Fiber mode-locked laser and laser device

Abstract

The present invention relates to the field of fiber laser technology, and in particular, to a fiber mode-locked laser and a laser device. The fiber mode-locked laser includes: a gain module, a phase shifter, a coupler, and a tunable filter; the gain module, the phase shifter, and the coupler form a NALM loop; the coupler is used to input a first reflection signal into the NALM sub-loop; the gain module and the phase shifter are respectively used to perform power amplification and phase shift processing on the first reflection signal transmitted clockwise and counterclockwise in the NALM sub-loop to obtain a second pulse signal and a third pulse signal; the coupler is further used to perform coupling processing on the second pulse signal and the third pulse signal to obtain a fourth pulse signal; in this way, through the action of the coupler and the phase shifter, the mode-locking threshold of the fiber mode-locked laser can be reduced to a certain extent, thereby effectively solving the technical problem of pulse splitting during mode-locking startup.

Description

Technical Field

[0001] The present invention relates to the technical field of fiber laser, and particularly relates to a fiber mode-locked laser and a laser device. Background Art

[0002] In 2008, Samuli et al. utilized the fiber SESAM mode-locking technology and combined it with an acousto-optic tunable filter to achieve a tunable all-fiber oscillator with a central wavelength of 1030 nm - 1060 nm. In 2016, K. Viskontas et al. utilized a SESAM mirror and a tunable filter to achieve a tunable all-fiber mode-locked light source with a central wavelength of 1020 nm - 1074 nm, a repetition frequency of 30 MHz, and an output power of 2 mW. In 2017, Feng Zou et al. utilized the SESAM mirror mode-locking method and combined it with a circulator and a tunable filter to achieve a tunable output of 1023 - 1060 nm, with an output power of 9.6 mW, a repetition frequency of 10.96 MHz, and a pulse width of 15.4 ps at a central wavelength of 1030 nm. In 2019, Maximilian Brinkmann et al. utilized a fiber SESAM and an electronically tunable filter to achieve an all-fiber oscillator with an output power of 2 mW, a repetition frequency of 40.5 MHz, a pulse width of 7 ps, and a tunable central wavelength of 1020 nm - 1060 nm, and used it as the seed source for a fiber FOPO (fiber optical parametric oscillator) system. In 2021, Thomas Wurthwein et al. based on a fiber SESAM and an electronically tunable filter achieved a mode-locked fiber oscillator with a repetition frequency of 40.5 MHz and a pulse width of 7 ps. In 2021 Aporta et al. based on SESAM mode-locking and collaborated with a tunable filter to achieve a tunable ps (picosecond) pulse laser output of 1025 - 1055 nm.

[0003] Currently, the following technical defects mainly exist in realizing fiber mode-locked laser signals in the prior art:

[0004] First, fiber oscillators with a tunable wavelength of 1 μm in the prior art are usually based on SESAM mode-locking. This mode-locking method usually has poor stability due to problems such as melting point aging and damage threshold.

[0005] Second, currently, for NALM fiber mode-locked lasers based on all polarization-maintaining with a repetition frequency below 50 MHz, there is usually a problem of pulse splitting during self-starting mode-locking, and it is necessary to reduce the pump power after mode-locking to achieve single-pulse mode-locking.

[0006] Thirdly, in the lasers implementing the mode-locking technology in the prior art, the commonly used filter is an electrically tunable filter, which is a mechanical drive structure. As the cavity, drive, homing, tuning rod, temperature, etc. change, the correspondence between the number of pulses and the frequency deteriorates. Therefore, the working performance of the existing lasers is not stable enough, and the generated mode-locking pulse signals are prone to errors. Moreover, when the existing electrically tunable filter is used for wavelength adjustment, the efficiency is low, and it often takes several minutes. In addition, the existing lasers based on electrically tunable filters cannot achieve adjustable wavelengths as needed, and the applicable range is small. Summary of the Invention

[0007] The present invention provides a fiber mode-locking laser and a laser device to solve the technical problem of pulse splitting during mode-locking startup in the prior art.

[0008] In a first aspect, the present invention provides a fiber mode-locking laser, which includes: a gain module, a phase shifter, a coupler, a tunable filter, and a first coupled output module;

[0009] The gain module, the phase shifter, and the coupler form a NALM loop; among them, the gain module and the phase shifter form a NALM sub-loop; the first end of the coupler is connected to the NALM sub-loop, and the second end of the coupler is connected to the first end of the tunable filter;

[0010] The tunable filter, in cooperation with the first coupled output module, is used to receive a first reflection signal and send it to the coupler; the coupler is used to output the first reflection signal into the NALM sub-loop; the gain module and the phase shifter are respectively used to perform power amplification and phase shift processing on the first reflection signals transmitted clockwise and counterclockwise in the NALM sub-loop to obtain a second pulse signal and a third pulse signal;

[0011] The coupler is further used to receive the second pulse signal and the third pulse signal through the first end, and perform coupling processing on the second pulse signal and the third pulse signal to obtain a fourth pulse signal; the tunable filter is further used to receive the fourth pulse signal output from the second end of the coupler, and perform continuous wavelength adjustment processing on the fourth pulse signal to obtain a first target laser signal.

[0012] According to the fiber mode-locking laser provided by the present invention, it further includes an optical circulator and an amplifier;

[0013] The second end of the coupler is further connected to the input end of the optical circulator, and the amplifier is connected to the first output end of the optical circulator;

[0014] The circulator is configured to receive the fifth pulse signal output by the coupler and output it to the amplifier; the amplifier is further configured to perform a two-pass non-linear amplification process on the fifth pulse signal to obtain a second target laser signal; the second output end of the circulator is configured to output the second target laser signal.

[0015] According to a fiber mode-locked laser provided by the present invention, a first end of the first coupling output module is connected to a second end of the tunable filter;

[0016] The first coupling output module is configured to receive the first target laser signal output from the tunable filter, and reflect the first target laser signal to obtain the first reflection signal; the first coupling output module is further configured to refract the first target laser signal to obtain a first transmission signal and output the first transmission signal.

[0017] According to a fiber mode-locked laser provided by the present invention, the first target laser signal is a picosecond-level pulsed laser signal; the second target laser signal is a femtosecond-level pulsed laser signal.

[0018] According to a fiber mode-locked laser provided by the present invention, it further includes a second coupling output module;

[0019] A first end of the gain module is connected to a first end of the phase shifter, and a second end of the gain module is connected to a second end of the phase shifter; a first end of the coupler is connected to a loop between the first end of the gain module and the first end of the phase shifter;

[0020] The second coupling output module includes a first port, a second port and a third port; the second coupling output module is connected to the NALM sub-loop, the first port of the second coupling output module is connected to the second end of the gain module, and the second port of the second coupling output module is connected to the second end of the phase shifter;

[0021] The second coupling output module is configured to receive the first reflection signal enhanced by the gain module and transmitted counterclockwise in the NALM sub-loop, perform a beam splitting process on the enhanced first reflection signal to obtain a third target laser signal and a fourth target laser signal; the third port of the second coupling output module is configured to output the third target laser signal, and the second port of the second coupling output module is configured to output the fourth target laser signal to the phase shifter.

[0022] According to a fiber mode-locked laser provided by the present invention, it further includes a semiconductor saturable absorber mirror; an input end of the semiconductor saturable absorber mirror is connected to a second end of the tunable filter;

[0023] The semiconductor saturable absorber mirror is used to receive the first target laser signal output from the tunable filter, perform pulse compression on it, and reflect the first target laser signal to obtain the first reflected signal.

[0024] According to a fiber mode-locked laser provided by the present invention, the gain module includes a pump source and a gain fiber;

[0025] The pump source is used to generate a pump optical signal, and the gain fiber is used to absorb the pump optical signal to amplify the power of the input signal.

[0026] According to a fiber mode-locked laser provided by the present invention, the splitting ratio of the coupler is 80:20, and the phase difference of the phase shifter is π / 2.

[0027] According to a fiber mode-locked laser provided by the present invention, the central wavelength of the tunable filter is 1030 nm and the bandwidth is 2 nm.

[0028] In a second aspect, the present invention also provides a laser device, which includes the fiber mode-locked laser as described above.

[0029] The fiber mode-locked laser provided by the present invention includes: a gain module, a phase shifter, a coupler, and a tunable filter; the gain module and the phase shifter form a NALM sub-loop; the first end of the coupler is connected to the NALM sub-loop to form a NALM loop structure, and the second end of the coupler is connected to the first end of the tunable filter. The tunable filter is used to receive the first reflected signal and send it to the coupler; the coupler is used to output the first reflected signal into the NALM sub-loop; the gain module and the phase shifter are respectively used to perform power amplification and phase shift processing on the first reflected signal transmitted clockwise and counterclockwise in the NALM sub-loop to obtain a second pulse signal and a third pulse signal; the coupler is also used to perform coupling processing on the second pulse signal and the third pulse signal to obtain a fourth pulse signal; thus, through the action of the coupler and the phase shifter, the mode-locking threshold of the fiber mode-locked laser is greatly reduced, effectively solving the technical problem of pulse splitting during mode-locking startup.

[0030] In addition, the tunable filter of the present application is also used to perform wavelength continuous adjustment processing on the fourth pulse signal to obtain the first target laser signal. In this way, the wavelength of the output fourth pulse signal can be adjusted within a certain range according to the needs of the application scenario, meeting the requirements of most application scenarios. Description of the Drawings

[0031] To more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is one of the schematic structural diagrams of the fiber mode-locked laser provided by the present invention;

[0033] Figure 2 It is another schematic structural diagram of the fiber mode-locked laser provided by the present invention;

[0034] Figure 3 It is the third schematic structural diagram of the fiber mode-locked laser provided by the present invention;

[0035] Figure 4 It is the spectrogram of the pulse signal output by the fiber mode-locked laser provided by the present invention.

[0036] Reference numerals:

[0037] 1: gain module; 2: phase shifter; 3: coupler; 4: circulator; 5: amplifier; 6: tunable filter; 7: first coupled output module; 8: second coupled output module; 9: semiconductor saturable absorber mirror. Detailed implementation manners

[0038] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention in conjunction with the drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0039] The present invention designs a fiber mode-locked laser based on the all-normal dispersion mode-locking technology. Based on the gain module, phase shifter, and coupler, a NALM sub-loop (i.e., a non-linear fiber amplification loop) is formed, which reduces the power threshold for the laser to reach the mode-locking point, enables the laser to have better self-starting performance, and low pulse energy will not cause pulse splitting, realizing a mode-locked laser with single-pulse start. And the mode-locked laser of the present invention introduces a tunable filter, realizing that the wavelength of the output pulse signal is adjustable within a certain range, meeting the requirements of most application scenarios. At the same time, compared with the existing lasers based on electro-tunable filters, the entire mode-locked laser has higher accuracy of the output pulse signal and more stable performance.

[0040] It should be noted that the connections involved in the present invention can be understood, in certain technical features, as including both physical connections and communication connections. For example, the connections between communication interfaces or between input and output terminals achieve both physical connections and the transmission of communication signals.

[0041] The following will further describe Figures 1 to 4 the technical solution of the present invention.

[0042] Embodiment 1:

[0043] As Figure 1 shown, this embodiment provides a fiber mode-locked laser, which includes: a gain module 1, a phase shifter 2, a coupler 3, a tunable filter 6, and a first coupled output module 7.

[0044] Among them, the gain module 1, the phase shifter 2, and the coupler 3 together form a NALM loop; among them, both ends of the gain module 1 are respectively connected to both ends of the phase shifter 2 to form a NALM sub-loop; the first end of the coupler 3 is connected to the NALM sub-loop, and the second end of the coupler 3 is connected to the first end of the tunable filter 6.

[0045] When the laser of the present invention operates, the first coupling output module 7 is used to receive the first reflection signal and send it to the coupler 3; the coupler 3 is used to output the first reflection signal into the NALM sub-loop. The coupler 3 has a certain power splitting ratio. After the first reflection signal enters the coupler 3, it will be split into two signals in the clockwise and counterclockwise directions according to the power splitting ratio. After the two signals with different powers propagate along the loop, a certain nonlinear phase difference will be generated. The first reflection signal is transmitted in the NALM sub-loop in the clockwise and counterclockwise directions respectively, that is, it passes through the gain module 1 and the phase shifter 2 successively. The counterclockwise signal will be amplified first after passing through the gain, and the clockwise signal will be amplified after passing through the gain. The two signals will accumulate different nonlinear phases during this process. The gain module 1 in the NALM sub-loop is used to amplify the power of the first reflection signal transmitted in the NALM sub-loop in the clockwise and counterclockwise directions, and at the same time increase the nonlinear phase difference in the NALM sub-loop. The phase shifter 2 is used to introduce a linear phase bias to the first reflection signal transmitted in the NALM sub-loop in the clockwise and counterclockwise directions to obtain the second pulse signal and the third pulse signal; the coupler is also used to receive the second pulse signal and the third pulse signal through the first end, and perform coupling processing on the second pulse signal and the third pulse signal to obtain the fourth pulse signal and the fifth pulse signal; the tunable filter 6 is also used to perform wavelength continuous adjustment processing on the fourth pulse signal to obtain the first target laser signal. The mode-locked laser of this embodiment is based on the gain module 1, the phase shifter 2, and the coupler 3 to form a NALM sub-loop, which reduces the power threshold for the laser to reach the mode-locked point, enables the laser to have better self-starting performance, and the low pulse energy will not cause pulse splitting, realizing a mode-locked laser with single-pulse start. And the mode-locked laser of this embodiment introduces a tunable filter 6, realizing that the wavelength of the output pulse signal is adjustable within a certain range, meeting the requirements of most application scenarios.

[0046] It can be understood that the function of the NALM loop in this embodiment is to introduce a gain competition trend similar to the saturable absorption effect. As a saturable absorber, it realizes the compression of pulses. The linear phase shift introduced by the phase shifter 2 makes it easier to achieve mode locking of pulses at a lower power, effectively improving the problem of pulse splitting during mode-locking startup.

[0047] The tunable filter 6 of this embodiment is a spectroscope made according to the acousto-optic diffraction principle. The transducer converts the high-frequency RF drive electrical signal into ultrasonic vibrations in the crystal, generating a spatially periodic modulation grating. When the incident light irradiates this grating, Bragg diffraction occurs, and the wavelength of the diffracted light corresponds one-to-one with the frequency of the high-frequency drive electrical signal. This tunable filter 6 can be used with a variety of laser light sources and can select and transmit light of a single wavelength from the incident light source. This acousto-optic tunable filter is a stable and reliable wavelength tuning method and has the advantages of continuous tunability, rapidity, accuracy, extinction ratio, etc. By using this acousto-optic tunable filter for regulation, a pulsed signal output with continuous tunability in the wavelength range of 1020 - 1060 nm is achieved.

[0048] Embodiment 2:

[0049] As Figure 2 , in one embodiment, the fiber mode-locked laser further includes a circulator 4 and an amplifier 5; the second end of the coupler 3 is also connected to the input end of the circulator 4, and the amplifier 5 is connected to the first output end of the circulator 4. The circulator is used to receive the fifth pulsed signal output by the coupler 3 and output it to the amplifier; the amplifier is further used to perform non-linear amplification processing on the fifth pulsed signal to obtain a second target laser signal; the second output end of the circulator is used to output the second target laser signal.

[0050] In one embodiment, the fiber mode-locked laser further includes a first coupled output module 7; the first end of the first coupled output module 7 is connected to the second end of the tunable filter 6. The first coupled output module 7 is used to receive the first target laser signal output from the tunable filter 6 and reflect the first target laser signal to obtain a first reflected signal. The first transmitted signal re-enters the NALM sub-loop for saturable absorption and amplification processing and finally is output from the coupler 3 to the tunable filter 6. The first coupled output module 7 is further used to transmit the first target laser signal to obtain a first transmitted signal and output this first transmitted signal. Generally, the first reflected signal accounts for about ninety percent of the first target laser signal and re-enters the NALM sub-loop for saturable absorption and amplification processing. The first transmitted signal accounts for about ten percent of the first target laser signal, and the first refracted signal is directly output. The energy loss generated during this process will be compensated by amplification in the gain module 1. The linear arm composed of the tunable filter 6 and the first coupled output module 7 realizes the self-similar evolution process of the pulse.

[0051] The gain module 1 in this embodiment includes a pump source and a gain fiber. The pump source is used to generate a pump optical signal, and the gain fiber is used to absorb the pump optical signal to amplify the power of the input signal. The gain fiber in this embodiment uses a ytterbium-doped gain fiber with a length of 48.8 cm and a polarization-maintaining single-mode fiber with a length of 324.6 cm. At the same time, when the laser is just started, an initial continuous non-mode-locked signal is generated through the gain module 1, and then it passes through the coupler 3 and the tunable filter 6 in sequence, and finally is reflected by the first coupling output module 7, and the signal returns to the NALM sub-loop for saturable absorption and amplification processing. After several cycles like this, the output pulse signal that meets the preset conditions is the first target laser signal. For example, the first target laser signal is a pulse signal with a continuously tunable wavelength range of 1020 - 1060 nm and picosecond level.

[0052] The coupler 3 in this embodiment is a 2×2 fiber coupler with a splitting ratio of 80:20, and the phase difference of the phase shifter 2 is π / 2. The center wavelength of the tunable filter 6 is 1030 nm and the bandwidth is 2 nm. Finally, a mode-locked laser signal with a repetition frequency of 30 MHz, a center wavelength of 1032 nm, and a spectral bandwidth of 1.4 nm is realized for the output first target laser signal, and the output power is 0.094 mW. For example, the spectrogram of the obtained first target laser signal is as Figure 4 shown.

[0053] The first transmitted signal output through the tunable filter 6 and the first coupling output module 7 in this embodiment is a pulse signal with a narrow spectrum and a pulse width in the ps magnitude. The tunable filter 6 uses the acousto-optic effect to achieve continuous tunability of the pulse wavelength. The first coupling output module 7 is a fiber mirror with 10% transmission and 90% reflection. Ninety percent of the energy of the fourth pulse signal is reflected back into the cavity by the fiber mirror after passing through the tunable filter 6, and 10% of the energy is transmitted and output through the fiber mirror. The amplifier 5 is composed of a gain module and a fiber total reflector. The pulse is amplified once after passing through the gain module, and then returns through the reflector and enters the gain module again for the second amplification. The second target laser signal output from the second output end of the circulator after being amplified and reflected by the amplifier 5 is a femtosecond-level pulsed laser signal. In other words, at the second end of the coupler 3, a non-linear amplification structure is introduced to directly obtain an amplified output with a pulse width in the fs magnitude, thus realizing a dual-output all-polarization-maintaining fiber mode-locked laser with two pulse widths of picosecond and femtosecond.

[0054] The tunable filter 6 in this embodiment uses an adjustable acousto-optic filter. Utilizing the acousto-optic effect, it modulates the radio frequency signal drive to realize the change of the output wavelength, and realizes continuous tunability of the wavelength in the range of 1020 - 1060 nm. Compared with the existing electronically tunable filter, the acousto-optic filter makes the entire structure of the laser more stable and greatly improves the service life.

[0055] Embodiment 3:

[0056] This embodiment provides a fiber mode-locked laser, which includes: a gain module 1, a phase shifter 2, a coupler 3, and a tunable filter 6. Both ends of the gain module 1 are respectively connected to both ends of the phase shifter 2 to form a NALM sub-loop; the first end of the coupler 3 is connected to the NALM sub-loop, and the second end of the coupler 3 is connected to the first end of the tunable filter 6. The fiber mode-locked laser further includes an optical circulator 4 and an amplifier 5; the second end of the coupler 3 is also connected to the input end of the optical circulator 4, and the amplifier 5 is connected to the first output end of the optical circulator 4. The optical circulator is used to receive the fourth pulse signal output by the coupler 3 and output it to the amplifier; the amplifier is further used to perform non-linear amplification processing on the fourth pulse signal to obtain a second target laser signal; the second output end of the optical circulator is used to output the second target laser signal.

[0057] As Figure 3 , in this embodiment, the fiber mode-locked laser further includes a second coupled output module 8, and the second coupled output module 8 is a 2×1 fiber coupler. When a signal is input from the first port, it will be output from the two output ports of the second port according to a certain splitting ratio. Here, a 10:90 fiber coupler is used, with 10% for outputting the first target laser signal and 90% for intracavity circulation; the first end of the gain module 1 (i.e., the right end in Figure 3 ) is connected to the first end of the phase shifter 2 (i.e., the right end in Figure 3 ), and the second end of the gain module 1 is connected to the second end of the phase shifter 2; the first end of the coupler 3 is connected to the loop between the first end of the gain module 1 and the first end of the phase shifter 2; the second coupled output module 8 includes a first port, a second port, and a third port; the second coupled output module 8 is connected to the NALM sub-loop. Specifically, the first port of the second coupled output module 8 is connected to the second end of the gain module 1, and the second port of the second coupled output module 8 is connected to the second end of the phase shifter 2. The second coupled output module 8 is used to receive the first reflected signal enhanced by the gain module 1 and transmitted counterclockwise in the NALM sub-loop, perform beam splitting processing on the enhanced first reflected signal to obtain a third target laser signal and a fourth target laser signal; the third target laser signal accounts for about 10%, and the fourth target laser signal accounts for about 90%. The third port of the second coupled output module 8 is used to output the third target laser signal, and the second port of the second coupled output module 8 is used to output the fourth target laser signal to the phase shifter 2 for the next cycle. The third port of the second coupled output module 8 in this embodiment is used to output the third target laser signal similar to the above-mentioned first target laser signal, which is a pulse signal with a continuously tunable wavelength range of 1020 - 1060 nm and a picosecond level.

[0058] In this embodiment, the mode-locked laser further includes a semiconductor saturable absorber mirror 9 (abbreviated as SESAM); the input end of the semiconductor saturable absorber mirror 9 is connected to the second end of the tunable filter; the semiconductor saturable absorber mirror 9 is configured to receive the first target laser signal output from the tunable filter, perform saturable absorption processing and reflection on the first target laser signal to obtain a first reflected signal, and enter the NALM sub-loop for nonlinear amplification processing. The NALM in this embodiment mainly consists of a coupler 3, a gain module 1, and a phase shifter 2. The coupler 3 is used to introduce the nonlinear phase shift of the clockwise and counterclockwise signals in the NALM sub-loop. The gain module 1 is used for signal amplification, and the phase shifter 2 is used to introduce a linear phase shift in the loop. The phase shifter 2 utilizes the nonlinear effect to obtain the effect of saturable absorption and realizes the compression of pulses during the oscillation process. The tunable filter 6 is used to perform continuous tunability processing on the pulse wavelength compressed by the NALM module to obtain an output with a narrow spectrum and a pulse width in the ps order of magnitude. The amplifier 5 is used to nonlinearly amplify the signal output from the transmission port to obtain an output signal with a relatively wide amplified spectrum and a pulse width in the fs order of magnitude.

[0059] Embodiment 4:

[0060] This embodiment provides a laser device, which includes the fiber mode-locked laser provided in any one of the above embodiments.

[0061] Specifically, since the laser device includes the fiber mode-locked laser as described above, and the specific structure of the fiber mode-locked laser refers to the above embodiments, the laser device shown in this embodiment includes all the technical solutions of the above embodiments. Therefore, it has at least all the beneficial effects obtained by the above all technical solutions, which will not be elaborated here one by one.

[0062] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative labor.

[0063] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the essence of the above technical solution, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fiber mode-locked laser, characterized in that, Including: A gain module, a phase shifter, a coupler, a tunable filter, and a first coupled output module; The gain module, the phase shifter, and the coupler form a NALM loop; wherein, the gain module and the phase shifter form a NALM sub-loop; the first end of the coupler is connected to the NALM sub-loop, and the second end of the coupler is connected to the first end of the tunable filter; The tunable filter, in cooperation with the first coupled output module, is configured to receive a first reflected signal and send it to the coupler; the coupler is configured to output the first reflected signal into the NALM sub-loop; the gain module and the phase shifter are respectively configured to perform power amplification and phase shift processing on the first reflected signal transmitted clockwise and counterclockwise in the NALM sub-loop to obtain a second pulse signal and a third pulse signal; The coupler is further configured to receive the second pulse signal and the third pulse signal through the first end of the coupler and perform coupling processing on the second pulse signal and the third pulse signal to obtain a fourth pulse signal; the tunable filter is further configured to receive the fourth pulse signal output from the second end of the coupler and perform wavelength continuous adjustment processing on the fourth pulse signal to obtain a first target laser signal; The fiber mode-locked laser further includes an optical circulator and an amplifier; The second end of the coupler is further connected to the input end of the optical circulator, and the amplifier is connected to the first output end of the optical circulator; The optical circulator is configured to receive the fifth pulse signal output by the coupler and output it to the amplifier; the amplifier is further configured to perform non-linear amplification processing on the fifth pulse signal to obtain a second target laser signal; the second output end of the optical circulator is configured to output the second target laser signal.

2. The mode-locked fiber laser according to claim 1, characterized in that The first end of the first coupled output module is connected to the second end of the tunable filter; The first coupled output module is configured to receive the first target laser signal output from the tunable filter, reflect the first target laser signal to obtain the first reflected signal; the first coupled output module is further configured to transmit the first target laser signal to obtain a first transmitted signal and output the first transmitted signal.

3. The mode-locked fiber laser according to claim 1, characterized in that, The first target laser signal is a picosecond-level pulsed laser signal; the second target laser signal is a femtosecond-level pulsed laser signal.

4. The mode-locked fiber laser according to claim 1, characterized in that, It further includes a second coupled output module; The first end of the gain module is connected to the first end of the phase shifter, and the second end of the gain module is connected to the second end of the phase shifter; the first end of the coupler is connected to the loop between the first end of the gain module and the first end of the phase shifter; The second coupled output module includes a first port, a second port, and a third port; the second coupled output module is connected to the NALM sub-loop, the first port of the second coupled output module is connected to the second end of the gain module, and the second port of the second coupled output module is connected to the second end of the phase shifter; The second coupling output module is configured to receive the first reflected signal enhanced by the gain module and transmitted counterclockwise in the NALM sub-loop of the NALM sub-loop, split the enhanced first reflected signal to obtain a third target laser signal and a fourth target laser signal; the third port of the second coupling output module is used to output the third target laser signal, and the second port of the second coupling output module is used to output the fourth target laser signal to the phase shifter.

5. The mode-locked fiber laser according to claim 4, characterized in that, It further includes a semiconductor saturable absorber mirror; the input end of the semiconductor saturable absorber mirror is connected to the second end of the tunable filter; The semiconductor saturable absorber mirror is configured to perform pulse compression processing on the first target laser signal received from the tunable filter and reflect the first target laser signal to obtain the first reflected signal.

6. The mode-locked fiber laser according to claim 1, wherein The gain module includes a pump source and a gain fiber; The pump source is configured to generate a pump optical signal, and the gain fiber is configured to absorb the pump optical signal to amplify the power of the input signal.

7. The mode-locked fiber laser according to claim 1, characterized in that, The splitting ratio of the coupler is 80:20, and the phase difference of the phase shifter is π / 2.

8. The mode-locked fiber laser according to claim 1, characterized in that, The central wavelength of the tunable filter is 1030 nm and the bandwidth is 2 nm.

9. A laser device, characterized in that, It includes a fiber mode-locked laser as described in any one of claims 1-8.

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