CN109149336B - Passive Q-switched mode-locked laser based on SBS and Fabry-Perot interferometer - Google Patents

Abstract

The invention discloses a passive Q-switched mode-locking laser based on SBS and Fabry-Perot interferometer, comprising: a pump source, a gain fiber, a fiber wavelength division multiplexer, a passive fiber, a fiber Bragg grating and a Fabry Perot interferometer, Fabry Perot interferometer is composed of two fiber end faces with a little spacing, which can be the end face of ordinary fiber jumper and the end face of ordinary fiber jumper through the fiber flange to accurately align and leave the spacing, also It can be composed of conventional fiber end faces and conventional fiber end faces that are precisely aligned and left spaced by other optical alignment tools. The pump source and gain fiber are determined according to the actual wavelength requirement. The central reflection wavelength of the fiber Bragg grating corresponds to the gain wavelength of the gain fiber. The two multiplexing wavelengths of the fiber wavelength division multiplexer are the pump wavelength and the gain wavelength of the gain fiber, respectively. The invention can restrain the amplitude, repetition frequency and spectral instability of the Brillouin passive Q-switched laser emission pulse.

Description

Passive Q-switched mode-locked laser based on SBS and Fabry-Perot interferometer

technical field

The invention belongs to the technical field of fiber lasers, and more particularly relates to a passively Q-switched mode-locked laser based on multi-level stimulated Brillouin scattering and Fabry-Perot interferometer.

Background technique

As one of the important nonlinear effects in optical fibers, stimulated Brillouin scattering has a small excitation threshold, and nonlinear backscattering has been widely used, such as fibers based on Brillouin backscattering Sensing and pulse width compression, slow light control based on SBS induced group refractive index changes, phase conjugation and beam quality optimization using SBS in multimode fibers, and using stimulated Brillouin scattering Passive Q-switching effect and modulation instability effect realized by Brillouin scattering. As one of the possible pulse generation methods to realize all-fiberization, passive Q-switching effect and relaxation oscillation effect of stimulated Brillouin scattering (SBS) have always been hot topics in ultrafast optics research. As early as 1997, researchers first realized self-starting Q-switching based on Brillouin scattering in a rare-earth ion-doped fiber laser. The two-end feedback used in the experiment was a fiber ring resonator and a mirror, as a typical example. For narrow linewidth feedback devices, the experimental scheme using fiber-optic ring resonators has been used until now. Subsequently, the researchers discovered the phenomenon of emitting mode-locked pulses based on the modulation instability effect of SBS. Since passive Q-switched and mode-locked lasers based on SBS can be built near any wavelength with gain, the threshold of SBS effect can be reduced with the increase of fiber length, and no additional optical components are required, so it is easy to build, so it has always been a laser important research content in the field.

However, due to the dynamic mechanism of SBS, the passive Q-switched laser of SBS has always been characterized by unstable output pulse. The instability of the output pulse based on passive Q-switching of SBS originates from the random thermal noise and random Rayleigh scattering in the laser. Thermal noise plays the role of initiating Brillouin scattering in the process of Brillouin scattering. The feedback effect brought by Rayleigh scattering constitutes the resonator of the Brillouin laser. The fiber ring resonators used in previous experiments usually have narrow linewidths, which are easy to excite stimulated Brillouin scattering, and have no feedback effect on multi-level Stokes light. played the most important role in the process. In fact, the passive Q-switching effect of Brillouin Q-switched lasers is caused by the combined action of nonlinear Brillouin backscattering and linear Rayleigh scattering, due to thermal noise and backscattering that cause spontaneous Brillouin scattering. Rayleigh scattering is random, causing the amplitude and repetition frequency of the Q-switched pulse to fluctuate in the range of 20% to 40%. Therefore, the instability and uncontrollability of passive Q-switching of SBS are caused. Although this characteristic can generate occasional pulses with extremely large peak power-to-average power ratios, it also has great defects.

First, the accidentally generated ultra-intensive pulses with uncontrollable amplitude can cause damage to the fiber and optical devices; secondly, the Q-switched pulse is usually accompanied by spurious pulses and has a multi-peak structure; finally, the amplitude and repetition frequency of the Q-switched output pulse Very unstable. Therefore, the application of passive Q-switching based on SBS is greatly limited. To attenuate the effects of thermal noise and other noises, some researchers suggest experimenting in a low temperature environment or other isolated systems. For example, the repetition rate of the pulse can be stabilized by adding an acousto-optic modulator in the cavity to actively modulate the pulse. It is also possible to control the gain by modulating the pump pulse to stabilize the repetition frequency of the Q-switched pulse, but this method is not very helpful for the amplitude stabilization, and in the above two methods, the stability of the spectrum is not mentioned. . Although all of these methods are effective, they all complicate the system, weaken the advantages of Brillouin passive Q-switched lasers in economy and convenience, and do not fundamentally solve the problem.

SUMMARY OF THE INVENTION

In view of the above defects or improvement needs of the prior art, the present invention provides an all-fiber passively Q-switched mode-locked laser based on multi-stage stimulated Brillouin scattering and Fabry-Perot interferometer, thereby solving the There are technical problems that the output of passive Q-switched laser based on stimulated Brillouin scattering is unstable, damages optical devices and is difficult to be practical.

In order to achieve the above object, the present invention provides a passively Q-switched mode-locked laser based on SBS and Fabry-Perot interferometer, including: a pump laser unit, a Fabry-Perot interferometer, a passive fiber and a fiber Bragg grating ;

The pump laser unit is respectively connected with the Fabry-Perot interferometer and the fiber Bragg grating;

The pump laser unit is used to realize the introduction of pump energy, and realize the amplification and conversion of the stimulated radiation of the pump energy into laser energy;

The fiber Bragg grating is used to realize the reflection of laser light, thereby forming a straight cavity resonator together with the Fabry-Perot interferometer;

The passive optical fiber is used to accumulate the Brillouin effect, which is placed at any position in the straight cavity resonator;

The Fabry-Perot interferometer is used to separately modulate the multi-level Stokes light generated by stimulated Brillouin scattering by using its nano-scale wavelength loss modulation to obtain stable Q-switched pulses or locks. mode pulse, and then output the Q-switched pulse or the mode-locked pulse from the end of the Fabry-Perot interferometer.

Preferably, the Fabry-Perot interferometer is composed of a first optical fiber end face and a second optical fiber end face, and the first optical fiber end face and the second optical fiber end face are aligned with a pre-existing fiber therebetween. Set the spacing.

Preferably, the first optical fiber end face is an ordinary optical fiber end face, and the second optical fiber end face is an ordinary optical fiber end face or an optical fiber end face after surface reflection enhancement treatment.

Preferably, the pump laser unit includes: a pump source, a fiber wavelength division multiplexer and a gain fiber;

The pump source is connected to the short wavelength end of the fiber wavelength division multiplexer, and the two long wavelength ends of the fiber wavelength division multiplexer are respectively connected to the first fiber end face and the gain fiber, so the gain fiber is connected to the fiber Bragg grating;

The pump source is used to implement the introduction of pump energy, the fiber wavelength division multiplexer is used to couple the pump energy into the straight cavity resonator, and convert it into laser energy through the gain fiber, the Gain fibers are used to achieve population inversion.

Preferably, the preset distance between the first optical fiber end face and the second optical fiber end face is between 5 μm and 1000 μm.

Preferably, the 3dB reflection bandwidth of the fiber Bragg grating is between 0.5 nm and 10 nm.

Preferably, the rare earth ions doped in the gain fiber are one or more of ytterbium ions, erbium ions and thulium ions.

Preferably, the passive fiber is not doped with a gain medium.

In general, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) Conventional passive Q-switched lasers based on SBS rely on nonlinear Brillouin scattering to achieve Q-switching operation. Usually, a fiber ring resonator is used to enhance the optical resonance in the ring to cause stimulated Brillouin scattering. Due to the lack of specific feedback for multilevel Stokes light, spontaneous Brillouin scattering and stochastic distributed Rayleigh scattering caused by random thermal noise play an important role in the initiation of Q-switched pulses. Therefore, the emitted pulses are random, unstable, and difficult to use. In the present invention, an optical fiber end face 7 and an optical fiber end face 6 are butted, and a gap is left, thereby generating an intra-cavity Fabry-Perot interferometer, which can perform nanometer-level regulation on the loss of wavelength, After satisfying the basic conditions of SBS Q-switching, it can also have a feedback effect on the Stokes light of a specific order, so that different orders of Stokes play different roles in the process of Q-switching, especially for a specific order of Stokes light. The feedback of Stokes light makes this order Stokes light play the role of stable pulse. Therefore, the influence of thermal noise and random Rayleigh scattering on the output pulse is weakened, and the output of SBS-based Q-switched pulse and mode-locked pulse with very stable pulse amplitude, repetition frequency and spectrum is realized.

(2) Compared with the conventional passive Q-switched mode-locked laser, it has the advantages of operating at multiple wavelengths, high damage threshold, easy integration of all-fiber, low cost, high output power, few components, and a simple optical path. The advantages. At present, the conventional Q-switched laser generation methods mainly include passive Q-switching methods such as saturable absorber, nonlinear ring mirror, nonlinear polarization rotation, etc., as well as active Q-switching methods such as electro-optical Q-switching, acousto-optic Q-switching, and rotating mirror Q-switching. The Q-switching method can operate at multiple wavelengths, but the cost is high, and the system is complex and difficult to integrate. The Q-switching of the saturable absorber is due to the specific wavelength absorption of the saturable absorber, so that the saturable absorber can only work in a specific wavelength range, and the damage threshold of the general saturable absorber is much lower than the damage threshold of the fiber itself, which inhibits the emission of the fiber. Power potential, can only work as a seed photogenerator at low power. As for the nonlinear ring mirror, nonlinear polarization rotation and other methods, specific device support is required, and the cost is relatively high. However, the passive Q-switched mode-locked laser based on SBS of the present invention has the operating mechanism of nonlinear stimulated Brillouin scattering effect, so theoretically it can be generated in any medium and wavelength with Brillouin gain, and is not limited by wavelength . Secondly, based on the structure of the passively Q-switched mode-locked laser of the present invention, the cost is low, and only two fiber end faces, such as fiber jumper end faces, need to be connected. The operation is simple and easy to implement, further reducing the cost of pulse generation. Secondly, based on the structure of the present invention, all-fiber packaging can be easily realized, and it is easy to integrate with other systems, such as multi-stage amplification systems, sensing systems and the like. Furthermore, due to the simple structure of the present invention and fewer optical devices used, the stability and damage threshold of the entire system are greatly increased, and the system can operate under extremely high power. Finally, the laser structure of the present invention can realize the output of Q-switched and mode-locked pulses, and the output pulse width ranges from microseconds to nanoseconds, and has a wide range of practical applications.

(3) The fiber end face 6 of the present invention adopts a common fiber end face, because once the fiber end face 6 has a higher reflectivity, the fiber end face 6 and the fiber Bragg grating 5 will form a straight cavity resonant cavity, resulting in the loss of the optical fiber. If the oscillation continues, the number of inverted particles cannot be aggregated, and stimulated Brillouin scattering cannot form a pulse output even if excited. Secondly, the fiber end face 7 can be an ordinary fiber end face or a fiber end face that has undergone reflection enhancement treatment. If the reflection enhancement treatment is performed, the reflectivity of the fiber end face 7 after the reflection enhancement treatment should be between 5% and 40%, because it is too low. The reflectivity of the Fabry-Perot cavity is too low, so that the feedback of the Stokes light is weak and drowned in thermal noise and random Rayleigh scattering, unable to form oscillations, causing random output of Q-switched pulses. If the reflectivity is too high, the reflectivity of the Fabry-Perot cavity will be too high, so that the signal light can only accumulate the number of inverted particles within a very small distance between the end faces of the two fibers. When the vibration starts, the accumulation of inversion particle numbers cannot be formed, which makes it difficult for the laser to work in the state of pulse operation.

(4) The present invention realizes a stable and controllable output based on SBS passive Q-switching, promotes the research and wide application of SBS-based passive Q-switching lasers, and provides a feasible solution for all-fiber passive Q-switching mode locking. Cheap pulsed laser fabrication offers a viable idea.

Description of drawings

1 is a schematic structural diagram of a passively Q-switched mode-locked laser based on multi-stage stimulated Brillouin scattering and Fabry-Perot interferometer provided by an embodiment of the present invention;

Fig. 2 is a kind of structure that produces the Fabry-Perot interferometer provided by the embodiment of the present invention, adopts the structural schematic diagram of jumper alignment;

3 is a Q-switched pulse sequence emitted by a passively Q-switched mode-locked laser based on multi-stage stimulated Brillouin scattering and Fabry-Perot interferometer provided by an embodiment of the present invention under a pump light of 600 mW;

FIG. 4 is a graph of a Q-switched pulse sequence emitted by a passively Q-switched mode-locked laser based on multi-level stimulated Brillouin scattering and Fabry-Perot interferometer provided by an embodiment of the present invention under the pump light of 600 mW radio frequency map;

5 is a mode-locked pulse sequence emitted by a passively Q-switched mode-locked laser based on multi-stage stimulated Brillouin scattering and Fabry-Perot interferometer provided by an embodiment of the present invention;

6 is a radio frequency diagram of a mode-locked pulse sequence emitted by a passively Q-switched mode-locked laser based on a multi-stage stimulated Brillouin scattering and a Fabry-Perot interferometer provided by an embodiment of the present invention;

In all figures, the same reference numerals are used to refer to the same elements or structures, wherein: 1- pump source, 2- wavelength division multiplexer, 3- gain fiber, 4- passive fiber, 5- fiber Bragg Grating, 6-first fiber end face, 7-second fiber end face, 8-first fusion point, 9-second fusion point, 10-third fusion point, 11-fourth fusion point, 12-fifth fusion point , 13-fiber flange, 14-first fiber jumper end face, 15-second fiber jumper end face, 16-first fiber jumper, 17-second fiber jumper.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The terms "first", "second", "third", "fourth" and "fifth" in the description and claims of the present invention are used to distinguish different objects, rather than to describe a specific order .

The present invention proposes a passively Q-switched mode-locking laser based on SBS and Fabry-Perot interferometer to break through the existing passive Q-switching and mode-locking based on SBS, which cannot be practical due to its huge randomness and instability. Applied restrictions. The basic idea is that although the fiber ring resonator in the existing scheme can generate a very narrow linewidth, it amplifies the effect of noise, which leads to the instability of the Q-switching of the Brillouin laser. In the present invention, an optical fiber end face 7 and an optical fiber end face 6 are butted, and a gap is left, thereby producing an intra-cavity Fabry-Perot interferometer, which can measure the wavelength loss in nanometer order. It can also have a feedback effect on the Stokes light of a specific level after satisfying the basic conditions of SBS Q-switching, so the influence of thermal noise and random Rayleigh scattering on the output pulse is weakened, and the pulse amplitude, repetition frequency and The spectrally stable outputs of SBS-based Q-switched pulses and mode-locked pulses.

1 is a schematic structural diagram of an all-fiberized passively Q-switched mode-locked laser based on multi-stage stimulated Brillouin scattering and Fabry-Perot interferometer provided by an embodiment of the present invention, wherein the pump laser unit includes Pump source 1, fiber wavelength division multiplexer 2 and gain fiber 3; the laser also includes passive fiber 4, fiber Bragg grating 5, Fabry-Perot interference composed of a first fiber end face 6 and a second fiber end face 7 The instrument, as well as the first welding point 8, the second welding point 9, the third welding point 10, the fourth welding point 11, and the fifth welding point 12 produced by connecting the various parts.

The pump source 1 is connected to the short wavelength end of the optical fiber wavelength division multiplexer 2 through the first fusion splicing point 8, and the two long wavelength ends of the optical fiber wavelength division multiplexer 2 are respectively connected with the first end and the first end of the gain fiber 3. An optical fiber end face 6 is connected to the second fusion splicing point 9 through the third fusion point 10, the first optical fiber end face 6 and the second optical fiber end face 7 can be aligned by the optical fiber flange or other optical alignment tools and leave a gap to form a fabric Riperot interferometer, the second fiber end face 7 is used as the main output end, the second end of the gain fiber 3 is connected to the first end of the passive fiber 4 through the fourth fusion point 11, and the second end of the passive fiber 4 is connected to the fiber Bragg grating The first ends of 5 are connected by a fifth welding point 12 . The laser can work in a Q-switched state or in a mode-locked state, and can stably emit pulses in the nanosecond to microsecond range.

In the embodiment of the present invention, the passive fiber 4 is a conventional fiber without a gain medium, which may be located between the gain medium 3 and the fiber Bragg grating 5 , or may be located between the first fiber end face 6 and the fiber wavelength division multiplexer 2 It can also be located between the optical fiber wavelength division multiplexer 2 and the gain fiber 3. The passive optical fiber only plays the role of accumulating the Brillouin effect, and can be placed in any position.

In the embodiment of the present invention, the rare earth ions doped in the gain fiber 3 are one or more of ytterbium ions, erbium ions and thulium ions. Among them, when the rare earth ions are ytterbium ions, the wavelength emitted by the pump source is 915 nm or 976 nm, when the rare earth ions are erbium ions, the wavelength emitted by the pump source is 980 nm or 1480 nm, and when the rare earth ions are thulium ions, the wavelength emitted by the pump source is 793 nm or 980nm.

In the embodiment of the present invention, the 3 dB reflection bandwidth of the fiber Bragg grating 5 is between 0.5 nm and 10 nm.

In the embodiment of the present invention, the distance between the first fiber end face 6 and the second fiber end face 7 is between 5 μm and 1000 μm. The first fiber end face 6 is a common fiber end face, and the second fiber end face 7 can be a common fiber end face or a fiber end face that has undergone surface reflection enhancement treatment. After the second optical fiber end face 7 is subjected to surface reflection enhancement treatment, the 3dB bandwidth of its reflection enhancement is not less than 0.5 nm, and the reflectivity is between 5% and 40%.

The common fiber end face in the embodiment of the present invention refers to the end face obtained by cutting the fiber with a cleaver without any processing.

In the embodiment of the present invention, the pump source 1 may be a conventional fiber-coupled semiconductor laser or a solid-state laser. The laser is coupled out by the fiber, and the core diameter of the output fiber is consistent with the core diameter of the gain fiber 3, the passive fiber 4, the fiber Bragg grating 5, the fiber wavelength division multiplexer 2 and the fiber end face to achieve the minimum fusion loss. The laser is a single-wavelength laser, and its central emission wavelength is located in the absorption spectrum of the rare-earth ions doped by the gain fiber 3, and continuous pumping can generate inversion particle numbers.

The fiber wavelength division multiplexer 2, which is a conventional fiber wavelength division multiplexer, is used to couple the pump wavelength into the direct cavity resonator, connect the direct cavity resonator, and convert it into laser energy through the gain fiber 3 . The coupling wavelength at the short wavelength end is the pump wavelength, and the coupling wavelength at the two long wavelength ends is the emission wavelength of the gain fiber.

The gain fiber 3, which is a conventional rare earth ion-doped fiber, consists of a doped core, a silica cladding and a coating layer. The absorption wavelength of the doped rare earth ions corresponds to the pump wavelength, and the emission wavelength corresponds to the reflection wavelength of the fiber Bragg grating 5 .

Passive fiber 4, which can be a conventional silica fiber or a photonic crystal fiber. It consists of core, cladding and coating.

The fiber Bragg grating 5 may be a Bragg grating written by a femtosecond laser, or a Bragg grating produced by other technologies. Its central reflection wavelength corresponds to the gain wavelength of the gain fiber, that is, its central reflection wavelength is located at the peak of the emission spectrum of the gain fiber.

The second optical fiber end face 7 and the first optical fiber end face 6 can be single-mode optical fibers or multi-mode optical fibers of the same specification, or both can be optical fiber jumpers, and the core sizes of the two optical fiber jumpers are the same. After the second fiber end face 7 and the first fiber end face 6 form a Fabry-Perot interferometer, different feedbacks can be generated for the Stokes light generated by the cascade.

The specific embodiment corresponding to the structural schematic diagram of the present invention is given below:

For the passively Q-switched mode-locked fiber laser based on SBS and Fabry-Perot interferometer shown in Figure 1, the pump source 1 is a 980 nm semiconductor laser. The wavelength division multiplexer 2 is a 1×2 three-port fiber optic coupler, the corresponding wavelength of port 1 is 980 nm, the corresponding wavelength of port 2 and port 3 is 1550 nm, and the bandwidth of the three ports is ±10 nm. The gain fiber 3 is an erbium-doped fiber with a length of 9 meters, and the passive fiber 4 is a standard single-mode fiber with a length of 20 meters. The center wavelength of the fiber Bragg grating 5 is 1550 nm, and the 3dB bandwidth is 4.9 nm. Both the first fiber end face 6 and the second fiber end face 7 are standard single-mode jumpers.

FIG. 2 shows one of the structures for generating a Fabry-Perot interferometer, which is formed in the form of an optical fiber flange butted with an optical fiber patch cord. The second optical fiber patch cord end face 15 of the second optical fiber patch cord 17 and the first The first optical fiber jumper end face 14 of the optical fiber jumper 16 is aligned by the optical fiber flange 13, and the distance between the two jumper end faces is about 17.4 μm, forming a Fabry-Performer that has a modulation effect on the wavelength in the nm order. Luo cavity. The Fabry-Perot cavity has weak feedback to the first several orders of Stokes light generated by the cascade of lasers, and has relatively significant feedback to the latter several orders of Stokes light generated in sequence.

FIG. 3 shows the emission of a passively Q-switched mode-locked laser based on multi-stage stimulated Brillouin scattering and Fabry-Perot interferometer provided by an embodiment of the present invention under a pump light of 600 mW The Q-switched pulse sequence.

FIG. 4 shows the emission of a passively Q-switched mode-locked laser based on multi-stage stimulated Brillouin scattering and Fabry-Perot interferometer provided by an embodiment of the present invention under a pump light of 600 mW RF diagram of the Q-switched pulse sequence.

FIG. 5 shows an all-fiberized passively Q-switched mode-locked laser based on multi-stage stimulated Brillouin scattering and Fabry-Perot interferometer provided by an embodiment of the present invention while adjusting the Fabry-Perot interferometer. After the interval between the mode-locked pulse trains that are transmitted.

FIG. 6 shows an all-fiberized passively Q-switched mode-locked laser based on multi-stage stimulated Brillouin scattering and Fabry-Perot interferometer provided by an embodiment of the present invention while adjusting the Fabry-Perot interferometer. RF plot of the transmitted mode-locked pulse train after the spacing between.

After the combined effect of the wavelength modulation spectrum of the Fabry-Perot cavity, the gain spectrum of the gain fiber, the reflection spectrum of the fiber Bragg grating, and the linewidth narrowing of random Rayleigh scattering, only the narrow linewidth The laser energy initially oscillates in the cavity, and due to the small feedback of the Fabry-Perot cavity and the random Rayleigh distributed feedback, a large number of inverted particles is accumulated in the cavity, and the straight cavity resonator enters a low Q value. state, the narrow linewidth laser causes cascaded stimulated Brillouin scattering in the cavity, and emits cascaded Stokes light, and the first several orders of Stokes light do not pass through the Fabry-Perot cavity. The modulation is only due to the weak Rayleigh scattering distributed feedback in the cavity and the fiber Bragg grating to form a low-Q resonator. After several orders of Stokes light are excited, due to the significant feedback in the cavity, the resonator is not suitable for the latter order. For Stokes light, it is a high-Q resonator. The energy accumulated in the cavity before is emitted out of the resonator in a very short time, forming a stable Q-switched pulse. The output pulse amplitude and repetition frequency of conventional SBS-based passive Q-switched lasers generally fluctuate violently in the range of 20% to 40%, which severely limits the practical application of SBS-based passively Q-switched lasers. , under the pump power of 600mW, the output pulse repetition frequency instability is as low as 1.06%, and the amplitude instability is as low as 1.52%. As shown in Figure 4, the signal-to-noise ratio is as high as 68.12dB. The highest signal-to-noise ratio achieved by the Q-switched laser fully proves the stability of the laser. After slowly adjusting the spacing of the Fabry-Perot cavity formed by the end faces of the two jumpers, the laser emits a stable mode-locked pulse sequence, as shown in Figure 6, the repetition frequency is 3.6MHz, which corresponds to the time for the light to cycle through the cavity once. The signal-to-noise ratio is as high as 73.88dB, and the emission pulse width is on the order of nanoseconds, which proves the ability of the laser to generate stable narrow pulse width pulses.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims (7)

1. a passive Q-switched mode-locked laser based on SBS and Fabry-Perot interferometer, is characterized in that, comprises: pump laser unit, Fabry-Perot interferometer, passive fiber (4) and fiber Bragg grating (5); The pump laser unit is respectively connected with the Fabry-Perot interferometer and the fiber Bragg grating (5); The pump laser unit is used to realize the introduction of pump energy, and realize the amplification and conversion of the stimulated radiation of the pump energy into laser energy; The fiber Bragg grating (5) is used to realize the reflection of the laser light, thereby forming a straight cavity resonator together with the Fabry-Perot interferometer; The passive optical fiber (4) is used to accumulate the Brillouin effect, and is placed at any position in the straight cavity resonator; The Fabry-Perot interferometer is composed of a first optical fiber end face (6) and a second optical fiber end face (7), and the first optical fiber end face (6) is aligned with the second optical fiber end face (7). There is a preset distance between the two, which is used to separately modulate the multi-level Stokes light generated by stimulated Brillouin scattering by using its nano-scale wavelength loss modulation to obtain a stable Q-switched pulse. or mode-locking pulse, and then outputting the Q-switching pulse or the mode-locking pulse from the end of the Fabry-Perot interferometer. 2. The laser according to claim 1, wherein the first fiber end face (6) is a common fiber end face, and the second fiber end face (7) is a common fiber end face or a surface reflection enhancement treatment. Fiber end face. 3. The laser according to claim 1 or 2, wherein the pump laser unit comprises: a pump source (1), a fiber wavelength division multiplexer (2) and a gain fiber (3); The pump source (1) is connected to the short wavelength end of the optical fiber wavelength division multiplexer (2), and the two long wavelength ends of the optical fiber wavelength division multiplexer (2) are respectively connected to the first optical fiber The end face (6) is connected with the gain fiber (3), and the gain fiber (3) is connected with the fiber Bragg grating (5); The pump source (1) is used to implement the introduction of pump energy, and the fiber wavelength division multiplexer (2) is used to couple the pump energy into the straight cavity resonator, and pass the gain fiber (3) is converted into laser energy, and the gain fiber (3) is used to realize population inversion. 4. The laser according to claim 1, characterized in that, the preset distance between the first fiber end face (6) and the second fiber end face (7) is between 5 μm and 1000 μm. 5. The laser according to claim 1 or 2, characterized in that the 3 dB reflection bandwidth of the fiber Bragg grating (5) is between 0.5 nm and 10 nm. 6. The laser according to claim 3, wherein the rare earth ions doped in the gain fiber (3) are one or more of ytterbium ions, erbium ions and thulium ions. 7. The laser according to claim 1, characterized in that, the passive fiber (4) is not doped with a gain medium.

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