Relaxation oscillation suppression high-power quasi-continuous thulium-doped fiber laser

Abstract

The utility model discloses a relaxation oscillation suppression high-power quasi-continuous thulium-doped fiber laser. The relaxation oscillation suppression high-power quasi-continuous thulium-doped fiber laser comprises a multi-wavelength hybrid pump, a wavelength division multiplexer, a first fiber bragg grating, a thulium-doped fiber, a second fiber bragg grating and a cladding stripper which are connected in sequence, the multi-wavelength hybrid pump comprises a bias pump source and a plurality of pulse pump sources; the output ends of the plurality of pulse pumping sources are connected with the input end of the wavelength division multiplexer; the bias pumping source is connected with one end of the third fiber bragg grating, the other end of the third fiber bragg grating is connected with one end of the erbium-ytterbium co-doped fiber, the other end of the erbium-ytterbium co-doped fiber is connected with one end of the fourth fiber bragg grating, and the other end of the fourth fiber bragg grating is connected with the input end of the wavelength division multiplexer. The laser provided by the utility model not only can stably suppress relaxation oscillation, but also can greatly reduce the power of the bias continuous substrate required in a light path, thereby reducing the power consumption and heat productivity of the laser, and avoiding destructive influence on a processing environment and acting substances.

Description

Technical Field

[0001] The utility model relates to the technical field of lasers, in particular to a high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression. Background Art

[0002] Quasi-continuous fiber lasers generally use electric pulse modulation pump sources to generate quasi-continuous lasers. During the pulse pumping process, before the resonant cavity establishes laser oscillation, the number of upper energy level inversion particles and the laser gain are much larger than the laser oscillation threshold. When the resonant cavity establishes laser oscillation, the accumulated upper energy level inversion particle number will be quickly released, resulting in a pulse far higher than the steady-state peak at the leading edge of each quasi-continuous pulse, i.e., relaxation oscillation. Relaxation oscillation will cause the peak power of the laser fiber to far exceed its design value, increasing the risk of fiber burnout. At the same time, it will also reduce the nonlinear threshold in the fiber and reduce the conversion efficiency of the system. Therefore, in quasi-continuous fiber lasers, relaxation oscillations generally need to be suppressed.

[0003] In 1μm ytterbium-doped fiber lasers, the more commonly used method to suppress relaxation oscillations is bias current pumping, that is, when the electric pulse modulated pump source is turned on, it is not turned on from zero, but a smaller value (i.e. bias current) is turned on in advance. Under the pumping of bias current, the resonant cavity is above the laser oscillation threshold and can output continuous light of lower power. Since the laser is continuously output, when the quasi-continuous electric pulse modulated pump source is output, the laser can be output directly without waiting for the resonant cavity to establish laser oscillation, so relaxation oscillations can be suppressed.

[0004] However, in 1.6-2μm thulium-doped fiber lasers, to achieve high-power quasi-continuous output, only 793nm semiconductor laser pumping can be used, because 793nm semiconductor lasers can easily achieve high-power pumping. However, high-power pumping has cross relaxation, and the energy level of thulium-doped fiber is complex, so the simple bias current pumping scheme cannot suppress relaxation oscillation well. At the same time, the use of bias current pumping method to suppress relaxation oscillation will lead to the presence of strong continuous base laser in quasi-continuous laser, thereby increasing the actual average power, increasing power consumption and increasing the heat generation of the laser. In addition, the continuous base laser will continue to heat the laser action material, which will have a destructive effect on the processing environment and the action material.

[0005] Therefore, it is necessary to propose a high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression, which can effectively suppress relaxation oscillations when outputting high-power quasi-continuous lasers, and reduce the biased continuous substrate power and the heat generated by the laser to avoid affecting the processing environment and the active material. Utility Model Content

[0006] In view of this, it is necessary to provide a high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression to solve the technical problems that the existing lasers cannot effectively suppress relaxation oscillations during high-power continuous output, and have high heat generation and destructive effects on the acting substances.

[0007] In order to achieve the above technical purpose, the utility model adopts the following technical solutions:

[0008] The utility model provides a high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression, comprising a multi-wavelength hybrid pump, a wavelength division multiplexer, a first fiber grating, a thulium-doped fiber, a second fiber grating and a cladding stripper connected in sequence;

[0009] The multi-wavelength hybrid pump includes a bias pump source and a plurality of pulse pump sources; the output ends of the plurality of pulse pump sources are all connected to the input end of the wavelength division multiplexer; the bias pump source is connected to one end of a third fiber grating, the other end of the third fiber grating is connected to one end of an erbium-ytterbium co-doped fiber, the other end of the erbium-ytterbium co-doped fiber is connected to one end of a fourth fiber grating, and the other end of the fourth fiber grating is connected to the input end of the wavelength division multiplexer.

[0010] Furthermore, the pulse pump source and the bias pump source are both semiconductor lasers.

[0011] Furthermore, the laser emission wavelength of the bias pump source is 940 nanometers.

[0012] Furthermore, the laser emission wavelength of the pulse pump source is 793 nanometers.

[0013] Further, the multi-wavelength hybrid pump also includes a bias current source, and the bias current source is connected to the bias pump source;

[0014] When the bias pump source and the plurality of pulse pump sources are turned on, the bias current source outputs a bias current, so that the resonant cavity composed of the third fiber grating, the erbium-ytterbium co-doped fiber and the fourth fiber grating outputs continuous base laser.

[0015] Furthermore, the power range of the continuous substrate laser is 1-5 milliwatts.

[0016] Furthermore, the wavelength division multiplexer is a combiner.

[0017] Furthermore, the first fiber grating and the third fiber grating are high-reflection gratings; the second fiber grating and the fourth fiber grating are low-reflection gratings.

[0018] Furthermore, the reflectivity of the low-reflection grating is 8%.

[0019] Furthermore, the reflectivity of the high-reflection grating is not less than 95%.

[0020] Compared with the prior art, the beneficial effects of the utility model include: the laser adopts multi-wavelength hybrid pumping, the main output power pump source uses multiple pulse pump sources, and then the laser emitted by the bias pump makes part of the thulium ions work at the second energy level or quasi-second energy level, which is beneficial to ensure that the laser upper energy level ( 3 F4) The particle number is in a controllable state, and the bias pump power can be reduced while suppressing laser relaxation oscillation, thereby reducing the power of the continuous base in the final output waveform. The relaxation oscillation suppression high-power quasi-continuous thulium-doped fiber laser provided by the utility model can not only stably suppress the relaxation oscillation existing in the laser during high-power quasi-continuous output, but also greatly reduce the bias continuous base power in the optical path, reduce the power consumption and heat generation of the laser, and avoid destructive effects on the processing environment and the active material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of the energy levels of the thulium-doped optical fiber provided by the utility model;

[0022] Figure 2 A schematic diagram of relaxation oscillation peak values ​​of different light pulses provided by the utility model;

[0023] Figure 3 This is an optical path structure diagram of a high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression provided by the utility model;

[0024] Figure 4 A schematic diagram of the laser pump current and laser waveform provided by the utility model;

[0025] In the figure, 1-multi-wavelength hybrid pump; 2-wavelength division multiplexer; 3-first fiber Bragg grating; 4-thulium-doped fiber; 5-second fiber Bragg grating; 6-cladding stripper; 10-bias pump source; 11-third fiber Bragg grating; 12-erbium-ytterbium co-doped fiber; 13-fourth fiber Bragg grating; 20-pulse pump source. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0027] In the description of the present application, “plurality” means two or more than two, unless otherwise clearly and specifically defined.

[0028] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0029] Before describing the embodiment of the present utility model, the concept of the embodiment is first introduced and described.

[0030] In 1.6-2μm thulium-doped fiber lasers, to achieve high-power quasi-continuous output, only 793nm semiconductor lasers can be used for pumping. 793nm semiconductor lasers can easily achieve high-power pumping, but cross relaxation also exists. Figure 1 As shown, Figure 1 The energy level diagram of thulium-doped fiber is shown. Due to the complex energy level of thulium-doped fiber, the simple bias current pumping scheme cannot effectively suppress the relaxation oscillation. In the high-power quasi-continuous thulium-doped fiber laser pumped at 793nm, the relaxation oscillation is suppressed by direct bias pumping in the 1μm ytterbium-doped fiber laser, such as Figure 2 As shown, due to the complex energy level structure of thulium ions pumped at 793nm, in addition to cross relaxation, there are also multiple energy transfer upconversions, which makes the laser upper energy level ( 3 F4) The number of particles is uncontrollable, resulting in different relaxation oscillation peaks for each pulse, which is in an uncontrollable state. Therefore, the optical path structure and processing method used in 1μm ytterbium-doped fiber lasers are not suitable for 1.6-2μm thulium-doped fiber lasers that need to achieve high-power quasi-continuous output.

[0031] In addition, using the bias current pumping method to suppress relaxation oscillations will result in the presence of a stronger continuous base laser in the quasi-continuous laser, increasing the actual average power, thereby increasing the power consumption and heat generation of the laser, which has an adverse effect in the application scenario. The continuous base laser will continue to heat the laser action material, causing a destructive effect on the processing environment and the action material.

[0032] Based on the above analysis, the utility model proposes a high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression. The specific principle is to use multi-wavelength hybrid pumping. The pump source as the main output power is still pumped by a 793nm semiconductor laser, and the bias pump wavelength is changed to around 1.2μm or 1.6μm, so that part of the thulium ions work at the second energy level or quasi-second energy level, which is beneficial to relatively simple energy levels to ensure that under a smaller bias power pump, the laser upper energy level ( 3 F4) The particle number is in a controllable state, suppressing laser relaxation oscillation while reducing the bias pump power.

[0033] The utility model provides a high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression. Figure 3 , Figure 3 A schematic diagram of the structure of a high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression provided in this embodiment, comprising a multi-wavelength hybrid pump 1, a wavelength division multiplexer 2, a first fiber grating 3, a thulium-doped fiber 4, a second fiber grating 5 and a cladding stripper 6 connected in sequence;

[0034] The multi-wavelength hybrid pump 1 includes a bias pump source 10 and a plurality of pulse pump sources 20; the output ends of the plurality of pulse pump sources 20 are all connected to the input end of the wavelength division multiplexer 2; the bias pump source 10 is connected to one end of a third fiber grating 11, the other end of the third fiber grating 11 is connected to one end of an erbium-ytterbium co-doped fiber 12, the other end of the erbium-ytterbium co-doped fiber 12 is connected to one end of a fourth fiber grating 13, and the other end of the fourth fiber grating 13 is connected to the input end of the wavelength division multiplexer 2.

[0035] The high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression provided in this embodiment adopts multi-wavelength hybrid pumping, and the pump source of the main output power selects multiple pulse pump sources, and then the laser emitted by the bias pump is used to make part of the thulium ions work at the second energy level or quasi-second energy level, which is beneficial to ensure that the laser upper energy level ( 3 F4) The particle number is in a controllable state, and the bias pump power can be reduced while suppressing laser relaxation oscillation, thereby reducing the power of the continuous base in the final output waveform. The relaxation oscillation suppression high-power quasi-continuous thulium-doped fiber laser of this embodiment can not only stably suppress relaxation oscillation, but also greatly reduce the bias continuous base power in the optical path, reduce power consumption and heat generation of the laser, and avoid affecting the processing environment and the active material.

[0036] In some embodiments, the pulse pump source and the bias pump source are both semiconductor lasers.

[0037] Semiconductor lasers (LDs) can effectively convert electrical energy into light energy and have high energy conversion efficiency. Compared with other types of lasers, semiconductor lasers usually have a longer service life and higher reliability. They do not require frequent maintenance, can work stably for a long period of time, and can provide strong pump power for lasers or amplifiers.

[0038] In some embodiments, the laser emission wavelength of the bias pump source is 940 nanometers, and the laser emission wavelength of the pulse pump source is 793 nanometers.

[0039] Combination Figure 3For explanation, the bias pump source 10 uses a 940nm LD laser, and the erbium-ytterbium co-doped fiber 12 is a specially designed optical fiber in which erbium ions and ytterbium ions are co-doped into the material of the optical fiber. After receiving the 940nm pump laser, this optical fiber can emit a laser with a wavelength of 1550nm (near 1.2μm or 1.6μm), which can make some thulium ions work at the second energy level or quasi-second energy level; multiple pulse pump sources 20 are still pumped by 793nm semiconductor lasers, which can easily achieve high-power pumping.

[0040] The above arrangement can be used to ensure that the upper laser level ( 3 F4) The particle number is in a controllable state, suppressing laser relaxation oscillation while reducing the bias pump power.

[0041] As a preferred embodiment, the multi-wavelength hybrid pump further includes a bias current source, and the bias current source is connected to the bias pump source;

[0042] When the bias pump source and the plurality of pulse pump sources are turned on, the bias current source outputs a bias current, so that the resonant cavity composed of the third fiber grating, the erbium-ytterbium co-doped fiber and the fourth fiber grating outputs a continuous base laser. Under the pumping of the bias current, the resonant cavity is above the laser oscillation threshold and can output continuous light of relatively low power.

[0043] As a preferred embodiment, the power range of the continuous substrate laser is 1-5 mW.

[0044] In order to illustrate the actual suppression effect of the laser of this embodiment on relaxation oscillation, as a specific embodiment, the measured results of turning on the bias pump source and turning off the bias pump source are compared:

[0045] When the 1550nm bias pump generated by the 940nm LD pumping Er-Yb co-doped fiber is not turned on, and the 793nm LD plus bias current is directly used to suppress the relaxation oscillation (this is the traditional optical path mode), the bias current needs to be increased. When the continuous base power is adjusted to 2-5W, the relaxation oscillation peak can be suppressed to within 2 times of the steady-state peak, and the relaxation oscillation peak of each waveform fluctuates greatly.

[0046] When the 940nm LD in this optical path is turned on to pump the Er-Yb co-doped fiber to generate a 1550nm bias pump, only 1-5mW of continuous base power needs to be output, and the relaxation oscillation peak value can be lower than the steady-state peak value, and each waveform has no relaxation oscillation. Figure 4 As shown, Figure 4The schematic diagram of each waveform of the high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression provided by this embodiment is shown. It can be seen that the relaxation oscillation can be effectively suppressed by turning on or off the 940nm LD bias pump in this optical path as needed. When the 940nm LD pump is turned on, only a very low base power is required to achieve effective suppression of relaxation oscillations, so that the bias continuous power base is reduced by three orders of magnitude compared to the conventional solution (from the need to increase the continuous base power of 2-5W to the continuous base power of 1-5mW).

[0047] While suppressing the relaxation oscillation of the high-power quasi-continuous thulium-doped fiber laser, the biased continuous substrate power is reduced, the power consumption of the laser and the heat generated by the laser are reduced, and destructive effects on the processing environment and the active material are avoided.

[0048] As a preferred embodiment, the wavelength division multiplexer is a combiner.

[0049] The beam combiner is used to combine multiple optical signals of different wavelengths into one beam, or to separate signals of different wavelengths in one beam, thereby realizing optical wavelength division multiplexing and allowing multiple independent optical signals to be transmitted on a single optical fiber.

[0050] As a preferred embodiment, the first fiber grating and the third fiber grating are high-reflection gratings; the second fiber grating and the fourth fiber grating are low-reflection gratings.

[0051] It should be noted that the first fiber grating, thulium-doped fiber and the second fiber grating constitute the first resonant cavity, providing positive feedback for the establishment of laser oscillation; the third fiber grating, erbium-ytterbium co-doped fiber and the fourth fiber grating constitute the second resonant cavity, so that the laser output by the bias pump can achieve total reflection of the laser, so that the laser emitted by the bias pump is repeatedly reflected and amplified in the resonant cavity mirror, and the output is a laser beam that meets the intensity requirements.

[0052] As a preferred embodiment, the reflectivity of the low-reflection grating is 8%.

[0053] As a preferred embodiment, the reflectivity of the high-reflection grating is not less than 95%.

[0054] The main working parameters of the laser of the utility model are: the optical fiber model is 25 / 400μm, it can output quasi-continuous laser with an average power of 80W and a peak power of 800W, the pulse width can be adjusted in the range of 40μs-100ms, and the repetition frequency range is 1Hz-3kHz.

[0055] The high-power quasi-continuous thulium-doped fiber laser with relaxation oscillation suppression provided in this embodiment adopts multi-wavelength hybrid pumping, and the pump source of the main output power selects multiple pulse pump sources, and then the laser emitted by the bias pump is used to make part of the thulium ions work at the second energy level or quasi-second energy level, which is beneficial to ensure that the laser upper energy level ( 3 F4) The particle number is in a controllable state, which can reduce the bias pump power while suppressing the laser relaxation oscillation, thereby reducing the power of the continuous base in the final output waveform.

[0056] The laser of the utility model solves the technical problem that the current bias pumping method commonly used in the current 1μm ytterbium-doped fiber laser cannot effectively suppress the relaxation oscillation in the 1.6-2μm thulium-doped fiber laser. The main reason for this problem is that the energy level of thulium ions is complex, and the number of upper energy level particles of 793nm pumping is uncontrollable, resulting in large fluctuations in the relaxation oscillation peak value and the need for a higher continuous base power. The laser provided in this embodiment can not only stably suppress relaxation oscillations, but also its bias continuous power base is reduced by three orders of magnitude compared to the conventional solution, effectively reducing the power consumption and the heat generation of the laser, and avoiding destructive effects on the processing environment and the acting material.

[0057] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present invention should be included in the protection scope of the present invention.

Claims

1. A high-power quasi-continuous-wave thulium-doped fiber laser with suppressed relaxation oscillation, characterized in that: It includes a multi-wavelength hybrid pump, a wavelength division multiplexer, a first fiber grating, a thulium-doped fiber, a second fiber grating and a cladding stripper connected in sequence; The multi-wavelength hybrid pump includes a bias pump source and a plurality of pulse pump sources; The output ends of the plurality of pulse pump sources are all connected to the input end of the wavelength division multiplexer; the bias pump source is connected to one end of a third fiber grating, the other end of the third fiber grating is connected to one end of an erbium-ytterbium co-doped fiber, the other end of the erbium-ytterbium co-doped fiber is connected to one end of a fourth fiber grating, and the other end of the fourth fiber grating is connected to the input end of the wavelength division multiplexer.

2. The high-power quasi-continuous-wave thulium-doped fiber laser with relaxation oscillation suppression according to claim 1, characterized in that: The pulse pump source and the bias pump source are both semiconductor lasers.

3. The high-power quasi-continuous-wave thulium-doped fiber laser with relaxation oscillation suppression according to claim 2, characterized in that: The laser emission wavelength of the bias pump source is 940 nanometers.

4. The high-power quasi-continuous-wave thulium-doped fiber laser with relaxation oscillation suppression according to claim 2, characterized in that: The laser emission wavelength of the pulse pump source is 793 nanometers.

5. The high-power quasi-continuous-wave thulium-doped fiber laser with relaxation oscillation suppression according to claim 2, characterized in that: The multi-wavelength hybrid pump further includes a bias current source, and the bias current source is connected to the bias pump source; When the bias pump source and the plurality of pulse pump sources are turned on, the bias current source outputs a bias current, so that the resonant cavity composed of the third fiber grating, the erbium-ytterbium co-doped fiber and the fourth fiber grating outputs continuous base laser.

6. The high-power quasi-continuous-wave thulium-doped fiber laser with relaxation oscillation suppression according to claim 5, characterized in that: The power of the continuous substrate laser is in the range of 1-5 mW.

7. The high-power quasi-continuous-wave thulium-doped fiber laser with relaxation oscillation suppression according to claim 1, characterized in that: The wavelength division multiplexer is a beam combiner.

8. The high-power quasi-continuous-wave thulium-doped fiber laser with relaxation oscillation suppression according to claim 1, characterized in that: The first fiber grating and the third fiber grating are high-reflection gratings; the second fiber grating and the fourth fiber grating are low-reflection gratings.

9. The high-power quasi-continuous-wave thulium-doped fiber laser with relaxation oscillation suppression according to claim 8, characterized in that: The reflectivity of the low-reflection grating is 8%.

10. The high-power quasi-continuous-wave thulium-doped fiber laser with relaxation oscillation suppression according to claim 8, characterized in that: The reflectivity of the high-reflection grating is not less than 95%.

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