3 [mu] m high-repetition-frequency high-power femtosecond fiber laser

Abstract

The invention provides a 3 [mu] m high-repetition-frequency high-power femtosecond fiber laser. The 3 [mu] m high-repetition-frequency high-power femtosecond fiber laser comprises an annular cavity structure and an amplification unit, the annular cavity structure comprises a first pumping source, a first erbium-doped gain fiber, a nonlinear polarization rotation unit and a coupler; the first pumping source emits 1.7 [mu] m pumping light to the first erbium-doped gain fiber, the first erbium-doped gain fiber emits 3 [mu] m laser to the nonlinear polarization rotation unit, the nonlinear polarization rotation unit emits 3 [mu] m high repetition frequency mode-locked laser to the coupler, and the coupler inputs part of the 3 [mu] m high repetition frequency mode-locked laser into the amplification unit; the amplification unit improves the average power of the 3 [mu] m high repetition frequency mode-locked laser. According to the invention, the 1.7 [mu] m fiber core pumping technology of excitation state enhanced absorption is adopted to realize high repetition frequency mode-locked pulse output, the advantages of 1.7 [mu] m high absorption rate and high gain realized by using short gain fibers are utilized, the nonlinear effect in the pulse amplification process is weakened, and finally high average power pulse output is realized.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, in particular to a 3μm high repetition rate and high power femtosecond fiber laser. Background Art

[0002] In order to achieve high repetition rate mode-locked pulse output, it is necessary to control the length of the resonant cavity and use the shortest possible active fiber as the gain medium. 3+ :The cladding pumping mode absorption rate of ZBLAN fiber laser is low, and a longer gain fiber is required to obtain sufficient pump absorption to reach the laser threshold, which limits the increase in the repetition frequency of the mode-locked pulse. In addition, the frequency difference between the 976nm pump light and the 3μm signal light is large, the corresponding quantum loss is also large, and the Stokes limit is low, which limits the efficiency of 3μm laser generation. In other words, the current 3μm mid-infrared band femtosecond fiber laser has deficiencies in average power, repetition frequency, etc. and faces development bottlenecks. Summary of the invention

[0003] In order to solve the above problems, an object of the embodiments of the present invention is to provide a 3 μm high repetition rate and high power femtosecond fiber laser.

[0004] The embodiment of the present invention provides a 3μm high repetition rate high power femtosecond fiber laser, comprising: a ring cavity structure and an amplifying unit; the ring cavity structure at least comprises a first pump source, a first erbium-doped gain fiber, a nonlinear polarization rotation unit and a coupler; the first pump source emits 1.7μm pump light to the first erbium-doped gain fiber, the first erbium-doped gain fiber receives the 1.7μm pump light and emits 3μm laser to the nonlinear polarization rotation unit, the nonlinear polarization rotation unit receives the 3μm laser and emits 3μm high repetition rate mode-locked laser to the coupler, the coupler leaves part of the 3μm high repetition rate mode-locked laser in the ring cavity structure for circulation, and inputs another part of the 3μm high repetition rate mode-locked laser into the amplifying unit; the amplifying unit is used to increase the average power of the 3μm high repetition rate mode-locked laser.

[0005] Optionally, the ring cavity structure also includes: a first dichroic mirror arranged between the first pump source and the first erbium-doped gain fiber, the first dichroic mirror being used to transmit the 1.7 μm pump light emitted by the first pump source to the first erbium-doped gain fiber, and to reflect the 3 μm high repetition rate mode-locked laser transmitted by the coupler.

[0006] Optionally, the annular cavity structure further includes: a gold mirror disposed between the first dichroic mirror and the coupler, the gold mirror being used to reflect the 3 μm high repetition rate mode-locked laser transmitted by the coupler to the first dichroic mirror.

[0007] Optionally, the ring cavity structure further includes: a second dichroic mirror disposed between the first erbium-doped gain fiber and the nonlinear polarization rotation unit, the second dichroic mirror being used for reflecting the 3 μm laser emitted by the first erbium-doped gain fiber to the nonlinear polarization rotation unit.

[0008] Optionally, the annular cavity structure further includes: a first wavelength division multiplexer arranged between the first pump source and the first erbium-doped gain fiber.

[0009] Optionally, the nonlinear polarization rotation unit includes: a first half paddle, a first isolator and a first quarter paddle; the first half paddle is used to change the polarization direction of the 3μm laser emitted by the erbium-doped gain fiber, the first isolator is used to ensure that the 3μm laser is transmitted in a single direction, and the first quarter paddle is used to adjust the polarization state of the 3μm laser and output the 3μm high repetition rate mode-locked laser.

[0010] Optionally, the amplification unit at least includes: a second pump source, a second erbium-doped gain fiber and a second isolator; the second pump source emits 1.7 μm pump light to the second erbium-doped gain fiber, the second isolator receives the 3 μm high repetition rate mode-locked laser diverted by the coupler and emits it to the second erbium-doped gain fiber, the second erbium-doped gain fiber receives the 1.7 μm pump light emitted by the second pump source and the 3 μm high repetition rate mode-locked laser emitted by the second isolator, thereby increasing the average power of the 3 μm high repetition rate mode-locked laser.

[0011] Optionally, when the ring cavity structure further includes the first wavelength division multiplexer, the amplification unit further includes: a second wavelength division multiplexer arranged between the second pump source and the second erbium-doped gain fiber.

[0012] Optionally, when the ring cavity structure also includes the first dichroic mirror, the amplification unit also includes: a third dichroic mirror arranged between the second pump source and the second erbium-doped gain fiber; the third dichroic mirror is used to transmit the 1.7μm pump light emitted by the second pump source to the second erbium-doped gain fiber, and reflect the 3μm high repetition rate mode-locked laser emitted by the second isolator to the second erbium-doped gain fiber.

[0013] Optionally, the amplifying unit further includes: a second quarter paddle and a second half paddle which are sequentially arranged on the light exiting side of the second isolator.

[0014] In the solution provided in the embodiment of the present invention, a 1.7 μm fiber core is used to pump Er 3+Doped ZBLAN fiber can achieve high repetition rate mode-locked pulse output. Compared with cladding pumping technology, 1.7μm core pumping technology can greatly improve the conversion efficiency of lasers in active optical fibers, while reducing quantum loss. A shorter gain fiber can achieve higher gain, so the repetition rate of the mode-locked fiber laser can be greatly increased, reducing nonlinear effects and suppressing pulse splitting. Subsequently, this high repetition rate mode-locked fiber laser is used as a seed source and combined with amplification unit 2 again. In the process of amplifying high repetition rate signal light, due to the high repetition rate, the pulse peak power is low at the same average power, avoiding pulse splitting caused by the peak power clamping effect. At the same time, combined with soliton self-compression, it can take into account the requirements of high average power and narrow pulse width, and finally achieve 3μm high repetition rate and high power femtosecond laser stable output.

[0015] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram showing the general structure of a first 3μm high repetition rate high power femtosecond fiber laser provided by an embodiment of the present invention is shown;

[0018] Figure 2 A detailed structural schematic diagram of a first 3 μm high repetition rate high power femtosecond fiber laser provided by an embodiment of the present invention is shown;

[0019] Figure 3 A schematic diagram showing the general structure of a second 3μm high repetition rate high power femtosecond fiber laser provided by an embodiment of the present invention is shown;

[0020] Figure 4 The detailed structural diagram of the second 3μm high repetition rate and high power femtosecond fiber laser provided by the embodiment of the present invention is shown.

[0021] icon:

[0022] 1-ring cavity structure, 2-amplification unit, 11-first pump source, 12-first erbium-doped gain fiber, 13-nonlinear polarization rotation unit, 14-coupler, 15-first dichroic mirror, 16-gold mirror, 17-second dichroic mirror, 18-first wavelength division multiplexer, 21-second pump source, 22-second erbium-doped gain fiber, 23-second isolator, 24-second wavelength division multiplexer, 25-third dichroic mirror, 26-second quarter paddle, 27-second half paddle, 131-first half paddle, 132-first isolator, 133-first quarter paddle, a-collimating lens, b-focusing lens. DETAILED DESCRIPTION

[0023] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0024] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0025] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] The embodiment of the present invention provides a 3 μm high repetition rate high power femtosecond fiber laser, such as Figures 1 to 4 As shown, Figure 1 Figure 2 The first structural schematic diagram of the 3μm high repetition rate high power femtosecond fiber laser is shown. Figure 3 Figure 4The second structural schematic diagram of the 3μm high repetition rate high power femtosecond fiber laser is shown. Figure 1 and Figure 3 As shown in FIG. 1 , the two 3 μm high repetition rate high power femtosecond fiber lasers both include two parts, a ring cavity structure 1 and an amplification unit 2. Figure 2 and Figure 4 As shown (to make the drawing neat and clear, Figure 2 and Figure 4 The reference numerals of the ring cavity structure 1 and the amplifying unit 2 are not directly shown), and the ring cavity structure 1 at least includes a first pump source 11, a first erbium-doped gain fiber 12, a nonlinear polarization rotation unit 13 and a coupler 14. Among them, the first pump source 11 can be a 1.7μm core pump for emitting 1.7μm pump light; the first erbium-doped gain fiber 12 adopts commercial Er 3+ : ZBLAN optical fiber; the nonlinear polarization rotation unit 13 is a saturable absorber for achieving passive mode locking; the ratio of the coupler 14 is 50:50, and the light input to the coupler 14 can be evenly split.

[0027] Specifically, Figure 2 and Figure 4 As shown, the first pump source 11 emits 1.7 μm pump light to the first erbium-doped gain fiber 12, the first erbium-doped gain fiber 12 receives the 1.7 μm pump light and emits 3 μm laser to the nonlinear polarization rotation unit 13, the nonlinear polarization rotation unit 13 receives the 3 μm laser and emits 3 μm high repetition rate mode-locked laser to the coupler 14, the coupler 14 leaves part of the 3 μm high repetition rate mode-locked laser in the ring cavity structure 1 for circulation, and inputs the other part of the 3 μm high repetition rate mode-locked laser into the amplification unit 2; as shown Figure 2 As shown, the coupler 14 can transmit half of the input 3μm high repetition rate mode-locked laser into the subsequent optical path pulse cavity of the ring cavity structure 1, and reflect the remaining half of the laser into the subsequently connected amplification unit 2. Since the average power of the 3μm high repetition rate mode-locked laser is relatively low when the 3μm high repetition rate mode-locked laser is directly output from the coupler 14, in order to obtain high average power, the 3μm high repetition rate mode-locked laser needs to be amplified outside the ring cavity structure 1. In an embodiment of the present invention, the 3μm high repetition rate mode-locked laser input into the amplification unit 2 can be used as seed light, and combined with the signal light amplification technology provided by the amplification unit 2, the average power of the 3μm high repetition rate mode-locked laser can be increased to achieve high average power pulse output.

[0028] The 3 μm high repetition rate high power femtosecond fiber laser provided in the embodiment of the present invention uses a 1.7 μm fiber core pumped Er 3+Doped ZBLAN fiber can achieve high repetition rate mode-locked pulse output. Compared with cladding pumping technology, 1.7μm core pumping technology can greatly improve the conversion efficiency of lasers in active optical fibers, while reducing quantum loss. A shorter gain fiber can achieve higher gain, so the repetition rate of the mode-locked fiber laser can be greatly increased, reducing nonlinear effects and suppressing pulse splitting. Subsequently, this high repetition rate mode-locked fiber laser is used as a seed source and combined with amplification unit 2 again. In the process of amplifying high repetition rate signal light, due to the high repetition rate, the pulse peak power is low at the same average power, avoiding pulse splitting caused by the peak power clamping effect. At the same time, combined with soliton self-compression, it can take into account the requirements of high average power and narrow pulse width, and finally achieve 3μm high repetition rate and high power femtosecond laser stable output.

[0029] Alternatively, if Figure 2 As shown, Figure 2 Specifically shown is a 3μm high repetition rate high power femtosecond fiber laser in a free space structure. In the embodiment of the present invention, the ring cavity structure 1 also includes: a first dichroic mirror 15 arranged between the first pump source 11 and the first erbium-doped gain fiber 12, and the first dichroic mirror 15 can be arranged at a 45-degree angle to transmit the 1.7μm pump light emitted by the first pump source 11 to the first erbium-doped gain fiber 12, and the 3μm high repetition rate mode-locked laser transmitted by the reflection coupler 14. The first dichroic mirror 15 is used to adjust the optical path and separate the pump light and the high repetition rate mode-locked laser.

[0030] Alternatively, if Figure 2 As shown, the annular cavity structure 1 may further include: a gold mirror 16 disposed between the first dichroic mirror 15 and the coupler 14. The gold mirror 16 may also be disposed at an angle to reflect the 3 μm high repetition rate mode-locked laser transmitted by the coupler 14 to the first dichroic mirror 15, thereby adjusting the direction of the optical path so that the 3 μm high repetition rate mode-locked laser can circulate continuously in the annular cavity structure 1.

[0031] Alternatively, if Figure 2 As shown, the ring cavity structure 1 may further include: a second dichroic mirror 17 disposed between the first erbium-doped gain fiber 12 and the nonlinear polarization rotation unit 13 , and the second dichroic mirror 17 may be disposed at an angle of 45 degrees to reflect the 3 μm laser emitted by the first erbium-doped gain fiber 12 to the nonlinear polarization rotation unit 13 .

[0032] It should be noted that in Figure 2In the 3μm high repetition rate high power femtosecond fiber laser of the free space structure shown, a chain collimating lens a can be provided between the first pump source 11 and the first dichroic mirror 15, and between the first erbium-doped gain fiber 12 and the second dichroic mirror 17, so that the 1.7μm pump light emitted by the first pump source 11 and the 3μm high repetition rate mode-locked laser emitted by the first erbium-doped gain fiber 12 can be collimated. In addition, a focusing lens b can be provided between the first dichroic mirror 15 and the first erbium-doped gain fiber 12 to focus the 1.7μm pump light and inject it into the first erbium-doped gain fiber 12.

[0033] Alternatively, if Figure 4 As shown, it can be understood that Figure 4 The structure of a 3μm high repetition rate high power femtosecond fiber laser of an all-fiber structure is shown. In the embodiment of the present invention, the ring cavity structure 1 may also include: a first wavelength division multiplexer 18 disposed between the first pump source 11 and the first erbium-doped gain fiber 12, the first wavelength division multiplexer 18 does not make any changes to the light beam, and its function is to connect the first pump source 11 and the first erbium-doped gain fiber 12.

[0034] It can be seen that the 3μm high repetition rate high power femtosecond fiber laser provided by the embodiment of the present invention can be used in both space structures and all-fiber structures. Compared with the free space structure, the all-fiber structure can increase the stability of the mode locking, and the laser structure is compact and easy to integrate, which can greatly expand its practical application.

[0035] Alternatively, if Figure 2 and Figure 4 As shown, in the above two cases, the structure of the nonlinear polarization rotation unit 13 is consistent, and both include: a first half paddle 131, a first isolator 132 and a first quarter paddle 133. This structure can be placed in the ring cavity structure 1 to achieve mode-locked pulse output. Among them, the first half paddle 131 is used to change the polarization direction of the 3μm laser emitted by the first erbium-doped gain fiber 12, and adjust the 3μm laser from linear polarization to elliptically polarized light. The first isolator 132 is used to ensure that the 3μm laser is transmitted in a single direction, and the first quarter paddle 133 is used to adjust the polarization state of the 3μm laser and output 3μm high repetition rate mode-locked laser.

[0036] Alternatively, if Figure 2 and Figure 4As shown, in the above two cases, the amplification unit 2 at least includes: a second pump source 21, a second erbium-doped gain fiber 22 and a second isolator 23. The second pump source 21 emits 1.7μm pump light to the second erbium-doped gain fiber 22, the second isolator 23 receives the 3μm high repetition rate mode-locked laser split by the coupler 14 and emits it to the second erbium-doped gain fiber 22, and the second erbium-doped gain fiber 22 simultaneously receives the 1.7μm pump light emitted by the second pump source 21 and the 3μm high repetition rate mode-locked laser emitted by the second isolator 23. That is, the embodiment of the present invention uses the high repetition rate mode-locked fiber laser formed by the ring cavity structure 1 as a seed source, and again combines the 1.7μm core pumping technology to amplify the 2.8μm signal light to achieve high average power pulse output, and at the same time combines the soliton self-compression to take into account the requirements of high average power and narrow pulse width, and finally achieves the improvement of the average power of the 3μm high repetition rate mode-locked laser.

[0037] Alternatively, if Figure 4 As shown, in the case where the ring cavity structure 1 also includes a first wavelength division multiplexer 18, that is, in the case of a 3μm high repetition rate high power femtosecond fiber laser in an all-fiber structure, the amplification unit 2 may also include: a second wavelength division multiplexer 24 arranged between the second pump source 21 and the second erbium-doped gain fiber 22, for connecting the second pump source 21 and the second erbium-doped gain fiber 22.

[0038] Alternatively, if Figure 2 As shown, in the case where the ring cavity structure 1 also includes a first dichroic mirror 15, that is, in the case of a 3μm high repetition rate high power femtosecond fiber laser in a free space structure, the amplification unit 2 may also include: a third dichroic mirror 25 arranged between the second pump source 21 and the second erbium-doped gain fiber 22, the third dichroic mirror 25 being used to transmit the 1.7μm pump light emitted by the second pump source 21 to the second erbium-doped gain fiber 22, and to reflect the 3μm high repetition rate mode-locked laser emitted by the second isolator 23 to the second erbium-doped gain fiber 22.

[0039] Alternatively, Figure 2As shown, in the case of a 3μm high repetition rate high power femtosecond fiber laser in a free space structure, the amplification unit 2 may further include: a second quarter paddle 26 and a second half paddle 27 which are sequentially arranged on the light output side of the second isolator 23. Among them, the second quarter paddle 26 functions to change the polarization state of the 3μm high repetition rate mode-locked laser, and the second half paddle 27 functions to change the polarization direction of the 3μm high repetition rate mode-locked laser. Specifically, the combination of the second half paddle 27 and the second quarter paddle 26 can control the polarization state of the output laser (i.e., the 3μm high repetition rate mode-locked laser), and by adjusting the angles of the second half paddle 27 and the second quarter paddle 26, the 3μm high repetition rate mode-locked laser can be converted from a linear polarization state to an elliptical polarization state. Compared with a laser in a linear polarization state, a laser in an elliptical polarization state can suppress the Raman effect during the amplification process. Therefore, the amplification efficiency is improved and the average power is increased.

[0040] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technical solution that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A 3μm high repetition rate high power femtosecond fiber laser, characterized in that: include: A ring cavity structure (1) and an amplification unit (2); the ring cavity structure (1) comprises at least a first pump source (11), a first erbium-doped gain optical fiber (12), a nonlinear polarization rotation unit (13) and a coupler (14); The first pump source (11) emits 1.7 μm pump light to the first erbium-doped gain fiber (12); the first erbium-doped gain fiber (12) receives the 1.7 μm pump light and emits 3 μm laser to the nonlinear polarization rotation unit (13); the nonlinear polarization rotation unit (13) receives the 3 μm laser and emits 3 μm high repetition rate mode-locked laser to the coupler (14); the coupler (14) retains part of the 3 μm high repetition rate mode-locked laser in the ring cavity structure (1) for circulation, and inputs another part of the 3 μm high repetition rate mode-locked laser into the amplification unit (2); the amplification unit (2) is used to increase the average power of the 3 μm high repetition rate mode-locked laser.

2. The 3μm high repetition rate high power femtosecond fiber laser according to claim 1, characterized in that: The annular cavity structure (1) further comprises: a first dichroic mirror (15) arranged between the first pump source (11) and the first erbium-doped gain fiber (12), the first dichroic mirror (15) being used to transmit the 1.7 μm pump light emitted by the first pump source (11) to the first erbium-doped gain fiber (12), and to reflect the 3 μm high repetition rate mode-locked laser transmitted by the coupler (14).

3. The 3 μm high repetition rate high power femtosecond fiber laser according to claim 2, characterized in that: The annular cavity structure (1) further comprises: a gold mirror (16) arranged between the first dichroic mirror (15) and the coupler (14), the gold mirror (16) being used to reflect the 3 μm high repetition rate mode-locked laser transmitted by the coupler (14) to the first dichroic mirror (15).

4. The 3 μm high repetition rate high power femtosecond fiber laser according to claim 3, characterized in that: The annular cavity structure (1) further comprises: a second dichroic mirror (17) arranged between the first erbium-doped gain optical fiber (12) and the nonlinear polarization rotation unit (13), wherein the second dichroic mirror (17) is used to reflect the 3 μm laser emitted by the first erbium-doped gain optical fiber (12) to the nonlinear polarization rotation unit (13).

5. The 3 μm high repetition rate high power femtosecond fiber laser according to claim 1, characterized in that: The annular cavity structure (1) further comprises: a first wavelength division multiplexer (18) arranged between the first pump source (11) and the first erbium-doped gain optical fiber (12).

6. The 3 μm high repetition rate high power femtosecond fiber laser according to any one of claims 1 to 5, characterized in that: The nonlinear polarization rotation unit (13) comprises: a first half-blade (131), a first isolator (132) and a first quarter-blade (133); the first half-blade (131) is used to change the polarization direction of the 3 μm laser emitted by the first erbium-doped gain optical fiber (12); the first isolator (132) is used to ensure that the 3 μm laser is transmitted in a single direction; and the first quarter-blade (133) is used to adjust the polarization state of the 3 μm laser and output the 3 μm high repetition rate mode-locked laser.

7. The 3 μm high repetition rate high power femtosecond fiber laser according to any one of claims 1 to 5, characterized in that: The amplification unit (2) comprises at least: a second pump source (21), a second erbium-doped gain optical fiber (22) and a second isolator (23); The second pump source (21) emits 1.7 μm pump light to the second erbium-doped gain fiber (22); the second isolator (23) receives the 3 μm high repetition rate mode-locked laser split by the coupler (14) and emits it to the second erbium-doped gain fiber (22); the second erbium-doped gain fiber (22) receives the 1.7 μm pump light emitted by the second pump source (21) and the 3 μm high repetition rate mode-locked laser emitted by the second isolator (23), thereby achieving an increase in the average power of the 3 μm high repetition rate mode-locked laser.

8. The 3 μm high repetition rate high power femtosecond fiber laser according to claim 7, characterized in that: When the annular cavity structure (1) further includes the first wavelength division multiplexer (18), the amplification unit (2) further includes: a second wavelength division multiplexer (24) arranged between the second pump source (21) and the second erbium-doped gain optical fiber (22).

9. The 3 μm high repetition rate high power femtosecond fiber laser according to claim 7, characterized in that: When the annular cavity structure (1) further includes the first dichroic mirror (15), the amplification unit (2) further includes: a third dichroic mirror (25) arranged between the second pump source (21) and the second erbium-doped gain fiber (22); The third dichroic mirror (25) is used to transmit the 1.7 μm pump light emitted by the second pump source (21) to the second erbium-doped gain fiber (22), and to reflect the 3 μm high repetition rate mode-locked laser emitted by the second isolator (23) to the second erbium-doped gain fiber (22).

10. The 3 μm high repetition rate high power femtosecond fiber laser according to claim 9, characterized in that: The amplifying unit (2) further comprises: a second quarter paddle (26) and a second half paddle (27) which are sequentially arranged on the light exit side of the second isolator (23).

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