Intelligent mode locking fiber laser with tunable central wavelength and intelligent mode locking method

Abstract

The invention discloses an intelligent mode-locking fiber laser with a tunable central wavelength and an intelligent mode-locking method, and relates to the technical field of lasers, the laser comprises a pumping source, a wavelength division multiplexer, a gain fiber, an intelligent mode-locking effect component, an output component, a spectrum analyzer and a computer terminal which are connected in sequence; the output component is also connected with the transmission end of the wavelength division multiplexer; the intelligent mode-locking effect assembly comprises a first electronic polarization controller, a polarization dependent isolator, a polarization maintaining optical fiber and a second electronic polarization controller which are connected in sequence. And the computer end is used for gradually adjusting the control voltages of the first electronic polarization controller and the second electronic polarization controller according to the central wavelength and bandwidth of the spectrum output by the spectrum analyzer by using a reinforcement learning method so as to realize mode locking at the target central wavelength. According to the invention, the mode-locked fiber laser realizes automatic mode locking at the required central wavelength through the intelligent mode-locking method.

Description

Technical Field

[0001] The present application relates to the field of laser technology, and in particular to an intelligent mode-locked fiber laser with tunable central wavelength and an intelligent mode-locking method. Background Art

[0002] Mode-locked fiber lasers are widely used in science, industry, and medicine due to their ability to generate stable ultrashort pulses. Traditional mode-locking control methods rely on manual adjustments or simple feedback control strategies, which are often inefficient and difficult to adapt to complex and changing operating environments. With the development of intelligent control technology, intelligent mode-locking algorithms based on deep learning and reinforcement learning have emerged. They can automatically adjust the operating state of the laser to suit different application requirements. Existing intelligent mode-locked lasers mainly focus on searching for and maintaining the mode-locked state, but have limited dynamic tuning capabilities for the central wavelength. Therefore, there is a need for a laser that can automatically mode-lock at a target central wavelength using reinforcement learning methods. Summary of the Invention

[0003] The purpose of this application is to provide an intelligent mode-locked fiber laser with tunable central wavelength and an intelligent mode-locking method, which can achieve automatic mode locking at the target central wavelength.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In a first aspect, the present application provides an intelligent mode-locked fiber laser with tunable central wavelength, comprising:

[0006] A pump source, a wavelength division multiplexer, a gain fiber, an intelligent mode-locking effect component, an output component, a spectrum analyzer, and a computer terminal are connected in sequence; the output component is also connected to the transmission end of the wavelength division multiplexer;

[0007] The intelligent mode-locking effect component includes: a first electronic polarization controller, a polarization-dependent isolator, a polarization-maintaining fiber, and a second electronic polarization controller connected in sequence; the computer end is used to use a reinforcement learning method to gradually adjust the control voltages of the first and second electronic polarization controllers according to the central wavelength and bandwidth of the spectrum output by the spectrum analyzer to achieve mode locking at the target central wavelength.

[0008] In one embodiment, the output component includes a first output coupler, a second output coupler and a jumper connector; the input end of the first output coupler is connected to the second electronic polarization controller; the first output end of the first output coupler is connected to the transmission end of a wavelength division multiplexer; the second output end of the first output coupler is connected to the input end of the second output coupler; both output ends of the second output coupler are connected to the jumper connector; one output end of the jumper connector serves as the output end of the intelligent mode-locked fiber laser, and the other output end of the jumper connector is connected to a spectrum analyzer.

[0009] In one embodiment, the gain fiber is an erbium-doped fiber with an excitation wavelength of 1530 nm-1580 nm.

[0010] In one embodiment, the gain fiber is an ytterbium-doped fiber with an excitation wavelength of 1030 nm-1064 nm.

[0011] In one embodiment, the first output coupler is a 9:1 output coupler; the first output end is a 90% output end; and the second output end is a 10% output end.

[0012] In one embodiment, the second output coupler is a 5:5 output coupler.

[0013] In one embodiment, the operating wavelengths of the wavelength division multiplexer, the first output coupler, the second output coupler, and the polarization-dependent isolator are all consistent with the excitation wavelength of the gain fiber.

[0014] In one embodiment, the jumper connector is an APC output jumper connector.

[0015] In a second aspect, the present application provides a central wavelength tunable intelligent mode-locking method, which is applied to the central wavelength tunable intelligent mode-locking fiber laser, and the intelligent mode-locking method includes:

[0016] Acquiring an output spectrum of a spectrum analyzer and extracting a central wavelength and a bandwidth of the output spectrum;

[0017] The control voltages of the first electronic polarization controller and the second electronic polarization controller are dynamically adjusted according to the central wavelength and bandwidth using the reinforcement learning method to achieve stable mode locking at the desired central wavelength.

[0018] In one embodiment, the training process of the reinforcement learning method includes multiple training stages, each training stage includes multiple training rounds;

[0019] In each training round, randomly generating a training control voltage for each training round as an initial voltage parameter; the training control voltage includes a first training control voltage and a second training control voltage;

[0020] According to the strategy of the reinforcement learning method, actions are gradually selected to act on the initial voltage parameters to gradually change the initial voltage parameters, thereby obtaining the central wavelength and bandwidth of the output spectrum after each change of the voltage parameters; the actions include incrementing or decrementing the training control voltage.

[0021] Calculating a reward value corresponding to each training round using a reward function based on the central wavelength and bandwidth of the changing output spectrum; the changing output spectrum includes an output spectrum before each change in voltage parameters and an output spectrum after each change in voltage parameters;

[0022] updating the strategy of the reinforcement learning method according to the reward value using a soft actor-critic algorithm;

[0023] The training rounds are repeated until the policy converges to a set threshold.

[0024] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0025] The present application provides an intelligent mode-locked fiber laser with tunable central wavelength and an intelligent mode-locking method. An intelligent mode-locking effect component, a spectrum analyzer, and a controller are provided in a conventional laser. The intelligent mode-locking effect component includes a first electronic polarization controller, a polarization-dependent isolator, a polarization-maintaining fiber, and a second electronic polarization controller connected in sequence. A computer uses a reinforcement learning method to adjust the control voltages of the first and second electronic polarization controllers of the intelligent mode-locking effect component. By adjusting the control voltages of the two voltage polarization controllers, the output spectrum is changed to achieve automatic mode locking. The first electronic polarization controller, the polarization-dependent isolator, and the second electronic polarization controller form a nonlinear polarization rotation structure to provide a mode-locking effect. The polarization-dependent isolator, the polarization-maintaining fiber, and the second electronic polarization controller form a Lyot filter, which allows the central wavelength of the mode-locked light to be tuned. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1This is a schematic structural diagram of an intelligent mode-locked fiber laser with tunable central wavelength in one embodiment of the present application.

[0028] Figure numerals: 1-pump source, 2-wavelength division multiplexer, 3-gain fiber, 4-first electronic polarization controller, 5-polarization dependent isolator, 6-polarization maintaining fiber, 7-second electronic polarization controller, 8-9:1 output coupler, 9-5:5 output coupler, 10-APC output jumper head, 11-spectrum analyzer, 12-computer terminal. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0030] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0031] Existing intelligent mode-locked lasers primarily focus on searching for and maintaining a stable mode-locked state, but have limited dynamic tuning capabilities for the center wavelength. Many applications, such as spectral analysis, optical communications, and biomedical imaging, place stringent requirements on the center wavelength of laser pulses, necessitating an intelligent mode-locked laser capable of precise, real-time adjustment of the center wavelength. This application provides an intelligent mode-locked fiber laser with a tunable center wavelength. This laser not only achieves automatic mode locking but also possesses the ability to automatically mode lock at any center wavelength within the tuning range, thereby improving the stability of the mode-locked fiber laser.

[0032] like Figure 1 As shown, the present application provides an intelligent mode-locked fiber laser with tunable central wavelength, comprising: a pump source 1, a wavelength division multiplexer 2, a gain fiber 3, an intelligent mode-locked effect component, an output component, a spectrum analyzer 11 and a computer terminal 12 connected in sequence; the output component is also connected to the transmission end of the wavelength division multiplexer 2; the intelligent mode-locked effect component comprises: a first electronic polarization controller 4, a polarization-dependent isolator 5, a polarization-maintaining fiber 6 and a second electronic polarization controller 7 connected in sequence; the computer terminal is used to analyze the central wavelength and bandwidth of the output spectrum of the spectrum analyzer 11 using a reinforcement learning method and gradually adjust the control voltages of the first electronic polarization controller 4 and the second electronic polarization controller 7 to achieve mode locking at the target central wavelength.

[0033] The laser described above can automatically adjust the voltage of the electronic polarization controller, thereby finely controlling the polarization state of the light field within the laser cavity to achieve mode locking at the target center wavelength. Compared with existing technologies, the laser of this application not only automatically achieves mode locking, but also has the ability to automatically mode lock at any center wavelength within the tuning range, significantly improving the laser's flexibility and application range.

[0034] In an exemplary embodiment, the output component includes a first output coupler, a second output coupler and two jumper connectors; the input end of the first output coupler is connected to the second electronic polarization controller 7; the first output end of the first output coupler is connected to the transmission end of the wavelength division multiplexer 2; the second output end of the first output coupler is connected to the input end of the second output coupler; both output ends of the second output coupler are connected to the jumper connectors; the output end of one of the jumper connectors serves as the output end of the intelligent mode-locked fiber laser, and the output end of the other jumper connector is connected to the spectrum analyzer 11.

[0035] In practical applications, the first output coupler is a 9:1 output coupler 8 , the first output end is a 90% output end, the second output end is a 10% output end, and the second output coupler is a 5:5 output coupler 9 .

[0036] In this application, the ring cavity assembly includes: a standard single-mode fiber, a gain fiber 3, an intelligent mode-locking effect component, a wavelength division multiplexer 2, and a 9:1 output coupler 8. The pump source 1 is connected to the ring cavity assembly. The ring cavity components are connected by a single-mode fiber that transmits in the corresponding wavelength band.

[0037] In an exemplary embodiment, the gain fiber 3 is an erbium-doped fiber with an excitation wavelength of 1530 nm-1580 nm.

[0038] In another exemplary embodiment, the gain fiber 3 is an ytterbium-doped fiber with an excitation wavelength of 1030 nm-1064 nm.

[0039] In an exemplary embodiment, the operating wavelengths of the wavelength division multiplexer 2 , the first output coupler, the second output coupler, and the polarization-dependent isolator 5 are all consistent with the excitation wavelength of the gain fiber 3 .

[0040] In an exemplary embodiment, the jumper connector is an APC output jumper connector 10 , and the APC output jumper connector 10 is an angled physical contact (APC) output jumper connector.

[0041] In an exemplary embodiment, the present application also provides specific connections of various devices in a central wavelength tunable intelligent mode-locked fiber laser, wherein the reflection end of the wavelength division multiplexer 2 is connected to the pump source 1; the common end of the wavelength division multiplexer 2 is connected to one end of the gain fiber 3; the other end of the gain fiber 3 is connected to one end of the intelligent mode-locking effect component; the intelligent mode-locking effect component is used to provide saturable absorption effect and filtering effect; the other end of the intelligent mode-locking effect component is connected to the input end of the 9:1 output coupler 8; the 90% output end of the 9:1 output coupler 8 is connected to the transmission end of the wavelength division multiplexer 2; the 10% output end of the 9:1 output coupler 8, as the output end of the ring cavity, is connected to the input end of the 5:5 output coupler 9; the other two ends of the 5:5 output coupler 9 are connected to the APC output jumper head 10; any one of them is connected to the spectrum analyzer 11, and the spectrum analyzer 11 is connected to the computer terminal 12 through the network interface; the output light of the other APC output jumper head 10 will be used as the final output light; the soft The actor-critic reinforcement learning method enables the laser to output stable and intelligently tunable mode-locked light.

[0042] The intelligent mode-locking effect component includes: a first electronic polarization controller 4, a polarization-dependent isolator 5, a polarization-maintaining fiber 6, and a second electronic polarization controller 7. The polarization-dependent isolator 5 is connected to the other end of the gain fiber 3, the first electronic polarization controller 4 is placed between the polarization-dependent isolator 5 and the gain fiber 3, the other end of the polarization-dependent isolator 5 is connected to one end of the polarization-maintaining fiber 6, the other end of the polarization-maintaining fiber 6 is connected to a 9:1 output coupler 8, and the second electronic polarization controller 7 is placed between the polarization-maintaining fiber 6 and the 9:1 output coupler 8. The first and second electronic polarization controllers 4 and 7 are connected to a computer terminal 12 via a network interface.

[0043] In practical applications, the computer terminal 12 uses a soft actor-critic reinforcement learning method to analyze spectral information and adjusts the polarization state of the light in the cavity according to the desired center wavelength by changing the control voltage of the first electronic polarization controller 4 and the second electronic polarization controller 7 to achieve stable mode locking at the desired center wavelength.

[0044] The tuning working principle of the intelligent mode-locked laser is that the first electronic polarization controller 4, the polarization-dependent isolator 5, and the second electronic polarization controller 7 constitute a nonlinear polarization rotation structure to provide a mode-locking effect; in addition, the polarization-dependent isolator 5, the polarization-maintaining fiber 6, and the second electronic polarization controller 7 constitute a Lyot filter, so that the center wavelength of the mode-locked light can be tuned; the soft actor-critic deep reinforcement learning method deployed in the computer terminal 12 can analyze the spectral information collected by the spectrum analyzer 11, and adjust the polarization state of the light in the cavity according to the required center wavelength by changing the control voltage of the first electronic polarization controller 4 and the second electronic polarization controller 7 to achieve stable mode locking at the required center wavelength.

[0045] The present application provides an intelligent mode-locked fiber laser with tunable central wavelength, the technical advantage of which lies in the use of reinforcement learning technology to achieve adaptive control of the laser system. Specifically, through the interaction between the intelligent agent and the laser system, the laser of the present application can automatically adjust the voltage of the electronic polarization controller, thereby finely regulating the polarization state of the light field in the laser cavity to achieve mode locking at the target central wavelength. Compared with the prior art, the laser of the present application can not only automatically achieve mode locking operation, but also has the ability to automatically lock the mode at any central wavelength within the tuning range, significantly improving the flexibility and application range of the laser. This intelligent control mechanism enables the laser to respond quickly to different working conditions and achieve efficient and stable mode-locked output, while maintaining the simplicity of operation and the robustness of the system.

[0046] In another exemplary embodiment, a method for intelligent mode-locking with tunable center wavelength is provided. The method is applied to the aforementioned intelligent mode-locked fiber laser with tunable center wavelength. The method comprises: obtaining an output spectrum from an optical spectrum analyzer and extracting the center wavelength and bandwidth of the output spectrum; and dynamically adjusting the control voltages of a first electronic polarization controller and a second electronic polarization controller based on the center wavelength and bandwidth using the reinforcement learning method to achieve stable mode-locking at a desired center wavelength. Specifically, the soft actor-critic deep reinforcement learning method is used to analyze spectral information and extract the center wavelength and bandwidth of the output spectrum. Based on the desired center wavelength, the soft actor-critic agent adjusts the polarization state of the light in the cavity by continuously changing the control voltages of the first and second electronic polarization controllers to achieve stable mode-locking at the desired center wavelength.

[0047] In an exemplary embodiment, the training process of the reinforcement learning method includes multiple training stages, each training stage including multiple training rounds; in each training round, a training control voltage for each training round is randomly generated as an initial voltage parameter; the training control voltage includes a first training control voltage and a second training control voltage; according to the strategy of the reinforcement learning method, actions are gradually selected to act on the initial voltage parameter to gradually change the initial voltage parameter, thereby obtaining the center wavelength and bandwidth of the output spectrum after each voltage parameter change; the actions include incrementing or decrementing the training control voltage; based on the center wavelength and bandwidth of the changed output spectrum, a reward value corresponding to the training round is calculated using a reward function; the changed output spectrum includes the output spectrum before each voltage parameter change and the output spectrum after each voltage parameter change; the strategy of the reinforcement learning method is updated using a soft actor-critic algorithm based on the reward value; and the training rounds are repeated until the strategy converges to a set threshold.

[0048] Agent, environment, strategy, and reward are all related concepts of reinforcement learning. The agent refers to the reinforcement learning algorithm module running on the PC, specifically the implementation part of the soft actor-critic algorithm, which is used to select actions based on the state of the environment. The environment refers to the physical system composed of the intelligent mode-locked fiber laser system and its related components. The state of the environment is represented by the spectral data (such as central wavelength and bandwidth) output by the spectrum analyzer. When the agent performs actions (such as adjusting the control voltage), the environment will change according to these actions and generate a new state (i.e., new spectral data). The feedback from the environment includes the new spectral data and the reward value calculated according to the reward function. The strategy refers to the rule or function for the agent to select actions based on the current state of the environment. It is defined and optimized by the soft actor-critic algorithm, with the goal of maximizing the cumulative reward value.

[0049] The corresponding reward value is determined based on the center wavelength and bandwidth of the spectrum before and after the change. The specific expression is:

[0050] R(λ t ,Δλ t )=-w1|λ t -λ target | 2 +w2R(Δλ t )

[0051]

[0052] Among them, w1 and w2 are scale factors, λ target is the target center wavelength, λ t is the central wavelength of the current step spectrum, Δλ tis the 3dB bandwidth of the current step spectrum, ReLU(·) is the activation function commonly used in deep learning, R(·) is the bandwidth reward value, Δλ G is Δλ t The threshold value, when Δλ t <Δλ G , the laser system is considered to be free running when Δλ t ≥Δλ G When w1, w2, α, Δλ G is a hyperparameter and t is the current step.

[0053] In practical applications, the reinforcement learning method trained at one central wavelength is fine-tuned through transfer learning and applied to other central wavelengths to reduce training time.

[0054] The transfer learning steps include:

[0055] When the target central wavelength changes, the target wavelength parameter in the reward function is updated according to the changed target central wavelength.

[0056] Save and reuse the reinforcement learning policy trained at any center wavelength.

[0057] Based on the updated reward function and the adopted strategy, further training is performed on the changed target center wavelength.

[0058] By reusing the trained reinforcement learning policy, the number of training rounds for the new target center wavelength is reduced, thereby reducing the training time.

[0059] The present application can not only realize automatic mode locking, but also has the ability to automatically mode lock at any central wavelength within the tuning range, thereby improving the stability of the mode-locked fiber laser.

[0060] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0061] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. An intelligent mode-locked fiber laser with tunable central wavelength, characterized in that: The central wavelength tunable intelligent mode-locked fiber laser comprises: a pump source, a wavelength division multiplexer, a gain fiber, an intelligent mode-locked effect component, an output component, a spectrum analyzer and a computer terminal connected in sequence; the output component is also connected to the transmission end of the wavelength division multiplexer; The intelligent mode-locking effect component includes: a first electronic polarization controller, a polarization-dependent isolator, a polarization-maintaining fiber, and a second electronic polarization controller connected in sequence; the computer end is used to use a reinforcement learning method to gradually adjust the control voltages of the first and second electronic polarization controllers according to the central wavelength and bandwidth of the spectrum output by the spectrum analyzer to achieve mode locking at the target central wavelength.

2. The central wavelength tunable intelligent mode-locked fiber laser according to claim 1, characterized in that: The output component includes a first output coupler, a second output coupler and two jumper connectors; the input end of the first output coupler is connected to the second electronic polarization controller; the first output end of the first output coupler is connected to the transmission end of the wavelength division multiplexer; the second output end of the first output coupler is connected to the input end of the second output coupler; both output ends of the second output coupler are connected to the jumper connectors; the output end of one of the jumper connectors serves as the output end of the intelligent mode-locked fiber laser, and the output end of the other jumper connector is connected to a spectrum analyzer.

3. The central wavelength tunable intelligent mode-locked fiber laser according to claim 1, characterized in that: The gain optical fiber is an erbium-doped optical fiber with an excitation wavelength of 1530nm-1580nm.

4. The central wavelength tunable intelligent mode-locked fiber laser according to claim 1, characterized in that: The gain optical fiber is an ytterbium-doped optical fiber with an excitation wavelength of 1030nm-1064nm.

5. The central wavelength tunable intelligent mode-locked fiber laser according to claim 2, characterized in that: The first output coupler is a 9:1 output coupler; the first output end is a 90% output end; and the second output end is a 10% output end.

6. The central wavelength tunable intelligent mode-locked fiber laser according to claim 2, characterized in that: The second output coupler is a 5:5 output coupler.

7. The central wavelength tunable intelligent mode-locked fiber laser according to claim 2, characterized in that: The operating wavelengths of the wavelength division multiplexer, the first output coupler, the second output coupler and the polarization-dependent isolator are all consistent with the excitation wavelength of the gain optical fiber.

8. The central wavelength tunable intelligent mode-locked fiber laser according to claim 2, characterized in that: The jumper connector is an APC output jumper connector.

9. An intelligent mode-locking method with tunable central wavelength, characterized in that: The central wavelength tunable intelligent mode-locking method is applied to the central wavelength tunable intelligent mode-locking fiber laser according to any one of claims 1 to 8, and the intelligent mode-locking method comprises: Acquiring an output spectrum of a spectrum analyzer and extracting a central wavelength and a bandwidth of the output spectrum; The control voltages of the first electronic polarization controller and the second electronic polarization controller are dynamically adjusted according to the central wavelength and bandwidth using the reinforcement learning method to achieve stable mode locking at the desired central wavelength.

10. The intelligent mode-locking method with tunable central wavelength according to claim 9, characterized in that: The training process of the reinforcement learning method includes multiple training stages, each training stage includes multiple training rounds; In each training round, randomly generating a training control voltage for each training round as an initial voltage parameter; the training control voltage includes a first training control voltage and a second training control voltage; According to the strategy of the reinforcement learning method, actions are gradually selected to act on the initial voltage parameters to gradually change the initial voltage parameters, thereby obtaining the central wavelength and bandwidth of the output spectrum after each change of the voltage parameters; the actions include incrementing or decrementing the training control voltage. Calculating a reward value corresponding to each training round using a reward function based on the central wavelength and bandwidth of the changing output spectrum; the changing output spectrum includes an output spectrum before each change in voltage parameters and an output spectrum after each change in voltage parameters; updating the strategy of the reinforcement learning method according to the reward value using a soft actor-critic algorithm; The training rounds are repeated until the policy converges to a set threshold.

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