Short-wavelength-based higher harmonic generation device and method

Abstract

The invention belongs to the technical field of ultrafast laser, and particularly relates to a higher harmonic generation device and method based on short wavelength, and the device comprises a laser source which is used for generating femtosecond laser pulses; the frequency conversion module is used for converting the femtosecond laser pulse into a short-wavelength driving pulse; the excitation target unit is used for generating higher harmonics by utilizing short-wavelength driving pulses; a cooperative control unit; wherein the working state of the frequency conversion module meets a first resonance condition, and the working state of the excitation target unit meets a second resonance condition; according to the invention, the cooperative control unit dynamically couples the resonance states of the frequency conversion module and the excitation target unit, thereby solving the problem of linkage detuning caused by light wavelength jittering driven by short wavelength and mismatching of system resonance conditions caused by the jittering. Due to the problem, an existing device cannot stably work in an optimal state for a long time, and the stability and the conversion efficiency of higher harmonic output power are restricted.

Description

Technical Field

[0001] This invention belongs to the field of ultrafast laser technology, specifically a device and method for generating high-order harmonics based on short wavelengths. Background Technology

[0002] The short-wavelength high-harmonic generation technology belongs to the field of ultrafast lasers and nonlinear optics. It is a key method for generating coherent light sources in the extreme ultraviolet to soft X-ray bands. Its core lies in using a femtosecond laser with high peak power to interact nonlinearly with matter (such as gas). Through the high-harmonic process, the frequency of the long-wavelength incident laser is significantly up-converted, thereby obtaining output light with short wavelength and high photon energy.

[0003] This technology aims to solve the technical challenge of how to simultaneously obtain extreme ultraviolet light sources with high photon energy, high repetition rate, and high average power.

[0004] In the prior art, the frequency conversion module and the excitation target unit in the high-order harmonic generation device usually work independently or are only subject to single-variable control. Since the working states of these two modules (which depend on the first resonance condition and the second resonance condition respectively) are essentially deeply coupled through the common short-wavelength driving pulse wavelength, the detuning of any single module (such as that caused by environmental disturbances) will not only reduce its own efficiency, but will also affect the resonance state of the other module through wavelength changes, resulting in a sharp deterioration in overall performance.

[0005] In summary, existing technologies lack the ability to perceive and jointly control this coupling relationship, making it impossible for the entire device to operate stably at a high level for a long period of time, thus restricting further improvement in the stability of high-order harmonic output power and conversion efficiency.

[0006] Therefore, the present invention provides a device and method for generating high-order harmonics based on short wavelengths. Summary of the Invention

[0007] To address the shortcomings of existing technologies and solve the problem that existing technologies lack the ability to perceive and jointly control this coupling relationship, thus preventing the entire device from operating stably at a high level for a long period of time, which restricts the further improvement of the stability and conversion efficiency of high-order harmonic output power.

[0008] The technical solution adopted by this invention to solve its technical problem is: A device and method for generating high-order harmonics based on short wavelengths, 1. A device for generating high-order harmonics based on short wavelengths, characterized in that it comprises:

[0009] A laser source used to generate femtosecond laser pulses;

[0010] The frequency conversion module is used to convert femtosecond laser pulses into short-wavelength drive pulses;

[0011] Excitation target unit, used to generate high-order harmonics using short-wavelength driving pulses;

[0012] Collaborative control unit;

[0013] The operating state of the frequency conversion module satisfies the first resonance condition, and the operating state of the excitation target unit satisfies the second resonance condition.

[0014] The first physical parameter on which the first resonance condition depends and the second physical parameter on which the second resonance condition depends are coupled to each other through the wavelength of the short-wavelength driving pulse;

[0015] The collaborative control unit is configured to: synchronously acquire the state information of the first resonance condition and the second resonance condition by monitoring the first feedback signal and the second feedback signal related to the wavelength, and generate control commands according to the coupling relationship of the state information to synchronously adjust the working parameters of the frequency conversion module and the excitation target unit, so that the device is locked in a collaborative working state in which the first resonance condition and the second resonance condition are simultaneously optimized.

[0016] Furthermore, the core of the coupling relationship lies in the fact that the driving light wavelength is a shared variable connecting the two resonance conditions; the collaborative control unit, by processing the feedback signal reflecting this coupling relationship, realizes the synchronous adjustment of the operating parameters of the frequency conversion module and the excitation target unit, thereby overcoming the chain detuning problem caused by independent control; the short wavelength driving pulse is preferably in the deep ultraviolet band, with a wavelength between 200nm and 400nm.

[0017] Preferably, the first resonance condition is a quasi-phase matching condition, and the frequency conversion module includes an electro-optically tuned superlattice crystal whose polarization period Λ satisfies the relationship between the wavelength λ of the femtosecond laser pulse: λ = 2•n_eff • Λ, where n_eff is the effective refractive index;

[0018] The second resonance condition includes the photonic bandgap resonance condition, wherein the excitation target unit comprises a hollow photonic crystal fiber, and the center wavelength of its bandgap is matched with the wavelength of the short-wavelength driving pulse;

[0019] The co-control unit is configured to fine-tune the quasi-phase matching condition by adjusting the voltage applied to the electro-optically tuned superlattice crystal, and to simultaneously fine-tune the photonic bandgap resonance condition by adjusting the strain applied to the photonic crystal fiber.

[0020] Furthermore, the combination of electro-optic tunable crystal and strain-tunable fiber provides rapid and precise wavelength control capability; its working principle is that voltage changes the crystal refractive index to maintain quasi-phase matching, and strain changes the fiber lattice constant to maintain bandgap matching. The two work together to achieve rapid tracking and locking of the driving wavelength.

[0021] Preferably, the second resonance condition further includes a quantum energy level resonance condition, and the excitation target unit further includes a quantum dot placed in a photonic crystal fiber, wherein the excitation energy level of the quantum dot is matched with the photon energy of the short-wavelength driving pulse.

[0022] Preferably, the energy of the first exciton absorption peak E_ex of the quantum dot and the photon energy E_DUV of the short-wavelength driving pulse satisfy: |E_DUV - E_ex| / E_ex < 5%.

[0023] Furthermore, the introduction of quantum dots aims to utilize their exciton resonance effect; when the driving light energy is matched with the exciton energy level, the nonlinear interaction between light and matter can be significantly enhanced, thereby directly improving the conversion efficiency of higher harmonics.

[0024] Preferably, the collaborative control unit obtains a first feedback signal by monitoring the wavelength jitter of the short-wavelength drive pulse, and obtains a second feedback signal by monitoring the mode characteristics change of the drive pulse transmitted from the excitation target unit.

[0025] Furthermore, wavelength jitter directly characterizes the deviation of the phase matching state, while the transmitted light mode characteristics directly reflect the bandgap matching state.

[0026] Preferably, the collaborative control unit synchronously adjusts at least two parameters among the output wavelength of the laser source, the voltage applied to the superlattice crystal, and the strain applied to the photonic crystal fiber according to the control command, and the adjustment range is dynamically adapted according to the coupling relationship between the first feedback signal and the second feedback signal.

[0027] Furthermore, dynamic adaptation refers to the control algorithm allocating the adjustment amount of each actuator in a non-fixed proportion according to the calculation results of the real-time feedback signal; this model-based control strategy can achieve a faster and smoother system response and effectively avoid overshoot.

[0028] Preferably, the collaborative control unit includes a state space controller for generating the control commands based on the coupling relationship;

[0029] The state space controller has a control cycle of less than 10 milliseconds and can suppress the long-term power fluctuation of the target high-order harmonics output by the device to within ±3%, of which long-term refers to continuous operation for no less than 4 hours.

[0030] A method for generating high-order harmonics based on short wavelengths, characterized by comprising: a synchronous acquisition step:

[0031] The first feedback signal characterizing the first resonance condition state satisfied by the working state of the frequency conversion module and the second feedback signal characterizing the second resonance condition state satisfied by the working state of the excitation target unit are acquired synchronously, wherein the first resonance condition and the second resonance condition are coupled to each other through the wavelength of the short-wavelength driving pulse.

[0032] Coupling processing step: Input the first feedback signal and the second feedback signal into the multivariable control model, which characterizes the mutual influence relationship between the first resonance condition and the second resonance condition;

[0033] Collaborative execution steps: Based on the output of the multivariable control model, at least two control commands are generated synchronously and sent to the frequency conversion module and the excitation target unit respectively to adjust their operating parameters, so that the frequency conversion module and the excitation target unit maintain a collaborative working state in which both the first resonance condition and the second resonance condition are locked.

[0034] Preferably, the multivariable control model in the coupling process is a state-space model established in advance through system identification.

[0035] Preferably, in the collaborative execution step, the phase matching condition is fine-tuned by adjusting the voltage applied to the electro-optic crystal in the frequency conversion module, and the bandgap condition is fine-tuned by synchronously adjusting the strain of the photonic crystal fiber in the excitation target unit.

[0036] The beneficial effects of this invention are as follows:

[0037] The present invention discloses a high-order harmonic generation device and method based on short wavelength. By coordinating and controlling the resonant conditions of frequency conversion and excitation target unit in real time, the present invention can actively compensate for environmental disturbances and suppress long-term fluctuations in high-order harmonic output power to within ±3%. This solves the power drift problem caused by detuning in existing devices and provides a reliable light source for precision applications. Attached Figure Description

[0038] The invention will now be further described with reference to the accompanying drawings.

[0039] Figure 1 is a block diagram showing the overall structure and signal flow of the device of the present invention;

[0040] Figure 2 is a schematic diagram of the disassembly and partial assembly of the core module of the device of the present invention;

[0041] Figure 3 is a block diagram of the multivariable dynamic adaptation control logic of the collaborative control unit of the present invention. Detailed Implementation

[0042] The following detailed description of the device and method for generating high-order harmonics based on short wavelengths, in conjunction with the accompanying drawings and several embodiments, illustrates the present invention. Each embodiment fully covers all the technical features of the claims and demonstrates the scope of protection through differentiated designs. All technical solutions achieve the core inventive objective of "dual-resonance condition cooperative locking" and possess repeatability and industrial application value.

[0043] In this invention, the short-wavelength driving pulse is preferably in the deep ultraviolet band, for example, with a wavelength between 200 nm and 400 nm. However, this invention is not limited to this; the short-wavelength driving pulse may also include the visible light band, for example, with a wavelength between 400 nm and 780 nm. By employing short-wavelength driving, the strong dependence of higher harmonic generation efficiency on the driving wavelength can be utilized, significantly improving photon energy conversion efficiency.

[0044] Example 1: Dual-resonance coordinated control high-order harmonic generation device

[0045] 1. Device Composition

[0046] Laser source: A Ti:sapphire femtosecond laser is used to output femtosecond laser pulses with a center wavelength of 800nm, a pulse width of 50fs, a repetition frequency of 1kHz, and a peak power of 2GW. The beam quality factor M²≤1.2 meets the basic requirements for pump light generated by high-order harmonics.

[0047] Frequency conversion module: The core is a 1cm long periodically polarized lithium niobate (PPLN) electro-optic tunable superlattice crystal with a polarization period Λ=15.8μm, satisfying the quasi-phase matching condition λ=2•n_eff•Λ (n_eff is the effective refractive index, with a value of 2.21). Electro-optic tuning is achieved by applying an adjustable voltage of 0-5kV. The nonlinear coefficient d 33 With a voltage of approximately 27 pm / V, it can convert 800 nm fundamental frequency light into 267 nm deep ultraviolet driving pulses, achieving a conversion efficiency of 45%.

[0048] Excitation target unit: Hollow photonic crystal fiber (inner diameter 10μm, cladding period 2μm) is used, and the fiber is filled with CdTe quantum dots (particle size 5nm). The energy deviation between the quantum dot exciton level and the 267nm deep ultraviolet driving pulse is ≤3%, which satisfies the dual conditions of photonic bandgap resonance and quantum level resonance. The quantum dot array spacing is 3nm, and the nonlinear refractive index can be adjusted to a range of 10⁻¹²cm² / W.

[0049] The collaborative control unit includes a wavelength monitoring module (monitoring the wavelength jitter of the deep ultraviolet driving pulse with an accuracy of ±0.01nm) and a transmitted light mode monitoring module (acquiring the light spot morphology and light intensity distribution). It senses the system status through the first feedback signal (wavelength jitter amount) and the second feedback signal (mode distortion coefficient). The control core is an STM32 microcontroller with a built-in basic PID control algorithm.

[0050] 2. The principle behind this embodiment:

[0051] Quasi-phase matching principle: In the frequency conversion module, the superlattice crystal forms a reciprocal lattice vector G=2π / Λ through periodic polarization, which compensates for the phase mismatch Δk in the three-wave mixing process, making Δk'=Δk-G=0, thus achieving efficient conversion from fundamental frequency light to deep ultraviolet light. The effective nonlinear coefficient d_eff=(2 / π)d 33 This significantly improves conversion efficiency.

[0052] Dual resonance coupling principle: In the excitation target unit, the photonic bandgap of the hollow photonic crystal fiber is matched with the wavelength of the deep ultraviolet driving pulse. At the same time, the quantum dot exciton energy level resonates with the driving light energy. The dual resonance effect enhances the nonlinear interaction, which improves the generation efficiency of high-order harmonics (mainly the 7th to 15th harmonics, with wavelengths of 30-40nm) by more than 3 times.

[0053] Collaborative control principle: The collaborative control unit collects dual feedback signals in real time. When wavelength jitter causes the first resonance mismatch, it outputs control command 1 to adjust the voltage of the superlattice crystal and change its refractive index n_eff to correct the phase matching condition. When the distortion of the transmitted light mode reflects the second resonance shift, it outputs control command 2 to finely adjust the pressure of the photonic crystal fiber fixing clamp (adjustment range 0-5N) to change the fiber strain to correct the photonic bandgap and achieve synchronous locking of the dual resonance conditions.

[0054] 3. The workflow in this embodiment is as follows:

[0055] The laser source is activated and stably outputs 800nm ​​femtosecond pulses, which are then beam expanded and collimated before being incident on the frequency conversion module.

[0056] The frequency conversion module converts the fundamental frequency light into a 267nm deep ultraviolet driving pulse under quasi-phase matching conditions, and the control unit monitors the wavelength of the pulse in real time (first feedback signal).

[0057] A deep ultraviolet driving pulse is incident on the excitation target unit, and high-order harmonics are excited through photonic bandgap resonance and quantum energy level resonance. The control unit synchronously monitors the transmitted light mode characteristics (second feedback signal).

[0058] The collaborative control unit dynamically allocates the adjustment amount (the ratio of voltage regulation to strain regulation is 1:1) based on the coupling relationship of the dual feedback signals, synchronously corrects the parameters of the two modules, and maintains the dual resonance state.

[0059] A stable high-order harmonic beam is output, and the target band harmonics are obtained after filtering by the filter module.

[0060] 4. In this embodiment, when the device operates for a long time (2 consecutive hours), the high-order harmonic power fluctuation is ≤±5%, the control cycle is ≤20ms, and the 7th harmonic conversion efficiency reaches 8%, which can meet the needs of basic scientific research experiments and fully cover the core technical features of claims 1-5, 8, and 10.

[0061] Example 2: Multivariable Cooperative Control Device for High-Order Harmonic Generation

[0062] 1. Equipment Improvement

[0063] Frequency conversion module optimization: It adopts a 2cm long magnesium-doped lithium niobate (MgO:LiNbO3) superlattice crystal with a chirped structure of polarization period Λ=14.6-16.2μm, and the group velocity mismatch is controlled within ±0.5ps / mm. It has better broadband matching characteristics, and the electro-optic tuning voltage range is extended to 0-10kV, with a wavelength tuning range of ±5nm.

[0064] Excitation target unit optimization: The quantum dots adopt a gradient size array (particle size 3-7nm) to achieve broadband nonlinear control in the range of 400-1600nm. At the same time, microlens arrays are added at both ends of the photonic crystal fiber to optimize beam coupling efficiency and reduce mode distortion.

[0065] The collaborative control unit has been upgraded: the control core has been replaced with a DSP processor, with a built-in state space controller. The control cycle has been optimized to <10ms. A new system identification module has been added, which can establish a multivariable control model under dual resonance conditions in real time and dynamically adapt the adjustment range (the adjustment ratio can be adaptively switched between 1:0.5 and 1:2).

[0066] 2. Principle of this embodiment:

[0067] Chirped superlattice phase matching principle: The chirped superlattice crystal compensates for the group velocity mismatch of broadband femtosecond pulses through periodic gradient, so that different wavelength components meet the quasi-phase matching conditions, the conversion efficiency is increased to more than 60%, and the spectral bandwidth of the deep ultraviolet driving pulse is extended to 10nm, providing a basis for broadband high-order harmonic generation.

[0068] Multivariable dynamic adaptation principle: The state-space controller is based on the coupled model obtained by system identification. It takes wavelength jitter, mode distortion coefficient and ambient temperature (new monitoring parameter) as input variables and solves the optimal control quantity through matrix operation. It avoids the overshoot and lag problems of single PID control. When the ambient temperature changes by ±5℃, it can still maintain the stability of dual resonance conditions and break through the dependence of traditional control on the environment.

[0069] 3. In this embodiment, compared with Embodiment 1, the control accuracy is higher: the control cycle of the state space controller is shortened from 20ms to 8ms, and the long-term power fluctuation is suppressed within ±3%, which is 40% higher than Embodiment 1, meeting the stringent stability requirements of high-precision experiments;

[0070] Greater environmental adaptability: The combination of the broadband matching characteristics of the chirped superlattice and the multivariable control model enables the device to work stably in environments with temperatures of 5-35℃ and humidity of 30%-70%, while Example 1 can only maintain its performance in a constant temperature environment of 20-25℃.

[0071] Wider harmonic coverage: Gradient-size quantum dot arrays enable broadband nonlinear modulation, covering the 5th to 21st harmonics (wavelength 25-53nm), which is 60% wider than the harmonic band of Example 1, making it applicable to a wider range of scenarios;

[0072] Higher conversion efficiency: The long-size magnesium-doped superlattice crystal and optimized coupling structure enable a deep ultraviolet conversion efficiency of 60% and a high-order harmonic conversion efficiency of 12%, which is 50% higher than that of Example 1.

[0073] Example 3: Cooperatively Coupled High-Order Harmonic Generation Device

[0074] 1. Equipment Enhancement

[0075] Laser source upgrade: Adopting an all-solid-state femtosecond laser with an output center wavelength of 1064nm, pulse width of 100fs, repetition frequency of 10kHz, peak power of 5GW, beam quality factor M²≤1.1, and long-term output stability (RMS)≤±0.5%, meeting the requirements of continuous industrial operation.

[0076] Enhanced frequency conversion module: The superlattice crystal adopts a two-dimensional hexagonal superlattice structure, which can simultaneously satisfy three wave vector conservation conditions to achieve multi-wavelength coordinated conversion. The polarization period tolerance is controlled within ±50nm. It is equipped with an active temperature control module (temperature control accuracy ±0.1℃) to further suppress the influence of temperature on phase matching.

[0077] Enhanced excitation target unit: Diamond-coated hollow photonic crystal fiber (power density increased to 10GW / cm²) is used. Quantum dots and helical DNA are assembled to form a chiral supramolecular structure, which enhances the circular dichroism signal by 40 times and the nonlinear optical response speed by 2 times. At the same time, an airflow cooling module (nitrogen flow rate 1-5L / min) is added to avoid thermal damage to quantum dots.

[0078] Industrialized design of the collaborative control unit: It adopts an industrial-grade PLC controller (Siemens S7-1200), equipped with redundant control loops and fault diagnosis modules, supports Ethernet communication and remote monitoring, and the control algorithm is upgraded to a hybrid algorithm combining model predictive control (MPC) and fuzzy adaptive PID, which can identify abnormal states such as sensor drift and actuator jamming and automatically switch to backup loops.

[0079] 2. The principle of this embodiment:

[0080] Multi-wave vector matching principle: The two-dimensional hexagonal superlattice forms multiple reciprocal lattice vector components through complex periodic modulation, which can simultaneously compensate for the phase mismatch of different harmonic conversion paths, and realize the simultaneous output of fundamental frequency light to deep ultraviolet light (266nm) and near ultraviolet light (355nm). The two driving lights are matched to excite different resonance modes of the target unit, further expanding the band coverage of higher harmonics.

[0081] Chiral Enhancement Nonlinearity Principle: The chiral supramolecular structure assembled from quantum dots and DNA breaks the centrosymmetry constraint, enabling even-order nonlinear polarizability χ (2) It significantly enhances and improves the polarization purity of harmonics, achieving a polarization degree of over 95%, thus solving the problem of disordered polarization in traditional harmonic beams.

[0082] Industrial-grade stable control principle: In the hybrid control algorithm, MPC is responsible for global optimization (predicting the resonant state change within the next 50ms), fuzzy adaptive PID is responsible for fast response (handling sudden disturbances), and redundant control loops ensure that the system can still maintain more than 70% of its performance when a single sensor or actuator fails. The fault diagnosis module provides early warning of potential faults through data analysis, and the mean time between failures (MTBF) is increased to more than 1,000 hours.

[0083] 3. This embodiment has advantages over Embodiment 2:

[0084] Stability and reliability meet industrial-grade standards: Through active temperature control, airflow cooling, redundant design and fault diagnosis, the device can operate continuously for 72 hours without interruption, with power fluctuation ≤±2%, which is 33% more stable than Example 2, meeting the continuous operation requirements of industrial lithography, material surface modification and other applications.

[0085] Superior harmonic performance: The chiral supramolecular structure enables the polarization degree of higher harmonics to reach 95%, which is significantly improved compared to 80% in Example 2. At the same time, multi-wave vector matching achieves continuous harmonic coverage in the 20-60nm band, and the uniformity of harmonic intensity is improved by 50%.

[0086] Enhanced environmental resistance and maintainability: The industrial-grade PLC controller and sealed optical cavity design enable the device to operate in harsh environments with temperatures ranging from -10 to 45°C and humidity from 20% to 85%. The remote monitoring function supports remote operation and maintenance, reducing operating costs.

[0087] Enhanced safety features: The system includes laser safety interlock, over-temperature and over-pressure protection, and fault alarm functions, meeting industrial safety standards, while Examples 1 and 2 only meet laboratory safety requirements.

[0088] Example 4: Method Example

[0089] This embodiment provides a method for generating higher harmonics based on the above-described device, the specific steps of which are as follows:

[0090] Turn on the laser source and preheat for 30 minutes until the output is stable. Set the output parameters (wavelength, pulse width, repetition frequency) to ensure that the femtosecond laser pulse meets the incident requirements of the frequency conversion module.

[0091] Initialize the collaborative control unit, set the first resonance condition threshold (quasi-phase matching wavelength deviation ≤ ±0.1nm) and the second resonance condition threshold (transmitted light mode distortion coefficient ≤ 0.1), and configure the control algorithm parameters (sampling period, prediction step size, etc. of the state space controller).

[0092] The control frequency conversion module enters the working state, adjusts the initial voltage to make the superlattice crystal meet the quasi-phase matching condition, converts the femtosecond laser pulse into a deep ultraviolet driving pulse, and records the reference value of the dual feedback signal in the initial state.

[0093] A deep ultraviolet driving pulse is incident on the excitation target unit, adjusting the initial strain of the photonic crystal fiber so that the excitation target unit simultaneously satisfies the photonic bandgap resonance and quantum energy level resonance, generating the target's higher harmonics;

[0094] The collaborative control unit collects the first feedback signal (deep ultraviolet driving pulse wavelength) and the second feedback signal (transmitted light mode characteristics) in real time and compares and analyzes them with the reference value.

[0095] Based on the comparison results, the optimal adjustment amount is calculated through a multivariable control model, and control command 1 and control command 2 are generated to adjust the superlattice crystal voltage of the frequency conversion module and the fiber strain of the excitation target unit, respectively, to dynamically adapt the coupling relationship of the dual resonance condition and maintain stable output of high-order harmonics.

[0096] When the feedback signal is detected to exceed the set threshold (abnormal operating condition), the control algorithm automatically switches to the fault response mode, increases the adjustment range and enables redundant control channels. If the fault lasts for 10 seconds, the safety interlock is activated, the laser source is turned off and an alarm signal is issued.

[0097] After the operation is completed, first turn off the laser source, and after the optical components have cooled to room temperature, turn off the collaborative control unit and auxiliary modules (temperature control, cooling, etc.).

[0098] This method achieves dynamic locking of dual resonance conditions through a closed-loop process of "initialization-monitoring-coordinated adjustment-anomaly response," fully covering all the step features of claim 10, and complementing the above three device embodiments, thus fully supporting the limitation of the scope of protection of the method in the claims.

[0099] 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 claimed invention.

Claims

1. A device for generating high-order harmonics based on short wavelengths, characterized in that: include: A laser source used to generate femtosecond laser pulses; The frequency conversion module is used to convert femtosecond laser pulses into short-wavelength drive pulses; Excitation target unit, used to generate high-order harmonics using short-wavelength driving pulses; Collaborative control unit; The operating state of the frequency conversion module satisfies the first resonance condition, and the operating state of the excitation target unit satisfies the second resonance condition. The first physical parameter on which the first resonance condition depends and the second physical parameter on which the second resonance condition depends are coupled to each other through the wavelength of the short-wavelength driving pulse; The collaborative control unit is configured to: synchronously acquire the state information of the first resonance condition and the second resonance condition by monitoring the first feedback signal and the second feedback signal related to the wavelength, and generate control commands according to the coupling relationship of the state information to synchronously adjust the working parameters of the frequency conversion module and the excitation target unit, so that the device is locked in a collaborative working state in which the first resonance condition and the second resonance condition are simultaneously optimized.

2. The high-order harmonic generation device based on short wavelength according to claim 1, characterized in that: The first resonance condition is a quasi-phase matching condition. The frequency conversion module contains an electro-optically tuned superlattice crystal whose polarization period Λ satisfies the relationship between the wavelength λ of the femtosecond laser pulse: λ = 2• n_eff • Λ, where n_eff is the effective refractive index. The second resonance condition includes the photonic bandgap resonance condition, wherein the excitation target unit comprises a hollow photonic crystal fiber, and the center wavelength of its bandgap is matched with the wavelength of the short-wavelength driving pulse; The co-control unit is configured to fine-tune the quasi-phase matching condition by adjusting the voltage applied to the electro-optically tuned superlattice crystal, and to simultaneously fine-tune the photonic bandgap resonance condition by adjusting the strain applied to the photonic crystal fiber.

3. The high-order harmonic generation device based on short wavelength according to claim 2, characterized in that: The second resonance condition also includes a quantum level resonance condition, and the excitation target unit further includes a quantum dot placed in a photonic crystal fiber, wherein the excitation energy level of the quantum dot is matched with the photon energy of the short-wavelength driving pulse.

4. The high-order harmonic generation device based on short wavelength according to claim 3, characterized in that: The first exciton absorption peak energy E_ex and the photon energy E_DUV of the short-wavelength driving pulse of the quantum dot satisfy: |E_DUV - E_ex| / E_ex < 5%.

5. The high-order harmonic generation device based on short wavelength according to claim 1, characterized in that: The collaborative control unit obtains a first feedback signal by monitoring the wavelength jitter of the short-wavelength drive pulse, and obtains a second feedback signal by monitoring the mode characteristics change of the drive pulse transmitted from the excitation target unit.

6. The high-order harmonic generation device based on short wavelength according to claim 2, characterized in that: The collaborative control unit synchronously adjusts at least two parameters, including the output wavelength of the laser source, the voltage applied to the superlattice crystal, and the strain applied to the photonic crystal fiber, according to the control command, and the adjustment range is dynamically adapted according to the coupling relationship between the first feedback signal and the second feedback signal.

7. The high-order harmonic generation device based on short wavelength according to claim 1, characterized in that: The collaborative control unit includes a state space controller, which generates the control commands based on the coupling relationship; The state space controller has a control cycle of less than 10 milliseconds and can suppress the long-term power fluctuation of the target high-order harmonics output by the device to within ±3%, of which long-term refers to continuous operation for no less than 4 hours.

8. A method for generating high-order harmonics based on short wavelengths, characterized in that, include: Synchronization acquisition steps: The first feedback signal characterizing the first resonance condition state satisfied by the working state of the frequency conversion module and the second feedback signal characterizing the second resonance condition state satisfied by the working state of the excitation target unit are acquired synchronously, wherein the first resonance condition and the second resonance condition are coupled to each other through the wavelength of the short-wavelength driving pulse. Coupling processing step: Input the first feedback signal and the second feedback signal into the multivariable control model, which characterizes the mutual influence relationship between the first resonance condition and the second resonance condition; Collaborative execution steps: Based on the output of the multivariable control model, at least two control commands are generated synchronously and sent to the frequency conversion module and the excitation target unit respectively to adjust their operating parameters, so that the frequency conversion module and the excitation target unit maintain a collaborative working state in which both the first resonance condition and the second resonance condition are locked.

9. A method for generating higher harmonics based on short wavelengths according to claim 8, characterized in that: The multivariable control model in the coupling process is a state-space model established in advance by identifying the device system.

10. A method for generating higher harmonics based on short wavelengths according to claim 8, characterized in that: In the coordinated execution step, the phase matching condition is fine-tuned by adjusting the voltage applied to the electro-optic crystal in the frequency conversion module, and the bandgap condition is fine-tuned by simultaneously adjusting the strain of the photonic crystal fiber in the excitation target unit.

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