A pulsed continuous composite tunable fiber laser

Abstract

The invention discloses a pulse continuous composite tunable fiber laser, comprising a pulse laser seed source, a first online fiber isolator, an amplification module and an output optical isolation connected in sequence through optical fibers; adjusting the seed pulse light parameters to form small signal amplification, in an amplification module with an amplification factor of 100-2000 times, a small part of the pump light amplifies the pulse seed light emitted by the pulse laser seed source to a pulse light of the order of milliwatts to hundreds of milliwatts, and the remaining majority of the pump light not consumed by the pulse seed light generates a base of ASE mixed with continuous light in a resonant cavity composed of a first high reflectivity grating and a first low reflectivity grating, thereby outputting a mixed light of the pulse light and the continuous light after the amplification module. The invention combines grating filtering and a continuous bottom, is conducive to suppressing nonlinearity, optimizing the spectrum, thereby generating higher power output and high beam quality, and only requires one seed source, thereby reducing costs.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber lasers, and in particular to a pulse continuous composite tunable optical fiber laser. Background Art

[0002] At present, the market for fiber lasers and fiber laser processing applications is expanding rapidly. The competition between single continuous lasers and pulsed lasers based on their respective characteristics is very fierce. The use of pulsed / continuous composite lasers can not only greatly improve processing efficiency, but also expand the traditional single laser processing field. Pulsed / continuous composite lasers have been applied in laser drilling, laser scribing, laser composite cleaning, laser 3D printing and other fields.

[0003] At present, the traditional way of pulse / continuous composite laser is to combine a continuous laser and a pulse laser, and output the continuous laser and the pulse laser by spatial or fiber coupling. The use of two laser systems is expensive, bulky, difficult to couple different optical fibers, and complex control systems. The inconvenience of actual use limits the expansion of composite laser applications in the field of processing. Summary of the invention

[0004] The main purpose of the present invention is to provide a pulse continuous composite tunable fiber laser, which reduces the cost while ensuring the performance.

[0005] The technical solution adopted by the present invention is: a pulse continuous composite tunable fiber laser, characterized in that it includes a pulse laser seed source, a first online fiber isolator, an amplification module and an output optical isolation connected in sequence through optical fibers; the amplification module is at least one level, a second online fiber isolator is provided between each level of amplification modules, and the amplification factor of each level of amplification module is 100-2000 times; wherein the first level amplification module includes a first fiber coupler, a first high reflectivity grating, a first gain fiber and a first low reflectivity grating connected in series in sequence to the rear end of the first online fiber isolator, and a first pump source connected to the first fiber coupler; the power of the pulse laser seed source is 60μW-1mW, and the pulse frequency is 0.1KHz-500KHz; the power of the first pump source is watt-level; The first pump source emits pump light, and a small part of the pump light amplifies the pulse seed light emitted by the pulse laser seed source to a pulse light of the order of milliwatts to hundreds of milliwatts. The remaining majority of the pump light not consumed by the pulse seed light generates a substrate for mixing ASE and continuous light under the resonant cavity formed by the first high reflectivity grating and the first low reflectivity grating, thereby outputting a mixed light of the pulse light and continuous light after the amplification module.

[0006] According to the above scheme, a passive transmission optical fiber is added between the first gain optical fiber and the first low reflectivity grating to increase the cavity length of the resonant cavity; the length of the passive transmission optical fiber is 20m-2000m.

[0007] According to the above solution, the grating line width of the first low reflectivity grating is smaller than the grating line width of the first high reflectivity grating, and the grating line widths of the first high reflectivity grating and the first low reflectivity grating are both in the range of 1.5nm-10nm.

[0008] According to the above scheme, the amplitude ratio of the output pulse light and continuous light is adjusted by controlling the current of the pump source in at least one stage of the amplification module, and the pump source is a pulse pump or a continuous pump.

[0009] According to the above scheme, the first pump source is a pulse pump source, and the pulse frequency is the same as the pulse frequency of the pulse laser seed source; by adjusting the driving mode of the pulse pump source, the intensity variation trend of the bottom continuous light is controlled.

[0010] According to the above scheme, according to the pulse frequency of the pulse pump source, the time of one cycle of the pulse pump source is divided into t1 and t2, where t1 is the pump current time occupied by the pulse light, and t2 is the pump current time occupied by the continuous light;

[0011] The driving mode of the pump source is falling edge pumping, that is, the input pulse light absorbs the pump energy within time t1 to amplify; the amplitude of the pulse pump peak current (I1) at time t1 is adjusted to control the pulse light amplification intensity; the current size (I2) and growth trend within time t2 of the continuous light pumping before and after the pulse pumping are adjusted to adjust the continuous light intensity change trend.

[0012] According to the above scheme, the amplification module includes the first-stage amplification module, as well as a pulse light amplification module and a continuous light amplification module; wherein, after the rear end of the first-stage amplification module passes through the second online optical fiber isolator, it is divided into two paths through a photoelectric regulator, namely pulse light and continuous light, which are independently amplified and outputted through the pulse light amplification module and the continuous light amplification module respectively, and an output optical isolator is respectively arranged behind the pulse light amplification module and the continuous light amplification module.

[0013] According to the above scheme, a beam combiner is provided after the output light barrier, which is used to combine the independently amplified output pulse light and continuous light for output.

[0014] According to the above scheme, the reflectivity of the first high-reflectivity grating is 99.9%, and the reflectivity of the first low-reflectivity grating is 0.1%-20%.

[0015] The beneficial effects produced by the present invention are:

[0016] 1. A pulsed laser seed source of a certain frequency is injected into an adjustable pump amplifier module, and a small signal amplification pump is used to absorb incomplete spontaneous radiation to generate continuous light. At the same time, filter devices (high reflectivity gratings, low reflectivity gratings) are used to suppress the generation of stray waves and the subsequent amplification of wide-spectrum ASE. The first-stage amplification realizes the synchronous and adjustable power amplification of pulsed light and continuous light. The present invention combines grating filtering and continuous bottom, which is conducive to suppressing nonlinearity and optimizing the spectrum, thereby generating higher power output and high beam quality, thereby improving the processing technology efficiency in application fields such as laser drilling, laser scribing, laser composite cleaning, and 3D printing. The present invention does not require the synthesis of continuous light modules and pulse light modules, but adopts an all-fiber single module structure to simultaneously generate pulses and continuous mixed light, with high integration, greatly saving costs, and easy to realize industrialization.

[0017] 2. By adding passive transmission optical fiber in the resonant cavity to increase the cavity length, the continuous bottom power jitter is optimized, which is more conducive to post-stage amplification.

[0018] 3. Control the pump source driving mode to achieve the generation of continuous light at the front and rear edges of the pulse, and compound lasers in multiple ways to expand the adjustment accuracy and application methods of cleaning applications.

[0019] 4. Compared with the traditional combination of a single continuous laser and a single pulse laser, the laser of the present application can achieve an adjustable bottom continuous light trend in the final generated composite light. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0021] Figure 1 It is a schematic diagram of the optical path structure of the first embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the improvement of the bottom jitter of continuous light.

[0023] Figure 3 This is a diagram of the optimization of the spectrum by bottom lifting of continuous light.

[0024] Figure 4 This is the correspondence diagram between the front-end pump current and the output light pulse waveform.

[0025] Figure 5 This is the corresponding diagram between the rear-stage pump current and the output light pulse waveform.

[0026] Figure 6 It is a schematic diagram of the optical path structure of the second embodiment of the present invention.

[0027] Figure 7 It is a schematic diagram of the optical path structure of the third embodiment of the present invention.

[0028] In the figure, 1-pulse laser seed source, 2-first online fiber isolator, 3-first fiber coupler, 4-first pump source, 5-first high reflectivity grating, 6-first gain fiber, 7-passive transmission fiber, 8-first low reflectivity grating, 9-second online fiber isolator, 10-second fiber coupler, 11-second pump source, 12-second gain fiber, 13-second high reflectivity grating, 14-second low reflectivity grating, 15-output optical isolator;

[0029] 11-1-second pulse pump source, 12-1-second pulse gain fiber, 13-1-second pulse high reflectivity grating, 14-1-second pulse low reflectivity grating, 15-1-pulse output optical barrier; 11-2-second continuous pump source, 12-2-second continuous gain fiber, 13-2-second continuous high reflectivity grating, 14-2-second continuous low reflectivity grating, 15-2-continuous output optical barrier; 16-photoelectric regulator, 17-beam combiner. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] Embodiment 1:

[0032] like Figure 1 As shown, this embodiment provides a pulse continuous composite tunable fiber laser, including a pulse laser seed source 1, a first online fiber isolator 2, an amplification module and an output optical isolator 15 connected in sequence through optical fibers.

[0033] The amplifier module has two levels, and the amplification factor of each amplifier module is 100-2000 times. Among them, the first-stage amplifier module includes a first fiber coupler 3, a first high reflectivity grating 5, a first gain fiber 6 and a first low reflectivity grating 8, which are sequentially connected to the rear end of the first online fiber isolator 2, and a first pump source 4 connected to the first fiber coupler 3. A second online fiber isolator 9 is provided between the first-stage amplifier module and the second-stage amplifier module. The second-stage amplifier module includes a second fiber coupler 10, a second high reflectivity grating 13, a second gain fiber 12, a second low reflectivity grating 14, which are sequentially connected to the rear end of the second online fiber isolator 9, and a second pump source 11 connected to the second fiber coupler 10. The rear end of the second low reflectivity grating 14 is connected to the output optical isolator 15. The number of amplifier modules is set as needed, generally 1-2 levels. Of course, according to specific needs, the number of amplifier modules can also be greater than 2.

[0034] In this embodiment, the power of the pulse laser seed source 1 is 60μW-1mW, and the pulse frequency is 0.1KHz-500KHz; the power of the first pump source 4 is in the watt level. The pulse light emitted by the pulse laser seed source 1 consumes a small part of the pump light in the first-stage amplifier module, thereby amplifying to the order of a few milliwatts to hundreds of milliwatts; in the resonant cavity formed by the first high-reflectivity grating 5 and the first low-reflectivity grating 8, there is still a large part of the pump light that is not consumed by the pulse light. The amplification factor of 100-2000 times and the resonant cavity will generate spontaneous radiation ASE and continuous light mixed substrate. The amplification factor refers to the ratio of the total power of the amplified output mixed light to the power of the input pulse light.

[0035] In the second-stage amplification module, the bottom of continuous light cannot be effectively amplified. In order to avoid most of the energy being absorbed by the pulsed light, while increasing the proportion of the continuous value of the first-stage amplification output, the pulsed light is also limited to be used for amplification within a certain range. Therefore, the pulse frequency of the pulse laser seed source 1 is set to 0.1KHz-500kHz, and the pulse continuous composite power is hundreds of milliwatts to watts, where the pulse power can be calculated based on the duty cycle.

[0036] The amplification factor is controlled within 100-2000, and the pulse light forms a small signal that is not enough to take away most of the pump energy, and at the same time, it will not produce excessive ASE to damage the optical fiber.

[0037] The first high reflectivity grating 5 and the second high reflectivity grating 13 have a reflectivity of 99.9%, and the first low reflectivity grating 8 and the second low reflectivity grating 14 have a reflectivity of 0.1%-20%. The resonant cavity formed by each group of high reflectivity gratings and low reflectivity gratings has a certain width spectrum line width screening function. Usually, the grating line width is selected in the range of 1.5nm-10nm. The line widths of the first high reflectivity grating 5 and the first low reflectivity grating 8 can be different, and the grating line width of the first low reflectivity grating is smaller than the grating line width of the first high reflectivity grating. If the line width is large, the spectrum is wide, which is not conducive to the subsequent amplification. The line widths of the second high reflectivity grating and the second low reflectivity grating can be different, and the grating line width is selected in the range of 1.5nm-10nm. The above grating line width range ensures that the residual pump light power of the first-stage amplification module will generate a certain power of continuous light while generating spontaneous radiation ASE; the spontaneous radiation ASE light source generated by the resonant cavity excitation and the continuous light together constitute a continuous bottom output. In addition, the first low-reflectivity grating 8 limits the backward transmission of ASE with a width of tens to hundreds of nanometers.

[0038] Since the generated ASE and continuous optical power jitter are relatively large, it is preferred to add a passive transmission fiber 7 after the first gain fiber to increase the cavity length of the resonant cavity. The length of the passive transmission fiber is 20m-2000m. Within a certain range, the longer the cavity length, the larger the longitudinal mode interval, and the fewer the number of modes included, which can greatly improve the continuous optical jitter on the nanosecond scale. The effect of the base jitter improvement before and after is shown in the figure. Figure 2 As shown, the waveform ripple is before improvement, and the straight line is after improvement. It can be seen that the waveform is smooth and has no jitter after improvement.

[0039] Furthermore, the power that can be amplified by the small signal pulse light increases slowly. After reaching a certain power, the base continuous light power growth rate will be greater than the pulse light. Therefore, the amplitude ratio of the output pulse light to the continuous light can be adjusted by controlling the current of the pump source in at least one stage of the amplification module. In this embodiment, only the current of the first pump source 4 can be adjusted, or the currents of the first pump source 4 and the second pump source 11 can be adjusted at the same time.

[0040] Due to the existence of the continuous light bottom, compared with the use of simple pulse amplification, the spectrum optimization is obvious at the same output power, such as Figure 3 It can be seen that the first and second stage amplification modules of this embodiment can amplify the power to the kilowatt level output, greatly improving the output power of the traditional single pulse laser. At the same time, the first and second gain fibers (6, 12) can be selected from low absorption coefficient fibers, thereby significantly improving the heat dissipation conditions of the gain fibers, and can further increase the input pump to improve the output power.

[0041] On the basis of the above, it is further preferred that the first pump source 4 is a pulse pump source, and the pulse frequency is the same as the pulse frequency of the pulse laser seed source 1; the intensity change trend of the bottom continuous light is controlled by adjusting the driving mode of the first pump source 4. When the amplification module is multi-stage, each pump source can be a pulse pump source, and only the current of the first pump source 4 of the first-stage amplification module can be adjusted, or the current of the pump source in any one or more amplification modules in the remaining amplification modules can be adjusted while adjusting the first pump source.

[0042] In this embodiment, Figure 4 and Figure 5As shown, according to the pulse frequency of the pulse pump source, the time of one cycle of the pulse pump source is divided into t1 and t2, where t1 is the pump current time occupied by the pulse light, and t2 is the pump current time occupied by the continuous light; the driving mode of the pump source is falling edge pumping, that is, the input pulse light absorbs the pump energy in t1 time to amplify; adjust the amplitude of the pulse pump peak current (I1) at t1 time to control the pulse light amplification intensity; adjust the current size (I2) and growth trend in the continuous light pump time t2 before and after the pulse pump, so as to adjust the continuous light intensity change trend. After the pulse pumping, the pumping trend gradually decreases, and the remaining pumping energy is enough to generate the continuous light bottom or amplify the continuous light bottom, which is the rear continuous bottom; after the pulse light amplification, the pump energy gradually increases from the bottom to the front continuous bottom, which will gradually increase before the pulse light is generated.

[0043] Figure 4 The upper part is the pump current waveform, and the lower part is the output light pulse waveform; Figure 5 The upper part is the pump current waveform, and the lower part is the output light pulse waveform. By adjusting the pump source driving mode, the bottom continuous light trend can be controlled to form Figure 4 and Figure 5 The continuous intensity and time adjustable optical pulse waveform shown is used Figure 4 The light pulse waveform corresponding to the front continuous base segment (i.e., the front continuous bottom) can be used to heat the material surface, and the heat accumulation will be beneficial to the surface material treatment by the pulse light. Figure 5 The light pulse waveform corresponding to the obtained rear continuous substrate segment (i.e., the rear continuous bottom) can be used for re-polishing and other treatments after the pulse light acts on the surface of the material.

[0044] In addition, the first pump source can also be a continuous pump source, and the pulse light amplification intensity and the continuous light intensity change trend can be controlled by adjusting the current of the continuous pump source. When the amplification module is multi-stage, each pump source can be a continuous pump source, and the current of the continuous pump source in any one or more of the remaining amplification modules can be adjusted while adjusting the first pump source.

[0045] Embodiment 2:

[0046] This embodiment is a variation of the first embodiment, and its principle and structure are similar to those of the first embodiment, except that: Figure 6As shown, the amplification module includes the first-stage amplification module, as well as the pulse light amplification module and the continuous light amplification module; wherein, after the rear end of the first-stage amplification module passes through the second online optical fiber isolator 9, it is divided into two paths through the photoelectric regulator 16, namely pulse light and continuous light, which are independently amplified and output through the pulse light amplification module and the continuous light amplification module, respectively. The pulse light amplification module and the continuous light amplification module are each provided with an output light partition, namely, a pulse output light partition 15-1 and a continuous output light partition 15-2. The advantage of this solution is that the pulse light and the continuous light can be independently amplified and output according to the needs, and finally two beams of adjustable lasers are obtained, which are suitable for a variety of application scenarios.

[0047] Embodiment three:

[0048] This embodiment is a variation of the second embodiment. Figure 7 As shown, a beam combiner 17 is provided after the pulse output light interval 15-1 and the continuous output light interval 15-2, which is used to combine the independently amplified pulse light and the continuous light for output. The advantage of this solution is that the pulse light and the continuous light can be independently amplified according to the demand. Although a mixed light is finally formed, the laser amplification technology of each group is mature and adjustable, which can maximize the power amplification of the continuous component.

[0049] In summary, the pulse continuous composite tunable fiber laser proposed in this application forms small signal amplification by adjusting the seed pulse light parameters, generates pulse and continuous composite laser output in the resonant cavity, and can achieve adjustable amplitude ratio of each component.

[0050] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A pulse continuous composite tunable fiber laser, characterized in that: It includes a pulse laser seed source, a first online optical fiber isolator, an amplification module and an output optical isolator which are sequentially connected through optical fibers; The amplification module is at least one stage, and a second online optical fiber isolator is provided between each stage of the amplification module. The amplification factor of each stage of the amplification module is 100-2000 times; wherein the first stage amplification module comprises a first optical fiber coupler, a first high reflectivity grating, a first gain optical fiber and a first low reflectivity grating which are serially connected to the rear end of the first online optical fiber isolator in sequence, and a first pump source connected to the first optical fiber coupler; The power of the pulse laser seed source is 60μW-1mW, and the pulse frequency is 0.1KHz-500KHz; the power of the first pump source is watt-level; The first pump source emits pump light, and a small part of the pump light amplifies the pulse seed light emitted by the pulse laser seed source to a pulse light of the order of milliwatts to hundreds of milliwatts. The remaining majority of the pump light not consumed by the pulse seed light generates a base of ASE mixed with continuous light under the resonant cavity formed by the first high reflectivity grating and the first low reflectivity grating, thereby outputting a mixed light of the pulse light and continuous light after the amplification module.

2. The pulse continuous composite tunable fiber laser according to claim 1, characterized in that: A passive transmission optical fiber is added between the first gain optical fiber and the first low reflectivity grating to increase the cavity length of the resonant cavity; the length of the passive transmission optical fiber is 20m-2000m.

3. The pulse continuous composite tunable fiber laser according to claim 1, characterized in that: The grating line width of the first low-reflectivity grating is smaller than the grating line width of the first high-reflectivity grating, and the grating line widths of the first high-reflectivity grating and the first low-reflectivity grating are both in the range of 1.5nm-10nm.

4. The pulse continuous composite tunable fiber laser according to claim 1, characterized in that: The amplitude ratio of the output pulse light and the continuous light is adjusted by controlling the current of the pump source in at least one stage of the amplification module, and the pump source is a pulse pump source or a continuous pump source.

5. The pulse continuous composite tunable fiber laser according to claim 1, characterized in that: The first pump source is a pulse pump source, and the pulse frequency is the same as the pulse frequency of the pulse laser seed source; by adjusting the driving mode of the pulse pump source, the intensity variation trend of the bottom continuous light is controlled.

6. The pulse continuous composite tunable fiber laser according to claim 5, characterized in that: According to the pulse frequency of the pulse pump source, the time of one cycle of the pulse pump source is divided into t1 and t2, wherein t1 is the pump current time occupied by the pulse light, and t2 is the pump current time occupied by the continuous light; The driving mode of the pump source is falling edge pumping, that is, the input pulse light absorbs the pump energy within the time t1 to amplify; Adjust the amplitude of the pulse pump peak current (I1) at time t1 to control the pulse light amplification intensity; The current size (I2) and growth trend during the continuous light pumping time t2 before and after the pulse pumping are adjusted, thereby adjusting the continuous light intensity change trend.

7. The pulse continuous composite tunable fiber laser according to claim 1, characterized in that: The amplification module includes the first-stage amplification module, a pulse light amplification module and a continuous light amplification module; wherein, after the rear end of the first-stage amplification module passes through the second online optical fiber isolator, it is divided into two paths through a photoelectric regulator, namely pulse light and continuous light, which are independently amplified and outputted through the pulse light amplification module and the continuous light amplification module respectively, and an output optical isolator is respectively arranged behind the pulse light amplification module and the continuous light amplification module.

8. The pulse continuous composite tunable fiber laser according to claim 7, characterized in that: A beam combiner is arranged behind the output light barrier, which is used to combine the independently amplified output pulse light and continuous light for output.

9. The pulse continuous composite tunable fiber laser according to claim 1, characterized in that: The reflectivity of the first high-reflectivity grating is 99.9%, and the reflectivity of the first low-reflectivity grating is 0.1%-20%.

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