Optical frequency comb generation method and device based on coherent Thomson scattering

Abstract

The invention provides an optical frequency comb generation method and device based on coherent Thomson scattering. The method comprises the following steps: providing a relativistic electron beam; periodic density modulation is carried out on the relativistic electron beams, so that the relativistic electron beams form equidistant ultra-short bunching structures; the relativistic electron beam after density modulation collides with a beam of incident laser, coherent Thomson scattering occurs, and an optical frequency comb is generated. According to the invention, the electron beam is directly subjected to periodic density modulation, and the coherent Thomson scattering principle is utilized to act with the laser, so that the accurate and controllable space between the optical frequency comb teeth can be realized with relatively low electron beam current energy, and the optical frequency comb is a sub-femtosecond pulse string in the time domain; an optical cavity is not needed, an extreme ultraviolet and soft X-ray optical frequency comb can be generated based on a medium-energy relativistic electron beam, and the system structure is simplified; and the required electron beam energy is low, so that the device is more compact.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photon source and particle beam application, and particularly relates to a method and device for generating optical frequency comb based on coherent Thomson scattering, wherein the optical frequency comb is located in the extreme ultraviolet (EUV) and soft X-ray waveband. BACKGROUND

[0002] An optical frequency comb (OFC) is a new type of high-quality light source, which is a series of uniformly spaced pulse sequences in the time domain and a series of uniformly spaced spectral lines in the frequency domain, similar to the teeth of a comb.

[0003] As a precise optical frequency ruler, the optical frequency comb can closely link the microwave frequency and the optical frequency, and has been widely applied to scientific research fields such as time measurement, precise spectroscopy and basic physics. The optical frequency comb generated based on traditional methods such as mode-locked laser and electro-optic modulator usually has a wavelength range covering from hundreds of nm of ultraviolet waveband to several μm of infrared waveband. If the working range of the optical frequency comb can be further extended to a short wavelength, from vacuum ultraviolet (VUV) to extreme ultraviolet (EUV or XUV) and even to X-ray waveband, the ultra-high precision detection of atomic and molecular structures can be realized; the applicable boundary of quantum electrodynamics (QED) theory can be explored; and the basic physical constants can be accurately measured. If the VUV optical comb technology is applied to the precise measurement of thorium-229 nuclear transition spectrum, the establishment of a new type of optical clock, i.e., nuclear optical clock, will be greatly promoted. However, this has been an important challenge in the scientific community.

[0004] The VUV / XUV optical frequency comb based on traditional laser is mainly obtained by the high harmonic generation of the cavity-enhanced incident laser and inert gas. In recent years, the new generation of X-ray coherent light source represented by free electron laser device can provide higher brightness, better coherence and shorter pulse, which can meet the current scientific research demand for ultra-high spatial and temporal resolution, ultra-short pulse and ultra-high brightness, and plays an almost irreplaceable important role in many basic and applied scientific research fields. Especially the high harmonic free electron laser device based on the external seed modulation method, not only can obtain time, space full coherent and wavelength tunable high brightness radiation in the EUV, soft X-ray band, but also has the potential to obtain short wavelength optical frequency comb by mode locking method due to the periodic time structure. At present, many theoretical and experimental researches have studied and verified the feasibility of generating short wavelength optical frequency comb. However, in order to generate short wavelength light, the above-mentioned accelerator-driven light source device usually needs to have a relatively high energy electron beam, and the scale and investment required by the device are usually very large. Although the performance is strong, the high construction cost makes the number of such large scientific devices very limited, which cannot fully meet the current increasing user demand. Therefore, it is urgent to seek a method to reduce the scale and cost of similar devices.

[0005] The Thomson scattering light source, also known as inverse Compton scattering light source, uses high brightness relativistic electron beam and high power incident laser to interact with each other, which can produce high brightness, short wavelength and quasi-monochromatic scattered light in the direction of electron beam motion. The parameters of the generated scattered light pulse are determined by the parameters of the relativistic electron beam and the incident laser. For the case of backscattering of the incident laser with wavelength λ L and relativistic energy factor γ of the electron beam, due to the Doppler frequency shift, the scattered light with wavelength about λ L / 4γ 2 can be generated. Compared with the free electron laser resonance relation λ R ~ λ u / 2γ 2 , λ R is the wavelength of the free electron laser, and λ u is the undulator period length. Since the laser wavelength λ L used in Thomson scattering is usually much smaller than the undulator period length λ u , the beam current energy required to obtain the same wavelength radiation in Thomson scattering is several orders of magnitude lower than that in synchrotron radiation or free electron laser, and the device scale and cost can be greatly reduced.

[0006] However, in the traditional Thomson scattering, the characteristic length of the electron bunch (about 100 microns) is usually much larger than the wavelength of the scattered light generated by the Thomson scattering, which makes the scattered light out of step and thus usually incoherent, which does not have the condition to obtain the optical frequency comb. SUMMARY

[0007] The purpose of the present application is to provide an optical frequency comb generation method and device based on coherent Thomson scattering, to generate optical frequency combs in the extreme ultraviolet and soft X-ray waveband, and the device is compact.

[0008] In order to achieve the above-mentioned purpose, the present application provides an optical frequency comb generation method based on coherent Thomson scattering, comprising:

[0009] S1: providing a relativistic electron beam;

[0010] S2: periodically modulating the density of the relativistic electron beam to form an equal-interval super-short group structure;

[0011] S3: making the density-modulated relativistic electron beam collide with an incident laser beam to generate coherent Thomson scattering and generate an optical frequency comb.

[0012] The target center wavelength of the optical frequency comb is one of the extreme ultraviolet and soft X-ray waveband, and the longitudinal size of the super-short group structure matches the target center wavelength of the optical frequency comb.

[0013] The density modulation is realized by using a seed laser.

[0014] The seed laser is a free electron laser.

[0015] The method of density modulation is a phase-merging enhanced harmonic generation density modulation method.

[0016] The comb tooth spacing of the optical frequency comb is determined by the frequency of the seed laser.

[0017] The collision angle is determined according to the wavelength of the incident laser and the target center wavelength of the optical frequency comb; when the collision angle is less than 180°, the equivalent wavelength of the incident laser under the equivalent collision included angle of 180° is:

[0018] ,

[0019] wherein, is the equivalent wavelength of the incident laser, is the average beta factor of the relativistic electron, is the center wavelength of the incident laser, is the collision included angle of the incident laser and the electron propagation direction.

[0020] The wavelength of the incident laser is in a terahertz wave band, the pulse width of the incident laser is 2-10 times the wavelength of the incident laser, and the repetition frequency of the incident laser matches the repetition frequency of the relativistic electron beam.

[0021] In another aspect, the application provides a light frequency comb generation device based on coherent Thomson scattering, comprising:

[0022] An electron beam generation and modulation system is used to generate a relativistic electron beam and periodically modulate the density of the relativistic electron beam to form an equally spaced ultrashort group structure;

[0023] A scattering laser system is used to provide incident laser that collides with the relativistic electron beam;

[0024] An interaction region is located in the propagation direction of the relativistic electron beam after density modulation and the incident laser, and is used for the relativistic electron beam after density modulation to collide with the incident laser to generate coherent Thomson scattering and produce a light frequency comb.

[0025] The light frequency comb generation device based on coherent Thomson scattering further comprises a radiation collection system for receiving and analyzing the generated light frequency comb; the radiation collection system is arranged in the propagation direction of the relativistic electron beam after density modulation.

[0026] The application directly modulates the density of the electron beam periodically, and uses the principle of coherent Thomson scattering to interact with the laser, so that the light frequency comb with precisely controllable tooth spacing and sub-femtosecond pulse train in time domain can be realized at a lower electron beam current energy, without the need for an optical cavity, and the light frequency comb of extreme ultraviolet and soft X-ray can be generated based on a medium energy relativistic electron beam, thereby simplifying the system structure; and the required electron beam energy is lower, so that the device is more compact. In addition, by changing the seed laser wavelength or the electron beam energy, the center frequency and the tooth spacing of the light frequency comb can be flexibly adjusted. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of incoherent Thomson scattering;

[0028] Figure 2 is a schematic diagram of coherent Thomson scattering;

[0029] Figure 3 is a schematic diagram of the electron beam after density modulation for generating coherent Thomson scattering.

[0030] Figure 4 is a flowchart of the light frequency comb generation method based on coherent Thomson scattering of the application.

[0031] Figure 5is a schematic diagram of the principle of generating a density modulated electron beam based on the phase combining enhanced harmonic generation (PEHG) density modulation method.

[0032] Figure 6 is an energy phase space and density distribution diagram of the ultrashort periodic beam pulse structure generated after the 800 nm seed laser modulates the electron beam group density.

[0033] Figure 7 is a signal time domain and frequency domain diagram of the coherent radiation generated after the density modulated electron beam group collides with the incident laser to generate coherent Thomson scattering.

[0034] Figures 8A-8D is a light intensity distribution diagram of the extreme ultraviolet / soft X-ray optical frequency comb with different comb tooth spacings generated by seed lasers of different wavelengths. DETAILED DESCRIPTION

[0035] The application will be further described in detail below in combination with the drawings and examples.

[0036] The optical frequency comb generation method and device based on coherent Thomson scattering of the application are realized based on coherent Thomson scattering (CTS).

[0037] As shown in Figure 1 , the conventional Thomson scattering is realized by the collision of electrons with incident laser. In the conventional Thomson scattering, the characteristic length of the electron beam group (about 100 microns) is usually much larger than the wavelength of the scattered light generated by the Thomson scattering, which makes the pace of the scattered light inconsistent and thus usually incoherent, so it does not have the condition to obtain the optical frequency comb.

[0038] As shown in Figure 2 , when the electrons are gathered in a super-short group structure (such as a micro-bunch slice) with a longitudinal dimension comparable to or even shorter than the wavelength of the radiation light, the collision of the electron beam group with the incident laser with a super-short pulse structure will cause coherent Thomson scattering, which will cause the phase of the generated radiation light to have correlation, thereby realizing coherent radiation. Therefore, the basic idea of coherent Thomson scattering is to gather electrons in a super-short pulse structure with a longitudinal dimension comparable to or even shorter than the wavelength of the radiation light, and then collide with the incident laser.

[0039] At present, a large number of theoretical and experimental researches have been conducted on the manipulation of the longitudinal phase space of the electron beam group. In order to obtain fully coherent radiation at a shorter wavelength, various schemes of density modulation of the electron beam group to form a group structure have appeared. On this basis, as shown in Figure 3As shown, this invention utilizes various density modulation methods in the field of high-gain free electron lasers (FELs) to generate ultrashort cluster structures in low-energy electron beam clusters through periodic density modulation. When the resulting electron beam collides with the incident laser, coherent Thomson scattering occurs, and the resulting coherent radiation light is an optical frequency comb.

[0040] Therefore, the optical frequency comb generation method and apparatus based on coherent Thomson scattering of the present invention combines periodic density modulation of an electron beam with coherent Thomson scattering. It uses the periodic density-modulated electron beam as the "active medium" for generating the optical frequency comb, and performs coherent Thomson scattering of the density-modulated electron beam with a strong incident laser. The periodic spatiotemporal structure of the electron beam is directly transformed into the optical frequency comb structure of the radiation field, so that the coherent radiation output by the coherent Thomson scattering within a certain wavelength range is the optical frequency comb.

[0041] First embodiment: Optical frequency comb generation method based on coherent Thomson scattering

[0042] Based on the above principles, such as Figure 4 The optical frequency comb generation method based on coherent Thomson scattering of the present invention is used to generate optical frequency combs in the extreme ultraviolet and soft X-ray bands, and includes the following steps:

[0043] Step S1: Provide a relativistic electron beam;

[0044] Relativistic electron beams are generated using electron accelerators (such as linear accelerators). The energy of a relativistic electron beam is 50-200 MeV. In this embodiment, the relativistic electron beam is an electron beam with a central energy of 100 MeV and a relative energy divergence of approximately 0.05%.

[0045] Step S2: Periodically modulate the density of the relativistic electron beam to form an equidistant ultrashort cluster structure;

[0046] In this embodiment, the target center wavelength of the optical frequency comb is either extreme ultraviolet (EUV) or soft X-ray bands. The longitudinal dimension of the ultrashort cluster structure matches the target center wavelength of the optical frequency comb, i.e., matches the wavelengths of both the EUV and soft X-ray bands. Specifically, the root-mean-square (RMS) size of the ultrashort cluster structure is smaller than the target center wavelength of the optical frequency comb to ensure the longitudinal coherence of each electron in the cluster structure at the target center wavelength. The ultrashort cluster structure is also called a micro-bundle slice.

[0047] The density modulation is achieved by using a seed laser, which is preferably a free electron laser, or other lasers such as commercial lasers. The free electron laser has a tunable target central wavelength, and a more fixed synchronization relationship between the repetition frequency and the time structure and the electron beam, and is more suitable for density modulation of the electron beam.

[0048] In this embodiment, the method of density modulation can be a phase-merged enhanced harmonic generation (PEHG) density modulation method. As shown in Figure 5 The density modulator used in the phase-merged enhanced harmonic generation (PEHG) density modulation method includes at least one undulator 11 (such as a transverse gradient undulator) and one buncher 12 (such as a quadrupole magnet group). The undulator 11 receives seed laser from a seed laser (for example, a titanium sapphire laser with a wavelength of 800 nm) and an electron beam from an electron accelerator to modulate the energy of the electron beam and form a dispersive electron beam. The buncher 12 converts the dispersive electron beam into an electron beam with periodic density modulation, and forms a plurality of equally spaced ultrashort bunch structures in the longitudinal direction of the electron beam.

[0049] In this embodiment, the above-mentioned relativistic electron beam is modulated by the PEHG density modulation method using a seed laser with a wavelength of 800 nm. As shown in Figure 6 The modulated relativistic electron beam forms about 10 cycles of equally spaced ultrashort bunch structures with a slice spacing of 800 nm in the longitudinal direction, and the bunching factor at the target radiation wavelength (such as 10 nm) is higher than 0.05.

[0050] In other embodiments, the method of density modulation can be other methods of achieving density modulation of the electron beam, as long as it can produce ultrashort bunch structures.

[0051] Step S3: Colliding the density-modulated relativistic electron beam with an incident laser beam to produce a coherent optical frequency comb through coherent Thomson scattering.

[0052] Each ultrashort bunch structure undergoes Thomson scattering in the laser field. Since all ultrashort bunch structures have the same internal structure (coherent radiation) and act on the laser in a fixed time sequence, the coherent radiation obtained by scattering of all ultrashort bunch structures is naturally superimposed in the time domain to form an equally spaced ultrashort pulse train, and in the frequency domain, it exhibits an equally spaced optical frequency comb.

[0053] In this embodiment, the collision is preferably a head-to-head collision with a collision angle of 180° to obtain the maximum light intensity during scattering.

[0054] In other embodiments, the collision angle can also be other angles, and the collision angle does not have to be 180 degrees for head-on collision. When the electron energy and the target center wavelength of the optical frequency comb are selected, different wavelengths of incident laser can be used to collide with electrons of a specified energy at different incident angles to achieve the required target center wavelength of the scattered radiation. The collision angle is determined according to the wavelength of the incident laser and the target center wavelength of the optical frequency comb. Within a certain wavelength range, shorter wavelength incident laser (relative to the wavelength of the incident laser in the head-on collision mode at 180°) incident at a collision angle smaller than 180° can be equivalent to incident laser of equivalent wavelength at a collision angle of 180°. The calculation formula of the equivalent wavelength of the incident laser at a collision angle of 180° is:

[0055]

[0056] wherein, is the equivalent wavelength of the incident laser, is the average beta factor of the relativistic electron, which is generally taken as 1, is the center wavelength of the incident laser, is the collision angle between the incident laser and the electron propagation direction.

[0057] Taking an electron beam energy of 100 MeV and a target center wavelength of the optical frequency comb of 10 nm as an example, the wavelength range of the incident laser is about 10 um~1.65 mm.

[0058] The parameters of the incident laser can be changed according to the energy of the electron beam, the spectral width of the optical frequency comb, and the collision angle. Among them, the wavelength of the incident laser is preferably in the terahertz band (i.e., long wavelength); the pulse width of the incident laser is preferably 2~10 times the center wavelength of the incident laser (i.e., short pulse width, containing only a few center wavelengths), which makes the spectrum of the optical frequency comb wider and has more comb teeth; the repetition frequency of the incident laser matches the repetition frequency of the relativistic electron beam. The peak intensity a (dimensionless intensity of laser) of the incident laser is close to 1 to ensure the high brightness of the scattered pulse. The incident laser is preferably a few-cycle laser, and is preferably linearly polarized Gaussian laser. In this embodiment, the incident laser is a linearly polarized terahertz incident laser with a wavelength of 1.42 mm and a pulse root mean square length of about 6 mm.

[0059] The spectrometer and the detector are placed in the far field (θ=0°) of the electron beam motion direction to receive the backscattered coherent radiation. As shown in Figure 7As shown, the detected scattered coherent radiation has a periodic sub-femtosecond temporal structure, and the corresponding time-domain signal is a series of sub-femtosecond pulse trains with a pulse interval of about 2.67 fs and a pulse width of about 0.3 fs. The central wavelength of the radiation is about 10 nm (photon energy 124 eV). Its spectrum presents a clear optical comb structure, and the interval between adjacent combs is 1.55 eV, which is exactly equal to the photon energy of the 800 nm seed laser. About 7 combs can be seen within the full width at half maximum of the spectrum.

[0060] The radiation spectrum of the extreme ultraviolet / soft X-ray optical frequency comb with different comb tooth intervals generated by seed lasers of different wavelengths is shown in FIG. 2, wherein, Figures 8A-8D Figure 8A The radiation spectrum of a single electron without modulation is shown in FIG. 2a, Figure 8B The case of a seed laser with a wavelength of 800 nm is shown in FIG. 2b, Figure 8C The case of a seed laser with a wavelength of 400 nm is shown in FIG. 2c, Figure 8B The case of a seed laser with a wavelength of 200 nm is shown in FIG. 2d. Figures 8A-8D It can be seen that the comb tooth interval of the optical frequency comb is determined by the interval of the super-short group cluster structure. The density modulation is realized by the seed laser, and therefore, the comb tooth interval Δω of the frequency comb is determined by the frequency ω of the seed laser seed and is independent of the electron beam energy.

[0061] Second embodiment: optical frequency comb generation device based on coherent Thomson scattering

[0062] Based on the above-mentioned optical frequency comb generation method based on coherent Thomson scattering, the realized optical frequency comb generation device based on coherent Thomson scattering specifically comprises the following structure:

[0063] An electron beam generation and modulation system is used to generate a relativistic electron beam and periodically modulate the density of the relativistic electron beam to form equal-interval super-short group cluster structures;

[0064] In this embodiment, the electron beam generation and modulation system includes an electron accelerator (such as a linear accelerator, used to generate an electron beam with an energy of 50-200 MeV) and a density modulator based on the principle of phase-merging enhanced harmonic generation (PEHG). The density modulator used in the phase-merging enhanced harmonic generation (PEHG) density modulation method includes at least one undulator 11 and one buncher 12 (such as a quadrupole magnet group). The undulator 11 receives seed laser from a seed laser (for example, a titanium sapphire laser with a wavelength of 800 nm) and electron beam from the electron accelerator to modulate the energy of the electron beam. The buncher 12 converts the energy-modulated electron beam into a periodic density modulation to form a plurality of equal-interval super-short group cluster structures in the longitudinal direction of the electron beam.

[0065] ​A scattered laser system for providing incident laser colliding with a relativistic electron beam;

[0066] The wavelength of the incident laser is preferably in the terahertz band (i.e., long wavelength), and the pulse width of the incident laser is preferably 2-20 times the wavelength (i.e., short pulse width), so that the spectrum of the optical frequency comb is wider and has more comb teeth; in this embodiment, the incident laser is linearly polarized Gaussian incident laser with long wavelength (e.g., terahertz band, wavelength 1.42 mm), and the normalized vector potential a0 is close to or greater than 1.

[0067] The interaction region is located in the propagation direction of the density-modulated relativistic electron beam and the incident laser, and is used for the collision between the density-modulated relativistic electron beam and the incident laser to produce the optical frequency comb through coherent Thomson scattering.

[0068] In addition, the optical frequency comb generation device based on coherent Thomson scattering can also include a radiation collection system for receiving and analyzing the generated optical frequency comb. Preferably, the radiation collection system is arranged at the far end (θ=0°) of the propagation direction of the density-modulated relativistic electron beam to receive and analyze the backscattered optical frequency comb.

[0069] The present application directly modulates the electron beam periodically, and uses the principle of coherent Thomson scattering to interact with the laser, so that the optical frequency comb with precisely controllable comb tooth spacing and sub-femtosecond pulse train in time domain can be realized at a lower electron beam energy, without the need for an optical cavity, and the extreme ultraviolet and soft X-ray band optical frequency comb can be generated based on a medium-energy relativistic electron beam, thus simplifying the system structure; and the required electron beam energy is lower, so that the device is more compact. In addition, by changing the seed laser wavelength or the electron beam energy, the center frequency and comb tooth spacing of the optical frequency comb can be flexibly adjusted.

[0070] Compared with the prior art, the present application has the following advantages:

[0071] Cavity-free mode locking: completely free from the dependence on the optical resonant cavity, the frequency locking is directly realized through the periodic structure of the electron beam, thus simplifying the system structure and reducing the technical complexity.

[0072] Compact and tunable: the required electron beam energy is relatively low (~100 MeV), and the device is relatively small in size. By changing the seed laser wavelength (λ seed ) or the electron beam energy (γ), the center frequency and comb tooth spacing (Δω=ω seed ) of the optical frequency comb can be flexibly adjusted.

[0073] High temporal and spatial characteristics: the generated optical frequency comb corresponds to a string of ultrashort pulses with stable interval and sub-femtosecond (~0.3 fs) pulse width in time domain, and has extremely high frequency accuracy and stability.

[0074] High efficiency and high coherence: based on coherent Thomson scattering, the electron radiation within each micro-bunch slice is coherent superposition, the intensity is proportional to the square of the number of electrons within the slice, which significantly improves the intensity and brightness of the scattered light.

[0075] The above merely describes the preferred embodiments of the present application, and is not intended to limit the scope of the present application. The above-described embodiments of the present application can be variously changed. Any simple, equivalent changes and modifications made according to the content of the claims and the specification of the present application are intended to fall within the scope of the present application. The present application is not described in detail, and is conventional technical content.

Claims

1. A method for optical frequency comb generation based on coherent Thomson scattering, characterized in that, The application relates to a method for generating an optical frequency comb, comprising the following steps: S1: providing a relativistic electron beam; S2: periodically modulating the density of the relativistic electron beam to form an equal-interval super-short group cluster structure; S3: colliding the density-modulated relativistic electron beam with an incident laser beam to generate the optical frequency comb through coherent Thomson scattering.

2. The method of claim 1, wherein the method is implemented in a coherent Thomson scattering based optical frequency comb generation system. The target central wavelength of the optical frequency comb is one of the extreme ultraviolet and soft X-ray wave bands, and the longitudinal size of the super-short group cluster structure matches the target central wavelength of the optical frequency comb.

3. The method of claim 1, wherein the method further comprises: The density modulation is realized by using a seed laser.

4. The method of claim 3, wherein the coherent Thomson scattering is generated by a laser. The seed laser is a free electron laser.

5. The method of claim 3, wherein the coherent Thomson scattering is generated by a laser. The density modulation method is a phase-combined enhanced harmonic generation density modulation method.

6. The method of claim 3, wherein the coherent Thomson scattering is generated by a laser. The comb tooth pitch of the optical frequency comb is determined by the frequency of the seed laser.

7. The method of claim 1, wherein the method is implemented in a coherent Thomson scattering based optical frequency comb generation system. The collision angle of the collision is determined according to the wavelength of the incident laser and the target central wavelength of the optical frequency comb; when the collision angle is less than 180 DEG, the equivalent wavelength of the incident laser under the equivalent collision included angle of 180 DEG is: ， wherein, is the equivalent wavelength of the incident laser, is the average beta factor of the relativistic electrons, is the center wavelength of the incident laser, is the collision angle between the incident laser and the electron propagation direction.

8. The method of claim 1, wherein the method is implemented in a coherent Thomson scattering based optical frequency comb generation system. The wavelength of the incident laser is in the terahertz wave band, the pulse width of the incident laser is 2-10 times the wavelength of the incident laser, and the repetition frequency of the incident laser matches the repetition frequency of the relativistic electron beam.

9. A coherent Thomson scattering based optical frequency comb generation device, characterized in that, The application also relates to an optical frequency comb generation device, comprising: an electron beam generation and modulation system for generating a relativistic electron beam and periodically modulating the density of the relativistic electron beam to form an equal-interval super-short group cluster structure; a scattering laser system for providing an incident laser beam for colliding with the relativistic electron beam; an interaction region located in the propagation direction of the density-modulated relativistic electron beam and the incident laser beam, for the density-modulated relativistic electron beam to collide with the incident laser beam to generate the optical frequency comb through coherent Thomson scattering.

10. The coherent Thomson scattering based optical frequency comb generator of claim 9, wherein, The device also comprises a radiation collection system for receiving and analyzing the generated optical frequency comb; the radiation collection system is arranged in the propagation direction of the density-modulated relativistic electron beam.

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