CN115313138B - System and method for actively inhibiting instability of fiber laser mode - Google Patents
System and method for actively inhibiting instability of fiber laser mode Download PDFInfo
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- CN115313138B CN115313138B CN202211237294.0A CN202211237294A CN115313138B CN 115313138 B CN115313138 B CN 115313138B CN 202211237294 A CN202211237294 A CN 202211237294A CN 115313138 B CN115313138 B CN 115313138B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
- H01S3/1305—Feedback control systems
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
- H01S3/1301—Stabilisation of laser output parameters, e.g. frequency or amplitude in optical amplifiers
Abstract
The invention provides a system and a method for actively inhibiting instability of a fiber laser mode, which comprises the following steps: the device comprises a fiber laser, a laser beam splitting module, a fundamental mode frequency shift module, a high-order mode frequency shift module, a mode division multiplexer, a fiber amplifier and a feedback device; the fiber laser provides a system seed laser source; the laser beam splitting module generates two laser beams with unstable inhibition modes according to the system seed laser; the fundamental mode frequency shift module provides fundamental mode seed laser; the high-order mode frequency shift module provides high-order mode seed laser for inhibiting mode interference; the mode division multiplexer couples the fundamental mode seed laser and the high-order mode seed laser into the optical fiber amplifier; the optical fiber amplifier amplifies and outputs the optical fiber seed laser with a stable mode; and the feedback device controls the fundamental mode frequency shift module and the high-order mode frequency shift module according to the output optical fiber seed laser. The invention destroys the mode interference in the optical fiber amplifier by controlling the frequency shift quantity between the high-order mode and the fundamental mode, and restrains the generation of the mode instability effect.
Description
Technical Field
The invention relates to the technical field of optical communication, in particular to a system and a method for actively inhibiting instability of a fiber laser mode.
Background
The beam quality is an important technical index for measuring the performance of the fiber laser. High-power fiber lasers with high brightness and high beam quality have become indispensable tools in the fields of industrial processing, basic science and biomedicine, benefit from the compactness, high energy conversion efficiency and low cost of the fiber lasers, and are rapidly developed based on the application of high-power fiber laser technology. And the instability of the transmission mode becomes one of the main limiting factors for limiting the further increase of the laser output power of the single-mode single-fiber. The mode instability exhibits a threshold characteristic associated with the excitation of higher order modes during laser amplification. At this stage, it is widely accepted that the higher-order modes and the fundamental mode cause refractive index grating formation in the optical fiber along the beam transmission direction through the thermo-optic effect, thereby causing energy exchange between the modes, and finally causing the quality degradation of the output beam. Therefore, how to find a fiber laser system that can suppress the mode instability effect and can be used becomes a problem to be solved.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a system and a method for actively inhibiting the instability of a fiber laser mode, and solves the technical problem that the stability of a fiber seed laser mode is difficult to control in the prior art.
According to a first aspect of the present invention, there is provided a system for actively suppressing instability of a fiber lasing mode, comprising:
a fiber laser, a laser beam splitting module, a fundamental mode frequency shift module, a high-order mode frequency shift module, a mode division multiplexer, a fiber amplifier and a feedback device,
the optical fiber laser is connected with the laser beam splitting module and used for providing a system seed laser source;
the two outputs of the laser beam splitting module are respectively connected with the fundamental mode frequency shift module and the high-order mode frequency shift module and are used for generating two laser beams with unstable suppression modes according to the seed laser of the system;
the fundamental mode frequency shift module is connected with a single mode input end of the mode division multiplexer and is used for providing fundamental mode seed laser;
the high-order mode frequency shift module is connected with a high-order mode input end of the mode division multiplexer and is used for providing high-order mode seed laser for inhibiting mode interference;
the output end of the mode division multiplexer is connected with the optical fiber amplifier and is used for coupling the fundamental mode seed laser and the high-order mode seed laser into the optical fiber amplifier;
the optical fiber amplifier is used for amplifying and outputting optical fiber seed laser with a stable mode;
the input end of the feedback device is connected with the output end of the optical fiber amplifier, one output end of the feedback device is connected with the fundamental mode frequency shift module, and the other output end of the feedback device is connected with the high-order mode frequency shift module, and the feedback device is used for controlling the fundamental mode frequency shift module and the high-order mode frequency shift module according to the optical fiber seed laser output by the optical fiber amplifier.
On the basis of the technical scheme, the invention can be improved as follows.
Optionally, the fiber laser is a continuous laser or a pulse laser.
Optionally, the fundamental-mode frequency shift module and the high-order-mode frequency shift module each include any one of an acousto-optic modulator, an acousto-optic frequency shifter, or an electro-optic frequency modulator, and act on the passing laser beam to generate a fixed frequency shift.
Optionally, the fundamental mode frequency shift module and/or the higher-order mode frequency shift module further include a preamplifier, and an output end of the preamplifier is connected to an input end of the mode division multiplexer.
Optionally, the mode division multiplexer includes a single-mode fiber taper coupler or a few-mode fiber taper coupler.
Optionally, the feedback device includes a frequency source, and a mode detection unit, a photoelectric conversion unit, an electronic signal control unit, a direct digital frequency synthesizer, and a mixer, which are connected in series in sequence;
the output end of the frequency source is connected with the fundamental mode frequency shift module and is used for generating a fixed radio frequency shift signal;
the input end of the mode detection unit is connected with the output end of the optical fiber amplifier and is used for sampling optical fiber seed laser output by the system;
the photoelectric conversion unit is used for converting the sampled optical fiber seed laser into a mode feedback electric signal;
the electronic signal control unit is used for judging whether the optical fiber seed laser mode output by the system changes according to the mode feedback electric signal and outputting a mode control signal according to a judgment result;
the direct digital frequency synthesizer is used for generating a frequency shift quantity signal according to the mode control signal;
one input end of the mixer is connected with the output end of the frequency source, the other input end of the mixer is connected with the direct digital frequency synthesizer, and the output end of the mixer is connected with the high-order mode frequency shift module and is used for superposing the frequency shift quantity signal to a fixed radio frequency shift signal so as to output a frequency shift control signal.
Optionally, the frequency source includes any one of a voltage-controlled oscillator, a radio frequency signal generator, and a waveform generator.
Optionally, the mode detection unit includes a CCD camera or a pinhole photodetector.
Optionally, the optical fiber amplifier includes any one of a double-clad optical fiber amplifier, a photonic crystal optical fiber amplifier, or a tapered optical fiber amplifier.
According to a second aspect of the present invention, there is provided a method for actively suppressing instability of a fiber laser mode, comprising:
the seed laser source of the system is divided into two laser beams,
applying a fixed radio frequency shift signal to one laser beam to obtain a fundamental mode seed laser; applying a frequency shift control signal to the other laser beam to obtain high-order mode seed laser;
coupling and amplifying the fundamental mode seed laser and the high-order mode seed laser to obtain optical fiber seed laser output by the system;
monitoring the mode change of the optical fiber seed laser, and adjusting the frequency shift control signal according to the mode change of the optical fiber seed laser to enable the optical fiber seed laser to tend to be stable.
Optionally, the monitoring the mode change of the optical fiber seed laser, and adjusting the frequency shift control signal according to the mode change of the optical fiber seed laser includes:
sampling optical fiber seed laser output by a system and carrying out photoelectric conversion to obtain a mode feedback electric signal representing the current mode of the optical fiber seed laser;
judging whether the optical fiber seed laser mode output by the system changes or not according to the mode feedback electric signal, outputting a mode control signal according to a judgment result, and generating a frequency shift quantity signal delta according to the mode control signalf；
The frequency shift signal deltafSuperimposed on a fixed radio frequency shifted signalfTo output a frequency shift control signalf+Δf；
And circulating the steps until the mode of the optical fiber seed laser is judged to be stable.
The invention provides a system and a method for actively inhibiting the instability of an optical fiber laser mode, which feed back the distribution change of a beam mode of an optical fiber seed laser output by a real-time detection system, do not generate a frequency shift control signal for driving a high-order mode frequency shift module before the quality of the beam is degraded, and only generate a fixed frequency offThe driving signal controls the basic mode frequency shift module to work; when the mode unstable condition occurs, the feedback device detects that the mode distribution of the light beam changes, and the feedback device generates the frequency off+ΔfThe frequency shift control signal acts on the high-order frequency shift module to drive the high-order mode seed laser to generate frequency shift, so that the interference between a fundamental mode and a high-order mode in the optical fiber seed laser output by the system is damaged, and the generation of mode instability is inhibited; because the system outputs the optical fiber seed laser and simultaneously monitors the optical fiber seed laser in real time, when the output power of the laser continues to increase and the mode is unstable again, the feedback device updates the frequency shift signal deltafGenerating a new frequency shift control signal to act on the high-order mode frequency shift module so as to continuously destroy the interference between the fundamental mode and the high-order mode in the optical fiber seed laser output by the system; the feedback device circularly detects and controls the high-order mode frequency shift module to stabilize the output mode of the system. The invention destroys the mode interference in the optical fiber amplifier by controlling the frequency shift amount between the high-order mode and the fundamental mode, reduces the thermotropic refractive index grating induced by the mode interference, inhibits the generation of mode instability effect, and improves the output power of the optical fiber laser system.
Drawings
FIG. 1 is a block diagram of a system for actively suppressing instability of a fiber laser mode according to the present invention;
FIG. 2 is a schematic diagram of a system according to an embodiment of the present invention;
FIG. 3 is a block diagram of the structure of the feedback device according to the present invention;
fig. 4 is a flowchart of a method for actively suppressing instability of a fiber laser mode according to the present invention.
In the drawings, the reference numbers indicate the following list of parts:
1. the fiber laser comprises a fiber laser, 2, a laser beam splitting module, 3, a base mode frequency shifting module, 301, a first acousto-optic frequency shifter, 302, a first preamplifier, 4, a high-order mode frequency shifting module, 401, a second acousto-optic frequency shifter, 402, a second preamplifier, 5, a mode division multiplexer, 6, a fiber amplifier, 7, a feedback device, 701, a mode detection unit, 702, a frequency source, 703, a photoelectric conversion unit, 704, an electronic signal control unit, 705, a direct digital frequency synthesizer, 706 and a frequency mixer.
Detailed Description
The following detailed description of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.
Fig. 1 is a block diagram of a system for actively suppressing instability of a fiber laser mode according to this embodiment. As shown in fig. 1, a system for actively suppressing instability of a fiber laser mode includes: the system comprises an optical fiber laser 1, a laser beam splitting module 2, a fundamental mode frequency shift module 3, a high-order mode frequency shift module 4, a mode division multiplexer 5, an optical fiber amplifier 6 and a feedback device 7;
the optical fiber laser 1 is connected with the laser beam splitting module 2 and is used for providing a system seed laser source;
the two outputs of the laser beam splitting module 2 are respectively connected with the fundamental mode frequency shift module 3 and the high-order mode frequency shift module 4, and are used for splitting the system seed laser into two laser beams with unstable suppression modes; one laser beam is used for generating fundamental mode seed laser, and the other laser beam is used for generating high-order mode seed laser;
the fundamental mode frequency shift module 3 is connected with a single mode input end of the mode division multiplexer 5 and is used for providing fundamental mode seed laser; specifically, the fundamental mode frequency shift module 3 provides a fixed radio frequency shift signal for one laser beam split by the laser beam splitting module 2fOutputting stable basic mode seed laser;
the high-order mode frequency shift module 4 is connected with a high-order mode input end of the mode division multiplexer 5 and is used for providing high-order mode seed laser for inhibiting mode interference; specifically, when the fiber seed laser output by the system is stable, the high-order mode frequency shift module 4 does not work, and when the fiber seed laser is unstable, the high-order mode frequency shift module 4 provides a frequency shift control signal for another laser beam split by the laser beam splitting module 2 to control the laser beam to generate a frequency shift different from that of the fundamental mode seed laser, so that the interference formation between the fundamental mode and the high-order mode is damaged; the high-order mode seed laser corresponding to the high-order mode frequency shift module 4 is controlled by a feedback device 7 mentioned later;
the output end of the mode division multiplexer 5 is connected with the optical fiber amplifier 6 and is used for optically coupling the fundamental mode seed laser and the high-order mode seed laser into the optical fiber amplifier 6;
the optical fiber amplifier 6 is used for amplifying the coupled optical fiber seed laser and outputting the optical fiber seed laser with a stable mode;
the input end of the feedback device 7 is connected with the output end of the optical fiber amplifier 6 and is used for sampling the optical fiber seed laser output by the system; one output end of the feedback device 7 is connected to the fundamental mode frequency shift module 3, and the other output end of the feedback device 7 is connected to the higher-order mode frequency shift module 4, and is configured to control the fundamental mode frequency shift module 3 and the higher-order mode frequency shift module 4 according to the fiber seed laser output by the fiber amplifier 6. More specifically, whether the mode of the optical fiber seed laser output by the system is stable or not is judged according to the optical fiber seed laser output by the real-time sampling system, and if so, the fundamental mode frequency shift module 3 is continuously controlled to output a fixed radio frequency shift signalfThe high-order mode frequency shift module 4 does not work, and the high-order mode frequency shift module 4 does not output high-order mode seed laser at the moment; if the frequency shift is unstable, a fixed radio frequency shift signal is output from the control fundamental mode frequency shift module 3fMeanwhile, the feedback device 7 also outputs a frequency shift control signal to the high-order mode frequency shift module 4 to control the high-order mode seed laser to generate frequency shift, so that the mode interference of the optical fiber seed laser is reduced.
It is understood that, according to the theory of mode instability, the mode instability has a distinct threshold characteristic, and the threshold is proportional to the output power of the fiber laser system, which is caused by the mode-to-mode interference between the excited high-order mode and the fundamental mode when the output power is increased, and the refractive index grating is induced under the thermo-optic effect. The present embodiment utilizes this characteristic, when mode instability occurs, high-order mode laser light is actively injected, the frequency thereof is modulated, a frequency shift different from that of fundamental mode laser light is generated, interference formation between modes is destroyed, and thus mode instability is suppressed, and the threshold thereof is increased.
According to the system for actively inhibiting the instability of the fiber laser mode, the fiber seed laser output by the system is detected in real time to feed back the distribution change of the beam mode, a frequency shift control signal for driving the high-order mode frequency shift module 4 is not generated before the quality of the beam is degraded, and only a fixed frequency is generatedfThe driving signal controls the basic mode frequency shift module 3 to work; when the mode instability occurs, the feedback device 7 detects the change of the beam mode distribution, and the feedback device 7 generates the frequency off+ΔfThe frequency shift control signal acts on the high-order frequency shift module to drive the high-order mode seed laser to generate frequency shift, so that the interference between a fundamental mode and a high-order mode in the optical fiber seed laser output by the system is damaged, and the generation of mode instability is inhibited; because the system outputs the optical fiber seed laser and simultaneously monitors the optical fiber seed laser in real time, when the output power of the laser continues to increase and the mode is unstable again, the feedback device 7 updates the frequency shift signal deltafGenerating a new frequency shift control signal to act on the high-order mode frequency shift module 4, thereby continuously destroying the interference between the fundamental mode and the high-order mode in the optical fiber seed laser output by the system; the feedback device 7 will cyclically detect and control the high-order mode frequency shift module 4 to stabilize the output mode of the system. The invention destroys the mode interference in the optical fiber amplifier 6 by controlling the frequency shift amount between the high-order mode and the fundamental mode, reduces the thermotropic refractive index grating induced by the mode interference, inhibits the generation of mode instability effect, and improves the output power of the optical fiber laser system.
In a possible embodiment, the fiber laser 1 may use a continuous laser or a pulse laser, but other lasers capable of outputting stable laser light may also be used to provide a seed laser source for the system.
In a possible embodiment, the mode division multiplexer 5 comprises a single mode fiber taper coupler or a few mode fiber taper coupler. Of course, on the basis of the foregoing embodiments, the mode division multiplexer 5 may also use the remaining couplers, which are not limited to the single-mode fiber-tapered coupler or the few-mode fiber-tapered coupler.
In a possible embodiment, the fundamental mode frequency shift module 3 and the higher-order mode frequency shift module 4 each include any one of an acousto-optic modulator, an acousto-optic frequency shifter, or an electro-optic frequency modulator, which acts on a passing laser beam to produce a fixed frequency shift.
It will be appreciated that the fundamental mode frequency shift module 3 provides a fixed radio frequency shifted signal to its input laser lightfThe beam of laser light is used as a fundamental mode seed laser light. In the present embodiment, an acousto-optic frequency shifter is exemplified. For example, the fundamental mode frequency shift module 3 comprises a first acousto-optic frequency shifter 301 as shown in fig. 2, and the higher-order mode frequency shift module 4 comprises a second acousto-optic frequency shifter 401 as shown in fig. 2.
In a possible embodiment mode, the fundamental mode frequency shift module 3 and/or the higher-order mode frequency shift module 4 further comprise a preamplifier, an output of which is connected to an input of the mode division multiplexer 5.
More specifically, as shown in fig. 2, the base-mode frequency shift module 3 further includes a first preamplifier 302, an input end of the first preamplifier 302 is connected to the first acousto-optic frequency shifter 301, and an output end thereof is connected to a single-mode input end of the mode division multiplexer 5, and the first preamplifier 302 is configured to amplify the base-mode seed laser output by the first acousto-optic frequency shifter 301 and input the amplified base-mode seed laser to the mode division multiplexer 5, so as to compensate for loss caused by the first acousto-optic frequency shifter 301. The high-order mode frequency shift module 4 further includes a second preamplifier 402, an input terminal of the second preamplifier 402 is connected to the second optical frequency shifter 401, and an output terminal thereof is connected to a high-order mode input terminal of the mode division multiplexer 5, the second preamplifier 402 is configured to amplify the high-order mode seed laser output by the second optical frequency shifter 401 and input the amplified high-order mode seed laser to the mode division multiplexer 5, so as to compensate for loss caused by the second optical frequency shifter 401.
In order to more clearly express the idea of the present invention, a system design scheme for actively suppressing the instability of the fiber laser mode is described in detail in a specific embodiment as shown in fig. 2.
As shown in fig. 2, the present embodiment shows a system for actively suppressing instability of a fiber laser mode, which includes:
the fiber laser comprises a fiber laser 1, a fiber coupler, a fiber-coupled first acousto-optic frequency shifter 301, a fiber-coupled second acousto-optic frequency shifter 401, a first preamplifier 302, a second preamplifier 402, a mode division multiplexer 5, a large mode area double-clad fiber amplifier 6 and a feedback device 7.
The optical fiber laser 1 is directly welded with a 1 x 2 optical fiber coupler serving as a laser beam splitting module 2 and used for providing system seed laser; the optical fiber coupler is used as a laser beam splitting module 2, incident laser is divided into two beams, and the two beams are respectively and directly welded with an optical fiber coupling first acousto-optic frequency shifter 301 and an optical fiber coupling second acousto-optic frequency shifter 401, wherein the optical fiber coupling first acousto-optic frequency shift is used as a component of a fundamental mode frequency shifter, the system always keeps a working state during operation and is used for providing fundamental mode seed laser for the whole laser system, and under the condition that the system output is stable, high-order mode seed laser used for a suppression mode is not additionally applied and is used as the optical fiber seed laser output by the system; the second acoustic optical frequency shift is coupled by the optical fiber to be used as a component of a high-order frequency shift module, and a laser beam (high-order mode seed laser) for inhibiting mode instability is generated; the two frequency shifters are amplified by the first preamplifier 302 and the second preamplifier 402 respectively to compensate the loss caused by the acousto-optic frequency shifter at the front end thereof; the fundamental mode laser output by the first preamplifier 302 is connected with a single-mode input end of the mode division multiplexer 5, and is used for providing fundamental mode seed laser; the high-order mode laser output by the second preamplifier 402 is connected with the high-order mode input end of the mode division multiplexer 5, and is used for providing high-order mode seed laser for inhibiting mode interference; the output end of the mode division multiplexer 5 is connected with the large mode field area double-clad optical fiber amplifier 6 and is used for coupling a fundamental mode and a high-order mode into the large mode field area double-clad optical fiber amplifier 6 for amplification; the large mode field area double-clad optical fiber amplifier 6 is used for amplifying the seed laser, outputting the optical fiber seed laser with a stable mode, and is connected with the feedback device 7 to feed back the laser signal output by the system; the feedback device 7 is configured to convert an optical signal output by the system into an electrical signal, and control the optical fiber coupling first acousto-optic frequency shifter 301 and the optical fiber coupling second acousto-optic frequency shifter 401 after processing the electrical signal.
In the system for actively suppressing the instability of the fiber laser mode shown in each embodiment of fig. 1 and 2, the feedback device 7 for implementing the frequency shift working state and frequency control of the fundamental mode and the high-order mode is a key element for suppressing the instability of the mode, and therefore the structure of the feedback device 7 is described in detail in the next embodiment.
As shown in the structure diagram of the feedback device 7 in fig. 3, the feedback device 7 includes a frequency source 702, and a mode detection unit 701, a photoelectric conversion unit 703, an electronic signal control unit 704, a direct digital frequency synthesizer 705 and a mixer 706 which are connected in series in sequence;
the output end of the frequency source 702 is connected to the fundamental mode frequency shift module 3 for generating a fixed rf frequency shift signalf；
The input end of the mode detection unit 701 is connected with the output end of the optical fiber amplifier 6 and is used for sampling the optical fiber seed laser output by the system;
the photoelectric conversion unit 703 is configured to convert the sampled optical fiber seed laser into a mode feedback electrical signal;
the electronic signal control unit 704 is configured to determine whether a fiber seed laser mode output by the system changes according to the mode feedback electrical signal, and output a mode control signal according to a determination result;
the direct digital frequency synthesizer 705 is used for generating a frequency shift signal delta according to the mode control signalf；
One input end of the mixer 706 is connected to the output end of the frequency source 702, the other input end thereof is connected to the direct digital frequency synthesizer 705, the output end of the mixer 706 is connected to the higher-order mode frequency shifting module 4 for shifting the frequency of the signalΔfSuperimposed on a fixed radio frequency shifted signalfTo output a frequency shift control signalf+Δf。
In one possible embodiment, the frequency source 702 comprises any one of a voltage controlled oscillator, a radio frequency signal generator, and a waveform generator.
In one possible embodiment, the mode detection unit 701 comprises a CCD camera or an aperture photodetector.
In one possible embodiment, the fiber amplifier 6 comprises any one of a double clad fiber amplifier 6, a photonic crystal fiber amplifier, or a tapered fiber amplifier.
When the system works, the mode detection unit 701, the photoelectric signal conversion unit and the frequency source 702 are in a whole-course working state after the system is started; the frequency source 702 outputs a fixed frequency signal, and a part of the fixed frequency signal drives the fundamental mode frequency shift module 3 to generate a frequency shiftfAnother part of the laser beam enters the mixer 706; the mode detection unit 701 is connected with the photoelectric signal conversion unit, and the mode detection unit 701 is used for monitoring the mode change condition of the optical fiber seed laser beam output by the system and sending a sampled optical signal to the photoelectric signal conversion unit in real time; the photoelectric signal conversion unit is connected with the electronic signal control unit 704; the electronic signal control unit 704 is connected to a direct digital frequency synthesizer 705. When the unstable mode occurs, the electronic signal control unit 704 sends a mode control signal to the direct digital frequency synthesizer 705, and the direct digital frequency synthesizer 705 sends a frequency shift signal ΔfTo mixer 706, and a fixed RF frequency signal output by frequency source 702fMixing frequency generationf+ΔfThe frequency shift control signal of (3) to drive the high-order mode frequency shift module 4 to control the high-order mode frequency shift amount.
In the system for actively suppressing the instability of the fiber laser mode shown in the above embodiments, the operation mode and the control sequence of each component have an extremely important influence on the implementation of the technical method of the present invention, the technical problem related to the present invention is solved, and the expected effect of the present invention is obtained. Therefore, the workflow of the system in the above embodiment is explained in detail in the following embodiment. In combination with the system for actively suppressing the instability of the fiber laser mode shown in the above embodiments, the present embodiment further provides a method for actively suppressing the instability of the fiber laser mode, including:
the seed laser source of the system is divided into two laser beams,
applying a fixed RF frequency signal to one of the laser beamsfObtaining the basic mode seed laser; applying a frequency shift control signal to another laser beamf+ΔfObtaining high-order mode seed laser;
coupling and amplifying the fundamental mode seed laser and the high-order mode seed laser to obtain optical fiber seed laser output by the system;
monitoring the mode change of the optical fiber seed laser, and adjusting the frequency shift control signal according to the mode change of the optical fiber seed laserf+ΔfAnd stabilizing the optical fiber seed laser.
In this embodiment, mode monitoring of outputting the optical fiber seed laser is realized by sampling the finally output optical fiber seed laser, and mode closed-loop control of the optical fiber seed laser is realized according to a monitoring result.
In a possible embodiment, the monitoring the mode change of the fiber seed laser, and adjusting the frequency shift control signal according to the mode change of the fiber seed laser includes:
sampling optical fiber seed laser output by a system and carrying out photoelectric conversion to obtain a mode feedback electric signal representing the current mode of the optical fiber seed laser;
judging whether the optical fiber seed laser mode output by the system changes or not according to the mode feedback electric signal, outputting a mode control signal according to a judgment result, and generating a frequency shift quantity signal delta according to the mode control signalf；
The frequency shift quantity signal deltafSuperimposed on a fixed radio frequency signalfTo output a frequency shift control signalf+Δf；
And circulating the steps until the mode of the optical fiber seed laser is judged to be stable.
Fig. 4 is a flowchart illustrating steps of a method for actively suppressing instability of a fiber laser mode according to this embodiment. The method can be implemented by any of the embodiments of the system described above, and since the steps and principles of implementing the method for actively suppressing the instability of the fiber laser mode using the system described above are similar, this embodiment is only illustrated as one of the specific embodiments.
In practical operation, the method for actively suppressing the instability of the fiber laser mode as shown in fig. 4 mainly includes the following steps:
s1: and starting the system and sending signals to each component module of the system.
S2: after receiving a system starting instruction, the frequency source 702 is started, the frequency source 702 outputs the working frequency f of the fundamental mode frequency shifter to drive the fundamental mode frequency shifter to output seed laser, and then the optical fiber amplifier 6 is turned on to obtain laser output.
S3: after the system is started, the feedback device 7 works to monitor the change of the output optical fiber seed laser mode in real time, and when the mode is not changed, the direct digital frequency synthesizer 705 is in a standby state; when the mode is unstable, the electronic signal control unit 704 outputs a mode control signal to drive the direct digital frequency synthesizer 705 to operate, and outputs a frequency quantity signalΔf(ii) a If the mode instability state is stopped, the direct digital frequency synthesizer 705 keeps the state, and if the mode instability state still exists, the frequency quantity signal delta continues to be updatedfOutputting, e.g. increasing, output frequency quantity signal deltafThe value of (c).
The invention provides a system and a method for actively inhibiting the instability of an optical fiber laser mode, which feed back the distribution change of a beam mode of an optical fiber seed laser output by a real-time detection system, do not generate a frequency shift control signal for driving a high-order mode frequency shift module 4 before the quality of the beam is degraded, and only generate a fixed frequency offThe driving signal controls the basic mode frequency shift module 3 to work; when the mode instability occurs, the feedback device 7 detects the change of the beam mode distribution, and the feedback device 7 generates the frequency off+ΔfThe frequency shift control signal acts on the high-order frequency shift module to drive the high-order mode seed laser to generate frequency shift, so that the interference between a fundamental mode and a high-order mode in the optical fiber seed laser output by the system is damaged, and the generation of mode instability is inhibited; because the system outputs the optical fiber seed laser and simultaneously monitors the optical fiber seed laser in real time, when the output power of the laser continues to increase and the mode is unstable again, the feedback device is used for feeding back the laser7 updating frequency shift quantity signal deltafGenerating a new frequency shift control signal to act on the high-order mode frequency shift module 4, thereby continuously destroying the interference between the fundamental mode and the high-order mode in the optical fiber seed laser output by the system; the feedback device 7 will cyclically detect and control the high-order mode frequency shift module 4 to stabilize the output mode of the system. The invention destroys the mode interference in the optical fiber amplifier 6 by controlling the frequency shift amount between the high-order mode and the fundamental mode, reduces the thermotropic refractive index grating induced by the mode interference, inhibits the generation of mode instability effect, and improves the output power of the optical fiber laser system.
It should be noted that, in the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and reference may be made to relevant descriptions of other embodiments for parts that are not described in detail in a certain embodiment.
While the preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A system for actively suppressing instability of fiber laser mode is characterized in that,
the method comprises the following steps: the device comprises an optical fiber laser (1), a laser beam splitting module (2), a fundamental mode frequency shift module (3), a high-order mode frequency shift module (4), a mode division multiplexer (5), an optical fiber amplifier (6) and a feedback device (7);
the optical fiber laser (1) is connected with the laser beam splitting module (2) and is used for providing a system seed laser source;
the two outputs of the laser beam splitting module (2) are respectively connected with the fundamental mode frequency shift module (3) and the high-order mode frequency shift module (4) and are used for generating two laser beams with unstable suppression modes according to system seed lasers;
the fundamental mode frequency shift module (3) is connected with a single mode input end of the mode division multiplexer (5) and is used for providing fundamental mode seed laser;
the high-order mode frequency shift module (4) is connected with a high-order mode input end of the mode division multiplexer (5) and is used for providing high-order mode seed laser for inhibiting mode interference;
the output end of the mode division multiplexer (5) is connected with the optical fiber amplifier (6) and is used for coupling the fundamental mode seed laser and the high-order mode seed laser into the optical fiber amplifier (6);
the optical fiber amplifier (6) is used for amplifying and outputting optical fiber seed laser with a stable mode;
the input end of the feedback device (7) is connected with the output end of the optical fiber amplifier (6), one output end of the feedback device (7) is connected with the fundamental mode frequency shift module (3), and the other output end of the feedback device (7) is connected with the higher-order mode frequency shift module (4) and used for controlling the fundamental mode frequency shift module (3) and the higher-order mode frequency shift module (4) according to the optical fiber seed laser output by the optical fiber amplifier (6).
2. The system for actively suppressing instability of fiber laser mode as claimed in claim 1, wherein the fiber laser (1) is a continuous laser or a pulsed laser.
3. A system for actively suppressing fiber laser mode instability as claimed in claim 1, wherein the fundamental mode frequency shift module (3) and the higher-order mode frequency shift module (4) each include any one of an acousto-optic modulator, an acousto-optic frequency shifter or an electro-optic frequency modulator, which acts on the passing laser beam to generate a fixed frequency shift.
4. A system for actively suppressing instability of fiber laser mode according to claim 3, wherein the fundamental mode frequency shift module (3) and/or the higher order mode frequency shift module (4) further comprises a preamplifier, the output of which is connected to the input of the mode division multiplexer (5).
5. The system for actively suppressing the instability of the fiber laser mode according to claim 1, wherein the feedback device (7) comprises a frequency source (702), and a mode detection unit (701), a photoelectric conversion unit (703), an electronic signal control unit (704), a direct digital frequency synthesizer (705) and a mixer (706) which are connected in series in sequence;
the output end of the frequency source (702) is connected with the basic mode frequency shift module (3) and is used for generating a fixed radio frequency shift signal;
the input end of the mode detection unit (701) is connected with the output end of the optical fiber amplifier (6) and is used for sampling optical fiber seed laser output by a system;
the photoelectric conversion unit (703) is used for converting the sampled optical fiber seed laser into a mode feedback electric signal;
the electronic signal control unit (704) is used for judging whether the optical fiber seed laser mode output by the system changes according to the mode feedback electric signal and outputting a mode control signal according to a judgment result;
the direct digital frequency synthesizer (705) is used for generating a frequency shift quantity signal according to the mode control signal;
one input end of the mixer (706) is connected with the output end of the frequency source (702), the other input end of the mixer is connected with the direct digital frequency synthesizer (705), and the output end of the mixer (706) is connected with the high-order mode frequency shift module (4) and is used for superposing the frequency shift quantity signal on a fixed radio frequency shift signal so as to output a frequency shift control signal.
6. A system for actively suppressing instability of a fiber laser mode according to claim 5, wherein the frequency source (702) comprises any one of a voltage controlled oscillator, a radio frequency signal generator, and a waveform generator.
7. The system for actively suppressing instability of the fiber laser mode as claimed in claim 5, wherein the mode detection unit (701) comprises a CCD camera or an aperture photodetector.
8. A system for actively suppressing instability of the fiber laser mode as defined in claim 1, wherein the fiber amplifier (6) comprises any one of a double clad fiber amplifier, a photonic crystal fiber amplifier or a tapered fiber amplifier.
9. A method for actively suppressing instability of a fiber lasing mode, comprising:
the system seed laser source is split into two laser beams,
applying a fixed radio frequency shift signal to one laser beam to obtain a fundamental mode seed laser; applying a frequency shift control signal to the other laser beam to obtain high-order mode seed laser;
coupling and amplifying the fundamental mode seed laser and the high-order mode seed laser to obtain optical fiber seed laser output by the system;
monitoring the mode change of the optical fiber seed laser, and adjusting the frequency shift control signal according to the mode change of the optical fiber seed laser to enable the optical fiber seed laser to tend to be stable.
10. The method of claim 9, wherein the monitoring the mode change of the fiber seed laser and the adjusting the frequency shift control signal according to the mode change of the fiber seed laser comprises:
sampling optical fiber seed laser output by a system and carrying out photoelectric conversion to obtain a mode feedback electric signal representing the current mode of the optical fiber seed laser;
judging whether the optical fiber seed laser mode output by the system changes according to the mode feedback electric signal and judging the result according to the judgmentOutputting a mode control signal, and generating a frequency shift signal delta according to the mode control signalf；
The frequency shift signal deltafSuperimposed on a fixed radio frequency shifted signalfTo output a frequency shift control signal f + deltaf；
And circulating the steps until the mode of the optical fiber seed laser is judged to be stable.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN202977957U (en) * | 2012-11-16 | 2013-06-05 | 广东汉唐量子光电科技有限公司 | Forward feedback amplification system |
| CN104037610A (en) * | 2014-07-01 | 2014-09-10 | 哈尔滨工业大学 | Single longitudinal mode laser interlocking method and device based on thermal frequency stabilization and acousto-optic frequency shift |
| CN109936042A (en) * | 2019-04-30 | 2019-06-25 | 北京理工大学 | A kind of generating device of the random waveform microwave signal based on Frequency shifted feedback laser |
| CN111916984A (en) * | 2020-08-20 | 2020-11-10 | 中国人民解放军国防科技大学 | Fiber laser system with mode instability effect suppression function |
| CN111969400A (en) * | 2020-08-27 | 2020-11-20 | 中国人民解放军国防科技大学 | High power fiber laser system |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| DE102006023601B4 (en) * | 2006-05-19 | 2009-01-15 | Menlo Systems Gmbh | laser system |
| US9397464B2 (en) * | 2014-12-19 | 2016-07-19 | Lumentum Operations Llc | Fiber laser assembly and method of generating light |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN202977957U (en) * | 2012-11-16 | 2013-06-05 | 广东汉唐量子光电科技有限公司 | Forward feedback amplification system |
| CN104037610A (en) * | 2014-07-01 | 2014-09-10 | 哈尔滨工业大学 | Single longitudinal mode laser interlocking method and device based on thermal frequency stabilization and acousto-optic frequency shift |
| CN109936042A (en) * | 2019-04-30 | 2019-06-25 | 北京理工大学 | A kind of generating device of the random waveform microwave signal based on Frequency shifted feedback laser |
| CN111916984A (en) * | 2020-08-20 | 2020-11-10 | 中国人民解放军国防科技大学 | Fiber laser system with mode instability effect suppression function |
| CN111969400A (en) * | 2020-08-27 | 2020-11-20 | 中国人民解放军国防科技大学 | High power fiber laser system |
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