Intelligent spatiotemporal mode-locked fiber laser and control method

Abstract

This invention discloses an intelligent spatiotemporally mode-locked fiber laser and its control method. The intelligent spatiotemporally mode-locked fiber laser includes: an all-fiber momentum space modulation device, which is used to control the spatial mode field distribution; the all-fiber momentum space modulation device includes: a momentum space random control device and an intelligent feedback control device; the momentum space random control device and the intelligent feedback control device are connected; the momentum space random control device is used to obtain an arbitrary mode field distribution in the coordinate space of the multimode fiber; the intelligent feedback control device is used to obtain a specific mode field distribution in the spatiotemporally mode-locked state of the multimode fiber. By obtaining an arbitrary mode field distribution in the coordinate space through the momentum space random control device and finding the specific mode field distribution in the spatiotemporally mode-locked state of the multimode fiber through the intelligent feedback control device, the spatial mode field distribution can be accurately controlled, achieving the effect of simultaneous spatiotemporal mode locking.

Description

Technical Field

[0001] This invention relates to the field of fiber laser technology, and in particular to an intelligent spatiotemporal mode-locked fiber laser and its control method. Background Technology

[0002] Mode-locked lasers are a crucial means of obtaining high-energy, ultra-narrow pulses, and currently have important applications in laser processing, medical imaging, communications, and military fields. Compared to traditional single-mode fiber mode-locked lasers, spatiotemporally mode-locked fiber lasers based on multimode fibers have a larger mode field area. Theoretical studies show that the output pulse energy of multimode fiber lasers is three orders of magnitude higher than that of single-mode fiber lasers, making them an ideal choice for obtaining high-energy, ultrashort pulses. Furthermore, because multimode fibers simultaneously possess multiple transverse mode distributions, they offer greater spatial freedom. Therefore, this type of fiber laser can be widely used in various fields such as industrial precision machining, optical communication, high-precision sensing, detection, and military applications.

[0003] Spatiotemporally mode-locked fiber lasers employ multimode fiber, requiring simultaneous locking of transverse modes while locking longitudinal modes; this necessitates precise control over the spatial distribution of the laser. Therefore, accurately controlling the spatial modes and simultaneously locking both temporal and spatial modes is crucial for achieving multimode mode-locked spatiotemporal fiber lasers. Current methods for spatial mode control typically utilize spatial filters: for spatial light fiber lasers, small apertures are placed in the spatial region, eliminating some transverse mode components depending on their placement. For all-fiber fiber lasers, methods such as different numerical apertures and staggered fusion splicing are used to eliminate some transverse modes. However, these existing methods only eliminate some transverse mode components through the coordinate space dimension, failing to accurately select the mode and introducing significant additional losses to the system, resulting in low pulse energy.

[0004] Therefore, existing technologies still need to be developed and improved. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide an intelligent spatiotemporal mode-locked fiber laser and a control method to solve the problem that existing spatiotemporal mode-locked fiber lasers cannot accurately control the spatial mode field distribution.

[0006] The present invention is achieved through the following technical solution: a smart spatiotemporal mode-locked fiber laser, wherein the smart spatiotemporal mode-locked fiber laser is a multimode fiber laser with an optical resonant cavity structure, comprising: an all-fiber momentum space modulation device, wherein the all-fiber momentum space modulation device is connected to the optical resonant cavity structure, and the all-fiber momentum space modulation device is used to control the spatial mode field distribution.

[0007] The all-fiber momentum space modulation device includes: a momentum space random modulation device and an intelligent feedback control device;

[0008] The momentum space random control device and the intelligent feedback control device are connected;

[0009] The momentum space random control device is used to obtain a mode field distribution of arbitrary shape in the coordinate space of a multimode fiber.

[0010] The intelligent feedback control device is used to obtain the specific mode field distribution of the spatiotemporal mode-locked state of the multimode fiber.

[0011] In a further embodiment of the present invention, the optical resonant cavity structure is a ring cavity circuit, and the intelligent spatiotemporal mode-locked fiber laser further includes: a multimode fiber pump source, a multimode pump connector, a few-mode gain fiber, a passive graded-index fiber, a multimode fiber optical isolator, a saturable absorber, a multimode fiber coupler, and a multimode fiber filter.

[0012] The multimode fiber pump source is connected to the multimode pump connector, and the multimode fiber pump source is used to excite the laser working medium.

[0013] The multimode pump connector is used to couple the light and signal emitted by the multimode fiber pump source into the ring cavity circuit;

[0014] The few-mode gain fiber is used to generate a one-micron wavelength laser through light emitted from the multimode fiber pump source via the gain material.

[0015] The passive graded-index fiber is used to reduce intermodal dispersion.

[0016] The multimode fiber optical isolator is used to ensure unidirectional transmission of laser light in the ring cavity circuit;

[0017] The saturable absorber is used to achieve time-domain mode locking;

[0018] The multimode fiber coupler is used to couple a portion of the laser output from the ring cavity circuit.

[0019] The multimode fiber filter is used for time-domain filtering of the laser in the ring cavity circuit.

[0020] In a further embodiment of the present invention, the intelligent feedback control device includes an intelligent feedback algorithm module;

[0021] The intelligent feedback algorithm module obtains a set of specific modulus field distributions that satisfy the spatiotemporal modulus-locking state through a global optimization algorithm, and the intelligent feedback algorithm module repeatedly learns the set of specific modulus field distributions that satisfy the spatiotemporal modulus-locking state through artificial intelligence.

[0022] In a further embodiment of the present invention, the intelligent feedback control device further includes: a knob control module;

[0023] The knob control module is used to lock the specific modulus field distribution of the spatiotemporal modulus-locking state manually or through the intelligent feedback algorithm module.

[0024] In a further embodiment of the present invention, the all-fiber momentum space modulation device further includes: a monitoring output device;

[0025] The monitoring output device is connected to the all-fiber momentum space modulation device and the intelligent feedback control device, respectively. The monitoring output device is used to monitor the intracavity state of the all-fiber momentum space modulation device and output a signal to the intelligent feedback control device.

[0026] In a further embodiment of the present invention, the multimode fiber pump source, the multimode pump connector, the few-mode gain fiber, the passive graded-index fiber, the all-fiber momentum space modulation device, the multimode fiber optical isolator, the saturable absorber, the multimode fiber coupler, and the multimode fiber filter are sequentially connected to form a ring cavity circuit.

[0027] In a further embodiment of the present invention, the momentum space random control device obtains a mode field distribution of arbitrary shape in the coordinate space of the multimode fiber by changing the geometry of the multimode fiber.

[0028] In a further embodiment of the present invention, the saturable absorbent is an artificial saturable absorbent or a natural saturable absorbent.

[0029] In a further embodiment of the present invention, the few-mode gain fiber is a step-index doped rare-earth element fiber and ytterbium-doped fiber is used as the laser gain medium.

[0030] Based on the same inventive concept, the present invention also provides a control method for the above-described intelligent spatiotemporal mode-locked fiber laser, which includes the following steps:

[0031] The mode field distribution of arbitrary shape in the coordinate space of multimode fiber can be obtained by using momentum space random control devices.

[0032] The specific mode field distribution of the spatiotemporal mode-locked state of the multimode fiber is obtained through an intelligent feedback control device.

[0033] The beneficial effects of this invention are:

[0034] This invention provides an intelligent spatiotemporally mode-locked fiber laser and a control method. The intelligent spatiotemporally mode-locked fiber laser includes: an all-fiber momentum space modulation device, which is used to control the spatial mode field distribution. Accurate control of the spatial mode field distribution is achieved through the all-fiber momentum space modulation device, realizing the effect of spatiotemporal mode-locking. The all-fiber momentum space modulation device includes: a momentum space random control device and an intelligent feedback control device; the momentum space random control device and the intelligent feedback control device are connected. The momentum space random control device is used to obtain an arbitrary mode field distribution in the multimode fiber coordinate space. Any spatial control state can be obtained solely through the momentum space random control device, achieving a flexible effect. The intelligent feedback control device is used to obtain a specific mode field distribution of the spatiotemporally mode-locked state of the multimode fiber. After obtaining an arbitrary spatial control state, the specific mode field distribution can be obtained through the intelligent feedback control device, achieving the effect of accurately controlling the spatial mode field distribution.

[0035] First, the mode field distribution of arbitrary shape in coordinate space is obtained through momentum space random control device. Then, the specific mode field distribution of the spatiotemporal mode-locked state of multimode fiber is found through intelligent feedback control device. Finally, the spatial mode field distribution can be precisely controlled to achieve simultaneous locking of time mode and spatial mode, and obtain stable and reliable high-energy ultrashort pulse output. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a preferred embodiment of an intelligent spatiotemporal mode-locked fiber laser provided by the present invention.

[0037] Figure 2 This is a schematic diagram illustrating the principle and structure of the winding control method.

[0038] Figure 3 This is a structural diagram illustrating the principle of the stretching and extrusion control method.

[0039] Figure 4 This is a schematic diagram illustrating the principle and structure of a local heating control method.

[0040] Figure 5 for Figure 1 Flowchart of the determination procedure when entering spacetime locking mode.

[0041] Figure 6 The schematic diagram of the linear structure of another embodiment of the intelligent spatiotemporal mode-locked fiber laser provided by the present invention is shown.

[0042] Figure 7 This is a flowchart of a preferred embodiment of a control method provided by the present invention.

[0043] Explanation of main component symbols

[0044] 100. Intelligent spatiotemporal mode-locked fiber laser; 10. Multimode fiber pump source; 20. Multimode pump connector; 30. Few-mode gain fiber; 40. Passive graded-index fiber; 50. All-fiber momentum space modulation device; 60. Multimode fiber optical isolator; 70. Saturable absorber; 80. Multimode fiber coupler; 90. Multimode fiber filter; 51. Momentum space random modulation device; 52. Intelligent feedback control device; 53. Monitoring output device; 521. Intelligent feedback algorithm module; 522. Knob control module. Detailed Implementation

[0045] This invention provides a preferred embodiment of an intelligent spatiotemporal mode-locked fiber laser and its control method, applicable to the field of fiber laser technology. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] In the implementation methods and the scope of the patent application, unless otherwise specified in the text, “a” and “the” may refer to a single or multiple entities.

[0047] Furthermore, if the embodiments of the present invention involve descriptions such as "first" or "second," such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature.

[0048] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0049] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0050] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0051] Example

[0052] This invention provides a preferred embodiment of an intelligent spatiotemporal mode-locked fiber laser, such as... Figure 1 As shown, the intelligent spatiotemporal mode-locked fiber laser 100 provided in a preferred embodiment of the present invention employs multimode fiber and is a multimode fiber laser with an optical resonant cavity structure. The optical resonant cavity structure includes a linear cavity loop structure and a ring cavity loop structure. The intelligent spatiotemporal mode-locked fiber laser 100 includes: a multimode fiber pump source 10, a multimode pump connector 20, a few-mode gain fiber 30, a passive graded-index fiber 40, an all-fiber momentum spatial modulation device 50, a multimode fiber optical isolator 60, a saturable absorber 70, a multimode fiber coupler 80, and a multimode fiber filter 90, arranged sequentially along the light propagation direction. The all-fiber momentum spatial modulation device 50 in the intelligent spatiotemporal mode-locked fiber laser 100 is used to control the spatial mode field distribution of the multimode fiber to achieve simultaneous locking of the spatiotemporal modes (i.e., time mode and spatial mode) in the multimode fiber laser, thereby obtaining high-energy and stable pulse output.

[0053] Please continue reading. Figure 1 In this preferred embodiment, the all-fiber momentum space modulation device 50 is an all-fiber, flexible space modulation device, comprising: a momentum space random control device 51 and an intelligent feedback control device 52; the momentum space random control device 51 and the intelligent feedback control device 52 are connected; the momentum space random control device 51 is used to obtain a mode field distribution of arbitrary shape in the coordinate space of the multimode fiber; the intelligent feedback control device 52 is used to obtain a specific mode field distribution of the spatiotemporal mode-locked state of the multimode fiber, so as to accurately control the spatial mode field distribution and realize the simultaneous locking of the spatiotemporal modes, i.e., the time mode and the spatial mode, in the multimode fiber laser.

[0054] The momentum space random control device 51 is a momentum space random control device 51 based on multimode fiber, which can be a step-index multimode fiber or a graded-index multimode fiber.

[0055] Please continue reading. Figure 1In this preferred embodiment, the intelligent spatiotemporal mode-locked fiber laser 100 has a ring cavity circuit, that is, the optical resonant cavity structure is a ring cavity circuit. The multimode fiber pump source 10, the multimode pump connector 20, the few-mode gain fiber 30, the passive graded-index fiber 40, the all-fiber momentum space modulation device 50, the multimode fiber optical isolator 60, the saturable absorber 70, the multimode fiber coupler 80, and the multimode fiber filter 90 are sequentially connected to form a fiber ring cavity circuit.

[0056] In other embodiments, such as Figure 6 As shown, the intelligent spatiotemporal mode-locked fiber laser 100 can also be configured as a linear cavity structure, that is, the optical resonant cavity structure is a linear cavity structure, and the multimode fiber pump source 10, the multimode pump connector 20, the multimode fiber coupler 80, the few-mode gain fiber 30, the all-fiber momentum space modulation device 50 and the multimode fiber filter 90 are connected sequentially along the direction of light propagation.

[0057] Please continue reading for more details. Figure 1In this preferred embodiment, the multimode fiber pump source 10 is connected to the multimode pump connector 20. The multimode fiber pump source 10 is used to excite the laser working medium. The multimode pump connector 20 is used to couple the light and signal emitted by the multimode fiber pump source 10 into the ring cavity circuit. The few-mode gain fiber 30 is used to excite a one-micron wavelength laser through the gain medium by the light emitted by the multimode fiber pump source 10. The passive graded-index fiber 40 is used to reduce intermodal dispersion. The multimode fiber optical isolator 60 is used to ensure unidirectional transmission of the laser in the ring cavity circuit. The saturable absorber 70 is used to achieve time-domain mode locking. The multimode fiber coupler 80 is used to couple a portion of the laser output from the ring cavity circuit. The multimode fiber filter 90 is used to perform time-domain filtering on the laser in the ring cavity circuit. In this preferred embodiment, the multimode fiber pump source 10 pumps the few-mode gain fiber 30 in the ring cavity circuit through the multimode pump connector 20 to generate a one-micron wavelength laser. Without any control, the intelligent spatiotemporally mode-locked fiber laser 100 is in a continuous optical pulse output state. Furthermore, due to the different group velocities of different propagation modes, the fiber ends reach the fiber at different times, resulting in intermodal dispersion. Therefore, the passive graded-index fiber 40 is provided to reduce intermodal dispersion. The all-fiber momentum spatial modulation device 50 is connected to the tail of the colorless refractive index fiber. After controlling the spatial mode field distribution, it passes through the multimode fiber optical isolator 60 and the saturable absorber 70 to complete the time-domain mode locking. The saturable absorber 70 is a device whose transmittance is related to light intensity, with low loss in the high-intensity portion and high loss in the low-intensity portion. Specifically, the saturable absorber 70 can be an artificial saturable absorber 70 based on nonlinear polarization rotation effect, nonlinear fiber environment, etc., or a natural saturable absorber 70 based on semiconductor saturable absorber mirror (SESEAM), carbon nanotubes, novel two-dimensional materials (graphene, black phosphorus, etc.). In addition, in other embodiments, the placement position of the saturable absorber 70 can be adjusted. The saturable absorber 70 can be placed at both ends of the few-mode gain fiber 30, or it can be placed in the passive fiber, i.e., the passive graded-index fiber 40. Subsequently, the laser output from the multimode fiber coupler 80 is used for measurement and observation. In this embodiment, the multimode fiber coupler 80 has a 7:3 coupling output, meaning that 30% of the laser is used for output, while the remaining 70% of the laser continues to circulate in the ring cavity circuit and remains stable within the cavity. Afterward, the laser passes through the multimode fiber filter 90 for time-domain filtering to ensure that the pulse is periodically weakened and re-enters the cycle.In addition, the multimode fiber optical isolator 60 is connected to the ring cavity circuit. The multimode fiber optical isolator 60 is a polarization-dependent isolator. The multimode fiber optical isolator 60 is connected to the saturable absorber 70 and the multimode fiber coupler 80 respectively to ensure unidirectional transmission of laser within the ring cavity circuit structure.

[0058] Furthermore, in other embodiments, the all-fiber momentum spatial modulation device 50 can also be used as a saturable absorber 70 to generate a saturable absorption effect in the time domain, playing a key role in pulse formation. When a pulse passes through the saturable absorber 70, the high-energy portion of the pulse is completely transmitted, while the low-energy portion cannot be transmitted, thus narrowing the pulse after it passes through the saturable absorber 70.

[0059] For further information, please refer to [link / reference]. Figure 1 In this preferred embodiment, the few-mode gain fiber 30 is a step-index doped rare-earth fiber with ytterbium-doped fiber as the laser gain medium. Furthermore, the length of the few-mode gain fiber 30 is adjusted according to high or low doping levels; in this preferred embodiment, the length of the few-mode gain fiber 30 is described as 2 meters.

[0060] Please continue reading. Figure 1 In this preferred embodiment, when the laser enters the momentum space random control device 51, the wavefront of the incident light is decomposed into multiple orthogonal modes in momentum space. The multimode fiber, acting as a converter from coordinate space to momentum space, alters the phase and amplitude of these orthogonal modes by changing the fiber's geometry, thereby achieving random perturbation of the phase and amplitude of the mode field within the multimode fiber, and ultimately obtaining a mode field distribution of arbitrary shape in coordinate space. Specifically, mechanical control methods can be used to change the geometry, for example... Figure 2 As shown, a multi-propeller coupled controller is used to achieve random control of momentum space by winding multimode fiber. Multiple orthogonal spatial modes propagate within the multimode fiber, decomposing the wavefront of the incident light signal into multiple orthogonal modes. The multimode fiber acts as a converter from coordinate space to momentum space. Coupling from one mode to another is achieved through geometric changes, and each propeller can create its own degree of freedom. Furthermore, other methods can be employed... Figure 3 and 4 The method shown involves using compression, stretching, local heating, or other mechanical manipulation techniques, or any other method that alters the geometry of the multimode fiber, to induce geometric changes such as bending, twisting, and extrusion, resulting in a mode field distribution of arbitrary shape in coordinate space, thus achieving random control of momentum space. Furthermore, the momentum space random control device 51 can also function as a spatial filter.

[0061] Subsequently, in order to obtain the desired specific mode field distribution and thus achieve spatiotemporal mode locking, the intelligent feedback control device 52 is provided to regulate the mode field distribution of arbitrary shapes to obtain a specific mode field distribution of the spatiotemporal mode-locked state of the multimode fiber. Furthermore, for ease of regulation, a monitoring device is needed to monitor the intelligent feedback control device 52. Therefore, in this preferred embodiment, the all-fiber momentum space modulation device 50 is also provided with a monitoring output device 53. The monitoring output device 53 is connected to both the all-fiber momentum space modulation device 50 and the intelligent feedback control device 52. The monitoring output device 53 is used to monitor the intracavity state of the all-fiber momentum space modulation device 50 and output a signal to the intelligent feedback control device 52. This intracavity state includes the continuous light state without spatiotemporal locking, and the single-pulse state and bound state under the locked state, etc. The monitoring output device 53 is an all-fiber monitoring output device, which can be an optical fiber coupled output device with a coupling-to-output ratio of 99:1.

[0062] Specifically, after obtaining a mode field distribution of arbitrary shape in coordinate space and realizing momentum space random control, the monitoring output device 53 transmits the random mode field distribution signal generated by the momentum space random control device 51 to the intelligent feedback control device 52. The intelligent feedback control device 52 has an intelligent feedback algorithm module 521. The intelligent feedback algorithm module 521 receives and processes the random mode field distribution signal, analyzes the characteristics of the signal through a global optimization algorithm, such as optical power signal, signal voltage value, pulse repetition frequency stability, output pulse energy, and output spectral shape, to obtain a specific mode field distribution set that satisfies the spatiotemporal mode-locking state, i.e., the optimal solution set that satisfies the spatiotemporal mode-locking state. This set can be a single-pulse output, a bound state, a multi-pulse output, etc. Furthermore, the intelligent feedback algorithm module 521 repeatedly learns the obtained specific mode field distribution set of the spatiotemporal mode-locking state through artificial intelligence, i.e., an artificial intelligence system, to complete the entire process. Through repeated learning, the spatiotemporal mode-locking time can be shortened, and the momentum space random control device 51 can generate memory, improving the spatiotemporal mode-locking efficiency. In addition, the intelligent feedback control device 52 further includes a knob control module 522; the knob control module 522 is electrically connected to the intelligent feedback algorithm module 521, and the knob control module 522 is equipped with a cable connected to the intelligent feedback algorithm module 521, allowing the knob control module to be turned via the cable; the knob control module 522 is used to lock the specific mode field distribution of the spatiotemporal mode-locked state manually or by the intelligent feedback algorithm module 521, to achieve the effect of precise control of the spatial mode field, that is, the specific mode field distribution of the spatiotemporal mode-locked state is locked by the knob control module 522 turned by the intelligent feedback algorithm module 521 or by manually turning the knob control module 522, so as to accurately control the spatial mode field distribution and ultimately obtain a stable high-energy ultrashort pulse output; wherein, under normal conditions, the locking is performed by the intelligent feedback algorithm module 521, and in some specific environments, such as when components are damaged, the locking can be performed manually to deal with emergency situations. In addition, the intelligent feedback algorithm module 521 can be a field-programmable gate array or a microcontroller, etc.

[0063] For further information, please refer to [link / reference]. Figure 1In this preferred embodiment, the intelligent spatiotemporally mode-locked fiber laser 100 is a ring-shaped circuit with a total length of approximately 8 meters. The laser output from the coupler 80 is measured using a spectrometer and oscilloscope, and the beam profile is recorded using a camera on the charge-coupled device 80. The pulse width is measured using an autocorrelation meter. Specifically, regarding spatiotemporal locking determination, taking output pulse energy and spectral shape as examples, when the laser output has not yet reached the locked state, the output pulse energy changes smoothly by adjusting the momentum space control device within a small range. When the laser output reaches the spatiotemporally locked state, the output optical power will fluctuate significantly when the momentum space control device is changed; at this time, the current position of the momentum space control device is recorded. When the laser output has not yet reached the locked state, the output spectral shape does not change significantly by adjusting the momentum space control device within a small range, exhibiting a single longitudinal mode state. When the laser output reaches the spatiotemporally locked state, the output spectrum will show significant broadening when the momentum space control device is changed, the spectral shape will change significantly, and multiple longitudinal modes will be generated within the spectrum; at this time, the current position of the momentum space control device needs to be recorded.

[0064] Furthermore, the output state determination method for the spatiotemporal mode-locked state includes the measurement feedback signal voltage, output pulse repetition frequency stability, output pulse energy, output spectral width, etc., output from the monitoring output device 53, thereby determining whether mode locking has been completed.

[0065] Furthermore, in specific applications, the all-fiber momentum space modulation device 50 can be used not only in the smart spatiotemporal mode-locked fiber laser 100 described in this preferred embodiment, i.e., the ytterbium-doped multimode mode-locked fiber laser, but also in any wavelength multimode mode-locked fiber laser with obvious optical response for spatiotemporal mode locking, such as the visible light band, communication band, and mid- to far-infrared band; and the all-fiber momentum space modulation device 50 can also be used in free-space optical fiber lasers.

[0066] like Figure 5 As shown, Figure 5 This is a flowchart of the spatiotemporal locking mode determination procedure for the intelligent spatiotemporal mode-locked fiber laser 100 according to a preferred embodiment. First, the multimode fiber pump source 10 is turned on, and the laser is in a continuous optical pulse output state without any control. Next, the momentum space random modulation device 51 is adjusted; the control method can be a winding type (e.g.,...). Figure 3 ), compression-stretching type (such as Figure 4 ) or local heating (such as Figure 5Mode random coupling is performed inside the multimode fiber using methods such as [list of methods]. Taking the winding method as an example, the multimode fiber is evenly wound onto the multi-paddle coupling controller, and can be loosened using the rotating knob on the winding disc for easy disassembly. By rotating any paddle of the coupling controller via an external motor, the phase and amplitude inside the momentum space of the multimode fiber can be changed, thus obtaining arbitrary mode field distributions in coordinate space. Subsequently, the intracavity state is collected by the monitoring output device 53 and transmitted to the intelligent feedback control device 52. The operation of the intelligent feedback algorithm module 521 includes two parts: first, the random mode field signal fed back by the monitoring output device 53 is controlled by a global optimization algorithm to find the optimal solution set that satisfies the spatiotemporal mode-locking state; then, artificial intelligence is used to repeatedly learn the spatiotemporal mode-locking state set to shorten the spatiotemporal mode-locking time, so as to accurately control the spatial mode field distribution and complete the entire process.

[0067] Regarding the specific locking method, taking the pulse energy and spectral shape output from the monitoring output device 53 as an example, when the laser output has not yet reached the locked state, the output pulse energy changes smoothly by adjusting the momentum space control device within a small range. When the laser output reaches the spatiotemporal locked state, the output optical power will fluctuate significantly when the momentum space control device is changed; at this time, the current position of the momentum space control device is recorded. When the laser output has not yet reached the locked state, the output spectral shape does not change significantly by adjusting the momentum space control device within a small range, exhibiting a single longitudinal mode state. When the laser output reaches the spatiotemporal locked state, the output spectrum will show obvious broadening when the momentum space control device is changed, and multiple longitudinal modes will be generated within the spectrum; at this time, the current position of the momentum space control device is recorded.

[0068] Global optimization algorithms can include genetic algorithms, particle swarm optimization, simulated annealing, and other algorithms; artificial intelligence can include artificial neural networks, association rule learning, and other methods for training and optimization.

[0069] Therefore, the intelligent spatiotemporal mode-locked fiber laser 100 provided in this preferred embodiment can obtain any spatial state simply by adjusting the momentum space control device, and acquire the desired spatial state through an intelligent feedback algorithm. The intelligent spatiotemporal mode-locked fiber laser 100 exhibits excellent flexibility and controllability in achieving spatial mode control and completing spatiotemporal mode-locking. Furthermore, compared to existing methods that require misaligned fiber splicing for spatial mode control, which incurs some losses, the intelligent spatiotemporal mode-locked fiber laser 100 provided in this preferred embodiment completely transforms any spatial state into the desired spatial state, effectively reducing spatial losses. In addition, compared to other large spatial control devices, the momentum space control device used in this preferred embodiment is miniaturized and, after operation through the intelligent feedback algorithm module 521, is easy to use and highly stable. Therefore, the intelligent spatiotemporal mode-locked fiber laser 100 exhibits excellent flexibility and controllability in achieving spatial mode control and completing spatiotemporal mode-locking, reduces spatial losses, and is characterized by its small size, ease of operation, and high stability, making it more valuable for future applications.

[0070] The present invention also provides a preferred embodiment of a control method applied to the intelligent spatiotemporal mode-locked fiber laser 100 to control the intelligent spatiotemporal mode-locked fiber laser 100. For example... Figure 7 As shown, Figure 7 The flowchart illustrates the control method. Depending on different requirements, the order of steps in the flowchart can be changed, and some steps can be omitted. The control method includes the following steps:

[0071] S100: The mode field distribution of arbitrary shape in the coordinate space of multimode fiber is obtained by using momentum space random control device.

[0072] Specifically, please refer to the following: Figure 1 and Figure 7 In a preferred embodiment of the control method described in this invention, in practical applications, in order to control the spatial mode field distribution, the momentum space random control device 51 is first used to obtain a mode field distribution of arbitrary shape in the multimode fiber coordinate space, thereby realizing momentum space random control.

[0073] S200: The specific mode field distribution of the spatiotemporal mode-locked state of multimode fiber is obtained through an intelligent feedback control device;

[0074] Specifically, please refer to the following: Figure 1 and Figure 7In a preferred embodiment of the control method described in this invention, after obtaining a mode field distribution of arbitrary shape in the coordinate space of the multimode fiber, the specific mode field distribution of the spatiotemporal mode-locked state of the multimode fiber is obtained through the intelligent feedback control device 52 in order to control the spatial mode field distribution.

[0075] The above technical solution can obtain any spatial state through momentum space random control device, and acquire the desired spatial state through intelligent feedback control device to control the spatial mode field distribution, realize the simultaneous locking of time mode and spatial mode, and obtain the effect of high-energy pulse output.

[0076] In summary, the intelligent spatiotemporal mode-locked fiber laser and control method provided by this invention have the following beneficial effects:

[0077] This invention employs an intelligent spatiotemporal mode-locked fiber laser equipped with a momentum space control device to achieve simultaneous spatiotemporal mode locking in a multimode fiber laser. First, an arbitrary mode field distribution in coordinate space is obtained through a momentum space random control device. Then, a smart feedback control device identifies the specific mode field distribution of the spatiotemporal mode-locked state of the multimode fiber. Finally, the spatial mode field distribution can be precisely controlled, achieving simultaneous locking of both temporal and spatial modes, resulting in stable and reliable high-energy ultrashort pulse output. Compared to direct control in coordinate space using methods such as pinhole placement and misaligned fusion splicing, this intelligent spatiotemporal mode-locked fiber laser offers superior flexibility and controllability, while reducing spatial losses, making it more valuable for future applications.

[0078] It should be understood that the above description of the technical solutions of this invention is quite specific and should not be construed as limiting the scope of protection of this invention. The scope of protection of this invention should be determined by the appended claims. Any technical solutions developed by those skilled in the art based on the above preferred embodiments of this invention without any inventive effort, including changes and modifications, should fall within the scope of protection of this invention.

Claims

1. A smart spatiotemporal mode-locked fiber laser, wherein the smart spatiotemporal mode-locked fiber laser is a multimode fiber laser and has an optical resonant cavity structure, characterized in that... include: An all-fiber momentum space modulation device is connected to the optical resonant cavity structure and is used to control the spatial mode field distribution. The all-fiber momentum space modulation device includes: a momentum space random modulation device and an intelligent feedback control device; The momentum space random modulation device and the intelligent feedback control device are connected; The momentum space random control device is used to obtain a mode field distribution of arbitrary shape in the coordinate space of a multimode fiber. The intelligent feedback control device is used to obtain the specific mode field distribution of the spatiotemporal mode-locked state of the multimode fiber. The all-fiber momentum space modulation device also includes: a monitoring output device; The monitoring output device is connected to the all-fiber momentum space modulation device and the intelligent feedback control device respectively. The monitoring output device is used to monitor the intracavity state of the all-fiber momentum space modulation device and output a signal to the intelligent feedback control device. Specifically, the random mode field distribution signal generated by the momentum space random modulation device is transmitted to the intelligent feedback control device.

2. The intelligent spatiotemporal mode-locked fiber laser according to claim 1, characterized in that, The optical resonant cavity structure is a ring cavity circuit. The intelligent spatiotemporal mode-locked fiber laser also includes: a multimode fiber pump source, a multimode pump connector, a few-mode gain fiber, a passive graded-index fiber, a multimode fiber optical isolator, a saturable absorber, a multimode fiber coupler, and a multimode fiber filter. The multimode fiber pump source is connected to the multimode pump connector, and the multimode fiber pump source is used to excite the laser working medium. The multimode pump connector is used to couple the light and signal emitted by the multimode fiber pump source into the ring cavity circuit; The few-mode gain fiber is used to generate a one-micron wavelength laser through light emitted from the multimode fiber pump source via the gain material. The passive graded-index fiber is used to reduce intermodal dispersion. The multimode fiber optical isolator is used to ensure unidirectional transmission of laser light in the ring cavity circuit. The saturable absorber is used to achieve time-domain mode locking; The multimode fiber coupler is used to couple a portion of the laser output from the ring cavity circuit. The multimode fiber filter is used for time-domain filtering of the laser in the ring cavity circuit.

3. The intelligent spatiotemporal mode-locked fiber laser according to claim 1, characterized in that, The intelligent feedback control device includes an intelligent feedback algorithm module; The intelligent feedback algorithm module obtains a set of specific modulus field distributions that satisfy the spatiotemporal modulus-locking state through a global optimization algorithm, and the intelligent feedback algorithm module repeatedly learns the set of specific modulus field distributions that satisfy the spatiotemporal modulus-locking state through artificial intelligence.

4. The intelligent spatiotemporal mode-locked fiber laser according to claim 3, characterized in that, The intelligent feedback control device also includes: a knob control module; The knob control module is used to lock the specific modulus field distribution of the spatiotemporal modulus-locking state manually or through the intelligent feedback algorithm module.

5. The intelligent spatiotemporal mode-locked fiber laser according to claim 2, characterized in that, The multimode fiber pump source, the multimode pump connector, the few-mode gain fiber, the passive graded-index fiber, the all-fiber momentum space modulation device, the multimode fiber optical isolator, the saturable absorber, the multimode fiber coupler, and the multimode fiber filter are sequentially connected to form a ring cavity circuit.

6. The intelligent spatiotemporal mode-locked fiber laser according to claim 1, characterized in that, The momentum space random control device obtains a mode field distribution of arbitrary shape in the coordinate space of the multimode fiber by changing the geometry of the multimode fiber.

7. The intelligent spatiotemporal mode-locked fiber laser according to claim 2, characterized in that, The saturable absorber is either an artificial or a natural saturable absorber.

8. The intelligent spatiotemporal mode-locked fiber laser according to claim 2, characterized in that, The few-mode gain fiber is a step-index doped rare-earth fiber with ytterbium-doped fiber as the laser gain medium.

9. A control method applied to an intelligent spatiotemporal mode-locked fiber laser according to any one of claims 1-8, characterized in that, Includes the following steps: The mode field distribution of arbitrary shape in the coordinate space of multimode fiber can be obtained by using momentum space random control devices. The monitoring output device is used to monitor the intracavity state of the momentum space modulation device and output a signal to the intelligent feedback control device; specifically, the random mode field distribution signal generated by the momentum space random modulation device is transmitted to the intelligent feedback control device. The specific mode field distribution of the spatiotemporal mode-locked state of the multimode fiber is obtained through an intelligent feedback control device.

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