High-concentration ytterbium-doped double-clad silicate optical fiber single-frequency amplifier

Abstract

The invention provides a high-concentration ytterbium-doped double-clad silicate optical fiber single-frequency amplifier which comprises a single-frequency laser seed source, a double-clad optical fiber pre-amplifier and a high-concentration ytterbium-doped double-clad silicate optical fiber main amplifier which are connected in sequence. The single-mode optical fiber pre-amplifier is used for primarily amplifying the single-frequency laser; the double-clad optical fiber pre-amplifier is used for further amplifying the optical signal output from the single-mode pre-amplifier; and the high-concentration ytterbium-doped double-clad silicate optical fiber main amplifier is used for performing high-power amplification on the signal light amplified by the double-clad optical fiber pre-amplifier and outputting specific high-power narrow-linewidth single-frequency laser. Single-frequency laser seed source low-noise coefficient pre-amplification is achieved through a front multi-stage pre-amplification system, a high-concentration ytterbium-doped double-clad silicate optical fiber is adopted in a final main amplifier, the length of a needed active optical fiber is shortened through provided high gain, the stimulated Brillouin scattering effect is restrained, and the optical fiber is high in gain and high in power consumption. And the output power of the single-frequency narrow-linewidth optical fiber amplifier is improved.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber lasers, and in particular to a high-concentration ytterbium-doped double-clad silicate optical fiber single-frequency amplifier. Background Art

[0002] Single-frequency lasers are a type of light source that operates in a single longitudinal mode of an optical oscillator. Due to their advantages such as long coherence length, low noise, and narrow spectrum width, they have been widely used in high-precision optical sensing, coherent communications, metrology, and other fields.

[0003] Single-frequency lasers are usually produced by operating in a laser cavity with a wide mode spacing and using filtering elements within the cavity to select a single oscillation mode. This can usually be achieved with a short cavity and a narrowband filter.

[0004] However, with the development of technology, in some high-end applications such as gravitational wave detection, coherent lidar, nonlinear frequency conversion, etc., the power level of a single-frequency laser source directly output by a single oscillator is difficult to meet the application requirements. In order to increase the power of a single-frequency laser, rare earth ion-doped optical fiber is used as a gain medium due to its excellent heat dissipation performance, high conversion efficiency and flexible operability.

[0005] Nevertheless, the maximum output power of single-frequency fiber amplifiers is still limited by the nonlinear effect - stimulated Brillouin scattering (SBS), that is, the laser signal is backscattered by the acoustic waves induced by the electroconstriction process in the optical fiber, thereby generating Stokes light with a frequency downshift equal to the corresponding phonon frequency, which limits the achievable output power and reduces the stability of the laser. For single-frequency fiber amplifiers, due to their ultra-narrow spectral line width, the threshold of the SBS effect is greatly reduced, further limiting the achievable output power.

[0006] The most direct way to suppress the stimulated Brillouin scattering effect in related technologies is to increase the effective mode area of ​​the main amplifier and shorten the fiber length. In order to increase the working power of a single-frequency fiber amplifier, a large-mode-field fiber with a larger core diameter can be used, but increasing the core diameter will lead to a decrease in beam quality, and an excessively large mode field diameter will also reduce the transverse mode instability threshold, which will also limit the power increase.

[0007] In addition, due to the limitation of rare earth ion doping concentration, the active silica fiber in conventional amplifier system requires a relatively long gain fiber length to provide sufficient gain, which leads to a lower stimulated Brillouin scattering threshold and limits the power increase of single-frequency laser. Summary of the invention

[0008] The invention provides a high-concentration ytterbium-doped double-clad silicate optical fiber single-frequency amplifier, which solves the problem of how to increase the stimulated Brillouin scattering threshold and the power of the single-frequency amplifier.

[0009] In order to achieve the above purpose, this application adopts the following technical solutions:

[0010] Provided is a high concentration ytterbium-doped double-clad silicate fiber single-frequency amplifier, comprising:

[0011] A single-frequency laser seed source, wherein the output end of the single-frequency laser seed source is connected to a single-mode optical fiber pre-amplifier, and the single-mode optical fiber pre-amplifier is used to preliminarily amplify the single-frequency laser provided by the single-frequency laser seed source;

[0012] The output end of the single-mode optical fiber preamplifier is connected to a double-clad optical fiber preamplifier, and the double-clad optical fiber preamplifier is used to further amplify the optical signal output from the single-mode preamplifier;

[0013] The output end of the double-clad fiber preamplifier is connected to a high-concentration ytterbium-doped double-clad silicate fiber main amplifier, which is used to perform final high-power amplification on the signal light amplified by the double-clad fiber preamplifier and output a specific high-power narrow-linewidth single-frequency laser.

[0014] In a first possible implementation, the single-mode optical fiber preamplifier includes a pump source, a wavelength division multiplexer, a single-mode active optical fiber and a first isolator;

[0015] The pump light is combined with the single-frequency laser output by the single-frequency laser seed source through the wavelength division multiplexer, and then injected into the single-mode active optical fiber. After amplification, the first-stage pre-amplified light is output, and the first-stage pre-amplified light is output to the double-clad optical fiber pre-amplifier through the first isolator.

[0016] Based on the first possible implementation manner, in a second possible implementation manner, the pump source is a single-mode pump source, which provides single-mode pump light for the optical fiber pre-amplifier.

[0017] Based on the first possible implementation, in a third possible implementation, the double-clad fiber preamplifier includes a first multimode pump source, a first pump / signal combiner, a double-clad active optical fiber, and a second isolator;

[0018] The pump end of the first pump / signal combiner is connected to the first multi-mode pump source, the first-stage pre-amplified light and the pump light of the first multi-mode pump source are combined by the first pump / signal combiner, injected into the double-clad active optical fiber for amplification, and the amplified second-stage pre-amplified light is output, and then output through the second isolator.

[0019] Based on the third possible implementation manner, in a fourth possible implementation manner, the single-mode active optical fiber is an ytterbium-doped single-mode active optical fiber, and its gain is lower than that of the double-clad active optical fiber.

[0020] Based on the fourth possible implementation, in a fifth possible implementation,

[0021] Based on the third possible implementation, in a fifth possible implementation, the high-concentration ytterbium-doped double-clad silicate fiber main amplifier includes a plurality of second multimode pump sources, a second pump / signal combiner, and a high-concentration ytterbium-doped double-clad silicate fiber;

[0022] The pump end of the second pump / signal combiner is connected in parallel to a plurality of the second multi-mode pump sources, and the secondary pre-amplified light and the pump light of the plurality of the second multi-mode pump sources are combined by the second pump / signal combiner, injected into the high-concentration ytterbium-doped double-clad silicate optical fiber for amplification and then output as a specific high-power narrow-linewidth single-frequency laser.

[0023] Based on the fifth possible implementation, in a sixth possible implementation, the high-concentration ytterbium-doped double-clad silicate optical fiber is a silicate optical fiber, and the ytterbium ion doping concentration is higher than 8000 ppm.

[0024] Based on any of the above possible implementations, in a seventh possible implementation, the double-clad active optical fiber is an ytterbium-doped double-clad active optical fiber; the gain of the double-clad active optical fiber is lower than the gain of a high-concentration ytterbium-doped double-clad silicate optical fiber.

[0025] Based on any of the above possible implementations, in an eighth possible implementation, a stimulated Brillouin scattering backlight monitoring system is provided between the double-clad fiber preamplifier and the high-concentration ytterbium-doped double-clad silicate fiber main amplifier; the stimulated Brillouin scattering backlight monitoring system is used to monitor the stimulated Brillouin scattering backlight to prevent the backlight power from being too high and affecting the system laser system;

[0026] The stimulated Brillouin scattering backlight monitoring system realizes monitoring through a reverse-connected optical fiber beam splitter, with a splitting ratio of 0.1:99.9, a high-power terminal signal light, and a low-power light connected to a backlight monitoring power meter or a spectrometer.

[0027] Based on any of the foregoing possible implementations, in a ninth possible implementation, the filter, the end cap, and the active optical fiber are connected via passive double-clad optical fibers of the same size.

[0028] The present application realizes low noise coefficient pre-amplification of a single-frequency laser seed source by reasonably setting up a pre-stage multi-stage pre-amplification system, provides a high-quality light beam, and adopts a high-concentration ytterbium-doped double-clad silicate fiber in the final main amplifier. The high gain provided shortens the length of the required active fiber and suppresses the stimulated Brillouin scattering effect, so as to improve the output power of the single-frequency narrow-linewidth fiber amplifier; by introducing a stimulated Brillouin scattering backlight monitoring system, the stimulated Brillouin scattering backlight of the system can be monitored in real time when the laser is running, thereby improving the safety of the high-power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram of the structure of a high-concentration ytterbium-doped double-clad silicate fiber single-frequency amplifier provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of the structure of another single-mode optical fiber pre-amplifier provided in an embodiment of the present application;

[0031] Figure 3 A schematic diagram of the structure of a double-clad optical fiber pre-amplifier provided in an embodiment of the present application;

[0032] Figure 4 A schematic diagram of the structure of a high-concentration ytterbium-doped double-clad silicate fiber main amplifier provided in an embodiment of the present application.

[0033] Reference numerals:

[0034] Single-frequency laser seed source 1; single-mode fiber preamplifier 2; pump source 201, wavelength division multiplexer 202, single-mode active fiber 203; first isolator 204; double-clad fiber preamplifier 3; first multi-mode pump source 301; first pump / signal combiner 302; double-clad active fiber 303; second isolator 304; stimulated Brillouin scattering backlight monitoring system 4; high-concentration ytterbium-doped double-clad silicate fiber main amplifier 5; second multi-mode pump source 501; second pump / signal combiner 502; high-concentration ytterbium-doped double-clad silicate fiber 503. DETAILED DESCRIPTION

[0035] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose, the technical solutions in the embodiments of the present application are clearly described. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present application.

[0036] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the terms used in this way are interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of one type, and the number of objects is not limited. For example, the first object can be one or more. In addition, "and / or" in the specification and claims represents at least one of the connected objects, and the character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0037] The description of the method flow in the specification of the present application and the steps of the flowchart in the drawings of the present specification do not have to be strictly executed according to the step numbers, and the method steps can be executed in a different order. Moreover, some steps can be omitted, multiple steps can be combined into one step, and / or one step can be decomposed into multiple steps.

[0038] The high-concentration ytterbium-doped double-clad silicate fiber single-frequency amplifier provided in the embodiments of the present application is described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0039] First, the application scenario of the high-concentration ytterbium-doped double-clad silicate fiber single-frequency amplifier in the embodiment of the present application is described in detail.

[0040] For applications such as gravitational wave detection, coherent lidar, and nonlinear frequency conversion, the power level of a single-frequency laser source directly output by a single oscillator is far from meeting the application requirements. Taking the Einstein telescope as an example, in order to reduce signal shot noise and improve the sensitivity of gravitational wave detection, a kilowatt-level single-frequency laser power was designed. For the amplification of single-frequency lasers, rare earth ion-doped optical fibers are the first choice as gain media due to their unique waveguide structure, large heat dissipation specific surface area, excellent thermal optical performance, high conversion efficiency, and flexible operation.

[0041] Using amplifier solutions based on large mode field fibers, the output power of wide spectrum lasers with nearly diffraction-limited single-mode beams reached the 10,000-watt level more than a decade ago. However, the maximum output power of single-frequency fiber amplifiers still does not exceed 1 kilowatts, and the main limiting factor is the nonlinear stimulated Brillouin scattering effect. For single-frequency fiber amplifiers, the ultra-narrow linewidth greatly reduces the threshold of stimulated Brillouin scattering effect, so an important factor in improving the power of single-frequency fiber amplifiers is to suppress the stimulated Brillouin scattering effect.

[0042] The most direct way to suppress the stimulated Brillouin scattering effect is to increase the effective mode area of ​​the main amplifier and shorten the fiber length. In order to increase the working power of the single-frequency fiber amplifier, a large-mode-field fiber with a larger core diameter can be used, but the larger core diameter deteriorates the beam quality, so it is necessary to maintain an ultra-low numerical aperture of the fiber. However, the numerical aperture cannot be reduced infinitely. Too low numerical aperture weakens the binding ability of the fiber core, resulting in a smaller bending range of the fiber, and also has extremely high requirements for the preparation process. On the other hand, too large a mode field diameter will also reduce the threshold of transverse mode instability, which will also limit the power increase. Limited by the doping concentration of rare earth ions, the active quartz fiber in the conventional amplifier system requires a relatively long gain fiber length to provide sufficient gain, resulting in a lower stimulated Brillouin scattering threshold, which limits the power increase of the single-frequency laser. Although the large-mode-field active fiber used in the power amplifier stage can alleviate the constraints of the stimulated Brillouin scattering effect to a certain extent, the low seed source power leads to a significant decrease in the signal-to-noise ratio during laser amplification, and the signal light power is increased by the pre-amplifier stage.

[0043] In order to overcome the above technical problems, this application proposes a single-frequency amplifier design using high-concentration ytterbium-doped double-clad silicate fiber. By optimizing the doping concentration and geometric parameters of the fiber and the system composition, high-power and high-stability single-frequency laser output is achieved.

[0044] See also Figure 1 , the present application embodiment provides a high concentration ytterbium-doped double-clad silicate fiber single-frequency amplifier, such as Figure 1 As shown, the single-frequency amplifier of the embodiment of the present application includes:

[0045] A single-frequency laser seed source 1, the output end of which is connected to a single-mode fiber preamplifier 2, the output end of which is connected to a double-clad fiber preamplifier 3, and the output end of which is connected to a high-concentration ytterbium-doped double-clad silicate fiber main amplifier 5.

[0046] The single-frequency laser seed source 1 is used to provide low-power single-frequency laser. In specific implementation, the single-frequency laser seed source 1 can be connected to an isolator, which is used to prevent the reverse light of the amplifier from affecting the working stability of the single-frequency laser seed source 1.

[0047] The type and line width of the single-frequency laser seed source 1 are selected according to the actual application. The type can be linear polarization-maintaining or non-polarized light, and the line width can be in the kHz and MHz range.

[0048] See also Figure 2The single-mode fiber preamplifier 2 is used to preliminarily amplify the single-frequency laser provided by the single-frequency laser seed source 1. The single-mode fiber preamplifier 2 includes a pump source 201, a wavelength division multiplexer 202, a single-mode active fiber 203 and a first isolator 204. The pump light is combined with the single-frequency laser output by the single-frequency laser seed source 1 through the wavelength division multiplexer 202, and then injected into the single-mode active fiber 203. After amplification, the first-stage pre-amplified light is output, and the first-stage pre-amplified light is output to the next-stage double-clad fiber preamplifier 3 through the first isolator 204. In some possible implementations, the wavelength division multiplexer 202 can be replaced by a combiner to achieve the same technical effect. Each port of the wavelength division multiplexer 202 or the combiner should correspond to the size of the optical fiber in the front and rear optical paths.

[0049] Furthermore, the pump source 201 is a single-mode pump source, which provides single-mode pump light for the optical fiber pre-amplifier 2 .

[0050] See also Figure 3 The double-clad fiber preamplifier 3 is used to further amplify the optical signal output from the single-mode preamplifier, that is, the first-stage pre-amplified light. The double-clad fiber preamplifier 3 includes a first multimode pump source 301, a first pump / signal combiner 302, a double-clad active fiber 303, and a second isolator 304. The pump end of the first pump / signal combiner 302 is connected to the first multimode pump source 301. The first-stage pre-amplified light and the pump light of the first multimode pump source 301 are combined by the first pump / signal combiner 302, injected into the double-clad active fiber 303 for amplification, and the amplified second-stage pre-amplified light is output, and then output to the next stage through the second isolator 304.

[0051] Further, the single-mode active fiber 203 is an ytterbium-doped single-mode active fiber, and its gain is lower than that of the double-clad active fiber 303. In specific implementation, preferably, the core / cladding size of the single-mode active fiber 203 can be 6 / 125 μm, 8 / 125 μm, 10 / 125 μm, etc.

[0052] See also Figure 4 The high-concentration ytterbium-doped double-clad silicate fiber main amplifier 5 performs final high-power amplification on the pre-amplified signal light, that is, amplifies the secondary pre-amplified light. The high-concentration ytterbium-doped double-clad silicate fiber main amplifier 5 includes a plurality of second multi-mode pump sources 501, a second pump / signal combiner 502, and a high-concentration ytterbium-doped double-clad silicate fiber 503. The pump end of the second pump / signal combiner 502 is connected in parallel to the plurality of second multi-mode pump sources 501, and the secondary pre-amplified light and the pump light of the plurality of second multi-mode pump sources 501 are combined by the second pump / signal combiner 502, injected into the high-concentration ytterbium-doped double-clad silicate fiber 503 for amplification and then output as a specific high-power narrow-linewidth single-frequency laser.

[0053] In specific implementation, the number of the second multimode pump sources 501 can be determined according to demand, and accordingly, the specifications of the second pump / signal combiner 502 are adjusted according to the number and size of the pump sources. The output end of the high-concentration ytterbium-doped double-clad silicate fiber main amplifier 5 is connected to a filter and an end cap, and the high-concentration ytterbium-doped double-clad silicate fiber main amplifier 5 outputs the amplified laser, which is filtered by the filter and then outputted through the end cap.

[0054] Furthermore, the high-concentration ytterbium-doped double-clad silicate optical fiber 503 is a silicate optical fiber, which uses silicate glass as a matrix material, and introduces other elements such as aluminum, boron, and phosphorus into it. Through a multi-component coordination mechanism, the ytterbium ion concentration of the active optical fiber is increased to 2% to 5%. Traditional quartz active optical fiber, whose main component is silicon dioxide, has a limited rare earth ion doping concentration, and an active optical fiber with high gain cannot be formed at a very high doping concentration. For ytterbium ions, the concentration of commercial conventional double-clad ytterbium-doped optical fiber is about 0.5% to 0.8%. The present application significantly increases the upper limit of the doping concentration of ytterbium ions in the optical fiber, and has a higher gain per unit length, so the length of the active optical fiber can be greatly reduced under the same gain required by the system.

[0055] Specifically, the ytterbium ion doping concentration of the high-concentration ytterbium-doped double-clad silicate optical fiber 503 is higher than 8000 ppm, and the selected length can be 10 cm, 30 cm, 50 cm, 80 cm, 100 cm, etc. according to the gain and power requirements.

[0056] Furthermore, the double-clad active optical fiber 303 is an ytterbium-doped double-clad active optical fiber, and its gain is higher than that of the single-mode active optical fiber 203 , but lower than that of the high-concentration ytterbium-doped double-clad silicate optical fiber 503 .

[0057] Through the single-mode fiber preamplifier 2, double-clad fiber preamplifier 3 and high-concentration ytterbium-doped double-clad silicate fiber main amplifier 5 with progressive gain relationships, high-power narrow-linewidth laser output with high beam quality, lower mode noise and high power can be guaranteed.

[0058] In some possible implementations, the filter, the end cap and the active optical fiber are connected through a passive double-clad optical fiber of the same size. On the basis of meeting the function, the length of the passive optical fiber should be shortened as much as possible to reduce the accumulation of nonlinear effects of the laser during transmission and thus affect the output power.

[0059] In some possible implementations, a stimulated Brillouin scattering backlight monitoring system 4 is provided between the double-clad fiber preamplifier 3 and the high-concentration ytterbium-doped double-clad silicate fiber main amplifier 5. The stimulated Brillouin scattering backlight monitoring system 4 is used to monitor the stimulated Brillouin scattering backlight to prevent the backlight power from being too high and affecting the system laser system. The secondary pre-amplified light is injected into the high-concentration ytterbium-doped double-clad silicate fiber main amplifier 5 after passing through the stimulated Brillouin scattering backlight monitoring system 4.

[0060] Furthermore, the stimulated Brillouin scattering backlight monitoring system 4 is monitored by a reverse-connected optical fiber beam splitter, with a splitting ratio of 0.1:99.9, a high-power terminal connected to the signal light, and a low-power light connected to the backlight monitoring power meter or spectrometer. When in use, the monitoring system can detect the occurrence of SBS in real time, and can suppress its influence by adjusting the pump power or taking other measures.

[0061] In some possible implementations, the isolator provides a filtering effect of a narrowband filter in addition to band isolation.

[0062] Exemplarily, the single-frequency laser seed source 1 provides an initial single-frequency laser signal, which is required to have a very narrow line width and relatively low power, such as a single-frequency seed source of 2 kHz and 50 mW.

[0063] The 2kHz, 50mW single-frequency seed source outputs single-frequency light through the isolator, and together with the 300mW pump light of the pump source 201, is injected into the single-mode active optical fiber 203 through a wavelength division multiplexer or a combiner, and outputs a first-stage pre-amplified light after amplification. The core / cladding size of the single-mode active optical fiber 203 used is 10 / 125μm.

[0064] The first-stage pre-amplified light is then output to the next stage through the first isolator 204, and the power output to the next stage is 200 mW.

[0065] The first multimode pump source 301 uses two 9W multimode pumps in parallel input, and the core / inner cladding / outer cladding size of the double-clad active fiber 303 is 10 / 125 / 250μm. The first-stage pre-amplified light is injected into the double-clad active fiber 303 through the pump source and the signal end of the signal combiner for amplification, and the amplified second-stage pre-amplified light is output, and then output to the next stage through the second isolator 304.

[0066] The secondary pre-amplified light is injected into the high-concentration ytterbium-doped double-clad silicate fiber main amplifier 5 after passing through the return light monitoring system, with a power of 14.2W.

[0067] The core / inner cladding / outer cladding dimensions of the high-concentration ytterbium-doped double-clad silicate optical fiber 503 are 30 / 250 / 400 μm, the length is 50 cm, and the gain is 18 dB.

[0068] The amplified laser output from the high-concentration ytterbium-doped double-clad silicate fiber 503 is filtered by a filter and then output from an end cap. The output is a single-frequency narrow-linewidth laser with a linewidth of 3kHz and a power of 300W.

[0069] In summary, the present application realizes low noise coefficient pre-amplification of a single-frequency laser seed source by reasonably setting up a pre-stage multi-stage pre-amplification system, provides a high-quality light beam, and adopts a high-concentration ytterbium-doped double-clad silicate fiber in the final main amplifier. The high gain provided shortens the length of the required active fiber and suppresses the stimulated Brillouin scattering effect to improve the output power of the single-frequency narrow-linewidth fiber amplifier; by introducing a stimulated Brillouin scattering backlight monitoring system, the stimulated Brillouin scattering backlight of the system can be monitored in real time when the laser is running, thereby improving the safety of the high-power system.

[0070] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0071] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present application, ordinary technicians in this field can also make many forms without departing from the purpose of the present application and the scope of protection of the claims, all of which are within the protection of the present application.

Claims

1. A high concentration ytterbium-doped double-clad silicate fiber single-frequency amplifier, characterized in that: include: A single-frequency laser seed source, wherein the output end of the single-frequency laser seed source is connected to a single-mode optical fiber pre-amplifier, and the single-mode optical fiber pre-amplifier is used to preliminarily amplify the single-frequency laser provided by the single-frequency laser seed source; The output end of the single-mode optical fiber preamplifier is connected to a double-clad optical fiber preamplifier, and the double-clad optical fiber preamplifier is used to further amplify the optical signal output from the single-mode preamplifier; The output end of the double-clad fiber preamplifier is connected to a high-concentration ytterbium-doped double-clad silicate fiber main amplifier, which is used to perform final high-power amplification on the signal light amplified by the double-clad fiber preamplifier and output a specific high-power narrow-linewidth single-frequency laser.

2. The high concentration ytterbium doped double clad silicate fiber single frequency amplifier according to claim 1, characterized in that: The single-mode optical fiber pre-amplifier comprises a pump source, a wavelength division multiplexer, a single-mode active optical fiber and a first isolator; The pump light is combined with the single-frequency laser output by the single-frequency laser seed source through the wavelength division multiplexer, and then injected into the single-mode active optical fiber. After amplification, the first-stage pre-amplified light is output, and the first-stage pre-amplified light is output to the double-clad optical fiber pre-amplifier through the first isolator.

3. The high concentration ytterbium doped double clad silicate fiber single frequency amplifier according to claim 2, characterized in that: The pump source is a single-mode pump source, which provides single-mode pump light for the optical fiber pre-amplifier.

4. The high concentration ytterbium doped double clad silicate fiber single frequency amplifier according to claim 2, characterized in that: The double-clad fiber preamplifier comprises a first multimode pump source, a first pump / signal combiner, a double-clad active fiber and a second isolator; The pump end of the first pump / signal combiner is connected to the first multi-mode pump source, the first-stage pre-amplified light and the pump light of the first multi-mode pump source are combined by the first pump / signal combiner, injected into the double-clad active optical fiber for amplification, and the amplified second-stage pre-amplified light is output, and then output through the second isolator.

5. The high concentration ytterbium doped double clad silicate fiber single frequency amplifier according to claim 4, characterized in that: The single-mode active optical fiber is an ytterbium-doped single-mode active optical fiber, and its gain is lower than the gain of the double-clad active optical fiber.

6. The high concentration ytterbium doped double clad silicate fiber single frequency amplifier according to claim 4, characterized in that: The high-concentration ytterbium-doped double-clad silicate fiber main amplifier includes a plurality of second multimode pump sources, a second pump / signal combiner and a high-concentration ytterbium-doped double-clad silicate fiber; The pump end of the second pump / signal combiner is connected in parallel to a plurality of the second multi-mode pump sources, and the secondary pre-amplified light and the pump light of the plurality of the second multi-mode pump sources are combined by the second pump / signal combiner, injected into the high-concentration ytterbium-doped double-clad silicate optical fiber for amplification and then output as a specific high-power narrow-linewidth single-frequency laser.

7. The high concentration ytterbium doped double clad silicate fiber single frequency amplifier according to claim 6, characterized in that: The high-concentration ytterbium-doped double-clad silicate optical fiber is a silicate optical fiber, and the ytterbium ion doping concentration is higher than 8000ppm.

8. The high concentration ytterbium doped double clad silicate fiber single frequency amplifier according to any one of claims 1 to 7, characterized in that: The double-clad active optical fiber is an ytterbium-doped double-clad active optical fiber; the gain of the double-clad active optical fiber is lower than the gain of a high-concentration ytterbium-doped double-clad silicate optical fiber.

9. The high concentration ytterbium doped double clad silicate fiber single frequency amplifier according to any one of claims 1 to 7, characterized in that: A stimulated Brillouin scattering backlight monitoring system is provided between the double-clad optical fiber pre-amplifier and the high-concentration ytterbium-doped double-clad silicate optical fiber main amplifier; the stimulated Brillouin scattering backlight monitoring system is used to monitor the stimulated Brillouin scattering backlight to prevent the backlight power from being too high to affect the system laser system; The stimulated Brillouin scattering backlight monitoring system realizes monitoring through a reverse-connected optical fiber beam splitter, with a splitting ratio of 0.1:99.9, a high-power terminal signal light, and a low-power light connected to a backlight monitoring power meter or a spectrometer.

10. The high concentration ytterbium doped double clad silicate fiber single frequency amplifier according to any one of claims 1 to 7, characterized in that: The filter, the end cap and the active optical fiber are connected through passive double-clad optical fibers of the same size.

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