CN115663577A - Bidirectional mode-locked fiber laser based on graded-index multimode fiber - Google Patents
Bidirectional mode-locked fiber laser based on graded-index multimode fiber Download PDFInfo
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- CN115663577A CN115663577A CN202211343147.1A CN202211343147A CN115663577A CN 115663577 A CN115663577 A CN 115663577A CN 202211343147 A CN202211343147 A CN 202211343147A CN 115663577 A CN115663577 A CN 115663577A
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Abstract
The invention discloses a bidirectional mode-locked fiber laser based on a graded-index multimode fiber, wherein a fiber laser system comprises a semiconductor pumping source, a single-mode wavelength division multiplexer, a single-mode gain fiber, a single-mode output coupler, a graded-index multimode fiber saturable absorber and a bidirectional ring-shaped resonant cavity formed by connecting a polarization controller. The semiconductor pump source provides energy for the laser and provides gain for the generation of pulse laser by matching with the gain medium; realizing the bidirectional mode-locked operation of the fiber laser by utilizing the nonlinear multimode interference effect in the graded-index multimode fiber; the polarization controller is used for changing the local polarization state of the laser, and the adjustment and the switching of the bidirectional mode locking state of the laser are realized. The bidirectional mode-locking fiber laser based on the multimode graded index fiber can realize bidirectional mode locking, is fully fiber-based, has the advantages of simple structure, high damage threshold value and the like, and has important application in gyroscopes.
Description
Technical Field
The invention belongs to the field of fiber lasers, and particularly relates to a bidirectional mode-locked fiber laser based on a graded-index multimode fiber.
Background
The mode-locked fiber laser is used as an ultrashort pulse light source, has the advantages of rich spectrum, short time interval, high peak power and the like, has wide scientific research value, and has wide application background in the aspects of space communication, pulse shaping, laser processing, optical signal processing and the like.
Most of mode-locked fiber lasers adopt a ring cavity structure, in a ring resonant cavity, a non-reciprocal optical isolator is generally adopted to realize the one-way operation of mode locking, and suppress stray light in the cavity, so that the threshold value of mode locking is reduced, however, the one-way ring resonant cavity structure can only output one soliton laser pulse, in comparison, the two-way mode-locked fiber laser can simultaneously generate two different ultrashort pulses in Clockwise (CW) and counterclockwise (CCW) directions, so that the two-way output of different repetition frequencies, central wavelengths and pulse durations in the same laser is realized, various application requirements are met, and the two-way mode-locked fiber laser has a wider application prospect in the fields of fiber sensing, double comb spectroscopy and the like.
The graded-index multimode fiber has rich nonlinearity and dispersion characteristics, and the saturable absorber based on the graded-index multimode fiber has the characteristics of low cost, high compactness, controllable nonlinearity, wide wavelength output range, low saturation energy and the like, so that the laser is more flexible, and particularly, in a bidirectional mode-locked fiber laser, effective control is provided for the generation of different ultrashort pulse solitons.
Disclosure of Invention
Is composed of
And the device is used for adjusting the polarization state of light in the cavity.
The semiconductor pump solves the problems, and the invention provides a bidirectional mode-locked fiber laser based on a graded-index multimode fiber, aiming at realizing the bidirectional operation of the mode-locked fiber laser and outputting a plurality of solitons with different forms at the same time, thereby solving the problems related to the unidirectional operation of the mode-locked fiber laser and the incapability of outputting the traditional solitons and the bound solitons at the same time.
In order to achieve the above object, the present invention provides a bidirectional mode-locked fiber laser of a ring cavity structure, comprising a semiconductor pump source for outputting pump light; a single mode wavelength division multiplexer for sequentially forming an optical loop; a single-mode erbium-doped gain fiber for generating population inversion; a single-mode output coupler for outputting laser light; a graded-index multimode fiber for a saturable absorber device; the polarization control pump source, the single-mode wavelength division multiplexer, the single-mode erbium-doped gain fiber, the single-mode output coupler, the graded-index multimode fiber and the polarization controller adopt automatic fusion of an optical fiber fusion splicer.
The output wavelength of the semiconductor pump source is 976nm.
Furthermore, the working wavelength of the reflection port of the single-mode wavelength division multiplexer and the working wavelength of the optical coupler are within 1520nm to 1620 nm.
The single-mode gain fiber is a single-mode erbium-doped gain fiber, and the length range of the single-mode erbium-doped gain fiber is set to be 1m-2m.
Further, the splitting ratio of the direct output end and the coupling output end of the single-mode output coupler is 70.
Furthermore, the size of a core of the graded-index multimode fiber is 62.5 mu m, and the length range of the core is set to be between 20cm and 30cm.
Compared with the prior art, the bidirectional mode-locked fiber laser based on the multimode graded index fiber provided by the invention has the following beneficial effects:
the multimode fiber based on the graded index provides a new method for realizing bidirectional mode locking.
The bidirectional mode-locking fiber laser is simple in structure, excellent in performance, capable of being completed only through fiber fusion, high in damage threshold, long in service life and easy to popularize and use practically.
All elements or optical fibers adopted in the bidirectional mode-locked fiber laser are mature in manufacturing process, mature commercial elements or commercial optical fibers are adopted, cost is greatly reduced, the structure of the laser is simplified, and stability and reliability of the bidirectional mode-locked fiber laser are improved.
Drawings
The above description is only an overview of the technical solutions of the present invention, and in order to further understand the specific structure and the effects of the present invention, the purpose, the features and the effects of the present invention will be described below with reference to the accompanying drawings.
Fig. 1 is a schematic diagram of a bidirectional mode-locked fiber laser according to an embodiment of the present invention.
In the figure, 1, a semiconductor pump source, 2, a single-mode wavelength division multiplexer, 3, a single-mode gain fiber, 4, a single-mode output coupler, 5, a graded-index multimode fiber, 6 and a polarization controller.
FIG. 2 is a spectral plot of the clockwise mode-locked operational output of a laser in accordance with an example of the present invention.
FIG. 3 is a spectral plot of the counterclockwise mode-locked operation output of a laser in accordance with an example of the present invention.
Fig. 4 is a pulse sequence diagram of the output of a bi-directional mode-locked operation of a laser in accordance with an example of the present invention.
FIG. 5 is a graph of the autocorrelation of an output pulse of a laser operating in clockwise mode-locked mode in accordance with an embodiment of the present invention.
FIG. 6 is a graph of the autocorrelation of the output pulse of a laser operating in a counter-clockwise mode-locked mode in accordance with an embodiment of the present invention.
Detailed description of the preferred embodiments
The following is a detailed description of the present invention, and it should be noted that the present invention is not limited to the following specific examples, and all other examples obtained by those skilled in the art without any inventive work fall within the scope of the present invention. The invention is now described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown.
Example 1
This example presents a two-way mode-locked fiber laser based on a graded-index multimode fiber. A schematic diagram of the structure of a bidirectional mode-locked fiber laser according to the present invention is shown in fig. 1. The single-mode gain fiber optical fiber laser comprises a semiconductor pump source 1, a single-mode wavelength division multiplexer 2, a single-mode gain fiber 3, a single-mode output coupler 4, a saturable absorber 5 and a polarization controller 6 which are sequentially welded to form a ring cavity structure; the saturable absorber 5 includes a single mode fiber, a graded-index multimode fiber and a single mode fiber which are connected in sequence.
The semiconductor pump source 1 is used as a basic light source to provide pump light for the optical fiber laser; the single-mode wavelength division multiplexer 2 is used for integrating light with two different central wavelengths into the same optical fiber; the single-mode gain optical fiber 3 is used as a gain medium to absorb pump light and excite light with the central wavelength in a 1550nm wave band; the single-mode output coupler 4 is used for splitting one beam of light into two beams according to a splitting ratio of 70; the saturable absorber 5 is used for realizing bidirectional mode-locked operation of the laser; the polarization controller is used for adjusting the polarization state of light in the cavity and realizing the adjustment and switching of the bidirectional mode locking state.
Fig. 2 is a spectrum diagram of a clockwise mode-locked pulse of the bidirectional mode-locked fiber laser of the present application at a pump power of 430mW, with a center wavelength of 1596.45nm and a 3db bandwidth of 2.41nm.
Fig. 3 is a spectrum diagram of a counter-clockwise mode-locked pulse of the bidirectional mode-locked fiber laser of the present application at a pump power of 430mW, with a center wavelength of 1596.89nm and a bandwidth of 3db of 4.37nm.
Fig. 4 is a diagram of a bidirectional mode-locked pulse sequence of the bidirectional mode-locked fiber laser of the present application at a pump power of 430mW, with a pulse interval of about 43.8ns, corresponding to a pulse repetition frequency of 23.18MHz.
Fig. 5 is a graph showing autocorrelation curves of output pulses of the bidirectional mode-locked fiber laser of the present application in the clockwise mode-locked state at a pump power of 430mW, which is 1.27ps.
Fig. 6 is a graph showing autocorrelation of an output pulse of the bidirectional mode-locked fiber laser of the present application in a counterclockwise mode-locked state at a pump power of 430mW, which is 0.74ps.
The above description is intended only to illustrate the technical solution of the present invention, and not to limit it, and it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, improvement and the like made within the spirit and principle scope of the technical scheme of the invention shall be included in the protection scope of the invention.
Claims (10)
1. A bidirectional mode-locked fiber laser based on a graded-index multimode fiber, comprising: the device comprises a semiconductor pump source (1), a single-mode wavelength division multiplexer (2), a single-mode gain fiber (3), a single-mode output coupler (4), a graded-index multimode fiber (5) and a polarization controller (6).
2. The optical components and optical fibers as claimed in claim 1 are completed by automatic fusion of optical fiber fusion splicer, the semiconductor pump source is used for realizing the introduction of pump light energy; the single-mode wavelength division multiplexer is used for sequentially forming an optical loop; the single-mode output coupler is used for outputting laser of the laser; the graded-index multimode fiber is used for a saturable absorber to realize bidirectional mode-locked operation of a laser; the polarization controller is used for adjusting the light polarization state in the annular resonant cavity and realizing the adjustment and switching of the bidirectional mode locking state of the laser.
3. A graded-index multimode fiber-based two-way mode-locked fiber laser as claimed in claim 1, characterized in that: the output wavelength of the semiconductor pump source is 976nm.
4. A graded-index multimode fiber-based two-way mode-locked fiber laser as claimed in claim 1, characterized in that: the splitting ratio of the direct output end to the coupling output end of the single-mode output coupler is 70.
5. A graded-index multimode fiber-based bidirectional mode-locked fiber laser as claimed in claim 1, characterized in that: the working wavelength of the reflection port of the single-mode wavelength division multiplexer and the optical coupler is in a wave band of 1520nm to 1620 nm.
6. A graded-index multimode fiber-based two-way mode-locked fiber laser as claimed in claim 1, characterized in that: the single-mode gain fiber is a single-mode erbium-doped gain fiber, the absorption coefficient is 55dB/m @1530nm, and the length range is 1m to 2m.
7. A graded-index multimode fiber-based bidirectional mode-locked fiber laser as claimed in claim 1, characterized in that: the polarization controller is used for adjusting the local light polarization state and realizing the adjustment and switching of the bidirectional mode locking state.
8. A graded-index multimode fiber-based two-way mode-locked fiber laser as claimed in claim 1, characterized in that: the graded-index multimode fiber saturable absorber is formed by respectively welding common single mode fibers at two ends of a section of graded-index multimode fiber and is used for maintaining and starting mode locking.
9. The graded-index multimode fiber of claim 8, wherein: the core diameter of the GI multimode fiber was 62.5 μm.
10. The graded-index multimode fiber of claim 8, wherein: the length range of the graded-index multimode fiber is set to be within the range of 20 cm-30cm.
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| CN202211343147.1A CN115663577A (en) | 2022-10-31 | 2022-10-31 | Bidirectional mode-locked fiber laser based on graded-index multimode fiber |
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| CN202211343147.1A CN115663577A (en) | 2022-10-31 | 2022-10-31 | Bidirectional mode-locked fiber laser based on graded-index multimode fiber |
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