Tunable low-repetition-frequency optical fiber optical frequency comb light source and generation method

Abstract

The invention relates to the field of ultrafast lasers, and provides a tunable low-repetition-frequency optical fiber optical frequency comb light source and a generation method. 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 invention relates to the technical field of ultrafast lasers, and in particular to a tunable low repetition frequency optical fiber frequency comb light source. Background Art

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

[0003] The fully polarization-maintaining fiber laser based on SESAM mode locking is a laser with a 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 applications in the optical fiber communication window, and its mid-infrared band also has important applications in biomedical imaging. In addition, ultrafast lasers in the 1550nm band can also generate supercontinuum spectra, which is also an indispensable key technology for optical frequency combs. The Chinese patent with application number "CN2019105541209" provides an adjustable high repetition rate single-cavity dual-coherent optical frequency comb light source. By using the first adjustable optical delay device and the second adjustable optical delay device in the first adjustable optical filter and the second adjustable optical filter, the adjustability of the repetition frequency of the single-cavity dual-comb is improved, so that it is increased from the initial non-adjustable to 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 combs. For erbium-doped fiber lasers in the 1.55μm band, the method to generate supercontinuum is to fuse a section of high nonlinear fiber (HNLF) after the amplifier stage. This method has a simple structure and is easy to integrate, and can realize the full fiberization of the system. After obtaining the supercontinuum, the f-2f self-reference technology can be used to double the low-frequency part and beat it with the high frequency to generate the f0 signal. The f-2f beat technology obtains the f0 signal by doubling the low-frequency component of the supercontinuum and then optically beating it with the corresponding high-frequency component on the photodetector. The f-2f self-reference detection system can generally be divided into two structures: non-collinear and collinear. However, the non-collinear structure is more complex than the collinear structure and has poorer stability.

[0005] Methods to achieve tunable repetition frequency of fiber lasers include introducing an adjustable spatial optical path inside the resonant cavity, controlling the cavity length through piezoelectric ceramics, and controlling the refractive index through temperature to control the effective cavity length of the resonant cavity. The method of introducing an adjustable spatial optical path inside the resonant cavity has the disadvantages of complex structure, low coupling efficiency and poor stability. The method of controlling the cavity length through temperature has strict requirements on the environment and temperature control equipment.

[0006] At present, there is no documented fiber optical frequency comb based on SESAM mode-locked ultrafast laser that can achieve both low repetition rate and adjustable frequency. Summary of the invention

[0007] In order to solve the current technical problem of lack of a fiber optical frequency comb light source that has low repetition rate, stable output, compact structure and adjustable repetition rate, the present invention provides a tunable low repetition rate fiber optical frequency comb light source and a generation method thereof, the light source has a low repetition rate and the repetition rate is continuously tunable, while meeting the requirements of compact structure and stable output, the accuracy and flexibility of frequency measurement are improved.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A first aspect of the present invention provides a tunable low repetition rate fiber optic frequency comb source.

[0010] A tunable low repetition rate fiber optical frequency comb light source, comprising: a fully polarization-maintaining ultrafast fiber laser seed source, a fiber pre-amplifier module, a fiber main amplifier module, a grating pair dispersion matching module, a supercontinuum generation module and an f-2f self-reference detection module arranged in sequence along an optical path;

[0011] Fully polarization-maintaining ultrafast fiber laser seed source, used to output low repetition rate continuously tunable signal light;

[0012] The optical fiber pre-amplification stage module and the optical fiber main amplifier stage module perform self-similar amplification and power amplification on the input signal light in turn;

[0013] A grating pair dispersion matching module is used to perform dispersion matching on the amplified signal light;

[0014] A supercontinuum generation module is used to couple the dispersion-matched signal light into a highly nonlinear optical fiber to generate a supercontinuum light source;

[0015] The f-2f self-reference detection module is used to measure supercontinuum light sources and obtain optical frequency combs with low repetition rates.

[0016] Further, the fully polarization-maintaining ultrafast fiber laser seed source comprises a polarization-maintaining fiber coupler and a wavelength division multiplexer hybrid device, a first polarization-maintaining erbium-doped fiber, a first polarization-maintaining fiber wavelength division multiplexer, and a polarization-maintaining fiber circulator, which are sequentially connected to form a ring cavity;

[0017] The first port of the polarization-maintaining fiber circulator is respectively connected to the first polarization-maintaining fiber wavelength division multiplexer and the second LD pump source, 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 respectively connected to the polarization-maintaining fiber coupler and the wavelength division multiplexer hybrid device and the optical fiber pre-amplifier stage module, and the polarization-maintaining fiber coupler and the wavelength division multiplexer hybrid device are also connected to the first LD pump source;

[0018] The first polarization-maintaining erbium-doped optical fiber is connected to the piezoelectric ceramic module, and the piezoelectric ceramic module is connected to the piezoelectric ceramic control module.

[0019] Furthermore, 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 a polarization-maintaining fiber coupler, a polarization-maintaining fiber wavelength division multiplexer hybrid device and a pump port of the first polarization-maintaining fiber wavelength division multiplexer to generate stimulated radiation, and is formed into a low-repetition-frequency continuously tunable signal light through a polarization-maintaining fiber circulator and a semiconductor saturable absorber mirror, and is output.

[0020] Furthermore, the piezoelectric ceramic module includes a cylindrical stainless steel block, a multi-layer piezoelectric ceramic stack, a piezoelectric ceramic driver, a controller connecting wire and a stress sensor connecting wire. The piezoelectric ceramic module is fused to the 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 provided with a controller connecting wire and a stress sensor connecting wire.

[0021] Furthermore, the fiber pre-amplification 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 by the full polarization-maintaining ultrafast fiber laser seed source sequentially enters the second polarization-maintaining fiber wavelength division multiplexer through the first polarization-maintaining fiber isolator and the second polarization-maintaining erbium-doped fiber. At the same time, the third LD pump source inputs the pump light into the second polarization-maintaining fiber wavelength division multiplexer to form a particle beam inversion, and performs self-similar amplification on the signal light.

[0022] Furthermore, the optical fiber main amplifier stage module includes a second polarization-maintaining optical fiber isolator, a third polarization-maintaining erbium-doped optical fiber, a third polarization-maintaining optical fiber wavelength division multiplexer and a fourth LD pump source. The signal light output by the optical fiber pre-amplifier stage module passes through the second polarization-maintaining optical fiber isolator and the third polarization-maintaining erbium-doped optical fiber in sequence and enters the third polarization-maintaining optical fiber wavelength division multiplexer. At the same time, the fourth LD pump source inputs the pump light into the third polarization-maintaining optical fiber wavelength division multiplexer to form a population inversion, thereby power amplifying the signal light.

[0023] Furthermore, the grating pair dispersion matching module includes a first fiber collimator, a first transmission grating, a second transmission grating and a second fiber collimator arranged in sequence along the optical path. The signal light output by the fiber main amplifier stage module is output by the first fiber collimator, and after being dispersed matched by the first transmission grating and the second transmission grating grating pair at the same time, it is coupled to the second fiber collimator.

[0024] Furthermore, the first fiber collimator, the first transmission grating, the second transmission grating and the second fiber collimator are all fixed on an electric translation stage, the first fiber collimator and the first transmission grating are displaced in a linked manner on the electric translation stage, and the second transmission grating and the second fiber collimator are displaced in a linked manner on the electric translation stage.

[0025] Furthermore, the supercontinuum generation module comprises a section of highly nonlinear optical fiber, and the dispersion-matched signal light is coupled into the highly nonlinear optical fiber to achieve spectrum broadening and generate a supercontinuum light source.

[0026] Furthermore, the f-2f self-reference detection module includes a first collimating lens, a second focusing lens, a periodically poled lithium niobate crystal, a second collimating lens, a second focusing lens, a narrow-band filter and a photodetector arranged in sequence along the 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 frequency light are colinearly transmitted to the photodetector through the narrow-band filter after passing through the second collimating lens and the second focusing lens. After acquiring the carrier envelope phase deviation signal, the conditions of the laser oscillator are adjusted to obtain a low repetition frequency optical frequency comb.

[0027] A second aspect of the present invention provides a method for generating a tunable low repetition rate fiber optical frequency comb light source.

[0028] A method for generating a tunable low repetition rate fiber optical frequency comb light source, applied to the tunable low repetition rate fiber optical frequency comb light source described in the first aspect, comprising:

[0029] The low repetition rate continuously tunable signal light output by the fully polarization-maintaining ultrafast fiber laser seed source is self-similarly amplified and power amplified in turn by the fiber pre-amplifier module and the fiber main amplifier module; the amplified signal light is dispersion matched by the grating dispersion matching module, and the dispersion matched signal light is coupled into the high nonlinear optical fiber by the supercontinuum generation module to generate a supercontinuum light source; the supercontinuum light source is measured by the f-2f self-reference detection module, and after obtaining the carrier-envelope phase offset signal, the main control feedback controls the fully polarization-maintaining ultrafast fiber laser seed source to lock the final carrier-envelope phase offset signal to obtain a low repetition rate optical frequency comb.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention utilizes a SESAM mode-locked laser to realize an optical frequency comb with low repetition frequency and tunable repetition frequency, thereby simplifying the structure of the optical frequency comb and obtaining more precise frequency measurement.

[0032] The present invention utilizes a semiconductor saturable absorber mirror (SESAM) to realize mode-locked laser, amplifies signal light through an optical fiber pre-amplifier module and an optical fiber main amplifier module, performs dispersion matching on the amplified pulse through a grating pair dispersion matching module to obtain a pulse close to the Fourier transmission limit, and then obtains a supercontinuum spectrum exceeding one octave through a high nonlinear fiber (HNLF), and finally utilizes an f-2f self-reference detection module in combination with active carrier envelope phase offset frequency locking to obtain an optical frequency comb with low repetition frequency and tunable repetition frequency, thereby solving the problem of the lack of an optical fiber optical frequency comb light source with low repetition frequency, stable output, compact structure and adjustable repetition frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0034] Figure 1 It is a light path structure diagram of a tunable low repetition rate fiber optical frequency comb light source shown in the present invention;

[0035] Figure 2 is an enlarged detail view of a piezoelectric ceramic module shown in the present invention;

[0036] Among them, I, fully polarization-maintaining ultrafast fiber laser seed source, II, fiber pre-amplifier module, III, fiber main amplifier module, IV, grating pair dispersion matching module, V, supercontinuum generation module, VI, f-2f self-reference detection module, 1, first LD pump source, 2, polarization-maintaining fiber coupler and wavelength division multiplexer hybrid device, 3, first polarization-maintaining erbium-doped fiber, 4, second LD pump source, 5, first polarization-maintaining fiber wavelength division multiplexer, 6, polarization-maintaining fiber circulator, 6.1, first port of polarization-maintaining fiber circulator, 6.2, second port of polarization-maintaining fiber circulator, 6.3, third port of polarization-maintaining fiber circulator, 7, semiconductor saturable absorber mirror (SESAM), 8, piezoelectric ceramic module (PZT), 9, piezoelectric ceramic control module, 10, first polarization-maintaining fiber isolator, 11, second polarization-maintaining erbium-doped fiber, 12, 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 electric translation 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 driver, 32, a controller connecting line, 33, a stress sensor (SGS) connecting line. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0038] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0039] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0040] Self-similar amplification technology: When a femtosecond pulse is transmitted in a positive dispersion gain fiber amplifier, under appropriate conditions, the interaction between dispersion, SPM and gain can gradually evolve the pulse into a parabolic pulse during the amplification process. This pulse has a linear chirp and can be easily compressed to less than 100fs by a pair of diffraction gratings or prisms.

[0041] Embodiment 1

[0042] like Figure 1 As shown, this embodiment provides a tunable low repetition rate fiber optical frequency comb light source, including: a fully polarization-maintaining ultrafast fiber laser seed source I, a fiber pre-amplification stage module II, a fiber main amplifier stage module III, a grating pair dispersion matching module IV, a supercontinuum generation module V and an f-2f self-reference detection module VI.

[0043] The fully polarization-maintaining ultrafast fiber laser seed source I is composed of 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 first port 6.1 of a polarization-maintaining fiber circulator, a second port 6.2 of the polarization-maintaining fiber circulator, a semiconductor saturable absorber mirror (SESAM) 7, and a third port 6.3 of the polarization-maintaining fiber circulator 6, which are sequentially connected into a ring cavity through optical fiber fusion splicing.

[0044] 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 a polarization-maintaining fiber coupler and a polarization-maintaining fiber wavelength division multiplexer hybrid device (the function of the polarization-maintaining fiber coupler is integrated on the basis of the polarization-maintaining fiber wavelength division multiplexer) 2 and a pump port of the first polarization-maintaining fiber wavelength division multiplexer 5 to generate stimulated radiation, and then forms a low repetition rate mode-locked laser output through a polarization-maintaining fiber circulator 6 and a semiconductor saturable absorber mirror (SESAM) 7. Among them, the selected first polarization-maintaining erbium-doped optical fiber 3 has a length of about 1m, a dispersion value D=15ps / (km·nm) at 1550nm, and can be purchased from Coherent; the first LD pump source 1 and the second LD pump source 4 both have 974nm continuous light output, and the maximum output power of both pumps is 1W, which can be purchased from DoGain; the modulation depth of the semiconductor saturable absorber mirror (SESAM) 7 is 55%, which can be purchased from BATOP; the other device pigtails are all PM1550 polarization-maintaining optical fibers, and by controlling the device pigtail length and pump power, a low repetition rate mode-locked laser output with a repetition rate of <10MHz can be achieved.

[0045] The piezoelectric ceramic control module 9 controls the stress change of the piezoelectric ceramic module (PZT) 8 on the first polarization-maintaining erbium-doped optical fiber 3, so as to realize the continuous tunability of the repetition frequency of the laser. Figure 2As shown, a cylindrical piezoelectric ceramic module (PZT) 8 is installed on the middle section of the first polarization-maintaining erbium-doped optical fiber 3 with adhesive, wherein the piezoelectric ceramic module includes a cylindrical stainless steel block with the same diameter as the piezoelectric ceramic drive, and both are fixed to a multilayer piezoelectric ceramic stack. The piezoelectric ceramic drive is connected to a piezoelectric ceramic control module 9 containing a stress sensor (SGS) to realize closed-loop operation and accurately adjust the cavity length and repetition frequency.

[0046] Among them, in the process of controlling the stress change of the first polarization-maintaining erbium-doped optical fiber 3 by the piezoelectric ceramic control module 9, the piezoelectric ceramic control module is implemented by an existing program and is not within the protection scope of the present invention.

[0047] like Figure 1 As shown, the fiber pre-amplification stage module II is composed of a first polarization-maintaining fiber isolator 10, a second polarization-maintaining erbium-doped fiber 11, a second polarization-maintaining fiber wavelength division multiplexer 12, and a third LD pump source 13 connected in sequence by fiber fusion. The signal light output by the full polarization-maintaining ultrafast fiber laser seed source I is input into the second polarization-maintaining erbium-doped fiber 11 through the first polarization-maintaining fiber isolator 10, and at the same time, the third LD pump source 13 inputs the pump light into the second polarization-maintaining fiber wavelength division multiplexer 12 to form a population inversion, and self-similar amplification is achieved after the signal light is extracted. Among them, the second polarization-maintaining erbium-doped fiber 11 used is about 2m long, 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.

[0048] like Figure 1 As shown, the optical fiber main amplifier 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 optical fiber fusion. The signal light output by the optical fiber pre-amplifier module II is input into the third polarization-maintaining erbium-doped optical fiber 15 through the second polarization-maintaining optical fiber isolator 14, and at the same time, the fourth LD pump source 17 inputs the pump light into the third polarization-maintaining optical fiber wavelength division multiplexer 16 to form a population inversion, and the power amplification is realized after the signal light is extracted. Among them, the third polarization-maintaining erbium-doped optical fiber 15 used is about 1m in length, and its dispersion value at 1550nm is D=-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.

[0049] like Figure 1As shown, 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 an electric translation stage 19.3. The signal light output by the fiber main amplifier module III is output by the first fiber collimator 18.1, and is coupled to the second fiber collimator 18.2 after the grating pair of the first transmission grating 19.1 and the second transmission grating 19.2 is dispersed simultaneously. The above components are all fixed on the electric translation stage 19.3, wherein the first fiber collimator 18.1 and the first transmission grating 19.1 are displaced in linkage on the electric translation stage 19.3, and the second transmission grating 19.2 and the second fiber collimator 18.2 are displaced in linkage on the electric translation stage 19.3, so as to ensure the coupling efficiency while performing dispersion matching while moving the spacing.

[0050] like Figure 1 As shown, the supercontinuum generation module V includes a section of highly nonlinear optical fiber (HNLF) 20. After the signal light is matched by the grating pair dispersion matching module IV, it is coupled into the highly nonlinear optical fiber (HNLF) 20 to achieve spectrum broadening, generating a supercontinuum with a width of 1000nm-2200nm, that is, greater than one octave.

[0051] like Figure 1 As shown, 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 narrowband 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, and the long-wave 2200nm component is frequency-doubled to 1100nm. The newly generated 1100nm frequency-doubled light and the original 1100nm fundamental frequency light are colinearly transmitted through the narrowband filter (BP) 26 to the photodetector (PD) 27 to obtain the f0 signal after passing through the second collimating lens 24 and the second focusing lens 25. After obtaining the carrier-envelope phase offset signal f0 using the above-mentioned 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, and finally the carrier-envelope phase offset is locked to obtain a low repetition frequency optical frequency comb.

[0052] While the cavity length and repetition frequency are precisely adjusted by controlling the piezoelectric ceramic module (PZT) 8, the dispersion in the fully polarization-maintaining ultrafast fiber laser seed source I also changes. At this time, the dispersion can be re-matched by adjusting the electric translation stage 19.3 in the grating pair dispersion matching module IV to change the spacing between the two transmission gratings, thereby achieving continuous tunability of the repetition frequency of the final optical frequency comb.

[0053] like 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 driver 31, a controller connecting line 32 and a stress sensor (SGS) connecting line 33. The piezoelectric ceramic module (PZT) 8 is fused to the erbium-doped optical fiber (EDF) 28. The cylindrical stainless steel block 29 is connected to the piezoelectric ceramic driver 31 through the multilayer piezoelectric ceramic stack 30. The piezoelectric ceramic driver 31 is provided with a controller connecting line 32 and a stress sensor (SGS) connecting line 33.

[0054] Ultrafast lasers appear as a comb sequence with equal frequency intervals (the comb interval is equal to the laser pulse repetition frequency) in the frequency domain, while the effective cavity length of the laser determines the pulse time interval T in the time domain. R and the laser repetition frequency f r ;

[0055]

[0056] Where: c is the speed of light; n c is the refractive index of the transmission medium in the cavity; L is the geometric cavity length. In the frequency domain, the spacing of the frequency comb teeth is equal to the repetition frequency of the pulse. In the time domain, f0 is determined by the carrier envelope phase Decide:

[0057]

[0058] Among them It is caused by 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 tooth sequence. The frequency of each comb tooth can be expressed as:

[0059] f n =nf r +f0

[0060] Here, n represents the number of teeth. Therefore, for a mode-locked laser, as long as f r By locking it simultaneously with f0, we can obtain a light comb.

[0061] The present invention can reduce the repetition frequency by increasing the cavity length of the piezoelectric ceramic, thereby obtaining a tunable low-repetition-frequency fiber optical frequency comb light source. The cavity length is controlled by the piezoelectric ceramic, which has good stability and is easy to control and quantize.

[0062] The present invention utilizes a semiconductor saturable absorber mirror (SESAM) to realize mode-locked laser, amplifies signal light through an optical fiber pre-amplification module II and an optical fiber main amplifier module III, performs dispersion matching on the amplified pulse through a grating pair dispersion matching module IV, obtains a pulse close to the Fourier transmission limit, and then obtains a supercontinuum spectrum exceeding one octave through a high nonlinear fiber (HNLF), and finally utilizes an f-2f self-reference detection module VI in combination with an active carrier envelope phase offset frequency locking method to obtain an optical frequency comb with low repetition frequency and tunable repetition frequency, thereby solving the problem of the lack of an optical fiber optical frequency comb light source with low repetition frequency, stable output, compact structure and adjustable repetition frequency.

[0063] Embodiment 2

[0064] This embodiment provides a method for generating a tunable low repetition rate fiber optical frequency comb light source, which is applied to the tunable low repetition rate fiber optical frequency comb light source described in Embodiment 1, comprising:

[0065] The low repetition rate continuously tunable signal light output by the fully polarization-maintaining ultrafast fiber laser seed source is self-similarly amplified and power amplified in turn by the fiber pre-amplifier module and the fiber main amplifier module; the amplified signal light is dispersion matched by the grating dispersion matching module, and the dispersion matched signal light is coupled into the high nonlinear optical fiber by the supercontinuum generation module to generate a supercontinuum light source; the supercontinuum light source is measured by the f-2f self-reference detection module, and after obtaining the carrier-envelope phase offset signal, the main control feedback controls the fully polarization-maintaining ultrafast fiber laser seed source to lock the final carrier-envelope phase offset signal to obtain a low repetition rate optical frequency comb.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A tunable low repetition rate fiber optical frequency comb light source, characterized in that: include: The fully polarization-maintaining ultrafast fiber laser seed source, fiber pre-amplification stage module, fiber main amplifier stage module, grating pair dispersion matching module, supercontinuum generation module and f-2f self-reference detection module are arranged in sequence along the optical path; Fully polarization-maintaining ultrafast fiber laser seed source, used to output low repetition rate continuously tunable signal light; The optical fiber pre-amplification stage module and the optical fiber main amplifier stage module perform self-similar amplification and power amplification on the input signal light in turn; A grating pair dispersion matching module is used to perform dispersion matching on the amplified signal light; A 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 detection module is used to measure supercontinuum light sources and obtain low repetition rate optical frequency combs.

2. The tunable low repetition rate fiber optical frequency comb light source according to claim 1, characterized in that: The fully polarization-maintaining ultrafast fiber laser seed source comprises a polarization-maintaining fiber coupler and a wavelength division multiplexer hybrid device, a first polarization-maintaining erbium-doped fiber, a first polarization-maintaining fiber wavelength division multiplexer, and a polarization-maintaining fiber circulator, which are sequentially connected to form a ring cavity; The first port of the polarization-maintaining fiber circulator is respectively connected to the first polarization-maintaining fiber wavelength division multiplexer and the second LD pump source, 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 respectively connected to the polarization-maintaining fiber coupler and the wavelength division multiplexer hybrid device and the optical fiber pre-amplifier stage module, and the polarization-maintaining fiber coupler and the wavelength division multiplexer hybrid device are also connected to the first LD pump source; The first polarization-maintaining erbium-doped optical fiber is connected to the piezoelectric ceramic module, and the piezoelectric ceramic module is connected to the piezoelectric ceramic control module.

3. The tunable low repetition rate fiber optical frequency comb light source according to claim 2, characterized in that: 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 a polarization-maintaining fiber coupler, a polarization-maintaining fiber wavelength division multiplexer hybrid device and a pump port of the first polarization-maintaining fiber wavelength division multiplexer to generate stimulated radiation, and then forms a low-repetition-frequency continuously tunable signal light through a polarization-maintaining fiber circulator and a semiconductor saturable absorber mirror, and is output.

4. The tunable low repetition rate fiber optical frequency comb light source according to 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 connecting wire and a stress sensor connecting wire. The piezoelectric ceramic module is fused to the 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 provided with a controller connecting wire and a stress sensor connecting wire.

5. The tunable low repetition rate fiber optical frequency comb light source according to claim 1, characterized in that: The fiber pre-amplification 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 by the full polarization-maintaining ultrafast fiber laser seed source enters the second polarization-maintaining fiber wavelength division multiplexer through the first polarization-maintaining fiber isolator and the second polarization-maintaining erbium-doped fiber in sequence. At the same time, the third LD pump source inputs the pump light into the second polarization-maintaining fiber wavelength division multiplexer to form a particle beam inversion, and performs self-similar amplification on the signal light.

6. The tunable low repetition rate fiber optical frequency comb light source according to claim 1, characterized in that: The optical fiber main amplifier stage module comprises a second polarization-maintaining optical fiber isolator, a third polarization-maintaining erbium-doped optical fiber, a third polarization-maintaining optical fiber wavelength division multiplexer and a fourth LD pump source. The signal light output by the optical fiber pre-amplifier stage module passes through the second polarization-maintaining optical fiber isolator and the third polarization-maintaining erbium-doped optical fiber in sequence and enters the third polarization-maintaining optical fiber wavelength division multiplexer. At the same time, the fourth LD pump source inputs the pump light into the third polarization-maintaining optical fiber wavelength division multiplexer to form a population inversion, and performs power amplification on the signal light.

7. The tunable low repetition rate fiber optical frequency comb light source according to claim 1, characterized in that: The grating pair dispersion matching module comprises a first fiber collimator, a first transmission grating, a second transmission grating and a second fiber collimator which are sequentially arranged along the optical path. The signal light output by the fiber main amplifier module is output by the first fiber collimator, and after being dispersed-matched by the first transmission grating and the second transmission grating grating pair simultaneously, it is coupled to the second fiber collimator. The first fiber collimator, the first transmission grating, the second transmission grating and the second fiber collimator are all fixed on an electric translation stage. The first fiber collimator and the first transmission grating are displaced in linkage on the electric translation stage, and the second transmission grating and the second fiber collimator are displaced in linkage on the electric translation stage.

8. The tunable low repetition rate fiber optical frequency comb light source according to claim 1, characterized in that: The supercontinuum generation module comprises a section of highly nonlinear optical fiber, and the dispersion-matched signal light is coupled into the highly nonlinear optical fiber to achieve spectrum broadening and generate a supercontinuum light source.

9. The tunable low repetition rate fiber optical frequency comb light source according to claim 1, characterized in that: 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 narrow-band filter and a photodetector which are sequentially arranged along an optical path. A 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 frequency light are colinearly transmitted to the photodetector through the narrow-band filter after passing through the second collimating lens and the second focusing lens. After acquiring a carrier envelope phase deviation signal, the conditions of a laser oscillator are adjusted to obtain an optical frequency comb with a low repetition frequency.

10. A method for generating a tunable low repetition rate fiber optical frequency comb light source, characterized in that: The tunable low repetition rate fiber optical frequency comb light source as claimed in any one of claims 1 to 9 comprises: The low repetition rate continuously tunable signal light output by the fully polarization-maintaining ultrafast fiber laser seed source is self-similarly amplified and power amplified in turn by the fiber pre-amplifier module and the fiber main amplifier module; the amplified signal light is dispersion matched by the grating dispersion matching module, and the dispersion matched signal light is coupled into the high nonlinear optical fiber by the supercontinuum generation module to generate a supercontinuum light source; the supercontinuum light source is measured by the f-2f self-reference detection module, and after obtaining the carrier-envelope phase offset signal, the main control feedback controls the fully polarization-maintaining ultrafast fiber laser seed source to lock the final carrier-envelope phase offset signal to obtain a low repetition rate optical frequency comb.

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