A pulsed fiber laser with adjustable repetition rate

Abstract

The embodiment of the present invention discloses a pulse fiber laser with adjustable repetition rate. The pulse fiber laser includes a control module, a seed source, an injection source, at least one amplification module, a first circulator and a second circulator; the control module is used to control the seed source to output a seed pulse with adjustable repetition rate, and control the injection source to output an injection pulse with adjustable repetition rate; the seed pulse output by the seed source is incident on the first end of the first circulator, and the injection pulse output by the injection source is incident on the first end of the second circulator; the seed pulse passes through the first end and the second end of the first circulator and is incident on the amplification module for amplification, and is output after passing through the second end and the third end of the second circulator; the injection pulse passes through the first end and the second end of the second circulator and is reversely injected into the amplification module, and the generated amplified spontaneous radiation is output from the third end of the first circulator. The present invention can reduce the risk of self-excitation of amplified spontaneous radiation, is compatible with a wide range of frequency changes, and is compatible with ns-level pulse output.

Description

Technical Field

[0001] The invention relates to the field of laser technology, in particular to a pulse fiber laser with adjustable repetition rate. Background Art

[0002] In the process of amplifying nanosecond-level high-power narrow pulses, the pulse width of the optical pulse signal is nanoseconds, and the peak power can reach kilowatts or even megawatts. The higher peak power will stimulate various nonlinear effects in the optical fiber, such as stimulated Brillouin scattering, stimulated Raman scattering, self-phase modulation, etc., which will eventually lead to the degradation of the output amplified pulse signal performance. In actual use, due to the adjustable change of pulse width repetition rate, there will also be problems of bidirectional ASE transmission caused by self-excitation of ASE (Amplification of Spontaneous Emission) due to low duty cycle, causing damage to the laser.

[0003] At present, there are two low repetition rate solutions for polarization-maintaining pulse fiber lasers: 1. Pulse pumping, so that the pump is also in pulse form, reducing the risk of ASE self-excitation. However, it is difficult to unify the time, and the repetition rate cannot be above 2kHz, which cannot reduce the risk of ASE self-excitation at the 10kHz level. 2. Long pulse width and low repetition rate, simple structure, increased duty cycle, and less prone to ASE self-excitation state. However, the pulse width cannot reach the ns level, and the peak value cannot be increased under high duty cycle conditions. Summary of the invention

[0004] The embodiment of the present invention provides a pulse fiber laser with adjustable repetition rate, which reduces the risk of self-excitation caused by amplified spontaneous radiation generated by the seed pulse during the amplification process, is compatible with a wide range of frequency changes, is compatible with ns-level pulse output, is conducive to improving the signal-to-noise ratio, and outputs a narrow-bandwidth, high-peak value, adjustable repetition rate pulse laser.

[0005] According to one aspect of the present invention, there is provided a pulse fiber laser with adjustable repetition rate, comprising a control module, a seed source, an injection source, at least one amplification module, a first circulator and a second circulator;

[0006] The control end of the seed source and the control end of the injection source are both connected to the control module, and the control module is used to control the seed source to output a seed pulse with an adjustable repetition frequency, and control the injection source to output an injection pulse with an adjustable repetition frequency;

[0007] The seed pulse output by the seed source is incident on the first end of the first circulator, the second end of the first circulator is connected to the input end of the amplification module, the output end of the amplification module is connected to the second end of the second circulator, and the injection pulse output by the injection source is incident on the first end of the second circulator;

[0008] The seed pulse passes through the first end and the second end of the first circulator, is incident on the amplification module for amplification, and is output after passing through the second end and the third end of the second circulator;

[0009] The injection pulse is reversely injected into the amplification module after passing through the first end and the second end of the second circulator, and the amplified spontaneous radiation generated by the injection pulse is output from the third end of the first circulator;

[0010] The pulse width of the seed pulse is smaller than the pulse width of the injection pulse, the peak power of the seed pulse is greater than the peak power of the injection pulse, and the start time of the injection pulse is later than the corresponding time of the falling edge of the seed pulse.

[0011] Optionally, the amplification module includes a primary amplification module and a secondary amplification module, and the pulse fiber laser further includes a third circulator and a fourth circulator;

[0012] The second end of the first circulator is connected to the input end of the first-stage amplification module, the output end of the first-stage amplification module is connected to the second end of the second circulator, part of the injection pulse output by the injection source is input to the first end of the second circulator, part of the injection pulse is input to the first end of the fourth circulator, the third end of the second circulator is connected to the first end of the third circulator, the second end of the third circulator is connected to the input end of the second-stage amplification module, and the output end of the second-stage amplification module is connected to the second end of the fourth circulator.

[0013] Optionally, the first-stage amplification module includes a first pump source, an optical fiber beam splitter, a first wavelength division multiplexer, a second wavelength division multiplexer, a first active optical fiber, and a second active optical fiber;

[0014] The output end of the first pump source is connected to the input end of the optical fiber splitter, the first output end of the optical fiber splitter is connected to the first input end of the first wavelength division multiplexer, the second output end of the optical fiber splitter is connected to the first input end of the second wavelength division multiplexer, the second input end of the first wavelength division multiplexer is connected to the second end of the first circulator, the output end of the first wavelength division multiplexer is connected to the first end of the first active optical fiber, the second end of the first active optical fiber is connected to the second input end of the second wavelength division multiplexer, and the output end of the second wavelength division multiplexer is connected to the first end of the second active optical fiber.

[0015] Optionally, the first-stage amplification module includes a second pump source, a third pump source, a first wavelength division multiplexer, a second wavelength division multiplexer, a first active optical fiber, and a second active optical fiber;

[0016] The output end of the second pump source is connected to the first input end of the first wavelength division multiplexer, the second input end of the first wavelength division multiplexer is connected to the second end of the first circulator, the output end of the first wavelength division multiplexer is connected to the first end of the first active optical fiber, the second end of the first active optical fiber is connected to the second input end of the second wavelength division multiplexer, the output end of the third pump source is connected to the first input end of the second wavelength division multiplexer, and the output end of the second wavelength division multiplexer is connected to the first end of the second active optical fiber.

[0017] Optionally, the first-stage amplification module also includes a first filter and a second filter, the input end of the first filter is connected to the second end of the first active optical fiber, the output end of the first filter is connected to the second input end of the second wavelength division multiplexer, the input end of the second filter is connected to the second end of the second active optical fiber, and the output end of the second filter is connected to the second end of the second circulator.

[0018] Optionally, the secondary amplification module includes a fourth pump source, a third wavelength division multiplexer and a third active optical fiber;

[0019] The output end of the fourth pump source is connected to the first input end of the third wavelength division multiplexer, the second input end of the third wavelength division multiplexer is connected to the second end of the third circulator, and the input and output of the third wavelength division multiplexer are connected to the first end of the third active optical fiber.

[0020] Optionally, the third active optical fiber is a double-clad active optical fiber, and the secondary amplification module further includes a cladding light stripper, the input end of the cladding light stripper is connected to the second end of the third active optical fiber, and the second end of the cladding light stripper is connected to the second end of the fourth circulator.

[0021] Optionally, a collimator is also included at the output end of the pulse fiber laser.

[0022] Optionally, the control module comprises a field-editable gate array, and the seed source and the injection source both comprise distributed Bragg feedback single-frequency semiconductor lasers.

[0023] Optionally, the repetition frequency of the pulsed fiber laser output pulses is adjusted in the range of 1 Hz to 10 kHz.

[0024] The embodiment of the present invention provides a pulse fiber laser with adjustable repetition rate. The control module controls the seed source to output the seed pulse and controls the injection source to output the injection pulse. The pulse width of the injection pulse is greater than the pulse width of the seed pulse. The seed pulse output by the seed source passes through the first circulator and is incident on the amplifier module for amplification. Due to delayed injection, the injection pulse output by the injection source passes through the second circulator after the seed pulse is turned off and is reversely injected into the amplifier module. A part of the amplified spontaneous radiation generated in the amplification process of the amplifier module is filtered out through the third end of the first circulator, thereby reducing the risk of self-excitation caused by the amplified spontaneous radiation generated by the seed pulse in the amplification process, improving the signal-to-noise ratio, and outputting a narrow bandwidth and high peak repetition rate adjustable pulse laser. The laser is compatible with a wide range of frequency changes and is compatible with ns-level pulse output.

[0025] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 1 A schematic structural diagram of a first pulse fiber laser with adjustable repetition rate provided in an embodiment of the present invention;

[0028] Figure 2 An oscilloscope comparison diagram of a seed pulse and an injected pulse provided in an embodiment of the present invention;

[0029] Figure 3 A schematic diagram of the structure of a second pulse fiber laser with adjustable repetition rate provided in an embodiment of the present invention;

[0030] Figure 4 A schematic structural diagram of a third pulse fiber laser with adjustable repetition rate provided in an embodiment of the present invention;

[0031] Figure 5 A schematic structural diagram of a fourth pulse fiber laser with adjustable repetition rate provided in an embodiment of the present invention;

[0032] Figure 6 A schematic structural diagram of a fifth pulse fiber laser with adjustable repetition rate provided in an embodiment of the present invention;

[0033] Figure 7A schematic structural diagram of a sixth pulse fiber laser with adjustable repetition rate provided in an embodiment of the present invention;

[0034] Figure 8 A spectrum diagram of the output laser before injection provided by an embodiment of the present invention;

[0035] Fig. 9 This is a spectrum diagram of the output laser after injection provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0037] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0038] Figure 1 A schematic diagram of the structure of a first pulse fiber laser with adjustable repetition rate provided in an embodiment of the present invention, Figure 2 The oscilloscope comparison diagram of the seed pulse and the injected pulse provided in the embodiment of the present invention is shown in FIG. Figure 1 and Figure 2 The pulse fiber laser with adjustable repetition frequency includes a control module 10, a seed source 20, an injection source 30, at least one amplification module 40, a first circulator 51 and a second circulator 52. The control end of the seed source 20 and the control end of the injection source 30 are both connected to the control module 10, and the control module 10 is used to control the seed source 20 to output a seed pulse with adjustable repetition frequency, and control the injection source 30 to output an injection pulse with adjustable repetition frequency. Among them, the pulse width of the seed pulse is smaller than the pulse width of the injection pulse, the peak power of the seed pulse is greater than the peak power of the injection pulse, and the start time of the injection pulse is later than the corresponding time of the falling edge of the seed pulse. Figure 2The red pulse is the injection pulse, and the purple pulse is the seed pulse. As an example, the seed source 20 and the injection source 30 are both distributed Bragg feedback (DFB) 1064nm polarization-maintaining single-frequency semiconductor lasers. In other embodiments, the models of the seed source 20 and the injection source 30 can be set according to actual needs, and the embodiment of the present invention does not limit this. Exemplarily, the control module 10 controls the seed source 20 to output a seed pulse of 5ns / 100Hz, and the control module 10 controls the injection source 30 to output an injection pulse of 9ms / 100Hz. The peak power of the seed pulse is 150mW, and the start time of the injection pulse is delayed by 100μs from the falling edge of the seed pulse.

[0039] Exemplarily, the seed pulse output by the seed source 20 is incident on the first end of the first circulator 51, the second end of the first circulator 51 is connected to the input end of the amplification module 40, the output end of the amplification module 40 is connected to the second end of the second circulator 52, and the injection pulse output by the injection source 30 is incident on the first end of the second circulator 52. After passing through the first and second ends of the first circulator 51, the seed pulse is incident on the amplification module 40 for amplification, and is output after passing through the second and third ends of the second circulator 52; the injection pulse is reversely injected into the amplification module 40 after passing through the first and second ends of the second circulator 52, and the amplified spontaneous radiation generated by the injection pulse is output from the third end of the first circulator 51.

[0040] Specifically, the circulator is a multi-port device that transmits the incident wave entering any port to the next port in the order of directions determined by the static bias magnetic field. The circulator can transmit high-frequency energy in one direction, that is, the signal input from the first end can only be output from the second end, and the signal input from the second end can only be output from the third end. It is used to isolate the signal and protect the amplifier module 40. The seed pulse output by the seed source 20 is incident to the amplifier module 40 for amplification after passing through the first circulator 51. At the same time, due to delayed injection, the injection pulse output by the injection source 30 is reversely injected into the amplifier module 40 after passing through the second circulator 52 after the seed pulse is turned off. The pulse width of the seed pulse is smaller than the pulse width of the injection pulse, which is equivalent to the injection pulse wrapping the seed pulse. The injection pulse has a lower peak value. The amplified spontaneous radiation generated by the injection pulse is amplified by the amplifier module 40 and filtered out by the third end of the first circulator 51, which reduces the amplified spontaneous radiation and nonlinear effects generated by the seed pulse during the amplification process, improves the signal-to-noise ratio, and outputs a narrow bandwidth and high peak value repetition frequency adjustable pulse laser.

[0041] The embodiment of the present invention provides a pulse fiber laser with adjustable repetition rate. The control module controls the seed source to output the seed pulse and controls the injection source to output the injection pulse. The pulse width of the injection pulse is greater than the pulse width of the seed pulse. The seed pulse output by the seed source passes through the first circulator and is incident on the amplification module for amplification. Due to delayed injection, the injection pulse output by the injection source passes through the second circulator after the seed pulse is turned off and is reversely injected into the amplification module. A part of the amplified spontaneous radiation generated in the amplification process of the amplification module is filtered out through the third end of the first circulator, thereby reducing the risk of self-excitation caused by the amplified spontaneous radiation generated by the seed pulse in the amplification process, improving the signal-to-noise ratio, outputting a narrow bandwidth and high peak repetition rate adjustable pulse laser, and being compatible with a wide range of frequency changes and ns-level pulse output to prevent laser damage.

[0042] Figure 3 The schematic diagram of the structure of the second pulse fiber laser with adjustable repetition rate provided by the embodiment of the present invention is shown in FIG. Figure 3 The pulse fiber laser with adjustable repetition rate further comprises a collimator 60 located at the output end of the pulse fiber laser. The collimator 60 converges the divergent light output by the pulse laser into parallel light output.

[0043] Exemplarily, the control module 10 includes a field editable gate array, and the seed source 20 and the injection source 30 both include a distributed Bragg feedback type single-frequency semiconductor laser. The field editable gate array is composed of hardware resources such as logic units, random access memory (RAM), multipliers, etc., and can realize hardware circuits such as multipliers, registers, and address generators. It has rich wiring resources, can be infinitely reprogrammed, has high integration, and reduces costs. The distributed Bragg feedback type single-frequency semiconductor laser has good monochromaticity, narrow line width, and high transmission rate.

[0044] Exemplarily, the repetition frequency adjustment range of the pulse output by the pulse fiber laser is 1Hz to 10kHz. The injected pulse is injected in the form of a duty cycle of 30% to 90%. As an example, when the repetition frequency adjustment range is 1Hz to 1kHz, the injected pulse is injected in the form of a 90% duty cycle; when the repetition frequency adjustment range is 1kHz to 5kHz, the injected pulse is injected in the form of a 60% duty cycle; when the repetition frequency adjustment range is 5Hz to 10kHz, the injected pulse is injected in the form of a 30% duty cycle. The pulse fiber laser provided by the embodiment of the present invention can adjust the repetition frequency over a wide range and stably output pulsed lasers with narrow pulse width and high peak value.

[0045] Figure 4 The schematic diagram of the structure of the third pulse fiber laser with adjustable repetition rate provided by the embodiment of the present invention is shown in FIG. Figure 4The amplification module 40 includes a primary amplification module 41 and a secondary amplification module 42, and the pulse fiber laser also includes a third circulator 53 and a fourth circulator 54. The second end of the first circulator 51 is connected to the input end of the primary amplification module 41, the output end of the primary amplification module 41 is connected to the second end of the second circulator 52, part of the injection pulse output by the injection source 30 is input to the first end of the second circulator 52, part of the injection pulse is input to the first end of the fourth circulator 54, the third end of the second circulator 52 is connected to the first end of the third circulator 53, the second end of the third circulator 53 is connected to the input end of the secondary amplification module 42, and the output end of the secondary amplification module 42 is connected to the second end of the fourth circulator 54.

[0046] Exemplarily, the amplification module 40 includes a first amplification module 41 and a second amplification module 42, and the first amplification module 41 and the second amplification module 42 amplify the seed pulse input by the seed source 20 twice to obtain a pulse laser with a higher peak value. The first amplification module 41 amplifies the seed pulse input by the seed source 20 for the first time, and a part of the injection pulse output by the injection source 30 is input to the first end of the second circulator 52, and is reversely injected into the first amplification module 41 through the second circulator 52, and a part of the amplified spontaneous radiation generated in the amplification process of the first amplification module 41 is filtered out through the third end of the first circulator 51, so as to reduce the amplified spontaneous radiation and nonlinear effect generated by the seed pulse in the first amplification process; the seed pulse after the first amplification is input to the second amplification module 42 through the third circulator 53 for amplification, and a part of the injection pulse output by the injection source 30 is input to the first end of the fourth circulator 54, and is reversely injected into the second amplification module 42 through the fourth circulator 54, and a part of the amplified spontaneous radiation generated in the amplification process of the second amplification module 42 is filtered out through the third end of the third circulator 53, so as to reduce the amplified spontaneous radiation and nonlinear effect generated by the seed pulse in the second amplification process. The injection pulse output by the injection source 30 is divided into two parts, and the amplified spontaneous radiation generated in the first amplification process and the second amplification process are filtered respectively to ensure that the seed pulse is not easy to generate amplified spontaneous radiation during the amplification process, and the pulse laser is output stably with a high signal-to-noise ratio.

[0047] Exemplarily, the first-stage amplification module 41 includes a first pump source 410, a fiber beam splitter 411, a first wavelength division multiplexer 412, a second wavelength division multiplexer 413, a first active fiber 414, and a second active fiber 415. The output end of the first pump source 410 is connected to the input end of the fiber beam splitter 411, the first output end of the fiber beam splitter 411 is connected to the first input end of the first wavelength division multiplexer 412, the second output end of the fiber beam splitter 411 is connected to the first input end of the second wavelength division multiplexer 413, the second input end of the first wavelength division multiplexer 412 is connected to the second end of the first circulator 51, the output end of the first wavelength division multiplexer 412 is connected to the first end of the first active fiber 414, the second end of the first active fiber 414 is connected to the second input end of the second wavelength division multiplexer 413, and the output end of the second wavelength division multiplexer 413 is connected to the first end of the second active fiber 415.

[0048] Specifically, the first pump source 410 generates high-energy pump light, which is input into the optical fiber beam splitter 411. The optical fiber beam splitter divides the pump light into two parts, one part of the pump light is transmitted from the first output end to the first wavelength division multiplexer 412, and the other part of the pump light is transmitted from the second output end to the second wavelength division multiplexer 413. The wavelength division multiplexer combines optical signals of different wavelengths into one beam, transmits them along a single optical fiber, and separates the optical signals at the output end, so that optical signals of different wavelengths can be transmitted on the same optical fiber. The first active optical fiber 414 amplifies the seed pulse, and the amplified seed pulse is transmitted to the second active optical fiber 415 through the second wavelength division multiplexer 413. The second active optical fiber 415 amplifies the seed pulse again and outputs it. As an example, the pump source 410 is a 980nm laser, the optical fiber splitter 411 transmits 40% of the pump light to the first wavelength division multiplexer 412, and transmits 60% of the pump light to the second wavelength division multiplexer 413, the peak power of the amplified seed pulse is 1kW, the pulse width is 5ns, and the repetition frequency is 100Hz. The embodiment of the present invention does not impose specific limitations on this.

[0049] Figure 5 The schematic diagram of the structure of the fourth pulse fiber laser with adjustable repetition rate provided by the embodiment of the present invention is shown in FIG. Figure 5The first-stage amplification module 41 includes a second pump source 418, a third pump source 419, a first wavelength division multiplexer 412, a second wavelength division multiplexer 413, a first active optical fiber 414, and a second active optical fiber 415. The output end of the second pump source 418 is connected to the first input end of the first wavelength division multiplexer 412, the second input end of the first wavelength division multiplexer 412 is connected to the second end of the first circulator 51, the output end of the first wavelength division multiplexer 412 is connected to the first end of the first active optical fiber 414, the second end of the first active optical fiber 414 is connected to the second input end of the second wavelength division multiplexer 413, the output end of the third pump source 419 is connected to the first input end of the second wavelength division multiplexer 413, and the output end of the second wavelength division multiplexer 413 is connected to the first end of the second active optical fiber 415. A second pump source 418 and a third pump source 419 are set. The second pump source 418 outputs pump light to the first wavelength division multiplexer 412, and the third pump source 419 outputs pump light to the second wavelength division multiplexer 413. Two pump sources are set to output pump light respectively, so that a larger pump light can be output, the seed pulse can be amplified, and a pulse laser with a larger peak value can be obtained.

[0050] Figure 6 The schematic diagram of the structure of the fifth pulse fiber laser with adjustable repetition rate provided by the embodiment of the present invention is shown in FIG. Figure 6 The first-stage amplification module 41 further includes a first filter 416 and a second filter 417. The input end of the first filter 416 is connected to the second end of the first active optical fiber 414, the output end of the first filter 416 is connected to the second input end of the second wavelength division multiplexer 413, the input end of the second filter 417 is connected to the second end of the second active optical fiber 415, and the output end of the second filter 417 is connected to the second end of the second circulator 52. The filter is used to filter the amplified signal, filter out interference noise, and improve the quality of the output pulse signal.

[0051] Figure 7 The sixth structural diagram of the pulse fiber laser with adjustable repetition rate provided by the embodiment of the present invention is shown in FIG. Figure 7 The secondary amplification module 42 includes a fourth pump source 421, a third wavelength division multiplexer 422 and a third active optical fiber 423. The output end of the fourth pump source 421 is connected to the first input end of the third wavelength division multiplexer 422, the second input end of the third wavelength division multiplexer 422 is connected to the second end of the third circulator 53, and the input and output of the third wavelength division multiplexer 422 are connected to the first end of the third active optical fiber 423. The fourth pump source 421 outputs pump light to the third wavelength division multiplexer 422, and the seed pulse is output to the third active optical fiber 423 after passing through the third wavelength division multiplexer 421, and the third active optical fiber 423 amplifies the seed pulse and outputs it. As an example, the fourth pump source 421 is a 940nm, 70W laser.

[0052] Exemplarily, the third active optical fiber 423 is a double-clad active optical fiber, and the secondary amplification module 42 also includes a cladding light stripper 424, the input end of the cladding light stripper 424 is connected to the second end of the third active optical fiber 423, and the second end of the cladding light stripper 424 is connected to the second end of the fourth circulator 54. Double-clad active optical fiber adds an active layer with an amplifier function on the basis of ordinary single-mode optical fiber, which greatly improves the transmission speed and transmission distance of optical fiber communication, effectively reduces the loss of optical signals, has high anti-interference ability, and stable transmission signals. The cladding light stripper 424 is used to strip the cladding protecting the optical fiber core to facilitate subsequent connections. The cladding light stripper 424 strips the cladding of the third active optical fiber 423 to facilitate subsequent signal transmission.

[0053] As an example, the seed source 20 and the injection source 30 are both distributed Bragg feedback (DFB) 1064nm polarization-maintaining single-frequency semiconductor lasers, and a field-editable gate array is used to form a pulse signal, wherein the injection source 30 is delayed for injection. The seed pulse formed by the seed source 20 is amplified by the first amplification module 41 and the second amplification module 42, and a first circulator 51 is added before the first amplification module 41 for protection, and a third circulator 53 is added before the second amplification module 42 for protection, and finally a pulse laser with a polarization extinction ratio (PER)>20dB, a pulse width of 5ns, a peak power of 40kW, and a repetition frequency range of 1Hz to 10kHz is obtained. Without changing the optical path, a pulse output with a large repetition frequency variation range and a stable high signal-to-noise ratio is achieved, with high safety, stable pulse energy, and anti-return light capability.

[0054] Figure 8 The spectrum diagram of the output laser before injection provided by the embodiment of the present invention, Fig. 9 The spectrum diagram of the laser output after injection provided by the embodiment of the present invention is shown in FIG. Figure 8 and Fig. 9 After adding the injection source 20 and reversely injecting the injection pulse into the amplification module 40, the output pulse laser has better performance, reduces the risk of amplified spontaneous radiation, and stabilizes the high signal-to-noise ratio output.

[0055] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A pulsed fiber laser with adjustable repetition rate, characterized in that: It includes a control module, a seed source, an injection source, at least one amplification module, a first circulator and a second circulator; The control end of the seed source and the control end of the injection source are both connected to the control module, and the control module is used to control the seed source to output a seed pulse with an adjustable repetition frequency, and control the injection source to output an injection pulse with an adjustable repetition frequency; The seed pulse output by the seed source is incident on the first end of the first circulator, the second end of the first circulator is connected to the input end of the amplification module, the output end of the amplification module is connected to the second end of the second circulator, and the injection pulse output by the injection source is incident on the first end of the second circulator; The seed pulse passes through the first end and the second end of the first circulator, is incident on the amplification module for amplification, and is output after passing through the second end and the third end of the second circulator; The injection pulse is reversely injected into the amplification module after passing through the first end and the second end of the second circulator, and the amplified spontaneous radiation generated by the injection pulse is output from the third end of the first circulator; The pulse width of the seed pulse is smaller than the pulse width of the injection pulse, the peak power of the seed pulse is greater than the peak power of the injection pulse, and the start time of the injection pulse is later than the corresponding time of the falling edge of the seed pulse.

2. The pulse fiber laser with adjustable repetition rate according to claim 1, characterized in that: The amplification module includes a primary amplification module and a secondary amplification module, and the pulse fiber laser also includes a third circulator and a fourth circulator; The second end of the first circulator is connected to the input end of the first-stage amplification module, the output end of the first-stage amplification module is connected to the second end of the second circulator, part of the injection pulse output by the injection source is input to the first end of the second circulator, part of the injection pulse is input to the first end of the fourth circulator, the third end of the second circulator is connected to the first end of the third circulator, the second end of the third circulator is connected to the input end of the second-stage amplification module, and the output end of the second-stage amplification module is connected to the second end of the fourth circulator.

3. The pulse fiber laser with adjustable repetition rate according to claim 2, characterized in that: The first-stage amplification module includes a first pump source, an optical fiber beam splitter, a first wavelength division multiplexer, a second wavelength division multiplexer, a first active optical fiber and a second active optical fiber; The output end of the first pump source is connected to the input end of the optical fiber splitter, the first output end of the optical fiber splitter is connected to the first input end of the first wavelength division multiplexer, the second output end of the optical fiber splitter is connected to the first input end of the second wavelength division multiplexer, the second input end of the first wavelength division multiplexer is connected to the second end of the first circulator, the output end of the first wavelength division multiplexer is connected to the first end of the first active optical fiber, the second end of the first active optical fiber is connected to the second input end of the second wavelength division multiplexer, and the output end of the second wavelength division multiplexer is connected to the first end of the second active optical fiber.

4. The pulsed fiber laser with adjustable repetition rate according to claim 2, characterized in that: The first-stage amplification module includes a second pump source, a third pump source, a first wavelength division multiplexer, a second wavelength division multiplexer, a first active optical fiber, and a second active optical fiber; The output end of the second pump source is connected to the first input end of the first wavelength division multiplexer, the second input end of the first wavelength division multiplexer is connected to the second end of the first circulator, the output end of the first wavelength division multiplexer is connected to the first end of the first active optical fiber, the second end of the first active optical fiber is connected to the second input end of the second wavelength division multiplexer, the output end of the third pump source is connected to the first input end of the second wavelength division multiplexer, and the output end of the second wavelength division multiplexer is connected to the first end of the second active optical fiber.

5. The pulse fiber laser with adjustable repetition rate according to claim 3 or 4, characterized in that: The first-stage amplification module also includes a first filter and a second filter, wherein the input end of the first filter is connected to the second end of the first active optical fiber, the output end of the first filter is connected to the second input end of the second wavelength division multiplexer, the input end of the second filter is connected to the second end of the second active optical fiber, and the output end of the second filter is connected to the second end of the second circulator.

6. The pulse fiber laser with adjustable repetition rate according to claim 2, characterized in that: The secondary amplification module includes a fourth pump source, a third wavelength division multiplexer and a third active optical fiber; The output end of the fourth pump source is connected to the first input end of the third wavelength division multiplexer, the second input end of the third wavelength division multiplexer is connected to the second end of the third circulator, and the output end of the third wavelength division multiplexer is connected to the first end of the third active optical fiber.

7. The pulse fiber laser with adjustable repetition rate according to claim 6, characterized in that: The third active optical fiber is a double-clad active optical fiber, and the secondary amplification module further includes a cladding light stripper, an input end of the cladding light stripper is connected to the second end of the third active optical fiber, and an output end of the cladding light stripper is connected to the second end of the fourth circulator.

8. The pulsed fiber laser with adjustable repetition rate according to claim 1, characterized in that: Also included is a collimator located at the output end of the pulse fiber laser.

9. The pulsed fiber laser with adjustable repetition rate according to claim 1, characterized in that: The control module comprises a field editable gate array, and the seed source and the injection source both comprise distributed Bragg feedback single-frequency semiconductor lasers.

10. The pulse fiber laser with adjustable repetition rate according to claim 1, characterized in that: The repetition frequency of the pulsed fiber laser output pulse can be adjusted in the range of 1Hz~10kHz.

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