CN116231431A - Novel mode-locked soliton fiber laser system based on space alignment structure - Google Patents
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Abstract
The invention discloses a novel mode-locked soliton optical fiber laser system based on a space alignment structure, which comprises the following components: the pumping source outputs pumping light and is connected with the wavelength division multiplexer, and the wavelength division multiplexer couples the pumping light into the annular cavity; the wavelength division multiplexer is connected with the erbium-doped single mode fiber, the erbium-doped single mode fiber is connected with the polarization independent isolator through a first single mode fiber, and the output end of the first fiber collimator is connected with the polarization independent isolator through a second single mode fiber; the first optical fiber collimator outputs collimated laser, and the second optical fiber collimator couples the laser output by the first optical fiber collimator back into the annular cavity to form a space alignment structure; the second optical fiber collimator, the polarization controller and the coupler are connected through a third single mode fiber, the coupler and the wavelength division multiplexer are connected through a fourth single mode fiber to form a closed optical path, and the coupler forms an output end of the system. The invention has the advantages of simple and compact structure, high stability, low cost, easy self-starting mode locking, good repeatability and little interference from external environment.
Description
Technical Field
The invention belongs to the technical field of ultrafast lasers, and particularly relates to a novel mode-locked soliton fiber laser system based on a space alignment structure.
Background
Compared with the traditional ultrafast solid laser system, the ultrafast fiber laser system has the obvious advantages of compact structure, good beam quality, low cost, easiness in thermal management and the like, and has been widely applied to the fields of fiber communication, biomedical treatment, optical imaging, frequency metering and laser processing. To meet the increasing demands of today's applications, further improvements in the stability and output parameters of ultra-fast fiber systems are needed.
For optimization of ultra-fast fiber systems, both the type of pulses output from the system and the method of generating the pulses are required. In terms of pulse types, the method can be divided into traditional solitons generated in a negative dispersion region, dispersion management generated in a near-zero dispersion region, self-similar pulses, dissipative solitons generated in a positive dispersion region, dissipative soliton resonance pulses and the like according to different net dispersion quantities in a laser system cavity. In the region of larger net negative dispersion, the traditional soliton pulse generated by dynamic balance of saturable absorption in the cavity, second-order dispersion and nonlinear effect can keep constant pulse width and spectrum width in the propagation process. There are natural advantages in the stability of the system compared to the other several pulses. In the aspect of pulse generation mode, compared with active mode locking, passive mode locking can realize self-starting pulse output without an additional modulation device. The method greatly reduces the cost and complexity of the system, and is the mainstream technology of the current ultra-fast optical fiber system research. The passive mode locking technology relies on a saturable absorber (Saturable Absorber, SA for short) to generate pulses, and the performance of SA is used to directly determine the output parameters of the system. In recent years, the work of building an ultrafast optical fiber system based on SA such as a semiconductor saturable absorber mirror (Semiconductor Saturable Absorber Mirror, abbreviated as SESAM), a low-dimensional material, or based on nonlinear polarization evolution (Nonlinear Polarization Evolution, abbreviated as NPE), a nonlinear annular mirror (Nonlinear Loop Mirror, abbreviated as NLM), a mamyshaev, a multimode interference effect, etc. has been widely studied.
However, defects such as a SESAM, such as a low damage threshold and poor repeatability of a two-dimensional material, limit the improvement of the output power and stability of the system, and meanwhile, the wavelength range generated by the laser system is limited by the band gap of the material. Although the equivalent saturable absorber can overcome the limit of a material damage threshold and a band gap to realize the broadband saturable absorption effect, the NPE has poor environmental stability, NLM is difficult to self-start, the structure of the Mamyshev is complex, and the problems of large fusion loss of multimode optical fibers and single-mode optical fibers and the like still exist. These drawbacks severely limit the application of ultrafast laser systems in some complex environments.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a novel mode-locked soliton fiber laser system based on a space alignment structure. The technical problems to be solved by the invention are realized by the following technical scheme:
the embodiment of the invention provides a novel mode-locked soliton optical fiber laser system based on a space alignment structure, which comprises the following components: the device comprises a pump source, a wavelength division multiplexer, an erbium-doped single mode fiber, a first single mode fiber, a polarization independent isolator, a second single mode fiber, a first fiber collimator, a second fiber collimator, a polarization controller, a third single mode fiber, a coupler and a fourth single mode fiber; wherein,,
the pumping source outputs pumping light and is connected with the wavelength division multiplexer through a tail fiber, and the wavelength division multiplexer couples the pumping light into the annular cavity;
the output end of the wavelength division multiplexer is connected with the erbium-doped single mode fiber through a passive optical fiber, the erbium-doped single mode fiber is connected with the input end of the polarization independent isolator through the first single mode fiber, and the output end of the first optical fiber collimator is connected with the output end of the polarization independent isolator through the second single mode fiber;
the first optical fiber collimator outputs collimated laser, the second optical fiber collimator couples the collimated laser output by the first optical fiber collimator back into the annular cavity to form a space alignment structure, the space alignment structure generates a saturable absorption effect, and the adjustment of saturated intensity and unsaturated loss is realized by properly adjusting alignment conditions;
the second optical fiber collimator, the polarization controller and the coupler are connected through the third single mode fiber, the coupler and the wavelength division multiplexer are connected through the fourth single mode fiber to form a closed optical path, and the coupler forms an output end of the system.
In one embodiment of the invention, the maximum output power of the pump source is 1.5W.
In one embodiment of the invention, the peak absorption of the erbium doped single mode fiber at 1530nm is 110dB/m.
In one embodiment of the present invention, the output apertures of the first fiber collimator and the second fiber collimator are both 2.0mm.
In one embodiment of the invention, the distance between the first fiber collimator and the second fiber collimator is 5cm to 20cm.
In one embodiment of the invention, the coupling efficiency between the first fiber collimator and the second fiber collimator is 70%.
In one embodiment of the invention, the split ratio of the coupler is 20:80; the laser is output from 20% of the output ends of the couplers, and 80% of the output ends of the couplers are connected with the wavelength division multiplexer.
In one embodiment of the present invention, the first single mode fiber, the second single mode fiber, the third single mode fiber and the fourth single mode fiber are all SMF-28e.
In one embodiment of the invention, a high order soliton pulse is output with a highest single pulse energy of 4.73 nJ.
The invention has the beneficial effects that:
the invention provides a novel mode-locked soliton optical fiber laser system based on a space alignment structure, and creatively provides a mode-locked soliton optical fiber laser system structure, in particular to a novel mode-locked soliton optical fiber laser system based on a space alignment structure: the device comprises a pump source, a wavelength division multiplexer, an erbium-doped single mode fiber, a first single mode fiber, a polarization independent isolator, a second single mode fiber, a first fiber collimator, a second fiber collimator, a polarization controller, a third single mode fiber, a coupler and a fourth single mode fiber; the wavelength division multiplexer couples the pump light into the annular cavity; the output end of the wavelength division multiplexer is connected with the erbium-doped single-mode fiber through a passive optical fiber, the input end of the erbium-doped single-mode fiber is connected with the input end of the polarization independent isolator through a first single-mode fiber, and the output end of the first optical fiber collimator is connected with the output end of the polarization independent isolator through a second single-mode fiber; the first optical fiber collimator outputs collimated laser, the second optical fiber collimator couples the collimated laser output by the first optical fiber collimator back into the annular cavity to form a space alignment structure, the space alignment structure generates a saturable absorption effect, and the adjustment of saturation intensity and non-saturation loss is realized by properly adjusting the alignment condition; the second optical fiber collimator, the polarization controller and the coupler are connected through a third single mode fiber, the coupler and the wavelength division multiplexer are connected through a fourth single mode fiber to form a closed optical path, and the coupler forms an output end of the system. Therefore, the invention has reasonable structure, does not need to introduce any material saturable absorber, and can generate equivalent saturable absorption effect only by changing the alignment condition of the first optical fiber collimator and the second optical fiber collimator. Compared with the traditional soliton fiber laser system based on a true saturable absorber and the traditional equivalent saturable absorption technology generated by utilizing a nonlinear effect, the spatial alignment structure-based saturable absorption effect creatively provided by the invention is free from the limitation of a material damage threshold and a band gap and the limitation of environmental stability, and has higher single pulse energy. In general, the mode-locked soliton fiber laser system provided by the invention has the obvious advantages of simple and compact structure, high stability, low cost, easiness in self-starting mode locking, good repeatability, small interference by external environment and the like, and can be used as a laser source in the fields of fiber communication, micromachining, frequency measurement, biomedicine, nonlinear optical research and the like.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
FIG. 1 is a schematic diagram of a novel mode-locked soliton fiber laser system based on a spatial alignment structure according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of output spectra at different pump powers provided by an embodiment of the present invention;
FIG. 3 is a schematic diagram of a mode-locked pulse sequence at a pump power of 1.5W provided by an embodiment of the present invention;
fig. 4 is a schematic diagram of 6-hour power stability provided by an embodiment of the present invention.
Reference numerals illustrate:
1-a pump source; a 2-wavelength division multiplexer; 3-erbium-doped single-mode optical fiber; 4-a first single mode optical fiber; a 5-polarization independent isolator; 6-a second single mode optical fiber; 7-a first fiber collimator; 8-a second fiber collimator; 9-a polarization controller; 10-a third single mode optical fiber; 11-a coupler; 12-fourth single mode optical fiber.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but embodiments of the present invention are not limited thereto.
In order to achieve a fiber laser system with a simple structure, without being limited by a material damage threshold and a band gap and without being limited by environment, referring to fig. 1, an embodiment of the present invention provides a novel mode-locked soliton fiber laser system based on a spatial alignment structure, including: the device comprises a pump source 1, a wavelength division multiplexer 2, an erbium-doped single mode fiber 3, a first single mode fiber 4, a polarization independent isolator 5, a second single mode fiber 6, a first fiber collimator 7, a second fiber collimator 8, a polarization controller 9, a third single mode fiber 10, a coupler 11 and a fourth single mode fiber 12; wherein,,
the pump source 1 outputs pump light and is connected with the wavelength division multiplexer 2 through the tail fiber, and the wavelength division multiplexer 2 couples the pump light into the annular cavity; the output end of the wavelength division multiplexer 2 is connected with the erbium-doped single-mode fiber 3 through a passive optical fiber, the input end of the erbium-doped single-mode fiber 3 is connected with the input end of the polarization independent isolator 5 through a first single-mode fiber 4, and the output end of the first optical fiber collimator 7 is connected with the output end of the polarization independent isolator 5 through a second single-mode fiber 6; the first optical fiber collimator 7 outputs collimated laser, the second optical fiber collimator 8 couples the collimated laser output by the first optical fiber collimator 7 back into the annular cavity to form a space alignment structure, the space alignment structure generates a saturable absorption effect, and the adjustment of saturation intensity and unsaturated loss is realized by properly adjusting the alignment condition; the second fiber collimator 8 and the polarization controller 9 are connected with the coupler 11 through the third single mode fiber 10, the coupler 11 and the wavelength division multiplexer 2 are connected through the fourth single mode fiber 12 to form a closed optical path, and the coupler 11 forms an output end of the system.
Preferably, the pump source 1 is a single-mode or multimode Laser Diode (LD); the maximum output power of the pump source 1 is 1.5W; the pump source 1 outputs 976nm pump light.
Preferably, the peak absorption of the erbium-doped single mode fiber 3 at 1530nm is 110dB/m.
Preferably, the output apertures of the first optical fiber collimator 7 and the second optical fiber collimator 8 are 2.0mm.
Preferably, the distance between the first fiber collimator 7 and the second fiber collimator 8 is 5cm to 20cm.
Preferably, the coupling efficiency between the first fiber collimator 7 and the second fiber collimator 8 is 70%.
Preferably, the splitting ratio of the coupler 11 is 20:80; wherein, 20% output end of the coupler 11 outputs laser light, and 80% output end of the coupler 11 is connected with the wavelength division multiplexer 2.
Preferably, the first single-mode optical fiber 4, the second single-mode optical fiber 6, the third single-mode optical fiber 10 and the fourth single-mode optical fiber 12 are all SMF-28e.
Preferably, a higher order soliton pulse with a highest single pulse energy of 4.73nJ is output.
Through the study of the inventor, the fiber laser system provided by the invention can realize the saturable absorption effect through a space alignment structure, and the principle is derived from the dependence of the coupling efficiency peak power of the laser received by the second fiber collimator 8. The laser spot output by the first fiber collimator 7 generates a small-amplitude divergence with the increase of the propagation distance. The core of the second fiber collimator 8 then acts as a hard stop, introducing additional coupling losses. As the peak power of the input laser increases, the peak power density at the core of the second fiber collimator 8 also increases. When the input peak power reaches a certain threshold value, a self-focusing effect caused by nonlinear refractive index change is generated, so that the coupling loss caused by light spot divergence is reduced, and the coupling efficiency is improved. As the input power is further increased, the rate of increase of the coupling efficiency gradually stabilizes the final region saturation. Therefore, the equivalent saturable absorption effect with high-power pulse coupling efficiency and low-power pulse coupling efficiency is realized. And this effect is only related to the optical power received by the second fiber collimator 8. Thus by varying the alignment conditions between the two collimators, reducing the power density to the second collimator 8 also changes the modulation depth and saturation power of this equivalent saturable absorption effect.
In order to verify the effectiveness of the novel mode-locked soliton fiber laser system based on the spatial alignment structure provided by the embodiment of the invention, the following experiment is performed for verification.
The LD pump source 1 outputs pump light with the central wavelength of 976nm and the maximum average power of 1.5W, the pump light is used as a tail fiber to be connected with the input end of the wavelength division multiplexer 2, the wavelength division multiplexer 2 couples 976nm pump light into the annular cavity, the wavelength division multiplexer 2 passes through an SMF-28e passive fiber and an erbium-doped single mode fiber 3, the diameters of a core layer and a cladding layer of the erbium-doped single mode fiber 3 are 4/125 mu m, the peak absorption coefficient of the core at 1530nm is 110dB/m, the length of the erbium-doped single mode fiber 3 is too short, so that the energy of the pump light can not be fully absorbed, the output power is lower, and the output light has residues of the pump light; too long a length of the erbium-doped single-mode fiber 3 will cause the generated laser light to be re-absorbed by itself, and the output power will also become low. The erbium-doped single-mode fiber 3 is connected with the polarization independent isolator 5 through a section of SMF-28e first single-mode fiber 4, the isolation degree of the polarization independent isolator 5 is 60dB, the maximum bearing average power is 3W, and the unidirectional operation of the optical signal in the annular cavity is ensured.
The polarization independent isolator 5 is connected with the first optical fiber collimator 7 through a section of SMF-28e second single mode fiber 6, the output caliber of the first optical fiber collimator 7 is 2.0mm, the working distance is 20cm, and the maximum bearing power is 2W. The collimator lens is plated with a 1.5 mu m antireflection film, so that the F-P cavity effect is prevented from being generated by Fresnel reflection of the output end surface while the good output beam quality is ensured. The first optical fiber collimator 7 is horizontally arranged to output collimated laser light with the diameter of 2mm, and the beam waist of the collimated laser light is positioned at the position 10cm behind the collimator. The output caliber of the second optical fiber collimator 8 is 2.0mm, the working distance is 20cm, and the maximum bearing power is 2W. The second fiber collimator 8 was placed 20cm behind the first fiber collimator 7, and the height was 45cm in line with the first fiber collimator 7. The second optical fiber collimator 8 is used for coupling and receiving the space light output by the first optical fiber collimator 7, and the coupling efficiency of the space structure is adjusted by changing the angle between the second optical fiber collimator 8 and the first optical fiber collimator 7. By changing the alignment condition, the equivalent saturable absorption effect that the high-power part has high transmittance and the low-power part has low transmittance when the pulse passes can be realized. The transmittance of the center part of the strongest pulse in the cavity is highest, the transmittance of the two wing parts of the pulse and other stray pulses is lower, phase locking between oscillation frequencies is achieved, and finally mode locking is achieved.
The second fiber collimator 8, the polarization controller 9 and the coupler 11 are connected by a section of the third single mode fiber 10 of SMF-28e. The polarization controller 9 can adjust the polarization state in the cavity and can play a role in fine tuning the cavity length. The split ratio of the coupler 11 is 20:80, 20% of ports of the coupler 11 are used as the output end of the system, and 80% of the output end of the coupler 11 is connected with one end of the wavelength division multiplexer 2 through a section of SMF-28e fourth single mode fiber to form a closed loop. The lengths of the first single mode fiber 4, the second single mode fiber 6 and the third single mode fiber 10 are selected because if the lengths of the optical fibers are too short to realize the fusion splicing process when the optical fiber fusion splicer is used for fusion splicing the optical fiber connection devices, the lengths of at least 1m are reserved for the subsequent optimization system process, and enough allowance is reserved when the different devices are required to be re-spliced. The fourth single mode fiber 12 not only leaves sufficient margin for the need to re-splice different devices during subsequent optimization of the system. Moreover, because the group velocity dispersion of a single mode fiber SMF-28e is negative at 1.5 μm, conventional solitons are typically generated in a large, net negative dispersion region within the cavity. And a sufficient single-mode fiber length is selected to be provided as a dispersion delay line, a large net negative dispersion environment is provided, and the generation of the traditional soliton is facilitated.
In addition, the fundamental soliton generated at shorter cavity length, limited by the soliton area theorem, outputs single pulse energy typically below 0.1nJ. And the fourth single-mode fiber 12 enables the total cavity length to be far longer than the soliton period, so that the generation of high-order solitons can be supported, the output parameters are further improved, and the system finally obtains soliton output of up to 4.73 nJ. The oscillator is a full negative dispersion mode locking fiber laser system, and in the full negative dispersion fiber laser system, a soliton forming mechanism plays a key role, and through a negative dispersion effect, the dynamic balance between a saturated absorption effect and a nonlinear effect can be realized, so that almost zero-chirp mode locking pulse is generated.
In the embodiment of the invention, the polarization controller 9 is adjusted to a proper position, the state of the laser in the annular cavity is controlled by the polarization controller 9, and the pitching angle of the second optical fiber collimator 8 is changed to adjust the coupling efficiency of the space structure to a proper position. The pump power can generate stable mode locking at the minimum of 800mW, and the mode locking central wavelength is 1560.9nm.
Fig. 2 illustrates output spectrum conditions under different pump powers, wherein different color lines only schematically distinguish the output spectrum conditions under different wavelengths, and the output spectrum conditions do not contain information on a technical scheme, and the abscissa in fig. 2 represents Wavelength (Wavelength/nm), the ordinate represents spectrum Intensity (Intensity/dB), and as can be seen from fig. 2, the pump powers are gradually increased to 1000, 1100, 1200, 1300, 1400 and 1500mW, mode locking is still stable, and after the pump power exceeds 1300mW, obvious Kelly sidebands generated by dispersive wave resonance appear on the spectrum, so that the traditional soliton pulse is proved to be generated. The alignment condition among the collimators is linearly adjusted, so that the tuning of the soliton spectrum center wavelength to the short wave direction slightly can be realized, and the range is 1560.9 to 1559.0nm.
Fig. 3 illustrates a mode-locked pulse sequence at a pump power of 1.5W, the abscissa in fig. 3 represents Time (Time/. Mu.s), and the ordinate represents spectral Intensity (Intensity/dB), and it can be seen from fig. 3 that the stable mode-locked pulse sequence has a spacing of 260ns, which coincides with the cavity length of the laser system when the pump power is fixed at 1.5W.
Fig. 4 illustrates the Output Power of the laser system after 6 hours, and the abscissa in fig. 4 represents Time (Time/h), and the ordinate represents Output Power (Output Power/mW), and it can be seen from fig. 4 that, when the average Power of the system Output is 17mW, the root mean square (rms) value of the Power within 6 hours is 0.23%.
In summary, the novel mode-locked soliton fiber laser system based on the spatial alignment structure provided by the embodiment of the invention creatively provides a mode-locked soliton fiber laser system structure, and specifically: the device comprises a pump source 1, a wavelength division multiplexer 2, an erbium-doped single mode fiber 3, a first single mode fiber 4, a polarization independent isolator 5, a second single mode fiber 6, a first fiber collimator 7, a second fiber collimator 8, a polarization controller 9, a third single mode fiber 10, a coupler 11 and a fourth single mode fiber 12; the pump source 1 outputs pump light and is connected with the wavelength division multiplexer 2 through a tail fiber, and the wavelength division multiplexer 2 couples the pump light into the annular cavity; the output end of the wavelength division multiplexer 2 is connected with the erbium-doped single-mode fiber 3 through a passive optical fiber, the input end of the erbium-doped single-mode fiber 3 is connected with the input end of the polarization independent isolator 5 through a first single-mode fiber 4, and the output end of the first optical fiber collimator 7 is connected with the output end of the polarization independent isolator 5 through a second single-mode fiber 6; the first optical fiber collimator 7 outputs collimated laser, the second optical fiber collimator 8 couples the collimated laser output by the first optical fiber collimator 7 back into the annular cavity to form a space alignment structure, the space alignment structure generates a saturable absorption effect, and the adjustment of saturation intensity and unsaturated loss is realized by properly adjusting the alignment condition; the second fiber collimator 8 and the polarization controller 9 are connected with the coupler 11 through the third single mode fiber 10, the coupler 11 and the wavelength division multiplexer 2 are connected through the fourth single mode fiber 12 to form a closed optical path, and the coupler 11 forms an output end of the system. It can be seen that the invention has reasonable structure, does not need to introduce any material saturable absorber, and can generate equivalent saturable absorption effect only by changing the alignment condition of the first optical fiber collimator 7 and the second optical fiber collimator 8. Compared with the traditional soliton fiber laser system based on a true saturable absorber and the traditional equivalent saturable absorption technology generated by utilizing a nonlinear effect, the spatial alignment structure-based saturable absorption effect provided by the embodiment of the invention is creatively generated, is not limited by a material damage threshold and a band gap and is also not limited by environmental stability, and has higher monopulse energy. In general, the mode-locked soliton fiber laser system provided by the embodiment of the invention has the obvious advantages of simple and compact structure, high stability, low cost, easiness in self-starting mode locking, good repeatability, small interference by external environment and the like, and can be used as a laser source in the fields of fiber communication, micromachining, frequency measurement, biomedicine, nonlinear optical research and the like.
Experiments prove that when the pumping power is 1.5W, the center wavelength 1559.0nm to 1560.9nm is tunable at the wavelength of 1.5 mu m by adjusting the polarization controller 9 to a proper position, so that high-stability high-order soliton pulse with the highest single pulse energy of 4.73nJ and the pulse width of 3.5ps can be obtained, namely ultrafast laser is realized, the single pulse energy of 4.73nJ overcomes the limitation of the fundamental-order soliton area theorem, and the generation of the high-order soliton is proved. The rms value was calculated to be 0.23% over 6 hours of power stability testing, demonstrating the stability of the system.
In the description of the present invention, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
Although the invention is described herein in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the specification and the drawings. In the description, the word "comprising" does not exclude other elements or steps, and the "a" or "an" does not exclude a plurality. Some measures are described in mutually different embodiments, but this does not mean that these measures cannot be combined to produce a good effect.
The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.
Claims (9)
1. Novel mode locking soliton fiber laser system based on space alignment structure, characterized by comprising: the device comprises a pump source (1), a wavelength division multiplexer (2), an erbium-doped single mode fiber (3), a first single mode fiber (4), a polarization independent isolator (5), a second single mode fiber (6), a first fiber collimator (7), a second fiber collimator (8), a polarization controller (9), a third single mode fiber (10), a coupler (11) and a fourth single mode fiber (12); wherein,,
the pump source (1) outputs pump light and is connected with the wavelength division multiplexer (2) through a tail fiber, and the wavelength division multiplexer (2) couples the pump light into the annular cavity; the output end of the wavelength division multiplexer (2) is connected with the erbium-doped single-mode fiber (3) through a passive optical fiber, the erbium-doped single-mode fiber (3) is connected with the input end of the polarization independent isolator (5) through the first single-mode fiber (4), and the first optical fiber collimator (7) is connected with the output end of the polarization independent isolator (5) through the second single-mode fiber (6); the first optical fiber collimator (7) outputs collimated laser, the second optical fiber collimator (8) couples the collimated laser output by the first optical fiber collimator (7) back into the annular cavity to form a space alignment structure, the space alignment structure generates a saturable absorption effect, and the adjustment of saturation intensity and unsaturated loss is realized by properly adjusting the alignment condition; the second optical fiber collimator (8), the polarization controller (9) and the coupler (11) are connected through the third single mode fiber (10), the coupler (11) and the wavelength division multiplexer (2) are connected through the fourth single mode fiber (12) to form a closed optical path, and the coupler (11) forms an output end of the system.
2. The novel mode-locked soliton fiber laser system based on spatial alignment structure according to claim 1, characterized in that the maximum output power of the pump source (1) is 1.5W.
3. The novel mode-locked soliton fiber laser system based on spatial alignment structure according to claim 1, characterized in that the peak absorption of the erbium-doped single-mode fiber (3) at 1530nm is 110dB/m.
4. The novel mode-locked soliton fiber laser system based on spatial alignment structure according to claim 1, wherein the output apertures of the first fiber collimator (7) and the second fiber collimator (8) are both 2.0mm.
5. The novel mode-locked soliton fiber laser system based on spatial alignment structure according to claim 1, characterized in that the distance between the first fiber collimator (7) and the second fiber collimator (8) is 5 cm-20 cm.
6. The novel mode-locked soliton fiber laser system based on spatial alignment structure according to claim 1, characterized in that the coupling efficiency between the first fiber collimator (7) and the second fiber collimator (8) is 70%.
7. The novel mode-locked soliton fiber laser system based on spatial alignment structure according to claim 1, characterized in that the splitting ratio of the coupler (11) is 20:80; the laser beam is output from 20% of the output end of the coupler (11), and 80% of the output end of the coupler (11) is connected with the wavelength division multiplexer (2).
8. The novel mode-locked soliton fiber laser system based on spatial alignment structure according to claim 1, characterized in that the first single mode fiber (4), the second single mode fiber (6), the third single mode fiber (10) and the fourth single mode fiber (12) are all of the type SMF-28e.
9. The novel mode-locked soliton fiber laser system based on spatial alignment structure of claim 1, wherein the high order soliton pulse with highest single pulse energy of 4.73nJ is output.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN118315908A (en) * | 2024-06-13 | 2024-07-09 | 长鹰恒容电磁科技(成都)有限公司 | Passive mode-locked fiber laser with polymorphic solitons |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN118315908A (en) * | 2024-06-13 | 2024-07-09 | 长鹰恒容电磁科技(成都)有限公司 | Passive mode-locked fiber laser with polymorphic solitons |
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