Broadband all-fiber femtosecond laser system based on chirped pulse amplification and its modulation method

Abstract

This invention discloses a broadband all-fiber femtosecond laser system based on chirped pulse amplification and its adjustment method. The broadband all-fiber femtosecond laser system includes a broadband dissipative soliton mode-locked fiber laser and an all-fiber chirped pulse amplifier connected together. The broadband dissipative soliton mode-locked fiber laser includes a first pump source, a first wavelength division multiplexer, a first gain fiber, a first polarization controller, a polarization-dependent isolator, a second polarization controller, and a coupler. The all-fiber chirped pulse amplifier includes a first polarization-independent isolator, a dispersion-compensating fiber, a second wavelength division multiplexer, a second gain fiber, a third wavelength division multiplexer, a single-mode fiber, a second polarization-independent isolator, a second pump source, and a third pump source. The system achieves broadband characteristics through fiber length adjustment, spectral adjustment, and micro-adjustment modules. This invention has a simple structure, wide application scenarios, pulse distortion resistance, broad spectrum, and strong anti-interference capability.

Description

Technical Field

[0001] This invention relates to lasers and their control technology, and more particularly to a broadband all-fiber femtosecond laser system based on chirped pulse amplification and its modulation method. Background Technology

[0002] Fiber lasers have become essential tools in the field of ultrafast photonics due to their advantages such as small size, low cost, good heat dissipation, and high energy conversion efficiency. They play a crucial role in fields such as thermal imaging, spectroscopy, communications, sensing, medicine, materials processing, environmental monitoring, and the military, especially in applications requiring high temporal resolution and precise control. Through mode-locking techniques, these lasers can generate ultrashort laser pulses with pulse widths in the picosecond or femtosecond range, thereby significantly improving the performance and functionality of lasers in these applications.

[0003] Mode-locking can be achieved through active mode-locking, passive mode-locking, and hybrid mode-locking. Among these, passively mode-locked fiber lasers based on nonlinear polarization rotation (NPR) are widely used in supercontinuum, optical frequency combs, optical sampling systems, and other fields due to their advantages such as compact structure, good stability, ease of operation, and self-starting capability. In the positive dispersion region, nonlinear effects, dispersion, loss, and gain interact to form dissipative soliton pulses; compared to traditional soliton pulses, dissipative soliton pulses can achieve higher peak power after compression. These advantages of passively mode-locked dissipative soliton pulses have broad applications in optics, general physics, biology, and medicine. However, the 3dB spectral width of current 1550nm dissipative soliton lasers is generally 35nm or less, resulting in a narrow spectrum and easy pulse distortion.

[0004] In addition, in some scenarios, after generating an ultrashort laser pulse, it is amplified by an ultrashort optical pulse amplifier. However, the peak intensity of light generated by a traditional ultrashort optical pulse amplifier is very high, which may produce harmful nonlinear pulse distortion, or even damage the gain medium or other optical components. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide a broadband all-fiber femtosecond laser system based on chirped pulse amplification and its modulation method, which has a simple structure, wide application scenarios, less pulse distortion, wide spectrum, and strong anti-interference ability.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A broadband all-fiber femtosecond laser system based on chirped pulse amplification includes a broadband dissipative soliton mode-locked fiber laser and an all-fiber chirped pulse amplifier connected in series. The broadband dissipative soliton mode-locked fiber laser includes a first pump source, a first wavelength division multiplexer, a first gain fiber, a first polarization controller, a polarization-dependent isolator, a second polarization controller, and a coupler. The first pump source, first wavelength division multiplexer, first gain fiber, first polarization controller, polarization-dependent isolator, second polarization controller, and coupler are sequentially connected. The coupler is also connected to a second... A wavelength division multiplexer; the all-fiber chirped pulse amplifier includes a first polarization-independent isolator, a dispersion-compensating fiber, a second wavelength division multiplexer, a second gain fiber, a third wavelength division multiplexer, a single-mode fiber, a second polarization-independent isolator, a second pump source, and a third pump source. The first polarization-independent isolator, the dispersion-compensating fiber, the second wavelength division multiplexer, the second gain fiber, the third wavelength division multiplexer, the single-mode fiber, and the second polarization-independent isolator are connected in sequence. The second pump source is connected to the second wavelength division multiplexer, and the third pump source is connected to the third wavelength division multiplexer.

[0008] A method for regulating the aforementioned broadband all-fiber femtosecond laser system based on chirped pulse amplification includes:

[0009] Adjust the pump power of the first pump source to 90mW±5mW, and adjust the power of the second and third pump sources to change the system amplification factor;

[0010] Adjusting the length of the first gain fiber enables the broadband dissipative soliton mode-locked fiber laser to perform ordinary narrow-spectrum dissipative soliton mode-locking.

[0011] Adjust the first polarization controller to find the broadband trapezoidal spectrum and the Q-switch state spectrum;

[0012] Fine-tuning the first and second polarization controllers causes the spectrum to change slightly between the Q-switched state and the broadband trapezoidal spectrum, and gradually stabilizes to the broadband dissipative soliton spectrum state. At this point, the first and second polarization controllers are fixed, thereby stabilizing the broadband dissipative soliton mode-locked fiber laser to the broadband dissipative soliton mode-locked state.

[0013] A modulation system for the aforementioned broadband all-fiber femtosecond laser system based on chirped pulse amplification includes:

[0014] The power adjustment module is used to adjust the pump power of the first pump source to 90mW±5mW, and to adjust the power of the second and third pump sources to change the system amplification factor.

[0015] The fiber length adjustment module is used to adjust the length of the first gain fiber so that the broadband dissipative soliton mode-locked fiber laser can perform ordinary narrow-spectrum dissipative soliton mode-locking.

[0016] The spectral adjustment module is used to adjust the first polarization controller to find the broadband trapezoidal spectrum and the Q-switch state spectrum;

[0017] The micro-adjustment module is used to fine-tune the first polarization controller and the second polarization controller, so that the spectrum changes slightly between the Q-switched state and the broadband trapezoidal spectrum, and gradually stabilizes to the broadband dissipative soliton spectrum state. At this time, the first polarization controller and the second polarization controller are fixed, thereby stabilizing the broadband dissipative soliton mode-locked fiber laser to the broadband dissipative soliton mode-locked state.

[0018] Compared with existing technologies, the advantages of this invention are as follows: This invention utilizes the NPR passive mode-locking principle to achieve stable, wide-spectrum, power-tunable dissipative soliton mode-locked pulse output. This fiber laser can output high-energy femtosecond pulses with adjustable energy over a wide spectral range, with a spectral width of up to 49.77 nm, a power of up to 140.06 mW, and a pulse width that can be compressed to one-third of the original, reaching 791.3 fs. It can serve as a high-brightness, high-energy, long-lifetime light source and as a pump source for erbium-doped amplifiers. The wide spectral range allows the laser to adapt to different application requirements, improving the flexibility and functionality of the equipment. This fiber laser also boasts advantages such as high stability, strong anti-interference capability, simple structure, flexible and adjustable amplification, and stable mode-locked operation, with a power amplification factor of up to 70 times. It is expected to find wide application in optical communication, optical sensing, and optical detection fields. Attached Figure Description

[0019] Figure 1 This is a structural diagram of the broadband all-fiber femtosecond laser system based on chirped pulse amplification provided by the present invention;

[0020] Figure 2 This is the test spectrum of the wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification provided by the present invention at port a;

[0021] Figure 3 This is a test repetition frequency diagram of the wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification provided by the present invention at port a;

[0022] Figure 4 This is the test autocorrelation trajectory diagram of the wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification provided by the present invention at port a;

[0023] Figure 5 This is a test spectrum diagram of the wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification provided by the present invention at port a;

[0024] Figure 6 The test autocorrelation trajectory of the wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification provided by this invention at port b;

[0025] Figure 7 The test autocorrelation trajectory of the wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification provided by this invention at the c-port. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0027] Example 1

[0028] This invention provides a broadband all-fiber femtosecond laser system based on chirped pulse amplification, such as... Figure 1 As shown, the system includes a broadband dissipative soliton mode-locked fiber laser and an all-fiber chirped pulse amplifier connected together. The broadband dissipative soliton mode-locked fiber laser includes a first pump source 1, a first wavelength division multiplexer 2, a first gain fiber 3, a first polarization controller 4, a polarization-dependent isolator 5, a second polarization controller 6, and a coupler 7. The first pump source 1, the first wavelength division multiplexer 2, the first gain fiber 3, the first polarization controller 4, the polarization-dependent isolator 5, the second polarization controller 6, and the coupler 7 are connected sequentially. The coupler 7 is also connected to the first wavelength division multiplexer 2. The output port of the broadband dissipative soliton mode-locked fiber laser is port a. The all-fiber chirped pulse amplifier includes a first polarization-independent isolator 8, a dispersion-compensating fiber 9, a second wavelength division multiplexer 10, a second gain fiber 11, a third wavelength division multiplexer 12, a single-mode fiber 13, a second polarization-independent isolator 14, a second pump source 15, and a third pump source 16. The first polarization-independent isolator 8, the dispersion-compensating fiber 9, the second wavelength division multiplexer 10, the second gain fiber 11, the third wavelength division multiplexer 12, the single-mode fiber 13, and the second polarization-independent isolator 14 are connected in sequence. The second pump source 15 is connected to the second wavelength division multiplexer 10, and the third pump source 16 is connected to the third wavelength division multiplexer 12.

[0029] The broadband dissipative soliton mode-locked fiber laser is specifically a fiber ring cavity. Coupler 7 has a first output port and a second output port, with an output power ratio of 20%:80% between the first and second output ports. The first output port is connected to the input port of the first polarization-independent isolator 8 of the all-fiber chirped pulse amplifier, and the second output port is connected to the input port of the first wavelength division multiplexer 3. The first pump source 1 provides pump light to the fiber ring cavity. The optical signal output from the first wavelength division multiplexer 2 passes sequentially through the first gain fiber 3, the first polarization controller 4, the polarization-dependent isolator 5, the second polarization controller 6, and the coupler 7 to generate broadband dissipative soliton pulses. Finally, 80% of the broadband dissipative soliton pulses are input to the first wavelength division multiplexer 2, and the remaining 20% ​​are input to the all-fiber chirped pulse amplifier.

[0030] The all-fiber chirped pulse amplifier features an all-fiber bidirectional pump structure. It utilizes optical pulse chirped amplification technology, employing dispersion-compensating fiber 9 to broaden 20% wide-spectrum dissipative soliton pulses, a second gain fiber 11 for power amplification, and single-mode fiber 13 for pulse compression, ultimately yielding a high-power, adjustable, and stable femtosecond pulse output. The single-mode fiber 13 and the second polarization-independent isolator 14 enable pulse width compression.

[0031] The components of the broadband dissipative soliton mode-locked fiber laser are connected via optical fibers, specifically single-mode fibers operating in the 1550nm wavelength range. Similarly, the components of the all-fiber chirped pulse amplifier are connected via optical fibers, also operating in the 1550nm wavelength range. Coupler 7 and the first polarization-independent isolator 8 are connected via optical fibers, again operating in the 1550nm wavelength range. Both the first polarization controller 4 and the second polarization controller 6 are squeeze-type polarization controllers. The input and output pigtails of the first wavelength division multiplexer 2, the first polarization controller 4, the polarization-dependent isolator 5, the second polarization controller 6, the coupler 7, the first polarization-independent isolator 8, the second wavelength division multiplexer 10, the third wavelength division multiplexer 12, the second polarization-independent isolator 14, the second pump source 15, and the third pump source 16 are all single-mode optical fibers in the 1550nm band. The output pigtails of the first pump source 1, the second pump source 15, and the third pump source 16 are all single-mode optical fibers in the 1550nm band. The dispersion compensation fiber 9 operates at a wavelength of 1550nm. The operating wavelengths of the first pump source 1, the second pump source 15, and the third pump source 16 are all 980nm. The operating wavelengths of the first wavelength division multiplexer 2, the second wavelength division multiplexer 10, and the third wavelength division multiplexer 12 are all 980 / 1550nm.

[0032] Example 2

[0033] This invention provides a method for regulating a broadband all-fiber femtosecond laser system based on chirped pulse amplification, comprising:

[0034] Adjust the pump power of the first pump source to 90mW±5mW, and adjust the power of the second and third pump sources to change the system amplification factor;

[0035] Adjusting the length of the first gain fiber enables the broadband dissipative soliton mode-locked fiber laser to perform ordinary narrow-spectrum dissipative soliton mode-locking.

[0036] Adjust the first polarization controller to find the broadband trapezoidal spectrum and the Q-switching state spectrum; the broadband trapezoidal spectrum can be found in the article "Partially polarized wave-breaking-free dissipative soliton with super-broad spectrum in a mode-locked fiber laser" published in Laser Physics Letters 8(2) 2011, pp. 134-138; the Q-switching state spectrum can be found in the article "Revealing the transition dynamics from Q switching to mode locking in asoliton laser" published in Physical Review Letters 123(9):093901 2019.

[0037] Fine-tuning the first and second polarization controllers causes the spectrum to change slightly between the Q-switched state and the broadband trapezoidal spectrum, and gradually stabilizes to the broadband dissipative soliton spectrum state. At this point, the first and second polarization controllers are fixed, thereby stabilizing the broadband dissipative soliton mode-locked fiber laser to the broadband dissipative soliton mode-locked state.

[0038] Example 3

[0039] This invention provides a modulation system for a broadband all-fiber femtosecond laser system based on chirped pulse amplification, comprising:

[0040] The power adjustment module is used to adjust the pump power of the first pump source to 90mW±5mW, and to adjust the power of the second and third pump sources to change the system amplification factor.

[0041] The fiber length adjustment module is used to adjust the length of the first gain fiber so that the broadband dissipative soliton mode-locked fiber laser can perform ordinary narrow-spectrum dissipative soliton mode-locking.

[0042] The spectral adjustment module is used to adjust the first polarization controller to find the broadband trapezoidal spectrum and the Q-switch state spectrum;

[0043] The micro-adjustment module is used to fine-tune the first polarization controller and the second polarization controller, so that the spectrum changes slightly between the Q-switched state and the broadband trapezoidal spectrum, and gradually stabilizes to the broadband dissipative soliton spectrum state. At this time, the first polarization controller and the second polarization controller are fixed, thereby stabilizing the broadband dissipative soliton mode-locked fiber laser to the broadband dissipative soliton mode-locked state.

[0044] Experimental results

[0045] like Figure 2 As shown, this is the output spectrum of the broadband dissipative soliton mode-locked fiber laser of the present invention. The broadband dissipative soliton mode-locked fiber laser can establish a self-starting mode-locked state when the pump power is 90mW±5mW. It can be observed that the center wavelength of the pulse is 1556.49nm, the 3dB bandwidth of the pulse spectrum is 49.77nm, and the pulse power is 2mW.

[0046] like Figure 3 As shown, this is a diagram of the output repetition frequency of a broadband dissipative soliton mode-locked fiber laser. The repetition frequency of the output optical signal of the broadband dissipative soliton mode-locked fiber laser is 10.029MHz, the pulse interval is 99.711ns, and the laser is operating in a relatively stable state.

[0047] like Figure 4 As shown, this is the autocorrelation trajectory of the output of a broadband dissipative soliton mode-locked fiber laser. Using Gaussian fitting, its pulse width is 2.1 ps.

[0048] like Figure 5 As shown, it is the output spectrum of a broadband dissipative soliton mode-locked fiber laser. The center frequency of the output optical signal of the broadband dissipative soliton mode-locked fiber laser is 10.029MHz, and the signal-to-noise ratio of the pulse is 57.7dB, indicating that the pulse signal is very stable.

[0049] Figure 6 The autocorrelation trajectory of the output optical pulse from a broadband dissipative soliton mode-locked fiber laser is shown after pulse broadening and power amplification in an all-fiber chirped pulse amplifier. Using Gaussian fitting, the pulse width is found to be 18.39 ps, indicating that the laser output pulse is broadened after passing through the dispersion-compensating fiber.

[0050] Figure 7 The autocorrelation trajectory of the output optical pulse from a broadband dissipative soliton mode-locked fiber laser is shown after pulse broadening, power amplification, and pulse compression in an all-fiber chirped pulse amplifier. Figure 7 The autocorrelation trajectory is shown when the power is amplified to 140.06mW. By using Gaussian fitting, the pulse width is 791.3fs, indicating that the pulse light output by the laser is broadened by the dispersion-compensating fiber and then compressed by the single-mode fiber. The pulse width can be compressed to 1 / 3 of the original pulse light output by the laser, and the power can be amplified to 70 times the original pulse light output by the laser.

[0051] It should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0052] It should be understood that the embodiments and descriptions above are only the principles, main features and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope of the invention, and all such changes and modifications fall within the protection scope of the present invention.

Claims

1. A broadband all-fiber femtosecond laser system based on chirped pulse amplification, characterized in that: The system includes a broadband dissipative soliton mode-locked fiber laser and an all-fiber chirped pulse amplifier connected together. The broadband dissipative soliton mode-locked fiber laser includes a first pump source, a first wavelength division multiplexer (WDM), a first gain fiber, a first polarization controller, a polarization-dependent isolator, a second polarization controller, and a coupler. The first pump source, first WDM, first gain fiber, first polarization controller, polarization-dependent isolator, second polarization controller, and coupler are sequentially connected. The coupler is also connected to the first WDM. The all-fiber chirped pulse amplifier includes a first polarization-independent isolator, a dispersion-compensating fiber, a second WDM, a second gain fiber, a third WDM, a single-mode fiber, a second polarization-independent isolator, a second pump source, and a third pump source. The first polarization-independent isolator, dispersion-compensating fiber, second WDM, second gain fiber, third WDM, single-mode fiber, and second polarization-independent isolator are sequentially connected. The second pump source is connected to the second WDM, and the third pump source is connected to the third WDM.

2. The broadband all-fiber femtosecond laser system based on chirped pulse amplification according to claim 1, characterized in that: The components of the broadband dissipative soliton mode-locked fiber laser are connected by optical fibers, and the optical fibers used are single-mode optical fibers in the 1550nm band.

3. The broadband all-fiber femtosecond laser system based on chirped pulse amplification according to claim 1, characterized in that: The components of the all-fiber chirped pulse amplifier are connected by optical fibers, and the optical fibers used are single-mode optical fibers in the 1550nm band.

4. The broadband all-fiber femtosecond laser system based on chirped pulse amplification according to claim 1, characterized in that: The coupler and the first polarization-independent isolator are connected by an optical fiber, which is a single-mode fiber in the 1550nm band.

5. The broadband all-fiber femtosecond laser system based on chirped pulse amplification according to claim 1, characterized in that: The first wavelength division multiplexer, the first polarization controller, the polarization-dependent isolator, the second polarization controller, the coupler, the first polarization-independent isolator, the second wavelength division multiplexer, the third wavelength division multiplexer, and the second polarization-independent isolator are all single-mode optical fibers with input and output pigtails in the 1550nm band. The output pigtails of the first pump source, the second pump source, and the third pump source are all single-mode optical fibers with output in the 1550nm band. The operating wavelength of the dispersion compensation fiber is 1550nm.

6. The broadband all-fiber femtosecond laser system based on chirped pulse amplification according to claim 1, characterized in that: Both the first polarization controller and the second polarization controller are squeeze-type polarization controllers.

7. The broadband all-fiber femtosecond laser system based on chirped pulse amplification according to claim 1, characterized in that: The coupler has a first output port and a second output port, with an output power ratio of 20%:80% between the first output port and the second output port. The first output port is connected to the input port of the first polarization-independent isolator, and the second output port is connected to the input port of the first wavelength division multiplexer.

8. The broadband all-fiber femtosecond laser system based on chirped pulse amplification according to claim 1, characterized in that: The first pump source, the second pump source, and the third pump source all operate at a wavelength of 980 nm, and the first wavelength division multiplexer, the second wavelength division multiplexer, and the third wavelength division multiplexer all operate at wavelengths of 980 / 1550 nm.

9. A method for adjusting a broadband all-fiber femtosecond laser system based on chirped pulse amplification as described in claim 1, characterized in that, include: Adjust the pump power of the first pump source to 90mW±5mW, and adjust the power of the second and third pump sources to change the system amplification factor; Adjusting the length of the first gain fiber enables the broadband dissipative soliton mode-locked fiber laser to perform ordinary narrow-spectrum dissipative soliton mode-locking. Adjust the first polarization controller to find the broadband trapezoidal spectrum and the Q-switch state spectrum; Fine-tuning the first and second polarization controllers causes the spectrum to change slightly between the Q-switched state and the broadband trapezoidal spectrum, and gradually stabilizes to the broadband dissipative soliton spectrum state. At this point, the first and second polarization controllers are fixed, thereby stabilizing the broadband dissipative soliton mode-locked fiber laser to the broadband dissipative soliton mode-locked state.

10. A modulation system for a broadband all-fiber femtosecond laser system based on chirped pulse amplification as described in claim 1, characterized in that, include: The power adjustment module is used to adjust the pump power of the first pump source to 90mW±5mW, and to adjust the power of the second and third pump sources to change the system amplification factor. The fiber length adjustment module is used to adjust the length of the first gain fiber so that the broadband dissipative soliton mode-locked fiber laser can perform ordinary narrow-spectrum dissipative soliton mode-locking. The spectral adjustment module is used to adjust the first polarization controller to find the broadband trapezoidal spectrum and the Q-switch state spectrum; The micro-adjustment module is used to fine-tune the first polarization controller and the second polarization controller, so that the spectrum changes slightly between the Q-switched state and the broadband trapezoidal spectrum, and gradually stabilizes to the broadband dissipative soliton spectrum state. At this time, the first polarization controller and the second polarization controller are fixed, thereby stabilizing the broadband dissipative soliton mode-locked fiber laser to the broadband dissipative soliton mode-locked state.

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