Fiber laser and method for suppressing relaxation oscillation thereof

Abstract

The application discloses a fiber laser and a method for suppressing relaxation oscillation of the fiber laser. The fiber laser comprises an oscillator and an amplifier connected in sequence. The oscillator comprises a first pump source, a high-reflection grating, a first gain fiber, a low-reflection grating and a first cladding light filter connected in sequence. The first pump source has a continuous operation state, and the first pump source is controlled to be in the continuous operation state before the fiber laser is started. The laser threshold power of the first pump source is P th , the operation power of the first pump source in the continuous operation state is P l , and P th >P l . By using the above fiber laser and the method for suppressing relaxation oscillation of the fiber laser, the pump source in the oscillator is controlled to continuously operate at a power lower than the laser threshold power before the fiber laser is started, the first gain fiber is in a weak-filling state, and population inversion exists. Therefore, the operation can eliminate the process of large amount of energy accumulation of inverted particles at the starting moment, so that the relaxation oscillation is effectively suppressed.

Description

Technical Field

[0001] This application belongs to the field of laser technology, specifically relating to a fiber laser and a method for suppressing relaxation oscillations therein. Background Technology

[0002] High-power quasi-continuous thulium-doped fiber lasers utilize thulium-doped gain fiber as the gain medium to generate laser light with a wavelength of 2µm under stimulation. By modulating the pump source, quasi-continuous pulse laser output can be achieved.

[0003] At the moment of laser startup, before a stable oscillation is established within the cavity, part of the gain fiber can act as a "saturable absorber," absorbing and storing energy until a certain "saturation" critical point, at which point the energy is released instantaneously, forming a huge spike pulse that interferes with system performance. Therefore, a method to suppress relaxation oscillations is urgently needed. Summary of the Invention

[0004] The technical problem to be solved by this application is that existing thulium-doped lasers are prone to relaxation oscillations at startup, which affect system performance. In order to solve this technical problem, a fiber laser that can effectively suppress relaxation oscillations and a relaxation oscillation suppression method thereof are provided.

[0005] The technical solution proposed in this application is as follows: A method for suppressing relaxation oscillations in a fiber laser involves controlling the pump source in the oscillator to be in a continuous operating state before the fiber laser is started. The laser threshold power of the pump source is P th The operating power of the pump source in continuous operation is P. l And P th >P l .

[0006] Furthermore, when the pump source is in continuous operation, the gain fiber generates population inversion.

[0007] Furthermore, P th and P l It also satisfies: 0.8 P th <P l .

[0008] A fiber laser, comprising: The oscillator includes a first pump source, a high-reflectivity grating, a first gain fiber, a low-reflectivity grating, and a first cladding optical filter connected in sequence. An amplifier is located downstream of the oscillator and connected to the first cladding optical filter; Wherein, the laser threshold power of the first pump source is P thThe first pump source has a continuous operating state, and the operating power of the first pump source in the continuous operating state is P. l And P th >P l .

[0009] Furthermore, the oscillator also includes a first beam combiner, the oscillator includes a plurality of first pump sources, the plurality of first pump sources are connected to the first beam combiner, and the first beam combiner is connected to the high-reflectivity grating.

[0010] Furthermore, at least one of the first pump sources has the continuous operating state.

[0011] Furthermore, the amplifier includes an isolator, a second combiner, a second gain fiber, and a second cladding optical filter connected in sequence. The oscillator is connected to the isolator. The amplifier also includes a second pump source, which is connected to the second combiner.

[0012] Furthermore, the amplifier comprises multiple stages, which are connected sequentially. Each stage of the amplifier includes the isolator, the second combiner, the second gain fiber, the second cladding optical filter, and the second pump source.

[0013] Furthermore, it also includes a mode field adapter, which is disposed between two adjacent stages of the amplifier.

[0014] Furthermore, the oscillator also includes a first driving module, which is connected to the first pump source and is used to enable the first pump source to be in the continuous operation state.

[0015] Using the aforementioned fiber laser and its relaxation oscillation suppression method, before the fiber laser is started, the pump source in the oscillator is controlled to operate continuously at a power lower than the laser threshold power. The first gain fiber is in a weakly filled state, exhibiting population inversion. Therefore, at the moment of startup, this operation can eliminate the process of large-scale energy accumulation of inverted particles, thereby effectively suppressing relaxation oscillations. Attached Figure Description

[0016] The accompanying drawings are provided to further understand this application and form part of the specification. They are used together with the embodiments of this application to explain this application and do not constitute a limitation thereof.

[0017] Figure 1 This is a schematic diagram of the structure of a fiber laser provided in one embodiment of this application; Figure 2 The diagram shows pulses of a conventional fiber laser and the fiber laser provided in this application.

[0018] Label Explanation: 100 Oscillator; 110 First pump source; 120 High-reflection grating; 130 First gain fiber; 140 Low-reflection grating; 150 First cladding optical filter; 160 First combiner; 200 Amplifier; 210 Isolator; 220 Second combiner; 230 Second gain fiber; 240 Second cladding optical filter; 250 Second pump source; 300 Mode field adapter; 400 Output head. Detailed Implementation

[0019] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0021] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0022] To suppress relaxation oscillations in fiber lasers, this application provides a fiber laser and a method for suppressing relaxation oscillations therein.

[0023] like Figure 1As shown, in one embodiment, the fiber laser includes an oscillator 100 and an amplifier 200 connected in sequence. The oscillator 100 includes a first pump source 110, a high-reflectivity grating 120, a first gain fiber 130, a low-reflectivity grating 140, and a first cladding optical filter 150 connected in sequence. The amplifier 200 is located downstream of the oscillator 100 and connected to the first cladding optical filter 150. The first pump source 110 provides pump light; the high-reflectivity grating 120 and the low-reflectivity grating 140 form a resonant cavity for generating oscillations and selecting the signal wavelength; the first gain fiber 130 absorbs the pump light to generate population inversion and amplify the signal light; and the first cladding optical filter 150 filters out the pump light from the fiber.

[0024] Furthermore, the laser threshold power of the first pump source 110 is P. th The first pump source 110 has a continuous operating state, and the operating power of the first pump source 110 in the continuous operating state is P. l And P th >P l Furthermore, when the first pump source 110 is in continuous operation, the first gain fiber 130 will experience population inversion. Preferably, P th and P l It also meets the requirement of: 0.8P th <P l To ensure in P l At power, the first gain fiber 130 is in a weakly filled state and will not accumulate a large amount of energy.

[0025] It should be explained that the laser threshold power refers to the power at which the first pump source 110, when operating, enables the oscillator 100 to reach the laser emission threshold, thereby generating high-power laser output. When the first pump source 110 is in continuous operation, its operating power is less than the laser threshold power, meaning that the oscillator 100 will not generate high-power laser and will be in a low-power operating state. The first gain fiber 130 will be in a weakly filled state and will not accumulate a large amount of energy.

[0026] To suppress relaxation oscillations, the fiber laser in the above embodiment operates as follows: before starting the fiber laser, the first pump source 110 is controlled to operate continuously. Thus, when the first pump source 110 is in continuous operation, the first gain fiber 130 will experience population inversion, for example, localized population inversion, resulting in only low-power laser output within the cavity. Subsequently, at startup, the first pump source 110 operates at a power exceeding the laser threshold power. Since the first gain fiber 130 is already in a weakly filled state with population inversion, the accumulation of a large amount of energy from the inverted particles at startup can be eliminated, thereby suppressing relaxation oscillations. Furthermore, for the effects of the fiber laser and its relaxation oscillation suppression method in the above embodiment, please refer to [reference needed]. Figure 2 , Figure 2 (a) is a schematic diagram of a conventional fiber laser pulse. Figure 2 (b) is a schematic diagram of the pulse after using the fiber laser and its relaxation oscillation suppression method in the above embodiments. As can be seen from the figure, the fiber laser and its relaxation oscillation suppression method in the above embodiments can effectively suppress the generation of the spike pulse at the moment of startup, thereby achieving the suppression of relaxation oscillation.

[0027] Using the aforementioned fiber laser and its relaxation oscillation suppression method, before the fiber laser is started, the pump source in the oscillator 100 is controlled to operate continuously at a power lower than the laser threshold power, and the first gain fiber 130 is in a weakly filled state, resulting in population inversion. Therefore, at the moment of startup, this operation can eliminate the process of large-scale energy accumulation of inverted particles, thereby effectively suppressing relaxation oscillations.

[0028] In one embodiment, the oscillator 100 includes a plurality of first pump sources 110. The oscillator 100 also includes a first beam combiner 160. The plurality of first pump sources 110 are connected to the first beam combiner 160, which is capable of beam combining the pump light generated by the plurality of first pump sources 110. The first beam combiner 160 is connected to a high-reflectivity grating 120 to deliver the beam combined to the high-reflectivity grating 120.

[0029] Furthermore, at least one first pump source 110 has a continuous operating state. Therefore, in order to suppress relaxation oscillations, one of the first pump sources 110 can be controlled to be in a continuous operating state before the fiber laser is started, or multiple first pump sources 110 can be controlled to be in a continuous operating state.

[0030] In one embodiment, the oscillator 100 further includes a first driving module. The first driving module is connected to the first pump source 110 and is used to enable the first pump source 110 to operate continuously. Optionally, the first driving module is a high-precision constant current source to provide a stable, low-noise current to the first pump source 110, thereby ensuring that the first pump source 110 operates stably at low power.

[0031] It should be noted that the oscillator 100 also includes a second driving module. The second driving module can be a pulse drive or a constant current source drive, and it is used to drive the first pump source 110 to operate at a power exceeding the laser threshold power. Simultaneously, the fiber laser can be equipped with a master switch and a start switch. When the master switch is closed, all electronic components in the fiber laser are de-energized. When the master switch is open, the first driving module continuously drives the first pump source 110 to ensure that relaxation oscillations can be suppressed at any time. When the start switch is open, the second driving module drives the first pump source 110. Furthermore, the first driving module and the second driving module are preferably connected to different first pump sources 110.

[0032] In one embodiment, amplifier 200 includes an isolator 210, a second combiner 220, a second gain fiber 230, and a second cladding optical filter 240 connected in sequence. Oscillator 100 is connected to isolator 210, which prevents reflected light from returning to upstream oscillator 100. Amplifier 200 also includes a second pump source 250 connected to the second combiner 220.

[0033] It should be noted that the functions of the second pump source 250, the second combiner 220, the second gain fiber 230, and the second cladding optical filter 240 can all be referred to the functions of the first pump source 110, the first combiner 160, the first gain fiber 130, and the first cladding optical filter 150 in the above embodiments, and will not be repeated here. However, the second pump source 250 does not need to be set to a continuous operating state. Furthermore, there can be multiple second pump sources 250.

[0034] In one embodiment, amplifier 200 comprises multiple stages. The multiple stages of amplifier 200 are connected sequentially, and each stage of amplifier 200 includes the aforementioned isolator 210, second combiner 220, second gain fiber 230, second cladding optical filter 240, and second pump source 250. Therefore, in adjacent stages of amplifier 200, the second cladding optical filter 240 in the upstream amplifier 200 is connected to the isolator 210 in the downstream amplifier 200. In other embodiments, the isolator 210 may only be provided in the amplifier 200 connected to the oscillator 100; this is not a limitation.

[0035] In one embodiment, the fiber laser further includes a mode field adapter 300. The mode field adapter 300 is disposed between the oscillator 100 and the amplifier 200, or between two adjacent amplifier stages 200, to connect optical fibers with different mode field diameters to meet the output requirements of subsequent high-power lasers. It is understood that the connections between the aforementioned standard components are all via optical fibers. If the mode field diameters of the optical fibers in the oscillator 100 and amplifier 200 are different, or if the mode field diameters of the optical fibers in two adjacent amplifier stages 200 are different, a mode field adapter 300 is required for connection.

[0036] In one embodiment, the fiber laser further includes an output head 400. The output head 400 is connected downstream of the amplifier 200. Specifically, the output head 400 is connected to the output of the second cladding optical filter 240 in the downstream amplifier 200.

[0037] In summary, the fiber laser and its relaxation oscillation suppression method provided in this application have at least the following advantages: Before the fiber laser is started, the pump source in the oscillator 100 operates continuously at a power lower than the laser threshold power, and the gain fiber is in a weakly filled state, which can effectively avoid energy accumulation and suppress relaxation oscillation at the moment of startup.

[0038] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing relaxation oscillations in a fiber laser, characterized in that, Before the fiber laser is started, the pump source in the control oscillator is kept in continuous operation. The laser threshold power of the pump source is P th The operating power of the pump source in continuous operation is P. l And P th >P l .

2. The fiber laser relaxation oscillation suppression method according to claim 1, characterized in that, When the pump source is in continuous operation, the gain fiber generates population inversion.

3. The fiber laser relaxation oscillation suppression method according to claim 1, characterized in that, P th and P l It also satisfies: 0.8 P th <P l .

4. A fiber laser, characterized in that, include: The oscillator includes a first pump source, a high-reflectivity grating, a first gain fiber, a low-reflectivity grating, and a first cladding optical filter connected in sequence. An amplifier is located downstream of the oscillator and connected to the first cladding optical filter; Wherein, the laser threshold power of the first pump source is P th The first pump source has a continuous operating state, and the operating power of the first pump source in the continuous operating state is P. l And P th >P l .

5. The fiber laser according to claim 4, characterized in that, The oscillator further includes a first beam combiner, the oscillator includes a plurality of first pump sources, the plurality of first pump sources are connected to the first beam combiner, and the first beam combiner is connected to the high-reflectivity grating.

6. The fiber laser according to claim 5, characterized in that, At least one of the first pump sources has the continuous operating state.

7. The fiber laser according to claim 5, characterized in that, The amplifier includes an isolator, a second combiner, a second gain fiber, and a second cladding optical filter connected in sequence. The oscillator is connected to the isolator. The amplifier also includes a second pump source, which is connected to the second combiner.

8. The fiber laser according to claim 7, characterized in that, The amplifier comprises multiple stages, which are connected sequentially. Each stage of the amplifier includes the isolator, the second combiner, the second gain fiber, the second cladding optical filter, and the second pump source.

9. The fiber laser according to claim 8, characterized in that, It also includes a mode field adapter, which is disposed between two adjacent stages of the amplifier.

10. The fiber laser according to claim 5, characterized in that, The oscillator further includes a first driving module, which is connected to the first pump source and is used to enable the first pump source to be in the continuous operation state.

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