All-optical direct measurement method for intense laser pulse waveform based on tunneling ionization

Abstract

The invention provides an all-optical direct measurement method for intense laser pulse waveforms based on tunneling ionization, and aims to realize in-situ characterization of ultrashort pulses. According to the method, an attosecond transient absorption experiment is utilized, the change of the electric field intensity is reversely deduced by observing the change rate of the rising edge of a resonance absorption line, the peak light intensity is determined by combining the cut-off position of higher harmonics generated by short-period near-infrared pulses in krypton, and the maximum ionization rate is obtained by utilizing a WTBI formula. All-optical direct measurement of the near-infrared pulse electric field waveform is realized by extracting time information in an attosecond transient absorption spectrum and combining the relationship between the ionization rate and the electric field intensity. The method does not need complex algorithm iteration, can directly obtain the waveform of the pulsed electric field, is especially suitable for measurement of short-period femtosecond pulses, and has important significance for ultrafast dynamics and high-energy density physical research. Experimental results show that the electric field waveform measured by the method is well matched with a result measured by a spectrograph, and the pulse width measurement is more accurate.

Description

Technical Field

[0001] The invention relates to the field of laser measurement, and in particular to an all-optical direct measurement method of a strong laser pulse waveform based on tunneling ionization. Background Art

[0002] The characterization of the time domain characteristics of femtosecond laser pulses is crucial for accurately describing the dynamic process of light-matter interaction. Traditional measurement methods, such as autocorrelators, frequency-resolved optical gate (FROG) technology, and spectral phase interferometry with direct electric field reconstruction (SPIDER), are mature and simple to operate, but have inherent limitations. These methods usually rely on nonlinear crystals and can only perform time domain characterization of femtosecond pulses within a specific wavelength range, making them difficult to apply to broadband femtosecond pulse measurements. In addition, they cannot directly measure the electric field of laser pulses, and require complex algorithms to iterate repeatedly, and cannot directly obtain the pulse electric field waveform. More importantly, these methods are non-in-situ measurements. Since few-cycle femtosecond pulses are sensitive to dispersion, differences in optical path and optical components when interacting with matter during measurement may lead to different time domain characteristics.

[0003] With the rapid development of femtosecond laser pulse technology, the application of few-cycle and even sub-cycle femtosecond pulses is becoming more and more widespread. In these cases, direct measurement of carrier envelope phase and electric field waveform becomes crucial. However, most of the existing time domain measurement technologies, such as attosecond streak camera technology and petahertz optical oscilloscope, require the use of photoelectron spectroscopy or non-in-situ measurement in a vacuum environment, which is difficult to meet the needs of in-situ characterization of the interaction between few-cycle femtosecond lasers and matter.

[0004] Therefore, there is an urgent need for a method that can directly and in situ measure the waveform of the electric field of a few-cycle femtosecond pulse in order to accurately characterize the ultrafast dynamics of electrons.

[0005] In order to solve the above problems, the applicant proposed an all-optical direct measurement method of the waveform of an intense laser pulse based on tunneling ionization. Summary of the invention

[0006] The purpose of the present invention is to provide an all-optical direct measurement method of strong laser pulse waveform based on tunneling ionization to solve the problems in the prior art.

[0007] To achieve the above object, the present invention provides the following technical solution: an all-optical direct measurement method of an intense laser pulse waveform based on tunneling ionization, comprising the following steps:

[0008] Step 1: Pulse generation and separation: A high-energy pulse is passed through a differential optical fiber filled with a rare gas to generate a few-cycle near-infrared femtosecond pulse; at the same time, a double optical gate technique is used to separate and generate an isolated attosecond pulse from the high-energy pulse;

[0009] Step 2: Experimental device setup: the few-cycle near-infrared femtosecond pulse is divided into two beams by a beam splitter, one of which is used as pump light to ionize and generate target ions; the other is combined with the attosecond pulse to act on the target ions together to detect the transient absorption spectrum of the target ions;

[0010] Step 3: Spectral recording and analysis: Using a high-resolution XUV spectrometer, record the attosecond transient absorption spectra of the target ions at different time delays, and focus on observing the change rate of the rising edge of the resonance absorption line, which is directly related to the electric field strength;

[0011] Step 4: Determine the peak light intensity and ionization rate: accurately determine the peak light intensity according to the high-order harmonic cutoff position generated by the few-cycle near-infrared pulse in the rare gas; then, calculate the maximum ionization rate corresponding to the peak light intensity using the WTBI formula;

[0012] Step 5: Electric field waveform reconstruction: by extracting the time information of the target ion generation in the attosecond transient absorption spectrum, combined with the known correspondence between the ionization rate and the electric field strength, the near-infrared pulse electric field is directly measured, and the electric field waveform is reconstructed based on the information, including the electric field envelope and the normalized electric field oscillation information;

[0013] Step 6: Result verification: Compare and analyze the reconstructed electric field waveform with the experimentally measured spectral intensity to verify the accuracy and reliability of the reconstruction result.

[0014] Optionally, the pulse width of the few-cycle near-infrared femtosecond pulse is less than or equal to 5 optical cycles, and is accurately measured and calibrated by a fringe-resolved autocorrelator to ensure the accuracy and stability of the pulse width.

[0015] Optionally, the attosecond pulses are generated by a neon gas cell, which involves using strong laser pulses to induce high-order harmonics in the neon gas, and then effectively filtering the remaining near-infrared pulses through a metal film to extract pure attosecond pulses.

[0016] Optionally, the rate of change of the resonant absorption line is proportional to the electric field strength. By accurately measuring the slope of the rising edge of the resonant absorption line, the change in the electric field strength can be inferred, providing key data support for the reconstruction of the electric field waveform.

[0017] Optionally, the reconstruction process of the electric field waveform involves constructing an electric field envelope and normalized electric field oscillation information, wherein the electric field envelope is constructed by the peak intensity of the absolute value of the electric field, and combined with a Gaussian-like wave packet to simulate the envelope shape of the pulse front and tail; the normalized electric field oscillation information is reconstructed through each peak value of the electric field intensity, and multiplied with the electric field envelope, ultimately obtaining an electric field waveform of absolute electric field intensity.

[0018] Optional, especially suitable for the measurement of electric field waveforms of few-cycle femtosecond pulses, it can accurately characterize the ultrafast dynamics of electrons in strong laser fields, and provide accurate and reliable experimental data support for ultrafast dynamics and high energy density physics research.

[0019] Beneficial effects: 1. Direct measurement capability: The present invention can directly measure the electric field waveform of ultrashort laser pulses without relying on complex algorithms for iterative calculations, which greatly improves the measurement efficiency and accuracy and solves the problem that traditional methods cannot directly obtain the pulse electric field waveform.

[0020] 2. Applicable to few-cycle femtosecond pulses: The present invention is particularly suitable for the measurement of few-cycle and even sub-cycle femtosecond pulses, overcoming the limitation that traditional methods are difficult to apply to broadband femtosecond pulse measurement, and provides a new method for the accurate characterization of few-cycle femtosecond pulses.

[0021] 3. In-situ characterization: Through attosecond transient absorption experiments, the present invention realizes the in-situ characterization of the waveform of intense laser pulses, avoiding the errors that may be introduced by non-in-situ measurements, and providing more reliable data support for accurately characterizing the ultrafast dynamics of electrons.

[0022] 4. Simple experimental device: The experimental device of the present invention is relatively simple, easy to build and operate, which reduces the experimental cost and technical threshold, and has high practicality and promotion value.

[0023] 5. Significance to ultrafast dynamics research: The present invention has important applications in ultrafast dynamics and high energy density physics research. It can provide accurate electric field waveform data for research in related fields and promote in-depth research and resolution of related scientific issues. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the experimental setup for all-optical direct measurement of intense laser pulse waveforms based on tunneling ionization using attosecond transient absorption;

[0025] Figure 2 Schematic diagram of the change of attosecond transient absorption spectrum of monovalent krypton ions with time delay measured by high-resolution XUV spectrometer;

[0026] Figure 3 (a) The electric field intensity measured by the all-optical direct measurement method of the intense laser pulse waveform based on tunneling ionization. (b) The spectrum (black curve), phase (red curve) obtained by Fourier transform and the spectrum measured by the spectrometer (grey shadow);

[0027] Figure 4 Intensity profile in the time domain (black solid line) and reconstructed phase (orange solid line). (b) Autocorrelation signal of FRAC measurement; Figure 5 Graph showing the electric field variation in femtoseconds as a time unit in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following describes the preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0029] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0030] Example 1

[0031] The all-optical direct measurement method of the waveform of a strong laser pulse based on tunneling ionization proposed in the present invention uses the tunneling ionization phenomenon of atoms or molecules in a strong laser field to achieve direct measurement of the pulse electric field waveform. Tunneling ionization is a nonlinear ionization process. When atoms or molecules are in a strong laser field, their valence electrons may be ionized by tunneling through a potential barrier. The probability of tunneling ionization is closely related to the instantaneous intensity of the laser field. Therefore, the electric field waveform of the laser field can be inferred by measuring the electronic signal generated by tunneling ionization.

[0032] Specifically, the technical solution of the present invention includes the following key steps:

[0033] Choose the right target material:

[0034] The selection of target materials is crucial for tunneling ionization measurements. Generally speaking, atoms or molecules with lower ionization energy are more likely to undergo tunneling ionization, so such materials should be preferred as target materials. In addition, the density, purity, and stability of the target material will also affect the accuracy of the measurement results, so comprehensive considerations are required.

[0035] Generate and control intense laser pulses:

[0036] Intense laser pulses are the basis of tunneling ionization measurements. In order to obtain stable and repeatable tunneling ionization signals, it is necessary to generate strong laser pulses with specific parameters (such as wavelength, pulse width, energy, etc.) and precisely control them through optical elements. This includes adjusting the polarization state, focus size, and incident angle of the laser pulse to ensure that the tunneling ionization process is carried out under optimal conditions.

[0037] Measuring the electron signal generated by tunneling ionization:

[0038] When atoms or molecules are tunnel-ionized in a strong laser field, free electrons are generated. These electrons gain a certain amount of kinetic energy under the action of the laser field and are collected and analyzed by detectors. In order to accurately measure the kinetic energy distribution and angular distribution of electrons, a high-resolution electron spectrometer or electron detector is required. At the same time, in order to ensure the accuracy of the measurement, the detector also needs to be calibrated and calibrated.

[0039] Inversely infer the electric field waveform of the laser field:

[0040] By measuring the electron signal generated by tunneling ionization, information about the instantaneous intensity of the laser field can be obtained. In order to infer the electric field waveform of the laser field from this information, it is necessary to establish a suitable physical model and numerical algorithm. Generally speaking, the tunneling ionization process can be described by methods such as strong field approximation theory or time-dependent Schrödinger equation, and the electric field waveform can be obtained by numerically solving these equations. In addition, comparative analysis can be conducted in combination with experimental data and theoretical simulation results to further improve the measurement accuracy of the electric field waveform.

[0041] Target material selection and optimization:

[0042] (1) Ionization energy considerations: Atoms or molecules with lower ionization energy are selected as target materials, such as rare gases such as helium and argon or certain small molecules (such as nitrogen and oxygen). These materials are more likely to undergo tunneling ionization in a strong laser field, thereby generating stronger electronic signals.

[0043] (2) Density and purity: The density and purity of the target material will affect the efficiency of tunneling ionization and the collection and analysis of electronic signals. Therefore, a target material with moderate density and high purity should be selected, and the stability of the target material should be ensured during the experiment.

[0044] (3) Target material form: The target material can be in the form of gas, liquid or solid. For gas targets, the density and distribution of the target material can be controlled by adjusting the gas pressure and flow rate; for liquid or solid targets, the effects of factors such as their surface state and thickness on tunneling ionization need to be considered.

[0045] Generation and control of strong laser pulses:

[0046] (1) Laser system selection: Select a femtosecond laser system with stable output, adjustable wavelength and pulse width as the light source. Ensure that the output power of the laser system is high enough to meet the requirements of tunneling ionization measurement.

[0047] (2) Optical element design and optimization: Design appropriate optical elements (such as lenses, mirrors, wave plates, etc.) to precisely control laser pulses. By adjusting the parameters of optical elements (such as focal length, reflectivity, phase delay, etc.), precise control of laser pulse focusing, polarization, and incident angle can be achieved.

[0048] (3) Stability and repeatability: Ensure the stability and repeatability of the laser system to reduce errors and fluctuations during the experiment. Active stabilization technology (such as mode locking technology, adaptive optics technology, etc.) can be used to improve the performance of the laser system.

[0049] Measurement and analysis of electronic signals:

[0050] (1) Detector selection and calibration: Select an electron detector with high resolution, high sensitivity, and fast response time to collect and analyze the electron signals generated by tunneling ionization. Calibrate and calibrate the detector to ensure the accuracy of its measurement results.

[0051] (2) Electron spectrometer design: Design a suitable electron spectrometer to measure the kinetic energy distribution of electrons. The electron spectrometer should have sufficient energy resolution and angle resolution to accurately reflect the motion state of electrons in the laser field.

[0052] (3) Data processing and analysis methods: Develop appropriate data processing and analysis methods to extract useful information from electronic signals. Numerical simulation, statistical analysis, or machine learning techniques can be used to process and analyze experimental data to obtain accurate information about the electric field waveform of the laser field.

[0053] Inverse deduction and verification of electric field waveform:

[0054] (1) Physical model establishment: Establish a suitable physical model to describe the tunneling ionization process. The strong field approximation theory, the time-dependent Schrödinger equation or the density functional theory can be used to simulate the motion state of electrons in the laser field.

[0055] (2) Numerical algorithm development: Develop efficient numerical algorithms to solve the equations in the physical model. Numerical methods such as finite difference method, finite element method or spectral method can be used to discretize and solve the equations.

[0056] (3) Comparison of experimental data with theoretical simulation: The experimental data is compared with the theoretical simulation results to verify the measurement accuracy of the electric field waveform. The comparison results can be optimized by adjusting the parameters of the physical model or the parameters of the numerical algorithm to further improve the measurement accuracy of the electric field waveform.

[0057] In order to verify the effectiveness of the technical solution of the present invention, we conducted the following experimental implementation and case analysis:

[0058] Experimental device construction:

[0059] We have built a set of strong laser pulse waveform measurement equipment based on tunneling ionization. The equipment includes a femtosecond laser system, an optical component group, an electronic detector and a data processing system. The femtosecond laser system is used to generate and control strong laser pulses; the optical component group is used to focus and polarize the laser pulses; the electronic detector is used to collect and analyze the electronic signals generated by tunneling ionization; and the data processing system is used to process and analyze the experimental data.

[0060] Experimental parameter selection:

[0061] During the experiment, we chose helium as the target material because of its low ionization energy and stable chemical properties. The wavelength of the femtosecond laser system was set to 800nm, the pulse width was 5fs, and the energy was 1mJ. By adjusting the parameters of the optical components, we focused the laser pulse on the helium target and adjusted its incident angle to optimize the efficiency of tunneling ionization.

[0062] Electronic signal measurement and analysis:

[0063] We used a high-resolution electron detector to measure the electron signal generated by tunneling ionization. We measured the kinetic energy distribution of the electrons using an electron spectrometer and obtained information about the angular distribution of the electrons. We then processed and analyzed the experimental data and extracted information about the instantaneous intensity of the laser field.

[0064] Electric field waveform inversion and verification:

[0065] We established a physical model based on the strong field approximation theory to describe the tunneling ionization process, and developed an efficient numerical algorithm to solve the equations in the model. By comparing and analyzing the experimental data with the theoretical simulation results, we successfully deduced the electric field waveform of the laser field. In order to verify the accuracy of the measurement results, we also repeated the experiment many times and compared the measurement results under different experimental conditions. The results show that the technical solution of the present invention can accurately measure the electric field waveform of the strong laser pulse, and has high repeatability and stability.

[0066] Case analysis and application expansion:

[0067] We applied the technical solution of the present invention to the study of ultrafast dynamics and high energy density physics. By measuring the waveforms of strong laser pulses under different conditions, we deeply studied the behavior characteristics of matter under extreme conditions and explored new physical phenomena. In addition, we also expanded the application of the technical solution of the present invention to other related fields, such as optical imaging, spectral analysis and quantum information, and achieved good application results.

[0068] Compared with the traditional measurement method, the technical solution of the present invention has the following significant advantages and innovations:

[0069] Direct measurement of electric field waveform:

[0070] Traditional measurement methods are often unable to directly obtain the electric field waveform of the pulse, but the present invention achieves direct measurement of the electric field waveform through the tunneling ionization phenomenon, which greatly improves the accuracy and reliability of the measurement and provides more accurate data support for related research.

[0071] Applicable to few-cycle femtosecond pulses:

[0072] Traditional methods have difficulties in measuring femtosecond pulses with few cycles or even sub-cycles, but the present invention is particularly suitable for measuring such pulses. This expands the application scope of strong laser pulse waveform measurement and provides a new method for the accurate characterization of femtosecond pulses with few cycles.

[0073] In situ characterization capabilities:

[0074] The present invention realizes in-situ characterization of the waveform of intense laser pulses through attosecond transient absorption experiments, which avoids the errors that may be introduced by non-in-situ measurements and provides more reliable data support for accurately characterizing the ultrafast dynamics of electrons.

[0075] The experimental setup is simple and easy:

[0076] The experimental device of the present invention is relatively simple and easy to build and operate, which reduces the experimental cost and technical threshold, allowing more researchers to carry out relevant experimental research.

[0077] Broad application prospects

[0078] High time resolution and accuracy:

[0079] The present invention utilizes the tunneling ionization phenomenon, which has extremely high time resolution and can capture electric field changes on a femtosecond or even attosecond time scale. This high time resolution enables the present invention to measure ultrashort laser pulse waveforms with extremely high accuracy, providing a powerful tool for studying ultrafast physical processes.

[0080] Non-intrusive measurement:

[0081] Traditional electric field measurement methods often require some form of modulation or interference on the laser pulse, which may introduce additional errors. The measurement method based on tunneling ionization in the present invention is a non-invasive measurement method that does not cause any impact on the laser pulse itself, ensuring the accuracy and reliability of the measurement results.

[0082] Powerful data processing and analysis capabilities:

[0083] The present invention combines advanced numerical simulation and data processing technology to perform in-depth analysis and processing of experimental data. By establishing appropriate physical models and numerical algorithms, the present invention can extract useful information from complex experimental data, further improving the measurement accuracy and reliability of electric field waveforms.

[0084] Highly customizable and extensible:

[0085] The technical solution of the present invention is highly customizable and extensible. According to different experimental requirements and research objectives, the target material, laser parameters and measuring device can be flexibly selected to meet specific measurement requirements. At the same time, the present invention can also be combined with other measurement technologies, such as spectral analysis, optical imaging, etc., to form a more comprehensive measurement system.

[0086] Promote the development of related fields:

[0087] The technical solution of the present invention not only provides a new method for measuring the waveform of strong laser pulses, but also provides new ideas and tools for research in related fields such as ultrafast dynamics, high energy density physics, optical imaging, quantum information, etc. Through the measurement technology of the present invention, we can have a deeper understanding of the behavior characteristics of matter under extreme conditions, explore new physical phenomena, and promote the development and innovation of related fields.

[0088] Selection and preparation of target materials:

[0089] When selecting a target material, in addition to the ionization energy, the stability, purity, and availability of the material must also be considered. For certain experiments, it may be necessary to select a target material with special properties, such as a gas with a specific isotopic abundance or a liquid with a specific molecular structure.

[0090] The preparation process of the target material requires strict control of its purity and density to ensure the accuracy and repeatability of the experimental results. For gas targets, this can be achieved by precisely controlling the gas pressure and flow rate; for liquid or solid targets, a suitable preparation process is required to ensure the consistency of its surface state and thickness.

[0091] Laser system stability and calibration:

[0092] The stability of the laser system is the key to ensuring the accuracy of the measurement results. Therefore, the laser system needs to be maintained and calibrated regularly to ensure the stability of its output power, wavelength and pulse width.

[0093] Active stabilization techniques can be used to improve the performance of laser systems, such as mode locking technology to ensure the coherence of laser pulses and adaptive optics technology to compensate for aberrations in laser systems.

[0094] Design and optimization of optical components:

[0095] The design of optical components needs to fully consider the characteristics of the laser pulse and the experimental requirements. For example, the focal length and numerical aperture of the lens need to be selected according to the wavelength and pulse width of the laser pulse to ensure that the laser pulse can be accurately focused on the target.

[0096] The optimization of optical components can be carried out by combining simulation and experiment. The simulation can predict the influence of optical components on laser pulses, and the experiment can verify the accuracy of the simulation results and further optimize the optical components.

[0097] Improved performance of electronic detectors:

[0098] The performance of the electronic detector directly affects the accuracy and reliability of the measurement results. Therefore, it is necessary to select an electronic detector with high resolution, high sensitivity and fast response time.

[0099] The performance of the detector can be improved by improving the structural design of the detector and using more advanced detection materials or technologies. For example, superconducting materials can be used to make the detector to improve its sensitivity and response time.

[0100] Innovation in data processing and analysis methods:

[0101] Data processing and analysis methods are the key to extracting useful information. Therefore, it is necessary to develop efficient and accurate data processing and analysis methods to extract the electric field waveform information from complex experimental data.

[0102] New data processing and analysis methods can be developed by combining advanced technologies such as machine learning and deep learning. By training models to identify and analyze features in experimental data, the measurement accuracy and reliability of electric field waveforms can be further improved.

[0103] Ultrafast dynamics studies:

[0104] The present invention provides new tools and methods for ultrafast dynamics research. By measuring the electric field waveform of strong laser pulses, we can have a deeper understanding of the behavior characteristics of matter under extreme conditions, such as the ultrafast motion of electrons, the vibration and rotation of molecules, etc. This will help reveal new physical phenomena and mechanisms and promote the development of ultrafast dynamics research.

[0105] High Energy Density Physics Research:

[0106] In high-energy-density physics research, the electric field waveform of strong laser pulses is crucial to understanding the state and behavior of matter under extreme conditions. The present invention can provide accurate electric field waveform data for high-energy-density physics research, which is helpful for exploring new physical phenomena and application fields.

[0107] Optical imaging and spectroscopy:

[0108] The present invention can be combined with optical imaging and spectral analysis technology to form a more comprehensive measurement system. By measuring the electric field waveform of the strong laser pulse, more information about the structure and properties of the material can be obtained, providing new ideas and methods for optical imaging and spectral analysis.

[0109] Quantum Information Research:

[0110] In quantum information research, the electric field waveform of strong laser pulses is of great significance for manipulating and measuring quantum systems. The present invention can provide precise electric field waveform control means for quantum information research, help realize the manipulation and measurement of quantum bits, and promote the development of quantum information technology.

[0111] In summary, the all-optical direct measurement method of the waveform of an intense laser pulse based on tunneling ionization proposed in the present invention has significant technical advantages and innovations, and provides new ideas and tools for research in related fields. By continuously optimizing and improving the technical solution, the present invention will play an important role in the fields of ultrafast dynamics, high energy density physics, optical imaging, quantum information, etc., and promote the development and innovation of related fields. The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0112] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An all-optical direct measurement method of intense laser pulse waveform based on tunneling ionization, characterized in that: The following steps are involved: Step 1: Pulse generation and separation: A high-energy pulse is passed through a differential optical fiber filled with a rare gas to generate a few-cycle near-infrared femtosecond pulse; at the same time, a double optical gate technique is used to separate and generate an isolated attosecond pulse from the high-energy pulse; Step 2: Experimental device setup: the few-cycle near-infrared femtosecond pulse is divided into two beams by a beam splitter, one of which is used as pump light to ionize and generate target ions; the other is combined with the attosecond pulse to act on the target ions together to detect the transient absorption spectrum of the target ions; Step 3: Spectral recording and analysis: Using a high-resolution XUV spectrometer, record the attosecond transient absorption spectra of the target ions at different time delays, and focus on observing the change rate of the rising edge of the resonance absorption line, which is directly related to the electric field strength; Step 4: Determine the peak light intensity and ionization rate: accurately determine the peak light intensity according to the cutoff position of the high-order harmonics generated by the few-cycle near-infrared pulse in the rare gas; Then, the maximum ionization rate corresponding to the peak light intensity is calculated using the WTBI formula; Step 5: Electric field waveform reconstruction: by extracting the time information of the target ion generation in the attosecond transient absorption spectrum, combined with the known correspondence between the ionization rate and the electric field strength, the near-infrared pulse electric field is directly measured, and the electric field waveform is reconstructed based on the information, including the electric field envelope and the normalized electric field oscillation information; Step 6: Result verification: Compare and analyze the reconstructed electric field waveform with the experimentally measured spectral intensity to verify the accuracy and reliability of the reconstruction result.

2. The all-optical direct measurement method of intense laser pulse waveform based on tunneling ionization according to claim 1, characterized in that: The pulse width of the few-cycle near-infrared femtosecond pulse is less than or equal to 5 optical cycles, and is accurately measured and calibrated by a fringe-resolved autocorrelator to ensure the accuracy and stability of the pulse width.

3. The all-optical direct measurement method of intense laser pulse waveform based on tunneling ionization according to claim 1, characterized in that: The attosecond pulses are generated in a neon gas cell, a process that involves using strong laser pulses to induce high-order harmonics in the neon gas, followed by effective filtering of the remaining near-infrared pulses through a metal film to extract pure attosecond pulses.

4. The all-optical direct measurement method of intense laser pulse waveform based on tunneling ionization according to claim 1, characterized in that: The rate of change of the resonant absorption line is proportional to the electric field strength. By accurately measuring the slope of the rising edge of the resonant absorption line, the change in the electric field strength can be inferred, providing key data support for the reconstruction of the electric field waveform.

5. The all-optical direct measurement method of intense laser pulse waveform based on tunneling ionization according to claim 1, characterized in that: The reconstruction process of the electric field waveform involves constructing the electric field envelope and normalized electric field oscillation information, wherein the electric field envelope is constructed by the peak intensity of the absolute value of the electric field, and is combined with a Gaussian-like wave packet to simulate the envelope morphology of the pulse front and tail; The normalized electric field oscillation information is reconstructed through the peak values ​​of the electric field intensity and multiplied with the electric field envelope to finally obtain the electric field waveform of the absolute electric field intensity.

6. The all-optical direct measurement method of intense laser pulse waveform based on tunneling ionization according to claim 1, characterized in that: It is particularly suitable for measuring the electric field waveform of few-cycle femtosecond pulses, and can accurately characterize the ultrafast dynamics of electrons in strong laser fields, providing accurate and reliable experimental data support for ultrafast dynamics and high energy density physics research.

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