Broadband spectrum all-fiber femtosecond laser system based on chirped pulse amplification and adjusting method thereof

Abstract

The invention discloses a broadband spectrum all-fiber femtosecond laser system based on chirped pulse amplification and an adjusting method of the broadband spectrum all-fiber femtosecond laser system. The broadband spectrum all-fiber femtosecond laser system comprises a broadband spectrum dissipative soliton mode-locked fiber laser and an all-fiber chirped pulse amplifier which are connected. The broadband spectrum dissipative soliton mode-locked fiber laser comprises a first pumping 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 comprises a first polarization independent isolator, a dispersion compensation 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 pumping source and a third pumping source. The system realizes the wide spectrum characteristic through the optical fiber length adjusting module, the spectrum adjusting module and the fine adjusting module. The device is simple in structure, wide in application scene, not prone to pulse distortion, wide in spectrum and high in anti-interference capacity.

Description

Technical Field

[0001] The invention relates to a laser and a control technology thereof, and in particular to a wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification and an adjustment method thereof. Background Art

[0002] Fiber lasers have become an important tool in the field of ultrafast photonics due to their small size, low cost, good heat dissipation, and high energy conversion efficiency. They play a key role in thermal imaging, spectroscopy, communications, sensing, medical treatment, material processing, environmental monitoring, and military applications, especially in applications that require high temporal resolution and precise control. Through mode locking technology, these lasers can generate ultrashort laser pulses with a pulse width of only picoseconds or femtoseconds, which significantly improves the performance and functionality of lasers in these applications.

[0003] Mode locking can be achieved by active mode locking, passive mode locking and hybrid mode locking. Among them, passive mode-locked fiber lasers based on nonlinear polarization rotation (NPR) are widely used in many fields such as supercontinuum, optical frequency comb, and optical sampling system due to their compact structure, good stability, easy operation, and self-start. In the positive dispersion region, nonlinear effects, dispersion, loss, and gain interact to form dissipative soliton pulses; compared with traditional soliton pulses, dissipative soliton pulses can reach higher peak power after compression. These advantages of passive mode-locked dissipative soliton pulses make them widely used in many fields such as optics, general physics, biology, and medicine. However, the 3dB spectral width of the current 1550nm dissipative soliton laser is generally 35nm or less, the spectrum is narrow, and the pulse is easily distorted.

[0004] In addition, in some scenarios, after the ultrashort laser pulses are generated, they are amplified by ultrashort optical pulse amplifiers. However, the peak intensity of light generated by traditional ultrashort optical pulse amplifiers is very high, which may cause harmful nonlinear pulse distortion and even damage the gain medium or other optical components. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification and its adjustment method, which has a simple structure, wide application scenarios, pulses that are not easily distorted, a wide spectrum, and strong anti-interference ability.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A wide spectrum all-fiber femtosecond laser system based on chirped pulse amplification comprises a wide spectrum dissipative soliton mode-locked fiber laser and an all-fiber chirped pulse amplifier connected to each other, wherein the wide spectrum dissipative soliton mode-locked fiber laser comprises 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, wherein the first pump source, the first wavelength division multiplexer, the first gain fiber, the first polarization controller, the polarization-dependent isolator, the second polarization controller and the coupler are connected in sequence, and the coupler is also connected to the first a wavelength division multiplexer; the all-fiber chirped pulse amplifier comprises a first polarization-independent isolator, a dispersion-compensating optical fiber, a second wavelength division multiplexer, a second gain optical fiber, a third wavelength division multiplexer, a single-mode optical fiber, a second polarization-independent isolator, a second pump source and a third pump source; the first polarization-independent isolator, the dispersion-compensating optical fiber, the second wavelength division multiplexer, the second gain optical fiber, the third wavelength division multiplexer, the single-mode optical 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 adjusting the above-mentioned wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification comprises:

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

[0010] Adjusting the length of the first gain fiber to enable the wide spectrum 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] The first polarization controller and the second polarization controller are fine-tuned to make the spectrum slightly change between the Q-switched state and the broadband trapezoidal spectrum, and gradually stabilize to the broadband dissipative soliton spectrum state. At this time, the first polarization controller and the second polarization controller are fixed to stabilize the broadband dissipative soliton mode-locked fiber laser to the broadband dissipative soliton mode-locked state.

[0013] An adjustment system for the above-mentioned wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification comprises:

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

[0015] An optical fiber length adjustment module, used for adjusting the length of the first gain optical fiber so that the wide spectrum dissipative soliton mode-locked optical fiber laser performs ordinary narrow spectrum dissipative soliton mode-locking;

[0016] A spectrum adjustment module, used for adjusting the first polarization controller to find a broadband trapezoidal spectrum and a Q-switch state spectrum;

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

[0018] Compared with the prior art, the present invention has the following beneficial effects: the present invention utilizes the NPR passive mode-locking principle to realize stable wide-spectrum power-adjustable dissipative soliton mode-locked pulse output. The fiber laser can output high-energy femtosecond pulses with adjustable energy in a wide spectral range, with a spectrum width of up to 49.77nm, a power of up to 140.06mW, and a pulse width that can be compressed to 1 / 3 of the original, up to 791.3fs. It can be used as a high-brightness, high-energy, long-life light source, and can be used as a pump source for erbium-doped amplifiers. The wide spectral range enables the laser to adapt to different application requirements, improving the flexibility and functionality of the equipment; the fiber laser also has the advantages of high stability, strong anti-interference ability, simple structure, flexible and adjustable amplification factor, and stable mode-locked operation, and the power amplification factor can reach 70 times. It is expected to be widely used in the fields of optical communication, optical sensing, and optical detection. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0020] Figure 2 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;

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

[0025] Figure 7 The present invention provides a test autocorrelation trajectory diagram of the wide spectrum all-fiber femtosecond laser system based on chirped pulse amplification at the C port. DETAILED DESCRIPTION

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

[0027] Embodiment 1

[0028] The embodiment of the present invention provides a wide spectrum all-fiber femtosecond laser system based on chirped pulse amplification, such as Figure 1 As shown, it includes a wide spectrum dissipative soliton mode-locked fiber laser and an all-fiber chirped pulse amplifier connected to each other, the wide spectrum 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 in sequence, the coupler 7 is also connected to the first wavelength division multiplexer 2, and the output port of the wide spectrum dissipative soliton mode-locked fiber laser is port a; the The all-fiber chirped pulse amplifier comprises 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 wide spectrum dissipative soliton mode-locked fiber laser is specifically a fiber ring cavity, the coupler 7 is provided with a first output port and a second output port, the output power ratio of the first output port and the second output port is 20%:80%, 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 for the fiber ring cavity, and the optical signal output by the first wavelength division multiplexer 2 passes 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 in sequence to generate wide spectrum dissipative soliton pulse light, and finally 80% of the wide spectrum dissipative soliton pulse light is input to the first wavelength division multiplexer 2, and the remaining 20% ​​is input to the all-fiber chirped pulse amplifier.

[0030] The all-fiber chirped pulse amplifier is an all-fiber bidirectional pumping structure, which uses optical pulse chirping amplification technology, that is, using dispersion compensation fiber 9 to broaden the 20% wide spectrum dissipative soliton pulse light, using the second gain fiber 11 for power amplification, and using the single-mode fiber 13 for pulse compression, and finally obtains high-power, power-adjustable and stable femtosecond pulse output. The single-mode fiber 13 and the second polarization-independent isolator 14 can achieve pulse width compression.

[0031] Among them, the various components of the wide spectrum dissipative soliton mode-locked fiber laser are connected by optical fiber, and the optical fiber used is a single-mode optical fiber in the 1550nm band. The various components of the all-fiber chirped pulse amplifier are connected by optical fiber, and the optical fiber used is a single-mode optical fiber in the 1550nm band. The coupler 7 and the first polarization-independent isolator 8 are connected by optical fiber, and the optical fiber used is a single-mode optical fiber in the 1550nm band. The first polarization controller 4 and the second polarization controller 6 are both squeezed 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, and 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 working wavelength of the dispersion compensation optical fiber 9 is 1550nm. The working wavelengths of the first pump source 1, the second pump source 15 and the third pump source 16 are all 980nm, and the working 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] Embodiment 2

[0033] The embodiment of the present invention provides a method for adjusting a wide-spectrum 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 pump source and the third pump source to change the system amplification factor;

[0035] Adjusting the length of the first gain fiber to enable the wide spectrum dissipative soliton mode-locked fiber laser to perform ordinary narrow spectrum dissipative soliton mode-locking;

[0036] The first polarization controller is adjusted to find the broadband trapezoidal spectrum and the Q-switched 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 on p134-138 of Laser Physics Letters 8(2) in 2011; the Q-switched state spectrum can be found in "Revealing the transition dynamics from Q switching to mode locking in asoliton laser" published on 123(9):093901 of Physical review letters in 2019.

[0037] The first polarization controller and the second polarization controller are fine-tuned to make the spectrum slightly change between the Q-switched state and the broadband trapezoidal spectrum, and gradually stabilize to the broadband dissipative soliton spectrum state. At this time, the first polarization controller and the second polarization controller are fixed to stabilize the broadband dissipative soliton mode-locked fiber laser to the broadband dissipative soliton mode-locked state.

[0038] Embodiment 3

[0039] The embodiment of the present invention provides a regulation system for a wide spectrum all-fiber femtosecond laser system based on chirped pulse amplification, comprising:

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

[0041] An optical fiber length adjustment module, used for adjusting the length of the first gain optical fiber so that the wide spectrum dissipative soliton mode-locked optical fiber laser performs ordinary narrow spectrum dissipative soliton mode-locking;

[0042] A spectrum adjustment module, used for adjusting the first polarization controller to find a broadband trapezoidal spectrum and a Q-switch state spectrum;

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

[0044] Experimental Results

[0045] like Figure 2 As shown, it is the output spectrum diagram of the wide spectrum dissipative soliton mode-locked fiber laser of the present invention. When the pump power of the wide spectrum dissipative soliton mode-locked fiber laser is 90mW±5mW, a self-starting mode-locked state can be established. It can be observed that the central wavelength of the pulse is 1556.49nm, the 3dB bandwidth of the pulse spectrum is 49.77nm, and the pulse light power is 2mW at this time.

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

[0047] like Figure 4 As shown in Figure 1, it is the output autocorrelation trajectory of a wide spectrum dissipative soliton mode-locked fiber laser. By using Gauss fitting, its pulse width is 2.1ps.

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

[0049] Figure 6 The autocorrelation trajectory of the output light pulse of the wide spectrum dissipative soliton mode-locked fiber laser after pulse broadening and power amplification in the all-fiber chirped pulse amplifier is shown. By using Gauss fitting, the pulse width is 18.39ps, indicating that the pulse light output by the laser is broadened after passing through the dispersion compensation fiber.

[0050] Figure 7 The autocorrelation trajectory of the output light pulse of a wide-spectrum dissipative soliton mode-locked fiber laser after pulse broadening, power amplification and pulse compression in an all-fiber chirped pulse amplifier is shown. Figure 7 This is the autocorrelation trajectory diagram when the power is amplified to 140.06mW. By using Gauss fitting, its pulse width is 791.3fs, which means that the pulse light output by the laser is broadened through the dispersion compensation fiber and then compressed through 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 document, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0052] It should be understood that the above embodiments and descriptions only describe the principles, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection of the present invention.

Claims

1. A wide-spectrum all-fiber femtosecond laser system based on chirped pulse amplification, characterized in that: The invention comprises a wide spectrum dissipative soliton mode-locked fiber laser and an all-fiber chirped pulse amplifier connected to each other. The wide spectrum dissipative soliton mode-locked fiber laser comprises 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, the first wavelength division multiplexer, the first gain fiber, the first polarization controller, the polarization-dependent isolator, the second polarization controller and the coupler are connected in sequence, and the coupler is also connected to the first wavelength division multiplexer. The all-fiber chirped pulse amplifier comprises 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.

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

3. The wide spectrum 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 wide spectrum 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 via an optical fiber, and the optical fiber used is a single-mode optical fiber in the 1550nm band.

5. The wide spectrum 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 have input and output pigtails that are single-mode optical fibers in the 1550nm band, the output pigtails of the first pump source, the second pump source, and the third pump source are single-mode optical fibers in the 1550nm band, and the operating wavelength of the dispersion-compensating optical fiber is 1550nm.

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

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

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

9. A method for adjusting a wide spectrum all-fiber femtosecond laser system based on chirped pulse amplification according to 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 pump source and the third pump source to change the system amplification factor; Adjusting the length of the first gain fiber to enable the wide spectrum 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; The first polarization controller and the second polarization controller are fine-tuned to make the spectrum slightly change between the Q-switched state and the broadband trapezoidal spectrum, and gradually stabilize to the broadband dissipative soliton spectrum state. At this time, the first polarization controller and the second polarization controller are fixed to stabilize the broadband dissipative soliton mode-locked fiber laser to the broadband dissipative soliton mode-locked state.

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

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