Dispersion compensation and separation method and device for attosecond pulse of soft X-ray water window wave band

Abstract

The invention belongs to the field of attosecond pulses, and particularly relates to a dispersion compensation and separation method and device for soft X-ray water window wave band attosecond pulses. The dispersion compensation device comprises a vacuum cavity and a liquid film generation mechanism, the working end of the liquid film generation mechanism is arranged in the vacuum cavity and used for outputting a working medium to generate a liquid film with the uniform and adjustable thickness. The separation device comprises a vacuum cavity and a liquid film generation mechanism, the working end of the liquid film generation mechanism is arranged in the vacuum cavity and used for outputting a working medium to generate a liquid film which is non-uniform and adjustable in thickness. The dispersion compensation and separation device comprises a vacuum cavity and two liquid film generation mechanisms, and the working ends of the two liquid film generation mechanisms are respectively arranged in the vacuum cavity and are used for respectively outputting working media to generate liquid films with non-uniform and adjustable thicknesses. Dispersion compensation or separation of attosecond pulses can be independently achieved through the liquid film, and dispersion compensation and separation can also be achieved at the same time.

Description

Technical Field

[0001] The invention relates to a dispersion compensation and separation device for soft X-rays, and in particular to a dispersion compensation and separation method and device for soft X-ray water window band attosecond pulses. Background Art

[0002] Attoseconds (10 -18 s) pulses were born in the early 21st century and are the fastest pulses currently mastered by humans. In the past 20 years, they have promoted significant progress and breakthroughs in attosecond science research, and provided new research methods and important innovation opportunities for the development of physics, chemistry, biology, materials, information and other fields. Compared with traditional extreme ultraviolet attosecond pulses, attosecond pulses in the soft X-ray band have higher photon energy, so they can achieve higher spatial resolution, can be used for inner shell electron dynamics research, can support shorter pulse widths, and attosecond pulses in the soft X-ray water window band are also more suitable for the study of biological samples.

[0003] Currently, soft X-ray attosecond light sources face two problems:

[0004] 1. Dispersion compensation of attosecond pulses.

[0005] In the attosecond pulse generation method based on high-order harmonic technology, according to the high-order harmonic three-step model, for the commonly used short orbit, the kinetic energy of the electron increases with the increase of the recombination time, and the attosecond pulse has a positive chirp, and negative dispersion needs to be provided to compress the width of the attosecond pulse. At present, the method of compensating for the dispersion of attosecond pulses mainly uses metal films. In the soft X-ray band, the group delay dispersion (GDD) of commonly used metal films is as follows: Figure 1 As shown in the figure, the transmittance of commonly used metal films is Figure 2 As shown in the figure, the horizontal axis is photon energy. The main problems of metal film compensation dispersion are: (1) Considering the reasonable transmittance of attosecond pulses, the thickness of the metal film is generally controlled at 100-200nm. However, under this thickness condition, the negative dispersion provided by the metal film is limited, and the dispersion compensation effect is not ideal; (2) The thickness of the metal film is fixed, and the inability to adjust the thickness means that the dispersion amount cannot be accurately adjusted; (3) The damage threshold of the metal film is low; (4) The fixed mesh structure of the metal film will affect the spatial profile of the attosecond pulse; (5) The oxidation of the metal film will lead to a decrease in the transmittance of the attosecond pulse.

[0006] 2. Separation of attosecond pulses and driving laser.

[0007] At present, the femtosecond laser driven gas high-order harmonic process is the most commonly used method to obtain attosecond pulses. In this method, after the driving laser and the gas target interact to produce attosecond pulses, some driving lasers still remain and are transmitted colinearly with the generated attosecond pulses. Since these residual driving lasers will have an adverse effect on the application of attosecond pulses, it is necessary to separate this part of the residual driving lasers from the attosecond pulses. However, the separation of attosecond pulses in the soft X-ray band is relatively difficult, and traditional solutions have many limitations.

[0008] At present, there are three commonly used solutions: (1) Use metal film for separation. The driving laser (mid-infrared band) generally has low photon energy and is difficult to penetrate the metal film, while attosecond pulses are generally in the extreme ultraviolet or soft X-ray band and have relatively high transmittance, such as Figure 2 As shown. Considering the transmittance of attosecond pulses, the thickness of the metal film is generally controlled at 100-200nm. The main problems with metal films for attosecond pulse separation are: 1) Low damage threshold. In high-performance attosecond light sources, the residual driving laser still has high power or energy, and the metal film is very easy to damage; 2) The mesh structure of the fixed metal film will affect the spatial profile of the attosecond pulse; 3) The oxidation of the metal film will lead to a decrease in the transmittance of the attosecond pulse. (2) Use a beam splitter to separate attosecond pulses. When the light pulse is incident at the Brewster angle corresponding to the wavelength of the driving laser, the reflectivity of the driving light is low. Since the Brewster angles corresponding to different wavelengths of light are different, extreme ultraviolet light is not incident at the Brewster angle, so it has a higher reflectivity. However, this method is mainly used in the extreme ultraviolet band. There is no suitable material in the soft X-ray band and the reflectivity is very low. (3) Use annular driving light. Using the spatial distribution of the driving light, since most of the energy of the driving pulse is distributed in the central area, this method will result in a large amount of driving light energy loss. Summary of the invention

[0009] The purpose of the present invention is to provide a method and device for dispersion compensation and separation of attosecond pulses in the soft X-ray water window band, in which traditional solutions such as metal films and beam splitters in soft X-ray attosecond light sources cannot effectively solve the problem of dispersion compensation and separation of attosecond pulses in the soft X-ray water window band, through comprehensive calculation and analysis of the dispersion, transmittance, refractive index of water in the soft X-ray water window band and the characteristics of attosecond pulses in the soft X-ray water window band.

[0010] To achieve the above purpose, the technical solution adopted by the present invention is:

[0011] A dispersion compensation method for attosecond pulses in the soft X-ray water window band, which is special in that:

[0012] A liquid film with uniform and adjustable thickness is used to compensate the dispersion of attosecond pulses in the soft X-ray water window band.

[0013] A dispersion compensation device for soft X-ray water window band attosecond pulses is used to implement the above-mentioned dispersion compensation method for soft X-ray water window band attosecond pulses, and its special features are:

[0014] It includes a vacuum chamber and a liquid film generating mechanism;

[0015] The working end of the liquid film generating mechanism is placed inside the vacuum chamber and is used to output the working medium to generate a liquid film with uniform and adjustable thickness;

[0016] An inlet and an outlet are respectively arranged on two opposite side walls of the vacuum chamber, and the inlet and the outlet are respectively located on two sides of the liquid film;

[0017] The soft X-ray water window band attosecond pulse to be dispersion compensated is incident on the liquid film through the incident port, and after dispersion compensation by the liquid film, it is guided out of the vacuum cavity through the exit port.

[0018] The present invention also provides a method for separating attosecond pulses in the soft X-ray water window band, which is special in that:

[0019] A liquid film with non-uniform and adjustable thickness is used to separate attosecond pulses in the soft X-ray water window band.

[0020] The present invention also provides a soft X-ray water window band attosecond pulse separation device, which is used to implement the above-mentioned X-ray water window band attosecond pulse separation method, and its special features are:

[0021] It includes a vacuum chamber and a liquid film generating mechanism;

[0022] The working end of the liquid film generating mechanism is placed inside the vacuum chamber and is used to output a working medium to generate a liquid film with non-uniform and adjustable thickness;

[0023] An inlet and an outlet are respectively arranged on two opposite side walls of the vacuum chamber, and the inlet and the outlet are respectively located on two sides of the liquid film;

[0024] The collinearly transmitted soft X-ray water window band attosecond pulses and residual infrared driving laser to be separated are incident on the liquid film through the incident port. After the residual infrared driving laser is separated by the liquid film, the soft X-ray water window band attosecond pulses are output to the outside of the vacuum cavity through the exit port.

[0025] Furthermore, the cross section of the liquid film along the thickness direction is an isosceles trapezoid, and the angle between its two inclined sides is 1 mrad to 10 mrad.

[0026] Furthermore, it also includes a baffle or a reflector disposed in the vacuum chamber; the baffle or the reflector is disposed on the optical path of the residual infrared driving laser separated by the liquid film; the baffle is used to shield the residual infrared driving laser;

[0027] Alternatively, a guide outlet is provided on a side wall of the vacuum cavity located on the reflecting light path of the reflector, and the reflector is used to guide the residual infrared driving laser out of the vacuum cavity through the guide outlet after reflection.

[0028] The present invention also provides a method for dispersion compensation and separation of attosecond pulses in the soft X-ray water window band, which is special in that:

[0029] Two liquid films with non-uniform and adjustable thickness are used to separate and compensate the dispersion of attosecond pulses in the soft X-ray water window band.

[0030] The present invention also provides a dispersion compensation and separation device for soft X-ray water window band attosecond pulses, which is used to implement the above-mentioned dispersion compensation and separation method for soft X-ray water window band attosecond pulses, and its special features are:

[0031] It includes a vacuum chamber and two liquid film generating mechanisms;

[0032] The working ends of the two liquid film generating mechanisms are respectively placed inside the vacuum cavity, and are used to respectively output working media to generate liquid films with non-uniform and adjustable thicknesses;

[0033] A gap is arranged between the two liquid films along the length direction of the vacuum cavity. The two liquid films have the same specifications. The sides close to each other are arranged in parallel, and the sides far away from each other are arranged in parallel accordingly, and the midlines of the two in the height direction coincide with each other.

[0034] An inlet and an outlet are respectively arranged on two opposite side walls of the vacuum chamber, and the inlet and the outlet are respectively located on the side away from each other of the two liquid films;

[0035] The liquid film near the incident port is defined as the first liquid film, and the liquid film near the incident port is defined as the second liquid film;

[0036] The collinearly transmitted soft X-ray water window band attosecond pulses and residual infrared driving laser to be dispersion compensated and separated are incident on the first liquid film through the incident port, and the residual infrared driving laser and dispersion compensation are separated by the first liquid film. After the second liquid film performs dispersion compensation on the soft X-ray water window band attosecond pulses, they are guided out of the vacuum cavity through the exit port.

[0037] Further, the cross section of the first liquid film along the thickness direction is a right isosceles trapezoid, the cross section of the second liquid film along the thickness direction is an inverted isosceles trapezoid, the angle between the two inclined sides of the first liquid film is 1mrad to 10mrad, and the angle between the two inclined sides of the second liquid film is -10mrad to -1mrad;

[0038] Alternatively, the cross section of the first liquid film along the thickness direction is an inverted isosceles trapezoid, the cross section of the second liquid film along the thickness direction is a right isosceles trapezoid, the angle between the two inclined sides of the first liquid film is -10mrad to -1mrad, and the angle between the two inclined sides of the second liquid film is 1mrad to 10mrad.

[0039] Furthermore, it also includes a baffle or a reflector disposed in the vacuum chamber; the baffle or the reflector is located on the optical path of the residual infrared driving laser that is spatially separated by the liquid film; the baffle is used to shield the residual infrared driving laser;

[0040] Alternatively, a guide outlet is provided on a side wall of the vacuum cavity located on the reflecting light path of the reflector, and the reflector is used to guide the residual infrared driving laser out of the vacuum cavity through the guide outlet after reflection.

[0041] The beneficial effects of the present invention are:

[0042] 1. The present invention uses a liquid film with uniform thickness for dispersion compensation, which can be tens of times thicker than a metal film to provide greater negative dispersion. The thickness of the liquid film can also be adjusted according to actual needs, making the dispersion compensation more accurate. At the same time, it will not affect the spatial profile of the attosecond pulse, and avoid the problem of reduced attosecond pulse transmittance due to oxidation of the metal film. It is of great significance for achieving shorter pulse width attosecond pulses and thus obtaining higher time resolution. Compared with the traditional metal film method, the method proposed by the present invention can provide a larger negative dispersion amount under the same transmittance conditions, and the dispersion is flexible and tunable, and has a higher damage threshold.

[0043] 2. The present invention realizes the spatial separation of collinearly transmitted soft X-ray water window band attosecond pulses and infrared driving lasers through a liquid film with non-uniform thickness. At the same time, since the transmittance of the infrared driving laser in the liquid film is relatively low, the liquid film itself can also absorb a certain amount of infrared driving laser, which is helpful for separation. Moreover, since the liquid film is flowing, it can still work under the condition of high-power / high-energy driving laser without any damage problem.

[0044] 3. The present invention can simultaneously achieve the separation and dispersion compensation of attosecond pulses in the soft X-ray water window band by using two liquid films with non-uniform thickness.

[0045] 4. The present invention can guide the separated infrared driving laser out of the vacuum cavity by means of the provided reflector, thereby realizing the secondary utilization of the infrared driving laser.

[0046] 5. The present invention has low loss for the transmission of attosecond pulses in the soft X-ray water window band. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is the dispersion diagram of the commonly used metal film (100nm thickness) in the existing soft X-ray band;

[0048] Figure 2 This is the transmittance diagram of the commonly used metal film (100nm thickness) in the existing soft X-ray band;

[0049] Figure 3 It is the dispersion diagram of water and different metal films in the soft X-ray band range of 200-530eV;

[0050] Figure 4 is a graph showing the transmittance of attosecond pulses in the soft X-ray water window band in liquid water films of different thicknesses in an embodiment of the present invention;

[0051] Figure 5 It is a structural schematic diagram of an embodiment of a dispersion compensation device for attosecond pulses in the soft X-ray water window band of the present invention;

[0052] Figure 6 Schematic diagram of separation principle of an embodiment of a separation device for attosecond pulses in the soft X-ray water window band of the present invention, a is a schematic diagram of the separation optical path, and b is a schematic diagram of the principle;

[0053] Figure 7 1 is a schematic diagram of the structure of an embodiment of a separation device for attosecond pulses in the water window band of soft X-rays according to the present invention, wherein a is a schematic diagram of the structure when a baffle is provided, and b is a schematic diagram of the structure when a reflector is provided;

[0054] Figure 8 It is a structural schematic diagram of a dispersion compensation and separation device for attosecond pulses in the soft X-ray water window band of the present invention, a is a structural schematic diagram when a baffle is set, and b is a structural schematic diagram when a reflector is set.

[0055] In the figure: 1-vacuum chamber, 2-liquid film generating mechanism, 3-liquid film, 4-baffle, 5-reflecting mirror. DETAILED DESCRIPTION

[0056] In order to make the purpose, advantages and features of the present invention clearer, the dispersion compensation and separation method and device of soft X-ray water window band attosecond pulses proposed by the present invention are further described in detail below in combination with the accompanying drawings and specific embodiments. According to the following specific implementation methods, the advantages and features of the present invention will be clearer. It should be noted that: the drawings are all in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention; secondly, the structure shown in the drawings is often part of the actual structure.

[0057] Embodiment 1

[0058] Dispersion compensation methods and scheme design

[0059] There is no public data on the group delay dispersion of water (H2O) in the soft X-ray band. Based on the refractive index parameters of water in the soft X-ray band of 200-530 eV, the dispersion of water in this range is calculated. Figure 3 The green curve is the GDD of H2O with a thickness of 100 nm (as 2 ). In the range of 200-530 eV, water has negative dispersion characteristics, which can compensate for the intrinsic positive dispersion of attosecond pulses. At 250 eV, GDD is about -6.32 as 2 ; GDD at 300eV is about -3.67as 2 ; GDD at 350eV is about -2.44as 2 ; GDD at 400eV is about -1.81as 2 ; GDD at 450eV is about -1.60as 2 ; GDD at 500eV is about -2.07as 2 .according to Figure 3 The calculated dispersion curves of commonly used metal materials in the soft X-ray band show that in this band, the negative dispersion provided by the water film of the same thickness is lower than but close to the negative dispersion provided by the metal film, and has a wider negative dispersion range than Ag, Ti, and Sn.

[0060] The transmittance of liquid water of different thicknesses in the water window band 282-533 eV is as follows Figure 4 As shown in the figure, at a thickness of 100nm, water has a transmittance of more than 95%, which is much higher than the transmittance of metal films. At a thickness of 5μm, it still has an overall transmittance of about 30%.

[0061] According to the calculation and analysis of the dispersion coefficient and transmittance of attosecond pulses in the soft X-ray water window band in water, water has a higher transmittance and can be tens of times thicker than metal films, thus providing greater negative dispersion. Taking transmittance and dispersion into consideration, the thickness of the liquid water film can be reasonably set between hundreds of nanometers and several microns to provide an appropriate amount of negative dispersion. For example, when the thickness is 5μm, the GDD at 250eV is about -316as 2 , GDD at 300eV is about -183.5as 2 , GDD at 350eV is about -122as 2 , GDD at 400eV is about -90.5as 2 , GDD is about -80as at 450eV 2 , GDD at 500eV is about -103.5as 2 , which can compensate for the positive dispersion of attosecond pulses in the soft X-ray water window band and achieve shorter attosecond pulse width.

[0062] It is also important to note that, unlike metal films, which have a fixed thickness (generally 100nm, 150nm, 200nm, 250nm), the thickness of liquid water films can be adjusted in real time, and has a high thickness adjustment accuracy, so that real-time dispersion compensation management can be performed according to the conditions of attosecond pulses, and the dispersion compensation amount is more accurate. Therefore, the use of liquid water films can effectively compensate for the dispersion of attosecond pulses in the soft X-ray water window band, which plays an important role in the realization of shorter pulse width attosecond pulses.

[0063] The design of the scheme for attosecond pulse dispersion compensation in the soft X-ray water window band using liquid water film is as follows: Figure 5 As shown. The dispersion compensation device mainly includes a vacuum cavity 1 and a liquid film generating mechanism 2; the liquid film generating mechanism 2 uses a liquid working medium, which is specifically water in this embodiment, and its working end is placed inside the vacuum cavity 1, and is used to output the working medium to generate a liquid film 3 of uniform thickness. The liquid film in this embodiment is a liquid water film; an inlet and an outlet (not shown in the figure) are respectively provided on two opposite side walls of the vacuum cavity 1, and the inlet and the outlet are respectively located on both sides of the liquid water film, and the soft X-ray water window band attosecond pulse to be dispersion compensated is incident on the liquid water film through the inlet, and the liquid water film is used to perform dispersion compensation on the soft X-ray water window band attosecond pulse passing through it, and the soft X-ray water window band attosecond pulse after dispersion compensation is exported to the outside of the vacuum cavity 1 through the outlet.

[0064] Taking into account transmittance and dispersion compensation, the thickness of the liquid water film is reasonably set between hundreds of nanometers and several microns. There are mature solutions for the liquid water film generation mechanism that meets this thickness range. The solution of two liquid nozzles spraying against each other to form a liquid water film can be adopted [Christopher J.Crissman, et al.Sub-micron thick liquid sheets produced by isotropically etched glass nozzles.Lab on a Chip, 2022, 22.7:1365-1373], or a special design single nozzle solution made by 3D printing or etching can be adopted [Maria Ekimova, et al.A liquid flatjet system for solution phase soft-x-ray spectroscopy.Structural Dynamics, 2015, 2.5]. The thickness of the liquid water film can be adjusted according to the angle of the two nozzles or the liquid flow rate to achieve a thickness of hundreds of nanometers to several microns. The surface size of the liquid water film can also be adjusted by adjusting the flow rate to adapt to the spot size. Under this adapted flow rate, liquid recycling in a vacuum is also a mature solution.

[0065] When used only for dispersion compensation, the attosecond pulses should be transmitted from a region with relatively uniform thickness of the liquid water film.

[0066] In addition to water, alcohol liquids such as methanol, ethanol, propanol, etc. can also be used.

[0067] Embodiment 2

[0068] Separation methods and scheme design

[0069] The separation scheme is designed by analyzing the refractive index of liquid water in different bands and the spatial size of the liquid water film.

[0070] The attosecond pulses in the soft X-ray water window band are usually generated by a driving laser in the mid-infrared band. The refractive index of water in the mid-infrared band is around 1.3, while the refractive index of water in the soft X-ray water window band is around 1. This embodiment is different from the first embodiment in that a liquid water film of non-uniform thickness is used, and the rest of the structure is the same as that of the embodiment.

[0071] Liquid water films with non-uniform thickness specifically include:

[0072] (1) The thickness decreases from top to bottom (a positive isosceles trapezoid). The attosecond pulse in the soft X-ray water window band has almost no effect on the beam direction after passing through the liquid water film, while the mid-infrared driving laser will point upward due to refraction in the liquid water, such as Figure 6 As shown, after a certain transmission distance, it is spatially separated from the attosecond pulse.

[0073] (2) The thickness increases from top to bottom (inverted isosceles trapezoid). The attosecond pulse in the soft X-ray water window band has almost no effect on the beam direction after passing through the liquid water film, while the mid-infrared driving laser will point downward due to refraction in the liquid water.

[0074] The non-uniform thickness of the liquid water film is approximately an isosceles trapezoid, and the angle between the two sides determines the deflection angle of the infrared light. In the infrared band, taking the refractive index of 1.3 as an example, when the angle between the two sides of the liquid water film is 1mrad, the deflection angle is 0.3mrad; when the angle between the two sides of the liquid water film is 5mrad, the deflection angle is 1.5mrad; when the angle between the two sides of the liquid water film is 10mrad, the deflection angle is 3mrad. At this time, after a transmission distance of 1m, the center of the infrared driving laser and the center of the attosecond pulse deviate by 3mm.

[0075] Considering the divergence angle of the infrared-driven laser, let's consider an actual example of a soft X-ray attosecond light source. The divergence angle of the infrared-driven laser is 5mrad, and the divergence angle of the soft X-ray attosecond pulse is 0.5mrad. In order to completely offset the two beams of light in space, the deflection angle needs to reach 2.75mrad, and the angle between the two sides of the liquid water film needs to be about 9.167mrad. When the distance between the attosecond generation position and the liquid water film is 0.5m, the diameter of the infrared-driven laser spot is about 2.5mm, and the diameter of the attosecond pulse spot is about 0.25mm. When the deflection angle is 2.75mrad, after passing through the liquid water film, it needs to propagate 0.5m to completely separate the two beams of light in space. In this case, the angle between the two sides of the liquid water film needs to be about 9.167mrad. For an attosecond pulse with a diameter of 0.25mm, the thickness of the liquid water film that the attosecond pulse passes through changes by 2.29μm (from the top to the bottom of the spot).

[0076] The design of the scheme for separating attosecond pulses in the soft X-ray water window band using liquid water film is as follows: Figure 7 As shown. The liquid water film needs to be placed in the vacuum chamber 1, and can be recycled to ensure the use efficiency. The residual infrared driving laser and attosecond pulse transmission of the co-linear transmission are separated in space through the liquid water film.

[0077] The residual infrared driving laser light which has been spatially separated by the liquid water film can be blocked by the baffle 4 ( Figure 7 (a)) or using a reflector 5 ( Figure 7 In (b), the residual laser is reflected and provided at a guide port (not shown in the figure) on the vacuum chamber 1, and then guided out and reused.

[0078] Since the transmittance of mid-infrared laser in water is low, the liquid water film itself can also absorb a certain amount of mid-infrared laser, which is helpful for separation. At the same time, since the liquid water film is flowing, it can still work well under high-power / high-energy laser driving conditions without damage.

[0079] Embodiment 3

[0080] Method and scheme design for simultaneous dispersion compensation and separation

[0081] In the first embodiment, the liquid water film has a uniform thickness and cannot spatially separate the infrared driving laser and the attosecond pulse, which is suitable for the case where only attosecond pulse dispersion compensation is considered.

[0082] In the second embodiment, the liquid water film has a non-uniform thickness. Since the attosecond pulse spot passes through liquid water films of different thicknesses at different positions, it means that there are different dispersion compensation amounts, which is unfavorable under normal circumstances and is only suitable for the case where only the separation of attosecond pulses is considered.

[0083] If attosecond pulse separation and dispersion compensation are performed simultaneously, the scheme is as follows Figure 8 As shown. Combining the schemes of Example 1 and Example 2, this embodiment adopts two liquid water films, the cross section of the first liquid water film along the thickness direction is a positive isosceles trapezoid, that is, the thickness decreases from top to bottom, the cross section of the second liquid water film along the thickness direction is an inverted isosceles trapezoid, that is, the thickness increases from top to bottom, the angle between the two inclined sides of the first liquid water film is 1mrad to 10mrad, and the angle between the two inclined sides of the second liquid water film is -10mrad to -1mrad; or, the cross section of the first liquid water film along the thickness direction is an inverted isosceles trapezoid, that is, the thickness increases from top to bottom, the cross section of the second liquid water film along the thickness direction is a positive isosceles trapezoid, that is, the thickness decreases from top to bottom, the angle between the two inclined sides of the first liquid water film is -10mrad to -1mrad, and the angle between the two inclined sides of the second liquid water film is 1mrad to 10mrad.

[0084] The first liquid water film achieves separation of attosecond pulses and infrared driving lasers, as well as certain dispersion compensation. The second liquid water film is placed at a certain distance, which separates the infrared driving laser spot from the attosecond pulse spot in space, and the second liquid water film achieves dispersion compensation for the attosecond pulse. After the attosecond pulse passes through the two liquid water films, different positions on the spot pass through liquid water films of equal thickness.

[0085] Consider an actual example of an attosecond light source in the soft X-ray water window band. The divergence angle of the infrared driving laser is 5mrad, the divergence angle of the attosecond pulse in the soft X-ray water window band is 0.5mrad, and the angle between the two sides of the liquid water film is about 9.167mrad. When the refractive index of the infrared driving laser in water is 1.3, the deflection angle reaches 2.75mrad, which meets the minimum deflection angle for completely separating the two beams of light. When the distance between the attosecond generation position and the liquid water film is 0.5m, the diameter of the infrared driving laser spot is about 2.5mm, and the diameter of the attosecond pulse spot is about 0.25mm. The thickness change of the attosecond pulse passing through the first liquid water film is 2.29μm (from the top to the bottom of the spot), and the two beams of light can be completely separated in space after propagating 0.5m. After this propagation distance, the thickness change of the second liquid water film placed is opposite to that of the first liquid water film. The thickness change of the attosecond pulse passing through the second liquid water film is still 2.29μm (from the top to the bottom of the spot), but the thickness of the upper and lower ends is opposite. After passing through the second liquid water film, different positions on the attosecond pulse spot pass through liquid water films of equal thickness. For attosecond pulses, the equivalent thickness of the two liquid water films is about 2.29μm. At this time, the overall transmittance is about greater than 50%, and the dispersion provided is: GDD is about -144.73as at 250eV 2 ; GDD at 300eV is about -84.04as 2 ; GDD at 350eV is about -55.876as 2 ; GDD at 400eV is about -41.45as 2 ; GDD at 450eV is about -36.64as 2 ; GDD at 500eV is about -47.4as 2 .

[0086] This method can provide flexible and precisely adjustable dispersion, has high efficiency, and can withstand high power / high energy. It is very suitable for attosecond light sources in the soft X-ray water window band and is of great significance for achieving attosecond pulses with shorter pulse widths and thus obtaining higher temporal resolution.

[0087] This embodiment is the same as the second embodiment, and a baffle 4 or a reflector 5 may be further provided in the vacuum chamber 1; the difference is that the baffle 4 or the reflector 5 of this embodiment needs to be provided on the optical path of the residual infrared driving laser that passes through the first liquid film to achieve separation.

Claims

1. A dispersion compensation method for attosecond pulses in the soft X-ray water window band, characterized in that: A liquid film with uniform and adjustable thickness is used to compensate the dispersion of attosecond pulses in the soft X-ray water window band.

2. A dispersion compensation device for soft X-ray water window band attosecond pulses, used to implement the dispersion compensation method for soft X-ray water window band attosecond pulses according to claim 1, characterized in that: It comprises a vacuum chamber (1) and a liquid film generating mechanism (2); The working end of the liquid film generating mechanism (2) is placed inside the vacuum chamber (1) and is used to output a working medium to generate a liquid film (3) with uniform and adjustable thickness; the working medium is water or an alcohol liquid; An inlet and an outlet are respectively arranged on two opposite side walls of the vacuum chamber (1), and the inlet and the outlet are respectively located on two sides of the liquid film (3); The soft X-ray water window band attosecond pulse to be dispersion compensated is incident on the liquid film (3) through the incident port, and after dispersion compensation is performed by the liquid film (3), it is guided out of the vacuum cavity (1) through the exit port.

3. A method for separating attosecond pulses in the soft X-ray water window band, characterized in that: A liquid film with non-uniform and adjustable thickness is used to separate attosecond pulses in the soft X-ray water window band.

4. A device for separating attosecond pulses in the soft X-ray water window band, used to implement the method for separating attosecond pulses in the soft X-ray water window band according to claim 3, characterized in that: It comprises a vacuum chamber (1) and a liquid film generating mechanism (2); The working end of the liquid film generating mechanism (2) is placed inside the vacuum chamber (1) and is used to output a working medium to generate a liquid film (3) with a non-uniform and adjustable thickness; the working medium is water or an alcohol liquid; An inlet and an outlet are respectively arranged on two opposite side walls of the vacuum chamber (1), and the inlet and the outlet are respectively located on two sides of the liquid film (3); The co-linearly transmitted soft X-ray water window band attosecond pulses and residual infrared driving laser light to be separated are incident on the liquid film (3) through the incident port. After the residual infrared driving laser light is separated by the liquid film (3), the soft X-ray water window band attosecond pulses are guided out of the vacuum cavity (1) through the exit port.

5. The soft X-ray water window band attosecond pulse separation device according to claim 4, characterized in that: The cross section of the liquid film (3) along the thickness direction is an isosceles trapezoid, and the included angle between its two inclined sides is 1 mrad to 10 mrad.

6. The soft X-ray water window band attosecond pulse separation device according to claim 4 or 5, characterized in that: It also includes a baffle (4) or a reflector (5) arranged in the vacuum chamber (1); The baffle (4) or the reflector (5) is arranged on the optical path of the residual infrared driving laser light that passes through the liquid film (3) to achieve separation; The baffle (4) is used to shield the residual infrared driving laser; Alternatively, a guide outlet is provided on a side wall of the vacuum cavity (1) located on the reflection light path of the reflector (5), and the reflector (5) is used to guide the residual infrared driving laser light out of the vacuum cavity (1) through the guide outlet after reflection.

7. A method for dispersion compensation and separation of attosecond pulses in the soft X-ray water window band, characterized in that: Two liquid films with non-uniform and adjustable thickness are used to separate and compensate the dispersion of attosecond pulses in the soft X-ray water window band.

8. A dispersion compensation and separation device for soft X-ray water window band attosecond pulses, used to implement the dispersion compensation and separation method for soft X-ray water window band attosecond pulses according to claim 7, characterized in that: It comprises a vacuum chamber (1) and two liquid film generating mechanisms (2); The working ends of the two liquid film generating mechanisms (2) are respectively placed inside the vacuum chamber (1) and are used to respectively output working media to generate liquid films (3) with non-uniform and adjustable thickness; the working media is water or alcohol liquid; A gap is provided between the two liquid films (3) along the length direction of the vacuum chamber (1); the two liquid films (3) have the same specifications, are arranged in parallel on the sides close to each other, are arranged in parallel on the sides away from each other, and their midlines in the height direction coincide with each other; An inlet and an outlet are respectively arranged on two opposite side walls of the vacuum chamber (1), and the inlet and the outlet are respectively located on the sides of the two liquid films (3) that are away from each other; The liquid film (3) close to the incident port is defined as a first liquid film, and the liquid film (3) close to the incident port is defined as a second liquid film; The soft X-ray water window band attosecond pulses and residual infrared driving laser beams to be dispersed and separated are incident on the first liquid film through the incident port, and the residual infrared driving laser beams and dispersion compensation are separated by the first liquid film. After the second liquid film performs dispersion compensation on the soft X-ray water window band attosecond pulses, the pulses are guided out of the vacuum cavity (1) through the exit port.

9. The dispersion compensation and separation device for soft X-ray water window band attosecond pulses according to claim 8, characterized in that: The cross section of the first liquid film along the thickness direction is a right isosceles trapezoid, the cross section of the second liquid film along the thickness direction is an inverted isosceles trapezoid, the angle between the two inclined sides of the first liquid film is 1mrad to 10mrad, and the angle between the two inclined sides of the second liquid film is -10mrad to -1mrad; Alternatively, the cross-section of the first liquid film along the thickness direction is an inverted isosceles trapezoid, the cross-section of the second liquid film along the thickness direction is a right isosceles trapezoid, the angle between the two inclined sides of the first liquid film is -10mrad to -1mrad, and the angle between the two inclined sides of the second liquid film is 1mrad to 10mrad.

10. The dispersion compensation and separation device for soft X-ray water window band attosecond pulses according to claim 8 or 9, characterized in that: It also includes a baffle (4) or a reflector (5) arranged in the vacuum chamber (1); The baffle (4) or the reflector (5) is located on the optical path of the residual infrared driving laser light that passes through the first liquid film to achieve separation; The baffle (4) is used to shield the residual infrared driving laser; Alternatively, a guide outlet is provided on a side wall of the vacuum cavity (1) located on the reflection light path of the reflector (5), and the reflector (5) is used to guide the residual infrared driving laser light out of the vacuum cavity (1) through the guide outlet after reflection.

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