Cascade gas target higher harmonic enhancement device and method based on Gouy phase regulation and control

Abstract

The invention provides a cascaded gas target higher harmonic enhancement device and method based on Gouy phase regulation and control. According to the higher harmonic coherent amplification method based on Gouy phase regulation and control and adopting the multiple cascaded gas targets, a cascaded gas target module scheme is adopted, and the Gouy phase of specific-order gas higher harmonics is regulated and controlled by regulating and controlling the relative distance between the multiple gas targets, so that the high-order gas higher harmonics are amplified. And finally, gas higher harmonics, especially specific-order harmonics, are enhanced. The method is not limited by driving laser single pulse energy, and the energy of the generated attosecond pulse sequence can be improved. Compared with a traditional multi-gas-target scheme, the method has the advantages that the phase of specific-order gas higher harmonics can be accurately regulated and controlled, enhancement of different-order harmonics is achieved, and help is provided for research in the fields of ultrafast electron dynamics, attosecond nonlinear physics and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-order harmonic generation, attosecond pulses and extreme ultraviolet light sources, and specifically relates to a cascade gas target high-order harmonic enhancement device and method based on Gouy phase regulation. Background Art

[0002] In the microscopic world, electrons are very important microscopic particles. The movement of electrons determines many microscopic properties of matter. The time scale of electron movement is in the attosecond level (10 -18 Seconds), in order to observe the movement of electrons, attosecond pulses are needed. An effective method to obtain attosecond pulses is gas high-order harmonic generation, which is a high-order nonlinear optical effect of the interaction between high-intensity driving lasers and rare gas atoms. It can produce a comb-shaped harmonic with a cutoff energy of tens of electron volts or even higher, which appears as only odd harmonics in the frequency domain. High-order harmonics appear in the time domain as a sequence of attosecond pulses separated by half an optical cycle. People can use certain isolated attosecond pulse gating methods to separate isolated attosecond pulses from the attosecond pulse sequence. Attosecond pulses can be used to detect ultrafast electron dynamics, and have very important application value in the fields of attosecond pump-probe, attosecond transient absorption spectroscopy, etc.

[0003] However, the gas high-order harmonic generation process has the problem of low conversion efficiency, resulting in low energy of attosecond pulses, which limits the development of attosecond nonlinear physics and other fields. At present, scientific research usually adopts the method of increasing the energy of the driving laser single pulse to obtain high-energy attosecond pulses. Due to the difficulty in developing high-energy femtosecond lasers, the development of high-energy attosecond pulses has been slow.

[0004] In addition to directly increasing the single pulse energy of the driving laser, another idea is to enhance the generated attosecond pulses. Using multiple gas targets to generate coherently enhanced high-order harmonics and then obtain enhanced attosecond pulse sequences is an effective method. In domestic and foreign research, the multi-gas target coherent enhancement scheme is usually difficult to control the phase of high-order harmonics, making it a problem to accurately control the coherent enhancement between high-order harmonics generated by multiple gas targets. Summary of the invention

[0005] Therefore, the purpose of the present invention is to overcome the defects in the prior art and provide a cascade gas target high-order harmonic enhancement device and method based on Gouy phase regulation. The high-order harmonic coherent amplification method based on Gouy phase regulation of the present invention using multiple cascade gas targets adopts a cascade gas target module solution, and by adjusting the relative distance between multiple gas targets, the Gouy phase of specific-order gas high-order harmonics is regulated, and finally the gas high-order harmonics, especially specific-order harmonics, are enhanced. This method is not limited by the energy of a single pulse of a driving laser, and can increase the energy of the generated attosecond pulse sequence. Compared with the traditional cascade gas target module solution, the method of the present invention can accurately regulate the phase of specific-order gas high-order harmonics, achieve the enhancement of harmonics of different orders, and provide assistance for research in fields such as ultrafast electron dynamics and attosecond nonlinear physics.

[0006] Before describing the present invention, the terms used in this article are defined as follows:

[0007] The term "Rayleigh distance" means: In optics and laser science, the Rayleigh distance or Rayleigh length or Rayleigh range refers to the distance along the direction of travel of a beam of light from its waist to a cross-section whose area is twice the area of ​​the waist, where the radius of the cross-section is approximately 1.414 times the radius of the waist.

[0008] The term "Gouy phase" refers to: a geometric phase introduced by the wavefront difference between a Gaussian beam and a plane wave. The Gouy phase at a certain point in the propagation direction of the beam is equal to the inverse tangent function of the ratio of the distance from the point to the beam waist to the Rayleigh distance of the Gaussian beam. The Gouy phase of a certain order of high-order harmonics generated at this point is equal to the Gouy phase of the driving beam at this point multiplied by the order of the harmonic.

[0009] The term "backing vacuum pump" refers to: a diaphragm pump, a screw pump, a rotary vane pump, a Roots pump, or a combination thereof, which can reduce the vacuum degree of the vacuum chamber to 1×10 -3 mbar level, reaching high vacuum level (1×10 -3 mbar-1×10 - 7 mbar), providing a fore-vacuum environment for the subsequent ultra-high vacuum pump.

[0010] The term "ultra-high vacuum pump" refers to: a turbomolecular vacuum pump, an ion vacuum pump, a titanium sublimation vacuum pump, or a combination thereof, which can further reduce the vacuum degree of the vacuum chamber from the fore-stage vacuum degree described in the term "fore-stage vacuum pump" to 1×10 -8 mbar to 1×10 -11 mbar level, reaching ultra-high vacuum level (1×10 -8 mbar-1×10-11 mbar).

[0011] The term "near-infrared band" refers to electromagnetic waves between visible light (VIS) and mid-infrared light (MIR). According to the definition of ASTM (American Society for Testing and Materials), it refers to electromagnetic waves with a wavelength range of 780 to 2526 nm. It is customary to divide the near-infrared region into two regions: near-infrared short-wave (780 to 1100 nm) and near-infrared long-wave (1100 to 2526 nm).

[0012] To achieve the above object, the first aspect of the present invention provides a cascade gas target high-order harmonic enhancement device based on Gouy phase control, the cascade gas target high-order harmonic enhancement device comprising:

[0013] a femtosecond drive laser for generating a drive laser;

[0014] A focusing module for converging the driving laser into a focused beam;

[0015] Cascade gas target module for generating and controlling the phase of high-order harmonics; and

[0016] Terminals for characterization and / or application;

[0017] Preferably, the cascade gas target high-order harmonic enhancement device further comprises: a vacuum chamber device and a rare gas generator;

[0018] More preferably, the focusing module, the cascade gas target module and the terminal are located in the vacuum chamber device.

[0019] According to the first aspect of the present invention, the cascade gas target high harmonic enhancement device, wherein:

[0020] The central wavelength of the femtosecond driving laser is in the near-infrared band, and the wavelength range of the near-infrared band is preferably 780nm to 2526nm, more preferably 780nm to 1100nm, and further preferably 780nm to 820nm;

[0021] The output pulse width of the femtosecond driven laser is 100fs to 300fs, preferably 50fs to 100fs, more preferably 30fs to 50fs;

[0022] The single pulse energy of the femtosecond driven laser is 0.1mJ to 20mJ, preferably 0.1mJ to 10mJ, more preferably 0.1mJ to 5mJ; and / or

[0023] The femtosecond driven laser is selected from one or more of the following: a femtosecond chirped pulse amplifier, a femtosecond laser oscillator, a femtosecond optical parametric amplifier, a femtosecond optical parametric chirped pulse amplifier, preferably a femtosecond chirped pulse amplifier or a femtosecond optical parametric chirped pulse amplifier, and most preferably a femtosecond chirped pulse amplifier.

[0024] According to the first aspect of the present invention, the cascade gas target high harmonic enhancement device, wherein:

[0025] The focusing module is selected from one or more of the following combinations: a spherical concave lens, a spherical concave reflector, an off-axis parabolic mirror, a tire mirror, an ellipsoidal concave reflector, an ellipsoidal concave lens, a cylindrical concave reflector, and a cylindrical concave lens, preferably selected from one or more of the following combinations: a spherical concave lens, a spherical concave reflector, and an off-axis parabolic mirror, and most preferably a spherical concave reflector; and / or

[0026] The rare gas generator includes a steel cylinder, a pressure reducing valve and a rare gas pipeline. One end of the rare gas pipeline is connected to the steel cylinder through the pressure reducing valve, and the other end of the rare gas pipeline is connected to the vacuum chamber device, and sprays rare gas as a high-order harmonic generating medium.

[0027] According to the cascade gas target high-order harmonic enhancement device of the first aspect of the present invention, the cascade gas target module comprises two or more cascaded gas targets and an electric translation stage; wherein:

[0028] Each of the gas targets is mounted on a respective independent electric translation stage to independently achieve movement in three dimensions.

[0029] According to the first aspect of the present invention, the cascade gas target high harmonic enhancement device, wherein:

[0030] The gas target is selected from one or more of the following: a continuous gas pool, a pulsed gas pool, a gas nozzle, a semi-infinite gas target, preferably selected from one or more of the following: a continuous gas pool, a pulsed gas pool, a gas nozzle, and most preferably a pulsed gas pool; and / or

[0031] The rare gas is selected from one or more of the following: helium, neon, argon, krypton, xenon, preferably selected from one or more of the following: neon, argon, krypton, and most preferably argon.

[0032] According to the first aspect of the present invention, the cascade gas target high harmonic enhancement device, wherein:

[0033] The gas target is arranged within the Rayleigh distance of the focused light beam;

[0034] The waist position of the focused light beam is the focus, and the Gouy phase of the focus is preferably zero; and / or

[0035] The distance between each of the gas targets and the focus is 0 to 2 Rayleigh distances before the focus and / or 0 to 2 Rayleigh distances after the focus, preferably 0.3 to 1.5 Rayleigh distances before the focus and / or 0.3 to 1.5 Rayleigh distances after the focus, more preferably 0.5 to 1 Rayleigh distance before the focus and / or 0.5 to 1 Rayleigh distance after the focus;

[0036] Preferably, the laser peak power density at the position where the gas target is placed is greater than the generation threshold of the laser peak power density of the argon high harmonics, and more preferably greater than 1×10 14 W / cm 2 .

[0037] According to the cascade gas target high-order harmonic enhancement device of the first aspect of the present invention, the vacuum chamber device comprises: a vacuum chamber, a vacuum pipeline and a vacuum pump; wherein,

[0038] The vacuum chamber and the vacuum pipeline are connected via a vacuum gate valve;

[0039] The vacuum degree of the vacuum chamber is 1×10 -6 mbar~1×10 -11 mbar, preferably 1×10 -7 mbar~1×10 -9 mbar, most preferably 1×10 -8 mbar;

[0040] The vacuum chamber is selected from one or more of the following: a circular vacuum chamber, a square vacuum chamber, a horizontal vacuum chamber, and a spherical vacuum chamber, preferably selected from one or more of the following: a circular vacuum chamber, a square vacuum chamber, and a horizontal vacuum chamber, more preferably a circular vacuum chamber and / or a horizontal vacuum chamber;

[0041] The vacuum pipe is selected from one or more of the following: a cylindrical pipe, a welded corrugated pipe, a formed corrugated pipe, and a small corrugated pipe, preferably selected from one or more of the following: a cylindrical pipe, a welded corrugated pipe, and a formed corrugated pipe, more preferably a cylindrical pipe and / or a formed corrugated pipe;

[0042] The vacuum pump comprises a fore vacuum pump and an ultra-high vacuum pump, wherein the fore vacuum pump is preferably selected from one or more of the following: a diaphragm pump, a screw pump, a rotary vane pump, a Roots pump, more preferably a diaphragm pump or a screw pump, and most preferably a diaphragm pump; the ultra-high vacuum pump is preferably selected from one or more of the following: a turbomolecular vacuum pump, an ion vacuum pump, a titanium sublimation vacuum pump, more preferably a turbomolecular vacuum pump or an ion vacuum pump, and most preferably a turbomolecular vacuum pump;

[0043] Preferably, the focusing module and the cascade gas target module are located in the same vacuum chamber or in two different vacuum chambers, more preferably in the same vacuum chamber.

[0044] According to the cascade gas target high-order harmonic enhancement device of the first aspect of the present invention, the terminal comprises:

[0045] Characterization terminals for measuring the spectrum, average pulse duration and / or energy of high harmonics; and

[0046] Application terminal;

[0047] in,

[0048] The representation terminal and the application terminal are switched or used in parallel;

[0049] The characterization terminal is selected from one or more of the following: an extreme ultraviolet spectrometer system, a time-of-flight spectrometer system, a photoelectron detector, an extreme ultraviolet vacuum camera, and a Shack-Hartmann wavefront sensor, preferably selected from one or more of the following: an extreme ultraviolet spectrometer system, a time-of-flight spectrometer system, and a photoelectron detector, and more preferably an extreme ultraviolet spectrometer system and / or a time-of-flight spectrometer system;

[0050] The application terminal is selected from one or more of the following: a transient absorption spectroscopy system, a light emission electron microscope system, an angle-resolved photoelectron spectroscopy system, a cold target recoil ion momentum spectrometer system, and a velocity imaging spectrometer system, preferably selected from one or more of the following: a transient absorption spectroscopy system, a light emission electron microscope system, an angle-resolved photoelectron spectroscopy system, and a cold target recoil ion momentum spectrometer system, more preferably a transient absorption spectroscopy system and / or an angle-resolved photoelectron spectroscopy system;

[0051] Preferably, the characterization terminal and the application terminal are located in different vacuum chambers.

[0052] A second aspect of the present invention provides a method for enhancing high-order harmonics, the method comprising using the device described in the first aspect to enhance high-order harmonics;

[0053] Preferably, the method comprises the following steps:

[0054] The femtosecond driving laser generates a driving laser, which passes through the focusing module and converges into a focused light beam. The first gas target after cascade inflation generates high-order harmonics. The high-order harmonics and the driving laser work together at the second gas target to generate extreme ultraviolet photon-assisted high-order harmonics. The extreme ultraviolet photon-assisted high-order harmonics and the first gas target produce high-order harmonics that are coherently superimposed. When the number of gas targets is preferably greater than 2, the driving laser and the coherently superimposed high-order harmonics generated by the previous gas target jointly act on the extreme ultraviolet photon-assisted gas high-order harmonics generation process at the second gas target and subsequent gas targets. The extreme ultraviolet photon-assisted high-order harmonics and the coherently superimposed high-order harmonics generated by the previous gas target are superimposed again to finally obtain enhanced high-order harmonics, which are propagated to the characterization terminal and / or the application terminal for measurement.

[0055] According to the method of the second aspect of the present invention, for high-order harmonics of different orders, the method further comprises: enhancing high-order harmonics of different orders by adjusting the distance between each of the gas targets and the focus.

[0056] The present invention is a universal high-order harmonic coherence enhancement method based on Gouy phase regulation and using multiple gas targets. By placing multiple gas targets within one to two Rayleigh distances of a focused laser and changing the relative distances between the multiple gas targets, high-energy high-order harmonics are generated.

[0057] According to a preferred embodiment of the present invention, the gas high-order harmonic enhancement device of the present invention includes: a femtosecond driven laser for generating gas high-order harmonics, a vacuum cavity and pipelines, a vacuum pump system, a focusing system, a vacuum electric translation stage, a multi-gas target structure, a rare gas, and a characterization terminal or an application terminal.

[0058] In particular, the above-mentioned femtosecond driven laser generally refers to a femtosecond chirped pulse amplifier with a single pulse energy in the millijoule range, a repetition frequency usually in the kilohertz range, an output pulse width less than 50fs, and a central wavelength in the near-infrared band.

[0059] Furthermore, the vacuum cavity includes a circular cavity, a square cavity, a horizontal cavity and a combination thereof, and the vacuum pipe includes a cylindrical pipe, a welded bellows, a formed bellows and a combination thereof. Each vacuum cavity and the vacuum pipe are connected with a vacuum gate valve to ensure that each vacuum cavity can be independently evacuated.

[0060] Furthermore, the vacuum pump system uses a mechanical pump as a front vacuum pump and combines it with an ultra-high vacuum pump to achieve 1×10 -8 The vacuum degree is in the mbar range. Ultra-high vacuum pumps include: turbomolecular pumps, ion pumps, titanium sublimation pumps and their combined systems.

[0061] Furthermore, the focusing system includes: a spherical mirror, an off-axis parabolic mirror, a tire mirror, an ellipsoidal mirror, a cylindrical mirror and a combination thereof, which is used to focus the driving laser so that the laser peak power density at the multi-gas target placement position meets or exceeds the conditions for generating gas high-order harmonics.

[0062] Furthermore, the vacuum electric translation stage has an adjustment accuracy of less than 0.1 mm, a stroke of more than 50 mm and a reset function, and is used to adjust the relative positions of various components in the vacuum chamber.

[0063] Furthermore, the multi-gas target is two or more specially placed gas targets, and the gas target includes: a continuous gas pool, a pulsed gas pool, a gas nozzle and a combination system thereof, which is used to generate gas high-order harmonics. Each of the gas targets is mounted on a separate electric displacement stage, so that each gas target can independently and non-interferingly achieve three-dimensional movement of "up and down", "left and right", and "front and back". The reference planes of "up and down", "left and right", and "front and back" mentioned here and below refer to the planes perpendicular to the light propagation direction inside the vacuum chamber.

[0064] Furthermore, the rare gas generator is composed of a steel cylinder, a pressure reducing valve and a rare gas pipeline. The steel cylinder is filled with rare gas. The pressure reducing valve is used to connect the steel cylinder to one end of the rare gas pipeline. The other end of the rare gas pipeline is connected to the vacuum chamber where the cascade gas target module is located. The rare gas pipeline inside the vacuum chamber is connected to the cascade gas target module, and the rare gas is sprayed as a medium for generating high-order harmonics. By controlling the indication of the pressure reducing valve, the gas pressure in the cascade gas target module can be regulated, and the gas pressure regulation range is 0.05bar-10bar.

[0065] The rare gas used for generating gas high-order harmonics includes one of helium, neon, argon, krypton and xenon.

[0066] Furthermore, the characterization terminal is used to measure the spectrum, average pulse duration or energy of gas high-order harmonics, including: an extreme ultraviolet spectrometer system, a time-of-flight spectrometer system, a photoelectron detector and a combination system thereof. 1. The extreme ultraviolet spectrometer system includes an extreme ultraviolet flat-field variable-ruled concave grating, a microchannel plate, a fluorescent screen, and a charge-coupled device camera. Among them, the extreme ultraviolet flat-field variable-ruled concave grating is used to split the generated high-order harmonics according to the wavelength size, and the two gratings are switched. The wavelength splitting range is 5nm to 20nm or 10nm to 60nm, which can be selected according to the order of the actual generated high-order harmonics; the microchannel plate is used to convert the high-order harmonics into electrical signals; the fluorescent screen is used to convert the electrical signals into fluorescent signals; the charge-coupled device camera is used to receive the fluorescent signals on the fluorescent screen. 2. The time-of-flight spectrometer system includes a pump-probe optical path, a gas nozzle, a rare gas, a time-of-flight spectrometer, and a signal acquisition system. The pump-probe method is used to measure the momentum distribution of the ionized rare gas electrons by the pump light and the probe light at different time delays, which is used to invert the average pulse duration of the high-order harmonics, i.e., the attosecond pulse sequence, and then obtain the average pulse duration of the high-order harmonics. 3. The photoelectron detector consists of a photoelectric probe and an ammeter, and is used to measure the energy of the high-order harmonics.

[0067] Furthermore, the application terminal is a practical application system of high-order harmonics, which can be switched or used in parallel with the characterization terminal, including: a transient absorption spectroscopy system, a light emission electron microscope system, an angle-resolved photoelectron spectroscopy system, a cold target recoil ion momentum spectrometer system and one of their combined systems.

[0068] In the scheme of the present invention for enhancing gas high-order harmonics by using multiple gas targets based on Gouy phase control: after the driving laser is reflected by a focusing mirror with suitable focusing parameters, focusing is achieved in a vacuum chamber, and multiple gas targets are placed within one to two Rayleigh distances of the focused light beam. By adjusting the distances of the multiple gas targets relative to the focus, Gouy phase control of a specific order is achieved for the gas high-order harmonics generated by each gas target. Furthermore, after the coherent superposition of the gas high-order harmonics generated by the multiple gas targets, the overall enhancement of the gas high-order harmonics and the substantial enhancement of the selected order are finally achieved. The enhanced gas high-order harmonics can be propagated to the characterization terminal for the measurement of the spectrum, average pulse duration and energy, or propagated to the application terminal for related experiments. This method can be used for the generation of high-energy attosecond pulses, and can be widely used in attosecond physics, attosecond transient absorption photonics, materials science and other fields, and has good application prospects.

[0069] The present invention provides a method for enhancing high-order harmonics of multiple gas targets based on Gouy phase regulation, including: a femtosecond driven laser, a vacuum cavity and pipeline, a vacuum pump system, a focusing system, a vacuum electric translation stage, a multi-gas target structure, a rare gas, a characterization terminal or an application terminal. The present invention adopts a multi-gas target scheme, and by regulating the relative distance between multiple gas targets, the Gouy phase of the selected order gas high-order harmonics is controlled, thereby enhancing the gas high-order harmonics, especially the selected order harmonics. The present invention has a simple structure, simple operation, compact design, and obvious effect. It is not limited by the driving laser energy, and can enhance harmonics of different orders. It has the advantages of high energy, wide spectrum, wide applicability, good repeatability, etc. It can be applied to ultrafast light field physical property detection, transient absorption spectroscopy measurement, attosecond physics, materials science and other fields, and has good application prospects and scientific research value.

[0070] Compared with the prior art, the cascade gas target high-order harmonic enhancement device and method based on Gouy phase control of the present invention can have but are not limited to the following beneficial effects:

[0071] 1. The high-harmonic coherent amplification method based on Gouy phase control and using multiple cascaded gas targets of the present invention adopts a multi-gas target scheme, and controls the Gouy phase of specific-order gas high-order harmonics by controlling the relative distance between multiple gas targets, and finally enhances gas high-order harmonics, especially specific-order harmonics. This method is not limited by the energy of a single pulse of a driving laser, and can increase the energy of the generated attosecond pulse sequence. Compared with the traditional multi-gas target scheme, the method of the present invention can accurately control the phase of specific-order gas high-order harmonics, realize the enhancement of harmonics of different orders, and provide help for research in fields such as ultrafast electron dynamics and attosecond nonlinear physics.

[0072] 2. The present invention has a simple structure, simple operation, compact design, and obvious effect. It is not limited by the driving laser energy and can enhance harmonics of different orders. It has the advantages of high energy, wide spectrum, wide applicability, and good repeatability. It can be applied to ultrafast light field physical property detection, transient absorption spectroscopy measurement, attosecond physics, materials science and other fields, and has good application prospects and scientific research value. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, wherein:

[0074] Figure 1 The schematic diagram of the structure of the cascade gas target high-order harmonic enhancement device based on Gouy phase regulation of the present invention is shown.

[0075] Figure 2 A schematic structural diagram of the arrangement of multi-cascade gas targets in Example 1 of the present invention is shown.

[0076] Figure 3 The diagram shows the enhanced gas high-harmonic spectrum intensity obtained by the cascade gas target high-harmonic enhancement device based on Gouy phase control in Example 1 of the present invention.

[0077] Figure 4 A schematic structural diagram of the arrangement of multi-cascade gas targets in Example 2 of the present invention is shown.

[0078] Figure 5 The diagram shows the enhanced gas high-order harmonic spectrum intensity obtained by the cascade gas target high-order harmonic enhancement device based on Gouy phase regulation in Example 2 of the present invention.

[0079] Figure 6 A schematic diagram of the structure of the multi-cascade gas target arrangement in Example 3 of the present invention is shown.

[0080] Figure 7 The diagram shows the enhanced gas high-order harmonic spectrum intensity obtained by the cascade gas target high-order harmonic enhancement device based on Gouy phase regulation in Example 3 of the present invention.

[0081] Figure 8 A schematic structural diagram of the arrangement of multi-cascade gas targets in Example 4 of the present invention is shown.

[0082] Fig. 9 A schematic structural diagram of the arrangement of multi-cascade gas targets in Example 5 of the present invention is shown.

[0083] Fig.10 A schematic diagram of the structure of the multi-cascade gas target arrangement in Example 6 of the present invention is shown.

[0084] Fig.11 A schematic diagram of the structure of the multi-cascade gas target arrangement in Example 7 of the present invention is shown.

[0085] Description of reference numerals:

[0086] 1. Femtosecond driven laser; 2. Focusing module; 3. Cascade gas target module; 4. Rare gas generator; 5. Characterization terminal; 6. Application terminal; 7. Vacuum chamber device; 8. Gas target No. 1 in Example 1; 9. Gas target No. 2 in Example 1; 10. Focus in Example 1; 11. Distance No. 1 in Example 1; 12. Distance No. 2 in Example 1; 13. Gas target No. 1 in Example 2; 14. Gas target No. 2 in Example 2; 15. Focus in Example 2; 16. Distance No. 1 in Example 2; 17. Distance No. 2 in Example 2; 18. Gas target No. 1 in Example 3; 19. Gas target No. 2 in Example 3; 20. Gas target No. 3 in Example 3; 21. Implementation The focus in Example 3; 22, the first distance in Example 3; 23, the second distance in Example 3; 24, the third distance in Example 3; 25, the first gas target in Example 4; 26, the second gas target in Example 4; 27, the third gas target in Example 4; 28, the fourth gas target in Example 4; 29, the focus in Example 4; 30, the first distance in Example 4; 31, the second distance in Example 4; 32, the third distance in Example 4; 33, the fourth distance in Example 4; 34, the first gas target in Example 5; 35, the second gas target in Example 5; 36, the third gas target in Example 5; 37, the fourth gas target in Example 5; 38, the fifth gas target in Example 5 No. 1 gas target; 39, the focus in Example 5; 40, the No. 1 distance in Example 5; 41, the No. 2 distance in Example 5; 42, the No. 3 distance in Example 5; 43, the No. 4 distance in Example 5; 44, the No. 5 distance in Example 5; 45, the No. 1 gas target in Example 6; 46, the No. 2 gas target in Example 6; 47, the No. 3 gas target in Example 6; 48, the No. 4 gas target in Example 6; 49, the No. 5 gas target in Example 6; 50, the No. 6 gas target in Example 6; 51, the No. 7 gas target in Example 6; 52, the No. 8 gas target in Example 6; 53, the No. 9 gas target in Example 6; 54, the No. 10 gas target in Example 6; 55, the focus in Example 6 point; 56, No. 1 distance in Example 6; 57, No. 2 distance in Example 6; 58, No. 3 distance in Example 6; 59, No. 4 distance in Example 6; 60, No. 5 distance in Example 6; 61, No. 6 distance in Example 6; 62, No. 7 distance in Example 6; 63, No. 8 distance in Example 6; 64, No. 9 distance in Example 6; 65, No. 10 distance in Example 6; 66, No. 1 gas target in Example 7; 67, No. 2 gas target in Example 7; 68, No. 3 gas target in Example 7; 69, No. 4 gas target in Example 7; 70, No. 5 gas target in Example 7; 71, No. 6 gas target in Example 7; 72, No. 7 gas target in Example 7;73. Gas target No. 8 in Example 7; 74. Gas target No. 9 in Example 7; 75. Gas target No. 10 in Example 7; 76. Gas target No. 11 in Example 7; 77. Gas target No. 12 in Example 7; 78. Gas target No. 13 in Example 7; 79. Gas target No. 14 in Example 7; 80. Gas target No. 15 in Example 7; 81. Gas target No. 16 in Example 7; 82. Gas target No. 17 in Example 7; 83. Gas target No. 18 in Example 7; 84. Gas target No. 19 in Example 7; 85. Gas target No. 20 in Example 7; 86. Focus in Example 7; 87. Distance No. 1 in Example 7; 88. Distance No. 2 in Example 7; 89. Distance No. 3 in Example 7 90, the fourth distance in Example 7; 91, the fifth distance in Example 7; 92, the sixth distance in Example 7; 93, the seventh distance in Example 7; 94, the eighth distance in Example 7; 95, the ninth distance in Example 7; 96, the tenth distance in Example 7; 97, the eleventh distance in Example 7; 98, the twelveth distance in Example 7; 99, the thirteenth distance in Example 7; 100, the fourteenth distance in Example 7; 101, the fifteenth distance in Example 7; 102, the sixteenth distance in Example 7; 103, the seventeenth distance in Example 7; 104, the eighteenth distance in Example 7; 105, the nineteenth distance in Example 7; 106, the twentyth distance in Example 7. ; DETAILED DESCRIPTION

[0087] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings. However, it should be understood that these embodiments are only used for more detailed and specific description and should not be understood as limiting the present invention in any form.

[0088] This section generally describes the materials and test methods used in the experiments of the present invention. Although many materials and operating methods used to achieve the purpose of the present invention are well known in the art, the present invention is still described as detailed as possible. It is clear to those skilled in the art that in the context, if not specifically stated, the materials and operating methods used in the present invention are well known in the art.

[0089] It should be noted that the “multiple” mentioned in this patent means two or more.

[0090] Example 1

[0091] This embodiment is an exemplary description of the cascade gas target high-order harmonic enhancement device and method based on Gouy phase control of the present invention.

[0092] Figure 1It is a schematic diagram of an embodiment of the present invention for enhancing gas high-order harmonics. Figure 2 The figure shows in detail the arrangement of the multi-stage gas target 3. Figure 1 and Figure 2 As shown:

[0093] The cascade gas target high-order harmonic enhancement device based on Gouy phase regulation of the present invention includes: a femtosecond driven laser 1, a focusing module 2, a cascade gas target module 3, a rare gas generator 4, a characterization terminal 5, an application terminal 6, and a vacuum chamber device 7. The focusing module 2, the cascade gas target module 3, the characterization terminal 5 and the application terminal 6 are located in the vacuum chamber device 7. The vacuum chamber device includes: a vacuum chamber, a vacuum pipe and a vacuum pump; wherein the vacuum chamber and the vacuum pipe are connected by a vacuum gate valve. The focusing module 2 and the cascade gas target module 3 are located in the same vacuum chamber, and the characterization terminal 5 and the application terminal 6 are located in different vacuum chambers. The vacuum chamber used in this embodiment is a combination of a circular vacuum chamber and a horizontal vacuum chamber, the vacuum pipe is a combination of a cylindrical pipe and a shaped bellows, and the vacuum pump is a combination of a diaphragm pump and a vortex molecular pump.

[0094] The femtosecond driving laser 1 used to generate the driving laser has a central wavelength of 800nm, a pulse width of 40fs, a single pulse energy of 5mJ, and a repetition frequency of 1kHz. After the driving laser passes through the focusing module 2, it is converged in the vacuum chamber device 7. The vacuum chamber device 7 uses a vacuum pump system to maintain a high vacuum environment. In this embodiment, the vacuum degree of this part is 5×10 -8 mbar. Within the Rayleigh distance of the focused beam, a cascade gas target module 3 is placed. The focusing module 2 uses a spherical concave reflector.

[0095] In this embodiment, two gas targets are used to demonstrate the cascade gas target module 3. The two gas targets are placed as follows: Figure 2 As shown, gas target No. 1 8 and gas target No. 2 9 are independently mounted on a vacuum displacement table that can move freely in three dimensions, and both targets are placed within the Rayleigh distance of the focused light beam. The beam waist position of the focused light beam is the focus 10, and the Gouy phase at the focus 10 is zero. Distance No. 1 11 and distance No. 2 12 are the distances between gas target No. 1 8 and gas target No. 2 9 and the focus, respectively. Gas target No. 1 8 and gas target No. 2 9 are both connected to a rare gas generator to be filled with rare gas as a gaseous high-order harmonic generating medium. In this embodiment, the rare gas selected is argon, the gas pressure at the cascade gas target module 3 is 0.5 bar, and the selected gas target is a pulse gas pool.

[0096] When the focused light beam is incident on the gas-filled No. 1 gas target 8, a series of gas high-order harmonics is first generated at the No. 1 gas target 8, and the gas high-order harmonics and the driving laser are coaxially propagated to the No. 2 gas target 9. In the gas-filled No. 2 gas target 9, the gas high-order harmonics and the driving laser work together to generate gas high-order harmonics assisted by extreme ultraviolet photons, and the gas high-order harmonics assisted by extreme ultraviolet photons are coherently superimposed with the gas high-order harmonics generated in the No. 1 gas target 8 to obtain enhanced gas high-order harmonics. By changing the size of the No. 1 distance 11 and the No. 2 distance 12 respectively, the gas high-order harmonics of a specific order can be enhanced. In this embodiment, the size of the first distance 11 and the second distance 12 is set according to the enhancement of the 33rd order harmonic. The size of the first distance 11 is 0.95 Rayleigh distances before the focus 10, and the Gouy phase of the 33rd order harmonic at the corresponding first gas target is 8π. The size of the second distance 12 is 0.78 Rayleigh distances before the focus 10, and the Gouy phase of the 33rd order harmonic at the corresponding second gas target is 7π. Under this distance setting, the laser focusing peak power density at the first gas target 8 in this embodiment is 5.8×10 14 W / cm 2 The laser focusing peak power density at the second gas target 9 is 6×10 14 W / cm 2 , are both greater than the generation threshold of argon high-order harmonics.

[0097] After the enhanced gas high-order harmonics are generated in the cascade gas target module 3, the enhanced gas high-order harmonics can be transmitted to the characterization terminal 5 for measurement of high-order harmonic spectrum, average pulse width and energy. Further, the enhanced gas high-order harmonics can be transmitted to the application terminal 6 for experiments such as transient absorption spectroscopy, attosecond pump-probe, and solid ultrafast electron dynamics detection.

[0098] Figure 3 The figure is a spectrum intensity diagram of the gas high harmonics generated at each gas target when the cascade gas target module is arranged according to the embodiment. Figure 3 It can be seen that the intensity of the gas high-order harmonics generated at the second gas target 9 is significantly enhanced as a whole compared with that at the first gas target 8, and there is a certain cut-off zone expansion. The enhancement factor of the specially set 33rd-order high-order harmonic is about 4 times, which is significantly larger than other orders, proving that this scheme can enhance the intensity of gas high-order harmonics, especially the harmonic intensity of the selected order.

[0099] Furthermore, by changing the first distance 11 and the second distance 12, it is possible to enhance harmonics of different orders. Furthermore, by increasing the number of gas targets, it is possible to achieve higher magnification and wider spectrum gas high-order harmonic enhancement.

[0100] The high-order harmonic enhancement scheme of the cascade gas target module based on Gouy phase control described in this embodiment realizes the generation of gas high-order harmonics with higher energy, wider spectrum, and particularly high single-order intensity. The method of the present invention has a simple structure, simple operation, compact design, and obvious effect. It has the advantages of high energy, wide spectrum, wide applicability, good repeatability, etc. It can be applied to multidisciplinary fields such as ultrafast light field physical property detection, attosecond physics, condensed matter physics, etc., and has broad application prospects.

[0101] Example 2

[0102] This embodiment is another exemplary description of the cascade gas target high-order harmonic enhancement device and method based on Gouy phase control of the present invention.

[0103] The cascade gas target high-order harmonic enhancement device based on Gouy phase control of Example 2 is the same as Example 1 except for Table 1.

[0104] Table 1 Cascade gas target high harmonic enhancement device based on Gouy phase control in Example 2

[0105]

[0106] Specifically, in this embodiment, two gas targets are used to demonstrate the cascade gas target module 3. The two gas targets are placed as follows: Figure 4 As shown, the rare gas selected in this embodiment is argon, the gas pressure at the cascade gas target module 3 is 0.5 bar, and the selected gas target is a pulse gas pool.

[0107] Different from the first embodiment, the first distance 16 and the second distance 17 are set according to the enhancement of the 27th order harmonic. The first distance 16 is 0.84 Rayleigh distances before the focus 15, and the Gouy phase of the 27th order harmonic at the first gas target is 6π. The second distance 17 is 0.66 Rayleigh distances before the focus 15, and the Gouy phase of the 27th order harmonic at the second gas target is 5π. Under this distance setting, the laser focusing peak power density at the first gas target 13 in the present embodiment is 5.9×10 14 W / cm 2 The laser focusing peak power density at the second gas target 14 is 6.2×10 14 W / cm 2 , are both greater than the generation threshold of argon high-order harmonics.

[0108] When the focused light beam is incident on the inflated gas target No. 1 13, a series of gas high-order harmonics are first generated at the gas target No. 1 13, and the gas high-order harmonics are coaxially propagated with the driving laser to the gas target No. 2 14. In the inflated gas target No. 2 14, the gas high-order harmonics and the driving laser work together to generate gas high-order harmonics assisted by extreme ultraviolet photons. The gas high-order harmonics assisted by extreme ultraviolet photons are coherently superimposed with the gas high-order harmonics generated in the gas target No. 1 13 to obtain enhanced gas high-order harmonics.

[0109] After the enhanced gas high-order harmonics are generated in the cascade gas target module 3, the enhanced gas high-order harmonics can be transmitted to the characterization terminal 5 for measurement of high-order harmonic spectrum, average pulse width and energy. Further, the enhanced gas high-order harmonics can be transmitted to the application terminal 6 for experiments such as transient absorption spectroscopy, attosecond pump-probe, and solid ultrafast electron dynamics detection.

[0110] Figure 5 The figure is a spectrum intensity diagram of the gas high harmonics generated at each gas target when the cascade gas target module is arranged according to the embodiment. Figure 5 It can be seen that the intensity of the gas high-order harmonics generated at the second gas target 14 is significantly enhanced as a whole compared to that at the first gas target 13, and there is a certain cutoff zone expansion. The spectral intensity of the specially set 27th-order high-order harmonic is the strongest, and the enhancement factor is about 2.3 times, which proves that the scheme can enhance the intensity of gas high-order harmonics of different orders by changing the size of the first distance 16 and the second distance 17.

[0111] Furthermore, by increasing the number of gas targets, gas high-order harmonic enhancement with higher magnification and wider spectrum can be achieved.

[0112] The high-order harmonic enhancement scheme of the cascade gas target module based on Gouy phase control described in this embodiment achieves the generation of gas high-order harmonics with higher energy, wider spectrum and significantly enhanced harmonic intensity of different selected orders by changing the size of the first distance 16 and the second distance 17, compared with Example 1. It is further proved that the method of the present invention can enhance the intensity of gas high-order harmonics of different orders, has a simple structure, simple operation, compact design, obvious effect, has the advantages of high energy, wide spectrum, wide applicability, good repeatability, etc., and can be applied to transient absorption spectroscopy measurement, attosecond physics, material science and other multidisciplinary fields, and has broad application prospects.

[0113] Example 3

[0114] This embodiment is another exemplary description of the cascade gas target high-order harmonic enhancement device and method based on Gouy phase control of the present invention.

[0115] The cascade gas target high-order harmonic enhancement device based on Gouy phase control of Example 3 is the same as Example 1 except for Table 2.

[0116] Table 2 Cascade gas target high harmonic enhancement device based on Gouy phase control in Example 3

[0117]

[0118] In this embodiment, three gas targets are used to demonstrate the cascade gas target module 3. The three gas targets are arranged as follows: Figure 6 As shown, the rare gas selected in this embodiment is argon, the gas pressure at the cascade gas target module 3 is 0.5 bar, and the selected gas target is a pulse gas pool.

[0119] In this embodiment, the size of the first distance 22, the second distance 23 and the third distance 24 are set according to the enhancement of the 33rd order harmonic. The size of the first distance 22 is 0.95 Rayleigh distances before the focus 21, and the corresponding Gouy phase of the 33rd order harmonic at the first gas target is 8π. The size of the second distance 23 is 0.78 Rayleigh distances before the focus 21, and the corresponding Gouy phase of the 33rd order harmonic at the second gas target is 7π. The size of the third distance 24 is 0.51 Rayleigh distances before the focus 21, and the corresponding Gouy phase of the 33rd order harmonic at the third gas target is 5π. Under this distance setting, the laser focusing peak power density at the first gas target 18 in this embodiment is 5.8×10 14 W / cm 2 The laser focusing peak power density at the second gas target 19 is 6×10 14 W / cm 2 The laser focusing peak power density at the third gas target 20 is 6.4×10 14 W / cm 2 , are both greater than the generation threshold of argon high-order harmonics.

[0120] When the focused light beam is incident on the inflated gas target No. 18, a series of gas high-order harmonics are first generated at the gas target No. 18, and the gas high-order harmonics are coaxially propagated with the driving laser to the gas target No. 2 19. In the inflated gas target No. 2 19, the gas high-order harmonics and the driving laser work together to generate extreme ultraviolet photon-assisted gas high-order harmonics, and the extreme ultraviolet photon-assisted gas high-order harmonics are coherently superimposed with the gas high-order harmonics generated in the gas target No. 1 18. The coherently superimposed gas high-order harmonics and the driving laser coaxially propagate to the gas target No. 3 20. In the inflated gas target No. 3 20, the coherently superimposed gas high-order harmonics and the driving laser work together to generate extreme ultraviolet photon-assisted gas high-order harmonics, and the extreme ultraviolet photon-assisted gas high-order harmonics are coherently superimposed with the coherently superimposed gas high-order harmonics generated in the gas target No. 2 19 again to obtain enhanced gas high-order harmonics.

[0121] After the enhanced gas high-order harmonics are generated in the cascade gas target module 3, the enhanced gas high-order harmonics can be transmitted to the characterization terminal 5 for measurement of high-order harmonic spectrum, average pulse width and energy. Further, the enhanced gas high-order harmonics can be transmitted to the application terminal 6 for experiments such as transient absorption spectroscopy, attosecond pump-probe, and solid ultrafast electron dynamics detection.

[0122] Figure 7 The figure is a spectrum intensity diagram of the gas high harmonics generated at each gas target when the cascade gas target module is arranged according to the embodiment. Figure 7 It can be seen that the intensity of the gas high-order harmonics generated at the third gas target 20 is greatly enhanced as a whole compared with that at the first gas target 18, and there is a certain cutoff zone expansion. The spectral intensity of the specially set 33rd-order high-order harmonic is the strongest and the enhancement factor is the largest, which is about 7.4 times. This proves that by increasing the number of gas targets, the scheme can achieve higher magnification, wider spectrum, and stronger selected order intensity of gas high-order harmonic enhancement.

[0123] Furthermore, by changing the sizes of the first distance 22, the second distance 23 and the third distance 24, enhancement can be performed on harmonics of different orders.

[0124] Example 4

[0125] This embodiment is another exemplary description of the cascade gas target high-order harmonic enhancement device and method based on Gouy phase control of the present invention.

[0126] The cascade gas target high-order harmonic enhancement device based on Gouy phase regulation of Example 4 is the same as Example 1 except for Table 3.

[0127] Table 3 Cascade gas target high harmonic enhancement device based on Gouy phase control of Example 4

[0128]

[0129] When the number of gas targets is more than 3, as shown in Table 3, based on the same Goui phase control principle, the cascade gas target module 3 has the same high-order harmonic enhancement function.

[0130] The multi-stage gas target placement structure in the embodiment of the present invention is as follows Figure 8In this embodiment, the first distance 30 to the fourth distance 33 are set according to the enhancement of the 29th order harmonic, and the sizes of the first distance 30 to the fourth distance 33 are 0.22 Rayleigh distances after the focus, 0.46 Rayleigh distances after the focus, 0.76 Rayleigh distances after the focus, and 0.95 Rayleigh distances after the focus, respectively. The Gouy phases of the 29th order harmonics at the corresponding first to fourth gas targets are -4π, -5π, -6π, and -7π, respectively.

[0131] Under the parameter settings of this embodiment, enhanced gas high-order harmonics can be generated in the cascade gas target module 3, proving that after multiple gas targets are placed at the focus, there is still an enhancement effect of high-order harmonics, further illustrating the universality of this method.

[0132] Example 5

[0133] This embodiment is yet another exemplary description of the cascade gas target high-order harmonic enhancement device and method based on Gouy phase control of the present invention.

[0134] The cascade gas target high harmonic enhancement device based on Gouy phase regulation of Example 5 is the same as Example 1 except for Table 4. Based on the same Gouy phase regulation principle, the cascade gas target module 3 has the same high harmonic enhancement function.

[0135] Table 4 Cascade gas target high harmonic enhancement device based on Gouy phase control of Example 5

[0136]

[0137] The multi-stage gas target placement structure in the embodiment of the present invention is as follows Fig. 9 In this embodiment, the first distance 40 to the fifth distance 44 are set according to the enhancement of the 31st order harmonic, and the sizes of the first distance 40 to the fourth distance 44 are respectively 0.85 Rayleigh distance before the focus, 0.7 Rayleigh distance before the focus, 0 Rayleigh distance before the focus, 0.43 Rayleigh distance after the focus, and 0.55 Rayleigh distance after the focus. The corresponding Gouy phases of the 31st order harmonics at the first to fifth gas targets are -7π, -6π, 0, 4π, and 5π, respectively.

[0138] Under the parameter settings of this embodiment, enhanced gas high-order harmonics can be generated in the cascade gas target module 3, proving that placing multiple gas targets both before and after the focus can enhance the high-order harmonics, further illustrating the universality of this method.

[0139] Example 6

[0140] This embodiment is yet another exemplary description of the cascade gas target high-order harmonic enhancement device and method based on Gouy phase control of the present invention.

[0141] The cascade gas target high-order harmonic enhancement device based on Gouy phase control of Example 6 is the same as Example 1 except for the number of gas targets, specific enhancement order, gas target type, and the distance between each gas target and the focus. Based on the same Gouy phase control principle, the cascade gas target module 3 has the same high-order harmonic enhancement function.

[0142] The multi-stage gas target placement structure in the embodiment of the present invention is as follows Fig.10 As shown, in this embodiment, the number of gas targets is 10, the specific enhancement order is 41, and the type of gas target is a gas nozzle. In this embodiment, the sizes of the No. 1 distance 56 to the No. 10 distance 65 are respectively 0.96 Rayleigh distance before the focus, 0.7 Rayleigh distance before the focus, 0.5 Rayleigh distance before the focus, 0.32 Rayleigh distance before the focus, 0.15 Rayleigh distance before the focus, 0.15 Rayleigh distance after the focus, 0.32 Rayleigh distance after the focus, 0.50 Rayleigh distance after the focus, 0.70 Rayleigh distance after the focus, and 0.96 Rayleigh distance after the focus, and the corresponding Gouy phases of the 31st order harmonics at the No. 1 gas target 45 to the No. 10 gas target 54 are -10π, -8π, -6π, -4π, -2π, 2π, 4π, 6π, 8π, and 10π.

[0143] Under the parameter settings of this embodiment, enhanced gas high-order harmonics can be generated in the cascade gas target module 3, which proves that the device is not limited by the type of gas target and further illustrates the universality of this method.

[0144] Example 7

[0145] This embodiment is yet another exemplary description of the cascade gas target high-order harmonic enhancement device and method based on Gouy phase control of the present invention.

[0146] The cascade gas target high-order harmonic enhancement device based on Gouy phase control of Example 7 is the same as Example 1 except for the number of gas targets, specific enhancement order, gas target type, and the distance between each gas target and the focus. Based on the same Gouy phase control principle, the cascade gas target module 3 has the same high-order harmonic enhancement function.

[0147] The multi-stage gas target placement structure in the embodiment of the present invention is as follows Fig.11As shown, in this embodiment, the number of gas targets is 20, the specific enhancement order is 41, and the type of gas target is a gas nozzle. In this embodiment, the sizes of the first distance 87 to the twentieth distance 106 are respectively 0.96 Rayleigh distance before the focus, 0.83 Rayleigh distance before the focus, 0.7 Rayleigh distance before the focus, 0.6 Rayleigh distance before the focus, 0.5 Rayleigh distance before the focus, 0.4 Rayleigh distance before the focus, 0.32 Rayleigh distance before the focus, 0.23 Rayleigh distance before the focus, 0.15 Rayleigh distance before the focus, 0.08 Rayleigh distance before the focus, 0.08 Rayleigh distance after the focus, 0.15 Rayleigh distance after the focus, 0.23 Rayleigh distance after the focus, and 0.23 Rayleigh distance after the focus. The corresponding Gouy phases of the 41st order harmonics at gas target No. 1 66 to gas target No. 20 85 are -10π, -9π, -8π, -7π, -6π, 5π, -4π, -3π, -2π, -π, π, 2π, 3π, 4π, 5π, 6π, 7π, 8π, 9π, and 10π, respectively.

[0148] Under the parameter settings of this embodiment, enhanced gas high-order harmonics can be generated in the cascade gas target module 3, indicating that this device can achieve higher-multiple enhancement of gas high-order harmonics by further increasing the number of gas targets, further illustrating the universality of this method.

[0149] Although the effects of some embodiments are shown above, those skilled in the art should understand that according to the concept of the present invention, the aforementioned other embodiments without specific effects or other technical solutions of the present invention not shown in the embodiments can also achieve the following technical effects stated in the invention content section that are equivalent to the embodiments:

[0150] 1. The high-order harmonic coherent amplification method based on Gouy phase control and using multiple cascade gas targets of the present invention adopts a cascade gas target module solution, and controls the Gouy phase of specific-order gas high-order harmonics by adjusting the relative distance between multiple gas targets, and finally enhances gas high-order harmonics, especially specific-order harmonics. This method is not limited by the energy of a single pulse of a driving laser, and can increase the energy of the generated attosecond pulse sequence. Compared with the traditional cascade gas target module solution, the method of the present invention can accurately control the phase of specific-order gas high-order harmonics, realize the enhancement of harmonics of different orders, and provide assistance for research in fields such as ultrafast electron dynamics and attosecond nonlinear physics.

[0151] 2. The present invention has a simple structure, simple operation, compact design, and obvious effect. It is not limited by the driving laser energy and can enhance harmonics of different orders. It has the advantages of high energy, wide spectrum, wide applicability, and good repeatability. It can be applied to ultrafast light field physical property detection, transient absorption spectroscopy measurement, attosecond physics, materials science and other fields, and has good application prospects and scientific research value.

[0152] At this point, those skilled in the art should recognize that based on the contents disclosed in the present invention, the product form and style of the exemplary embodiments of the present invention described herein, without departing from the spirit and principles of the present invention, many other variations or modifications directly made to the present invention should all be deemed to be within the scope of the present invention.

[0153] Although the present invention has been described to a certain extent, it is obvious that appropriate changes in various conditions can be made without departing from the spirit and scope of the present invention. It is understood that the present invention is not limited to the embodiments described, but belongs to the scope of the claims, which includes equivalent replacements of each factor described.

Claims

1. A cascade gas target high-order harmonic enhancement device based on Gouy phase control, characterized in that: The cascade gas target high harmonic enhancement device comprises: a femtosecond drive laser for generating a drive laser; A focusing module for converging the driving laser into a focused beam; Cascade gas target module for generating and controlling the phase of high-order harmonics; and Terminals for characterization and / or application; Preferably, the cascade gas target high-order harmonic enhancement device further comprises: a vacuum chamber device and a rare gas generator; More preferably, the focusing module, the cascade gas target module and the terminal are located in the vacuum chamber device.

2. The cascade gas target high harmonic enhancement device according to claim 1, characterized in that: The central wavelength of the femtosecond driving laser is in the near-infrared band, and the wavelength range of the near-infrared band is preferably 780nm to 2526nm, more preferably 780nm to 1100nm, and further preferably 780nm to 820nm; The output pulse width of the femtosecond driven laser is 100fs to 300fs, preferably 50fs to 100fs, more preferably 30fs to 50fs; The single pulse energy of the femtosecond driven laser is 0.1mJ to 20mJ, preferably 0.1mJ to 10mJ, more preferably 0.1mJ to 5mJ; and / or The femtosecond driven laser is selected from one or more of the following: a femtosecond chirped pulse amplifier, a femtosecond laser oscillator, a femtosecond optical parametric amplifier, a femtosecond optical parametric chirped pulse amplifier, preferably a femtosecond chirped pulse amplifier or a femtosecond optical parametric chirped pulse amplifier, and most preferably a femtosecond chirped pulse amplifier.

3. The cascade gas target high harmonic enhancement device according to claim 1 or 2, characterized in that: The focusing module is selected from one or more of the following combinations: a spherical concave lens, a spherical concave reflector, an off-axis parabolic mirror, a tire mirror, an ellipsoidal concave reflector, an ellipsoidal concave lens, a cylindrical concave reflector, and a cylindrical concave lens, preferably selected from one or more of the following combinations: a spherical concave lens, a spherical concave reflector, and an off-axis parabolic mirror, and most preferably a spherical concave reflector; and / or The rare gas generator includes a steel cylinder, a pressure reducing valve and a rare gas pipeline. One end of the rare gas pipeline is connected to the steel cylinder through the pressure reducing valve, and the other end of the rare gas pipeline is connected to the vacuum chamber device, and sprays rare gas as a high-order harmonic generating medium.

4. The cascade gas target high harmonic enhancement device according to any one of claims 1 to 3, characterized in that: The cascade gas target module includes two or more cascaded gas targets and an electric translation stage; wherein: Each of the gas targets is mounted on a respective independent electric translation stage to independently achieve movement in three dimensions.

5. The cascade gas target high harmonic enhancement device according to claim 4, characterized in that: The gas target is selected from one or more of the following: a continuous gas pool, a pulsed gas pool, a gas nozzle, a semi-infinite gas target, preferably selected from one or more of the following: a continuous gas pool, a pulsed gas pool, a gas nozzle, and most preferably a pulsed gas pool; and / or The rare gas is selected from one or more of the following: helium, neon, argon, krypton, xenon, preferably selected from one or more of the following: neon, argon, krypton, and most preferably argon.

6. The cascade gas target high harmonic enhancement device according to claim 4 or 5, characterized in that: The gas target is arranged within the Rayleigh distance of the focused light beam; The waist position of the focused light beam is the focus, and the Gouy phase of the focus is preferably zero; and / or The distance between each of the gas targets and the focus is 0 to 2 Rayleigh distances before the focus and / or 0 to 2 Rayleigh distances after the focus, preferably 0.3 to 1.5 Rayleigh distances before the focus and / or 0.3 to 1.5 Rayleigh distances after the focus, more preferably 0.5 to 1 Rayleigh distance before the focus and / or 0.5 to 1 Rayleigh distance after the focus; Preferably, the laser peak power density at the position where the gas target is placed is greater than the generation threshold of the laser peak power density of the argon high harmonics, and more preferably greater than 1×10 14 W / cm 2 .

7. The cascade gas target high harmonic enhancement device according to any one of claims 1 to 6, characterized in that: The vacuum chamber device comprises: a vacuum chamber, a vacuum pipeline and a vacuum pump; wherein, The vacuum chamber and the vacuum pipeline are connected via a vacuum gate valve; The vacuum degree of the vacuum chamber is 1×10 -6 mbar~1×10 -11 mbar, preferably 1×10 -7 mbar~1×10 - 9 mbar, most preferably 1×10 -8 mbar; The vacuum chamber is selected from one or more of the following: a circular vacuum chamber, a square vacuum chamber, a horizontal vacuum chamber, and a spherical vacuum chamber, preferably selected from one or more of the following: a circular vacuum chamber, a square vacuum chamber, and a horizontal vacuum chamber, more preferably a circular vacuum chamber and / or a horizontal vacuum chamber; The vacuum pipe is selected from one or more of the following: a cylindrical pipe, a welded corrugated pipe, a formed corrugated pipe, and a small corrugated pipe, preferably selected from one or more of the following: a cylindrical pipe, a welded corrugated pipe, and a formed corrugated pipe, more preferably a cylindrical pipe and / or a formed corrugated pipe; The vacuum pump comprises a fore vacuum pump and an ultra-high vacuum pump, wherein the fore vacuum pump is preferably selected from one or more of the following: a diaphragm pump, a screw pump, a rotary vane pump, a Roots pump, more preferably a diaphragm pump or a screw pump, and most preferably a diaphragm pump; the ultra-high vacuum pump is preferably selected from one or more of the following: a turbomolecular vacuum pump, an ion vacuum pump, a titanium sublimation vacuum pump, more preferably a turbomolecular vacuum pump or an ion vacuum pump, and most preferably a turbomolecular vacuum pump; Preferably, the focusing module and the cascade gas target module are located in the same vacuum chamber or in two different vacuum chambers, more preferably in the same vacuum chamber.

8. The cascade gas target high harmonic enhancement device according to any one of claims 1 to 7, characterized in that: The terminal comprises: Characterization terminals for measuring the spectrum, average pulse duration and / or energy of high harmonics; and Application terminal; in, The representation terminal and the application terminal are switched or used in parallel; The characterization terminal is selected from one or more of the following: an extreme ultraviolet spectrometer system, a time-of-flight spectrometer system, a photoelectron detector, an extreme ultraviolet vacuum camera, and a Shack-Hartmann wavefront sensor, preferably selected from one or more of the following: an extreme ultraviolet spectrometer system, a time-of-flight spectrometer system, and a photoelectron detector, and more preferably an extreme ultraviolet spectrometer system and / or a time-of-flight spectrometer system; The application terminal is selected from one or more of the following: a transient absorption spectroscopy system, a light emission electron microscope system, an angle-resolved photoelectron spectroscopy system, a cold target recoil ion momentum spectrometer system, and a velocity imaging spectrometer system, preferably selected from one or more of the following: a transient absorption spectroscopy system, a light emission electron microscope system, an angle-resolved photoelectron spectroscopy system, and a cold target recoil ion momentum spectrometer system, more preferably a transient absorption spectroscopy system and / or an angle-resolved photoelectron spectroscopy system; Preferably, the characterization terminal and the application terminal are located in different vacuum chambers.

9. A method for enhancing high-order harmonics, characterized in that: The method comprises using the device according to any one of claims 1 to 8 to enhance high-order harmonics; Preferably, the method comprises the following steps: The femtosecond driving laser generates a driving laser, which passes through the focusing module and converges into a focused light beam. The first gas target after cascade inflation generates high-order harmonics. The high-order harmonics and the driving laser work together at the second gas target to generate extreme ultraviolet photon-assisted high-order harmonics. The extreme ultraviolet photon-assisted high-order harmonics and the first gas target produce high-order harmonics that are coherently superimposed. When the number of gas targets is preferably greater than 2, the driving laser and the coherently superimposed high-order harmonics generated by the previous gas target jointly act on the extreme ultraviolet photon-assisted gas high-order harmonics generation process at the second gas target and subsequent gas targets. The extreme ultraviolet photon-assisted high-order harmonics and the coherently superimposed high-order harmonics generated by the previous gas target are superimposed again to finally obtain enhanced high-order harmonics, which are propagated to the characterization terminal and / or the application terminal for measurement.

10. The method according to claim 9, characterized in that For high-order harmonics of different orders, the method further includes: enhancing the high-order harmonics of different orders by adjusting the distance between each of the gas targets and the focus.

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