All-fiber integrated femtosecond laser system based on gain-managed nonlinear amplification

Abstract

The application discloses a kind of based on gain management nonlinear amplification all-optical fiber integration femtosecond laser system, comprising: all-optical fiber ultrashort pulse seed source, all-optical fiber pulse pre-compressor, fiber GMN amplifier and high-power fiber pulse compressor.The all-optical fiber pulse pre-compressor includes circulator, chirped fiber Bragg grating, passive optical fiber.The fiber GMN amplifier includes pump source, wavelength division multiplexer, gain fiber, pump light stripper.A kind of based on gain management nonlinear amplification all-optical fiber integration femtosecond laser system of the application introduces all-optical fiber pulse pre-compressor and high-power fiber pulse compression, the evolution and compression of pulse are all completed in fiber link, without introducing additional free space component, while guaranteeing the femtosecond laser of output high peak power and ultrashort pulse width also takes into account the high environmental stability and compactness, can satisfy the application demand of various complex environment, with wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of laser technology and nonlinear optics, and particularly relates to a full-fiber integrated femtosecond laser system based on gain-managed nonlinear amplification. BACKGROUND

[0002] High-intensity femtosecond lasers have extremely short pulse widths and extremely high peak powers, and thus have significant application requirements in high-precision industrial manufacturing, biological medicine, military aerospace, frontier science and other fields. Among them, femtosecond fiber lasers stand out due to their compact system design, reliable environmental stability and excellent beam quality, and have brought new breakthroughs to the development of these fields.

[0003] At present, the commonly used way to generate femtosecond fiber lasers is mode-locking technology. However, the peak power of the laser directly output by the fiber mode-locked laser is low, which cannot meet the application requirements, and needs to be further amplified by a gain fiber. Direct amplification in the gain fiber is affected by nonlinear effects such as self-phase modulation (SPM) and stimulated Raman scattering (SRS), which limits the improvement of the pulse peak power and causes the pulse quality to decrease. In order to improve the pulse peak power, the most common method for managing nonlinearity is the chirped pulse amplification (CPA) technology, in which the pulse is first stretched in the time domain, then amplified, and finally compressed. However, the dispersion mismatch between the stretcher and the compressor, as well as the inevitable gain narrowing, make it difficult for the compressed pulse width to be within 100 femtoseconds. It is worth noting that many applications require extremely high temporal and spatial resolution as well as significant nonlinear effects, which requires the use of lasers with a pulse width of about 50 fs. Such applications include the generation of attosecond lasers, which won the Nobel Prize in Physics in 2023, high-speed nonlinear optical imaging driven by multiple beams, and the creation of optical frequency combs.

[0004] So far, there are pre-chirp management amplification technology and gain-managed nonlinear (GMN) amplification technology that can realize femtosecond lasers with a pulse width of about 50 fs. However, in the case of pre-chirp management amplification, it is necessary to introduce a partial free-space structure to precisely regulate the dispersion of the seed laser, which increases the complexity of the system and eliminates the advantages of the full-fiber structure. Compared with the pre-chirp management amplification technology, the GMN technology relies on nonlinear attractors, making the temporal distribution of its seed laser insensitive. In addition, the GMN amplification system does not require additional stretching devices, and the system structure is extremely compact. However, the GMN amplification system currently uses a diffraction grating and other free-space structures in its final compression stage. This inevitably introduces a partial free-space structure, which reduces the overall compactness and stability of the system. Therefore, the present application proposes a full-fiber integrated femtosecond laser that can output high peak power with a pulse width of about 50 fs. SUMMARY

[0005] In order to solve the problem that the high peak power femtosecond laser with a pulse width of about 50 fs has more free space components, a large volume, is greatly affected by the environment and is difficult to integrate, the application provides a full-fiber integrated femtosecond laser system based on gain management nonlinear amplification. The seed source, amplifier and compressor of the whole system all adopt a full-fiber structure, which is highly compact and can meet the application requirements in various complex environments. The laser output by the seed source is pre-compressed by a chirped fiber Bragg grating, and then injected into a fiber amplifier for GMN amplification. The amplified pulse laser is compressed by a hollow-core photonic crystal fiber. Finally, a high peak power femtosecond laser output with a pulse width of 50 fs can be realized by using the method. Compared with the traditional femtosecond laser, the method can realize high peak power ultrashort pulse output while maintaining the full-fiber integrated structure, excellent beam quality and high environmental stability.

[0006] In order to achieve the above object, the application adopts the following technical scheme:

[0007] A full-fiber integrated femtosecond laser system based on gain management nonlinear amplification comprises a full-fiber ultrashort pulse seed source, a full-fiber pulse pre-compressor, a fiber GMN amplifier and a high-power fiber pulse compressor. The full-fiber pulse pre-compressor comprises a circulator, a chirped fiber Bragg grating and a passive fiber. The fiber GMN amplifier comprises a pump source, a wavelength division multiplexer, a gain fiber and a pump light stripper. The output end of the full-fiber ultrashort pulse seed source is connected to the input end of the circulator, the reflection end of the circulator is connected to the input end of the chirped fiber Bragg grating, and the output end of the circulator is connected to the passive fiber. The output end of the passive fiber is connected to the pump end of the wavelength division multiplexer, wherein the pump end of the wavelength division multiplexer is connected to the output end of the pump source. The output end of the wavelength division multiplexer is connected to the gain fiber, the pump stripper in sequence, and the output end of the pump stripper is connected to the high-power fiber pulse compressor.

[0008] Preferably, the center wavelength of the full-fiber ultrashort pulse seed source is 1000-1060 nm, the spectral full width at half maximum is 1-80 nm, the pulse width is 0.1-20 ps, the repetition frequency is 1-100 MHz, and the pulse energy is 0.1-10 nJ.

[0009] Preferably, the center wavelength of the chirped fiber Bragg grating is 1000-1060 nm, the spectral full width at half maximum is 10-80 nm, the reflectivity is between 10% and 99%, and the available negative dispersion value β2 is between -0.5 and -5 ps 2 .

[0010] As preferred, the pump source is a semiconductor laser, a solid-state laser, a gas laser, a fiber laser or a Raman laser, the laser type is a continuous laser or a pulsed laser, and the output fiber is a single-mode fiber or a multi-mode fiber.

[0011] As preferred, the pumping mode of the pump source is one of core single-end pumping, core double-end pumping, cladding single-end pumping and cladding double-end pumping.

[0012] As preferred, the gain fiber is a quartz fiber doped with ytterbium (Yb) rare earth ions, and the fiber type can be a single-clad fiber or a double-clad fiber, and the fiber core diameter is between 4-50 μm.

[0013] As preferred, the high-power fiber pulse compressor is an air-core photonic bandgap photonic crystal fiber or an air-core anti-resonant photonic crystal fiber, and the zero dispersion wavelength is between 900-1000 nm.

[0014] As preferred, the fiber devices and the fibers are coupled by fiber fusion.

[0015] Compared with the prior art, the application has the following advantages:

[0016] The application provides a full-fiber integrated femtosecond laser system based on gain-managed nonlinear amplification, and the core devices are a full-fiber pulse pre-compressor and a high-power fiber pulse compressor. The pulse width of a seed source is reduced to less than 2 ps by the full-fiber pulse pre-compressor, so as to provide a full-fiber front-end signal light for a fiber GMN amplifier. The pulse width of the laser output by the GMN amplifier is compressed to about 50 fs by the high-power fiber pulse compressor, and the peak power of the laser can reach a megawatt level.

[0017] The application has the following advantages: the whole system adopts a full-fiber integrated link, and the generation, amplification, GMN evolution and compression of pulses are all completed in the fiber without introducing additional free-space components. Compared with a conventional high-peak-power femtosecond laser, the system can ensure the output of femtosecond laser with high peak power and ultra-short pulse width, and still maintain high system compactness and environmental stability. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 FIG. 1 is a structural schematic diagram of a full-fiber integrated femtosecond laser system based on gain-managed nonlinear amplification according to the application.

[0019] Figure 2 FIG. 2 is a pulse evolution process diagram in different system structures according to the application.

[0020] Wherein, 1. All-fiber ultrashort pulse seed source, 2. Circulator, 3. Chirped fiber Bragg grating, 4. Passive fiber, 5. Pump source, 6. Wavelength division multiplexer, 7. Gain fiber, 8. Pump light stripper, 9. High-power fiber pulse compressor, 10. All-fiber ultrashort pulse seed source pulse profile, 11. All-fiber ultrashort pulse seed source output pulse profile, 12. All-fiber pulse pre-compressor output pulse profile, 13. Fiber GMN amplifier output pulse profile, 14. High-power fiber pulse compressor output pulse profile. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the following will further illustrate the present application by combining with several drawings and embodiments, it should be noted that, in the premise of not conflicting, the following described embodiments or technical features between each can be combined to form a new embodiment. The specific embodiments described here are only used to explain the present application, but not limit the present application.

[0022] As Figure 1 shown, an all-fiber integrated femtosecond laser system based on gain-managed nonlinear amplification includes: all-fiber ultrashort pulse seed source 1, all-fiber pulse pre-compressor 2-4, fiber GMN amplifier 5-8 and high-power fiber pulse compressor 9. The all-fiber pulse pre-compressor includes circulator 2, chirped fiber Bragg grating 3, passive fiber 4. The fiber GMN amplifier includes pump source 5, wavelength division multiplexer 6, gain fiber 7, pump light stripper 8. The output end of the all-fiber ultrashort pulse seed source 1 is connected to the input end of the circulator 2, the reflection end of the circulator 2 is connected to the input end of the chirped fiber Bragg grating 3, and the output end of the circulator 2 is connected to the passive fiber 4. The output end of the passive fiber 4 is connected to the pump end of the wavelength division multiplexer 6, wherein the pump end of the wavelength division multiplexer 6 is connected to the output end of the pump source 5. The output end of the wavelength division multiplexer 6 is connected to the gain fiber 7, the pump stripper 8 in turn, and the output end of the pump stripper 8 is connected to the high-power fiber pulse compressor 9.

[0023] The ultrashort pulses generated by the all-fiber ultrashort pulse seed source 1 are input to the all-fiber pulse pre-compressor 2-4. First, the ultrashort pulses are guided by the circulator 2 into the chirped fiber Bragg grating 3 for compression. The compressed ultrashort pulses are then input into the passive fiber 4 through the output of the circulator 2 to compensate for excessive negative dispersion, ensuring that the laser pulse width output by the all-fiber pulse pre-compressor 2-4 is in the range of hundreds of femtoseconds to several picoseconds. The laser output from the all-fiber pulse pre-compressor 2-4 is then further boosted by the fiber GMN amplifier. Simultaneously, strong nonlinearity and gain-shaping spectral processing are used to shape the pulse spectrum, enabling pulse output with pulse widths of tens of femtoseconds. The pulses output from the fiber GMN amplifier are then fed into the high-power fiber pulse compressor 9 for dispersion compensation, obtaining a high-peak-power femtosecond laser with a pulse width of approximately 50 fs.

[0024] The pulse evolution profile in the entire system is as follows Figure 2 As shown, the all-fiber ultrashort pulse seed source pulse profile 10 is a Gaussian pulse profile with accumulated positive chirp. After passing through the all-fiber pulse pre-compression 2-4, the accumulated positive chirp is compensated, so the output pulse profile 12 of the all-fiber pulse pre-compressor is a Gaussian pulse profile with approximately zero chirp. After passing through the fiber GMN amplifier 5-8, as the GMN amplification evolves, the pulse profile gradually evolves from Gaussian to parabolic and then to asymmetric. Therefore, the output pulse profile 13 of the fiber GMN amplifier is an asymmetric pulse profile with accumulated positive chirp. After passing through the high-power fiber pulse compressor 9, the positive chirp of the pulse is compensated, and finally the output pulse profile of the high-power fiber pulse compressor is a Gaussian pulse profile with approximately zero chirp.

[0025] This invention provides a compact, stable, and all-fiber integrated femtosecond laser capable of achieving ultrashort pulse widths and high peak power. Based on gain-managed nonlinear amplification technology, a complete all-fiber link is achieved using an all-fiber seed source, pre-compressor, amplifier, and main compressor. Compared to traditional femtosecond lasers, this structure has no free-space components, maintaining high environmental stability and compactness while outputting high peak power and ultrashort pulse width femtosecond lasers. It can meet the application requirements of various complex environments and has broad application prospects.

Claims

1. An all-fiber integrated femtosecond laser system based on gain-managed nonlinear amplification, characterized in that, The full-fiber ultrashort pulse seed source, the full-fiber pulse pre-compressor, the fiber GMN amplifier and the high-power fiber pulse compressor are included. The full-fiber pulse pre-compressor comprises a circulator, a chirped fiber Bragg grating and a passive optical fiber. The fiber GMN amplifier comprises a pump source, a wavelength division multiplexer, a gain optical fiber and a pump light stripper. The output end of the all-fiber ultrashort pulse seed source is connected with the input end of the circulator, the reflection end of the circulator is connected with the input end of the chirped fiber Bragg grating, and the output end of the circulator is connected with the passive optical fiber; the output end of the passive optical fiber is connected with the pump end of the wavelength division multiplexer, wherein the pump end of the wavelength division multiplexer is connected to the output end of the pump source; the output end of the wavelength division multiplexer is connected with the gain optical fiber and the pump stripper in sequence, and the output end of the pump stripper is connected to the high-power fiber pulse compressor; the center wavelength of the all-fiber ultrashort pulse seed source is 1000-1060 nm, the full width at half maximum of the spectrum is 1-80 nm, the pulse width is 0.1-20 ps, the repetition frequency is 1-100 MHz, and the pulse energy is 0.1-10 nJ; the center wavelength of the chirped fiber Bragg grating is 1000-1060 nm, the full width at half maximum of the spectrum is 10-80 nm, the reflectivity is between 10% and 99%, and the provided negative dispersion value β2 is between -0.5 and -5 ps 2 ; the pump source is a semiconductor laser, a solid-state laser, a gas laser, a fiber laser or a Raman laser, the laser type is a continuous laser or a pulsed laser, the output optical fiber is a single-mode optical fiber or a multi-mode optical fiber; the pump mode of the pump source is core single-end pumping, core double-end pumping, cladding single-end pumping or cladding double-end pumping; the gain optical fiber is a quartz optical fiber doped with ytterbium and rare earth ions, the optical fiber type is a single-clad optical fiber or a double-clad optical fiber, and the optical fiber core diameter is between 4-50 μm.

2. The all-fiber integrated femtosecond laser system based on gain- managed nonlinear amplification according to claim 1, wherein, The high-power fiber pulse compressor is an air-core photonic bandgap photonic crystal fiber or an air-core anti-resonant photonic crystal fiber, and the zero dispersion wavelength is between 900-1000 nm.

3. The all-fiber integrated femtosecond laser system based on gain- managed nonlinear amplification of claim 1, wherein, The fiber devices and the fibers are coupled by fiber fusion.

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