Tunable low-repetition-frequency optical fiber optical frequency comb light source

Abstract

The utility model relates to the field of ultrafast lasers, and provides a tunable low-repetition-frequency optical fiber optical frequency comb light source. Comprising an all-polarization-maintaining ultrafast fiber laser seed source, a fiber pre-amplification stage module, a fiber main amplification stage module, a grating pair dispersion matching module, a super-continuum spectrum generation module and an f-2f self-reference detection module which are sequentially arranged along a light path. The full polarization-maintaining ultrafast fiber laser seed source is used for outputting continuously tunable signal light with low repetition frequency; the optical fiber pre-amplification stage module and the optical fiber main amplification stage module are used for carrying out self-similarity amplification and power amplification on the input signal light in sequence; the grating pair dispersion matching module is used for performing dispersion matching on the amplified signal light; the super-continuum spectrum generation module is used for coupling the signal light subjected to dispersion matching into a high-nonlinearity optical fiber to generate a super-continuum spectrum light source; and the f-2f self-reference detection module is used for measuring the super-continuum spectrum light source to obtain a light frequency comb with low repetition frequency.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of ultrafast laser, especially to a tunable low repetition rate fiber optical frequency comb light source. BACKGROUND

[0002] The statements in this section merely provide background information related to the utility model and do not necessarily constitute prior art.

[0003] The all-polarization-maintaining fiber laser based on SESAM mode locking is a kind of laser with compact structure, good beam quality, low insertion loss and stable ultrashort pulse output. The 1550nm band corresponding to the erbium-doped fiber laser has mature application in the optical fiber communication window, and the mid-infrared band has important application in biomedical imaging. The ultrashort laser of 1550nm band can also produce supercontinuum, which is an indispensable key technology for optical frequency comb. The Chinese patent with application number "CN2019105541209" provides a tunable high repetition rate single-cavity double-coherent optical frequency comb light source. By using the first adjustable optical delay in the first adjustable optical filter and the second adjustable optical delay in the second adjustable optical filter, the repetition rate adjustability of the single-cavity double-comb is improved, which increases from the initial non-adjustable to the adjustable in the GHz range. However, the patent realizes a high repetition rate optical frequency comb light source.

[0004] The generation of supercontinuum and f-2f self-reference technology are important components of optical comb. For the erbium-doped fiber laser of 1.55μm band, the method of generating supercontinuum is to splice a high nonlinear fiber (HNLF) after the amplification stage. This method is simple in structure and easy to integrate, and can realize the all-fiber system. After obtaining the supercontinuum, the f0 signal can be generated by using the f-2f self-reference technology to multiply the low frequency part and beat with the high frequency. The f-2f beat frequency technology multiplies the low frequency component of the supercontinuum, and then performs optical beat with the corresponding high frequency component on the photodetector, thereby obtaining the f0 signal. The f-2f self-reference detection system can be generally divided into non-collinear and collinear structures, but the non-collinear structure is more complex than the collinear structure, and the stability is also poorer.

[0005] The methods of realizing the repetition rate tunable of fiber laser include introducing adjustable spatial light path in the resonant cavity, controlling the cavity length by piezoelectric ceramic, and controlling the effective cavity length of the resonant cavity by temperature control of refractive index. The method of introducing adjustable spatial light path in the resonant cavity has the disadvantages of complex structure, low coupling efficiency and poor stability. The method of controlling the cavity length by temperature has strict requirements on the environment and temperature control equipment.

[0006] At present, the fiber optical frequency comb based on SESAM mode-locked ultrafast laser can realize low repetition frequency and adjustable frequency simultaneously, but there is no such fiber optical frequency comb in the literature. Content of the utility model

[0007] In order to solve the technical problem that there is no fiber optical frequency comb with low repetition frequency, stable output, compact structure and adjustable repetition frequency at present, the utility model provides a kind of adjustable low repetition frequency fiber optical frequency comb light source, and the repetition frequency of this light source is low and continuously adjustable, while meeting compact structure and stable output, the accuracy and flexibility of frequency measurement are improved.

[0008] In order to realize the above-mentioned purpose, the utility model adopts the following technical scheme:

[0009] The utility model provides a kind of adjustable low repetition frequency fiber optical frequency comb light source, comprising: full polarization maintaining ultrafast fiber laser seed source, fiber preamplification stage module, fiber main amplification stage module, grating dispersion matching module, supercontinuum spectrum generation module and f-2f self-referencing detection module are arranged in sequence along the light path;

[0010] Full polarization maintaining ultrafast fiber laser seed source is used to output low repetition frequency continuously adjustable signal light;

[0011] Fiber preamplification stage module and fiber main amplification stage module are sequentially self-similar amplification and power amplification to the input signal light;

[0012] Grating dispersion matching module is used to match the dispersion of the amplified signal light;

[0013] Supercontinuum spectrum generation module is used to couple the dispersion-matched signal light into high nonlinear fiber to generate supercontinuum spectrum light source;

[0014] F-2f self-referencing detection module is used to measure the supercontinuum spectrum light source to obtain low repetition frequency optical frequency comb.

[0015] Further, the full polarization maintaining ultrafast fiber laser seed source includes polarization maintaining fiber coupler and wavelength division multiplexer hybrid device, first polarization maintaining erbium-doped fiber, first polarization maintaining fiber wavelength division multiplexer and polarization maintaining fiber ring resonator connected in sequence to form a ring cavity;

[0016] The first port of the polarization maintaining fiber ring resonator is connected to the first polarization maintaining fiber wavelength division multiplexer and the second LD pump source respectively, the first polarization maintaining fiber wavelength division multiplexer is connected to the second LD pump source, the second port of the polarization maintaining fiber ring resonator is connected to the semiconductor saturable absorber mirror, and the third port of the polarization maintaining fiber ring resonator is connected to the polarization maintaining fiber coupler and wavelength division multiplexer hybrid device and the fiber preamplification stage module respectively, and the polarization maintaining fiber coupler and wavelength division multiplexer hybrid device is also connected to the first LD pump source;

[0017] The first polarization maintaining erbium-doped fiber is connected with a piezoelectric ceramic module, and the piezoelectric ceramic module is connected with a piezoelectric ceramic control module.

[0018] Further, the pump light output by the first LD pump source and the second LD pump source is input into the first polarization maintaining erbium-doped fiber through the polarization maintaining fiber coupler, the polarization maintaining fiber wavelength division multiplexer hybrid device and the pump port of the first polarization maintaining fiber wavelength division multiplexer to generate stimulated radiation, and the low-repetition-frequency continuous tunable signal light is formed through the polarization maintaining fiber circulator and the semiconductor saturable absorber mirror and then output.

[0019] Further, the piezoelectric ceramic module comprises a cylindrical stainless steel block, a multilayer piezoelectric ceramic stack, a piezoelectric ceramic drive, a controller connection line and a stress sensor connection line, the piezoelectric ceramic module is fused on the first polarization maintaining erbium-doped fiber, the cylindrical stainless steel block is connected with the piezoelectric ceramic drive through the multilayer piezoelectric ceramic stack, and the piezoelectric ceramic drive is provided with the controller connection line and the stress sensor connection line.

[0020] Further, the fiber pre-amplification stage module comprises a first polarization maintaining fiber isolator, a second polarization maintaining erbium-doped fiber, a second polarization maintaining fiber wavelength division multiplexer and a third LD pump source, the signal light output by the all-polarization-maintaining ultrafast fiber laser seed source is sequentially input into the second polarization maintaining fiber wavelength division multiplexer through the first polarization maintaining fiber isolator and the second polarization maintaining erbium-doped fiber, and the third LD pump source inputs pump light into the second polarization maintaining fiber wavelength division multiplexer to form particle beam inversion, so as to self-similarly amplify the signal light.

[0021] Further, the fiber main amplification stage module comprises a second polarization maintaining fiber isolator, a third polarization maintaining erbium-doped fiber, a third polarization maintaining fiber wavelength division multiplexer and a fourth LD pump source, the signal light output by the fiber pre-amplification stage module is sequentially input into the third polarization maintaining fiber wavelength division multiplexer through the second polarization maintaining fiber isolator and the third polarization maintaining erbium-doped fiber, and the fourth LD pump source inputs pump light into the third polarization maintaining fiber wavelength division multiplexer to form particle number inversion, so as to power amplify the signal light.

[0022] Further, the grating dispersion matching module comprises a first fiber collimator, a first transmission grating, a second transmission grating and a second fiber collimator arranged in sequence along an optical path, the signal light output by the fiber main amplification stage module is output by the first fiber collimator, and after the first transmission grating and the second transmission grating perform grating matching at the same time, the signal light is coupled into the second fiber collimator.

[0023] Further, the first fiber collimator, the first transmission grating, the second transmission grating and the second fiber collimator are all fixed on an electric displacement table, the first fiber collimator and the first transmission grating are linked and displaced on the electric displacement table, and the second transmission grating and the second fiber collimator are linked and displaced on the electric displacement table.

[0024] Further, the supercontinuum spectrum generation module comprises a high nonlinearity fiber, and the color dispersion matched signal light is coupled into the high nonlinearity fiber to realize spectrum broadening and generate a supercontinuum spectrum light source.

[0025] Further, the f-2f self-reference detection module comprises a first collimating lens, a second focusing lens, a periodically poled lithium niobate crystal, a second collimating lens, a second focusing lens, a narrowband filter and a photodetector arranged in sequence along an optical path, the supercontinuum spectrum light source is coupled into the periodically poled lithium niobate crystal through the first collimating lens and the second focusing lens, the newly generated frequency-doubled light and the original fundamental frequency light pass through the second collimating lens and the second focusing lens and then are transmitted to the photodetector through the narrowband filter in a same line, after the carrier envelope phase offset frequency signal is acquired, the condition of the laser oscillator is adjusted to obtain a low repetition frequency optical frequency comb.

[0026] Compared with the prior art, the utility model has the advantages of:

[0027] The utility model discloses a low repetition frequency and tunable optical frequency comb realized by SESAM mode-locked laser, which simplifies the structure of the optical frequency comb and obtains more accurate frequency measurement.

[0028] The utility model discloses a low repetition frequency and tunable optical frequency comb realized by SESAM mode-locked laser, which simplifies the structure of the optical frequency comb and obtains more accurate frequency measurement. BRIEF DESCRIPTION OF DRAWINGS

[0029] The description and drawings of the utility model constitute a part of the utility model and are used to provide further understanding on the utility model, and the illustrative embodiment of the utility model and its description are used to explain the utility model, and do not constitute improper limitation on the utility model.

[0030] Figure 1 It is the optical path structure diagram of tunable low repetition frequency optical fiber optical frequency comb light source shown in the utility model;

[0031] Figure 2 It is the piezoelectric ceramic module amplification detail drawing shown in the utility model;

[0032] I, a full-polarization ultrafast fiber laser seed source, II, a fiber pre-amplification module, III, a fiber main amplification module, IV, a grating dispersion matching module, V, an ultrashort supercontinuum spectrum generation module, VI, an f-2f self-referenced detection module, 1, a first LD pump source, 2, a polarization maintaining fiber coupler and wavelength division multiplexer hybrid device, 3, a first polarization maintaining erbium-doped fiber, 4, a second LD pump source, 5, a first polarization maintaining fiber wavelength division multiplexer, 6, a polarization maintaining fiber circulator, 6.1, a first port of the polarization maintaining fiber circulator, 6.2, a second port of the polarization maintaining fiber circulator, 6.3, a third port of the polarization maintaining fiber circulator, 7, a semiconductor saturable absorber mirror (SESAM), 8, a piezoelectric ceramic module (PZT), 9, a piezoelectric ceramic control module, 10, a first polarization maintaining fiber isolator, 11, a second polarization maintaining erbium-doped fiber, 12, a second polarization maintaining fiber wavelength division multiplexer, 13, a third LD pump source, 14, a second polarization maintaining fiber isolator, 15, a third polarization maintaining erbium-doped fiber, 16, a third polarization maintaining fiber wavelength division multiplexer, 17, a fourth LD pump source, 18.1, a first fiber collimator, 18.2, a second fiber collimator, 19.1, a first transmission grating, 19.2, a second transmission grating, 19.3, an electrically driven displacement stage, 20, a high nonlinear fiber (HNLF), 21, a first collimating lens, 22, a second focusing lens, 23, a periodically poled lithium niobate crystal (PPLN), 24, a second collimating lens, 25, a second focusing lens, 26, a narrowband filter (BP), 27, a photodetector (PD), 28, an erbium-doped fiber (EDF), 29, a cylindrical stainless steel block, 30, a multilayer piezoelectric ceramic stack, 31, a piezoelectric ceramic drive, 32, a controller connection line, 33, a stress sensor (SGS) connection line. DETAILED DESCRIPTION

[0033] The utility model will be further described below in combination with the drawings and examples.

[0034] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the utility model. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the utility model belongs.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the utility model. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the specification, the presence of a feature, step, operation, device, component and / or their combination is indicated.

[0036] Self-similar amplification: When femtosecond pulses are transmitted in a positive dispersion gain fiber amplifier, under suitable conditions, the interaction between dispersion, SPM and gain can gradually evolve the pulse into a parabolic pulse during the amplification process. This pulse has linear chirp and can be easily compressed to below 100 fs by a pair of diffraction gratings or prisms.

[0037] As shown in Figure 1 The embodiment provides a tunable low repetition rate fiber optical frequency comb source, comprising: a full polarization maintaining ultrafast fiber laser seed source I, a fiber pre-amplification module II, a fiber main amplification module III, a grating pair dispersion matching module IV, an ultrabroadband spectrum generation module V, and an f-2f self-reference detection module VI.

[0038] The full polarization maintaining ultrafast fiber laser seed source I is connected in sequence by a polarization maintaining fiber coupler and a wavelength division multiplexer hybrid device 2, a first polarization maintaining erbium-doped fiber 3, a first polarization maintaining fiber wavelength division multiplexer 5, a polarization maintaining fiber ring first port 6.1 of a polarization maintaining fiber ring 6, a polarization maintaining fiber ring second port 6.2 of the polarization maintaining fiber ring 6, a semiconductor saturable absorber mirror (SESAM) 7, and a polarization maintaining fiber ring third port 6.3 of the polarization maintaining fiber ring 6 to form a ring cavity through fiber fusion.

[0039] The pump light output by the first LD pump source 1 and the second LD pump source 4 is input into the first polarization maintaining erbium-doped fiber 3 through the pump port of the polarization maintaining fiber coupler and the polarization maintaining fiber wavelength division multiplexer hybrid device (which integrates the function of the polarization maintaining fiber coupler on the basis of the polarization maintaining fiber wavelength division multiplexer) 2 and the first polarization maintaining fiber wavelength division multiplexer 5 to generate stimulated radiation, and forms a low repetition rate mode-locked laser output through the polarization maintaining fiber ring 6 and the semiconductor saturable absorber mirror (SESAM) 7. The selected first polarization maintaining erbium-doped fiber 3 has a length of about 1 m and a dispersion value D = 15 ps / (km·nm) at 1550 nm, and is available from Coherent company; the first LD pump source 1 and the second LD pump source 4 are both 974 nm continuous light output, and the maximum output power of the two pumps is 1 W, which is available from DoGain company; the semiconductor saturable absorber mirror (SESAM) 7 has a modulation depth of 55%, which is available from BATOP company; and the tail fibers of other devices are all PM1550 polarization maintaining fibers, and the low repetition rate mode-locked laser output with a repetition rate of less than 10 MHz can be realized by controlling the length of the tail fiber and the pump power.

[0040] The stress change of the first polarization maintaining erbium-doped fiber 3 is controlled by the piezoelectric ceramic module (PZT) 8 through the piezoelectric ceramic control module 9, so as to realize the continuous tunable repetition rate of the laser. Figure 2As shown in the figure, the cylindrical piezoelectric ceramic module (PZT) 8 is mounted in the middle section of the first polarization maintaining erbium-doped optical fiber 3 by adhesive, wherein the piezoelectric ceramic module contains a cylindrical stainless steel block with the same diameter as the piezoelectric ceramic drive diameter, both of which are fixed to a multilayer piezoelectric ceramic stack, and the piezoelectric ceramic drive is connected with the piezoelectric ceramic control module 9 containing the stress sensor (SGS) to realize closed-loop operation, accurately adjusting the cavity length and the repetition frequency.

[0041] Wherein, the piezoelectric ceramic control module 9 controls the stress change of the piezoelectric ceramic module (PZT) 8 to the first polarization maintaining erbium-doped optical fiber 3, which is realized by existing programs and is not within the protection scope of the utility model.

[0042] As shown in the figure, Figure 1 The fiber pre-amplification stage module II is composed of a first polarization maintaining optical fiber isolator 10, a second polarization maintaining erbium-doped optical fiber 11, a second polarization maintaining optical fiber wavelength division multiplexer 12, and a third LD pump source 13 connected in sequence by fiber fusion. The signal light output by the all-polarization-maintaining ultrafast fiber laser seed source I passes through the first polarization maintaining optical fiber isolator 10 and is input into the second polarization maintaining erbium-doped optical fiber 11, while the third LD pump source 13 inputs pump light into the second polarization maintaining optical fiber wavelength division multiplexer 12 to form particle number inversion, and after signal light extraction, self-similar amplification is realized. Among them, the second polarization maintaining erbium-doped optical fiber 11 used has a length of about 2m, and its dispersion value D at 1550nm is -12ps / (km·nm), which can be purchased from Exail Company; the third LD pump source (13) used is a 974nm continuous light output, with a maximum output power of 1W, which can be purchased from DoGain Company.

[0043] As shown in the figure, Figure 1 The fiber main amplification stage module III is composed of a second polarization maintaining optical fiber isolator 14, a third polarization maintaining erbium-doped optical fiber 15, a third polarization maintaining optical fiber wavelength division multiplexer 16, and a fourth LD pump source 17 connected in sequence by fiber fusion. The signal light output by the fiber pre-amplification stage module II passes through the second polarization maintaining optical fiber isolator 14 and is input into the third polarization maintaining erbium-doped optical fiber 15, while the fourth LD pump source 17 inputs pump light into the third polarization maintaining optical fiber wavelength division multiplexer 16 to form particle number inversion, and after signal light extraction, power amplification is realized. Among them, the third polarization maintaining erbium-doped optical fiber 15 used has a length of about 1m, and its dispersion value D at 1550nm is -12ps / (km·nm), which can be purchased from Exail Company; the fourth LD pump source 17 used is a 974nm continuous light output, with a maximum output power of 1W, which can be purchased from DoGain Company.

[0044] As shown in the figure, Figure 1As shown in the figure, the grating pair dispersion matching module IV includes: a first fiber collimator 18.1, a second fiber collimator 18.2, a first transmission grating 19.1, a second transmission grating 19.2, and a motorized displacement stage 19.3. The signal light output from the fiber main amplification stage module III is output by the first fiber collimator 18.1, and after dispersion matching through the grating pair of the first transmission grating 19.1 and the second transmission grating 19.2, it is coupled into the second fiber collimator 18.2. The above-mentioned devices are all fixed on the motorized displacement stage 19.3. Among them, the first fiber collimator 18.1 and the first transmission grating 19.1 are linked and displaced on the motorized displacement stage 19.3, and the second transmission grating 19.2 and the second fiber collimator 18.2 are linked and displaced on the motorized displacement stage 19.3, ensuring the coupling efficiency while performing dispersion matching during the moving distance.

[0045] As Figure 1 shown in the figure, the supercontinuum generation module V includes a section of highly nonlinear fiber (HNLF) 20. After the signal light matched by the grating pair dispersion matching module IV is coupled into the highly nonlinear fiber (HNLF) 20, spectral broadening is achieved, generating a supercontinuum with a width of 1000 nm - 2200 nm, that is, greater than one octave.

[0046] As Figure 1 shown in the figure, the f - 2f self - reference detection module VI includes: a first collimating lens 21, a second focusing lens 22, a periodically poled lithium niobate crystal (PPLN) 23, a second collimating lens 24, a second focusing lens 25, a narrow - band filter (BP) 26, and a photodetector (PD) 27. The supercontinuum light source is coupled into the periodically poled lithium niobate crystal (PPLN) 23 through the first collimating lens 21 and the second focusing lens 22. The 2200 nm long - wave component is frequency - doubled to 1100 nm. The newly generated 1100 nm frequency - doubled light and the original 1100 nm fundamental - frequency light pass through the second collimating lens 24 and the second focusing lens 25 and then collinearly pass through the narrow - band filter (BP) 26 and are transmitted to the photodetector (PD) 27 to obtain the f0 signal. After obtaining the carrier - envelope phase offset frequency signal f0 using the above f - 2f self - reference detection module, the conditions of the laser oscillator are actively feedback - controlled, such as adjusting the pump light power or the piezoelectric ceramic. Finally, the carrier - envelope phase offset is locked to obtain an optical frequency comb with a low repetition frequency.

[0047] While precisely adjusting the cavity length and repetition frequency by controlling the piezoelectric ceramic module (PZT) 8 as described above, the dispersion in the all - polarization - maintaining ultrafast fiber laser seed source I also changes. At this time, by adjusting the motorized displacement stage 19.3 in the grating pair dispersion matching module IV to change the distance between the two transmission gratings, the dispersion can be rematched, realizing continuous tunability of the repetition frequency of the final optical frequency comb.

[0048] As Figure 2As shown, the piezoelectric ceramic module (PZT) 8 includes a cylindrical stainless steel block 29, a multilayer piezoelectric ceramic stack 30, a piezoelectric ceramic drive 31, a controller connecting line 32 and a stress sensor (SGS) connecting line 33, the piezoelectric ceramic module (PZT) 8 is fused on the doped optical fiber (EDF) 28, the cylindrical stainless steel block 29 is connected to the piezoelectric ceramic drive 31 through the multilayer piezoelectric ceramic stack 30, and the piezoelectric ceramic drive 31 is provided with the controller connecting line 32 and the stress sensor (SGS) connecting line 33.

[0049] The ultrafast laser shows a comb sequence with equal frequency intervals (comb interval equals the laser pulse repetition frequency) in the frequency domain, and the effective cavity length of the laser determines the time interval T of the pulse in the time domain R And the repetition frequency f of the laser r ;

[0050]

[0051] In the formula: c is the speed of light; n c The refractive index of the transmission medium in the cavity; L is the geometric cavity length, in the frequency domain, the interval of the frequency comb is equal to the repetition frequency of the pulse. In the time domain, f0 is determined by the carrier envelope phase :

[0052]

[0053] Among them The mismatch between the group velocity and the phase velocity. f0 is the frequency of the frequency tooth closest to the frequency zero point in the comb sequence, and the frequency of each comb tooth can be expressed as:

[0054] f n =nf r +f0

[0055] Among them, n represents the serial number of the comb tooth. Therefore, for a mode-locked laser, as long as f r And f0 are locked at the same time, the optical comb can be obtained.

[0056] The utility model discloses a cavity length of piezoelectric ceramic can be reduced by increasing, thereby obtaining the low repetition frequency fiber optical frequency comb light source of tunable, through piezoelectric ceramic control cavity length, stability is good, and easy control and quantitative adjustment.

[0057] The utility model discloses utilize semiconductor saturable absorber mirror (SESAM) realizes mode-locked laser, after the pre-amplification level module II of optical fiber, the main amplification level module III of optical fiber carries out the amplification to signal light, and the pulse after amplification is matched to dispersion by grating dispersion matching module IV, obtains the pulse of near Fourier transmission limit, obtains the supercontinuum spectrum of more than one octave again through high nonlinear fiber (HNLF), finally utilizes f-2f self-referencing detection module VI to combine active carrier envelope phase frequency locking method, obtains the light frequency comb of low repetition frequency and adjustable repetition frequency, solved the problem that the current can have low repetition frequency, output stable, compact structure and the problem that the repetition frequency of fiber light frequency comb source is adjustable lacks.

[0058] The above only is the preferred embodiment of the utility model and does not use for limiting the utility model, and for the skilled in the art, the utility model can have various changes and changes. Any modification, equivalent replacement, improvement etc. that is made within the spirit and principle of the utility model should include in the protection scope of the utility model.

Claims

1. A tunable low repetition rate fiber optical frequency comb source, characterized in that, include: The following components are arranged sequentially along the optical path: a fully polarization-maintaining ultrafast fiber laser seed source, a fiber pre-amplification stage module, a fiber main amplification stage module, a grating pair dispersion matching module, a supercontinuum generation module, and an f-2f self-reference detection module. A seed source for a fully polarization-maintaining ultrafast fiber laser, used to output continuously tunable signal light with low repetition frequency; The fiber optic pre-amplification stage module and the fiber optic main amplification stage module sequentially perform self-similar amplification and power amplification on the input signal light; The grating-to-dispersion matching module is used to perform dispersion matching on the amplified signal light; The supercontinuum generation module is used to couple the dispersion-matched signal light into a highly nonlinear optical fiber to generate a supercontinuum light source. The f-2f self-reference probe module is used to measure supercontinuum light sources and obtain a low-repetition-frequency optical comb.

2. The tunable low repetition rate fiber optical frequency comb source of claim 1, wherein, The fully polarization-maintaining ultrafast fiber laser seed source includes a hybrid device of polarization-maintaining fiber coupler and wavelength division multiplexer, a first polarization-maintaining erbium-doped fiber, a first polarization-maintaining fiber wavelength division multiplexer, and a polarization-maintaining fiber circulator, which are connected in sequence to form a ring cavity. The first port of the polarization-maintaining fiber circulator is connected to the first polarization-maintaining fiber wavelength division multiplexer and the second LD pump source, respectively. The first polarization-maintaining fiber wavelength division multiplexer is connected to the second LD pump source. The second port of the polarization-maintaining fiber circulator is connected to the semiconductor saturable absorber mirror. The third port of the polarization-maintaining fiber circulator is connected to the hybrid device of polarization-maintaining fiber coupler and wavelength division multiplexer and the fiber pre-amplification stage module, respectively. The hybrid device of polarization-maintaining fiber coupler and wavelength division multiplexer is also connected to the first LD pump source. The first polarization-maintaining erbium-doped fiber is connected to the piezoelectric ceramic module, which in turn is connected to the piezoelectric ceramic control module.

3. The tunable low repetition rate fiber optical frequency comb source of claim 2, wherein, Pump light output from the first LD pump source and the second LD pump source is input into the first polarization-maintaining erbium-doped fiber through a hybrid device of polarization-maintaining fiber coupler and polarization-maintaining fiber wavelength division multiplexer and the pump port of the first polarization-maintaining fiber wavelength division multiplexer to generate stimulated emission. After passing through the polarization-maintaining fiber circulator and the semiconductor saturable absorber mirror, it forms a low-repetition-frequency continuously tunable signal light and is output.

4. The tunable low repetition rate fiber optical frequency comb source of claim 2 or 3, characterized in that, The piezoelectric ceramic module includes a cylindrical stainless steel block, a multi-layer piezoelectric ceramic stack, a piezoelectric ceramic driver, a controller connection line, and a stress sensor connection line. The piezoelectric ceramic module is fused to a first polarization-maintaining erbium-doped optical fiber. The cylindrical stainless steel block is connected to the piezoelectric ceramic driver through the multi-layer piezoelectric ceramic stack. The piezoelectric ceramic driver is equipped with a controller connection line and a stress sensor connection line.

5. The tunable low repetition rate fiber optical frequency comb source of claim 1, wherein, The fiber preamplification stage module includes a first polarization-maintaining fiber isolator, a second polarization-maintaining erbium-doped fiber, a second polarization-maintaining fiber wavelength division multiplexer, and a third LD pump source. The signal light output from the seed source of the fully polarization-maintaining ultrafast fiber laser sequentially passes through the first polarization-maintaining fiber isolator and the second polarization-maintaining erbium-doped fiber into the second polarization-maintaining fiber wavelength division multiplexer. At the same time, the third LD pump source inputs pump light into the second polarization-maintaining fiber wavelength division multiplexer to form particle beam inversion, thereby performing self-similar amplification on the signal light.

6. The tunable low repetition rate fiber optical frequency comb source of claim 1, wherein, The fiber main amplification stage module comprises a second polarization maintaining fiber isolator, a third polarization maintaining erbium-doped fiber, a third polarization maintaining fiber wavelength division multiplexer and a fourth LD pump source, the signal light output by the fiber pre-amplification stage module enters the third polarization maintaining fiber wavelength division multiplexer through the second polarization maintaining fiber isolator and the third polarization maintaining erbium-doped fiber in sequence, and the fourth LD pump source inputs pump light into the third polarization maintaining fiber wavelength division multiplexer to form population inversion, thereby power amplifying the signal light.

7. The tunable low repetition rate fiber optical frequency comb source of claim 1, wherein, The grating dispersion matching module comprises a first fiber collimator, a first transmission grating, a second transmission grating and a second fiber collimator arranged in sequence along an optical path, the signal light output by the fiber main amplification stage module is output by the first fiber collimator, and after the first transmission grating and the second transmission grating are simultaneously subjected to dispersion matching, the signal light is coupled into the second fiber collimator.

8. The tunable low repetition rate fiber optical frequency comb source of claim 7, wherein, The first fiber collimator, the first transmission grating, the second transmission grating and the second fiber collimator are all fixed on the motorized displacement stage, the first fiber collimator and the first transmission grating are linked and displaced on the motorized displacement stage, and the second transmission grating and the second fiber collimator are linked and displaced on the motorized displacement stage.

9. The tunable low repetition rate fiber optical frequency comb source of claim 1, wherein, The supercontinuum generation module comprises a high nonlinearity fiber, the signal light subjected to dispersion matching is coupled into the high nonlinearity fiber to realize spectrum widening, thereby generating a supercontinuum light source.

10. The tunable low repetition rate fiber optical frequency comb source of claim 1, wherein, The f-2f self-reference detection module comprises a first collimating lens, a second focusing lens, a periodically poled lithium niobate crystal, a second collimating lens, a second focusing lens, a narrowband filter and a photodetector arranged in sequence along an optical path, the supercontinuum light source is coupled into the periodically poled lithium niobate crystal through the first collimating lens and the second focusing lens, the newly generated frequency-doubled light and the original fundamental light are collinearly transmitted to the photodetector through the second collimating lens and the second focusing lens after passing through the narrowband filter, after the carrier envelope phase frequency shift signal is obtained, the conditions of the laser oscillator are adjusted to obtain a low repetition frequency optical frequency comb.

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