Method for generating selectable frequency EUV light source using periodic channel structure flat plate waveguide

Abstract

The method for generating selectable frequency EUV light source by using periodic square groove structure flat plate waveguide belongs to the field of laser physics, and utilizes femtosecond laser and gas medium interaction to generate extreme ultraviolet (EUV) and soft X-ray light radiation. The present application comprises a flat plate waveguide with periodic square groove structure, a support or device required for adjusting the flat plate waveguide with periodic square groove structure, a platform or guide rail system for accurately controlling position movement, a base or support structure for stabilizing and fixing the equipment or components, a gas supply system for filling the flat plate waveguide with periodic square groove structure with gas and using inert gas to propel the experiment. By using the flat plate waveguide with periodic square groove structure as a gas carrier, the conversion efficiency of extreme ultraviolet and soft X-ray light radiation can be effectively improved; by adjusting the period of the square groove structure, the harmonic order with the highest conversion efficiency can be changed, thereby regulating the wavelength distribution of high harmonic emission, and realizing the frequency selection output of the extreme ultraviolet light source.

Description

Technical Field

[0001] This invention relates to a novel scheme for generating extreme ultraviolet (EUV) soft X-ray radiation by the interaction of a femtosecond laser with a gaseous medium, and for controlling its emission and wavelength distribution, which belongs to the field of laser physics. Background Technology

[0002] With the continuous advancement of laser technology, obtaining stable light sources with shorter wavelengths and stronger radiation has become a constant pursuit for scientists. Currently, EUV radiation has become a research focus due to its significant applications in physics, biochemistry, materials science, and chip manufacturing. The mainstream methods for generating EUV (10-120nm) light radiation include synchrotron radiation sources, discharge plasma (DPP), laser plasma (LPP), and high-order (second and above) harmonic radiation (HHG). Synchrotron radiation sources are difficult to widely apply due to the complexity of their equipment. EUV sources generated by DPP and LPP are currently mainly used in extreme ultraviolet lithography, and their emission wavelength is highly dependent on the properties of the target material itself. However, high-order harmonics driven by ultrashort pulses are a highly effective way to generate EUV and soft X-rays with ultrashort pulse width and high spatial and temporal coherence due to their unique properties such as narrow radiation bandwidth and tunable wavelength. The EUV sources generated by this method have a wide spectral range (covering infrared to ultraviolet) and the wavelength can be as short as the "water window" band (2.3-4.4 nm). EUV sources obtained through HHG radiation have the characteristics of high cost performance, easy acquisition and good coherence, which has led to great development in benchtop equipment processing. In addition, this method is currently the primary method for obtaining attosecond coherent pulses, and therefore has attracted great attention.

[0003] However, the low conversion efficiency of coherent EUV and soft X-ray sources obtained from high-harmonic radiation severely limits their further application. Furthermore, traditional methods struggle to generate tunable EUV radiation. Therefore, the focus is on obtaining tunable high-power EUV sources applicable to practical engineering projects. The generation of HHG in free space suffers from severe phase mismatch, thus prompting the development of quasi-phase matching mechanisms. The core idea is to compensate for the phase of higher harmonics in multiple in-phase regions, enabling coherent enhancement of these signals. Based on this, researchers have proposed many quasi-phase matching methods: periodically and alternately arranged gas cells, reverse-transmission light pulses, multicolor fields, microelectrode modulation, and hollow capillary schemes with periodically varying inner diameters. However, since obtaining extreme ultraviolet light typically requires the entire device to be in a high vacuum state, periodically and alternately arranged gas cells lead to drastic changes in the vacuum level of the vacuum chamber, affecting the emission of extreme ultraviolet radiation. Reverse-transmission light pulses, multicolor fields, and microelectrode modulation schemes introduce additional equipment, making the entire device more complex. Furthermore, the hollow capillary scheme with periodically varying inner diameters presents fabrication difficulties. Summary of the Invention

[0004] To address the aforementioned problems in EUV and extreme ultraviolet radiation modulation, this invention proposes a new method for improving high-order harmonic conversion efficiency and achieving frequency-selective EUV radiation output.

[0005] To achieve the above objectives, this invention proposes an experimental scheme for controlling EUV radiation using a planar waveguide with a periodic square groove structure. The scheme mainly includes a planar waveguide with a periodic square groove structure, a support or device for adjusting the planar waveguide, a platform or guide rail system for precisely controlling its position movement, a base or support structure for stabilizing and fixing the equipment or components, and a gas supply system for filling the planar waveguide with the periodic square groove structure with gas and using inert gas to propel the experiment.

[0006] A method for generating a frequency-selectable EUV light source using a planar waveguide with a periodic square groove structure is characterized by: using a planar waveguide with a periodic square groove structure as a gas carrier device for the gas filling gas; the device includes a glass block (1-1) stacked at the bottom and a glass block (1-10) stacked at the top, thin glass sheets one (1-4), two (1-5), three (1-6), and four (1-7), and the specific fabrication steps are as follows:

[0007] Step 1: Fabricate a glass block with a periodic square groove structure and a groove structure as a gas inlet: Fabricate a periodic square groove structure one (1-2) on the upper surface of the glass block (1-1) stacked below and a periodic square groove structure two (1-3) on the lower surface of the glass block (1-10) stacked above. Fabricate a groove structure one (1-8) and a groove structure two (1-9) forming a gas inlet on the edge of the glass block (1-1) stacked below. Fabricate a groove structure three (1-13) and a groove structure four (1-14) forming a gas inlet on the edge of the glass block (1-10) stacked above.

[0008] Step 2: Fabrication of thin glass sheets: Based on the dimensions of the glass blocks stacked below (1-1) and above (1-10) processed in Step 1, and the structure fabricated on the surface of the glass blocks, fabricate thin glass sheets one (1-4), two (1-5), three (1-6), and four (1-7). Align the fabricated thin glass sheets with the edges of the four right angles of the glass block stacked below (1-1), forming a cross on the upper surface of the glass block stacked below (1-1) in the area not occupied by the thin glass sheets. By adjusting the spacing between thin glass sheets two (1-5) and four (1-7), and between thin glass sheets one (1-4) and three (1-6), the internal dimensions of the waveguide can be adjusted; by adjusting the spacing between thin glass sheets four (1-7) and one (1-4), and between thin glass sheets two (1-5) and three (1-6), the size of the gas inlet can be adjusted.

[0009] Step 3: Assemble the planar waveguide with the periodic square groove structure; align the upper surface of the glass block (1-1) stacked below and the lower surface of the glass block (1-10) stacked above according to the periodic square groove structure one (1-2), periodic square groove structure two (1-3), and groove structure one (1-8), groove structure two (1-9), groove structure three (1-13), and groove structure four (1-14) used to form the gas inlet, from bottom to top, in the order of the glass block (1-1), four thin glass sheets, and the glass block (1-10) stacked above, so that thin glass sheet one (1-4), thin glass sheet two (1-5), thin glass sheet three (1-6), and thin glass sheet four (1-7) are sandwiched in the middle, and assembled using vacuum glue.

[0010] To modulate the generated EUV spectrum by the periodic square groove structure within the flat plate, a waveguide adjustment device is used. This waveguide adjustment device consists of a platform or guide rail system (3-1) for precise control of position movement, a base or support structure (3-2) for stabilizing and fixing the equipment or components, a flat plate waveguide device with a periodic square groove structure (3-3), a gas supply system (3-4) for filling the flat plate waveguide with a periodic square groove structure with gas and using inert gas to propel the experiment, and a support or device (3-5) for adjusting the flat plate waveguide with a periodic square groove structure. The specific installation and adjustment steps are as follows:

[0011] Step 1: Install the planar waveguide device (3-3) with periodic square groove structure on the bracket or device (3-5) required for adjusting the planar waveguide with periodic square groove structure, and adjust the longitudinal angle of the planar waveguide device by adjusting the bracket or device required for adjusting the planar waveguide with periodic square groove structure.

[0012] Step 2: Install the bracket or device (3-5) required for adjusting the planar waveguide with periodic square groove structure on (3-1), and adjust the vertical position of the bracket or device required for adjusting the planar waveguide with periodic square groove structure and the waveguide device above by adjusting the platform or guide rail system used for precise control of position movement.

[0013] Step 3: Install the platform or guide rail system (3-1) for precise control of position movement on the base or support structure (3-2) for stabilizing and fixing the equipment or components. Adjust the lateral angle of the entire device by rotating the base or support structure for stabilizing and fixing the equipment or components, and adjust the front-back and left-right positions of the entire device by translating the base or support structure for stabilizing and fixing the equipment or components.

[0014] Step 4: Fill the flat waveguide with periodic square groove structure with gas and connect and seal the gas supply system (3-4) for the experiment using inert gas propulsion with the flat waveguide device (3-3) with periodic square groove structure.

[0015] Step 5: Adjust the vertical position of the planar waveguide device (3-3) with periodic square groove structure by adjusting the platform or guide rail system (3-1) used for precise control of position movement so that the planar waveguide opening is at the same height as the femtosecond laser. Adjust the front-back and left-right positions of the base or support structure (3-2) used for stabilizing and fixing the equipment or component so that the laser is aligned with the planar waveguide opening and the focal point is located inside the waveguide. Rotate the base or support structure (3-2) used for stabilizing and fixing the equipment or component and the bracket or device (3-5) required for adjusting the planar waveguide with periodic square groove structure to adjust the lateral and longitudinal angles of the planar waveguide with periodic square groove structure so that the femtosecond laser can pass through the planar waveguide. Then fix the base or support structure used for stabilizing and fixing the equipment or component in the vacuum target chamber.

[0016] The femtosecond laser enters the vacuum target chamber through a vacuum window, is reflected by two mirrors, and then focused by a focusing mirror. The focused femtosecond laser is coupled into a gas-filled planar waveguide with a periodic square groove structure, where it interacts with the inert gas to produce extreme ultraviolet radiation. The mixed beam of femtosecond laser and higher harmonics is emitted from the outlet of the planar waveguide with the periodic square groove structure and enters the spectrometer vacuum chamber. After the femtosecond laser is filtered out by a filter, only the extreme ultraviolet radiation remains. Finally, the extreme ultraviolet radiation is dispersed by a grating element and collected by the spectrometer.

[0017] The planar waveguide with a periodic square groove structure proposed in this invention can effectively improve the conversion efficiency of generating higher harmonics, achieving frequency-selective EUV radiation output. This device modulates the fundamental frequency light and inert gas through the periodic square groove structure inside the waveguide, successfully obtaining enhanced EUV radiation output compared to ordinary planar waveguides. Furthermore, compared to periodically and alternately arranged gas cells, the waveguide's inherent space limitations prevent drastic changes in vacuum during gas filling. Compared to reverse-transmission light pulse, multicolor field, and microelectrode modulation schemes, this scheme does not introduce additional equipment to complicate the entire device. Compared to the difficulty in fabricating and controlling the period of hollow capillaries with periodically varying inner diameters, this device, based on a planar waveguide, is easier to fabricate due to the square groove structure. This has significant value for its further engineering applications.

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and examples. These examples are only for explaining the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0019] The thickness of thin glass sheet one, thin glass sheet two, thin glass sheet three and thin glass sheet four in this invention is 0.2-1mm, and "higher order" refers to two or more times. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a planar waveguide device with a periodic square hole structure.

[0021] 1-1: Glass blocks stacked below; 1-2: Periodic square groove structure one; 1-3: Periodic square groove structure two; 1-4: Thin glass sheet one; 1-5: Thin glass sheet two; 1-6: Thin glass sheet three; 1-7: Thin glass sheet four; 1-8: Groove structure one forming a gas inlet; 1-9: Groove structure two forming a gas inlet; 1-13: Groove structure three forming a gas inlet; 1-14: Groove structure four forming a gas inlet; 1-10: Glass blocks stacked above; 1-11: Flat light outlet; 1-12: Flat light inlet.

[0022] Figure 2 The front and left views of a planar waveguide device with a periodic square hole structure.

[0023] 2-1: Gas inlet.

[0024] Figure 3 This is a schematic diagram of waveguide installation.

[0025] 3-1: Platform or guide rail system for precise control of position movement; 3-2: Base or support structure for stabilizing and fixing equipment or components; 3-3: Flat waveguide with periodic square groove structure; 3-4: Gas supply system for filling flat waveguide with periodic square groove structure with gas and using inert gas to propel experiments; 3-5: Support or device required for adjusting flat waveguide with periodic square groove structure.

[0026] Figure 4 This is a schematic diagram of the experimental optical path.

[0027] 4-1: Femtosecond laser; 4-2: Vacuum window; 4-3, 4-4: Reflector; 4-5: Vacuum target chamber; 4-6: Focusing lens; 4-7: Planar waveguide with periodic square groove structure; 4-8: Gas supply system for filling the planar waveguide with periodic square groove structure with gas and using inert gas to propel the experiment; 4-9: Mixed light of femtosecond laser and higher harmonics; 4-10: Filter; 4-11: Higher harmonics; 4-12: Vacuum chamber of spectrometer; 4-13: Grating element; 4-14: Extreme ultraviolet spectrometer.

[0028] Figure 5 The high-order harmonic spectra are shown for a planar waveguide without a periodic square groove structure and a planar waveguide with a periodic square groove structure. Detailed Implementation

[0029] The invention will now be further described with reference to the accompanying drawings.

[0030] The aforementioned planar waveguide with a periodic square groove structure is primarily composed of silicon dioxide. Two fused silica glass blocks, each measuring 15×10×2.5mm, have periodic square grooves with a depth of 0.05–0.08mm fabricated on their surfaces. The dimensions of each groove are close to its period (the distance between adjacent grooves, approximately 0.4–0.8mm). The groove used as the gas inlet is larger than the gas inlet tube, allowing the gas to be guided into the groove. Four ordinary thin glass sheets, approximately 0.2mm thick and 7×4.9mm in size, are also included. Figure 1 As shown in Figure (b), four thin glass sheets are arranged along the edge of the lower glass block in Figure (c). Since the combined glass sheets have a slightly smaller planar dimension than the glass block we used, a 1mm wide channel will appear at the center of the long side of the glass block, serving as a gas filling channel; while a channel slightly wider than the square hole will appear at the center of the short side of the glass block, serving as the light guiding channel of the waveguide, as shown in Figure (d). The square groove structure and gas inlet position on the two fused silica glass sheets are aligned vertically and sealed with vacuum glue to form a planar waveguide with a periodic square groove structure that allows gas to enter from the side and has a flat plate for light entry and exit. The left and front views of the structure are shown in Figure (c). Figure 2 As shown.

[0031] The aforementioned bracket or device for adjusting the planar waveguide with a periodic square groove structure is used to mount the planar waveguide and adjust its pitch angle so that the focused laser can be coupled into the planar waveguide with the periodic square groove structure.

[0032] The displacement stage is used to adjust the vertical displacement of the support or device required for the entire planar waveguide with periodic square groove structure, thereby adjusting the vertical position of the entire planar waveguide with periodic square groove structure so that the focused laser can be coupled into the planar waveguide with periodic square groove structure.

[0033] The fixed base is used to fix the displacement stage on it. By rotating and moving the fixed base, the angle and relative position of the waveguide relative to the laser beam can be adjusted, so that the focused laser can be coupled into the planar waveguide with a periodic square groove structure. Furthermore, by fixing the fixed base, the adjusted device can be stabilized.

[0034] The aforementioned air intake device is used to inflate the planar waveguide with a periodic square groove structure during the experiment.

[0035] The inert gases mentioned include helium, neon, argon, krypton, xenon, etc.

[0036] The core component of this invention is a planar waveguide device with a periodic square groove structure, composed of two glass blocks with periodic square groove structures and four thin glass sheets, as shown in the schematic diagram. Figure 1As shown in Figure (a), the upper surface of the glass block 1-1 stacked below has a periodic square groove structure 1-2 and two groove structures 1-8 and 1-9 reserved for forming gas inlets, as shown in the black shading; Figure (b) shows thin glass sheets 1, 2, 3 and 4 (1-4, 1-5, 1-6, 1-7) with a thickness of approximately 0.2 mm after processing; Figure (c) is similar to Figure (a), except that the periodic square groove structure 1-3 and the groove structures 1-13 and 1-14 reserved for forming gas inlets are made on the lower surface of the glass block 1-10 stacked above, as shown in the gray shading. The structures in Figures (a), (b) and (c) are stacked sequentially from bottom to top with edge alignment to form a top view of the structure shown in Figure (d), where 1-11 and 1-12 are the light outlet and light inlet of the planar waveguide, respectively.

[0037] Figure 2 The left image is a left view of a planar waveguide device with a periodic square groove structure, and the right image is a front view of the same device. 1-12 is the light inlet of the planar waveguide; 1-4, 1-6, and 1-7 are thin glass sheets one, three, and four sandwiched between two glass blocks; 2-1 is a groove for placing the gas tube, used to fill the planar waveguide with the periodic square groove structure with gas, serving as the gas inlet. Figure 1 The numbers 1-8 and 1-13 are formed by overlapping vertically.

[0038] In order for the incident femtosecond laser to be successfully coupled into the planar waveguide, it is necessary to Figure 3 The waveguide device shown is installed and adjusted as follows:

[0039] The first step is to install the planar waveguide device 3-3 with the periodic square groove structure on the bracket or device 3-5 required for adjusting the planar waveguide with the periodic square groove structure, so that the longitudinal angle of the planar waveguide device with the periodic square groove structure can be adjusted.

[0040] The second step is to install the bracket or device 3-5 required for adjusting the planar waveguide with periodic square groove structure on the platform or guide rail system 3-1 for precise control of position movement. The vertical position of the bracket or device required for adjusting the planar waveguide with periodic square groove structure and the waveguide device on it is controlled by adjusting the platform or guide rail system for precise control of position movement.

[0041] The third step is to install the platform or guide rail system 3-1 for precise control of position movement on the base or support structure 3-2 for stabilizing and fixing the equipment or components. The lateral angle of the entire device relative to the laser beam can be adjusted by rotating the base or support structure for stabilizing and fixing the equipment or components, and the relative position of the entire device with the focal point of the laser beam can be adjusted by translating the base or support structure for stabilizing and fixing the equipment or components.

[0042] Fourth, adjust the vertical position of the planar waveguide device 3-3 with the periodic square groove structure by adjusting the platform or guide rail system 3-1 used for precise position control, so that the planar waveguide opening is at the same height as the femtosecond laser. Adjust the position of the base or support structure 3-2 used for stabilizing and fixing the equipment or component so that the laser is aligned with the planar waveguide opening and the focal point is located inside the waveguide. Rotate the base or support structure 3-2 used for stabilizing and fixing the equipment or component and adjust the bracket or device 3-5 required for adjusting the planar waveguide with the periodic square groove structure to adjust the lateral and longitudinal angles of the planar waveguide with the periodic square groove structure so that the femtosecond laser can pass through the planar waveguide with the periodic square groove structure. Fix the base or support structure 3-2 used for stabilizing and fixing the equipment or component in the vacuum target chamber.

[0043] Figure 4 This is the experimental optical path diagram. The femtosecond laser 4-1 enters the vacuum target chamber 4-5 through the vacuum window. After being reflected by mirrors 4-3 and 4-4, it is focused by focusing mirror 4-6. The focused femtosecond laser is coupled into a gas-filled planar waveguide device 4-7 with a periodic square groove structure, where it interacts with the inert gas to produce extreme ultraviolet radiation. The mixed beam 4-9 of the femtosecond laser and higher harmonics is emitted from the outlet of the planar waveguide with the periodic square groove structure and enters the spectrometer vacuum chamber 4-12. After the femtosecond laser is filtered out by filter 4-10, only extreme ultraviolet radiation 4-11 remains. Finally, it is dispersed by grating element 4-13 and collected by spectrometer 4-14.

[0044] Figure 5This paper presents an experimental comparison of extreme ultraviolet (EUV) radiation generated by a conventional planar waveguide and a planar waveguide with a periodic square groove structure. It can be seen that compared to the planar waveguide without a periodic square groove structure, the EUV radiation obtained by the planar waveguide with a periodic square groove structure (800 μm period) shows a significant enhancement in the wavelength range of 9.8 nm–11.5 nm; the EUV radiation obtained by the planar waveguide with a periodic square groove structure (400 μm period) shows a significant enhancement in the wavelength range of 8.6 nm–11 nm. This indicates that the planar waveguide with a periodic square groove structure successfully controls EUV radiation through the modulation of laser drive and inert gas by the internal periodic square groove structure, achieving different wavelength distributions. Furthermore, a smaller period is more favorable for phase matching of short-wavelength harmonic orders, resulting in higher conversion efficiency for short-wavelength harmonics. This fully demonstrates the feasibility and effectiveness of this scheme.

Claims

1. A method for generating a frequency-selectable EUV light source using a planar waveguide with a periodic square groove structure, characterized in that: A planar waveguide with a periodic square groove structure is used as the gas carrier device for the gas filling. The device includes a glass block (1-1) stacked at the bottom and a glass block (1-10) stacked at the top, thin glass sheets one (1-4), two (1-5), three (1-6), and four (1-7). The thickness of thin glass sheets one, two, three, and four is 0.2-1 mm. The specific manufacturing steps are as follows: Step 1: Fabricate a glass block with a periodic square groove structure and a groove structure as a gas inlet: Fabricate a periodic square groove structure one (1-2) on the upper surface of the glass block (1-1) stacked below and a periodic square groove structure two (1-3) on the lower surface of the glass block (1-10) stacked above. Fabricate a groove structure one (1-8) and a groove structure two (1-9) forming a gas inlet on the edge of the glass block (1-1) stacked below. Fabricate a groove structure three (1-13) and a groove structure four (1-14) forming a gas inlet on the edge of the glass block (1-10) stacked above. Step 2: Fabrication of thin glass sheets: Based on the dimensions of the glass blocks stacked below (1-1) and above (1-10) processed in Step 1, and the structure fabricated on the surface of the glass blocks, fabricate thin glass sheets one (1-4), two (1-5), three (1-6), and four (1-7). Align the fabricated thin glass sheets with the edges of the four right angles of the glass block stacked below (1-1), forming a cross on the upper surface of the glass block stacked below (1-1) in the area not occupied by the thin glass sheets. By adjusting the spacing between thin glass sheets two (1-5) and four (1-7), and between thin glass sheets one (1-4) and three (1-6), the internal dimensions of the waveguide can be adjusted; by adjusting the spacing between thin glass sheets four (1-7) and one (1-4), and between thin glass sheets two (1-5) and three (1-6), the size of the gas inlet can be adjusted. Step 3: Assemble the planar waveguide with the periodic square groove structure; align the upper surface of the glass block (1-1) stacked below and the lower surface of the glass block (1-10) stacked above according to the periodic square groove structure one (1-2), periodic square groove structure two (1-3), and groove structure one (1-8), groove structure two (1-9), groove structure three (1-13), and groove structure four (1-14) used to form the gas inlet, from bottom to top, in the order of the glass block (1-1), four thin glass sheets, and the glass block (1-10) stacked above, so that thin glass sheet one (1-4), thin glass sheet two (1-5), thin glass sheet three (1-6), and thin glass sheet four (1-7) are sandwiched in the middle, and assembled using vacuum glue.

2. The method for generating a frequency-selectable EUV light source using a planar waveguide with a periodic square slot structure as described in claim 1, characterized in that: To modulate the generated EUV spectrum by the periodic square groove structure within the flat plate, a waveguide adjustment device is used. This waveguide adjustment device consists of a platform or guide rail system (3-1) for precise control of position movement, a base or support structure (3-2) for stabilizing and fixing the equipment or components, a flat plate waveguide device with a periodic square groove structure (3-3), a gas supply system (3-4) for filling the flat plate waveguide with a periodic square groove structure with gas and using inert gas to propel the experiment, and a support or device (3-5) for adjusting the flat plate waveguide with a periodic square groove structure. The specific installation and adjustment steps are as follows: Step 1: Install the planar waveguide device (3-3) with periodic square groove structure on the bracket or device (3-5) required for adjusting the planar waveguide with periodic square groove structure, and adjust the longitudinal angle of the planar waveguide device by adjusting the bracket or device required for adjusting the planar waveguide with periodic square groove structure. Step 2: Install the bracket or device (3-5) required for adjusting the planar waveguide with periodic square groove structure on the platform or guide rail system (3-1) for precise control of position movement. Adjust the vertical position of the bracket or device required for adjusting the planar waveguide with periodic square groove structure and the waveguide device above by adjusting the platform or guide rail system for precise control of position movement. Step 3: Install the platform or guide rail system (3-1) for precise control of position movement on the base or support structure (3-2) for stabilizing and fixing the equipment or components. Adjust the lateral angle of the entire device by rotating the base or support structure for stabilizing and fixing the equipment or components, and adjust the front-back and left-right positions of the entire device by translating the base or support structure for stabilizing and fixing the equipment or components. Step 4: Fill the flat waveguide with periodic square groove structure with gas and connect and seal the gas supply system (3-4) for the experiment using inert gas propulsion with the flat waveguide device (3-3) with periodic square groove structure. Step 5: Adjust the vertical position of the planar waveguide device (3-3) with periodic square groove structure by adjusting the platform or guide rail system (3-1) used for precise control of position movement so that the planar waveguide opening is at the same height as the femtosecond laser. Adjust the front-back and left-right positions of the base or support structure (3-2) used for stabilizing and fixing the equipment or component so that the laser is aligned with the planar waveguide opening and the focal point is located inside the waveguide. Rotate the base or support structure (3-2) used for stabilizing and fixing the equipment or component and the bracket or device (3-5) required for adjusting the planar waveguide with periodic square groove structure to adjust the lateral and longitudinal angles of the planar waveguide with periodic square groove structure so that the femtosecond laser can pass through the planar waveguide. Then fix the base or support structure used for stabilizing and fixing the equipment or component in the vacuum target chamber.

3. The method for generating a frequency-selectable EUV light source using a planar waveguide with a periodic square slot structure as described in claim 1, characterized in that: The femtosecond laser enters the vacuum target chamber through a vacuum window, is reflected by two mirrors, and then focused by a focusing mirror. The focused femtosecond laser is coupled into a gas-filled planar waveguide with a periodic square groove structure, where it interacts with the inert gas to produce extreme ultraviolet radiation. The mixed beam of femtosecond laser and higher harmonics is emitted from the outlet of the planar waveguide with the periodic square groove structure and enters the spectrometer vacuum chamber. After the femtosecond laser is filtered out by a filter, only the extreme ultraviolet radiation remains. Finally, the extreme ultraviolet radiation is dispersed by a grating element and collected by the spectrometer.

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