An ytterbium-doped fiber mode-locked laser

Abstract

The application discloses a ytterbium-doped fiber mode-locked laser, which comprises a first pump source, a first regenerator, a second pump source and a second regenerator. The first regenerator comprises a first ytterbium-doped fiber and a pulse stretching device, and the second regenerator comprises an isolator, a pulse compression device, a spectrum stretching fiber and a band-pass filter. The design of the staggered band-pass filter is realized through the two regenerators, and the spectrum is widened due to the self-phase modulation effect; in addition, the energy input of the first pump source and the second pump source can realize the mode-locked pulse output. The application reduces the peak power by pulse stretching to reduce the nonlinear effect, realizes the generation of high-energy output pulses in the fiber mode-locked laser, and the interval between the pulse stretching device and the central wavelength of the band-pass filter can effectively prevent the noise and continuous component from oscillating, and improve the pulse quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mode-locked lasers, in particular to a Yb-doped fiber mode-locked laser. BACKGROUND

[0002] As an important branch of modern laser technology, Yb-doped fiber mode-locked lasers integrate the latest achievements in material science, optical engineering, and electronic technology. Yb-doped fibers, with their unique gain characteristics such as wide absorption band, high quantum efficiency, and low pump threshold, have become the ideal gain medium for achieving high-power and high-efficiency laser output. Mode-locked technology, as a key technology for realizing ultra-short pulse output, precisely controls the phase relationship of each longitudinal mode in the laser cavity, resulting in a high degree of compression of laser pulses in time, thereby outputting laser with high peak power and narrow pulse width.

[0003] However, in the development of high-power Yb-doped fiber mode-locked lasers, the suppression of nonlinear effects has become a key problem that needs to be solved. Nonlinear effects, such as self-phase modulation, four-wave mixing, and optical soliton effect, can introduce additional phase changes and energy losses during laser transmission, leading to distortion of laser pulses, broadening of the spectrum, and a decrease in output power. Especially under conditions of high power density and long fiber length, these nonlinear effects are particularly significant, severely limiting the output performance of the laser. SUMMARY

[0004] Therefore, in order to solve one of the above problems, the present application provides a Yb-doped fiber mode-locked laser, which reduces the peak power by pulse broadening to alleviate nonlinear effects, and realizes the generation of high-energy output pulses in a fiber mode-locked laser.

[0005] The present application provides a Yb-doped fiber mode-locked laser, comprising a first pump source, a first regenerator, a second pump source, and a second regenerator; wherein,

[0006] The first regenerator and the second regenerator are connected end to end; the first pump source provides energy for the first regenerator; and the second pump source provides energy for the second regenerator.

[0007] The first regenerator comprises a first Yb-doped fiber and a pulse broadening device; the second regenerator comprises an isolator, a bandpass filter, a pulse compression device, and a spectral broadening fiber; the center wavelength of the pulse broadening device has a spacing from the center wavelength of the bandpass filter; and the passband of the pulse broadening device has a spacing from the passband of the bandpass filter.

[0008] The pulse broadening device comprises a first chirped Bragg grating; and the pulse compression device comprises a second chirped Bragg grating.

[0009] The first regenerator and the second regenerator are used for band-pass filtering and generating spectral broadening caused by self-phase modulation effect.

[0010] The application provides a ytterbium-doped fiber mode-locked laser, which comprises a first pump source, a first regenerator, a second pump source and a second regenerator. The first regenerator comprises a first ytterbium-doped fiber and a pulse broadening device, and the second regenerator comprises an isolator, a band-pass filter, a pulse compression device and a spectral broadening fiber. The pulse broadening device and the center wavelength of the band-pass filter have a spacing, and the band-passes are different. Therefore, the two regenerators can realize the design of staggered band-pass filters, have spectral broadening caused by self-phase modulation effect, and realize mode-locked pulse output by the energy input of the first pump source and the second pump source. The application reduces the peak power by pulse broadening to reduce the nonlinear effect, realizes high-energy output pulse in the fiber mode-locked laser, and effectively prevents noise and continuous component from oscillating by the spacing between the pulse broadening device and the center wavelength of the band-pass filter, thereby improving the pulse quality.

[0011] Further, the first regenerator further comprises a first fiber combiner and a fiber coupler.

[0012] The first fiber combiner, the first ytterbium-doped fiber, the fiber coupler and the pulse broadening device are sequentially connected.

[0013] In the application, the pulse broadening device makes the entering pulse normally dispersed and then enters the second ytterbium-doped fiber for amplification. The pulse broadening device has the function of band-pass filtering.

[0014] In the application, the spectral broadening fiber is used for nonlinear spectral broadening of the pulse compressed by the pulse compression device, so that part of the spectrum can pass through the band-pass filter. The amount of nonlinear spectral broadening is adjusted by the length of the spectral broadening.

[0015] In the application, when the laser works for the first time, the first pump source and the second pump source need to output pump light with a certain power to excite the gain medium in the ytterbium-doped fiber. The ytterbium-doped fiber has good heat dissipation performance, a wide absorption band and stable output, can efficiently couple into the fiber, thereby improving the pumping efficiency of the laser, effectively coupling the pump light into the fiber, and stably working the laser. The application also provides a seed laser, which is connected with the fiber coupler to form a seed starting device. After the laser works for the first time, the laser pump power and the filter band-pass frequency range are fixed, and the seed pulse injection can start the mode locking.

[0016] Further, the pulse stretching device further comprises a fiber circulator and a fiber collimator.

[0017] One end of the fiber circulator is connected to the fiber coupler, and the other end of the fiber circulator is connected to the second regenerator.

[0018] In the pulse stretching device, the pulse entering the pulse stretching device is stretched by the first chirped fiber Bragg grating to a preset standard through the fiber circulator from the fiber collimator to free space, reflected back to the fiber collimator, and finally enters the second fiber combiner and the second Yb-doped fiber connected to the fiber circulator from the fiber circulator.

[0019] Further, the pulse passing through the pulse stretching device has the following characteristics:

[0020] The pulse width is within 0.5-5ps;

[0021] The spectral width is between 5-20nm;

[0022] The pulse energy is greater than 100pJ.

[0023] Optionally, the pulse stretching device can achieve normal dispersion stretching of the entering pulse to the order of hundreds of picoseconds to nanoseconds, and the entering pulse is adjusted according to preset parameters, and the stretched pulse enters the second Yb-doped fiber for amplification. The preset parameters include center wavelength, bandwidth, and dispersion amount, etc.

[0024] Optionally, the fiber coupler comprises a 2×2 fiber coupler; and the splitting ratio of the fiber coupler comprises 50 / 50.

[0025] The type and performance parameters of the fiber coupler are configured according to the implementation requirements.

[0026] Further, the second regenerator further comprises a second combiner and a second Yb-doped fiber.

[0027] The second fiber combiner, the second Yb-doped fiber, the isolator, the pulse compression device, the spectral stretching fiber, and the bandpass filter are connected in sequence.

[0028] Specifically, the pulse compression device further comprises a wave plate, a first polarization beam splitting cube, a second polarization beam splitting cube, a second fiber collimator, and a third fiber collimator; one end of the second fiber collimator is connected to the second Yb-doped fiber; and one end of the third fiber collimator is connected to the spectral stretching fiber.

[0029] Optionally, in the pulse compression device, the wave plate comprises a first half-wave plate, a second half-wave plate, and a quarter-wave plate.

[0030] Specifically, the pulse of the second Yb-doped fiber passes through the second fiber collimator, the isolator, the first polarization beam splitting cube, the quarter wave plate, the second chirped volume Bragg grating, is reflected back to the first polarization beam splitting cube from the second chirped volume Bragg grating, then passes through the first half wave plate, the second polarization beam splitting cube, the second half wave plate, the third fiber collimator in sequence, and finally enters the spectrum broadening fiber.

[0031] Optionally, the pulse compression device is configured to output the compressed laser energy according to a preset ratio.

[0032] Specifically, the pulse compression device compresses the pulse amplified by the second Yb-doped fiber according to preset parameters, the preset parameters of the pulse compression device such as the central wavelength, bandwidth and dispersion amount of the pulse are consistent with those of the spectrum broadening device, abnormal dispersion is introduced, the compressed laser energy is output according to a preset ratio, and the remaining energy is returned to the spectrum broadening fiber. Further, the band-pass filter includes a band-pass filter with a bandwidth of nm order; the bandwidth of the band-pass filter is smaller than the bandwidth of the pulse broadening device and the bandwidth of the pulse compression device.

[0033] It should be noted that in one mode-locked laser implemented by the application, the first regenerator includes a first fiber combiner, a first Yb-doped fiber, a fiber coupler and a pulse broadening device, the second regenerator includes a second fiber combiner, a second Yb-doped fiber, a pulse compression device, a spectrum broadening fiber and a band-pass filter; the first regenerator and the second regenerator are connected to form a ring resonator, the central wavelength and the passband of the band-pass filter and the pulse broadening device are separated, the spectrum broadening caused by the misaligned band-pass filter setting and the self-phase modulation effect satisfies the Mamyshev mode-locking mechanism, and finally the first pump source and the second pump source provide energy for the resonator to realize mode-locked pulse output.

[0034] The Mamyshev mechanism refers to a passive mode-locking technology used in a mode-locked laser. The mode-locking technology locks multiple longitudinal mode light waves together so that they overlap in time and interfere to form ultrashort pulses. The Mamyshev mechanism is characterized by spectrum broadening caused by misaligned band-pass filter setting and self-phase modulation effect to realize mode-locking.

[0035] Specifically, for the mode-locked laser implemented by the present application, two cascaded regenerators are included to generate pulses through spectral broadening and spectral filtering. The structure determines that the high peak power pulse is fully broadened in spectrum after self-phase modulation and can pass through the filter, while the low peak power pulse is not fully broadened in spectrum and is isolated by the band-pass filter. The process is cascaded, which shows a significantly enhanced saturable absorption effect: through high-intensity pulses, while suppressing pulses below a certain intensity, only pulses strong enough can cross the interval of the two filters to enter the next arm.

[0036] The embodiment of the present application has the following aspects:

[0037] The embodiment of the present application provides a mode-locked laser, a first regenerator includes a first fiber combiner, a first ytterbium-doped fiber, a fiber coupler and a pulse broadening device, and a second regenerator includes a second fiber combiner, a second ytterbium-doped fiber, a pulse compression device, a spectral broadening fiber and a band-pass filter; the pulse is broadened in spectrum in the first regenerator and the second regenerator due to the self-phase modulation effect; the pulse broadening device and the center wavelength of the band-pass filter have an interval, and the band-passes are also different; therefore, the two regenerators can realize the design of staggered band-pass filters, and have the spectral broadening caused by the self-phase modulation effect, and the mode-locked pulse output can be realized by the energy input of the first pump source and the second pump source; the present application reduces the peak power by broadening the pulse to reduce the nonlinear effect, and further compresses and outputs the pulse, so that the high-energy output pulse is generated in the fiber mode-locked laser, and the interval between the pulse broadening device and the center wavelength of the band-pass filter can effectively prevent noise and continuous components from oscillating, and improve the pulse quality. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a structure schematic diagram of a ytterbium-doped fiber mode-locked laser provided by the embodiment of the present application;

[0039] Figure 2 is a structure schematic diagram of another ytterbium-doped fiber mode-locked laser provided by the embodiment of the present application;

[0040] Figure 3 is a schematic diagram of pulse output spectrum of a ytterbium-doped fiber mode-locked laser provided by the embodiment of the present application;

[0041] Figure 4 is a schematic diagram of autocorrelation measurement result of pulse output of a ytterbium-doped fiber mode-locked laser provided by the embodiment of the present application;

[0042] Figure 2Reference signs: first pump source 1, first fiber combiner 2, first ytterbium-doped fiber 3, seed laser 4, fiber coupler 5, fiber circulator 6, first fiber collimator 7, first chirped Bragg grating 8, second pump source 9, second fiber combiner 10, second ytterbium-doped fiber 11, second fiber collimator 12, isolator 13, first polarization beam splitting cube 14, quarter wave plate 15, first half wave plate 16, second polarization beam splitting cube 17, second half wave plate 18, third fiber collimator 19, spectrum broadening fiber 20, band pass filter 21, second chirped Bragg grating 22. DETAILED DESCRIPTION

[0043] The application will be further described below in conjunction with the drawings and specific embodiments. For the step numbers in the following embodiments, they are only set for the convenience of description, and the order between the steps is not limited in any way, and the execution order of each step in the embodiments can be adaptively adjusted according to the understanding of those skilled in the art.

[0044] As shown in the drawings, Figure 1 Figure 1 is a structural schematic diagram of a ytterbium-doped fiber mode-locked laser provided by an embodiment of the application. The embodiment provides a ytterbium-doped fiber mode-locked laser, which comprises a first pump source, a first regenerator, a second pump source and a second regenerator; wherein,

[0045] The first regenerator and the second regenerator are connected in a head-to-tail manner; the first pump source provides energy for the first regenerator; and the second pump source provides energy for the second regenerator.

[0046] The first regenerator comprises a ytterbium-doped fiber and a pulse broadening device; the second regenerator comprises an isolator, a pulse compression device, a spectrum broadening fiber and a band pass filter; the center wavelength of the pulse broadening device has a spacing with the center wavelength of the band pass filter; and the passband of the pulse broadening device has a spacing with the passband of the band pass filter.

[0047] The pulse broadening device comprises a first chirped Bragg grating; and the pulse compression device comprises a second chirped Bragg grating.

[0048] The first regenerator and the second regenerator are both used for band pass filtering and generating spectrum broadening caused by self-phase modulation effect.

[0049] Specifically, the pulse broadening device performs normal dispersion broadening on the incoming pulse, and then the pulse is output to the second regenerator for amplification. The pulse broadening device also has the function of band pass filtering.

[0050] ​Specifically, the spectrum-broadening fiber is used to nonlinearly broaden the spectrum of the pulse compressed by the pulse compression device, allowing a portion of the spectrum to pass through a bandpass filter. The amount of nonlinear spectrum broadening is adjusted by the length of the spectrum broadening.

[0051] This embodiment provides a ytterbium-doped fiber mode-locked laser, including a first pump source, a first regenerator, a second pump source, and a second regenerator. The first regenerator includes a ytterbium-doped fiber and a pulse broadening device, while the second regenerator includes an isolator, a pulse compression device, a spectral broadening fiber, and a bandpass filter. The pulse undergoes spectral broadening due to self-phase modulation in both the ytterbium-doped fiber and the spectral broadening fiber. The center wavelengths of the pulse broadening device and the bandpass filter are spaced apart, and their bandpasses are different. Therefore, the two regenerators can achieve a misaligned bandpass filter design with spectral broadening due to self-phase modulation. Combined with the energy input from the first and second pump sources, mode-locked pulse output can be achieved. This invention reduces peak power and mitigates nonlinear effects by broadening the pulse, enabling the generation of high-energy output pulses in the fiber mode-locked laser. Simultaneously, the center wavelength spacing between the pulse broadening device and the bandpass filter effectively prevents noise and continuous component oscillation, improving pulse quality.

[0052] like Figure 2 As shown, Figure 2 This is a schematic diagram of another ytterbium-doped fiber mode-locked laser provided in an embodiment of the present invention. This embodiment provides another ytterbium-doped fiber mode-locked laser, including a first pump source 1, a first fiber combiner 2, a first ytterbium-doped fiber 3, a seed laser 4, a fiber coupler 5, a fiber circulator 6, a first fiber collimator 7, a first chirped volume Bragg grating 8, a second pump source 9, a second fiber combiner 10, a second ytterbium-doped fiber 11, a second fiber collimator 12, an isolator 13, a first polarization beam splitter 14, a quarter-wave plate 15, a first half-wave plate 16, a second polarization beam splitter 17, a second half-wave plate 18, a third fiber collimator 19, a spectrum broadening fiber 20, a bandpass filter 21, and a second chirped volume Bragg grating 22.

[0053] The pulse broadening device includes an optical fiber circulator 6, a first optical fiber collimator 7, and a first chirped Bragg grating 8; the pulse compression device includes a second optical fiber collimator 12, an isolator 13, a first polarization beam splitter 14, a quarter-wave plate 15, a first half-wave plate 16, a second polarization beam splitter 17, a second half-wave plate 18, a third optical fiber collimator 19, and a second chirped Bragg grating 22.

[0054] The first optical fiber combiner 2, the first Yb-doped optical fiber 3, the optical fiber coupler 5, the pulse stretching device, the second Yb-doped optical fiber 11, the isolator 13, the pulse compression device, the spectral stretching optical fiber 20 and the band-pass filter 21 are sequentially connected in an optical fiber fusion manner to form a ring resonator. The first pump source 1 and the second pump source 9 provide energy for the ring resonator, and the ring resonator and the first pump source 1 and the second pump source 9 form a mode-locked oscillator; and mode-locked pulse output is realized through the mode-locked oscillator.

[0055] The center wavelength of the pulse stretching device is spaced from the center wavelength of the band-pass filter 21; and the passband of the pulse stretching device is spaced from the passband of the band-pass filter 21.

[0056] In the embodiment, the first Yb-doped optical fiber 3 performs normal dispersion stretching on the incoming pulse, causes the pulse to produce spectral stretching caused by self-phase modulation effect, and then passes through the pulse stretching device with a band-pass filtering effect.

[0057] Specifically, the spectral stretching optical fiber 20 causes the pulse compressed by the pulse compression device to produce spectral stretching caused by self-phase modulation effect, so that part of the spectrum can pass through the band-pass filter 21. The nonlinear spectral stretching amount is adjusted by the length of the spectral stretching optical fiber 20. In the embodiment of the application, the spectral stretching optical fiber is a PM10-125 optical fiber with a length of 6 m.

[0058] Specifically, when the laser is first operated, the first pump source 1 and the second pump source 9 need to output pump light with a certain power to excite the gain medium in the Yb-doped optical fiber. Since the Yb-doped optical fiber has good heat dissipation performance, a wide absorption band and stable output, it can efficiently couple into the optical fiber, thereby improving the pumping efficiency of the laser, making the pump light effectively coupled into the optical fiber and enabling the laser to work stably. The embodiment also provides a seed laser 4 connected with the optical fiber coupler 5 to form a seed starting device. After the laser is first operated, the pulse produces spectral stretching caused by self-phase modulation effect and pump input in the first Yb-doped optical fiber and the spectral stretching optical fiber through the misaligned band-pass of the pulse stretching device and the band-pass filter, and forms a Mamyshev mechanism. After that, the pump power of the laser and the filter band-pass frequency range and other cavity parameters are fixed, and the mode-locked laser can be started only by starting the seed pulse injection.

[0059] It should be noted that the seed laser 4 used in the embodiment of the application is a passively mode-locked Yb-doped laser, which outputs a seed pulse with a center wavelength of 1030 nm, a bandwidth of 3 nm, a pulse energy of 0.2 nJ and a repetition frequency of 27.7 MHz.

[0060] The embodiment of the present application adopts a chirped fiber Bragg grating with a center wavelength of 1030nm, a bandwidth of 7.8nm, and a dispersion coefficient of 50ps / nm; one end of the optical fiber circulator is connected to the optical fiber coupler 5, and the other end of the optical fiber circulator is connected to the second optical fiber combiner 10.

[0061] In the embodiment, the pulse entering the pulse stretching device is reflected back to the first polarization beam splitter from the second chirped fiber Bragg grating, and then sequentially passes through the third optical fiber collimator, the second half-wave plate, the second polarization beam splitter, the first half-wave plate, the first polarization beam splitter, the isolator, the second optical fiber collimator, and the second doped ytterbium fiber, and finally enters the spectrum stretching fiber.

[0062] Further, the pulse passing through the pulse stretching device 6 has the following characteristics:

[0063] The pulse width is within 0.5-5ps;

[0064] The spectral width is between 5-20nm;

[0065] The pulse energy is greater than 100pJ.

[0066] Specifically, the pulse stretching device normally dispersively stretches the entering pulse to the order of hundreds of picoseconds to nanoseconds, and adjusts the entering pulse according to preset parameters. The preset parameters include center wavelength, bandwidth, and dispersion amount, etc. The stretched pulse enters the second doped ytterbium fiber for amplification.

[0067] Optionally, the optical fiber coupler 5 includes a 2x2 optical fiber coupler; and the splitting ratio of the optical fiber coupler 5 includes 50 / 50.

[0068] The type and performance parameters of the optical fiber coupler are configured according to the implementation requirements.

[0069] Further, the pulse compression device includes a first half-wave plate 16, a second half-wave plate 18, a quarter-wave plate 15, a first polarization beam splitter cube 14, a second polarization beam splitter cube 17, a second optical fiber collimator 12, and a third optical fiber collimator 19.

[0070] Specifically, the pulse passing through the second doped ytterbium fiber sequentially passes through the second optical fiber collimator, the isolator, the first polarization beam splitter cube, the quarter-wave plate, the second chirped fiber Bragg grating, is reflected back to the first polarization beam splitter cube from the second chirped fiber Bragg grating, and then sequentially passes through the first half-wave plate, the second polarization beam splitter cube, the second half-wave plate, the third optical fiber collimator, and finally enters the spectrum stretching fiber.

[0071] Optionally, the pulse compression device is used to output the compressed laser energy according to a preset ratio (optionally >80%).

[0072] Specifically, the pulse compression device compresses the pulse amplified by the second ytterbium-doped fiber 11 according to preset parameters, the preset parameters of the pulse compression device such as the central wavelength, bandwidth and dispersion amount of the pulse are consistent with those of the pulse stretching device, abnormal dispersion is introduced, and the compressed laser energy is outputted according to a preset ratio, and the remaining energy is returned to the spectrum stretching fiber 12.

[0073] Further, the band-pass filter includes a band-pass filter with a bandwidth in the order of nm; the bandwidth of the band-pass filter is smaller than the bandwidth of the pulse stretching device and the bandwidth of the pulse compression device.

[0074] In the embodiment, the center wavelength of the band-pass filter 20 is adjustable in the range of 1030-1040 nm. The band-pass filter 20 used in the embodiment has a bandwidth of 2.8 nm, and the center wavelength is adjustable in the range of 1030-1040 nm. The pump light outputted by the first pump source 1 is incident into the mode-locked oscillator through the first fiber combiner 2; the pump light outputted by the second pump source 9 is incident into the mode-locked oscillator through the second fiber combiner 10; the pump light outputted by the first pump source 1 and the second pump source 9 is in the 980 nm band.

[0075] In the embodiment, the pump light outputted by the first pump source 1 and the second pump source 9 is 976 nm, the maximum pump power is 9 W and 18 W respectively, the output fiber is a 105 / 125 multimode fiber, and the pump light is incident through the 105 / 125 end of the first fiber combiner 2 and the second fiber combiner 10 respectively. The first ytterbium-doped fiber 3 is a Nufern PLMA-YDF-10 / 125-M fiber, and the length is 3.4 m; the second ytterbium-doped fiber 11 is a Nufern PLMA-YDF-14 / 125-UF fiber, and the length is 1.5 m.

[0076] In the embodiment, the working wavelengths of the remaining unexplained devices are all 1030 nm, and the tail fibers are all PM10-125.

[0077] It should be noted that in the mode-locked laser implemented by the present application, a ring resonant cavity is formed by sequentially connecting the first fiber combiner 2, the first ytterbium-doped fiber 3, the fiber coupler 5, the pulse stretching device, the second fiber combiner 10, the second ytterbium-doped fiber 11, the pulse compression device, the spectrum stretching fiber 20 and the band-pass filter 21, the center wavelength and the passband of the band-pass filter 21 and the pulse stretching device are separated, the spectrum stretching caused by the misaligned band-pass filter and the self-phase modulation effect satisfies the Mamyshev mode-locking mechanism, and finally the first pump source and the second pump source provide energy for the resonant cavity to realize the output of mode-locked pulses.

[0078] As Figure 3 ,4 is shown, Figure 3 is a schematic diagram of the pulse output spectrum of a Yb-doped fiber mode-locked laser provided by an embodiment of the present application, Figure 4 is a schematic diagram of the autocorrelation measurement result of the pulse output of a Yb-doped fiber mode-locked laser provided by an embodiment of the present application. In this embodiment, a mode-locked pulse output with a maximum energy of 244 nJ can be obtained.

[0079] The Mamyshev mechanism refers to a passive mode-locking technique used in a mode-locked laser. The mode-locking technique locks together light waves of multiple longitudinal modes so that they overlap in time and interfere to form ultrashort pulses. The Mamyshev mechanism is characterized by mode-locking achieved through the setting of staggered bandpass filters and spectral broadening caused by self-phase modulation.

[0080] Specifically, in the mode-locked laser implemented by the present application, pulses are generated through spectral broadening and spectral filtering. This structure determines that high peak power pulses are fully broadened in spectrum after self-phase modulation and can pass through the filter, while low peak power pulses are not fully broadened in spectrum and are blocked by the bandpass filter. Cascading this process represents a significantly enhanced saturable absorption effect: by high-intensity pulses, while suppressing pulses below a certain intensity, only sufficiently strong pulses can cross the gap between the two filters and enter the next arm.

[0081] In summary, the implementation of the embodiment of the present application has the following beneficial effects:

[0082] The embodiment provides a mode-locked laser, a first fiber combiner 2, a first Yb-doped fiber 3, a fiber coupler 5, a pulse broadening device, a second fiber combiner 10, a second Yb-doped fiber 11, a pulse compression device, a spectral broadening fiber 20, and a bandpass filter 21; the pulse broadening device has a gap with the center wavelength of the bandpass filter, and the bandpass is also different; therefore, the pulse broadening device and the bandpass filter 21 can realize the design of staggered bandpass filters, and the pulse can generate spectral broadening caused by the self-phase modulation effect in the first Yb-doped fiber and the spectral broadening fiber 12, and the energy input of the first pump source and the second pump source can realize the mode-locked pulse output; the present application reduces the peak power by broadening the pulse to reduce the nonlinear effect, and further compresses and outputs the pulse, so as to realize the generation of high-energy output pulses in the fiber mode-locked laser, and the gap between the center wavelengths of the pulse broadening device and the bandpass filter can effectively prevent noise and continuous components from oscillating, and improve the pulse quality.

[0083] It can be seen that the content in the method embodiments is applicable to the system embodiments, the system embodiments specifically implement the same functions as the method embodiments, and achieve the same beneficial effects as the method embodiments.

[0084] The above is a specific description of the preferred embodiments of the application, but the application is not limited to the embodiments described, and those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the application. These equivalent modifications or replacements are all included in the scope defined by the claims of the present application.

Claims

1. A ytterbium-doped fiber mode-locked laser, characterized in that, It includes a first pump source, a first regenerator, a second pump source, and a second regenerator; wherein, The first regenerator and the second regenerator are connected end to end; the first pump source provides energy to the first regenerator; the second pump source provides energy to the second regenerator; The first regenerator includes a first ytterbium-doped fiber and a pulse broadening device; the second regenerator includes a bandpass filter, a pulse compression device, and a spectrum broadening fiber; the center wavelength of the pulse broadening device is spaced apart from the center wavelength of the bandpass filter; the passband of the pulse broadening device is spaced apart from the passband of the bandpass filter. The pulse broadening device includes a first chirped Bragg grating; the pulse compression device includes an isolator and a second chirped Bragg grating; the first chirped Bragg grating and the second chirped Bragg grating are opposite each other in free space; Both the first regenerator and the second regenerator are used for bandpass filtering and to generate spectral broadening due to self-phase modulation effects.

2. The ytterbium-doped fiber mode-locked laser as described in claim 1, characterized in that, The first regenerator also includes a first fiber combiner and a fiber coupler; The first fiber combiner, the first ytterbium-doped fiber, the fiber coupler, and the pulse broadening device are connected in sequence.

3. A ytterbium-doped fiber mode-locked laser as described in claim 2, characterized in that, The pulse broadening device includes an optical fiber circulator, a first optical fiber collimator, and a first chirped volume Bragg grating; wherein, One end of the fiber optic circulator is connected to the fiber optic coupler, and the other end of the fiber optic circulator is connected to the second regenerator.

4. A ytterbium-doped fiber mode-locked laser as described in any one of claims 1-3, characterized in that, The pulses transmitted through the pulse broadening device have the following characteristics: The pulse width is within 0.5-5 ps; The spectral width is between 5 and 20 nm; The pulse energy is greater than 100 pJ.

5. A ytterbium-doped fiber mode-locked laser as described in claim 2, characterized in that, The fiber optic coupler includes a 2×2 fiber optic coupler; the splitting ratio of the fiber optic coupler includes 50 / 50.

6. A ytterbium-doped fiber mode-locked laser as described in claim 3, characterized in that, The second regenerator also includes a second combiner and a second ytterbium-doped fiber; The second bundle combiner, the second ytterbium-doped fiber, the isolator, the pulse compression device, the spectrum broadening fiber, and the bandpass filter are connected in sequence.

7. A ytterbium-doped fiber mode-locked laser as described in claim 6, characterized in that, The pulse compression device further includes a waveplate, a first polarization beam splitter cube, a second polarization beam splitter cube, a second fiber collimator, and a third fiber collimator; one end of the second fiber collimator is connected to the second ytterbium-doped fiber; and one end of the third fiber collimator is connected to the spectrum broadening fiber.

8. A ytterbium-doped fiber mode-locked laser as described in claim 7, characterized in that, The waveplates include half-wave plates and quarter-wave plates.

9. A ytterbium-doped fiber mode-locked laser as described in claim 6, characterized in that, The pulse compression device is used to output the compressed laser energy according to a preset ratio.

10. A ytterbium-doped fiber mode-locked laser as described in claim 6, characterized in that, The bandpass filter includes a bandpass filter with a bandwidth on the order of nm; the bandwidth of the bandpass filter is less than the bandwidth of the pulse broadening device and the bandwidth of the pulse compression device.

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