A broadband, low-noise, ultra-stable laser source for laser fusion systems

Abstract

The present invention discloses a broadband, low-noise, ultra-stable laser source for use in laser fusion systems, including: a seed source for generating lasers that require intensity noise suppression; an optical amplification module for achieving intensity noise suppression in medium and high frequency bands and preliminary amplification of laser power; a main amplification module for further amplifying the laser power, while achieving intensity noise suppression in low frequency bands through nonlinear effects; an analog-digital hybrid photoelectric feedback module for acquiring an error signal and performing modulation feedback on the main amplification module to achieve deeper suppression of intensity noise in low frequency bands. The present invention integrates intensity noise (RIN) suppression and power amplification, and adopts analog-digital hybrid photoelectric feedback technology to significantly reduce intensity noise in lower frequency bands and larger bandwidths, thereby achieving low-intensity noise lasers with higher power output. The present invention can be widely used in the field of laser light source technology.

Description

Technical Field

[0001] The present invention relates to the technical field of laser light sources, and in particular to a broadband, low-noise, ultra-stable laser source applied to a laser fusion system. Background Art

[0002] The intensity noise of the laser, that is, the fluctuation of the laser output power, is crucial to the accuracy of a variety of detection applications. This includes fields such as fusion energy development, lidar, material forming and nonlinear frequency conversion. However, different applications require different noise performance in different frequency bands. For example, technical solutions such as inertial confinement fusion (ICF) in fusion energy development also put forward higher requirements for high-power and low-noise lasers. Because achieving higher-quality laser fusion requires more stable and more precisely controlled laser signals to meet the needs of laser device power balance and target pellet symmetric compression. As the light source of the entire large-scale laser device, the output stability of the laser affects the final stability of each light output and the waveform control accuracy. Therefore, in the current large-scale laser devices used for ICF research, as well as the subsequent development of ICF laser driver technology, it is of great application significance to study laser devices with high power and low intensity noise and their implementation technology.

[0003] Therefore, the research and realization of broadband and low-intensity noise lasers with required power has become an important topic in the field of laser technology to meet the precision requirements of different applications.

[0004] In the field of intensity noise suppression, researchers have extensively studied a variety of techniques, including optoelectronic feedback, mode cleaners, and gain saturation. The optoelectronic feedback method usually involves sampling the optoelectronic signal and dynamically adjusting the power fluctuation of the final output laser in combination with a feedback device. For example, researchers at Harvard University successfully used a combination of an electro-optic modulator (EOM) and an acousto-optic modulator (AOM) to achieve an intensity noise suppression effect of 15dB in the frequency range of 100Hz to 1MHz. However, due to the limitation of the bandwidth of the servo or feedback system, it is still challenging to achieve excellent intensity noise suppression over a wide frequency range. Mode cleaners are an effective way to reduce intensity noise, especially when used in combination with optoelectronic feedback technology. However, mode cleaners based on spatial optical cavity structures introduce some spatial optical elements, increase the complexity of use, and increase sensitivity to environmental interference. The third technology utilizes the gain saturation effect of semiconductor optical amplifiers or booster optical amplifiers to effectively suppress intensity noise over a wide frequency range. However, due to the limitations of semiconductor material properties and carrier dynamics, the frequency band that can suppress intensity noise is also subject to certain restrictions, and the output power is usually limited to tens of milliwatts. Although external fiber amplifiers can effectively increase the output laser power, it is still challenging to maintain or suppress the intensity noise during laser amplification, especially for ultra-low intensity noise lasers. Summary of the invention

[0005] In order to solve at least one of the technical problems existing in the prior art to a certain extent, the object of the present invention is to provide a broadband, low-noise, ultra-stable laser source for use in a laser fusion system.

[0006] The technical solution adopted by the present invention is:

[0007] A broadband, low-noise, ultra-stable laser source for use in a laser fusion system, comprising:

[0008] A seed source for generating laser light for which intensity noise suppression is required;

[0009] Optical amplification module, used to achieve intensity noise suppression in the mid- and high-frequency bands and preliminary amplification of laser power;

[0010] The main amplifier module is used to further amplify the laser power and suppress the intensity noise in the low frequency band through nonlinear effects;

[0011] The analog-digital hybrid optoelectronic feedback module is used to obtain the error signal and modulate the feedback pump source in the main amplifier module to achieve deeper suppression of intensity noise in the low frequency band.

[0012] Furthermore, the seed source includes but is not limited to fixed wavelength or tunable lasers in the form of different gain media such as optical fiber, solid, semiconductor, gas, etc.

[0013] Furthermore, the output coupling mode of the seed source includes but is not limited to optical fiber coupling, spatial light output, grating coupling, etc.

[0014] Further, the optical amplification module includes an optical amplifier and an optical circulator; the input end of the optical amplifier is connected to the output end of the seed source, the output end of the optical amplifier is connected to the input end of the optical circulator, and the output end of the optical circulator serves as the output end of the optical amplification module;

[0015] The laser generated by the seed source is subjected to mid- and high-frequency noise suppression by the optical amplifier, and then the laser is transmitted back and forth in the entire optical path through the optical circulator, so that the laser is amplified by the main amplifier module at the subsequent stage and then output to the system.

[0016] Further, the optical amplifier includes a semiconductor optical amplifier and a fiber optical amplifier; the type of semiconductor optical amplifier may include but is not limited to booster semiconductor optical amplifiers and other different types of semiconductor optical amplifiers. The type of fiber optical amplifier may include but is not limited to erbium-doped fiber amplifiers, ytterbium-doped fiber amplifiers and other different types of fiber amplifiers.

[0017] Furthermore, the main task of the optical circulator is to ensure that the optical signal can complete the transmission to the next-level module and enable the optical signal of the next level to complete the output. Its types include but are not limited to multi-port fiber circulators, electro-optical circulators, silicon-based circulators, etc.

[0018] Furthermore, the main amplification module includes a multi-mode pump, a single-mode pump, a laser beam combining device, a gain optical fiber and a light return device;

[0019] The first input end of the laser beam combining device is connected to the output end of the optical amplification module, the second input end of the laser beam combining device is connected to the output end of the multi-mode pump, and the third input end of the laser beam combining device is connected to the output end of the single-mode pump; the output end of the laser beam combining device is connected to the input end of the gain optical fiber, and the output end of the gain optical fiber is connected to the light return device; the driving end of the single-mode pump is connected to the analog-digital hybrid optoelectronic feedback module;

[0020] The optical power signal output by the optical amplifier module is received by the laser beam combining device in the form of fiber coupling, and the optical power is amplified by the gain fiber. At the same time, the nonlinear effect of the gain fiber in the amplification process is combined to achieve the preliminary suppression of the intensity noise in the low frequency band.

[0021] The output power of the single-mode pump is feedback-controlled through an analog-digital hybrid optoelectronic feedback module to further suppress the intensity noise of the laser in the low frequency band.

[0022] Furthermore, the types of gain fibers include but are not limited to gain fibers doped with rare earth elements, titanium sapphire, optical glass fibers, etc. Feedback forms may include pump light intensity modulation, pump laser diode power modulation, and the like.

[0023] Furthermore, the light return device is used to realize the round-trip transmission of the laser signal in the gain fiber to fully utilize the nonlinear effect of the gain fiber; the light return device includes but is not limited to a fiber reflector, a coupler, a laser reflector group, etc.

[0024] Further, the analog-digital hybrid photoelectric feedback module includes an optical isolator, a photodetector, an analog proportional-integral-differentiator and a digital proportional-integral-differentiator;

[0025] The input end of the optical splitter isolator is connected to the optical amplifier module, the output end of the optical splitter isolator is connected to the input end of the photodetector, the output end of the photodetector is respectively connected to the input end of the analog proportional integral differentiator and the input end of the digital proportional integral differentiator, and the output signal of the analog proportional integral differentiator and the output signal of the digital proportional integral differentiator are fused and fed back to the main amplifier module;

[0026] The error signal is converted into an electrical signal through a photodetector, and the electrical signal is transmitted to an analog proportional-integral-differentiator and a digital proportional-integral-differentiator at the same time. The characteristics of the two forms of proportional-integral-differentiator are utilized to realize power fluctuation monitoring, error signal acquisition and feedback over a wider range in the low-frequency band.

[0027] Furthermore, the analog proportional-integral-differentiator includes an analog proportional integrator, an analog proportional-integral-differentiator, an analog proportional controller or an analog integral controller; the digital proportional-integral-differentiator includes a digital proportional integrator, a digital proportional-integral-differentiator, a digital proportional controller or a digital integral controller.

[0028] The beneficial effects of the present invention are as follows: the present invention integrates intensity noise (RIN) suppression and power amplification, and adopts analog-digital hybrid optoelectronic feedback technology, which significantly reduces intensity noise in a lower frequency band and a larger bandwidth range, and realizes a low-intensity noise laser with a higher power output. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the embodiments of the present invention or the drawings of related technical solutions in the prior art are introduced below. It should be understood that the drawings introduced below are only for the convenience of clearly describing some embodiments of the technical solutions of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 Schematic diagram of the structure of a broadband, low-noise, ultra-stable laser source applied to a laser fusion system in an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of laser intensity noise before and after suppression in an embodiment of the present invention;

[0032] Figure 3 is a relative intensity noise comparison diagram after two different processings in an embodiment of the present invention;

[0033] Figure 4 is a relative intensity noise comparison diagram after two different processings in an embodiment of the present invention;

[0034] Figure 5 is a schematic diagram of the output of a laser at a preset power in an embodiment of the present invention;

[0035] Figure 6 It is a schematic diagram of the fluctuation of the polarization splitting ratio within 4 hours in an embodiment of the present invention.

[0036] Figure numerals: 01 seed source; 02 optical amplification module; 02-1 optical amplifier; 02-2 optical circulator; 03 main amplification module; 03-1 multi-mode pump; 03-2 single-mode pump; 03-3 laser beam combining device; 03-4 gain optical fiber; 03-5 optical return device; 04 analog-digital hybrid optoelectronic feedback module; 04-1 optical isolator; 04-2 photodetector; 04-3 analog proportional integral differentiator; 04-4 digital proportional integral differentiator. DETAILED DESCRIPTION

[0037] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and are not to be construed as limitations of the present invention. For the step numbers in the following embodiments, they are only provided for the convenience of explanation, and the order between the steps is not limited in any way, and the execution order of each step in the embodiment can be adaptively adjusted according to the understanding of those skilled in the art.

[0038] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are 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, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0039] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0040] In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0041] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0042] In view of the existing technical problems, the present invention discloses a broadband low-noise ultra-stable laser source for laser fusion system, which has the characteristics of low intensity noise, broadband suppression, and high output power. In order to simultaneously realize high-power, large-bandwidth, low-intensity noise laser output including Hz-level frequency bands, the present invention proposes a dual-gain saturation effect technology based on boosting semiconductor optical amplifiers and reflective ytterbium-doped fiber amplifiers, combined with analog-digital hybrid optoelectronic feedback technology. Specifically, the present invention successfully achieves a relative intensity noise lower than -150dB / Hz in the frequency range of 0.1Hz to 10GHz, especially in the bandwidth range of 10Hz to 10GHz. The RIN level is reduced to -160dB / Hz, and a laser light source with RIN close to the shot noise limit is achieved in the range of more than 29 octaves. In addition, the output power of the light source obtained by the present invention exceeds 10W, and the long-term polarization extinction ratio reaches more than 20dB, with high output power and high polarization stability. The objectives of the present invention are achieved by the following technical solutions. These characteristics make the present invention have important application prospects and potential in related fields.

[0043] like Figure 1 As shown, this embodiment provides a broadband low-noise ultra-stable laser source applied to a laser fusion system, comprising:

[0044] Seed source 01, used to generate laser light that needs to suppress intensity noise;

[0045] Optical amplifier module 02, used to achieve intensity noise suppression in the mid- and high-frequency bands and preliminary amplification of laser power;

[0046] The main amplifier module 03 is used to further amplify the laser power and achieve intensity noise suppression in the low frequency band through nonlinear effects;

[0047] The analog-digital hybrid optoelectronic feedback module 04 is used to obtain the error signal and modulate the feedback pump source in the main amplification module to provide feedback, thereby achieving deeper suppression of the intensity noise in the low-frequency band and further amplifying the laser power.

[0048] As an optional implementation, the output coupling mode of the seed source 01 includes but is not limited to fiber coupling, spatial light output, grating coupling, etc. In this embodiment, the output coupling mode of the seed source is fiber coupling, that is, it is input into the subsequent system through optical fiber.

[0049] As an optional embodiment, the optical amplification module 02 includes an optical amplifier 02-1 and an optical circulator 02-2. After the laser generated by the seed source is subjected to mid- and high-frequency band noise suppression by the optical amplifier 02-1, the laser is transmitted back and forth in the entire optical path through the optical circulator 02-2, so that the laser is amplified by the main amplifier module at the rear stage and then output to the system. The optical amplifier 02-1 includes a semiconductor optical amplifier and a fiber optical amplifier; the types of semiconductor optical amplifiers may include but are not limited to different types of semiconductor optical amplifiers such as booster semiconductor optical amplifiers. The types of fiber optical amplifiers may include but are not limited to different types of fiber amplifiers such as erbium-doped fiber amplifiers and ytterbium-doped fiber amplifiers. The main task of the optical circulator 02-2 is to ensure that the optical signal can complete the transmission to the next-level module and enable the optical signal of the next level to complete the output. Its types include but are not limited to multi-port fiber circulators, electro-optical circulators, silicon-based circulators, etc.

[0050] In this embodiment, the optical amplifier module is composed of a booster semiconductor optical amplifier and an optical circulator. The optical amplifier gain saturation effect of the semiconductor is used to suppress the intensity noise in the medium and high frequency bands and initially increase the power. After the laser generated by the seed source is subjected to noise suppression in the medium and high frequency bands by the semiconductor optical amplifier, the laser is transmitted back and forth in the entire optical path through the optical circulator, so that the light is amplified by the main amplifier module at the rear stage and then output to the system.

[0051] As an optional implementation, the main amplifier module 03 includes a multi-mode pump 03-1, a single-mode pump 03-2, a laser beam combining device 03-3, a gain fiber 03-4 and a light return device 03-5. The laser beam combining device 03-3 receives the optical power signal output by the optical amplifier module 02 in the form of fiber coupling, and uses the gain fiber 03-4 to amplify the optical power. At the same time, the nonlinear effect of the gain fiber 03-4 in the amplification process is combined to achieve preliminary suppression of the intensity noise in the low frequency band. The output power of the single-mode pump 03-2 is feedback-controlled by the analog-digital hybrid optoelectronic feedback module 04 to further suppress the intensity noise in the low frequency band of the laser and increase the power. The types of gain fiber 03-4 include but are not limited to gain fibers doped with rare earth elements, titanium sapphire, optical glass fibers, etc. Feedback forms can include pump light intensity modulation, pump laser diode power modulation, etc. The optical return device 03-5 is used to realize the round-trip transmission of the laser signal in the gain optical fiber to fully utilize its nonlinear effect; the optical return device includes but is not limited to optical fiber reflectors, couplers, laser reflector groups, etc.

[0052] In this embodiment, the laser beam combining device receives the optical power signal of the previous stage in the form of optical fiber coupling, and uses the gain fiber to amplify the optical power. At the same time, the nonlinear effect of the gain fiber in the amplification process is combined to achieve preliminary suppression of the intensity noise in the low frequency band. And combined with the feedback adjustment of the pump power, the low-frequency intensity noise can be further suppressed. This module introduces the laser signal generated by the optical amplifier module 02, uses the multi-mode pump 03-1 and the single-mode pump 03-2 to pump the gain fiber 03-4, and at the same time, the output power of the single-mode pump 03-2 is feedback-controlled by the analog-digital hybrid optoelectronic feedback module 04, so as to further suppress the low-frequency intensity noise of the laser and increase the power.

[0053] As an optional implementation, the analog-digital hybrid photoelectric feedback module 04 includes an optical isolator 04-1, a photodetector 04-4, an analog proportional integral differentiator 04-3, and a digital proportional integral differentiator 04-4. The error signal is converted into an electrical signal by the photodetector 04-4, and the electrical signal is simultaneously transmitted to the analog proportional integral differentiator 04-3 and the digital proportional integral differentiator 04-4, and the characteristics of the two forms of proportional integral differentiators are utilized to realize power fluctuation monitoring, error signal acquisition and feedback over a wider range in the low frequency band. The types of digital proportional integrators and analog proportional integrators include but are not limited to analog / digital proportional integrators, analog / digital proportional integral differentiators, analog / digital proportional controllers, analog / digital integral controllers, etc.

[0054] In this embodiment, the main parts of the analog-digital hybrid photoelectric feedback module include the output end of the optical isolator 04-1, the photodetector 04-2 and the analog-digital proportional integral differentiator. In the device, a small part of the optical signal is transmitted to the photodetector by the optical isolator, and the fluctuation signal of the optical power is converted into an electrical signal by the photodetector, and then the analog proportional integral differentiator and the digital proportional integral differentiator are used for calculation processing, so that the electrical signal converted by the photodetector is converted into a driving signal for pump power regulation, and this driving signal dynamically changes the output power of the single-mode pump 03-2 to achieve the suppression of intensity noise in the low-frequency range. In addition, the main optical signal is output from the large end of the optical isolator 04-1, and the output main optical signal is a single-frequency laser signal with low intensity noise in a wide frequency band, which can be used in various subsequent related applications.

[0055] See also Figure 2 , Figure 2 By comparing the schematic diagrams of the intensity noise of the laser before and after suppression, it is found that the device of this embodiment successfully achieves significant suppression of the relative intensity noise of the laser in the range of 0.1 Hz to 380 MHz.

[0056] See also Figure 3 ,exist Figure 3 In the figure, the gray curve represents the relative intensity noise after the gain saturation effect of a single-stage semiconductor optical amplifier is suppressed. Thanks to this part, the intensity noise in the high frequency range (10 kHz to 350 MHz) of the laser is effectively suppressed, close to the shot noise limit. The black curve shows the relative intensity noise diagram of the dual gain saturation effect in the semiconductor optical amplifier and the reflective ytterbium-doped fiber amplifier, combined with the analog-digital hybrid optoelectronic feedback technology. Thanks to this part of the structure, the relative intensity noise in the low frequency range (0.1 Hz to 10 kHz) of the laser is significantly suppressed, and the RIN above 1 Hz has been maintained below -150 dB / Hz.

[0057] See also Figure 4 ,exist Figure 4 In the figure, the gray curve represents the relative intensity noise after the dual gain saturation effect is suppressed by using a semiconductor optical amplifier and a reflective ytterbium-doped fiber amplifier, while the black curve represents the relative intensity noise diagram using the dual gain saturation effect in a semiconductor optical amplifier and a reflective ytterbium-doped fiber amplifier, combined with analog-digital hybrid optoelectronic feedback technology. Thanks to this experimental setup, the relative intensity noise of the laser has achieved significant RIN suppression in a large frequency range from 0.1Hz to 380MHz, while the RIN above 1Hz has been maintained below -150dB / Hz, and the RIN level has been suppressed to -160dB / Hz from 10Hz to 10GHz.

[0058] See also Figure 5 , Figure 5 The power stability is demonstrated while maintaining an output power of 10.8W. Thanks to this experimental device, the laser can maintain a high-power stable output. Figure 6 , Figure 6 A schematic diagram showing the fluctuation of the polarization splitting ratio over 4 hours.

[0059] In general, this embodiment adopts the dual gain saturation effect technology based on semiconductor optical amplifiers and reflective ytterbium-doped fiber amplifiers, and the suppression performance of the intensity noise corresponding to the semiconductor optical amplifier and the ytterbium-doped fiber amplifier in different frequency bands complements each other, greatly suppressing the intensity noise in the medium and high frequency bands and the intensity noise in the low frequency band, and taking into account the further improvement of the low-frequency intensity noise suppression performance by combining analog-digital hybrid optoelectronic feedback technology. The results show that in the medium and low frequency bands, that is, from 0.1Hz to 380MHz, significant relative intensity noise (RIN) suppression is successfully achieved, and the RIN above 1Hz is maintained below -150dB / Hz. It is worth noting that in a wider frequency range, that is, from 10Hz to 10GHz, the RIN level is suppressed to -160dB / Hz, almost approaching the limit of shot noise. This description more clearly expresses the technical achievements of this embodiment.

[0060] In summary, the present invention has at least the following advantages and beneficial effects compared to the prior art:

[0061] (1) The present invention integrates intensity noise (RIN) suppression and power amplification, and adopts a multi-stage optical amplification strategy, which can increase the power of the output light, obtain high-power output, and achieve intensity noise suppression within an ultra-wide frequency band, successfully achieving intensity noise suppression in the mid- and low-frequency bands.

[0062] (2) The laser intensity noise suppression and power amplification are seamlessly integrated, and the dual gain saturation effect in the semiconductor optical amplifier (BOA) and the reflective erbium-doped fiber amplifier (RYDFA) is fully utilized. Through the combined dual gain saturation effect, the present invention greatly broadens the suppression range of the laser intensity noise.

[0063] (3) The present invention introduces analog-digital hybrid photoelectric feedback technology, which effectively realizes a significant suppression of intensity noise in the low-frequency band. The combination of dual gain saturation effect and analog-digital hybrid photoelectric feedback technology enables us to achieve significant intensity noise suppression in the low-frequency band and reduce the intensity noise level to close to the shot noise limit within the bandwidth range of 10Hz to 10GHz. In addition, a higher output power can be achieved at the same time. These innovative features give the present invention unique advantages and prospects in the field of high-power low-intensity noise lasers.

[0064] In the above description of this specification, the description with reference to the terms "one embodiment / example", "another embodiment / example" or "certain embodiments / examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0065] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0066] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the above embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A broadband, low-noise, ultra-stable laser source for laser fusion system, characterized in that: include: A seed source for generating laser light for which intensity noise suppression is required; Optical amplification module, used to achieve intensity noise suppression in the mid- and high-frequency bands and preliminary amplification of laser power; The main amplifier module is used to further amplify the laser power and achieve low-frequency intensity noise suppression through nonlinear effects. The analog-digital hybrid optoelectronic feedback module is used to obtain the error signal and perform modulation feedback on the main amplifier module to achieve deeper suppression of low-frequency intensity noise. The optical amplification module comprises an optical amplifier and an optical circulator; the input end of the optical amplifier is connected to the output end of the seed source, the output end of the optical amplifier is connected to the input end of the optical circulator, and the output end of the optical circulator serves as the output end of the optical amplification module; The laser generated by the seed source is subjected to mid- and high-frequency band noise suppression by the optical amplifier, and then the laser is transmitted back and forth in the entire optical path through the optical circulator, so that the laser is amplified by the main amplifier module at the subsequent stage and then output to the system; The main amplification module includes a multi-mode pump, a single-mode pump, a laser beam combining device, a gain optical fiber and a light return device; The first input end of the laser beam combining device is connected to the output end of the optical amplification module, the second input end of the laser beam combining device is connected to the output end of the multi-mode pump, and the third input end of the laser beam combining device is connected to the output end of the single-mode pump; the output end of the laser beam combining device is connected to the input end of the gain optical fiber, and the output end of the gain optical fiber is connected to the light return device; the driving end of the single-mode pump is connected to the analog-digital hybrid optoelectronic feedback module; The optical power signal output by the optical amplifier module is received by the laser beam combining device in the form of fiber coupling, and the optical power is amplified by the gain fiber. At the same time, the nonlinear effect of the gain fiber in the amplification process is combined to achieve the preliminary suppression of the intensity noise in the low frequency band. The output power of the single-mode pump is feedback-controlled through an analog-digital hybrid optoelectronic feedback module to further suppress the intensity noise of the laser in the low frequency band. The analog-digital hybrid photoelectric feedback module includes an optical isolator, a photodetector, an analog proportional-integral-differentiator and a digital proportional-integral-differentiator; The input end of the optical splitter isolator is connected to the optical amplifier module, the output end of the optical splitter isolator is connected to the input end of the photodetector, the output end of the photodetector is respectively connected to the input end of the analog proportional integral differentiator and the input end of the digital proportional integral differentiator, and the output signal of the analog proportional integral differentiator and the output signal of the digital proportional integral differentiator are fused and fed back to the main amplifier module; The error signal is converted into an electrical signal through a photodetector, and the electrical signal is transmitted to an analog proportional-integral-differentiator and a digital proportional-integral-differentiator at the same time. The characteristics of the two forms of proportional-integral-differentiator are utilized to realize power fluctuation monitoring, error signal acquisition and feedback over a wider range in the low-frequency band.

2. A broadband, low-noise, ultra-stable laser source for laser fusion system according to claim 1, characterized in that: The output coupling mode of the seed source includes a fiber coupling mode, a spatial light output mode or a grating coupling mode.

3. The broadband, low-noise, ultra-stable laser source for laser fusion system according to claim 1, characterized in that: The optical amplifier includes a semiconductor optical amplifier and a fiber optical amplifier; the fiber optical amplifier includes an erbium-doped fiber amplifier or an ytterbium-doped fiber amplifier.

4. The broadband, low-noise, ultra-stable laser source for laser fusion system according to claim 1, characterized in that: The optical circulator is used to ensure that the optical signal can complete the transmission to the next-stage module and enable the optical signal of the next stage to complete the output; The optical circulator includes a multi-port optical fiber circulator, an electro-optical circulator or a silicon-based circulator.

5. The broadband, low-noise, ultra-stable laser source for laser fusion system according to claim 1, characterized in that: The gain optical fiber includes a gain optical fiber doped with rare earth elements, titanium sapphire or optical glass optical fiber; Feedback forms include pump light intensity modulation or pump laser diode power modulation.

6. The broadband, low-noise, ultra-stable laser source for laser fusion system according to claim 1, characterized in that: The light return device is used to realize the round-trip transmission of the laser signal in the gain optical fiber, so as to fully utilize the nonlinear effect of the gain optical fiber; the light return device is realized by using an optical fiber reflector, a coupler or a laser reflector group.

7. The broadband, low-noise, ultra-stable laser source for laser fusion system according to claim 1, characterized in that: The analog proportional integral differentiator includes an analog proportional integrator, an analog proportional integral differentiator, an analog proportional controller or an analog integral controller; the digital proportional integral differentiator includes a digital proportional integrator, a digital proportional integral differentiator, a digital proportional controller or a digital integral controller.

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