Method and system for ceps-stable multi-octave mid-infrared pulse generation

Abstract

The present application relates to a kind of mid-infrared pulse generation method and system, specifically to a kind of CEP stable multi-octave mid-infrared pulse generation method and system.The present application mainly solves the technical problems that the existing mid-infrared pulse generation method has complex structure, poor stability, needs complex frequency domain rearrangement or multi-level control.The method of the present application comprises the following steps: step 1, generating broadband drive pulse;Step 2, chirp control is carried out to broadband drive pulse;Step 3, cascade setting nonlinear crystal and carrying out cascade pulse internal difference frequency;Step 4, obtain super wideband mid-infrared output pulse.The present application pre-designs the spectrum phase of broadband drive pulse, so that it realizes the time domain coincidence of different frequency components in different positions and different crystals during the propagation process in nonlinear crystal, thereby generating complementary waveband difference frequency signal in cascade in multiple nonlinear crystals, and obtaining super wideband, carrier envelope phase stable mid-infrared pulse output.

Description

Technical Field

[0001] This invention relates to a method and system for generating mid-infrared pulses, specifically to a method and system for generating multi-octave mid-infrared pulses with CEP (carrier envelope phase) stability. Background Technology

[0002] Femtosecond and even sub-periodic mid-infrared laser pulses have significant applications in strong-field physics, attosecond science, nonlinear optics, and ultrafast electron dynamics control in materials. Especially in the generation of higher harmonics, the center wavelength of the driving optical field has a square relationship with the harmonic cutoff energy; therefore, carrier-envelope phase-stable few-period mid-infrared pulses are considered one of the key light sources for obtaining high-energy isolated attosecond pulses.

[0003] In existing technologies, the main approaches to obtaining carrier envelope phase-stable mid-infrared ultrashort pulses include optical parametric amplification (OPA) and optical parametric chirped pulse amplification (OPCPA). These OPA systems can achieve high pulse energy output, and their carrier envelope phase stability is determined by the input seed pulse. Intra-pulse difference frequency (IPF) utilizes the different frequency components within a single broadband femtosecond pulse to achieve passive carrier envelope phase stabilization without additional phase locking, thus becoming an important method for obtaining mid-infrared seed pulses. By nonlinearly broadening the near-infrared or visible femtosecond pulses and implementing IPF in a nonlinear crystal, ultrashort pulses with wavelengths in the mid-infrared band can be obtained. However, limited by the dispersion characteristics and phase-matching conditions of nonlinear crystals, the mid-infrared spectral bandwidth obtained by traditional IPF techniques is usually narrow, often covering only about one octave, making it difficult to support the generation of sub-periodic or even sub-sub-periodic mid-infrared pulses. The bandwidth limitation stems primarily from the following factors: First, significant group velocity mismatch exists between different frequency components in nonlinear crystals, causing high-frequency and low-frequency components involved in the difference frequency process to rapidly drift away in time. Second, the effective phase-matching bandwidth provided by a single nonlinear crystal is limited, failing to simultaneously cover the difference frequency process across an ultra-wide spectral range. Therefore, regardless of whether based on broadband light sources such as Ti:sapphire lasers or narrowband light sources such as picosecond lasers, the seed light bandwidth with carrier envelope phase stability is difficult to exceed a single octave. To overcome these limitations, existing technologies have attempted to employ combinations of multiple nonlinear crystals to achieve complementary phase-matching bandwidths, or to introduce frequency-domain rearrangement structures to time- and frequency-controlled broadband pulses. However, multi-crystal cascade schemes are easily limited by the time-domain walk-away effect during pump pulse propagation within the crystals in practical applications, making it difficult for the difference frequency process in different crystals to effectively coordinate, thus limiting the bandwidth expansion effect. Furthermore, while introducing a 4f optical system or intermediate compression structure can, to some extent, control the spatiotemporal overlap of different frequency components, it also significantly increases system complexity, reduces overall stability, and adversely affects the long-term stability of the carrier envelope phase. On the other hand, some solutions achieve ultra-wideband difference frequency output by introducing intermediate dispersion compensation or independent control structures between cascaded nonlinear crystals. However, such structures often cause the difference frequency signals of different bands to be separated in time and space, requiring additional coherent synthesis steps. This not only increases the complexity of the system but also limits its promotion in high-stability application scenarios.

[0004] In summary, the existing technology lacks a simple, stable, and effective intra-pulse difference frequency method that can overcome the bandwidth limitation of nonlinear crystal phase matching without complex frequency domain rearrangement or multi-level synchronous control, thereby achieving ultra-wideband, carrier envelope phase-stable mid-infrared ultrashort pulse output. Summary of the Invention

[0005] The purpose of this invention is to address the problem that existing carrier envelope phase-stable mid-infrared pulse generation schemes are difficult to overcome the bandwidth limitation of a single nonlinear crystal phase matching while maintaining system structure simplicity and stability, and often rely on complex frequency domain rearrangement or multi-level control. The invention provides a carrier envelope phase-stable multi-octave mid-infrared pulse generation method and system.

[0006] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0007] A method for generating CEP-stabilized multi-octave mid-infrared pulses, characterized by the following steps:

[0008] Step 1: Generate broadband drive pulses

[0009] Using ultrashort pulses as the initial light source, a broadband driving pulse covering the visible to near-infrared band is obtained through nonlinear spectral broadening, and the obtained broadband driving pulse contains at least one set of high-frequency components and one set of low-frequency components.

[0010] Step 2: Chirp control of the broadband drive pulse

[0011] Before the broadband driving pulse is incident on the nonlinear crystal, the chirp is determined based on the thickness of the nonlinear crystal and the group velocity walk-off between the frequency components within it. Then, the obtained broadband driving pulse is subjected to corresponding dispersion modulation based on the chirp, so that the broadband driving pulse exhibits a non-zero chirp state.

[0012] Step 3: Cascade nonlinear crystals and perform cascaded pulse difference frequency modulation.

[0013] The dispersion-modulated broadband driving pulses are sequentially incident onto two nonlinear crystals cascaded along the light propagation direction to perform cascaded pulse difference frequency conversion.

[0014] During the process of cascaded pulse intra-frequency difference, the group velocity walk-off in the nonlinear crystal is used to make the broadband driving pulses of different frequency components coincide in time at different propagation positions or in different nonlinear crystals, and the cascaded pulse intra-frequency difference is completed in the corresponding nonlinear crystal. Thus, a longer wavelength difference frequency signal is preferentially generated in the first nonlinear crystal, and a shorter wavelength difference frequency signal is generated in the second nonlinear crystal.

[0015] Step 4: Obtain the ultra-wideband mid-infrared output pulse

[0016] By spatially collinearly outputting the spectrally complementary difference frequency signals obtained from different nonlinear crystals, a mid-infrared ultrashort pulse output covering a multi-octave spectral range is obtained.

[0017] Furthermore, in step 1, the nonlinear spectral broadening methods include multi-plate nonlinear broadening, hollow fiber nonlinear broadening, and gas or solid medium filamentation broadening.

[0018] Furthermore, in step 2, the dispersion control method includes chirped mirror reflection, dispersion compensation prism pair, and grating dispersion modulation device.

[0019] Furthermore, in step 2, the dispersion modulation is specifically negative group delay dispersion, so that the broadband driving pulse of the high-frequency component leads the broadband driving pulse of the low-frequency component in time, thereby forming an initial temporal distribution of broadband driving pulses of different frequency components in the time domain.

[0020] Furthermore, in step 3, the material type, thickness, and cutting angle of each nonlinear crystal correspond to different phase-matching bands;

[0021] The nonlinear crystal is a crystal material with second-order nonlinear effects, including barium β-borate, bismuth borate, lithium niobate, or magnesium oxide-doped lithium niobate crystals.

[0022] Furthermore, in step 3, the number of nonlinear crystals is two; in the two-crystal cascaded difference frequency mode composed of two nonlinear crystals, the broadband driving light is divided into two pump components. , and signal light components ,and ;

[0023] Define the group delay between different frequency components as (Used to quantitatively express chirp quantity), the thickness of the first nonlinear crystal is L1, the thickness of the second nonlinear crystal is L2, and the group velocity walk-off is... ;

[0024] Then the amount of chirping The thickness L1 and group velocity of the first nonlinear crystal are diverging. The following conditions must be met:

[0025] ;

[0026] The thickness L2 and chirp of the second nonlinear crystal and the group move away quickly The following conditions must be met:

[0027] .

[0028] Meanwhile, the present invention also provides a CEP-stabilized multi-octave mid-infrared pulse generation system for realizing the aforementioned CEP-stabilized multi-octave mid-infrared pulse generation method, which is characterized by:

[0029] It includes an ultrashort pulse laser source module, a spectral broadening module, a dispersion modulation module, a cascaded pulse intra-pulse difference frequency module, and an output and separation module;

[0030] The ultrashort pulse laser source module is used to output ultrashort pulses;

[0031] The spectral broadening module is connected to the ultrashort pulse laser source module and is used to generate broadband driving pulses;

[0032] The dispersion modulation module is located in the output optical path of the spectral broadening module and is used to apply predetermined dispersion modulation to the broadband driving pulse.

[0033] The cascaded pulse intra-frequency difference module includes two nonlinear crystals cascaded along the light propagation direction, used to realize cascaded pulse intra-frequency difference based on the group velocity walk-off effect;

[0034] The output and separation module is set in the output optical path of the cascaded pulse difference frequency module. By filtering out the residual driving pulse after the cascaded pulse difference frequency, it ensures that the spectrally complementary difference frequency signals obtained from different nonlinear crystals can be directly collinearly output in space, thereby obtaining mid-infrared ultrashort pulse output covering a multi-octave spectrum range.

[0035] Furthermore, the ultrashort pulse laser source module is a femtosecond laser or a picosecond laser.

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] 1. By pre-designing the spectral phase of the broadband driving pulse (using chirped mirrors, bulk materials, etc.), the group velocity walk-off effect is used to achieve temporal overlap of different frequency components in different positions and crystals during propagation in the nonlinear crystal. This generates complementary band difference frequency signals in multiple nonlinear crystals in a cascaded manner, ultimately obtaining an ultra-wideband, carrier envelope phase-stable mid-infrared pulse output.

[0038] 2. This scheme overcomes the limitations of group velocity walk-off and crystal phase-matching bandwidth faced by traditional intra-pulse difference frequency schemes, enabling the generation of mid-infrared femtosecond pulses with carrier envelope phase stability exceeding octave bands. Furthermore, this method is applicable to various light sources such as Ti:Sapphire femtosecond lasers and Yb:YAG picosecond lasers. By cascading two nonlinear crystals that meet design requirements and optimizing the driving pulse chirp, the spectrum of the difference frequency pulse is broadened to the phase-matching bandwidth range of multiple crystals. This invention does not suppress or eliminate group velocity walk-off, but rather achieves controlled time coincidence conditions for group velocity walk-off at different propagation positions through the synergistic design of the driving pulse chirp and crystal parameters, thereby realizing effective difference frequencies for different spectral components in the cascaded nonlinear crystals. This invention has a stable and simple structure, and the method has good universality for various laser light sources. Attached Figure Description

[0039] Figure 1 This is a flowchart illustrating Embodiment 1 of the present invention.

[0040] Figure 2 This is a physical demonstration diagram of Embodiment 1 of the present invention;

[0041] Figure 3 This is a schematic diagram of the optical path in Embodiment 2 of the present invention;

[0042] Figure 4 This is a schematic diagram of the optical path in Embodiment 3 of the present invention. Detailed Implementation

[0043] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0044] Example 1

[0045] See Figure 1 This embodiment provides a CEP-stabilized multi-octave mid-infrared pulse generation method, which specifically includes the following steps:

[0046] Step 1: Generate broadband drive pulses

[0047] Using ultrashort pulses as the initial light source, a broadband driving pulse covering the visible to near-infrared band is obtained through nonlinear spectral broadening. Specifically, the aforementioned nonlinear spectral broadening methods include, but are not limited to, multi-plate nonlinear broadening, hollow-core fiber nonlinear broadening, and gas or solid medium filament broadening. The obtained broadband driving pulse contains at least one set of high-frequency components and one set of low-frequency components, both of which can be used for subsequent cascaded pulse intra-pulse frequency difference processes.

[0048] Step 2: Chirp control of the broadband drive pulse

[0049] Before the broadband driving pulse is incident on the nonlinear crystal, the chirp is determined based on the thickness of the nonlinear crystal and the group velocity walk-off between its frequency components. Then, based on the chirp, a corresponding dispersion modulation is applied to the broadband driving pulse obtained in step 1, causing the broadband driving pulse to exhibit a non-zero chirp state. Preferably, the dispersion modulation is specifically negative group delay dispersion, so that the high-frequency component broadband driving pulse leads the low-frequency component broadband driving pulse in time, thereby forming an initial timing distribution of broadband driving pulses with different frequency components in the time domain. The aforementioned dispersion modulation methods include, but are not limited to, chirped mirror reflection, dispersion-compensating prism pairs, and grating dispersion modulation devices. Through the above dispersion modulation, the relative time delay between different frequency components changes continuously with the propagation distance as the broadband driving pulse propagates in the nonlinear crystal.

[0050] Preferably, the specific chirp amount needs to be determined based on the specific experimental design, taking into account both the group velocity walk-off between different frequency components within the nonlinear crystal and the crystal thickness. The selection principles for chirp amount and crystal thickness are given below:

[0051] In the cascaded difference frequency mode of two crystals, the broadband drive pulse is divided into two pump components. , ( ), and signal light components ,and , corresponding to Figure 2 And it is expected to obtain frequency component coverage. to CEP-stabilized idler frequency optical pulses.

[0052] To ensure and sequentially with If the time domains coincide, then the group delay between different frequency components under this condition is... (Used to quantitatively express chirp amount) and the thickness of the first crystal L1, group velocity walk-off ( ) should meet The thickness L2 of the second crystal should satisfy the following conditions in relation to the chirp and group velocity walk-off: .

[0053] The design of the difference frequency process for more cascaded crystals follows the same principle.

[0054] Step 3: Cascade nonlinear crystals and perform cascaded pulse difference frequency modulation.

[0055] A broadband driving pulse, after dispersion modulation, is sequentially incident onto two cascaded nonlinear crystals arranged along the light propagation direction for cascaded intra-pulse difference frequency conversion. The different materials, thicknesses, and cutting angles of the nonlinear crystals correspond to different phase-matching bands. Specifically, during the nonlinear frequency conversion process, the propagation phase velocities of different frequency light waves within the nonlinear crystals differ. To ensure the continuous and effective accumulation of the difference frequency signal during propagation, the momentum conservation relationship between the two driving frequency components involved in the difference frequency conversion and the generated difference frequency wave must be satisfied, i.e., the phase-matching condition must be met. Due to their different dispersion characteristics, different nonlinear crystal materials have different frequency combinations that can satisfy the phase-matching condition; simultaneously, by adjusting the crystal's cutting angle and thickness, the crystal can achieve higher difference frequency conversion efficiency within a specific band. Therefore, nonlinear crystals with different materials and parameter settings correspond to different effective phase-matching bands.

[0056] The thickness of the selected nonlinear crystal is determined by its walk-off characteristics and operating wavelength. Nonlinear crystals include, but are not limited to: barium β-borate (BBO); bismuth borate (BIBO); lithium niobate or magnesium oxide-doped lithium niobate crystals; and other crystal materials exhibiting second-order nonlinear effects.

[0057] Step 4: Utilize the group velocity walk-off effect to achieve automatic time-domain matching.

[0058] During the propagation of a broadband driving pulse in a nonlinear crystal, different frequency components undergo relative temporal position changes due to their different group velocities, causing the low-frequency components to gradually catch up with the high-frequency components. By rationally designing the chirp of the driving pulse, the thickness of each nonlinear crystal, and the arrangement order of the nonlinear crystals, the group velocity walk-off effect within the nonlinear crystals is utilized to achieve time overlap between different frequency components at different propagation positions or in different nonlinear crystals, and to complete the difference frequency generation within the corresponding crystal. Thus, a longer wavelength difference frequency signal is preferentially generated in the first nonlinear crystal, and a shorter wavelength difference frequency signal is generated in subsequent nonlinear crystals, thereby achieving the cascading of multiple difference frequency processes.

[0059] Step 5: Obtain the ultra-wideband mid-infrared output pulse

[0060] Through the above-described cascaded pulse intra-frequency difference process, spectrally complementary difference frequency signals are obtained in different nonlinear crystals. The spectrally complementary difference frequency signals obtained from different nonlinear crystals are output collinearly in space, ultimately obtaining a mid-infrared ultrashort pulse output covering a multi-octave spectrum range. Moreover, this output pulse inherits the passively stable carrier envelope phase characteristic of the cascaded pulse intra-frequency difference technology.

[0061] Example 2

[0062] Optical systems based on Ti:sapphire femtosecond lasers

[0063] See Figure 3 In this embodiment, a Ti:sapphire femtosecond laser is used as the ultrashort pulse source to provide high peak power and broadband femtosecond pulses. The femtosecond pulses output by the laser are passed through a spectral broadening module composed of six 100-micron-thick quartz sheets placed at Brewster angles to generate broadband driving pulses covering the visible to near-infrared bands. The broadband driving pulses then enter a dispersion control module, where a predetermined amount of negative group delay dispersion is introduced through a broadband chirped mirror with negative chirp, causing different frequency components to form a specific chirped distribution in time. The amount of dispersion can be finely controlled by a wedge. The chirped driving pulses are focused and sequentially incident on cascaded nonlinear crystals. For example, to obtain near-infrared difference frequency light, a bismuth borate crystal can be selected; to generate mid-infrared difference frequency light, a magnesium oxide-doped lithium niobate crystal can be selected. The group velocity mismatch effect is used in each crystal to realize the difference frequency process within the cascaded pulses, thereby generating complementary mid-infrared difference frequency signals in different crystals. The angle of the difference frequency crystal is determined by its phase matching characteristics. For example, under the phase matching conditions corresponding to this wavelength band, a bismuth borate crystal with a phase matching angle of 60° (xz plane) corresponds to a near-infrared difference frequency signal of 1~2.5 micrometers; a magnesium oxide-doped lithium niobate crystal with a phase matching angle of 45.7° corresponds to a mid-infrared difference frequency signal of 2.5~4 micrometers. Its crystal thickness is determined by the group delay walk-off, which is typically on the order of several hundred micrometers.

[0064] Ultimately, the difference frequency signals are directly output in a collinear manner to obtain ultra-wideband, carrier envelope phase-stable mid-infrared ultrashort pulses with a spectral coverage of 1-4 micrometers.

[0065] Example 3

[0066] Optical systems based on narrowband picosecond lasers

[0067] See Figure 4 In this embodiment, a picosecond laser based on a ytterbium-doped gain medium is used as the light source. The initial pulse spectrum of the picosecond laser output is relatively narrow, but it has high average power and good stability.

[0068] The picosecond pulse is first broadened by a nonlinear spectral broadening module to obtain a broadband driving pulse that meets the difference frequency requirements of the cascaded pulses. For a one-micron narrowband picosecond pulse, a YAG crystal can be used for nonlinear broadening. Subsequently, the broadband driving pulse is dispersion-tuned to ensure it exhibits a pre-designed chirped state before entering the cascaded nonlinear crystal. When it is necessary to increase the energy of the supercontinuum after broadening, an energy amplification stage can be optionally set.

[0069] During the propagation of the chirped broadband driving pulse in a cascaded nonlinear crystal, different frequency components satisfy phase matching in different crystals and complete difference frequency conversion in the corresponding crystals, thereby generating difference frequency signals covering different wavelength bands. For example, under the phase matching conditions corresponding to this wavelength band, a phase matching angle of 20.3° for barium β-borate (BBO) corresponds to a mid-infrared difference frequency signal of 1.5–3 micrometers; a phase matching angle of 44.3° for magnesium oxide-doped lithium niobate crystal corresponds to a mid-infrared difference frequency signal of 3–4.5 micrometers. Through the cascaded difference frequency process, an ultra-wideband, carrier envelope phase-stable mid-infrared pulse output with a spectral coverage of 1.5–4.5 micrometers is ultimately obtained.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for generating CEP-stabilized multi-octave band mid-infrared pulses, characterized in that, Includes the following steps: Step 1: Generate broadband drive pulses Using ultrashort pulses as the initial light source, a broadband driving pulse covering the visible to near-infrared band is obtained through nonlinear spectral broadening, and the obtained broadband driving pulse contains at least one set of high-frequency components and one set of low-frequency components. Step 2: Chirp control of the broadband drive pulse Before the broadband driving pulse is incident on the nonlinear crystal, the chirp is determined based on the thickness of the nonlinear crystal and the group velocity walk-off between the frequency components in the nonlinear crystal. Then, the obtained broadband driving pulse is subjected to corresponding dispersion modulation based on the chirp to make the broadband driving pulse exhibit a non-zero chirp state. Step 3: Cascade nonlinear crystals and perform cascaded pulse difference frequency modulation. The dispersion-modulated broadband driving pulses are sequentially incident onto two nonlinear crystals cascaded along the light propagation direction to perform cascaded pulse difference frequency conversion. During the process of cascaded pulse intrafrequency difference, the group velocity walk-off in the nonlinear crystal is used to make the broadband driving pulses of different frequency components coincide in time at different propagation positions or in different nonlinear crystals, and the cascaded pulse intrafrequency difference is completed in the corresponding nonlinear crystal. Thus, the difference frequency signal with a longer wave component is preferentially generated in the first nonlinear crystal, and the difference frequency signal with a shorter wave component is generated in the second nonlinear crystal. Step 4: Obtain the ultra-wideband mid-infrared output pulse By spatially collinearly outputting the spectrally complementary difference frequency signals obtained from different nonlinear crystals, a mid-infrared ultrashort pulse output covering a multi-octave spectral range is obtained.

2. The CEP-stabilized multi-octave band mid-infrared pulse generation method according to claim 1, characterized in that: In step 1, the nonlinear spectral broadening methods include multi-thin-plate nonlinear broadening, hollow-core fiber nonlinear broadening, and gas or solid medium filament broadening.

3. The CEP-stabilized multi-octave mid-infrared pulse generation method according to claim 1 or 2, characterized in that: In step 2, the dispersion control method includes chirped mirror reflection, dispersion compensation prism pair, and grating dispersion modulation device.

4. The CEP-stabilized multi-octave band mid-infrared pulse generation method according to claim 3, characterized in that: In step 2, the dispersion modulation is specifically negative group delay dispersion, so that the broadband driving pulse of the high-frequency component leads the broadband driving pulse of the low-frequency component in time, thereby forming an initial temporal distribution of broadband driving pulses of different frequency components in the time domain.

5. The CEP-stabilized multi-octave band mid-infrared pulse generation method according to claim 1, characterized in that: In step 3, the material type, thickness, and cutting angle of each nonlinear crystal correspond to different phase-matching bands; The nonlinear crystal is a crystal with second-order nonlinear effects, and the material types include barium β-borate, bismuth borate, lithium niobate, and magnesium oxide-doped lithium niobate crystals.

6. The CEP-stabilized multi-octave band mid-infrared pulse generation method according to claim 5, characterized in that: In step 3, the number of nonlinear crystals is two; in the two-crystal cascaded difference frequency mode composed of two nonlinear crystals, the broadband driving light is divided into two pump components. , and signal light components ,and ; Define the group delay between different frequency components as , To quantitatively express the chirp amount, the thickness of the first nonlinear crystal is L1, the thickness of the second nonlinear crystal is L2, and the group velocity walk-off is... ; Then the amount of chirping The thickness L1 and group velocity of the first nonlinear crystal are diverging. The following conditions must be met: ； The thickness L2 and chirp of the second nonlinear crystal and the group move away quickly The following conditions must be met: 。 7. A CEP-stabilized multi-octave mid-infrared pulse generation system, used to implement the CEP-stabilized multi-octave mid-infrared pulse generation method according to any one of claims 1-6, characterized in that: It includes an ultrashort pulse laser source module, a spectral broadening module, a dispersion modulation module, a cascaded pulse intra-pulse difference frequency module, and an output and separation module; The ultrashort pulse laser source module is used to output ultrashort pulses; The spectral broadening module is connected to the ultrashort pulse laser source module and is used to generate broadband driving pulses; The dispersion modulation module is located in the output optical path of the spectral broadening module and is used to apply predetermined dispersion modulation to the broadband driving pulse. The cascaded pulse intra-frequency difference module includes two nonlinear crystals cascaded along the light propagation direction, used to realize cascaded pulse intra-frequency difference based on group velocity walk-off; The output and separation module is set in the output optical path of the cascaded pulse difference frequency module. By filtering out the residual driving pulse after the cascaded pulse difference frequency, it ensures that the spectrally complementary difference frequency signals obtained from different nonlinear crystals can be directly collinearly output in space, thereby obtaining mid-infrared ultrashort pulse output covering a multi-octave spectrum range.

8. The CEP-stabilized multi-octave mid-infrared pulse generation system according to claim 7, characterized in that: The ultrashort pulse laser source module is a femtosecond laser or a picosecond laser.

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