CN115473117A - High repetition frequency optical fiber optical comb based on burst pulse train modulation - Google Patents
High repetition frequency optical fiber optical comb based on burst pulse train modulation Download PDFInfo
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
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- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
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- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
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- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
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- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/10038—Amplitude control
- H01S3/10046—Pulse repetition rate control
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- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
- H01S3/136—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling devices placed within the cavity
- H01S3/137—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling devices placed within the cavity for stabilising of frequency
Abstract
The invention discloses a burst-pulse-string-modulation-based high-repetition-frequency optical fiber optical comb, which comprises a high-repetition-frequency optical fiber laser, a peak power enhancer, an optical fiber amplifier, an optical coupler, a nonlinear spectrum expander, a carrier envelope frequency offset detection system, a first photoelectric detector and a phase-locked loop feedback module circuit, wherein the high-repetition-frequency optical fiber laser, the peak power enhancer, the optical fiber amplifier, the optical coupler, the nonlinear spectrum expander, the carrier envelope frequency offset detection system, the first photoelectric detector and the phase-locked loop feedback module circuit are sequentially connected and connected into a loop. The invention provides a method for realizing a high repetition frequency optical fiber optical comb, which can provide a reliable high repetition frequency optical comb light source for the application fields of astronomical spectrum measurement, optical communication, laser radar and the like.
Description
Technical Field
The invention relates to the technical field of lasers, in particular to a high repetition frequency optical fiber optical comb based on burst pulse train modulation.
Background
Optical frequency combs (hereinafter referred to as optical combs) have been of great value in the fields of application such as optical atomic clocks, generation of ultra-low noise microwave signals, astronomical spectrum calibration, precise ranging and the like since the past two decades of development.
The optical comb is represented by a string of stable pulse sequences with strictly equal time intervals in the time domain, and is represented by comb-shaped optical spectrums with strictly equal frequency intervals in the frequency domain, and is an important bridge for connecting microwave frequency and optical frequency, and is also a precise instrument for generating precise frequency signals. However, the output frequency signal of the free-running mode-locked laser is not stable enough, so that the two frequency components, i.e., the repetition frequency and the carrier envelope frequency offset, are usually doubly locked to improve the frequency stability. The method is a good method for locking the repetition frequency by adjusting the cavity length of the resonant cavity based on a piezoelectric actuator (PZT). An error signal is obtained by beating the repetition frequency signal of the mode locking pulse and the stable frequency signal of the stable frequency microwave source, and the laser resonant cavity is adjusted by utilizing a phase-locked loop feedback loop according to the error signal, so that the repetition frequency locking is realized. For the locking of the carrier envelope frequency offset, as described in patent document CN201410219345, currently, the carrier envelope frequency offset f is usually extracted by first adopting f-2f beat frequency method ceo The signal is then locked to the frequency signal. The method firstly needs to utilize femtosecond pulse pumping nonlinear medium with high peak power to generate a supercontinuum with more than one octave, and then respectively extracts low-frequency signals f n And a high frequency signal f 2n By multiplying the low-frequency signal f n Obtaining a frequency-multiplied signal 2f n Then beat-frequency the frequency-doubled signal and the high-frequency signal to obtain f ceo Signal, finally through phase-locked loop feedback circuit pair f ceo The signal is locked.
Compared with a MHz repetition frequency optical comb, the mode-locking optical fiber optical comb based on the f-2f beat frequency method has certain requirements on pulse peak power, and compared with a GHz repetition frequency optical comb, under the condition of the same average output power, for a GHz repetition frequency high repetition frequency mode-locking optical fiber laser optical comb, the pulse peak power is reduced by more than 1-2 orders of magnitude, the quality of a generated super-continuum spectrum is seriously reduced when a pulse pumps a nonlinear medium, even the super-continuum spectrum spanning one octave can not be generated, the difficulty is caused for extracting a carrier envelope frequency offset signal, and the frequency stability of a GHz repetition frequency optical fiber laser is difficult to realize. The problems result in that no mode-locked fiber laser optical comb method capable of well realizing the repetition frequency above GHz exists at present.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a high repetition frequency optical fiber optical comb based on burst modulation, a high repetition frequency optical fiber laser based on repetition frequency locking, a burst modulation technology and an optical fiber laser amplification technology are combined, femtosecond pulse output and peak power improvement are realized while the characteristics of high repetition frequency pulses are kept, a supercontinuum spanning an octave is generated through a femtosecond pulse pumping nonlinear spectrum expander, finally, extraction and locking of carrier envelope frequency offset are realized based on an f-2f self-reference method and a phase-locked loop technology, the high repetition frequency optical fiber optical comb with the repetition frequency greater than 1GHz is realized, and a reliable high repetition frequency optical comb light source can be provided for the application fields of astronomical spectrum measurement, optical communication, laser radar and the like.
The object of the invention is achieved by at least one of the following solutions.
The invention provides a burst-pulse-string-modulation-based high-repetition-frequency optical fiber optical comb, which comprises a high-repetition-frequency optical fiber laser, a peak power enhancer, an optical fiber amplifier, an optical coupler, a nonlinear spectrum expander, a carrier envelope frequency offset detection system, a first photoelectric detector and a phase-locked loop feedback module circuit, wherein the high-repetition-frequency optical fiber laser, the peak power enhancer, the optical fiber amplifier, the optical coupler, the nonlinear spectrum expander, the carrier envelope frequency offset detection system, the first photoelectric detector and the phase-locked loop feedback module circuit are sequentially connected and connected into a loop;
wherein the high repetition frequency fiber laser with repetition frequency locking is used for outputting the high repetition frequency fiber laser with repetition frequency locked and larger than 1GHzContinuous wave mode-locked picosecond pulses; the peak power enhancer modulates continuous wave mode-locked picosecond pulses with GHz repetition frequency into burst pulse trains with MHz repetition frequency to enhance pulse peak power; the modulated burst pulse train generates femtosecond pulses after being amplified by an optical fiber amplifier and compressed by soliton effect pulses; the femtosecond pulse is divided into two paths of signals by an optical coupler, one path of signals is output as an optical comb signal, and the other path of signals generates a super-continuum spectrum with more than one octave after passing through a nonlinear spectrum expander; further utilizing a carrier envelope frequency offset detection system to obtain a carrier envelope frequency offset signal f ceo And received by the first photodetector; detected f ceo The signal adjusts the pumping power of the high repetition frequency fiber laser locked by the repetition frequency through a phase-locked loop feedback module circuit to realize f ceo And locking the signal, thereby realizing the optical comb for stabilizing the frequency signal output.
Furthermore, the repetition frequency locked high repetition frequency fiber laser is locked on a stable frequency reference source, and can realize continuous wave mode-locked picosecond pulse output with the repetition frequency higher than 1GHz and the repetition frequency locked.
Further, the peak power enhancer is used for realizing the modulation of the high repetition frequency pulse according to the waveform of the applied modulation signal; by loading square wave signals with MHz repetition frequency, continuous waves with GHz repetition frequency are modulated into burst pulse trains with MHz repetition frequency in a mode-locked picosecond pulse mode, so that the pulse peak power is enhanced.
Furthermore, the optical fiber amplifier is a one-stage or multi-stage doped rare earth ion optical fiber amplifier, and the applicable pulse amplification wavelength range of the optical fiber amplifier is matched with the output pulse wavelength of the high repetition frequency optical fiber laser with locked repetition frequency; the fiber amplifier has two functions: firstly, performing power amplification on a modulated burst pulse string with a MHz repetition frequency; and secondly, generating femtosecond pulses by combining a soliton effect pulse compression technology.
Furthermore, the carrier envelope frequency deviation detection system comprises a collimator, a dichroic mirror, a light frequency conversion medium, a time delay device consisting of a first reflecting mirror and a second reflecting mirror, a beam splitter and a narrow-band optical filter,
the collimator is used for converting the supercontinuum signal into a space optical signal, and the dichroic mirror is used for dividing the supercontinuum into a low-frequency signal f n And contains a high-frequency signal f 2n For converting red light to include 2f n The delay device is used for delaying the blue light, and the beam splitter is used for carrying out delay on the signal containing 2f n And a frequency-multiplied signal containing a high-frequency signal f 2n The blue light is combined and beaten to obtain a frequency offset signal f containing a carrier envelope ceo Of the optical signal of (a).
The carrier envelope frequency offset detection system is used for extracting a carrier envelope frequency offset signal f ceo (ii) a The supercontinuum spanning an octave contains a number of frequency components, and each frequency in the optical comb can be represented as f according to the optical comb formula n ＝nf rep +f ceo Wherein f is rep Is the pulse repetition frequency, n denotes the nth frequency; by applying a low-frequency signal f contained in a supercontinuum spanning an octave n And a high frequency signal f 2n Respectively filtering out; low frequency signal f n After frequency doubling, 2f is obtained n Signal, 2f will be n Signal and f 2n Obtaining f after beat frequency of signal ceo Signal (beat frequency process can be formulated: 2f n -f 2n ＝(2nf rep +2f ceo )-(2nf rep +f ceo )＝f ceo )。
Further, the first photodetector is used for receiving the carrier envelope frequency offset f extracted by the carrier envelope frequency offset detection system ceo And converting the optical signal into an electrical signal.
Further, the repetition frequency locked high repetition frequency fiber laser comprises an ultra-short fiber laser resonant cavity, a piezoelectric actuator, a wavelength division multiplexer, a pump light source, an isolator, a coupler, a second photoelectric detector, a band-pass filter, a radio frequency amplifier, a first mixer, a first frequency reference source, a first low-pass filter and a first proportional differential integrator,
the ultra-short fiber laser resonant cavity is used for pumping the ultra-short fiber laser resonant cavity, the ultra-short fiber laser resonant cavity is used for generating continuous wave mode-locked picosecond pulses with repetition frequency larger than GHz, the wavelength division multiplexer is used for outputting the continuous wave mode-locked picosecond pulses generated by the ultra-short fiber laser resonant cavity, the isolator is used for preventing return light from returning to the ultra-short fiber laser resonant cavity to influence a stable mode-locked state, the coupler is used for outputting two paths of signals, one path of signal is used for outputting laser pulse signals, the other path of signal is used for stabilizing frequency, the second photoelectric detector is used for converting the signals with stable frequency into electric signals, the band-pass filter is used for filtering the electric signals to obtain pulse fundamental frequency repetition frequency signals, the radio frequency amplifier is used for carrying out radio frequency amplification on the fundamental frequency repetition frequency signals, the first mixer is used for beating the fundamental frequency repetition frequency signals and the first frequency reference source to obtain low-frequency error signals, the first low-pass filter is used for purifying the error signals, and the first proportional differential integrator is used for driving the piezoelectric actuator to adjust the cavity length of the ultra-short fiber laser resonant cavity according to the purified error signals so as to adjust and adjust the pulse repetition frequency.
Furthermore, the phase-locked loop feedback module circuit is used for locking f ceo A signal; by receiving f from the first photodetector ceo The signal and a stable frequency reference source are subjected to beat frequency to obtain an error signal, and the error signal is fed back to a high repetition frequency fiber laser with locked repetition frequency to further adjust the pumping power to realize f ceo And locking the signal.
Further, the phase-locked loop feedback module circuit comprises a band-pass filter, a radio frequency amplifier, a second mixer, a second frequency reference source, a second low-pass filter and a second proportional-derivative integrator,
the band-pass filter is used for filtering the carrier envelope frequency offset signal f ceo For radio frequency amplification of the signal, a second mixer for frequency shifting the carrier envelope by a frequency offset signal f ceo Beat-frequency with the stable frequency signal generated by the second frequency reference source to obtain a low-frequency error signal, filter out useless frequency components in the error signal, and integrate with the second proportional-derivative integratorThe error signal generates a regulation signal to regulate the pumping power of the pumping light source so as to realize the carrier envelope frequency offset signal f ceo Is locked.
Compared with the prior art, the invention has the following beneficial effects:
the core component of the invention is a high repetition frequency fiber laser with locked repetition frequency. Continuous wave mode-locked picosecond pulses with the repetition frequency larger than 1GHz are modulated into a burst pulse train sequence with the repetition frequency of MHz through an optical modulation technology, the peak power of femtosecond pulses can be effectively improved while the characteristics of GHz repetition frequency pulse signals are maintained by combining an optical fiber laser amplification technology, a high-quality supercontinuum spanning one octave is generated, good conditions are created for extracting and locking carrier envelope frequency offset signals, and therefore the repetition frequency optical comb larger than 1GHz is achieved.
The invention provides a burst pulse string modulation-based high-repetition-frequency optical fiber optical comb, which is characterized in that a peak power enhancer is used for modulating continuous waves with GHz repetition frequency into burst pulses with MHz repetition frequency, the peak power of femtosecond pulses can be effectively improved while the characteristics of GHz repetition-frequency pulse signals are maintained in the optical amplification process, a high-quality super-continuum spectrum is generated, good conditions are created for extracting and locking carrier envelope frequency offset signals, and the purpose of realizing the optical comb with the repetition frequency above GHz is achieved.
Drawings
Fig. 1 is a schematic structural diagram of a burst modulation-based high repetition frequency optical fiber comb according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a repetition frequency locked high repetition frequency fiber laser according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of a carrier envelope frequency offset detection system according to an embodiment of the present invention.
Fig. 4 is a circuit diagram of a pll feedback control module according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, specific embodiments of the present invention are described below with reference to the accompanying drawings.
The invention provides a high repetition frequency optical fiber optical comb based on burst pulse train modulation, which comprises a high repetition frequency optical fiber laser 1-1 with locked repetition frequency, a peak power intensifier 1-2, an optical fiber amplifier 1-3, an optical coupler 1-4, a nonlinear spectrum expander 1-5, a carrier envelope frequency deviation detection system 1-6, a first photoelectric detector 1-7 and a phase-locked loop feedback module circuit 1-8, as shown in figure 1.
The high repetition frequency fiber laser 1-1 with locked repetition frequency is used for outputting continuous wave mode-locked picosecond pulses with locked repetition frequency and more than 1 GHz; the peak power enhancer 1-2 is used for modulating continuous wave mode-locked picosecond pulses with GHz repetition frequency into burst pulse trains with MHz repetition frequency so as to enhance pulse peak power; the modulated burst pulse train is amplified by an optical fiber amplifier 1-3 to generate femtosecond pulses; the femtosecond pulse is divided into two paths of signals by the optical coupler 1-4, one path of signals is output as optical comb signals, and the other path of signals generates a super-continuum spectrum with more than one octave after the nonlinear spectrum expander 1-5 is pumped; further acquiring a carrier envelope frequency offset signal f by using a carrier envelope frequency offset detection system 1-6 ceo And received by the first photodetector 1-7; detected carrier envelope frequency offset signal f ceo The signal adjusts the pumping power of the high repetition frequency fiber laser 1-1 locked by the repetition frequency through a phase-locked loop feedback module circuit 1-8 to realize f ceo And locking the signal, thereby realizing the optical comb for stabilizing the frequency signal output.
In some embodiments of the present invention, the peak power booster 1-2 is an amplitude electro-optical modulator, and modulates the high repetition frequency pulse according to the waveform of the applied modulation signal; by loading square wave signals with MHz repetition frequency, continuous waves with GHz repetition frequency are modulated into burst pulse trains with MHz repetition frequency in mode-locked picosecond pulses, so that pulse peak power is enhanced.
In some embodiments of the present invention, the optical fiber amplifier 1-3 is one or more cascade doped rare earth ion optical fiber amplifiers, and the applicable pulse amplification wavelength range is matched with the output pulse wavelength of the repetition frequency locked high repetition frequency optical fiber laser 1-1. The fiber amplifiers 1-3 serve two functions: firstly, performing power amplification on a modulated burst pulse string with a MHz repetition frequency; and secondly, generating femtosecond pulses by combining a soliton effect pulse compression technology.
In some embodiments of the present invention, the nonlinear optical spectrum expander 1-5 is a high nonlinear optical fiber, which is pumped by femtosecond pulses to generate a supercontinuum spanning an octave.
In some embodiments of the present invention, the repetition frequency locked high repetition frequency fiber laser 1-1, a laser structure of which is shown in fig. 2, includes an ultra-short fiber laser resonator 2-1, a piezoelectric actuator 2-2, a wavelength division multiplexer 2-3, a pump light source 2-4, an isolator 2-5, a coupler 2-6, a second photodetector 2-7, a band-pass filter 2-8, a radio frequency amplifier 2-9, a first mixer 2-10, a first frequency reference source 2-11, a first low-pass filter 2-12, and a first proportional differential integrator 2-13.
Wherein, the pump light source 2-4 pumps the ultrashort fiber laser resonant cavity 2-1 through the wavelength division multiplexer 2-3, combine the passive mode locking technology, produce the continuous wave mode locking picosecond pulse with repetition frequency greater than 1 GHz; continuous wave mode-locked picosecond pulses generated by the ultrashort optical fiber laser resonant cavity 2-1 are output through a signal end of a wavelength division multiplexer 2-3, and are divided into two paths by a coupler 2-6 after passing through an isolator 2-5, wherein one path is used for laser signal output, the other path is used for frequency stabilization, and the isolator 2-5 is used for preventing return light from returning to the ultrashort optical fiber laser resonant cavity 2-1 to influence a stable mode-locked state; the signal for frequency stabilization is converted into an electric signal by a second photoelectric detector 2-7, a pulse fundamental frequency repetition frequency signal is left after passing through a band-pass filter 2-8, the fundamental frequency repetition frequency signal is subjected to beat frequency with a stable first frequency reference source 2-11 in a first mixer 2-10 after being amplified by a radio frequency amplifier 2-9, and a low-frequency error signal is obtained; the error signal is input to a first proportional differential integrator 2-13 after being purified by a first low-pass filter 2-12; the first proportional differential integrator 2-13 drives the piezoelectric actuator 2-2 according to the error signal to adjust the cavity length of the ultrashort fiber laser resonant cavity 2-1, so that the pulse repetition frequency is adjusted and controlled, and the repetition frequency signal larger than 1GHz is locked on a stable frequency reference source.
In some embodiments of the present invention, the carrier envelope frequency shift detection system 1-6, as shown in FIG. 3, includes a collimator 3-1, a dichroic mirror 3-2, an optical frequency conversion medium 3-3, a first mirror 3-4, a second mirror 3-5, a beam splitter 3-6, and a narrow band optical filter 3-7.
Wherein the collimator 3-1 converts the supercontinuum signal across an octave transmitted in the optical fiber into a space optical signal, the supercontinuum across an octave contains a plurality of frequency components, and each frequency in the optical comb can be expressed as f according to an optical comb formula n ＝nf rep +f ceo Wherein f is rep Is the pulse repetition frequency, n denotes the nth frequency; the dichroic mirror 3-2 divides the supercontinuum into a low-frequency signal f n And contains a high-frequency signal f 2n "blue light"; the "red light" becomes to contain 2f after passing through the light frequency conversion medium 3-3 n The frequency-doubled signal enters a beam splitter 3-6; in order to make the pulses in the 'blue light' and the 'red light' overlap in time as much as possible to obtain the best beat frequency effect, the 'blue light' enters the beam splitter 3-6 after being delayed by a delay device consisting of a first mirror 3-4 and a second mirror 3-5; containing 2f n And a frequency-multiplied signal containing a high-frequency signal f 2n 3-6 beams of the blue light are combined in the beam splitter and beat to obtain a frequency offset signal f containing a carrier envelope ceo The beat frequency process is formulated as: 2f of n -f 2n ＝(2nf rep +2f ceo )-(2nf rep +f ceo )＝f ceo (ii) a Finally, useless frequency components are filtered through the narrow-band optical filters 3-7 to obtain a carrier envelope frequency offset signal f ceo 。
In some embodiments of the present invention, the pll feedback module 1-8, as shown in fig. 4, includes a band pass filter 4-1, a rf amplifier 4-2, a second mixer 4-3, a second frequency reference source 4-4, a second low pass filter 4-5, and a second pid integrator 4-6.
Wherein, f ceo After filtering useless frequency components by a band-pass filter 4-1, the signal is amplified by a radio frequency amplifier 4-2 and input to one end of a second mixer 4-3; the other end of the second mixer 4-3 is connected to a frequency reference source 4-3, and the carrier envelope frequency offset signal f ceo Beating the stable frequency signal generated by the second frequency reference source 4-4 in the second mixer 4-3 to obtain a low-frequency error signal; after useless frequency components of the error signal are filtered by a second low-pass filter 4-5, the error signal is input to a second proportional-derivative integrator 4-6; the second proportional-differential integrator 4-6 generates a regulation signal according to the error signal to adjust the pumping power of the pumping light source 2-4 so as to realize f ceo And locking the signal.
The above-mentioned embodiment is one of the embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments and test examples, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof and are included in the scope of the present invention.
Claims (10)
1. A high repetition frequency optical fiber optical comb based on burst modulation is characterized by comprising a high repetition frequency optical fiber laser (1-1), a peak power enhancer (1-2), an optical fiber amplifier (1-3), an optical coupler (1-4), a nonlinear spectrum expander (1-5), a carrier envelope frequency offset detection system (1-6), a first photoelectric detector (1-7) and a phase-locked loop feedback module circuit (1-8), wherein the high repetition frequency optical fiber laser (1-1), the peak power enhancer (1-2), the optical fiber amplifier (1-3), the optical coupler (1-4), the nonlinear spectrum expander (1-5) are sequentially connected and connected into a loop;
wherein, the high repetition frequency fiber laser (1-1) with locked repetition frequency is used for outputting continuous wave mode-locked picosecond pulses with locked repetition frequency and more than 1 GHz; the peak power enhancer (1-2) is used for modulating continuous wave mode-locked picosecond pulses with GHz repetition frequency into burst pulse trains with MHz repetition frequency; the optical fiber amplifier (1-3) is used for amplifying the modulated burst pulse train and then generating femtosecond pulses; the optical coupler (1-4) is used for dividing the femtosecond pulse into two paths of signals, one path of signal is output as an optical comb signal, and the other path of signal generates a super-continuum spectrum with more than one octave after passing through the nonlinear spectrum expander (1-5); carrierA wave envelope frequency offset detection system (1-6) for acquiring a carrier envelope frequency offset signal f based on the supercontinuum ceo A first photodetector (1-7) for receiving a carrier envelope frequency offset signal f ceo (ii) a The phase-locked loop feedback module circuit (1-8) is used for adjusting the pumping power of the high-repetition-frequency optical fiber laser (1-1) locked by the repetition frequency to realize f ceo And signal locking is carried out, so that the optical comb for stabilizing frequency signal output is realized.
2. The optical comb of claim 1, wherein the repetition frequency locked high repetition frequency fiber laser (1-1) is locked to a stable frequency reference source, and is capable of achieving continuous wave mode locked picosecond pulse output with a repetition frequency greater than 1GHz and a locked repetition frequency.
3. A burst-modulation-based high repetition frequency fiber optical comb according to claim 1, wherein the peak power booster (1-2) modulates the high repetition frequency pulses according to the waveform of the applied modulation signal; and modulating continuous wave mode-locked picosecond pulses with GHz repetition frequency into burst pulse trains with MHz repetition frequency by loading square wave signals with MHz repetition frequency.
4. The optical comb of claim 1, wherein the optical fiber amplifiers (1-3) are one or more cascaded doped rare-earth ion optical fiber amplifiers, and the applicable pulse amplification wavelength range is matched with the output pulse wavelength of the repetition frequency locked high repetition frequency optical fiber laser (1-1).
5. A high repetition frequency optical fiber comb based on burst modulation according to claim 1, wherein the optical fiber amplifier (1-3) has two functions: firstly, performing power amplification on a modulated burst pulse train with MHz repetition frequency; and secondly, generating femtosecond pulses by combining a soliton effect pulse compression technology.
6. A high repetition frequency fiber optic comb based on burst modulation according to claim 1, wherein the first photodetector (1-7) is configured to receive a carrier envelope frequency offset signal f extracted by a carrier envelope frequency offset detection system (1-6) ceo And converts it from an optical signal to an electrical signal.
7. The burst-modulation-based high repetition frequency fiber optic comb according to claim 1, wherein the carrier envelope frequency offset detection system (1-6) comprises a collimator (3-1), a dichroic mirror (3-2), an optical frequency conversion medium (3-3), a delay device, a beam splitter (3-6) and a narrow band optical filter (3-7),
the collimator (3-1) is used for converting the supercontinuum signal into a space light signal, and the dichroic mirror (3-2) is used for dividing the supercontinuum into a signal f containing low frequency n And contains a high-frequency signal f 2n The blue light and light frequency conversion medium (3-3) is used for converting red light into a light containing 2f n The delay device is used for delaying the blue light, and the beam splitter (3-6) is used for delaying the signal containing 2f n And a frequency-multiplied signal containing a high-frequency signal f 2n The blue light is combined and beaten to obtain a frequency offset signal f containing a carrier envelope ceo Of the optical signal of (a).
8. The burst-modulation-based high repetition frequency fiber optical comb according to any one of claims 1 to 7, characterized in that the repetition frequency locked high repetition frequency fiber laser (1-1) comprises an ultra-short fiber laser resonator (2-1), a piezoelectric actuator (2-2), a wavelength division multiplexer (2-3), a pump light source (2-4), an isolator (2-5), a coupler (2-6), a second photodetector (2-7), a band-pass filter (2-8), a radio frequency amplifier (2-9), a first mixer (2-10), a first frequency reference source (2-11), a first low-pass filter (2-12), and a first proportional differential integrator (2-13),
the pump light source (2-4) is used for pumping the ultrashort optical fiber laser resonant cavity (2-1), the ultrashort optical fiber laser resonant cavity (2-1) is used for generating continuous wave mode-locked picosecond pulses with repetition frequency larger than 1GHz, the wavelength division multiplexer (2-3) is used for outputting the continuous wave mode-locked picosecond pulses generated by the ultrashort optical fiber laser resonant cavity (2-1), the isolator (2-5) is used for preventing return light from returning to the ultrashort optical fiber laser resonant cavity (2-1) to influence a stable mode-locked state, the coupler (2-6) is used for outputting two paths of signals, one path of signal is used for outputting a laser pulse signal, the other path of signal is used for stabilizing the frequency, a second photoelectric detector (2-7) is used for converting the signal with the stable frequency into an electric signal, a band-pass filter (2-8) is used for filtering the electric signal to obtain a pulse fundamental frequency repetition frequency signal, a radio-frequency amplifier (2-9) is used for carrying out radio-frequency amplification on the fundamental frequency repetition frequency signal, a first mixer (2-10) is used for beating the fundamental frequency repetition frequency signal and a first frequency reference source (2-11) to obtain a low-frequency error signal, a first low-pass filter (2-12) is used for purifying the error signal, and a first proportional differential integrator (2-13) is used for driving a piezoelectric actuator (2-2) according to the purified error signal to adjust the cavity length of an ultra-short fiber laser resonant cavity (2-1) so as to adjust and control the pulse repetition frequency.
9. A high repetition frequency fiber optic comb based on burst modulation according to claim 8 wherein said phase locked loop feedback module circuit (1-8) is adapted to lock the carrier envelope frequency offset signal f ceo (ii) a By shifting the carrier envelope frequency of the signal f received by the first photodetector (1-7) ceo Beating frequency with a stable frequency reference source to obtain an error signal, feeding the error signal back to a high repetition frequency fiber laser (1-1) with repetition frequency locking to adjust the pumping power of a pumping light source (2-4) to realize a carrier envelope frequency offset signal f ceo And (6) locking.
10. The optical comb of claim 9, wherein the PLL feedback module (1-8) comprises a band-pass filter (4-1), a radio frequency amplifier (4-2), a second mixer (4-3), a second frequency reference source (4-4), a second low-pass filter (4-5) and a second PID integrator (4-6),
the band-pass filter (4-1) is used for filtering the carrier envelope frequency offset signal f ceo A radio frequency amplifier (4-2) for radio frequency amplifying the signal and a second mixer (4-3) for frequency shifting the carrier envelope by a signal f ceo Beat frequency with stable frequency signal generated by a second frequency reference source (4-4) to obtain low-frequency error signal, a second low-pass filter (4-5) for filtering useless frequency components in the error signal, and a second proportional-differential integrator (4-6) for generating regulation signal according to the error signal to regulate the pumping power of a pumping light source (2-4) to realize carrier envelope frequency deviation signal f ceo Locking of (2).
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