures of the core and the cladding are 0.14 and 0.46, respectively, and the absorption of the 793 nm pump light by the cladding is The coefficient is 4.5-4.7dB/m, and the length is 1.8m;

The core/cladding of the second low-doped single-mode thulium-doped gain fiber is 15/250 μm, the numerical apertures of the core and the cladding are 0.11 and 0.46, respectively, and the absorption coefficient of the cladding to the 793 nm pump light is 2.0 -2.1dB/m, length is 3.0m.

Preferably, the core/cladding of the first cladding pump light stripper is 10/130 μm, the transmission loss of the signal light is less than 0.2 dB, the pump light stripping efficiency is more than 22 dB, and the polarization extinction ratio is more than 20 dB;

The core/cladding of the second cladding pump light stripper is 15/250 μm, the transmission loss of the signal light is less than 0.2 dB, the pump light stripping efficiency is more than 20 dB, and the polarization extinction ratio is more than 18 dB.

Preferably, the polarization isolation degree of the optical isolator is >20dB, the single arm withstand power is 20W, the core/cladding of the signal fiber is 10/130 μm, and the slow axis of the pigtail fiber outputs linearly polarized light.

Preferably, the extinction ratio of the mode field adapter is >16dB, the doping loss is <0.9dB, the core/cladding of the pigtail at the input end is 10/130 μm, and the output end is 15/250 μm.

A 1907nm single-mode polarization-maintaining all-fiber laser proposed by the present invention has the following advantages:

1. Using polarization-maintaining devices, horizontal or orthogonal polarization-maintaining welding methods are used between the devices. Under the action of polarization-maintaining gratings, the output laser is linearly polarized light.

2. A semiconductor cooler (TEC) is used to control the temperature of the fiber grating, and the spectral offset is optimized by changing the cooling temperature of the grating, thereby improving the polarization extinction ratio of the thulium-doped fiber laser. wavelength tuning.

3. Using a 790nm laser diode as the pump source has more advantages in output power than semiconductor lasers and fiber lasers in the same band.

4. The structure of the polarization-maintaining large-mode field-gain fiber is optimized, so that the fiber laser can obtain high-power polarization-maintaining single-mode laser output; by optimizing the MFD/D, the pumping efficiency and beam quality of the laser can also be improved, and the laser output efficiency can be improved.

Description of drawings

1 is a schematic structural diagram of a 1907nm single-mode polarization-maintaining all-fiber laser according to the present invention;

Figure 2 is a schematic diagram of the polarization selection of a polarization-maintaining grating pair fused with dual PM-FBGs at 0°;

Figure 3 is a schematic diagram of the polarization selection of a polarization-maintaining grating pair fused by double PM-FBG at 90°;

Fig. 4 is the output power curve of thulium-doped single-mode polarization-maintaining oscillator seed source in the present invention;

Fig. 5 is the output power curve of the thulium-doped single-mode polarization-maintaining all-fiber amplifier in the present invention;

Fig. 6 is the output spectrogram of the thulium-doped single-mode polarization-maintaining all-fiber amplifier in the present invention;

FIG. 7 is the beam quality and spot profile of the thulium-doped single-mode polarization-maintaining all-fiber amplifier in the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict.

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but it is not intended to limit the present invention.

Example 1:

The present embodiment will be described below with reference to FIG. 1. The 1907 nm single-mode polarization-maintaining all-fiber laser described in this embodiment includes: a fiber oscillator and a fiber amplifier;

The fiber oscillator includes a high reflectivity fiber Bragg grating 1, a first forward pump optical combiner 3-I, a first pump light source 5-I, and a first low-doped single-mode thulium-doped gain fiber 4-I and low reflectivity fiber Bragg grating 2;

The fiber amplifier includes a first cladding pump optical stripper 6-I, a second cladding pump optical stripper 6-II, an optical isolator 7, a mode field adapter 8, and a second forward pump optical combiner 3-II, the second low-doped single-mode thulium-doped gain fiber 4-II, and the second pump light source 5-II;

The output end of the high-reflectivity fiber Bragg grating 1 is connected to the input end of the first forward pump optical combiner 3-I, and the first pump light source 5-I is connected to the pump of the first forward pump optical combiner 3-I pump fiber, the output end of the first forward pump optical combiner 3-I is connected to one end of the first low-doped single-mode thulium-doped gain fiber 4-I, and the first low-doped single-mode thulium-doped gain fiber 4-I The other end is connected to the input end of the low reflectivity fiber Bragg grating 2;

The output end of the low reflectivity fiber Bragg grating 2 is connected to the input end of the first cladding pump light stripper 6-1;

The output end of the first cladding pump optical stripper 6-1 is connected to the optical isolator 7, the output pigtail of the optical isolator 7 is connected to the mode field adapter 8, and the output end of the mode field adapter 8 is connected to the second forward pump photosynthesiser. The beamer 3-II, the second pump light source 5-II is connected to the pump fiber of the second forward pump beam combiner 3-II, and the signal light output pigtail of the second forward pump beam combiner 3-II One end of the second low-doped single-mode thulium-doped gain fiber 4-II is connected, and the other end of the second low-doped single-mode thulium-doped gain fiber 4-II is connected to the output of the second cladding pump light stripper 6-II end; output linearly polarized light on the slow axis of the optical isolator 7 pigtail;

All devices are polarization maintaining devices.

Further, the high reflectivity fiber Bragg grating 1, the low reflectivity fiber Bragg grating 2, the first low-doped single-mode thulium-doped gain fiber 4-I and the second low-doped single-mode thulium-doped gain fiber 4-II respectively fixed on the heat dissipation base.

Still further, the high-reflection fiber Bragg grating 1 and the low-reflectivity fiber Bragg grating 2 are respectively fixed on different cooling platforms, and the cooling platforms are cooled by semiconductor refrigerators, and the temperature control range is -5 to 40°C. .

Still further, the other end of the first low-doped single-mode thulium-doped gain fiber 4-1 is orthogonally spliced with the input end of the low-reflection fiber Bragg grating 2;

The output end of the low-reflection fiber Bragg grating 2 is orthogonally welded with the input end of the first cladding pump light stripper 6-1;

Horizontal welding is performed between other devices.

In this embodiment, the slow axis of the first low-doped single-mode thulium-doped gain fiber 4-I is spliced with the fast axis of the pigtail fiber of the low-reflection fiber Bragg grating 2.

In this embodiment, the slow axis of the low-reflection fiber Bragg grating 2 pigtail is fused with the fast axis of the first cladding pumping light stripper 6-I.

In this embodiment, horizontal welding is performed between other devices, that is, the slow axis of each pigtail corresponds to the slow axis, and the fast axis corresponds to the fast axis.

Example 2:

The present embodiment will be described below with reference to FIG. 1. The 1907 nm single-mode polarization-maintaining all-fiber laser described in this embodiment includes: a fiber oscillator and a fiber amplifier;

The fiber oscillator includes a high reflectivity fiber Bragg grating 1, a first forward pump optical combiner 3-I, a first pump light source 5-I, and a first low-doped single-mode thulium-doped gain fiber 4-I and low reflectivity fiber Bragg grating 2;

The fiber amplifier includes a first cladding pump optical stripper 6-I, a second cladding pump optical stripper 6-II, an optical isolator 7, a mode field adapter 8, and a second forward pump optical combiner 3-II, the second low-doped single-mode thulium-doped gain fiber 4-II, and the second pump light source 5-II;

The output end of the high-reflectivity fiber Bragg grating 1 is connected to the input end of the first forward pump optical combiner 3-I, and the first pump light source 5-I is connected to the pump of the first forward pump optical combiner 3-I pump fiber, the output end of the first forward pump optical combiner 3-I is connected to one end of the first low-doped single-mode thulium-doped gain fiber 4-I, and the first low-doped single-mode thulium-doped gain fiber 4-I The other end is connected to the input end of the low reflectivity fiber Bragg grating 2;

The output end of the low reflectivity fiber Bragg grating 2 is connected to the input end of the first cladding pump light stripper 6-1;

The output end of the first cladding pump optical stripper 6-1 is connected to the optical isolator 7, the output pigtail of the optical isolator 7 is connected to the mode field adapter 8, and the output end of the mode field adapter 8 is connected to the second forward pump photosynthesiser. The beamer 3-II, the second pump light source 5-II is connected to the pump fiber of the second forward pump beam combiner 3-II, and the signal light output pigtail of the second forward pump beam combiner 3-II One end of the second low-doped single-mode thulium-doped gain fiber 4-II is connected, and the other end of the second low-doped single-mode thulium-doped gain fiber 4-II is connected to the output of the second cladding pump light stripper 6-II end; output linearly polarized light on the slow axis of the optical isolator 7 pigtail;

All devices are polarization maintaining devices.

Further, the fast-axis Bragg wavelength of the high-reflection fiber Bragg grating 1 is 1907nm±0.2nm, the reflectivity is >99.5%, the transmission bandwidth is 0.5nm±0.1nm, and the pump power is higher than 200W;

The slow-axis Bragg wavelength of the low-reflection fiber Bragg grating 2 is 1907nm±0.2nm, the reflectance=10±2%, the reflection bandwidth is 0.3nm±0.1nm, and the maximum signal optical power that can be tolerated is 50W;

The spectral side mode suppression ratio is >20dB, and the Bragg wavelength mismatch between the fast axis and the slow axis is <0.1nm.

Still further, the first forward pump optical beam combiner 3-I is a (6+1)×1 beam combiner, the pumping efficiency is >95%, the signal light transmission loss is <0.7dB, and the signal fiber of the beam combiner is The core diameter and cladding diameter are 10/130 μm, and the pump fiber is 105/125 μm;

The second forward pumping optical beam combiner 3-II is a (6+1)×1 beam combiner, with pumping efficiency>95%, signal light transmission loss<2dB, polarization extinction ratio>18dB, single arm withstand power >150W, the signal fiber is 15/250μm, and the pump fiber is 200/220μm.

Still further, the core/cladding of the first low-doped single-mode thulium-doped gain fiber 4-I is 10/130 μm, the numerical apertures of the core and the cladding are 0.14 and 0.46, respectively, and the cladding is suitable for the 793 nm pump. The absorption coefficient of Puguang is 4.5-4.7dB/m, and the length is 1.8m;

The core/cladding of the second low-doped single-mode thulium-doped gain fiber 4-II is 15/250 μm, the numerical apertures of the core and the cladding are 0.11 and 0.46 respectively, and the absorption of the 793 nm pump light by the cladding is The coefficient is 2.0-2.1dB/m, and the length is 3.0m.

Still further, the core/cladding of the first cladding pump light stripper 6-I is 10/130 μm, the transmission loss of the signal light is <0.2dB, the pump light stripping efficiency is>22dB, and the polarization extinction ratio> 20dB;

The core/cladding of the second cladding pump light stripper 6-II is 15/250 μm, the transmission loss of signal light is less than 0.2 dB, the pump light stripping efficiency is more than 20 dB, and the polarization extinction ratio is more than 18 dB.

Still further, the polarization isolation degree of the optical isolator 7 is >20 dB, the single arm withstand power is 20 W, the core/cladding of the signal fiber is 10/130 μm, and the slow axis of the pigtail fiber outputs linearly polarized light.

Still further, the extinction ratio of the mode field adapter 8 is >16dB, the doping loss is <0.9dB, the core/cladding of the pigtail at the input end is 10/130 μm, and the output end is 15/250 μm.

Describe the working principle of the present invention below in conjunction with Fig. 1:

According to the single-mode fiber mode field diameter formula:

From the above formula, it can be obtained that there is a monotonically decreasing relationship between the mode field diameter and core diameter ratio (MFD/D) and the normalized frequency V value. In order to obtain single-mode laser output, it is first necessary to ensure that the core V value is less than 2.4048, and the MFD/D value at this time can be calculated to be 1.099, which is the optimal mode matching that can be achieved in the single-mode fiber category.

Taking a common large mode field area thulium-doped fiber as an example, the typical value of its core NA is 0.09. Therefore, the maximum core diameter to ensure single-mode transmission of 1900 nm laser is about 16.2 μm. Considering that the signal light transmitted by the laser is linearly polarized light, if the MFD/D is too large, most of the signal light will be transmitted in the cladding, reducing its polarization extinction ratio. Therefore, the MFD/D and polarization extinction ratio should be comprehensively considered for the core diameter of the customized single-mode fiber. in two ways.

In order to obtain higher laser efficiency, the fiber core needs a fine composition design to obtain higher doping concentration and reduce NA, but low NA and high doping concentration are contradictory, and efficient thulium-doped fiber composition design is about large mode field area while ensuring The design requirement of low NA is a long-standing technical difficulty in the manufacture of thulium-doped fibers. This is the design difficulty of highly doped fibers and one of the main reasons that limit the efficiency of current thulium-doped fiber lasers to be much lower than the theoretical quantum efficiency. In order to improve the pump absorption efficiency and the light-light conversion efficiency, the doping concentration and the core-to-package diameter ratio can be appropriately increased, but too high doping concentration makes the fabrication of low-core NA fibers more difficult and photon darkening occurs. , degenerates the fiber efficiency, and considers that the core NA is too small, when the fiber laser is integrated, it is not conducive to the transmission of the cladding pump light in the fiber core, which affects the absorption efficiency of the pump. If the NA is designed to be 0.096, the design value of the maximum single-mode fiber core diameter to ensure the single-mode transmission of light energy with a wavelength greater than 1.9 μm is 15.1 μm. Therefore, we designed the fiber parameters in this research scheme as follows: core NA = 0.08, core diameter 15 μm, cladding NA = 0.48, inner cladding diameter 250 μm, mode field diameter MFD = 16.4 μm, and V value is about 2.0. Considering the thermal management, ASE suppression and efficiency issues in the gain fiber region, the absorption coefficient of the gain fiber cladding is designed to be 2.00dB/m@793nm.

When injecting 793nm pump light power of 475W, the present invention achieves a continuous laser output of 207.6W, the laser center wavelength is 1907.8nm, the light-to-optical conversion efficiency is 43.7%, the polarization extinction ratio is 16.6dB, and the beam quality is 1.52.

The following describes the principle of dual FBG polarization selection in conjunction with Figure 2 and Figure 3:

Writing FBG in the core region of PM fiber is equivalent to writing FBG with the same grating period along the fast and slow main axes. The inherent high birefringence of PM fiber makes the Bragg wavelengths λ _F and λ _S of the fast and slow main axes slightly different , there is a small Bragg wavelength shift Δλ _B , and Δλ _B =2BΛ, where B is the mode birefringence of the polarization-maintaining fiber, B=Δn= _ns -n _f , _ns and n _f are the slow axis and fast axis, respectively Modal index of refraction for the on-axis polarization state, B, on the order of ^10-4 , dimensionless. The magnitude of Λ is 10 ² nm, and the typical distribution range of Δλ _B is 0.1-0.6 nm. Since the two wavelengths appear on the fast and slow axes respectively, the wavelengths exhibit polarization-dependent properties.

In the dual PM-FBG linear cavity fiber CW laser, if the dual PM-FBG is fused at 0°, as shown in Figure 2, ignoring the errors introduced in the manufacturing process, λ ^F _B-HR =λ ^F _B-LR , λ ^S _B-HR =λ ^S _B-LR , according to the wavelength selection of the dual FBG, a pair of dual wavelength characteristic spectra with the same intensity and wavelength interval Δλ _B will appear. The short wavelength corresponds to the fast axis of the dual PM-FBG, and the long wavelength corresponds to the dual PM. - The slow axis of the FBG, the output laser is elliptically polarized light, even if the double FBGs are located at different positions in the cavity, the power of the pumped light is different, and the nonlinear magnitude of the two is different, but because the intensity of the two wavelengths is similar, the two wavelengths are basically Simultaneously, the dual wavelengths can be separated by a polarizing beam splitter.

If the double PM-FBGs are fused at 90°, as shown in Figure 3, the slow axis λ ^S _B-HR of HR-FBG and LR-FBG can be ensured by finely designing the Bragg wavelength and bandwidth of the fast and slow main axes or by applying temperature control to the FBG. The fast axis λ ^F _B-LR corresponds to the fast axis λ ^F _B-HR of HR-FBG and the oscillation of LR-FBG slow axis λ ^S _B-LR can be suppressed at the same time, and the final one is in HR-FBG slow axis and LR - Linearly polarized light output oscillating between the fast axes of the FBG.

Below in conjunction with Fig. 4, Fig. 5, Fig. 6 and Fig. 7, the output parameter of the present invention is described:

4 shows the output power curve of the seed source oscillator in the present invention, the abscissa represents the pump power of the semiconductor laser injected into the beam combiner, and the ordinate represents the output power of the 1907 nm single-mode polarization-maintaining all-fiber oscillator. When the pump light power injected at 793nm is 33.7W, the output power of the oscillator is 12.5W, the slope efficiency is 41.1%, the laser wavelength at this time is 1907.78nm, and the polarization extinction ratio after ISO is 19.6dB.

Figure 5 is the output curve of the 1907nm single-mode polarization-maintaining all-fiber amplifier, the abscissa represents the pump power absorbed by the amplifier stage, and the ordinate represents the output power of the amplifier. When the power of the injected 793nm pump light is 475W, the present invention realizes the continuous laser output of 207.6W, and the slope efficiency is 43.4%.

Fig. 6 shows the laser wavelength of the amplifier, the abscissa shows the wavelength, and the ordinate shows the dimensionless spectral intensity. The central wavelength of the amplifier is the same as that of the oscillator, stable at 1907.8nm, the full width at half-wave of the spectrum is 0.19nm, and the polarization extinction ratio at the highest power is 16.6dB.

Figure 7 shows the beam quality and spot distribution under the highest power of the amplifier. The abscissa indicates the position of the laser transmission direction, and the ordinate indicates the radius of the spot. The beam quality is measured by the knife edge method. The fitting curve can be used to obtain the x-direction of the amplifier at the highest power. The beam quality is 1.52 and the beam quality in the y direction is 1.50.

Although the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and other arrangements can be devised without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the features described in the various dependent claims and herein may be combined in different ways than are described in the original claims. It will also be appreciated that features described in connection with a single embodiment may be used in other described embodiments.

Claims (10)

1. a 1907nm single-mode polarization-maintaining all-fiber laser, is characterized in that, it comprises: fiber oscillator and fiber amplifier; The optical fiber oscillator comprises a high reflectivity fiber Bragg grating (1), a first forward pump optical beam combiner (3-I), a first pump light source (5-I), a first low-doped single-mode dopant Thulium gain fiber (4-I) and low reflectivity fiber Bragg grating (2); The optical fiber amplifier comprises a first cladding pump optical stripper (6-I), a second cladding pump optical stripper (6-II), an optical isolator (7), a mode field adapter (8), a Two forward pump beam combiners (3-II), a second low-doped single-mode thulium-doped gain fiber (4-II), and a second pump light source (5-II); The output end of the high reflectivity fiber Bragg grating (1) is connected to the input end of the first forward pump light combiner (3-I), and the first pump light source (5-I) is connected to the first forward pump light combiner The pump fiber of the device (3-I), the output end of the first forward pump optical combiner (3-I) is connected to one end of the first low-doped single-mode thulium-doped gain fiber (4-I), the first The other end of the low-doped single-mode thulium-doped gain fiber (4-I) is connected to the input end of the low-reflection fiber Bragg grating (2); The output end of the low reflectivity fiber Bragg grating (2) is connected to the input end of the first cladding pump light stripper (6-I); The output end of the first cladding pump optical stripper (6-I) is connected to the optical isolator (7), the output pigtail of the optical isolator (7) is connected to the mode field adapter (8), and the mode field adapter (8) is connected to the output end of the optical isolator (7). The output end is connected to the second forward pump optical combiner (3-II), the second pump light source (5-II) is connected to the pump fiber of the second forward pump optical combiner (3-II), the second The signal light output pigtail of the forward pump optical combiner (3-II) is connected to one end of the second low-doped single-mode thulium-doped gain fiber (4-II), and the second low-doped single-mode thulium-doped gain fiber ( The other end of 4-II) is connected to the output end of the second cladding pumping optical stripper (6-II); linearly polarized light is output on the slow axis of the optical isolator (7) pigtail; All devices are polarization maintaining devices. 2. The 1907nm single-mode polarization-maintaining all-fiber laser according to claim 1, wherein the high-reflection fiber Bragg grating (1), the low-reflection fiber Bragg grating (2), the first low-doped fiber Bragg grating ( The doped single-mode thulium-doped gain fiber (4-I) and the second low-doped single-mode thulium-doped gain fiber (4-II) are respectively fixed on the heat dissipation base. 3. The 1907nm single-mode polarization-maintaining all-fiber laser according to claim 1, wherein the high-reflectivity fiber Bragg grating (1) and the low-reflectivity fiber Bragg grating (2) are respectively fixed and arranged in different positions. On the cooling platform, the cooling platform is cooled by semiconductor refrigerators, and the temperature control range is -5 ~ 40 °C. 4. The 1907nm single-mode polarization-maintaining all-fiber laser according to claim 1, wherein the other end of the first low-doped single-mode thulium-doped gain fiber (4-1) and the low-reflection fiber The input end of the Bragg grating (2) is orthogonally welded; The output end of the low-reflection fiber Bragg grating (2) is orthogonally spliced with the input end of the first cladding pumping light stripper (6-I); Horizontal welding is performed between other devices. 5. The 1907nm single-mode polarization-maintaining all-fiber laser according to claim 1, wherein the fast-axis Bragg wavelength of the high-reflection fiber Bragg grating (1) is 1907nm±0.2nm, and the reflectivity is >99.5 %, the transmission bandwidth is 0.5nm±0.1nm, and the pump power can withstand higher than 200W; The slow-axis Bragg wavelength of the low-reflectivity fiber Bragg grating (2) is 1907nm±0.2nm, the reflectivity=10±2%, the reflection bandwidth is 0.3nm±0.1nm, and the maximum signal optical power that can be tolerated is 50W; The spectral side mode suppression ratio is >20dB, and the Bragg wavelength mismatch between the fast axis and the slow axis is <0.1nm. 6. The 1907nm single-mode polarization-maintaining all-fiber laser according to claim 1, wherein the first forward pump beam combiner (3-1) is a (6+1)×1 beam combiner The pump efficiency is >95%, the signal light transmission loss is <0.7dB, the core diameter and cladding diameter of the signal fiber of the combiner are 10/130μm, and the pump fiber is 105/125μm; The second forward pump optical beam combiner (3-II) is a (6+1)×1 beam combiner, with pumping efficiency >95%, signal light transmission loss <2dB, polarization extinction ratio >18dB, single arm Withstand power>150W, signal fiber is 15/250μm, pump fiber is 200/220μm. 7. The 1907nm single-mode polarization-maintaining all-fiber laser according to claim 1, wherein the core/cladding of the first low-doped single-mode thulium-doped gain fiber (4-1) is 10 /130μm, the numerical apertures of the core and the cladding are 0.14 and 0.46, respectively, the absorption coefficient of the cladding to the 793nm pump light is 4.5-4.7dB/m, and the length is 1.8m; The core/cladding of the second low-doped single-mode thulium-doped gain fiber (4-II) is 15/250 μm, the numerical apertures of the core and the cladding are 0.11 and 0.46, respectively, and the cladding corresponds to the 793 nm pump light The absorption coefficient is 2.0-2.1dB/m, and the length is 3.0m. 8. The 1907nm single-mode polarization-maintaining all-fiber laser according to claim 1, wherein the core/cladding of the first cladding pump light stripper (6-I) is 10/130 μm , the transmission loss of signal light is <0.2dB, the stripping efficiency of pump light is >22dB, and the polarization extinction ratio is >20dB; The core/cladding of the second cladding pump light stripper (6-II) is 15/250 μm, the transmission loss of the signal light is less than 0.2 dB, the pump light stripping efficiency is more than 20 dB, and the polarization extinction ratio is more than 18 dB. 9. The 1907nm single-mode polarization-maintaining all-fiber laser according to claim 1, wherein the polarization isolation of the optical isolator (7) is >20dB, the single-arm withstand power is 20W, and the core of the signal fiber /The cladding is 10/130 μm, and linearly polarized light is output on the slow axis of the pigtail. 10. A 1907nm single-mode polarization-maintaining all-fiber laser according to claim 1, characterized in that, the extinction ratio of the mode field adapter (8) is >16dB, the doping loss is <0.9dB, and the input end pigtail has an extinction ratio >16dB. The core/cladding is 10/130 μm and the output is 15/250 μm.

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