Method and apparatus for generating optical frequency combs based on coherent Thomson scattering

Abstract

This invention provides a method and apparatus for generating an optical frequency comb based on coherent Thomson scattering. The method includes: providing a relativistic electron beam; periodically density modulating the relativistic electron beam to form an equally spaced ultrashort cluster structure; and colliding the density-modulated relativistic electron beam with an incident laser beam to induce coherent Thomson scattering, thereby generating the optical frequency comb. This invention, by directly periodically density modulating the electron beam and utilizing the principle of coherent Thomson scattering to interact with the laser, can achieve a precisely controllable optical frequency comb with a sub-femtosecond pulse train in the time domain at relatively low electron beam energy. It eliminates the need for an optical cavity and can generate optical frequency combs for extreme ultraviolet and soft X-rays based on a medium-energy relativistic electron beam, simplifying the system structure. Furthermore, the lower required electron beam energy makes the apparatus more compact.

Description

Technical Field

[0001] This invention relates to the field of photon source and particle beam application technology, and particularly to a method and apparatus for generating an optical frequency comb based on coherent Thomson scattering, wherein the optical frequency comb is located in the extreme ultraviolet (EUV) and soft X-ray bands. Background Technology

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

[0003] Optical frequency combs, as precise optical frequency measuring tools, can establish a close relationship between microwave frequencies and light wave frequencies, and have been widely used in scientific research fields such as timing, precision spectroscopy, and fundamental physics. Optical frequency combs generated using traditional mode-locked lasers, electro-optic modulators, and other methods typically cover a wavelength range from the ultraviolet band of hundreds of nm to the infrared band of several μm. If the operating range of optical frequency combs can be further extended to shorter wavelengths, from vacuum ultraviolet (VUV) to extreme ultraviolet (EUV or XUV) and even to the X-ray band, ultra-high precision detection of atomic and molecular structures can be achieved; the applicability boundaries of quantum electrodynamics (QED) theory can be explored, and fundamental physical constants can be accurately determined; the application of VUV optical comb technology to the precise measurement of thorium-229 nuclear transition spectra will greatly promote the establishment of a new type of optical clock—the nuclear optical clock. However, this has always been a significant challenge for the scientific community.

[0004] Traditional VUV / XUV optical frequency combs based on lasers are mainly obtained by generating high-order harmonics through the interaction of cavity-enhanced incident lasers with inert gases. In recent years, a new generation of X-ray coherent sources, represented by free-electron laser devices, has emerged, providing light with higher brightness, better coherence, and shorter pulses. This meets the current research demands for ultra-high spatial and temporal resolution, ultra-short pulses, and ultra-high brightness, playing a nearly irreplaceable role in numerous basic and applied research fields. In particular, high-order harmonic free-electron laser devices based on external seed modulation methods can not only obtain temporally and spatially fully coherent and wavelength-tunable high-brightness radiation in the EUV and soft X-ray bands, but also possess the potential to generate short-wavelength optical frequency combs through mode-locking due to their periodic temporal structure. Several theoretical and experimental studies have investigated and verified the feasibility of generating short-wavelength optical frequency combs. However, the aforementioned accelerator-driven light source devices typically require high-energy electron beams to generate short-wavelength light, resulting in large-scale devices and substantial investments. Despite their powerful performance, the high construction costs limit the number of such large scientific facilities, which cannot fully meet the ever-increasing user demand. Therefore, there is an urgent need to find ways to reduce the size and cost of similar facilities.

[0005] The Thomson scattering source, also known as the inverse Compton scattering source, uses the interaction of a high-brightness relativistic electron beam and a high-power incident laser to produce high-brightness, short-wavelength quasi-monoenergetic scattered light in the direction of the electron beam's motion. The parameters of the generated scattered light pulse are determined by the parameters of the relativistic electron beam and the incident laser. For an electron beam with a relativistic energy factor of γ and a wavelength of λ... L When incident laser light undergoes backscattering, a wavelength of approximately λ can be generated due to the Doppler frequency shift. L / 4γ 2 The scattered light. Compare with the free electron laser resonance relationship λ. R ~ λ u / 2γ 2 , λ R λ is the wavelength of a free-electron laser. u The undulator period length is given by the laser wavelength λ used for Thomson scattering. L Typically much smaller than the oscillator period length λ u Therefore, in Thomson scattering, the beam energy required to obtain radiation of the same wavelength is several orders of magnitude lower than that of synchrotron radiation or free electron lasers, which can greatly reduce the size and cost of the device.

[0006] However, in traditional Thomson scattering, the characteristic length of the electron beam (about 100 micrometers) is usually much larger than the wavelength of the scattered light produced by Thomson scattering. This makes the scattered light inconsistent and therefore usually lacks coherence, thus failing to meet the conditions for obtaining an optical frequency comb. Summary of the Invention

[0007] The purpose of this invention is to provide a method and apparatus for generating optical frequency combs based on coherent Thomson scattering, so as to generate optical frequency combs in the extreme ultraviolet and soft X-ray bands, and the apparatus is compact.

[0008] To achieve the above objectives, the present invention provides a method for generating an optical frequency comb based on coherent Thomson scattering, comprising:

[0009] S1: Provides a relativistic electron beam;

[0010] S2: Periodically modulate the density of the relativistic electron beam to form an equidistant ultrashort cluster structure;

[0011] S3: The density-modulated relativistic electron beam collides with an incident laser beam, causing coherent Thomson scattering and generating an optical frequency comb.

[0012] The target center wavelength of the optical frequency comb is one of the extreme ultraviolet and soft X-ray bands, and the longitudinal dimension of the ultrashort cluster structure matches the target center wavelength of the optical frequency comb.

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

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

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

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

[0017] The collision angle is determined based on 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 at a collision angle of 180° is:

[0018] ,

[0019] in, The equivalent wavelength of the incident laser is λ. The average beta factor of relativistic electrons, The center wavelength of the incident laser. The angle between the incident laser and the electron propagation direction is the collision angle.

[0020] The wavelength of the incident laser is in the terahertz band, the pulse width of the incident laser is 2 to 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] On the other hand, the present invention provides an optical frequency comb generating device based on coherent Thomson scattering, comprising:

[0022] An electron beam generation and modulation system is used to generate a relativistic electron beam and to periodically modulate the density of the relativistic electron beam to form an equidistant ultrashort cluster structure.

[0023] A scattered laser system used to provide incident laser light that collides with a relativistic electron beam;

[0024] The interaction region, located in the propagation direction of the density-modulated relativistic electron beam and the incident laser, is used to allow the density-modulated relativistic electron beam to collide with the incident laser, resulting in coherent Thomson scattering and generating an optical frequency comb.

[0025] The optical frequency comb generating device based on coherent Thomson scattering further includes a radiation collection system for receiving and analyzing the generated optical frequency comb; the radiation collection system is positioned in the propagation direction of the density-modulated relativistic electron beam.

[0026] This invention achieves a precisely controllable optical frequency comb with sub-femtosecond pulse trains in the time domain by directly periodically modulating the density of an electron beam and utilizing the principle of coherent Thomson scattering to interact with a laser. This requires relatively low electron beam energy and eliminates the need for an optical cavity. It generates extreme ultraviolet and soft X-ray optical frequency combs based on medium-energy relativistic electron beams, simplifying the system structure. Furthermore, the lower required electron beam energy makes the device more compact. In addition, the center frequency and tooth spacing of the optical frequency comb can be flexibly adjusted by changing the seed laser wavelength or electron beam energy. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the principle of incoherent Thomson scattering.

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

[0029] Figure 3 This is a schematic diagram illustrating the principle of using a density-modulated electron beam to generate coherent Thomson scattering.

[0030] Figure 4 This is a flowchart of the optical frequency comb generation method based on coherent Thomson scattering of the present invention.

[0031] Figure 5This is 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 This is a diagram showing the energy phase space and density distribution of the ultrashort periodic beam pulse structure generated by the electron beam density modulation of an 800nm ​​seed laser.

[0033] Figure 7 It is the time-domain and frequency-domain diagram of the coherent radiation signal generated after the density-modulated electron beam undergoes coherent Thomson scattering with the incident laser.

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

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0036] The optical frequency comb generation method and apparatus based on coherent Thomson scattering of the present invention are based on coherent Thomson scattering (CTS).

[0037] like Figure 1 As shown, traditional Thomson scattering is achieved by the collision of electrons with the incident laser. In traditional Thomson scattering, the characteristic length of the electron beam (about 100 micrometers) is usually much larger than the wavelength of the scattered light produced by Thomson scattering. This makes the scattered light inconsistent and therefore usually lacks coherence, thus failing to meet the conditions for obtaining an optical frequency comb.

[0038] like Figure 2 As shown, when electrons are concentrated in an ultrashort cluster structure (such as a micro-slice) with a longitudinal scale comparable to or even shorter than the wavelength of the emitted light, coherent Thomson scattering occurs when the electron beam with the ultrashort pulse structure collides with the incident laser. This results in a phase correlation in the generated emitted light, thus achieving coherent radiation. Therefore, the basic idea behind coherent Thomson scattering is to concentrate electrons in an ultrashort pulse structure with a longitudinal scale comparable to or even shorter than the wavelength of the emitted light through various means, and then collide with the incident laser.

[0039] Currently, extensive theoretical and experimental research has been conducted on the manipulation of the longitudinal phase space of electron beam clusters. To obtain fully coherent radiation at shorter wavelengths, various schemes for density modulation of electron beam clusters to form clustered structures have emerged. Based on this, such as... 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] Density modulation is achieved using a seed laser, preferably a free-electron laser, but other lasers such as commercial lasers can also be used. The target center wavelength of a free-electron laser is tunable, and its repetition frequency and time structure have a more fixed synchronization relationship with the electron beam, making it more suitable for electron beam density modulation.

[0048] In this embodiment, the density modulation method can be the phase-combining enhanced harmonic generation (PEHG) density modulation method. For example... Figure 5 As shown, the density modulator used in the Phase-Combined Enhanced Harmonic Generation (PEHG) density modulation method includes at least one undulator 11 (such as a transverse gradient undulator) and one beam mixer 12 (such as a quadrupole magnet array). The undulator 11 receives a seed laser from a seed laser (e.g., an 800 nm Ti:sapphire laser) and an electron beam from an electron accelerator to modulate the energy of the electron beam, forming a dispersive electron beam. The beam mixer 12 converts the dispersive electron beam into a periodically density-modulated electron beam, forming multiple equally spaced ultrashort clusters along the longitudinal direction of the electron beam.

[0049] In this embodiment, a seed laser with a wavelength of 800 nm is used to modulate the relativistic electron beam using the PEHG density modulation method. For example... Figure 6 As shown, the modulated relativistic electron beam forms an ultrashort cluster structure with approximately 10 periods in the longitudinal direction and a slice spacing of 800 nm, with a focusing factor higher than 0.05 at the target radiation wavelength (e.g., 10 nm).

[0050] In other embodiments, the density modulation method can be any other method for achieving electron beam density modulation, as long as it can produce an ultrashort clustering mechanism.

[0051] Step S3: The density-modulated relativistic electron beam collides with an incident laser beam, causing coherent Thomson scattering and generating an optical frequency comb.

[0052] Each ultrashort cluster structure undergoes Thomson scattering in the laser field. Since all ultrashort cluster structures have the same internal structure (coherent radiation) and interact with the laser in a fixed time sequence, the coherent radiation they scatter naturally superimposes in the time domain to form equally spaced ultrashort pulse trains, which in the frequency domain appear as equally spaced optical frequency combs.

[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. The collision angle does not have to be a 180-degree head-to-head collision. When the electron energy and the target center wavelength of the optical frequency comb are selected, incident lasers of different wavelengths can be used at different incident angles to collide with electrons of a specified energy to achieve the desired scattered radiation at the target center wavelength. The collision angle is determined based on the wavelength of the incident laser and the target center wavelength of the optical frequency comb. Within a certain wavelength range, a shorter wavelength incident laser (relative to the wavelength of the incident laser in a 180° head-to-head collision mode) incident at a collision angle of less than 180° can be equivalent to an incident laser of equivalent wavelength at a collision angle of 180°. The formula for calculating the equivalent wavelength of the incident laser at a collision angle of 180° is as follows:

[0055]

[0056] in, The equivalent wavelength of the incident laser is λ. This is the average beta factor of the relativistic electron, typically taken as 1. The center wavelength of the incident laser. The angle between the incident laser and the electron propagation direction is the collision angle.

[0057] Taking an electron beam energy of 100 MeV and a target center wavelength of 10 nm as an example: the wavelength range of the incident laser is approximately 10 μm to 1.65 mm.

[0058] The parameters of the incident laser can be varied according to the energy of the electron beam, the spectral width of the optical frequency comb, and the collision angle. Specifically, the wavelength of the incident laser is preferably in the terahertz band (i.e., a long wavelength); the pulse width of the incident laser is preferably 2 to 10 times the center wavelength of the incident laser (i.e., a short pulse width, containing only a few center wavelengths), which results in a wider spectrum and more comb teeth in the optical frequency comb; the repetition frequency of the incident laser matches the repetition frequency of the relativistic electron beam. The peak pulse intensity α (dimensionless laser intensity) of the incident laser is close to 1 to ensure high brightness of the scattered pulse. The incident laser is preferably a few-period laser, and more preferably a 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 approximately 6 mm.

[0059] A spectrometer and detector are placed in the far field (θ=0°) of the electron beam's direction of motion to receive backscattered coherent radiation. For example... Figure 7As shown, the detected scattered coherent radiation exhibits a periodic sub-femtosecond time structure, corresponding to a time-domain signal of a series of sub-femtosecond pulses with an interval of approximately 2.67 fs and a pulse width of approximately 0.3 fs. The radiation center wavelength is approximately 10 nm (photon energy 124 eV). Its spectrum displays a clear optical frequency comb structure, with the spacing between adjacent comb teeth being 1.55 eV, precisely equal to the photon energy of an 800 nm seed laser. Approximately 7 comb teeth are visible within the full width at half maximum (FWHM) of the spectrum.

[0060] The radiation spectra of extreme ultraviolet / soft X-ray optical frequency combs with different tooth spacings generated by seed lasers of different wavelengths are shown below. Figures 8A-8D As shown, where, Figure 8A The radiation spectrum of a single electron without modulation is shown. Figure 8B The example shows a seed laser with a wavelength of 800 nm. Figure 8C The example shows a seed laser with a wavelength of 400 nm. Figure 8B The example shows a seed laser with a wavelength of 200 nm. Figures 8A-8D It can be seen that the tooth spacing of the optical frequency comb is determined by the spacing of the ultrashort clustered structures. Density modulation is achieved using a seed laser; therefore, the tooth spacing Δω of the frequency comb is determined by the frequency ω of the seed laser. seed The decision 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-described optical frequency comb generation method based on coherent Thomson scattering, the implemented optical frequency comb generation device based on coherent Thomson scattering specifically includes the following structure:

[0063] An electron beam generation and modulation system is used to generate a relativistic electron beam and to periodically modulate the density of the relativistic electron beam to form an equidistant ultrashort cluster structure.

[0064] In this embodiment, the electron beam generation and modulation system includes an electron accelerator (such as a linear accelerator for generating electron beams with energies of 50-200 MeV) and a density modulator based on the phase-combining enhanced harmonic generation (PEHG) principle. The density modulator used in the PHEG density modulation method includes at least one undulator 11 and one beam mixer 12 (such as a quadrupole magnet array). The undulator 11 receives a seed laser from a seed laser (e.g., an 800 nm Ti:sapphire laser) and an electron beam from the electron accelerator to modulate the energy of the electron beam. The beam mixer 12 converts the energy-modulated electron beam into periodic density modulation, forming multiple equally spaced ultrashort cluster structures along the longitudinal direction of the electron beam.

[0065] A scattered laser system used to provide incident laser light that collides 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 to 20 times the wavelength (i.e., short pulse width), so that the optical frequency comb has a wider spectrum and more comb teeth; in this embodiment, the wavelength of the incident laser is a long wavelength (such as the terahertz band, wavelength 1.42 mm) linearly polarized Gaussian incident laser, and its normalized vector potential a0 is close to or greater than 1.

[0067] The interaction region, located in the propagation direction of the density-modulated relativistic electron beam and the incident laser, is used to allow the density-modulated relativistic electron beam to collide with the incident laser, resulting in coherent Thomson scattering and generating an optical frequency comb.

[0068] Furthermore, the optical frequency comb generating device based on coherent Thomson scattering may also include a radiation collection system for receiving and analyzing the generated optical frequency comb. Preferably, the radiation collection system is positioned at the far end (θ=0°) in the propagation direction of the density-modulated relativistic electron beam to receive and analyze the optical frequency comb generated by backscattering.

[0069] This invention achieves a precisely controllable optical frequency comb with sub-femtosecond pulse trains in the time domain by directly periodically modulating the density of an electron beam and utilizing the principle of coherent Thomson scattering to interact with a laser. This requires relatively low electron beam energy and eliminates the need for an optical cavity. It generates optical frequency combs in the extreme ultraviolet and soft X-ray bands based on medium-energy relativistic electron beams, simplifying the system structure. Furthermore, the lower required electron beam energy makes the device more compact. In addition, the center frequency and tooth spacing of the optical frequency comb can be flexibly adjusted by changing the seed laser wavelength or electron beam energy.

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

[0071] Cavity-free mode-locking: It completely eliminates the dependence on optical resonant cavities and achieves frequency locking directly through the periodic structure of the electron beam itself, simplifying the system structure and reducing technical complexity.

[0072] Compact and tunable: The required electron beam energy is relatively low (~100 MeV), allowing for a relatively miniaturized device. This is achieved by changing the seed laser wavelength (λ). seed The center frequency and tooth spacing of the optical frequency comb can be flexibly adjusted by using either electron beam energy (γ) or electron beam energy (γ). seed ).

[0073] High spatiotemporal characteristics: The generated optical frequency comb corresponds to a series of ultrashort pulses with stable intervals and pulse widths on the order of sub-femtoseconds (~0.3 fs) in the time domain, while possessing extremely high frequency accuracy and stability.

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

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. All simple and equivalent changes and modifications made in accordance with the claims and description of this application fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are 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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