Fiber laser for promoting stable soliton attraction state through high-birefringence fiber

Abstract

The invention belongs to the technical field of lasers, and discloses a fiber laser for promoting generation of a stable soliton attraction state by using a high-birefringence fiber. The optical fiber laser comprises a laser pumping source, a wavelength division multiplexer, an erbium-doped gain optical fiber, a polarization independent isolator, a polarization controller, a polarization maintaining optical fiber, an output coupler and a mode locking device based on a carbon nanotube saturable absorber, and all the components are sequentially connected through single-mode optical fibers. The polarization-maintaining optical fiber is a panda-shaped polarization-maintaining optical fiber with a high birefringence effect. The polarization direction and the polarization state in the cavity are accurately controlled by adjusting the polarization controller, phase synchronization of soliton pulses is achieved when the polarization maintaining optical fiber is output, soliton energy in the cavity is rapidly accumulated, soliton splitting is triggered, and finally a stable multi-pulse soliton attraction state is formed. The design is simple and convenient to operate, and stability and anti-interference capability of soliton transmission are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber lasers, in particular to an optical fiber laser using a high-birefringence optical fiber to promote the generation of a stable soliton attraction state. Background Art

[0002] Solitons are localized structures in nonlinear systems. Since their discovery, they have been a hot topic in the fields of optics, nonlinear dynamics, and ultrafast optics. The soliton phenomenon in single-mode optical fibers has played a key role in promoting the development of optical fiber communications and mode-locked laser technology. Its core mechanism is the dynamic balance between anomalous dispersion and self-phase modulation in the medium. This balance gives solitons stable wave packet characteristics, allowing them to maintain their shape and energy unchanged during long-distance transmission. However, traditional fiber lasers have poor stability and limited anti-interference capabilities, which makes the application of solitons as stable information carriers face more stringent conditions. Summary of the invention

[0003] In order to solve the above-mentioned deficiencies and shortcomings of the prior art, the present invention provides a fiber laser that promotes the generation of a stable soliton attraction state using a high birefringence fiber.

[0004] To achieve the above-mentioned purpose, a fiber laser that promotes stable soliton attraction state by high birefringence fiber is provided, specifically, comprising a laser pump source, a wavelength division multiplexer, an erbium-doped gain fiber, a polarization-independent isolator, a polarization controller, a polarization-maintaining fiber, an output coupler, and a carbon nanotube-based saturable absorber mode-locking device.

[0005] Preferably, the laser pump uses 976nm band laser, which has strong stability and adjustable power, and provides reliable energy support for the formation of solitons in the optical path.

[0006] Preferably, the wavelength division multiplexer comprises an input end 2a and an input end 2b, and functions to couple the 976nm pump light with the 1550nm band light wave and input them into the resonant cavity through the input end 2c.

[0007] Preferably, the erbium-doped gain fiber is 0.5 m long, and stimulates erbium ions to transition to a high-energy state by absorbing the energy of 980 nm pump light, and achieves population inversion through non-radiative relaxation, ultimately generating stable and efficient light output in the 1550 nm band.

[0008] Preferably, the single-mode optical fiber has a total length of 18.94 m and is used to transmit light waves in the 1550 nm band.

[0009] Preferably, the polarization-independent isolator can effectively prevent the light beam from flowing back, ensure unidirectional transmission in the optical path, and provide good protection for the device.

[0010] Preferably, the polarization controller is composed of three wave plates, and by precisely adjusting their rotation angles, the polarization direction and polarization state of light can be flexibly changed, thereby realizing dynamic regulation of the soliton state. Different soliton state distribution characteristics can be obtained by independently rotating one of the wave plates while keeping the other two wave plates stationary.

[0011] Preferably, the polarization-maintaining optical fiber introduces a significant high birefringence effect into the cavity, so that the two polarization states outputted through the polarization-maintaining optical fiber are approximately linearly coupled, thereby triggering soliton splitting.

[0012] Preferably, the output coupler comprises a 30% output end 7c and a 70% output end 7b.

[0013] Preferably, the carbon nanotube-based saturable absorption mode-locking device uses a film made of carbon nanotubes, which is sandwiched between two optical fiber connectors and fixedly connected by a flange to select the longitudinal mode and achieve pulse narrowing.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The present invention provides a fiber laser that uses high birefringence fiber to promote stable soliton attraction state, which has the advantages of simple structure and low cost. The high birefringence effect introduced by polarization-maintaining fiber enables the pulses transmitted in the cavity to achieve approximately linear coupling when output, and induces soliton pulse splitting under the action of peak power clamping effect, thereby forming a stable multi-pulse soliton attraction state with basically consistent amplitude and pulse width.

[0016] 2. The present invention further studies the stability of the multi-pulse soliton attraction state under collision conditions. The study shows that even in the case of collision, the multi-pulse soliton attraction state can still maintain the stability of the internal structure. This anti-interference performance significantly improves the stability of the laser in a complex environment, and at the same time provides a more reliable and stable carrier for the information communication field. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1The structure diagram of a fiber laser for generating a stable soliton attraction state by using a high birefringence fiber provided by the present invention includes a laser pump source 1, a wavelength division multiplexer 2, an erbium-doped gain fiber 3, a polarization-independent isolator 4, a polarization controller 5, a polarization-maintaining fiber 6, an output coupler 7, and a mode-locking device 8 based on a carbon nanotube saturable absorber.

[0019] Figure 2 (a)-(c) are the time domain evolution results of 4-pulse and 5-pulse stable soliton attraction states output by a fiber laser that generates stable soliton attraction states using high birefringence fiber provided by the present invention, as well as a 7-pulse soliton attraction state that is subject to collision interference.

[0020] Figure 3 (a)-(c) are the three-dimensional display results of the amplitude and pulse width of each pulse in the case of 4-pulse and 5-pulse stable soliton attraction states and 7-pulse soliton attraction states disturbed by collision.

[0021] Figure 4 (a)-(c) are the interaction diagrams of pulses in the stable soliton attraction state of 4 pulses and 5 pulses and the soliton attraction state of 7 pulses disturbed by collision. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] Example

[0024] The purpose of the present invention is to enhance the birefringence effect in the fiber laser cavity by introducing polarization-maintaining fiber. The high birefringence characteristics of the polarization-maintaining fiber enable the pulses in the fiber laser to undergo approximately linear coupling during propagation, thereby inducing the splitting of soliton pulses and finally forming a stable multi-pulse soliton attraction state. The present invention has the characteristics of simple operation, strong stability and strong anti-interference.

[0025] Figure 1 The structure diagram of a fiber laser for generating a stable soliton attraction state by using a high birefringence fiber provided by the present invention, the fiber laser comprises a laser pump source 1, a first input end 2a of a wavelength division multiplexer, an erbium-doped gain fiber 3, a polarization-independent isolator 4, a polarization controller 5, a polarization-maintaining fiber 6, a 70% signal output end 7b of an output coupler, a mode-locking device 8 based on a carbon nanotube saturable absorber, and a second input end 2b of the wavelength division multiplexer. They are sequentially connected through a 18.94-meter single-mode optical fiber to form a closed-loop laser resonant cavity.

[0026] The laser pump 1 uses 976nm band laser, which has strong stability and adjustable power, and provides reliable energy support for the formation of solitons in the optical path.

[0027] The wavelength division multiplexer 2 comprises an input end 2a and an input end 2b, and functions to couple the 976nm pump light with the 1550nm band light wave and input them into the resonant cavity through the input end 2c.

[0028] The erbium-doped gain fiber 3 is 0.5 m long and excites erbium ions to transition to a high-energy state by absorbing the energy of 980 nm pump light, and achieves population inversion through non-radiative relaxation, ultimately generating stable and efficient light output in the 1550 nm band.

[0029] The polarization-independent isolator 4 can effectively prevent the light beam from flowing back, ensure unidirectional transmission in the optical path, and at the same time play a good protective role for the device.

[0030] The polarization controller 5 is composed of three wave plates. By precisely adjusting their rotation angles, the polarization direction and polarization state of light can be flexibly changed, thereby realizing dynamic regulation of the soliton state. Different soliton state distribution characteristics can be obtained by independently rotating one of the wave plates while keeping the other two wave plates stationary.

[0031] The polarization-maintaining fiber 6 introduces a significant high birefringence effect into the cavity, which enables the two polarization states outputted through the polarization-maintaining fiber to achieve approximately linear coupling, thereby triggering soliton splitting.

[0032] The output coupler 7 includes a 30% output terminal 7c and a 70% output terminal 7b.

[0033] The carbon nanotube-based saturable absorption mode-locking device 8 uses a film made of carbon nanotubes. The film is sandwiched between two optical fiber connectors and fixedly connected by a flange to select the longitudinal mode and achieve pulse narrowing.

[0034] As a specific example, Figure 2 The time domain evolution of the soliton attraction state is shown. Figure 2 (a) is the time domain evolution diagram of the stable 4-pulse soliton attraction state. Figure 2 (b) is the time domain evolution diagram of the stable 5-pulse soliton attraction state. Figure 2 (c) is the time domain evolution diagram of the stable 7-pulse soliton attraction state subjected to collision interference.

[0035] In order to verify the attraction characteristics of the multi-pulse soliton attraction state in the embodiment, Figure 3 The amplitude and pulse width of each pulse soliton in the soliton attraction state are shown. Since the soliton attraction state can attract other soliton states to evolve towards it, the amplitude and pulse width of each pulse soliton that stabilizes after evolution are consistent. Figure 3 The amplitudes in (a)-(c) are all around 0.8, and the pulse width is broadened using the pulse width dispersion formula The calculated value of the pulse width is about 377fs.

[0036] In addition, in order to verify the stability of the multi-pulse soliton attraction state, Figure 4 Shows how the pulses interact with each other. Figure 4 (a) shows the interaction between pulses III and II in the 4-pulse soliton attraction state. The results show that the phase relationship oscillates with a fixed period without divergence or irregular changes. This periodic oscillation means that the weak interaction between the pulses remains in equilibrium, allowing the phase relationship to reverberate periodically without instability. The interaction between pulses III and I and IV is basically the same as the interaction between pulses III and II. Figure 4 (b) shows the interaction between pulse V and II and IV in the 5-pulse soliton attraction state. Figure 4 (a) In addition to similar periodic oscillations, the interaction between pulses V and IV is manifested as the relative synchronization of the phases of the two pulses. They are relatively independent of each other and have weak interaction, indicating that the pulses may be in a highly stable state. Figure 4 (c) shows the interaction between pulses V and VIII in the 7-pulse soliton attraction state. The interaction diagram at the collision position appears to converge to the top of the cone and concentrate at one point, with no irregular discrete points around. This indicates that in the 7-pulse soliton attraction state, the pulses can still maintain a stable internal structure after the collision.

[0037] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A fiber laser that generates a stable soliton attraction state using a high birefringence fiber, characterized in that: The fiber laser that promotes stable soliton attraction state by high birefringence fiber includes a laser pump source, a first input end of a wavelength division multiplexer, an erbium-doped gain fiber, a polarization-independent isolator, a polarization controller, a polarization-maintaining fiber, a 70% output end of an output coupler, a carbon nanotube saturable absorber-based mode-locking device, and a second input end of the wavelength division multiplexer, and is connected in sequence through a single-mode optical fiber to form a ring laser resonant cavity.

2. The fiber laser using high birefringence fiber to promote stable soliton attraction state according to claim 1, characterized in that: The laser pump adopts 976nm band laser; the length of the erbium-doped gain fiber is 0.5m; the total length of the single-mode fiber is 18.94m; the total length of the polarization-maintaining fiber is 1.05m; the polarization controller is a three-wave plate polarization controller; the output ratio of the output coupler is 3:7; the carbon nanotube saturable absorber mode-locking device consists of two optical fiber connectors and a carbon nanotube film in the middle.

3. The fiber laser using high birefringence fiber to promote stable soliton attraction state according to claim 1, characterized in that: The laser pump has strong stability and adjustable power, and provides reliable energy support for the formation of solitons in the optical path.

4. The wavelength division multiplexer includes a first input end and a second input end, and its function is to couple the 976nm pump light with the 1550nm band light wave and input it into the resonant cavity through the input end.

5. The erbium-doped gain fiber absorbs the energy of the 980nm pump light, excites erbium ions to transition to a high-energy state, and achieves population inversion through non-radiative relaxation, ultimately generating stable and efficient light output in the 1550nm band, and together with the single-mode fiber, provides a weak birefringence effect for the resonator.

6. The polarization-maintaining optical fiber is of the panda type, and its function is to provide a high birefringence effect in the cavity.

7. The polarization controller is used to change the polarization state of the two orthogonal polarization components in the cavity. The polarization state and polarization direction of the two orthogonal polarization components obtained by the high birefringence effect in the cavity change rapidly, so that the phase of the polarization-maintaining optical fiber output is synchronized and the amplitude is close to linear coupling. Finally, under the influence of the peak power clamping effect, a multi-pulse soliton attraction state is split.

8. The polarization-independent isolator can effectively prevent the light beam from flowing back, ensure unidirectional transmission in the optical path, and provide good protection for the device.

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