Fiber laser and control method thereof

Abstract

The invention discloses a fiber laser and a control method thereof. A fiber laser includes: a seed source for emitting signal light; the optical fiber amplifier comprises a gain optical fiber, the first end of the gain optical fiber is connected with the seed source, and the second end of the gain optical fiber emits a laser beam formed after the signal light is amplified; the detection feedback module is used for detecting light spot energy distribution of the laser beam and generating a control instruction according to the light spot energy distribution; and the control module is electrically connected with the detection feedback module and is used for twisting the gain optical fiber according to the control instruction. According to the optical fiber laser provided by the embodiment of the invention, automatic control on the light spot shape is realized by utilizing the electric control system, the operation threshold and the maintenance condition of light spot deformation maintenance of the optical fiber laser are reduced, and the maintenance efficiency of the optical fiber laser in a complex processing environment is improved; and the long-term use stability and the service life of the fiber laser are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, and in particular to a fiber laser and a control method thereof. Background Art

[0002] Laser processing technology enables efficient, high-quality, and advanced processing of new materials. Ultrafast pulsed lasers, in particular, with their extremely high peak power and narrow pulse width, have been widely used in fields such as fine micromachining of materials, the semiconductor industry, solar photovoltaics, and scientific research. During these applications, the spot circularity and energy distribution of ultrafast pulsed lasers are crucial parameters, significantly impacting the quality of the final product after ultra-precision machining.

[0003] There are several mainstream solutions to the problem of laser spot deformation at the laser outlet: If the spot roundness changes greatly, the energy distribution is extremely uneven, and it is difficult to meet the use requirements, the laser will usually be returned to the factory for repair by engineers, which will cause the external processing optical path to need to be readjusted, and the maintenance cycle is usually longer; the laser is tested and verified before leaving the factory, and an adjustable lens bracket is added in front of the module that is prone to cause spot deformation, and a window is set at the corresponding position of the laser housing. After the spot is deformed, the lens bracket is adjusted through the window to adjust the spot. The disadvantage is that the window will affect the airtightness and stability of the laser. At the same time, the laser cavity is opened outside the clean room for debugging, which is prone to dust contamination of the mirror and there is a risk of damaging the lens. Summary of the Invention

[0004] The embodiments of the present invention provide a fiber laser and a control method thereof, which utilize an electronic control system to realize automatic control of the spot shape, thereby lowering the operating threshold and maintenance conditions for repairing the fiber laser spot deformation, improving the maintenance efficiency of the fiber laser in complex processing environments, and effectively enhancing the long-term stability and service life of the fiber laser.

[0005] In a first aspect, an embodiment of the present invention provides a fiber laser, comprising:

[0006] A seed source, used for emitting signal light;

[0007] An optical fiber amplifier, comprising a gain optical fiber, wherein a first end of the gain optical fiber is connected to the seed source, and a second end of the gain optical fiber emits a laser beam formed by amplifying the signal light;

[0008] a detection feedback module, detecting the spot energy distribution of the laser beam and generating a control instruction according to the spot energy distribution;

[0009] The control module is electrically connected to the detection feedback module and twists the gain optical fiber according to the control instruction.

[0010] Optionally, the optical fiber amplifier further includes an optical fiber end cap, an optical fiber end cap base, and a first fixing member, wherein the optical fiber end cap is connected to the second end of the gain optical fiber, and the optical fiber end cap is fixed on the optical fiber end cap base;

[0011] The first fixing member fixes the gain optical fiber at a first distance from the optical fiber end cap to the optical fiber end cap base.

[0012] Optionally, the control module includes a movable block and a second fixing member, and the movable block is twisted and fixed on the optical fiber end cap base;

[0013] The second fixing member fixes the gain optical fiber at a second distance from the optical fiber end cap to the movable block, and the second distance is greater than the first distance.

[0014] Optionally, the optical fiber amplifier further includes a pump source, and the pump light emitted by the pump source is projected onto the optical fiber end cap.

[0015] Optionally, the optical fiber amplifier further includes a beam combiner, wherein the beam combiner is connected between the first end of the gain optical fiber and the seed source;

[0016] The control module includes an active block, and the active block multiplexes the combiner.

[0017] Optionally, the optical fiber amplifier further includes a pump source, and the pump light emitted by the pump source and the signal light are projected onto the same end of the combiner.

[0018] Optionally, the detection feedback module includes a spectroscopic element, an attenuation plate and a photosensitive element;

[0019] The beam splitting element is located on the propagation path of the laser beam and splits the laser beam into an outgoing light and a detection light;

[0020] The attenuation plate and the photosensitive element are located on a propagation path of the detection light, and the attenuation plate is located between the light splitting element and the photosensitive element.

[0021] Optionally, the detection feedback module further includes a feedback circuit, which is electrically connected to the photosensitive element to generate the control instruction;

[0022] The control module further includes a servo motor, which twists the gain optical fiber according to the control instruction.

[0023] Optionally, the photosensitive element performs curve fitting according to the spot energy distribution of the laser beam, and selects the motor coordinates with the smallest error value from the Gaussian distribution as the control instruction.

[0024] In a second aspect, an embodiment of the present invention further provides a method for controlling a fiber laser, comprising:

[0025] causing the seed source to emit signal light;

[0026] enabling a gain optical fiber in an optical fiber amplifier to amplify the signal light to form a laser beam;

[0027] enabling a detection feedback module to detect the spot energy distribution of the laser beam and generate a control instruction according to the spot energy distribution;

[0028] The control module is enabled to twist the gain optical fiber according to the control instruction.

[0029] An embodiment of the present invention provides a fiber laser. The signal light emitted by the seed source is incident on the fiber amplifier, and the gain fiber inside the fiber amplifier amplifies the signal light to form a laser beam. The detection feedback module detects the spot energy distribution of the laser beam, and the detection feedback module provides control instructions to the control module. By applying additional stress to the gain fiber, automatic control of the spot energy distribution is achieved. The fiber laser proposed in the present invention uses an electronic control system to achieve automatic control of the spot shape, lowering the operating threshold and maintenance conditions for repairing the spot deformation of the fiber laser, improving the maintenance efficiency of the fiber laser in complex processing environments, and effectively improving the stability and service life of the fiber laser during long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a working diagram of a fiber laser provided by an embodiment of the present invention;

[0031] Figure 2 1 is a schematic structural diagram of a reverse-pumped fiber laser provided by an embodiment of the present invention;

[0032] Figure 3 yes Figure 2 A partial enlarged schematic diagram of part A;

[0033] Figure 4 1 is a schematic structural diagram of a forward-pumped fiber laser provided by an embodiment of the present invention;

[0034] Figure 5 yes Figure 4 A partial enlarged schematic diagram of part B;

[0035] Figure 6 This is a flow chart of a fiber laser control method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0037] Figure 1 This is a working diagram of a fiber laser provided by an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of a reverse pumped fiber laser provided by an embodiment of the present invention, with reference to Figure 1 and Figure 2 The embodiment of the present invention provides a fiber laser, which includes a seed source 10, a fiber amplifier 20, a detection feedback module 30, and a control module 40. The seed source 10 is used to emit signal light; the fiber amplifier 20 includes a gain fiber 21, the first end of the gain fiber 21 is connected to the seed source 10, and the second end of the gain fiber 21 emits a laser beam formed by amplifying the signal light. Figure 1 As shown, the output light is split, that is, the light is split at the light output port of the fiber amplifier 20, and a portion of the laser beam emitted by the fiber amplifier 20 is projected to the detection and feedback module 30. The detection and feedback module 30 detects the spot energy distribution of the laser beam and generates a control instruction based on the spot energy distribution; the control module 40 is electrically connected to the detection and feedback module 30 and twists the gain fiber 21 according to the control instruction of the detection and feedback module 30.

[0038] The embodiment of the present invention provides a reverse pumped fiber laser, in which a seed source 10 emits a signal light to be amplified, and the signal light is incident on a gain fiber 21. The gain fiber 21 has a gain medium inside, which is usually doped with rare earth elements (such as erbium, ytterbium, etc.). Under the excitation of the pump light, the gain medium can achieve a particle number inversion, generate stimulated radiation, and amplify the intensity of the signal light to form a laser beam. The detection feedback module 30 detects the spot energy distribution of the laser beam, and the detection feedback module 30 provides a control instruction to the control module 40 to twist the gain fiber 21. Among them, the detection feedback module 30 can detect the spot energy distribution of the laser beam in real time, or detect the spot energy distribution of the laser beam once every preset time.

[0039] The gain fiber 21 has a certain torsional space. When light is transmitted normally in the gain fiber 21, the principle of total reflection is used to achieve efficient and low-loss transmission of the optical signal. When providing control instructions to the control module 40, the control module 40 applies additional stress to the gain fiber 21, so that light in a certain direction does not meet the propagation conditions of total reflection in the gain fiber 21, and is therefore scattered and dissipated. In this way, artificial interference can be made on the beam quality and energy distribution of the light spot, thereby achieving automatic control of the energy distribution of the light spot.

[0040] An embodiment of the present invention provides a fiber laser. The signal light emitted by the seed source 10 is incident on the fiber amplifier 20, and the gain fiber 21 inside the fiber amplifier 20 amplifies the signal light to form a laser beam. The detection feedback module 30 detects the spot energy distribution of the laser beam. The detection feedback module 30 provides control instructions to the control module 40. The control module 40 changes the spot energy distribution of the laser beam by applying additional stress to the gain fiber 21, that is, changes the spot energy distribution of the light outlet, and realizes automatic control of the spot energy distribution. The fiber laser proposed in the present invention uses an electronic control system to realize automatic control of the spot shape, reduces the operating threshold and maintenance conditions for repairing the spot deformation of the fiber laser, improves the maintenance efficiency of the fiber laser in complex processing environments, and effectively improves the stability and service life of the fiber laser in long-term use.

[0041] Optional, Figure 3 yes Figure 2 A partial enlarged schematic diagram of part A, refer to Figure 2 and Figure 3 The optical fiber amplifier 20 further includes an optical fiber end cap 22, an optical fiber end cap base 23, and a first fixing member 24. The optical fiber end cap 22 is connected to the second end of the gain fiber 21 and fixed to the optical fiber end cap base 23. The first fixing member 24 fixes the gain fiber 21 at a first distance from the optical fiber end cap 22 to the optical fiber end cap base 23. In this embodiment of the present invention, the connection of one end of the optical fiber end cap 22 to the second end of the gain fiber 21 and the fixing of the gain fiber 21 at the first distance from the optical fiber end cap 22 to the optical fiber end cap base 23 ensure that the output end position of the gain fiber 21 remains unchanged when stress is applied to the distal gain fiber 21, thereby preventing the directivity of the light beam from shifting.

[0042] It is understandable that the length of the gain fiber 21 is usually long, and the length can be 1 meter to 20 meters. Among them, the gain fiber 21 includes a fixed section and an adjustable section. The fixed section refers to the gain fiber 21 that is fixed 0 to 50 mm in front of the fiber end cap 22, and the adjustable section refers to the gain fiber 21 that is more than 50 mm in front of the fiber end cap 22 and is adjustable. The fixed section and the adjustable section can also be other lengths, and the embodiments of the present invention do not limit this. A gain fiber 21 that is long enough can allow the signal light and the pump light to fully interact and achieve energy amplification through stimulated radiation. Among them, the adjustable section of the gain fiber 21 is coiled into a circle, so that there is a certain amount of torsion space while the coiling radius of the gain fiber 21 remains unchanged.

[0043] Among them, the first fixing member 24 fixes the gain fiber 21 at a first distance from the fiber end cap 22 to the fiber end cap base 23. The first fixing member 24 can be a fiber pressing block. The first distance can be 50 mm or other lengths. The embodiment of the present invention does not limit this.

[0044] Optional, continue to refer to Figure 2 and Figure 3 The control module 40 includes a movable block 41 and a second fixing member 42. The movable block 41 is twisted and fixed on the optical fiber end cap base 23; the second fixing member 42 fixes the gain optical fiber 21 at a second distance from the optical fiber end cap 22 on the movable block 41, and the second distance is greater than the first distance.

[0045] The movable block 41 is located at the center of the fiber end cap base 23, further away from the fiber end cap 22. A stable torsional fulcrum is established on the fiber end cap base 23 to torsionally secure the movable block 41 to the fiber end cap base 23. The mechanical securing method may be a pin-type torsion connection, which is not limited in this embodiment of the present invention. A second fixing member 42 secures the gain fiber 21 to the movable block 41 at a second distance from the fiber end cap 22. The second distance may be 50 to 100 mm, and the second distance is greater than the first distance. The securing method is glue.

[0046] Illustratively, the control module 40 further includes a third fixing member 43, which is located on a side of the second fixing member 42 that is distal to the fiber end cap 22. The third fixing member 43 secures the gain fiber 21 to the movable block 41 at a third distance from the fiber end cap 22, where the third distance is greater than the second distance. In this embodiment of the present invention, securing the gain fiber 21 to the movable block 41 via the second fixing member 42 and the third fixing member 43 improves the stability of the connection between the gain fiber 21 and the movable block 41.

[0047] For example, by fixing the gain fiber 21 50 mm to 100 mm in front of the fiber end cap 22 on the movable block 41 with glue, when a control instruction is provided to the control module 40, the servo motor 44 in the control module 40 drives the movable block 41 to twist, and then the movable block 41 drives the gain fiber 21 to twist, thereby realizing automatic control of the light spot energy distribution.

[0048] Illustratively, the optical fiber amplifier 20 further includes a fourth fixture 26, which is located on a side of the third fixture 43 away from the optical fiber end cap 22. The fourth fixture 26 secures the gain fiber 21 to the optical fiber end cap base 23 at a fourth distance from the optical fiber end cap 22, where the fourth distance is greater than the third distance. The fourth fixture 26 may be a fiber clamp.

[0049] Optional, reference Figure 2 The optical fiber amplifier 20 further includes a pump source 25 , and the pump light emitted by the pump source 25 is projected onto the optical fiber end cap 22 .

[0050] It is understood that the pump source 25 emits pump light, which can be a diode laser, and this embodiment of the present invention does not limit this. The pump light is reversely injected into the cladding of the gain fiber 21 through the fiber end cap 22, exciting the gain medium in the core of the gain fiber 21, causing electrons to transition from the ground state to the excited state, forming a population inversion, and providing an energy basis for the amplification of the signal light. The pump light is incident from the fiber end cap 22, and the propagation direction of the pump light and the signal light is opposite. This reverse pumping structure allows the pump light and the signal light to overlap throughout the gain fiber 21, making the population inversion distribution more uniform and improving the stability of the light spot energy distribution.

[0051] Optional, Figure 4 1 is a schematic structural diagram of a forward-pumped fiber laser provided by an embodiment of the present invention. Figure 5 yes Figure 4 A partial enlarged schematic diagram of part B, see Figure 4 and Figure 5 The optical fiber amplifier 20 further includes a combiner 27 , which is connected between the first end of the gain optical fiber 21 and the seed source 10 ; the control module 40 includes an active block 41 , which multiplexes the combiner 27 .

[0052] It is understood that in a forward-pumped fiber laser, the pump light and signal light propagate in the same direction. The combiner 27 combines the signal light and pump light through optical coupling technology and transmits them to the gain fiber 21. The combiner 27 is fixed to a servo motor 44 in the control module 40. As the combiner 27 rotates with the servo motor 44, the gain fiber 21 also rotates with the combiner 27, thereby generating controllable stress. Therefore, the movable block 41 reuses the combiner 27 to simplify the system structure.

[0053] The optical fiber amplifier 20 further includes a PD monitoring device 28 , which can monitor the power stability of the pump light in real time.

[0054] Optional, reference Figure 4 The optical fiber amplifier 20 further includes a pump source 25 , and the pump light and the signal light emitted by the pump source 25 are projected to the same end of the combiner 27 .

[0055] Pump source 25 emits pump light, which is injected into the input port of fiber amplifier 20. The pump light and signal light propagate in the same direction. This forward pumping structure ensures precise spatial overlap of the signal and pump lights, minimizing energy loss and avoiding damage to optical components caused by reflected light. This allows for efficient transmission and amplification of the signal light.

[0056] For example, refer to Figure 5The fiber laser further includes a fifth fixing member 29, which fixes the circular portion of the gain fiber 21. The fifth fixing member 29 can be a fiber clamp.

[0057] Optional, reference Figures 1 to 5 The detection feedback module 30 includes a spectrometer 31, an attenuation plate 32 and a photosensitive element 33; the spectrometer 31 is located on the propagation path of the laser beam and splits the laser beam into outgoing light and detection light; the attenuation plate 32 and the photosensitive element 33 are located on the propagation path of the detection light, and the attenuation plate 32 is located between the spectrometer 31 and the photosensitive element 33.

[0058] For a reverse-pumped fiber laser, the laser beam emitted from the fiber end cap 22 propagates to the coated mirror 34. The side of the coated mirror 34 near the gain fiber 21 is coated with a high-reflection coating, which allows for total reflection of the laser beam. The side away from the gain fiber 21 is coated with an anti-reflection coating, which allows for total transmission of the reverse pump light. A dichroic mirror 35 is positioned between the pump source 25 and the coated mirror 34. This mirror provides high transmission of the pump light and high reflection of the signal light, ensuring that the pump light is injected back into the cladding from the output end while preventing the signal light from entering the pump source 25 in the reverse direction, thus avoiding interference from optical feedback. The laser beam is then reflected to the beam splitter 31. Most of the laser beam is reflected by the beam splitter 31, becoming the output light that leaves the fiber laser and enters the external optical system. A small portion of the laser beam is transmitted by the beam splitter 31, becoming the probe light that is incident on the attenuator 32. The attenuation plate 32 attenuates excessively strong detection light to a level that the photosensitive element 33 can withstand, protecting it from damage and improving detection accuracy. The photosensitive element 33 can be a charge-coupled device (CCD), which monitors the energy distribution of the detection light spot and provides real-time quantitative data.

[0059] Optional, reference Figures 1 to 5 The detection feedback module 30 further includes a feedback circuit 36 ​​, which is electrically connected to the photosensitive element 33 and generates a control instruction. The control module 40 further includes a servo motor 44 , which twists the gain fiber 21 according to the control instruction.

[0060] Among them, the feedback circuit 36 ​​is used to receive the digital signal of the light spot energy distribution collected by the photosensitive element 33. If there is an error in the light spot shape, the feedback circuit 36 ​​can generate control instructions in real time, drive the servo motor 44, twist the gain fiber 21, optimize the light spot quality, and ensure that the laser can stably output a light beam that meets the requirements under complex working conditions, reduce manual intervention and improve adjustment accuracy.

[0061] Optionally, the photosensitive element 33 performs curve fitting according to the spot energy distribution of the laser beam, and selects the motor coordinates with the smallest error value from the Gaussian distribution as the control instruction.

[0062] It can be understood that after the photosensitive element 33 collects the spot energy distribution data of the laser beam and converts it into a digital signal, the actual spot distribution is matched with the ideal Gaussian distribution model through a curve fitting algorithm, and the error value between the two is calculated. Among them, the motor coordinates with the smallest error value are used as control instructions to drive the motor to adjust the optical fiber stress, so that the spot energy distribution continuously approaches the Gaussian distribution, forming a closed-loop optimization process to achieve automatic calibration of the spot quality.

[0063] Exemplarily, the optical fiber amplifier 20 may be a femtosecond pulse laser. Specifically, the optical fiber amplifier 20 may be a high-power optical fiber femtosecond pulse laser with adjustable spot energy distribution.

[0064] Figure 6 This is a flow chart of a fiber laser control method provided by an embodiment of the present invention, refer to Figures 1 to 6 , the control methods of fiber laser include:

[0065] S101 , the seed source 10 emits signal light.

[0066] S102 : The gain fiber 21 in the fiber amplifier 20 amplifies the signal light to form a laser beam.

[0067] S103 , the detection feedback module 30 detects the spot energy distribution of the laser beam and generates a control instruction according to the spot energy distribution.

[0068] S104 , the control module 40 twists the gain fiber 21 according to the control instruction.

[0069] The fiber laser control method provided in the embodiment of the present invention adopts the fiber laser provided in the above embodiment.

[0070] The above control method uses the photosensitive element 33 to collect the spot energy distribution of the amplified signal light in real time and fit the Gaussian model, drives the servo motor 44 to twist the gain fiber 21, has the ability of automatic calibration without human intervention, can accurately improve the spot energy concentration, approach the ideal Gaussian distribution, and has strong interference ability. It can respond to environmental changes in real time to maintain the stability of the light beam, improves the maintenance efficiency of the laser in complex processing environments, and effectively improves the stability and service life of the laser in long-term use.

[0071] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will appreciate that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations, and substitutions are possible for those skilled in the art without departing from the scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the scope of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A fiber laser, characterized in that: include: A seed source, used for emitting signal light; An optical fiber amplifier, comprising a gain optical fiber, wherein a first end of the gain optical fiber is connected to the seed source, and a second end of the gain optical fiber emits a laser beam formed by amplifying the signal light; a detection feedback module, detecting the spot energy distribution of the laser beam and generating a control instruction according to the spot energy distribution; The control module is electrically connected to the detection feedback module and twists the gain optical fiber according to the control instruction.

2. The fiber laser according to claim 1, wherein: The optical fiber amplifier further includes an optical fiber end cap, an optical fiber end cap base, and a first fixing member, wherein the optical fiber end cap is connected to the second end of the gain optical fiber, and the optical fiber end cap is fixed on the optical fiber end cap base; The first fixing member fixes the gain optical fiber at a first distance from the optical fiber end cap to the optical fiber end cap base.

3. The fiber laser according to claim 2, characterized in that The control module includes a movable block and a second fixing member, and the movable block is twisted and fixed on the optical fiber end cap base; The second fixing member fixes the gain optical fiber at a second distance from the optical fiber end cap to the movable block, and the second distance is greater than the first distance.

4. The fiber laser according to claim 3, characterized in that The optical fiber amplifier further includes a pump source, and the pump light emitted by the pump source is projected onto the optical fiber end cap.

5. The fiber laser according to claim 1, wherein: The optical fiber amplifier further includes a beam combiner connected between the first end of the gain optical fiber and the seed source; The control module includes an active block, and the active block multiplexes the combiner.

6. The fiber laser according to claim 5, characterized in that The optical fiber amplifier further includes a pump source, and the pump light emitted by the pump source and the signal light are projected onto the same end of the beam combiner.

7. The fiber laser according to claim 1, wherein: The detection feedback module includes a spectroscopic element, an attenuation plate and a photosensitive element; The beam splitting element is located on the propagation path of the laser beam and splits the laser beam into an outgoing light and a detection light; The attenuation plate and the photosensitive element are located on a propagation path of the detection light, and the attenuation plate is located between the light splitting element and the photosensitive element.

8. The fiber laser according to claim 7, characterized in that The detection feedback module further includes a feedback circuit, which is electrically connected to the photosensitive element and generates the control instruction; The control module further includes a servo motor, which twists the gain optical fiber according to the control instruction.

9. The fiber laser according to claim 8, characterized in that The photosensitive element performs curve fitting according to the spot energy distribution of the laser beam, and selects the motor coordinates with the smallest error value from the Gaussian distribution as the control instruction.

10. A method for controlling a fiber laser, characterized in that: include: causing the seed source to emit signal light; enabling a gain optical fiber in an optical fiber amplifier to amplify the signal light to form a laser beam; enabling a detection feedback module to detect the spot energy distribution of the laser beam and generate a control instruction according to the spot energy distribution; The control module is enabled to twist the gain optical fiber according to the control instruction.

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