Output parameter-switchable amplified loop mirror pulse oscillator and oscillation output method

Abstract

The present invention discloses an amplified loop mirror pulse oscillator with switchable output parameters, which includes a Sagnac interferometer loop, a central coupler, a first linear reflection arm and a second linear reflection arm. Among them, the Sagnac interferometer loop and the central coupler, together with the first linear reflection arm and / or the second linear reflection arm, form a nonlinear amplified loop mirror pulse oscillator, which stably outputs ultrashort pulses in the picosecond or even femtosecond range. In the present invention, the Sagnac interferometer loop, the central coupler, and any one of the linear reflection arms can form a nonlinear amplified loop mirror pulse oscillator with a "9"-shaped cavity, which stably outputs ultrashort pulses in the picosecond range. The switching of the output parameters relies on the switching and adjustment of the mode-locked states of two lasers between the two linear reflection arms, and can achieve mode-locked pulses with different central wavelengths, pulse widths, repetition frequencies, and dual wavelengths.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and particularly to an amplified loop mirror pulse oscillator with switchable output parameters and an oscillation output method. Background Art

[0002] Ultra-short pulse fiber lasers are playing an increasingly important role in fields such as fine processing, laser medicine, scientific research, and national defense, and are becoming the key instrument for promoting the preparation of new materials and new devices. In the realization of high-power ultra-short pulse fiber lasers, the pulse oscillator is the core component. Different output parameters of the oscillator will directly affect the differences in the final output parameters of the laser, and thus cause differences in its application fields and application effects.

[0003] The parameters affecting the application fields and application effects of the laser are mainly the output pulse width, repetition frequency, and output wavelength of the laser. For high-power ultra-short pulse lasers with fixed indicators, limited by the single output parameters of the oscillator, their application fields and application effects are usually relatively limited. For example, a high-power fiber femtosecond laser with a pulse width of 20 ps has significant effects in the stealth cutting of sapphire wafers (LEDs). However, in the stealth cutting of other materials (such as SiC wafers), a 20-ps laser is powerless. Increasing or decreasing the output pulse width of the laser can make it competent for the stealth cutting of SiC wafers, but it will cause it to be unable to be competent for the stealth cutting of LEDs.

[0004] Therefore, researching an ultra-short pulse fiber oscillator with switchable output parameters can greatly improve the application compatibility of fiber lasers, enabling them to be competent for laser processing and manufacturing of different materials. There have been relevant studies at home and abroad that can obtain fiber pulse oscillators with different output parameters, but the changes in the output parameters of the lasers are small and difficult to meet the needs of different applications. For example, in 2012, Bai Yangbo et al. from Tianjin University (Tunable dual-wavelength passively mode-locked Yb-doped fiber laser using SESAM) realized a dual-wavelength ytterbium-doped fiber laser with tunable output wavelength using a semiconductor saturable absorber mirror. The tuning range of the output center wavelength of this laser is 1020-1055 nm, and the repetition frequency difference is only 20 kHz. The experiment did not give the pulse width comparison of the two mode-locked pulses, but the spectral widths of the two are not much different, and it is speculated that the corresponding transform-limited pulse widths are also very small, and the output parameter changes are extremely small. Summary of the Invention

[0005] The object of the present invention is to provide an amplified loop mirror pulse oscillator with switchable output parameters and an oscillation output method. The present invention uses a nonlinear amplified loop mirror to achieve switchable output parameters.

[0006] To achieve this purpose, the amplified loop mirror pulse oscillator with switchable output parameters designed by the present invention is characterized in that it includes a Sagnac interference loop, a central coupler, a first linear reflection arm and a second linear reflection arm. Among them, the Sagnac interference loop and the central coupler form a non-linear amplified loop mirror pulse oscillator with the first linear reflection arm and / or the second linear reflection arm, and stably output ultra-short pulses in the picosecond or even femtosecond order.

[0007] Advantages of the present invention:

[0008] In the present invention, the Sagnac interference loop, the central coupler and any one of the linear reflection arms can form a non-linear amplified loop mirror pulse oscillator in the "9" cavity type, and stably output ultra-short pulses in the picosecond order. The switching of the output parameters depends on the switching and adjustment of the mode-locking states of two lasers between the two linear reflection arms, and can realize mode-locked pulses with different central wavelengths, pulse widths, repetition frequencies and dual wavelengths. Description of the drawings

[0009] Figure 1 is a schematic diagram of the principle of the present invention;

[0010] Figure 2 is a schematic diagram of the first fiber amplifier in the present invention;

[0011] Figure 3 is a schematic diagram of the second fiber amplifier in the present invention;

[0012] Figure 4 is a schematic diagram of the third fiber amplifier in the present invention;

[0013] Among them, 1110 - the first fiber amplifier, 1120 - the beam splitter, 1130 - the phase shifter, 1140 - the central coupler, 1150 - the second fiber amplifier, 1160 - the first filter reflector, 1170 - the third fiber amplifier, 1180 - the second filter reflector, 1111 - the first pump source, 1112 - the first wavelength division multiplexer, 1113 - the first gain fiber, 1151 - the second pump source, 1152 - the second wavelength division multiplexer, 1153 - the second gain fiber, 1171 - the third pump source, 1172 - the third wavelength division multiplexer, 1173 - the third gain fiber. Detailed implementation manners

[0014] The following further describes the present invention in detail with reference to the drawings and specific embodiments:

[0015] The amplified loop mirror pulse oscillator with switchable output parameters designed by the present invention, such as Figures 1 to 4As shown in the figure, it includes a Sagnac interference loop, a central coupler 1140, a first linear reflection arm, and a second linear reflection arm. Among them, the Sagnac interference loop and the central coupler 1140 form a non-linear amplified loop mirror pulse oscillator with the first linear reflection arm and / or the second linear reflection arm, stably outputting ultrashort pulses in the picosecond or even femtosecond order of magnitude.

[0016] In the above technical solution, the Sagnac interference loop includes a first fiber amplifier 1110, a beam splitter 1120, and a phase shifter 1130. The first fiber amplifier 1110 includes a first pump source 1111, a first wavelength division multiplexer 1112, and a first gain fiber 1113. The signal output end of the first pump source 1111 is connected to the first communication end on the left side of the first wavelength division multiplexer 1112. The second communication end on the left side of the first wavelength division multiplexer 1112 is connected to the first communication end of the beam splitter 1120. The communication end on the right side of the first wavelength division multiplexer 1112 is connected to one end of the first gain fiber 1113. The other end of the first gain fiber 1113 is connected to the first communication end on the left side of the central coupler 1140. The second communication end of the beam splitter 1120 is the oscillator mode-locked pulse output end. The third communication end of the beam splitter 1120 is connected to the first communication end of the phase shifter 1130. The second communication end of the phase shifter 1130 is connected to the second communication end on the left side of the central coupler 1140.

[0017] In the above technical solution, the first linear reflection arm includes a second fiber amplifier 1150 and a first filter reflector 1160. The second fiber amplifier 1150 includes a second pump source 1151, a second wavelength division multiplexer 1152, and a second gain fiber 1153. The signal output end of the second pump source 1151 is connected to the first communication end on the left side of the second wavelength division multiplexer 1152. The second communication end on the left side of the second wavelength division multiplexer 1152 is connected to the first communication end on the right side of the central coupler 1140. The communication end on the right side of the second wavelength division multiplexer 1152 is connected to one end of the second gain fiber 1153. The other end of the second gain fiber 1153 is connected to the communication end of the first filter reflector 1160.

[0018] In the above technical solution, the second linear reflection arm includes a third fiber amplifier 1170 and a second filter reflector 1180. The third fiber amplifier 1170 includes a third pump source 1171, a third wavelength division multiplexer 1172, and a third gain fiber 1173. The signal output end of the third pump source 1171 is connected to the first communication end on the left side of the third wavelength division multiplexer 1172. The second communication end on the left side of the third wavelength division multiplexer 1172 is connected to the second communication end on the right side of the central coupler 1140. The communication end on the right side of the third wavelength division multiplexer 1172 is connected to one end of the third gain fiber 1173. The other end of the third gain fiber 1173 is connected to the communication end of the second filter reflector 1180.

[0019] In the above technical solution, the pump source provides pump energy for the amplifier. The wavelength division multiplexer is used to efficiently couple the pump laser output by the pump source and the signal light into the gain fiber after beam combination.

[0020] In the above technical solution, the doping ion types of the first gain fiber 1113, the second gain fiber 1153, and the third gain fiber 1173 include erbium, ytterbium, thulium, holmium, and neodymium ions. After being excited by the pump light, the gain fiber can radiate spontaneous emission laser.

[0021] In the above technical solution, fiber optic amplifiers are inserted into both the Sagnac interference loop and the two linear reflection arms to adjust the gain effect of this path. The gain effect depends on the pump light intensity. The stronger the pump light, the more obvious the gain effect.

[0022] In the above technical solution, the first filtering reflector 1160 is a first fiber Bragg grating. One end of the first fiber Bragg grating is connected to the other end of the second gain fiber 1153, and the other end of the first fiber Bragg grating is left open;

[0023] Alternatively, the first filtering reflector 1160 is composed of a first filter and a first mirror. Among them, the other end of the second gain fiber 1153 is connected to the first mirror through the first filter.

[0024] The second filtering reflector 1180 is a second fiber Bragg grating. One end of the second fiber Bragg grating is connected to the other end of the third gain fiber 1173, and the other end of the second fiber Bragg grating is left open;

[0025] Alternatively, the second filtering reflector 1180 is composed of a second filter and a second mirror. Among them, the other end of the third gain fiber 1173 is connected to the second mirror through the second filter.

[0026] The first filtering reflector 1160 and the second filtering reflector 1180 have different parameters.

[0027] The parameters of the filtering reflector include: reflection efficiency, filtering center wavelength, and filtering bandwidth. Different filtering reflector parameters will affect the oscillator output parameters. The above parameters correspond to the gain, output center wavelength, spectral width, and pulse width of the oscillator respectively.

[0028] In the above technical solution, the beam splitter 1120 is a 1×2 fiber coupler with a beam splitting ratio of 10:90. The beam splitting ratio between the second communication end and the third communication end of the beam splitter 1120 is 10:90.

[0029] In the above technical solution, the central coupler 1140 is a 2×2 fiber coupler with a 50:50 beam splitting ratio.

[0030] In the above technical solution, the 1130 phase shifter is a non-reciprocal device, which can provide a fixed phase difference for the signal light in the forward and reverse directions in the Sagnac interference loop, and helps to realize the self-starting mode locking of the nonlinear amplifying loop mirror mode-locked oscillator.

[0031] In the above technical solution, the first filtering reflector 1160 takes a fiber laser operating in the 1μm band as an example. Suppose it is a fiber Bragg grating with a central wavelength of 1070nm, a reflection bandwidth of 0.05nm, and a reflectivity > 99%. The central wavelength of the output pulse of the mode-locked pulse oscillator is 1070nm, and the pulse width is 70ps.

[0032] The second filtering reflector 1180 takes a fiber laser operating in the 1μm band as an example. Suppose it is a fiber Bragg grating with a central wavelength of 1030nm, a reflection bandwidth of 1nm, and a reflectivity > 60%. The central wavelength of the output pulse of the mode-locked pulse oscillator is 1030nm, and the pulse width is 10ps. The filtering reflector includes but is not limited to devices operating in the 1μm band, nor is it limited to the form of a fiber Bragg grating, or the form of a filter plus a fiber mirror, etc., all components or structures that can achieve the functions of filtering and reflection.

[0033] In the above technical solution, by adjusting the gain, loss, polarization and other effects of the two linear reflection arms, the competitive advantage of this path in the oscillator can be changed, so as to realize the switching of the output parameters of the laser.

[0034] The switching of output parameters means that the output parameters of the entire pulse oscillator are determined by the parameters of the filtering reflectors in the two linear arms. For example, if one path has an obvious competitive advantage (that is, higher gain or lower loss), the oscillator outputs the output parameters determined by the filtering reflector of this path; if the other path has an obvious competitive advantage, the oscillator outputs the output parameters determined by the filtering reflector of the other path; if the competitive advantages of the two paths are equal, the output parameters of the oscillator include the common characteristics of the two linear arms, which is a typical dual-wavelength, dual-pulse laser oscillator.

[0035] In the present invention, the difference in the repetition frequencies of the two output pulses can be achieved by adding a single-mode fiber in any one of the linear reflection arms.

[0036] For the above-mentioned output parameter switching, the following operations can be adopted: Turn on the pump sources in the first fiber amplifier 1110 and the second fiber amplifier 1150 and increase them to a certain power threshold. After the spontaneous emission laser in the gain medium is excited, a stable mode-locked pulse can be formed in the resonant cavity formed by the laser sagnac interference ring and the first linear reflection arm. Thus, a mode-locked pulse output dominated by the first linear reflection arm can be obtained respectively, with a central wavelength of 1070 nm and a pulse width of 70 ps. Then, turn off the second fiber amplifier 1150, turn on the third fiber amplifier 1170, and increase it to a certain power threshold, and a mode-locked pulse output dominated by the second linear reflection arm can be obtained, with a central wavelength of 1030 nm and a pulse width of 10 ps. Thus, the switching of output parameters is realized.

[0037] In addition, the present invention can also realize a mode-locked pulse oscillator with dual-wavelength output based on a nonlinear amplifying loop mirror. Compared with the above situation, this laser is realized by the following operations: Change the parameters of the first filter reflector 1160. Set it as a fiber Bragg grating with a central wavelength of 1070 nm, a reflection bandwidth of 1 nm, and a reflectivity > 99%. The central wavelength of the output pulse of the mode-locked pulse oscillator is 1070 nm, and the pulse width is 10 ps. Turn on the first fiber amplifier 1110, the second fiber amplifier 1150, and the third fiber amplifier 1170 and increase them to a certain power threshold. Use a spectrometer to observe the output pulse at the output end of the laser combiner 1120, and continuously optimize the pump powers of the second fiber amplifier 1150 and the third fiber amplifier 1170 until finally a stable dual-wavelength mode-locked pulse is output.

[0038] The specific implementation scheme of the present invention will be described below:

[0039] For a mode-locked pulse fiber laser, the realization of the mode-locked pulse is the result of the combined action of gain and loss in the resonant cavity. When the gain in the cavity is greater than the loss, the mode-locked pulse can be stably output. In the present invention, when any one of the linear reflection arms exists alone, the mode-locked pulse can be stably generated. Its output parameters are mainly determined by the parameters of the filter reflector. When the gain effect of one path is more obvious (i.e., the amplifier power is higher) and the competitive advantage is greater, the output parameters of the oscillator are determined by the linear reflection arm of this path. By reducing the gain of this path and increasing the gain of the other path, the working state of the oscillator can be switched to be dominated by the other path, thus realizing the switching of output parameters.

[0040] In addition, when the length difference between the two linear reflection arms is very small (the repetition frequencies of the output pulses of the two paths are extremely close), ensure that the gain effects of the two paths are at a comparable level. During the pulse evolution process, the action of the nonlinear effect (cross-phase modulation) can realize a pulse oscillator with dual-wavelength simultaneous output. This oscillator can be used as the seed source of a dual-comb spectrometer.

[0041] An oscillation output method using the above oscillator, which comprises the following steps:

[0042] Step 1: The first pump source 1111 outputs a pump laser signal, and the pump laser signal is transmitted to the first gain fiber 1113 through the first wavelength division multiplexer 1112. The first gain fiber 1113 radiates spontaneous emission laser according to the pump laser signal to form a signal light;

[0043] Step 2: The first gain fiber 1113 sends the signal light to the second wavelength division multiplexer 1152 through the central coupler 1140. The second pump source 1151 outputs a pump laser signal. The second wavelength division multiplexer 1152 combines the signal light and the pump laser signal, and then the second gain fiber 1153 amplifies the signal. The first filter reflector 1160 reflects the combined light after signal amplification and then returns it to the central coupler 1140;

[0044] Step 3: The central coupler 1140 recouples the reflected signal light into the sagnac interference loop. One path of the signal light is transmitted clockwise, that is, one path of the signal passes through the phase shifter 1130, the beam splitter 1120 and the first fiber amplifier 1110 in sequence. The other path of the signal light is transmitted counterclockwise, that is, the other path of the signal light passes through the first fiber amplifier 1110, the beam splitter 1120 and the phase shifter 1130 in sequence. When the two-way transmitted signal light passes through the first fiber amplifier 1110, it will be amplified by the first gain fiber 1113 and accumulate a certain phase. However, since the two paths of signal light pass through different sequences, the accumulated phases are also different, having a certain phase difference;

[0045] Step 4: The two-way transmitted and amplified signal light returns to the central coupler 1140 again and carries a certain phase difference. When the phase difference is 2π, the two beams of light interfere and enhance, and all return along the original path, and then return to the second fiber amplifier 1150 again, and then are reflected by the first filter reflector 1160 again. This cycle repeats until a stable mode-locked pulse is output from the second communication end of the beam splitter (1120), and the output pulse parameters of this path are determined by the first filter reflector.

[0046] For the linear path determined by the second linear reflection arm, its working principle is the same as that of the above steps 1 to 4. Only if the first fiber amplifier 1110 and the second fiber amplifier 1150 are turned on, the laser operates in the resonant cavity composed of the Sagnac interference ring, the second fiber amplifier 1150 and the first filter reflector 1160 to form a pulse output; and if the first fiber amplifier 1110 and the third fiber amplifier 1170 are turned on, the laser operates in the resonant cavity composed of the Sagnac interference ring, the third fiber amplifier 1170 and the second filter reflector 1180 to form a pulse output; if the first fiber amplifier 1110, the second fiber amplifier 1150 and the third fiber amplifier 1170 are turned on, and the second fiber amplifier 1150 and the third fiber amplifier 1170 have the same gain effect, the laser jointly transmits and operates in the resonant cavities respectively composed of the Sagnac interference ring and the first linear reflection arm, and the Sagnac interference ring and the second linear reflection arm to form a dual-wavelength dual-pulse laser output.

[0047] Embodiment 1, a nonlinear amplifying loop mirror mode-locked pulse oscillator with switchable output pulse parameters.

[0048] The present invention uses a nonlinear amplifying loop mirror mode-locking to achieve an ultrashort pulse fiber oscillator with switchable output parameters of output wavelength change (>40 nm), pulse width difference (>50 ps), and repetition frequency difference (in the order of MHz).

[0049] In Embodiment 1, the first fiber amplifier 1110 can amplify the power of the signal light by using the stimulated radiation effect of the laser. It includes a pump source, a wavelength division multiplexer, and a gain fiber.

[0050] The pump source provides pump energy for the oscillator. The central wavelength of the output pump laser is 974 nm, and the maximum output power is 600 mW.

[0051] The wavelength division multiplexer is used to efficiently couple the pump laser and the signal light into the gain fiber after beam combination. Its working band is 974 / 1030 nm.

[0052] In this embodiment, the gain fiber is a gain fiber with ytterbium ions doped in the core, and can radiate spontaneous emission laser of 1000 - 1100 nm after being excited by the 974 nm pump light.

[0053] The first filter reflector 1160 is a fiber Bragg grating with a central wavelength of 1070 nm, a reflection bandwidth of 0.05 nm, and a reflectivity >99%. The central wavelength of the output pulse of the corresponding mode-locked pulse oscillator is 1070 nm, and the pulse width is 70 ps.

[0054] The second filtering reflector 1180 is a fiber Bragg grating with a central wavelength of 1030 nm, a reflection bandwidth of 1 nm, and a reflectivity > 60%. The central wavelength of the output pulse of the mode-locked pulse oscillator corresponds to 1030 nm, and the pulse width is 10 ps.

[0055] In this embodiment, the difference in the repetition frequencies of the two output pulses can be achieved by adding a single-mode fiber in any one of the linear reflection arms.

[0056] The specific implementation process of Embodiment 1 is as follows: Turn on the first fiber amplifier 1110 and the second fiber amplifier 1150 and increase them to a certain power threshold, and a mode-locked pulse output dominated by the first linear reflection arm can be obtained, with a central wavelength of 1070 nm and a pulse width of 70 ps. Then, turn off the second fiber amplifier 1150, turn on the third fiber amplifier 1170, and increase it to a certain power threshold, and a mode-locked pulse output dominated by the second linear reflection arm can be obtained, with a central wavelength of 1030 nm and a pulse width of 10 ps. Thus, the switching of the output parameters is realized.

[0057] Embodiment 2: A non-linear amplifying loop mirror mode-locked pulse oscillator with dual-wavelength output. Compared with Embodiment 1, only the parameters of the filtering reflector of the first linear reflection arm are changed in Embodiment 2, and the lengths of the two linear reflection arms are ensured to be the same (error < 2 cm). The reason why the repetition frequency difference of the two mode-locked pulses needs to be less than 200 Hz is that when they evolve in the Sagnac interference loop, the cross-phase modulation clamping effect can make the dual-wavelength output possible. If the pulse repetition frequencies differ too much, the pulse walk-off is serious, and it is difficult to form a stable dual-wavelength pulse output.

[0058] Compared with Embodiment 1, only the parameters of the first filtering reflector 1160 are changed in Embodiment 2. It is a fiber Bragg grating with a central wavelength of 1070 nm, a reflection bandwidth of 1 nm, and a reflectivity > 99%. The central wavelength of the output pulse of the corresponding mode-locked pulse oscillator is 1070 nm, and the pulse width is 10 ps.

[0059] The implementation process of Embodiment 2 is as follows: Turn on the first fiber amplifier 1110, the second fiber amplifier 1150, and the third fiber amplifier 1170 and increase them to a certain power threshold. Use a spectrometer to observe the output pulse at the output end of the combiner 1120, and continuously optimize the pump powers of the second fiber amplifier 1150 and the third fiber amplifier 1170 until a stable dual-wavelength mode-locked pulse is finally output.

[0060] The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

Claims

1. An amplified loop mirror pulse oscillator with switchable output parameters, characterized in that: It includes a Sagnac interference loop, a central coupler (1140), a first linear reflection arm and a second linear reflection arm. Among them, the Sagnac interference loop and the central coupler (1140) form a non-linear amplified loop mirror pulse oscillator with the first linear reflection arm and / or the second linear reflection arm; the Sagnac interference loop includes a first fiber amplifier (1110), a beam splitter (1120) and a phase shifter (1130). The first fiber amplifier (1110) includes a first pump source (1111), a first wavelength division multiplexer (1112) and a first gain fiber (1113). The signal output end of the first pump source (1111) is connected to the first communication end on the left side of the first wavelength division multiplexer (1112). The second communication end on the left side of the first wavelength division multiplexer (1112) is connected to the first communication end of the beam splitter (1120). The communication end on the right side of the first wavelength division multiplexer (1112) is connected to one end of the first gain fiber (1113). The other end of the first gain fiber (1113) is connected to the first communication end on the left side of the central coupler (1140). The second communication end of the beam splitter (1120) is the output end of the oscillator mode-locked pulse. The third communication end of the beam splitter (1120) is connected to the first communication end of the phase shifter (1130). The second communication end of the phase shifter (1130) is connected to the second communication end on the left side of the central coupler (1140); the first linear reflection arm includes a second fiber amplifier (1150) and a first filter reflector (1160), and the second linear reflection arm includes a third fiber amplifier (1170) and a second filter reflector (1180); By adjusting the gain, loss and polarization of the two linear reflection arms, the competitive advantages of the two paths in the oscillator are changed, and the switching of the output parameters of the laser is realized; the output parameters of the pulse oscillator are determined by the parameters of the filter reflectors in the two linear arms. If one path has higher gain or lower loss, the oscillator outputs the output parameters determined by the filter reflector of this path; if the gains and losses of the two paths are equal, the output parameters of the oscillator include the common characteristics of the two linear arms.

2. The amplified loop mirror pulse oscillator with switchable output parameters according to claim 1, characterized in that: The second fiber amplifier (1150) includes a second pump source (1151), a second wavelength division multiplexer (1152) and a second gain fiber (1153). The signal output end of the second pump source (1151) is connected to the first communication end on the left side of the second wavelength division multiplexer (1152). The second communication end on the left side of the second wavelength division multiplexer (1152) is connected to the first communication end on the right side of the central coupler (1140). The communication end on the right side of the second wavelength division multiplexer (1152) is connected to one end of the second gain fiber (1153). The other end of the second gain fiber (1153) is connected to the communication end of the first filter reflector (1160).

3. The amplified ring mirror pulse oscillator with switchable output parameters according to claim 1 or 2, characterized in that: The third optical fiber amplifier (1170) includes a third pump source (1171), a third wavelength division multiplexer (1172), and a third gain fiber (1173). The signal output end of the third pump source (1171) is connected to the first communication end on the left side of the third wavelength division multiplexer (1172). The second communication end on the left side of the third wavelength division multiplexer (1172) is connected to the second communication end on the right side of the central coupler (1140). The communication end on the right side of the third wavelength division multiplexer (1172) is connected to one end of the third gain fiber (1173), and the other end of the third gain fiber (1173) is connected to the communication end of the second filtering reflector (1180).

4. The amplified ring mirror pulse oscillator with switchable output parameters according to claim 3, characterized in that: The doping ion types of the first gain fiber (1113), the second gain fiber (1153), and the third gain fiber (1173) include erbium, ytterbium, thulium, holmium, and neodymium ions.

5. The amplified ring mirror pulse oscillator with switchable output parameters according to claim 2, characterized in that: The first filtering reflector (1160) is a first fiber Bragg grating. One end of the first fiber Bragg grating is connected to the other end of the second gain fiber (1153), and the other end of the first fiber Bragg grating is left open. Alternatively, the first filtering reflector (1160) is composed of a first filter and a first mirror. Among them, the other end of the second gain fiber (1153) is connected to the first mirror through the first filter.

6. The amplified loop mirror pulse oscillator with switchable output parameters according to claim 3, characterized in that: The second filtering reflector (1180) is a second fiber Bragg grating. One end of the second fiber Bragg grating is connected to the other end of the third gain fiber (1173), and the other end of the second fiber Bragg grating is left open. Alternatively, the second filtering reflector (1180) is composed of a second filter and a second mirror. Among them, the other end of the third gain fiber (1173) is connected to the second mirror through the second filter.

7. The amplified loop mirror pulse oscillator with switchable output parameters according to claim 1, characterized in that: The beam splitter (1120) is a 1×2 fiber coupler with a splitting ratio of 10:

90.

8. The amplified ring mirror pulse oscillator with switchable output parameters according to claim 1, characterized in that: The central coupler (1140) is a 2×2 fiber coupler with a splitting ratio of 50:

50.

9. A method for oscillating output using the oscillator according to claim 3, characterized in that, It includes the following steps: Step 1: The first pump source (1111) outputs a pump laser signal. The pump laser signal is transmitted to the first gain fiber (1113) through the first wavelength division multiplexer (1112). The first gain fiber (1113) radiates spontaneous emission laser according to the pump laser signal to form a signal light. Step 2: The first gain fiber (1113) sends the signal light to the second wavelength division multiplexer (1152) through the central coupler (1140). The second pump source (1151) outputs a pump laser signal. The second wavelength division multiplexer (1152) combines the signal light and the pump laser signal, and then the combined light is amplified by the second gain fiber (1153). The first filtering reflector (1160) reflects the amplified combined light and then returns it to the central coupler (1140). Step 3: The central coupler (1140) recouples the reflected signal light back into the Sagnac interference loop. One path of the signal light is transmitted clockwise, that is, one path of the signal sequentially passes through the phase shifter (1130), the beam splitter (1120), and the first fiber amplifier (1110). The other path of the signal light is transmitted counterclockwise, that is, the other path of the signal light sequentially passes through the first fiber amplifier (1110), the beam splitter (1120), and the phase shifter (1130). The signal lights transmitted in both directions will be amplified by the first gain fiber (1113) and accumulate a certain phase when passing through the first fiber amplifier (1110). However, since the two paths of signal lights pass through in different orders, the accumulated phases are also different, having a certain phase difference. Step 4: The signal lights amplified by the two-way transmission return to the central coupler (1140) again and carry a certain phase difference. When the phase difference is 2π, the two beams of light interfere constructively and all return along the original path, returning to the second fiber amplifier (1150) again, and then being reflected by the first filter reflector (1160) again. This cycle repeats until a stable mode-locked pulse output is formed.

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