A method and system for synergistic regulation of high harmonic generation and above-threshold ionization

Abstract

The application relates to the field of laser technology and discloses a high-harmonic wave and above-threshold ionization synergic regulation method and system, which adopts a fundamental frequency light and multiple auxiliary fields to form a time-space overlapping composite laser field, adjusts the wavelength, intensity, delay time and polarization direction of the auxiliary field, forms a multi-parameter laser field, takes the multi-parameter laser field as a physical action carrier, synchronously collects HHG spectral intensity distribution and ATI electron spectrum data by using a high-sensitivity spectrometer and an electron spectrometer on the basis of the multi-parameter laser field, inputs the data into a Bayesian optimization algorithm, dynamically adjusts laser parameters, obtains an optimal laser parameter combination, adjusts an electron re-collision probability by adjusting laser ellipticity based on the obtained optimal laser parameter combination, controls an electron ionization time and return energy by using a two-color field carrier envelope phase, synchronously optimizes an HHG cutoff frequency and an ATI spectrum peak position, and realizes closed-loop control; and the application realizes synergic regulation of high-harmonic wave generation and above-threshold ionization processes.

Description

Technical Field

[0001] This invention relates to the field of laser technology, specifically to a method and system for the coordinated control of high-order harmonics and suprathreshold ionization. Background Technology

[0002] High-order harmonic generation (HHG) and above-threshold ionization (ATI) are two important nonlinear phenomena in the interaction between strong lasers and matter. HHG has broad application prospects in extreme ultraviolet and soft X-ray sources, attosecond pulse generation, and other fields. ATI is of great significance in atomic and molecular physics, ultrafast spectroscopy, and other research. However, most current research on HHG and ATI is conducted independently, lacking effective synergistic control methods. Existing control methods often only optimize the yield of HHG or the electron energy spectrum of ATI, and cannot simultaneously meet the specific requirements of these two phenomena in different application scenarios. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned problems by designing a method and system for coordinated control of higher harmonics and suprathreshold ionization.

[0004] The first aspect of this invention provides a method for synergistic control of higher harmonics and suprathreshold ionization, the method comprising the following steps:

[0005] A composite laser field with spatiotemporal overlap is formed by using fundamental frequency light and multiple auxiliary fields. By adjusting the wavelength, intensity, delay time and polarization direction of the auxiliary fields, a multi-parameter laser field is formed, which is then used as a carrier of physical interaction.

[0006] Based on the multi-parameter laser field, HHG spectral intensity distribution and ATI electronic energy spectrum data are simultaneously acquired by a high-sensitivity spectrometer and an electron spectrometer, and then input into a Bayesian optimization algorithm to dynamically adjust the laser parameters and obtain the optimal combination of laser parameters.

[0007] Based on the obtained optimal laser parameter combination, the probability of electron re-collision is controlled by adjusting the laser ellipticity, and the electron ionization time and return energy are modulated by using the two-color field carrier envelope phase. The HHG cutoff frequency and ATI energy spectrum peak position are optimized simultaneously to achieve closed-loop control.

[0008] Optionally, in a first implementation of the first aspect of the present invention, the method of using fundamental frequency light and multiple auxiliary fields to form a spatiotemporally overlapping composite laser field, and adjusting the wavelength, intensity, delay time, and polarization direction of the auxiliary fields to form a multi-parameter laser field, using the multi-parameter laser field as a physical interaction carrier, includes:

[0009] The parameters of the fundamental frequency light are determined, and the fundamental frequency light is split into multiple beams by a beam splitter. One beam is used as the main laser, and the remaining beams are used as seed lights for the auxiliary field.

[0010] For each seed beam, a high-order harmonic generator is used to convert the seed beam into an auxiliary field of the target wavelength. The polarization state of each beam is adjusted by a combination of half-wave plates and quarter-wave plates. A spatial light modulator is used to perform wavefront shaping on each beam.

[0011] The temporal waveform and phase information of each laser beam are measured by the direct electric field reconstruction method of spectral phase interferometry. The time delay between the auxiliary field and the main laser is adjusted by a precision delay line to ensure that each beam achieves spatiotemporal overlap at the focal position.

[0012] The polarization direction of linearly polarized light is adjusted by rotating a half-wave plate, and the ellipticity and azimuth angle of elliptically polarized light are adjusted by combining half-wave plates and quarter-wave plates. For the polarization combination of multiple lasers, the polarization characteristics of the synthesized light field are calculated using the Mueller matrix method.

[0013] The parameters of the fundamental frequency light and each auxiliary field are mapped to a point in a multi-dimensional parameter space. An initial population is generated in the multi-dimensional parameter space, and a genetic algorithm is used to optimize the parameters to form a multi-parameter laser field.

[0014] Optionally, in a second implementation of the first aspect of the present invention, the parameters of the fundamental frequency light include:

[0015] Select the fundamental frequency wavelength within the wavelength range of 800nm-2000nm, and set the pulse width, peak power density, and initial polarization state;

[0016] Determine the number of auxiliary fields and assign an initial wavelength, intensity scaling factor, initial delay time and polarization direction to each auxiliary field, where the initial wavelength is an integer or fractional multiple of the fundamental frequency wavelength.

[0017] Optionally, in a third implementation of the first aspect of the present invention, the step of mapping the fundamental frequency light and the parameters of each auxiliary field to a point in a multi-dimensional parameter space, generating an initial population in the multi-dimensional parameter space, and using a genetic algorithm to optimize the parameters to form a multi-parameter laser field includes:

[0018] The physical parameters of the fundamental frequency light and each auxiliary field are mapped to the gene loci of the chromosome, and the initial population is randomly generated in the multidimensional parameter space.

[0019] The tournament selection method is used to randomly select multiple chromosomes from the current population to form a competition group. The fitness values ​​of individuals in the competition group are compared, and the best individual is selected to enter the offspring. The selection operation is repeated to form a candidate population. An elite retention strategy is introduced to directly copy the best individual from the parent generation to the offspring.

[0020] Perform a crossover operation on individuals in the candidate population, randomly select paired individuals with crossover probability, and generate new values ​​for each gene locus of the paired chromosomes using arithmetic crossover.

[0021] Perform mutation operations on the crossover individuals, randomly select mutated gene positions with mutation probability, and add random perturbations that follow a Gaussian distribution to the selected gene positions.

[0022] The mutated offspring population is physically constrained and verified. Then it is determined whether the maximum number of iterations has been reached. If so, the chromosome with the highest fitness is selected from the final population as the optimal solution, forming a multi-parameter laser field.

[0023] Optionally, in the fourth implementation of the first aspect of the present invention, the step of simultaneously acquiring HHG spectral intensity distribution and ATI electron spectrum data using a high-sensitivity spectrometer and an electron spectrometer based on the multi-parameter laser field, and inputting them into a Bayesian optimization algorithm to dynamically adjust the laser parameters and obtain the optimal combination of laser parameters includes:

[0024] An initial sampling point is selected within a multi-parameter laser field, and a uniformly distributed point set covering the parameter space is generated using a Sobol sequence.

[0025] For each sampling point, HHG spectral intensity distribution and ATI electronic energy spectrum data are collected to obtain raw data, and target features are extracted from the raw data;

[0026] Radial basis functions were selected as covariance functions, and Markov chain Monte Carlo method was used to estimate the hyperparameters of the kernel function to construct a Gaussian process model.

[0027] The global optimal solution in the parameter space is predicted within a finite number of samplings using a Gaussian process model, and the optimal laser parameter combination is obtained by dynamically adjusting the laser field combination.

[0028] Optionally, in the fifth implementation of the first aspect of the present invention, the step of controlling the electron re-collision probability by adjusting the laser ellipticity based on the obtained optimal laser parameter combination, controlling the electron ionization time and return energy by utilizing the two-color field carrier envelope phase, and simultaneously optimizing the HHG cutoff frequency and ATI energy spectrum peak position to achieve closed-loop control includes:

[0029] Based on the obtained optimal laser parameter combination, key parameters related to electron dynamics are extracted, including at least laser ellipticity and two-color field carrier envelope phase.

[0030] An ellipticity-re-collision probability model and a CEP-ionization time / return energy model are constructed based on the strong field approximation theory.

[0031] Under the premise of fixing the two-color field carrier envelope phase, a single-parameter gradient search is performed on the laser ellipticity, and under the premise of fixing the laser ellipticity, a 0-2π full-cycle scan is performed on the two-color field carrier envelope phase.

[0032] Laser ellipticity and dual-color field carrier envelope phase are used as two-dimensional variables. The coordinate rotation method is used for joint optimization until the maximum number of iterations is reached to obtain the optimal combination, and the real-time feedback control loop is implemented.

[0033] Optionally, in the sixth implementation of the first aspect of the present invention, in the ellipticity-re-collision probability model, when the laser ellipticity is equal to 0, the electron trajectory is symmetrical in the two-dimensional plane. When the laser ellipticity increases, the electron trajectory gradually becomes three-dimensional. By pre-calculating the electron trajectory distribution under different laser ellipticity values, a Lookup table of laser ellipticity and re-collision probability is established.

[0034] In the CEP-ionization time / return energy model, the time difference between the ionization time and the return of electrons to the parent ion determines the return energy, which in turn affects the HHG cutoff frequency.

[0035] A second aspect of the present invention provides a system for coordinated control of higher harmonics and suprathreshold ionization, the system comprising:

[0036] The adjustment module is used to form a spatiotemporally overlapping composite laser field by using fundamental frequency light and multiple auxiliary fields. By adjusting the wavelength, intensity, delay time and polarization direction of the auxiliary fields, a multi-parameter laser field is formed, and the multi-parameter laser field is used as a physical action carrier.

[0037] The dynamic adjustment module is used to simultaneously acquire HHG spectral intensity distribution and ATI electronic energy spectrum data using a high-sensitivity spectrometer and an electron spectrometer based on a multi-parameter laser field, and input them into a Bayesian optimization algorithm to dynamically adjust the laser parameters and obtain the optimal combination of laser parameters.

[0038] The optimization module is used to control the electron re-collision probability by adjusting the laser ellipticity based on the obtained optimal laser parameter combination, and to regulate the electron ionization time and return energy by using the two-color field carrier envelope phase. It also simultaneously optimizes the HHG cutoff frequency and ATI energy spectrum peak position to achieve closed-loop control.

[0039] A third aspect of the present invention provides a device for coordinated control of higher harmonics and suprathreshold ionization, the device comprising a memory and at least one processor, the memory storing instructions; the at least one processor calling the instructions in the memory to cause the device to perform the steps of the coordinated control method for higher harmonics and suprathreshold ionization as described in any of the preceding claims.

[0040] A fourth aspect of the present invention provides a computer-readable storage medium storing instructions that, when executed by a processor, implement the steps of the method for coordinated control of higher harmonics and suprathreshold ionization as described in any of the preceding claims.

[0041] The technical solution provided by this invention employs a composite laser field that overlaps spatiotemporally with fundamental frequency light and multiple auxiliary fields. By adjusting the wavelength, intensity, delay time, and polarization direction of the auxiliary fields, a multi-parameter laser field is formed, which serves as the physical interaction carrier. Based on this multi-parameter laser field, a high-sensitivity spectrometer and an electron spectrometer are used to simultaneously acquire HHG spectral intensity distribution and ATI electron spectrum data, which are then input into a Bayesian optimization algorithm to dynamically adjust the laser parameters and obtain the optimal laser parameter combination. Based on the obtained optimal laser parameter combination, the probability of electron re-collision is controlled by adjusting the laser ellipticity, and the electron ionization time and return energy are modulated by using the two-color field carrier envelope phase. The HHG cutoff frequency and ATI spectrum peak position are simultaneously optimized to achieve closed-loop control. This invention achieves coordinated control of high-order harmonic generation and suprathreshold ionization processes, greatly improving the efficiency and accuracy of control. It can quickly find the optimal parameter combination that meets specific needs, promoting the technological development and application expansion in related fields. Attached Figure Description

[0042] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0043] Figure 1 A flowchart of the method for coordinated control of higher harmonics and suprathreshold ionization provided in an embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the structure of the high-order harmonics and suprathreshold ionization synergistic control system provided in an embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram of the structure of the high-order harmonics and suprathreshold ionization coordinated control device provided in an embodiment of the present invention. Detailed Implementation

[0046] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms “comprising” or “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, apparatus, product, or device that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0047] For ease of understanding, the specific process of the embodiments of the present invention is described below. Please refer to [link / reference]. Figure 1 A flowchart of the method for coordinated control of higher harmonics and suprathreshold ionization provided in this invention is shown. The method specifically includes the following steps:

[0048] Step 101: Use fundamental frequency light and multiple auxiliary fields to form a spatiotemporally overlapping composite laser field. By adjusting the wavelength, intensity, delay time and polarization direction of the auxiliary fields, a multi-parameter laser field is formed, and the multi-parameter laser field is used as the physical action carrier.

[0049] In this embodiment, the parameters of the fundamental frequency light are determined, and the fundamental frequency light is split into multiple beams by a beam splitter. One beam is used as the main laser, and the remaining beams are used as seed beams for the auxiliary field. For each seed beam, a high-order harmonic generator is used to convert the seed beam into an auxiliary field of the target wavelength. The polarization state of each beam is adjusted by combining half-wave plates and quarter-wave plates. A spatial light modulator is used to perform wavefront shaping on each beam. The temporal waveform and phase information of each laser are measured by the direct electric field reconstruction method of spectral phase interferometry. The time delay between the auxiliary field and the main laser is adjusted by a precision delay line to ensure that each beam achieves spatiotemporal overlap at the focal position. The polarization direction of the linearly polarized light is adjusted by rotating the half-wave plate, and the ellipticity and azimuth angle of the elliptically polarized light are adjusted by combining half-wave plates and quarter-wave plates. For the polarization combination of multiple lasers, the polarization characteristics of the synthesized light field are calculated by the Mueller matrix method.

[0050] The parameters of the fundamental frequency light and each auxiliary field are mapped to a point in a multi-dimensional parameter space. An initial population is generated in the multi-dimensional parameter space, and a genetic algorithm is used to optimize the parameters to form a multi-parameter laser field.

[0051] In this embodiment, the fundamental frequency light wavelength is selected from the wavelength range of 800nm-2000nm, and the pulse width, peak power density and initial polarization state are set; the number of auxiliary fields is determined, and each auxiliary field is assigned an initial wavelength, intensity scaling factor, initial delay time and polarization direction, wherein the initial wavelength is an integer or fractional multiple of the fundamental frequency light wavelength.

[0052] In this embodiment, the physical parameters of the fundamental frequency light and each auxiliary field are mapped to the gene loci of chromosomes, and an initial population is randomly generated in a multi-dimensional parameter space. A tournament selection method is used to randomly select multiple chromosomes from the current population to form a competition group. The fitness values ​​of individuals within the competition group are compared, and the optimal individual is selected to enter the offspring. This selection operation is repeated to form a candidate population. An elite retention strategy is introduced, directly replicating the optimal individual from the parent generation to the offspring. A crossover operation is performed on the individuals in the candidate population, randomly selecting paired individuals with a crossover probability. For each gene locus of the paired chromosomes, arithmetic crossover is used to generate a new value. A mutation operation is performed on the crossover individuals, randomly selecting mutated gene loci with a mutation probability. A random perturbation following a Gaussian distribution is added to the selected gene loci. The mutated offspring population is physically constrained and then it is determined whether the maximum number of iterations has been reached. If so, the chromosome with the highest fitness is selected from the final population as the optimal solution, forming a multi-parameter laser field.

[0053] In this embodiment, a spatiotemporally overlapping composite laser field is constructed using fundamental frequency light and 2-3 auxiliary fields. First, a beam splitter separates the fundamental frequency light into a main laser and a seed light. The seed light is then converted into auxiliary fields of specific wavelengths, such as 400nm frequency-doubled light or 1200nm third-harmonic light, by an optical parametric amplifier. Each auxiliary field is independently configured with an intensity adjuster to achieve intensity adjustment of 0.1-10 times the fundamental frequency light. The time delay of the main laser is controlled by a picosecond-precision delay line, such as -20fs to +20fs. The polarization control system employs a multi-stage waveplate combination to achieve linear polarization and ellipsoidal polarization. Circular polarization and circular polarization switching utilize a spatial light modulator to perform wavefront shaping on each beam, compensating for optical aberrations and controlling the focal position and intensity distribution, such as Gaussian or Bessel distribution. A synchronous triggering system ensures that all beams achieve precise spatiotemporal overlap in the gas target area, forming a composite light field containing multidimensional parameters such as wavelength ratio, intensity ratio, phase difference, and polarization state combination. This serves as the physical carrier for higher harmonics and suprathreshold ionization processes. In the gas target area, such as a helium or argon jet target, the linear polarization azimuth angle is continuously adjustable from 0 to 360°, and the elliptic polarization ellipticity is controllable from 0 to 1.

[0054] Step 102: Based on the multi-parameter laser field, use a high-sensitivity spectrometer and an electron spectrometer to simultaneously acquire HHG spectral intensity distribution and ATI electron spectrum data, and input them into a Bayesian optimization algorithm to dynamically adjust the laser parameters and obtain the optimal combination of laser parameters.

[0055] In this embodiment, initial sampling points are selected within the multi-parameter laser field, and a uniformly distributed point set covering the parameter space is generated using a Sobol sequence. For each sampling point, HHG spectral intensity distribution and ATI electronic energy spectrum data are collected to obtain raw data, from which target features are extracted. A radial basis function is selected as the covariance function, and the hyperparameters of the kernel function are estimated using the Markov chain Monte Carlo method to construct a Gaussian process model. The global optimal solution of the parameter space is predicted within a finite number of samplings using the Gaussian process model, and the laser field combination is dynamically adjusted to obtain the optimal laser parameter combination.

[0056] In this embodiment, after a multi-parameter laser field acts on a gas target to generate high-harmonic generation (HHG) and upthreshold ionization (ATI) signals, these signals are synchronously acquired using a high-sensitivity spectrometer and a magnetic bottle-type electron spectrometer. A sub-femtosecond synchronous triggering system ensures that the signals correspond to the same laser pulse. The Latin hypercube sampling method is used to generate initial sample points in the laser parameter space, including parameters such as wavelength, intensity, delay, and polarization. The initial sample points are typically 50 uniformly distributed points. These points sequentially drive the laser system to output the composite field corresponding to the parameters, acquiring HHG spectral intensity distribution and ATI electron spectrum data. HHG cutoff frequency, target energy range yield, and ATI main peak energy and energy dissipation are extracted. This data is then input into a Bayesian optimization algorithm. A Gaussian process model is used to model the mapping relationship between parameters and features. The Matérn kernel function is selected to describe the correlation in the parameter space, and the kernel function hyperparameters are optimized using maximum likelihood estimation. The expected improvement is defined as the acquisition function, balancing exploration and utilization. The next set of laser parameters to be tested is iteratively selected, with 5-10 new points added in each iteration. After each experiment, the training dataset is updated, and the Gaussian process model is refitted until the function value change rate is less than 1% for 10 consecutive generations or a preset number of iterations is reached, such as 80. Finally, the optimal parameter combination that optimizes the HHG yield and ATI energy spectrum target is extracted from the model. After the stability is verified by 5 repeatable experiments, the optimal laser parameters are output to the control system. At the same time, a real-time feedback mechanism is established. When the signal deviation exceeds 5%, Bayesian optimization is automatically triggered to fine-tune the parameters, ensuring that the laser system operates in an optimal state in the long term.

[0057] Step 103: Based on the obtained optimal laser parameter combination, the electron re-collision probability is controlled by adjusting the laser ellipticity, and the electron ionization time and return energy are modulated by using the two-color field carrier envelope phase. The HHG cutoff frequency and ATI energy spectrum peak position are optimized simultaneously to achieve closed-loop control.

[0058] In this embodiment, based on the obtained optimal laser parameter combination, key parameters related to electron dynamics are extracted, including at least laser ellipsoidity and two-color field carrier envelope phase; an ellipsoidity-re-collision probability model and a CEP-ionization time / return energy model are constructed based on the strong field approximation theory; under the premise of fixing the two-color field carrier envelope phase, a single-parameter gradient search is performed on the laser ellipsoidity, and under the premise of fixing the laser ellipsoidity, a 0-2π full-cycle scan is performed on the two-color field carrier envelope phase;

[0059] Laser ellipticity and dual-color field carrier envelope phase are used as two-dimensional variables. The coordinate rotation method is used for joint optimization until the maximum number of iterations is reached to obtain the optimal combination, and the real-time feedback control loop is implemented.

[0060] In this embodiment, in the construction of the ellipticity-recollision probability model, the laser ellipticity is defined to range from 0 to 1, and 21 discrete sampling points are divided with a step size of 0.05. For each laser ellipticity value, the initial electron momentum distribution is generated based on the strong field approximation theory. It is assumed that the initial position of the electron when it enters the laser field after tunnel ionization is near the atomic nucleus, and the initial velocity is determined by the instantaneous laser electric field. The classical trajectory Monte Carlo method is used to simulate the motion trajectory of the ionized electron in the composite laser field. The three-dimensional position coordinates of the electron from the ionization time to the time of leaving the laser field are recorded. For each trajectory, it is determined whether a "recollision" event has occurred: if the electron returns to the region less than 0.1 nm away from the atomic nucleus during the motion, it is considered a valid recollision, and the count is incremented by 1. Multiple independent electron trajectories are simulated for each laser ellipticity value, and the recollision probability is calculated as the number of recollision events / the total number of trajectories, forming a correspondence table between the laser ellipticity value and P_recoll, i.e., the Lookup table.

[0061] In the CEP-ionization time / return energy model, the carrier envelope phase (CEP) of the two-color field is accurately measured using spectral phase interferometry, ranging from 0 to 2π. Eight phase points are defined with a step size of π / 8. For each CEP value, the time-dependent Schrödinger equation is solved using the finite-difference time-domain method to calculate the tunneling ionization rate of the atom and determine the probability distribution of the ionization time t0. After being accelerated in the laser field, some ionized electrons return to the parent ion under the influence of the light field, with the return time equal to nT, where n is the number of light periods. The kinetic energy of the returning electrons is calculated according to the Newton-Lorentz equation. By statistically analyzing independent ionization events, a mapping relationship between CEP and the average ionization time and average return energy is established. Finally, the data is fitted using cubic spline interpolation to form the CEP-ionization time / return energy model, which is used to predict the electron return energy under different CEP values, thereby determining the HHG cutoff frequency.

[0062] In this embodiment, closed-loop control of the HHG cutoff frequency and ATI energy spectrum peak position is achieved based on the optimal combination of laser parameters output by Bayesian optimization. Laser ellipticity is used as the core parameter for controlling the electron re-collision probability. The ellipticity is gradually adjusted from 0 to 0.8 using a combination of half-wave and quarter-wave plates. HHG and ATI energy spectrum data are collected every 0.05 seconds to establish an ellipticity-re-collision probability mapping relationship and determine the initial ellipticity value, such as 0.2, that maximizes the HHG yield. Simultaneously, the two-color field carrier envelope phase is used as a key parameter for regulating the electron ionization time and return energy. An electro-optic phase modulator scans within the 0-2π range, collecting data in steps of π / 16. The correlation between ionization time and return energy is analyzed using a classical trajectory Monte Carlo model to lock the HHG cutoff frequency and ATI main peak energy simultaneously. The CEP range close to the target value, such as π / 4-3π / 4, is then used for joint optimization in the two-dimensional parameter space using the coordinate rotation method: the CEP is fixed at the midpoint of the optimal range, and the ellipticity is perturbed by a small step size of ±0.02. The local optimum is found by gradient descent. The ellipticity is then fixed again, and the CEP is finely adjusted by ±π / 32. This iteration is repeated until the objective function (such as the deviation between the HHG cutoff frequency and the ATI peak position of the weighted combination) converges. The final optimal combination, such as ellipticity 0.25±0.01 and CEP=π / 2±π / 64, is input into the closed-loop control system. By comparing the deviation between the measured spectrum and the target spectrum in real time, a threshold of 2% is set to trigger the dynamic adjustment of the waveplate angle and phase modulator. A feedback loop is completed every 100 laser pulses to ensure that the system can maintain optimal performance under external interference.

[0063] In this embodiment, laser ellipticity describes the degree of ellipticity of the laser polarization state, directly affecting the re-collision probability of electrons in the laser field. The higher the ellipticity, the stronger the deviation of the electron trajectory from the plane, and the lower the re-collision probability. The two-color field carrier envelope phase: the relative phase between the light field oscillation and the envelope in the two-color field determines the ionization time of the electron and its kinetic energy when returning to the parent nucleus. Changing the CEP will shift the ionization-acceleration-re-collision sequence of electrons in the laser field. The HHG cutoff frequency: depends on the maximum kinetic energy of the electron when returning to the parent nucleus. It needs to be controlled by the CEP to adjust the acceleration time and energy acquisition efficiency of the electron in the two-color field. The ATI energy spectrum peak position: is determined by the initial kinetic energy distribution after electron tunneling ionization. It needs to be controlled by the ellipticity to control the complexity of the electron's trajectory in the laser field after ionization (the trajectory is more regular and the peak position is more concentrated under low ellipticity).

[0064] The optimal combination requires finding a balance between the two. Low ellipticity increases the re-collision probability to improve the HHG cutoff frequency, but may broaden the ATI peak position. Appropriate CEP offset can compensate for the ionization time, so that the electron return energy and ATI peak position are optimized at the same time. The optimal combination refers to the pairing of the specific value of laser ellipticity determined by the closed-loop optimization algorithm with the CEP phase value of the two-color field. This combination can make the HHG cutoff frequency and ATI energy spectrum peak position reach the preset optimization target at the same time.

[0065] Please see Figure 2 A schematic diagram of the structure of the high-order harmonics and suprathreshold ionization synergistic control system provided in this embodiment of the invention.

[0066] The adjustment module is used to form a spatiotemporally overlapping composite laser field by using fundamental frequency light and multiple auxiliary fields. By adjusting the wavelength, intensity, delay time and polarization direction of the auxiliary fields, a multi-parameter laser field is formed, and the multi-parameter laser field is used as a physical action carrier.

[0067] The dynamic adjustment module is used to simultaneously acquire HHG spectral intensity distribution and ATI electronic energy spectrum data using a high-sensitivity spectrometer and an electron spectrometer based on a multi-parameter laser field, and input them into a Bayesian optimization algorithm to dynamically adjust the laser parameters and obtain the optimal combination of laser parameters.

[0068] The optimization module is used to control the electron re-collision probability by adjusting the laser ellipticity based on the obtained optimal laser parameter combination, and to regulate the electron ionization time and return energy by using the two-color field carrier envelope phase. It also simultaneously optimizes the HHG cutoff frequency and ATI energy spectrum peak position to achieve closed-loop control.

[0069] Figure 3 This is a schematic diagram of a high-order harmonic and suprathreshold ionization coordinated control device 600 provided in an embodiment of the present invention. The high-order harmonic and suprathreshold ionization coordinated control device 600 can vary considerably due to different configurations or performance. It may include one or more central processing units (CPUs) 610 (e.g., one or more processors) and a memory 620, and one or more storage media 630 (e.g., one or more mass storage devices) storing application programs 633 or data 632. The memory 620 and storage media 630 can be temporary or persistent storage. The program stored in the storage media 630 may include one or more modules (not shown in the diagram), each module may include a series of instruction operations on the high-order harmonic and suprathreshold ionization coordinated control device 600. Furthermore, the processor 610 may be configured to communicate with the storage media 630 and execute the series of instruction operations in the storage media 630 on the high-order harmonic and suprathreshold ionization coordinated control device 600 to implement the method provided in the above embodiment.

[0070] The high-order harmonics and suprathreshold ionization coordinated control device 600 may further include one or more power supplies 640, one or more wired or wireless network interfaces 650, one or more input / output interfaces 660, and / or one or more operating devices 631, such as Windows Server, Mac OS X, Unix, Linux, FreeBSD, etc. Those skilled in the art will understand that... Figure 3 The structure of the high-order harmonics and suprathreshold ionization coordinated control device shown does not constitute a limitation on the computer device provided by the present invention. It may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0071] The present invention also provides a computer-readable storage medium, which can be a non-volatile computer-readable storage medium or a volatile computer-readable storage medium, wherein the computer-readable storage medium stores instructions that, when the instructions are executed on a computer, cause the computer to perform the various steps of the higher harmonics and suprathreshold ionization coordinated control method provided in the above embodiments.

[0072] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the above-described equipment or apparatus / unit can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0073] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0074] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for synergistic control of higher harmonics and suprathreshold ionization, characterized in that, The method includes the following steps: A composite laser field with spatiotemporal overlap is formed by using fundamental frequency light and multiple auxiliary fields. By adjusting the wavelength, intensity, delay time and polarization direction of the auxiliary fields, a multi-parameter laser field is formed, which is then used as a carrier of physical interaction. Based on the multi-parameter laser field, HHG spectral intensity distribution and ATI electronic energy spectrum data are simultaneously acquired by a high-sensitivity spectrometer and an electron spectrometer, and then input into a Bayesian optimization algorithm to dynamically adjust the laser parameters and obtain the optimal combination of laser parameters. Based on the obtained optimal laser parameter combination, the probability of electron re-collision is controlled by adjusting the laser ellipticity, and the electron ionization time and return energy are modulated by using the two-color field carrier envelope phase. The HHG cutoff frequency and ATI energy spectrum peak position are optimized simultaneously to achieve closed-loop control. The method employs a composite laser field formed by the spatiotemporal overlap of fundamental frequency light and multiple auxiliary fields. By adjusting the wavelength, intensity, delay time, and polarization direction of the auxiliary fields, a multi-parameter laser field is formed. This multi-parameter laser field serves as a physical interaction carrier, including: The parameters of the fundamental frequency light are determined, and the fundamental frequency light is split into multiple beams by a beam splitter. One beam is used as the main laser, and the remaining beams are used as seed lights for the auxiliary field. For each seed beam, a high-order harmonic generator is used to convert the seed beam into an auxiliary field of the target wavelength. The polarization state of each beam is adjusted by a combination of half-wave plates and quarter-wave plates. A spatial light modulator is used to perform wavefront shaping on each beam. The temporal waveform and phase information of each laser beam are measured by the direct electric field reconstruction method of spectral phase interferometry. The time delay between the auxiliary field and the main laser is adjusted by a precision delay line to ensure that each beam achieves spatiotemporal overlap at the focal position. The polarization direction of linearly polarized light is adjusted by rotating a half-wave plate, and the ellipticity and azimuth angle of elliptically polarized light are adjusted by combining half-wave plates and quarter-wave plates. For the polarization combination of multiple lasers, the polarization characteristics of the synthesized light field are calculated using the Mueller matrix method. The parameters of the fundamental frequency light and each auxiliary field are mapped to a point in a multi-dimensional parameter space. An initial population is generated in the multi-dimensional parameter space, and a genetic algorithm is used to optimize the parameters to form a multi-parameter laser field.

2. The method for coordinated control of higher harmonics and suprathreshold ionization as described in claim 1, characterized in that, The parameters of the fundamental frequency light include: Select the fundamental frequency wavelength within the wavelength range of 800nm-2000nm, and set the pulse width, peak power density, and initial polarization state; Determine the number of auxiliary fields and assign an initial wavelength, intensity scaling factor, initial delay time and polarization direction to each auxiliary field, where the initial wavelength is an integer or fractional multiple of the fundamental frequency wavelength.

3. The method for coordinated control of higher harmonics and suprathreshold ionization as described in claim 1, characterized in that, The process of mapping the parameters of the fundamental frequency light and each auxiliary field to a point in a multi-dimensional parameter space, generating an initial population in the multi-dimensional parameter space, and using a genetic algorithm to optimize the parameters to form a multi-parameter laser field includes: The physical parameters of the fundamental frequency light and each auxiliary field are mapped to the gene loci of the chromosome, and the initial population is randomly generated in the multidimensional parameter space. The tournament selection method is used to randomly select multiple chromosomes from the current population to form a competition group. The fitness values ​​of individuals in the competition group are compared, and the best individual is selected to enter the offspring. The selection operation is repeated to form a candidate population. An elite retention strategy is introduced to directly copy the best individual from the parent generation to the offspring. Perform a crossover operation on individuals in the candidate population, randomly select paired individuals with crossover probability, and generate new values ​​for each gene locus of the paired chromosomes using arithmetic crossover. Perform mutation operations on the crossover individuals, randomly select mutated gene positions with mutation probability, and add random perturbations that follow a Gaussian distribution to the selected gene positions. The mutated offspring population is physically constrained and verified. Then it is determined whether the maximum number of iterations has been reached. If so, the chromosome with the highest fitness is selected from the final population as the optimal solution, forming a multi-parameter laser field.

4. The method for coordinated control of higher harmonics and suprathreshold ionization as described in claim 1, characterized in that, Based on the multi-parameter laser field, the method involves simultaneously acquiring HHG spectral intensity distribution and ATI electron spectral data using a high-sensitivity spectrometer and an electron spectrometer, and inputting these data into a Bayesian optimization algorithm to dynamically adjust the laser parameters and obtain the optimal combination of laser parameters, including: An initial sampling point is selected within a multi-parameter laser field, and a uniformly distributed point set covering the parameter space is generated using a Sobol sequence. For each sampling point, HHG spectral intensity distribution and ATI electronic energy spectrum data are collected to obtain raw data, and target features are extracted from the raw data; Radial basis functions were selected as covariance functions, and Markov chain Monte Carlo method was used to estimate the hyperparameters of the kernel function to construct a Gaussian process model. The global optimal solution in the parameter space is predicted within a finite number of samplings using a Gaussian process model, and the optimal laser parameter combination is obtained by dynamically adjusting the laser field combination.

5. The method for coordinated control of higher harmonics and suprathreshold ionization as described in claim 1, characterized in that, Based on the obtained optimal laser parameter combination, the electron re-collision probability is controlled by adjusting the laser ellipticity, and the electron ionization time and return energy are modulated using the two-color field carrier envelope phase. Simultaneously, the HHG cutoff frequency and ATI energy spectrum peak position are optimized to achieve closed-loop control, including: Based on the obtained optimal laser parameter combination, key parameters related to electron dynamics are extracted, including at least laser ellipticity and two-color field carrier envelope phase. An ellipticity-re-collision probability model and a CEP-ionization time / return energy model are constructed based on the strong field approximation theory. Under the premise of fixing the two-color field carrier envelope phase, a single-parameter gradient search is performed on the laser ellipticity, and under the premise of fixing the laser ellipticity, a 0-2π full-cycle scan is performed on the two-color field carrier envelope phase. Laser ellipticity and dual-color field carrier envelope phase are used as two-dimensional variables. The coordinate rotation method is used for joint optimization until the maximum number of iterations is reached to obtain the optimal combination, and the real-time feedback control loop is implemented.

6. The method for coordinated control of higher harmonics and suprathreshold ionization as described in claim 5, characterized in that, In the ellipticity-re-collision probability model, when the laser ellipticity is equal to 0, the electron trajectory is symmetrical in the two-dimensional plane. As the laser ellipticity increases, the electron trajectory gradually becomes three-dimensional. By pre-calculating the electron trajectory distribution under different laser ellipticity values, a lookup table of laser ellipticity and re-collision probability is established. In the CEP-ionization time / return energy model, the time difference between the ionization time and the return of electrons to the parent ion determines the return energy, which in turn affects the HHG cutoff frequency.

7. A system for coordinated control of high-order harmonics and suprathreshold ionization, characterized in that, The system includes: The adjustment module is used to form a spatiotemporally overlapping composite laser field by using fundamental frequency light and multiple auxiliary fields. By adjusting the wavelength, intensity, delay time and polarization direction of the auxiliary fields, a multi-parameter laser field is formed, and the multi-parameter laser field is used as a physical action carrier. The dynamic adjustment module is used to simultaneously acquire HHG spectral intensity distribution and ATI electronic energy spectrum data using a high-sensitivity spectrometer and an electron spectrometer based on a multi-parameter laser field, and input them into a Bayesian optimization algorithm to dynamically adjust the laser parameters and obtain the optimal combination of laser parameters. The optimization module is used to control the electron re-collision probability by adjusting the laser ellipticity based on the obtained optimal laser parameter combination, and to regulate the electron ionization time and return energy by using the two-color field carrier envelope phase. It also simultaneously optimizes the HHG cutoff frequency and ATI energy spectrum peak position to achieve closed-loop control.

8. A device for coordinated control of high-order harmonics and suprathreshold ionization, characterized in that, The higher harmonics and suprathreshold ionization coordinated control device includes a memory and at least one processor, wherein the memory stores instructions; the at least one processor calls the instructions in the memory to cause the higher harmonics and suprathreshold ionization coordinated control device to perform the various steps of the higher harmonics and suprathreshold ionization coordinated control method as described in any one of claims 1-6; The method employs a composite laser field formed by the spatiotemporal overlap of fundamental frequency light and multiple auxiliary fields. By adjusting the wavelength, intensity, delay time, and polarization direction of the auxiliary fields, a multi-parameter laser field is formed. This multi-parameter laser field serves as a physical interaction carrier, including: The parameters of the fundamental frequency light are determined, and the fundamental frequency light is split into multiple beams by a beam splitter. One beam is used as the main laser, and the remaining beams are used as seed lights for the auxiliary field. For each seed beam, a high-order harmonic generator is used to convert the seed beam into an auxiliary field of the target wavelength. The polarization state of each beam is adjusted by a combination of half-wave plates and quarter-wave plates. A spatial light modulator is used to perform wavefront shaping on each beam. The temporal waveform and phase information of each laser beam are measured by the direct electric field reconstruction method of spectral phase interferometry. The time delay between the auxiliary field and the main laser is adjusted by a precision delay line to ensure that each beam achieves spatiotemporal overlap at the focal position. The polarization direction of linearly polarized light is adjusted by rotating a half-wave plate, and the ellipticity and azimuth angle of elliptically polarized light are adjusted by combining half-wave plates and quarter-wave plates. For the polarization combination of multiple lasers, the polarization characteristics of the synthesized light field are calculated using the Mueller matrix method. The parameters of the fundamental frequency light and each auxiliary field are mapped to a point in a multi-dimensional parameter space. An initial population is generated in the multi-dimensional parameter space, and a genetic algorithm is used to optimize the parameters to form a multi-parameter laser field.

9. A computer-readable storage medium storing instructions thereon, characterized in that, When the instructions are executed by the processor, they implement the various steps of the method for coordinated control of higher harmonics and suprathreshold ionization as described in any one of claims 1-6.

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