Seed laser and fiber laser coherent combining system for optical path control

Abstract

A seed laser and fiber laser coherent combining system for implementing optical path control includes a picosecond pulse source, a high-speed photodetector, an intensity modulator, a single-frequency laser, and a phase modulation unit. The picosecond pulse source is connected to the high-speed photodetector, and the single-frequency laser is connected to the intensity modulator. The high-speed photodetector converts the detected pulsed optical signal into a pulsed electrical signal and loads it into the intensity modulator. The intensity modulator intensity-modulates the laser output from the single-frequency laser to convert it into a pulsed optical signal. The intensity modulator is connected to the phase modulation unit, which phase-modulates the pulsed optical signal output by the intensity modulator before outputting it. The seed laser is used in a fiber laser coherent combining system. When implementing optical path control, its significant advantage is that the center wavelength of the picosecond pulse source does not need to be consistent with the center wavelength of the single-frequency seed laser in the coherent combining system. That is, one picosecond pulse source can be used in multiple coherent combining systems with different center wavelengths.

Description

Technical Field

[0001] The present invention mainly relates to the field of optical fiber laser technology, in particular to a seed laser and an optical fiber laser coherent combining system for implementing optical path control. Background Art

[0002] As an important high-brightness light source, the power scaling capabilities of high-power, narrow-linewidth, linearly polarized fiber lasers have long been a research hotspot in the laser field. Existing research indicates that fiber laser output power is limited by physical factors such as nonlinear effects and mode instability, and these limiting factors are polarization-dependent. Therefore, increasing the power of high-power, narrow-linewidth, linearly polarized fiber lasers is more difficult.

[0003] Coherent combining of multiple lasers based on active phase control is an effective technology for achieving power outputs exceeding the limits of single-channel fiber lasers, and has already achieved power outputs in the 10,000-watt range. In coherent combining systems, achieving good coherent combining results requires precise control of the optical path length differences of the multiple lasers involved, keeping them within the coherence length. Single-frequency lasers, with coherence lengths exceeding several kilometers, are ideal light sources for coherent combining systems. However, due to significant nonlinear effects and mode instability, single-frequency laser output power currently only reaches kilowatts. To achieve high power output while effectively suppressing nonlinear effects, phase modulation techniques are often used to broaden the linewidth of a single-frequency seed laser, producing a narrow linewidth seed laser with a linewidth on the order of 0.1 nm. This narrow linewidth seed laser is then injected into an all-fiber multi-stage amplifier chain for power amplification. The coherence length of these narrow linewidth seeds is only a few centimeters. In actual system construction, the optical path length differences of the participating lasers are difficult to control within this range. Furthermore, fluctuations in output power, environmental disturbances, and jitter introduced by the water cooling system can also affect the optical path difference. Therefore, high-precision optical path adjustment and control is one of the key technologies of coherent combining systems.

[0004] Currently, the common way to adjust the optical path is to replace the single-frequency seed laser in the coherent combining system with a picosecond pulse source, use a high-speed photodetector to measure the time delay Δτ between each light beam at the output end of the combined laser, and then calculate the optical path difference based on this and perform optical path compensation. This method requires the use of a picosecond pulse source with exactly the same center wavelength as the seed laser of the coherent combining system. At the same time, since the center wavelength of the optical fiber device in the subsequent optical fiber amplification link is consistent with the seed laser wavelength, it means that different seed laser wavelengths require a picosecond pulse source with the corresponding wavelength, which is not conducive to the construction and experimental testing of the actual system. Therefore, the development of a precise control device for the optical path of fiber laser coherent combining that is independent of the center wavelength of the picosecond pulse source is of great significance for improving the efficiency of experimental testing. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention proposes a seed laser and a fiber laser coherent combining system for implementing optical path control.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a seed laser for implementing optical path control, comprising: a picosecond pulse source, a high-speed photodetector, an intensity modulator, a single-frequency laser, and a phase modulation unit; the output fiber of the picosecond pulse source is connected to the high-speed photodetector, and the high-speed photodetector converts the detected pulse light signal into a pulse electrical signal and loads it into the intensity modulator; the intensity modulator is connected to the single-frequency laser, and the intensity modulator performs intensity modulation on the laser output by the single-frequency laser to convert the laser into a pulse light signal; the phase modulation unit is connected to the intensity modulator, and the phase modulation unit performs phase modulation on the pulse light signal output by the intensity modulator and then outputs it.

[0008] According to the seed laser for implementing optical path control provided by the present invention, the phase modulation unit includes a modulation signal source, a radio frequency signal amplifier, and an electro-optical phase modulator; the modulation signal source is connected to the radio frequency signal amplifier, the radio frequency signal amplifier amplifies the modulation signal output by the modulation signal source and then loads it into the electro-optical phase modulator; the intensity modulator is connected to the electro-optical phase modulator, and the electro-optical phase modulator phase modulates the pulsed light signal output by the intensity modulator.

[0009] According to the seed laser for implementing optical path control provided by the present invention, the seed laser also includes: a power preamplifier; an electro-optical phase modulator is connected to the power preamplifier, and the pulse light signal output by the electro-optical phase modulator is output after power amplification by the power preamplifier.

[0010] In a second aspect, the present invention further provides a fiber laser coherent combining system, comprising: a seed laser, wherein the seed laser is any one of the seed lasers for implementing optical path control described above.

[0011] According to the fiber laser coherent combining system provided by the present invention, the system further comprises: a beam splitter, a phase modulator array, a fiber delay line array, an amplifier array, a laser output end cap array, a beam combining device, a plurality of beam splitters, a spot analyzer, an output end photodetector, an oscilloscope, a phase controller, and a dynamic fiber delay line controller;

[0012] The output end of the seed laser is connected to a beam splitter, which splits the seed laser into N beams;

[0013] The phase modulator array includes N phase modulators, the fiber delay line array includes N fiber delay lines, the amplifier array includes N fiber laser amplification links, and the laser output end cap array includes N fiber end caps. Each unit beam output by the beam splitter is connected to a phase modulator, a fiber delay line, a fiber laser amplification link, and a fiber end cap. Each fiber delay line is connected to a dynamic fiber delay line controller, which controls the optical path by controlling the fiber delay line.

[0014] Each unit beam output by the beam splitter undergoes phase modulation by the corresponding phase modulator, optical path control by the fiber delay line, power amplification by the fiber laser amplifier link, and then output to the beam combiner through the fiber end cap. The beam combiner combines the N unit beams and outputs them.

[0015] The laser beam output by the beam combining device is split by multiple beam splitters. A portion of the split laser beam is transmitted to a spot analyzer for observing the far-field spot and evaluating the coherent combining effect. A portion of the split laser beam is transmitted to the output end photodetector. The signal detected by the output end photodetector is transmitted to an oscilloscope and a phase controller.

[0016] The phase controller is connected to each phase modulator in the phase modulator array and is used to control the phase of each unit light beam.

[0017] According to the fiber laser coherent combining system provided by the present invention, the multiple beam splitters include: a first beam splitter and a second beam splitter; the laser output by the beam combining device is split by the first beam splitter, wherein a part of the laser is output to the free space, and a part of the laser is incident on the second beam splitter and split by the second beam splitter; the second beam splitter splits a part of the laser and transmits it to the spot analyzer, and the second beam splitter splits another part of the laser and transmits it to the output end photoelectric detector.

[0018] The fiber laser coherent combining system provided by the present invention further includes: a lens arranged between the second beam splitter and the spot analyzer; the second beam splitter splits a portion of the laser beam and transmits it to the spot analyzer through the lens.

[0019] The present invention proposes a seed laser for implementing optical path control, which is mainly composed of a picosecond pulse source, a high-speed photodetector, an intensity modulator and a single-frequency laser. Based on the seed laser for optical path control of the fiber laser coherent combining system, the optical path difference measurement of the fiber laser coherent combining system is implemented, and combined with the energy transfer fiber fusion optical path compensation and the dynamic fiber delay line optical path compensation, the goal of fine adjustment of the optical path of each fiber laser link in the coherent combining system can be achieved. When implementing optical path adjustment, the significant advantage of the seed laser is that the center wavelength of the picosecond pulse source does not need to be consistent with the center wavelength of the single-frequency seed laser in the coherent combining system, that is, a high-performance picosecond pulse source can be used for multiple high-power coherent combining systems with different center wavelengths. The construction, operation and dismantling of the present invention are simple and easy to operate, and have very little impact on the structure of the coherent combining system, which will greatly save experimental costs and improve experimental efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 1 is a schematic structural diagram of a seed laser for implementing optical path control in an embodiment;

[0022] Figure 2 is a schematic structural diagram of a fiber laser coherent combining system in one embodiment;

[0023] Figure 3 This is a structural diagram of a seed laser based on single-frequency phase modulation provided by an embodiment;

[0024] Figure 4 is a schematic structural diagram of a laser for implementing optical path control in one embodiment;

[0025] Wherein, the accompanying drawings are marked as follows:

[0026] 1: Picosecond pulse source; 2: High-speed photodetector; 3: Single-frequency laser; 4: Intensity modulator; 5: Electro-optical phase modulator; 6: Modulation signal source; 7: RF signal amplifier; 8: Power pre-amplifier; 9: Single-frequency seed laser;

[0027] 1-1: seed laser; 1-2: beam splitter; 1-3: phase modulator array; 1-4: fiber delay line array; 1-5: amplifier array; 1-6: laser output end cap array; 1-7: beam combiner; 1-8: first beam splitter; 1-9: second beam splitter; 1-10: lens; 1-11: spot analyzer; 1-12: output photodetector; 1-13: oscilloscope; 1-14: phase controller; 1-15: dynamic fiber delay line controller. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0029] It should be noted that, in the description of the embodiments of the present invention, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or also includes elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0030] The terms "first," "second," and the like in this application are used to distinguish similar objects, and are not used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in orders other than those illustrated or described herein. Furthermore, the objects distinguished by "first," "second," and the like generally refer to a class of objects and do not limit the number of objects. For example, the first object may be one or more.

[0031] Reference Figure 1 As an optional embodiment, a seed laser for implementing optical path control is provided, comprising a picosecond pulse source 1, a high-speed photodetector 2, an intensity modulator 4, a single-frequency laser 3, and a phase modulation unit;

[0032] The output fiber pigtail of the picosecond pulse source 1 is connected to the high-speed photodetector 2, and the single-frequency laser 3 is connected to the intensity modulator 4. The high-speed photodetector 2 converts the detected pulse light signal into a pulse electrical signal and loads it into the intensity modulator 4. The intensity modulator 4 modulates the intensity of the output laser of the single-frequency laser 3 to convert it into a pulse light signal.

[0033] The intensity modulator 4 is connected to the phase modulation unit, and the phase modulation unit performs phase modulation on the pulse light signal output by the intensity modulator 4 and then outputs the phase modulated signal.

[0034] Furthermore, the phase modulation unit includes a modulation signal source 6, a radio frequency signal amplifier 7, and an electro-optical phase modulator 5;

[0035] The modulation signal source 6 is connected to the RF signal amplifier 7, which amplifies the modulation signal output by the modulation signal source 6 and loads it to the electro-optical phase modulator 5; the intensity modulator 4 is connected to the electro-optical phase modulator 5, which phase modulates the pulse light signal output by the intensity modulator 4.

[0036] Furthermore, the seed laser further includes a power preamplifier 8 , the electro-optical phase modulator 5 is connected to the power preamplifier 8 , and the pulse light signal output by the electro-optical phase modulator 5 is amplified by the power preamplifier 8 and then output.

[0037] The basic principle of the fiber laser coherent combining system is to divide the same seed laser into N sub-beams, which respectively enter N fiber laser transmission links for phase modulation, optical path control, and power amplification in the power amplifier link. The output beams of the N fiber laser transmission links are then spatially spliced ​​through a beam combining device, and by precisely controlling parameters such as the phase and optical path of each beam, the purpose of high-brightness synthetic laser output is achieved.

[0038] Specifically, see Figure 2 , a fiber laser coherent combining system, including a seed laser 1-1, a beam splitter 1-2, a phase modulator array 1-3, a fiber delay line array 1-4, an amplifier array 1-5, a laser output end cap array 1-6, a beam combining device 1-7, a first beam splitter 1-8, a second beam splitter 1-9, a lens 1-10, a spot analyzer 1-11, an output end photodetector 1-12, an oscilloscope 1-13, a phase controller 1-14, and a dynamic fiber delay line controller 1-15;

[0039] The output end of the seed laser 1-1 is connected to the beam splitter 1-2, which splits the seed laser into N beams;

[0040] The phase modulator array 1-3 includes N phase modulators, the fiber delay line array 1-4 includes N fiber delay lines, and the amplifier array 1-5 includes N fiber laser amplification links; the laser output end cap array 1-6 includes N fiber end caps; each unit light beam output by the beam splitter 1-2 is connected to a phase modulator, a fiber delay line, a fiber laser amplification link, and a fiber end cap, and each fiber delay line is connected to a dynamic fiber delay line controller 1-15, which controls the optical path by controlling the fiber delay line;

[0041] Each unit beam output by the beam splitter 1-2 undergoes phase modulation by the corresponding phase modulator, optical path control by the fiber delay line, power amplification by the fiber laser amplifier link, and then output to the beam combiner 1-7 through the fiber end cap. The beam combiner 1-7 combines the N unit beams and outputs the combined beams.

[0042] The laser beam output by the beam combiner 1-7 is split by a plurality of beam splitters. A portion of the split laser beam is transmitted to a spot analyzer 1-11 for observing the far-field spot and evaluating the coherent combining effect. A portion of the split laser beam is transmitted to an output-end photodetector 1-12. The signal detected by the output-end photodetector is transmitted to an oscilloscope 1-13 and a phase controller 1-14.

[0043] The phase controller 1-14 is connected to each phase modulator in the phase modulator array 1-3 and is used to control the phase of each unit light beam.

[0044] Optionally, the plurality of beam splitters include: a first beam splitter 1-8 and a second beam splitter 1-9;

[0045] The laser output by the beam combining device 1-7 passes through the first beam splitter 1-8, and the laser output by the beam combining device 1-7 is split by the first beam splitter 1-8, wherein most of the main laser power is output to the free space, and a small part of the laser power is incident on the second beam splitter 1-9, and is split by the second beam splitter 1-9. A part of the laser beam split by the second beam splitter 1-9 is transmitted to the spot analyzer 1-11 after passing through the lens 1-10 for observing the far-field spot and evaluating the coherent combination effect. A part of the laser beam split by the second beam splitter 1-9 is transmitted to the output end photodetector 1-12, and the signal detected by the output end photodetector 1-12 is transmitted to the oscilloscope 1-13 and the phase controller 1-14. The phase controller 1-14 is connected to each phase modulator in the phase modulator array 1-3 for controlling the phase of each unit light beam.

[0046] For the active phase control system, the output end photodetector 1-12 converts the detected optical signal into an electrical signal, and the phase controller 1-14 is used to achieve phase locking of each laser in the system. There are many methods for active phase control, which will not be introduced in the present invention.

[0047] Reference Figure 3 , a structural diagram of a seed laser based on single-frequency phase modulation provided by an embodiment, Figure 2 The seed laser originally used Figure 3 The seed laser based on single-frequency phase modulation shown in the figure includes a single-frequency seed laser 9, a modulation signal source 6, a radio frequency signal amplifier 7, an electro-optical phase modulator 5 and a power pre-amplifier 8. The phase modulation unit includes a modulation signal source 6, a radio frequency signal amplifier 7 and an electro-optical phase modulator 5. The modulation signal source 6 is connected to the radio frequency signal amplifier 7, and the radio frequency signal amplifier 7 amplifies the modulation signal output by the modulation signal source 6 and then loads it to the electro-optical phase modulator 5. The seed laser output by the single-frequency seed laser 9 passes through the electro-optical phase modulator 5 and the power pre-amplifier 8 and enters the beam splitter 1-2. Figure 2 The fiber laser coherent combining system shown.

[0048] exist Figure 2 When the fiber laser coherent combining system shown in the figure is used for optical path control, Figure 2 The seed laser 1-1 in the CMOS (using a single-frequency seed laser) is replaced by Figure 4 Picosecond pulse source 1 is shown. Figure 4 , Figure 4 The structure diagram of the laser for implementing optical path control in an embodiment includes a picosecond pulse source 1, a modulation signal source 6, a radio frequency signal amplifier 7, and an electro-optical phase modulator 5. The radio frequency signal amplifier 7 amplifies the modulation signal output by the modulation signal source 6 and then loads it to the electro-optical phase modulator 5. Figure 2 The central wavelength of the single-frequency seed laser used by Zhongyuan is the same. The picosecond pulse source 1 passes through the electro-optical phase modulator 5 and the power pre-amplifier 8 and enters the beam splitter 1-2. Figure 2 The fiber laser coherent combining system shown in the figure. The specific process of optical path control is as follows: Figure 2 The output end photodetector 1-12 converts the detected optical signal into an electrical signal. After the electrical signal is analyzed and processed by the oscilloscope 1-13, the transmission time delay Δτ of the other N-1 fiber laser transmission links is obtained based on the fiber laser link with the longest optical path in the fiber laser coherent combining system. Then, the optical path of each laser in the fiber laser coherent combining system is precisely controlled by combining the coarse optical path adjustment of the fused energy transfer fiber and the fine adjustment of the dynamic fiber delay line controller 1-15.

[0049] However, for the construction and verification test of the actual synthetic system, Figure 3 When the central wavelength of the picosecond pulse source in the system is inconsistent with that of the single-frequency seed laser, the picosecond pulse source signal cannot be transmitted in the fiber laser amplification link of the system due to the filtering and isolation effect of the narrow linewidth fiber device in the fiber laser link. In order to achieve the purpose of optical path adjustment, the only option is to replace the picosecond pulse source or use a wavelength tunable picosecond pulse source, which increases the experimental test cost. To this end, the present invention proposes the following method: Figure 1 The wavelength shown can be flexibly switched for Figure 2 The fiber laser coherent combining system shown here uses a seed laser for optical path length control.

[0050] based on Figure 2 The fiber laser coherent combining system shown in Figure 1 The seed laser shown for implementing optical path control can be applied to the fiber laser coherent combining system. When implementing optical path control, the fiber laser coherent combining system has a significant advantage in that the center wavelength of the picosecond pulse source does not need to be consistent with the center wavelength of the single-frequency seed laser in the coherent combining system, that is, one picosecond pulse source can be used for multiple coherent combining systems with different center wavelengths.

[0051] In one embodiment, a fiber laser coherent combining system is provided, the structure of which is shown in FIG. Figure 2 As shown, the seed laser 1-1 adopts Figure 1 The optical path measurement and control process of the fiber laser coherent combining system is as follows: Figure 3 As shown in FIG, the single-frequency seed laser in the fiber laser coherent combining system is replaced with a picosecond pulse source. Figure 1 The seed laser shown is a picosecond pulse source output laser that is directly connected to a high-speed photodetector through a pigtail. The high-speed photodetector converts the detected pulse light signal into a pulse electrical signal and loads it into an intensity modulator. The intensity modulator then modulates the intensity of the single-frequency laser to convert it into a pulse light signal, which then enters the beam splitter 1-2. Figure 2The fiber laser coherent combining system shown in the figure detects the laser signal output from the beam combining end to obtain the transmission delay time Δτ between the other (N-1) fiber lasers and the reference laser link, and uses this as a basis for precise optical path control. A significant advantage of this solution is that the center wavelength of the picosecond pulse source does not need to be consistent with the center wavelength of the single-frequency seed laser in the original fiber laser coherent combining system. That is, a high-performance picosecond pulse source can be used for multiple high-power coherent combining systems with different center wavelengths, achieving the goal of flexibly adjusting the optical path of fiber laser coherent combining systems with different seed laser center wavelengths. In addition, the optical path adjustment device has very little impact on the existing system structure during construction, operation, and dismantling, which will greatly save experimental costs and improve experimental efficiency.

[0052] based on Figure 1 The process of fine optical path control of the fiber laser coherent combining system using the seed laser for optical path control is as follows:

[0053] Step 1: Figure 1 Seed laser replacement for optical path control shown Figure 2 The seed laser of the fiber laser coherent combining system shown.

[0054] Step 2: Connect the picosecond pulse source output laser directly to the high-speed photodetector through the pigtail. The high-speed photodetector converts the detected pulse light signal into a pulse electrical signal and loads it into the intensity modulator. The intensity modulator then modulates the intensity of the single-frequency laser to convert it into a pulse light signal. The phase-modulated pulse light signal enters the power pre-amplifier for power amplification. The power-amplified pulse light signal enters the beam splitter through the beam splitter. Figure 2 The fiber laser coherent combining system shown.

[0055] Step 3: In Figure 2 At the combined laser output end of the fiber laser coherent combining system shown, the output end photodetector 1-12 converts the combined output optical signal into an electrical signal. After analyzing and processing the electrical signal using an oscilloscope, the fiber laser link with the longest optical path in the coherent combining system is determined based on the signal transmission time. Taking the fiber laser link with the longest optical path as a benchmark, the transmission time delay Δτ of the other N-1 fiber laser links compared with it is obtained.

[0056] Step 4: According to the formula L = cΔτ / n, first calculate the energy transfer fiber length L that needs to be compensated for the other N-1 fiber laser links, where c represents the propagation speed of light in a vacuum and n represents the refractive index of the fiber core. Then, in the other N-1 fiber laser links, a power transfer fiber with a length of L = cΔτ / n is fused. This method can compensate the optical path difference between each light beam to 1-2 cm, so that the optical path between each fiber laser link in the fiber laser coherent combining system is basically matched.

[0057] Step 5: Based on the fourth step, a dynamic fiber delay line controller is used to adjust the fiber delay lines on each fiber laser transmission link to further fine-tune the optical path of each laser. Currently, the control accuracy of commercial fiber delay lines can reach 0.1ps, and the coherence between each light beam is adjusted to the optimal state as much as possible, thereby maintaining efficient coherent synthesis laser output.

[0058] Matters not covered by the present invention are known technologies.

[0059] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The above-described embodiments merely represent several embodiments of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements are all within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

[0061] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A seed laser for implementing optical path control, characterized in that: include: Picosecond pulse source, high-speed photodetector, intensity modulator, single-frequency laser, phase modulation unit; The output fiber pigtail of the picosecond pulse source is connected to a high-speed photodetector, which converts the detected pulse light signal into a pulse electrical signal and loads it into an intensity modulator. The intensity modulator is connected to the single-frequency laser, and the intensity modulator modulates the intensity of the laser output by the single-frequency laser to convert the laser into a pulsed light signal; The phase modulation unit is connected to the intensity modulator, and the phase modulation unit performs phase modulation on the pulse light signal output by the intensity modulator and then outputs the phase modulated signal.

2. The seed laser for implementing optical path control according to claim 1, characterized in that: The phase modulation unit includes a modulation signal source, a radio frequency signal amplifier, and an electro-optical phase modulator; The modulation signal source is connected to the radio frequency signal amplifier, which amplifies the modulation signal output by the modulation signal source and then loads it into the electro-optical phase modulator; The intensity modulator is connected to the electro-optical phase modulator, and the electro-optical phase modulator performs phase modulation on the pulse light signal output by the intensity modulator.

3. The seed laser for implementing optical path control according to claim 2, characterized in that: The seed laser further comprises: a power pre-amplifier; The electro-optical phase modulator is connected to the power pre-amplifier, and the pulse optical signal output by the electro-optical phase modulator is output after being power-amplified by the power pre-amplifier.

4. A fiber laser coherent combining system, characterized in that: The invention comprises a seed laser, wherein the seed laser is the seed laser for implementing optical path control according to any one of claims 1 to 3.

5. The fiber laser coherent combining system according to claim 4, characterized in that: The system further comprises: a beam splitter, a phase modulator array, an optical fiber delay line array, an amplifier array, a laser output end cap array, a beam combining device, a plurality of beam splitters, a spot analyzer, an output end photodetector, an oscilloscope, a phase controller, and a dynamic optical fiber delay line controller; The output end of the seed laser is connected to a beam splitter, which splits the seed laser into N beams; The phase modulator array includes N phase modulators, the fiber delay line array includes N fiber delay lines, the amplifier array includes N fiber laser amplification links, and the laser output end cap array includes N fiber end caps. Each unit beam output by the beam splitter is connected to a phase modulator, a fiber delay line, a fiber laser amplification link, and a fiber end cap. Each fiber delay line is connected to a dynamic fiber delay line controller, which controls the optical path by controlling the fiber delay line. Each unit beam output by the beam splitter undergoes phase modulation by the corresponding phase modulator, optical path control by the fiber delay line, power amplification by the fiber laser amplifier link, and then output to the beam combiner through the fiber end cap. The beam combiner combines the N unit beams and outputs them. The laser beam output by the beam combining device is split by multiple beam splitters. A portion of the split laser beam is transmitted to a spot analyzer for observing the far-field spot and evaluating the coherent combining effect. A portion of the split laser beam is transmitted to the output end photodetector. The signal detected by the output end photodetector is transmitted to an oscilloscope and a phase controller. The phase controller is connected to each phase modulator in the phase modulator array and is used to control the phase of each unit light beam.

6. The fiber laser coherent combining system according to claim 5, characterized in that: The plurality of beam splitters include: a first beam splitter and a second beam splitter; The laser beam outputted by the beam combining device is split by the first beam splitter, wherein a portion of the laser beam is outputted into free space, and a portion of the laser beam is incident on the second beam splitter and is split by the second beam splitter; The second beam splitter splits a part of the laser beam and transmits it to the spot analyzer, and the second beam splitter splits another part of the laser beam and transmits it to the output end photoelectric detector.

7. The fiber laser coherent combining system according to claim 6, characterized in that: Also includes: a lens disposed between the second beam splitter and the spot analyzer; The second beam splitter splits a portion of the laser light and transmits it to the spot analyzer through a lens.

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