A co2 main pole pulse power amplification system

Abstract

The application discloses a CO2 main pole pulse power amplification system and relates to the technical field of lasers, comprising a seed source, an isolator, a light beam transmission module, a multistage CO2 amplifier and a control system. By adopting a CO2 Q-switched laser as the seed source, and sequentially feeding the pulse after isolation and light beam shaping into a multistage amplification chain modified by 4kW and 8kW CO2 lasers, under real-time monitoring and adjustment of the control system, stable amplification from microjoule nanosecond pulses to high-repetition-frequency output of hundreds of millijoules is realized, application requirements of generating 13.5 nanometer extreme ultraviolet light by using high-energy 10.6 micrometer pulse to bombard tin droplets are met, output energy, repetition frequency and light beam stability are taken into account, and the existing laser platform is utilized to reduce system construction and maintenance costs.

Description

Technical Field

[0001] This invention relates to the field of laser technology, specifically to a CO2 master pulse power amplification system. Background Technology

[0002] The master pulse power amplifier (MOPA) is a device that combines a seed source laser with an amplifier to generate pulsed lasers with high peak energy and high average power. The 10.6µm laser pulse bombards a tin droplet to generate 13.5nm extreme ultraviolet light, which is used to expose photoresist.

[0003] In the field of laser technology, high-energy, short-pulse laser sources are crucial for a variety of applications, particularly in extreme ultraviolet (EUV) lithography, materials processing, scientific research, and defense technology. Traditional laser generation methods often struggle to simultaneously meet the demands for high energy, short pulses, and high repetition rates, which limits the application potential of laser technology in certain areas.

[0004] CO2 lasers, as important gas lasers, are renowned for their high energy output, good beam quality, and relatively long lifespan. However, using a CO2 laser alone often makes it difficult to directly generate high-energy, short-pulse lasers that meet the requirements of specific applications. Therefore, an effective pulse power amplification system is needed to further enhance the energy and performance of the laser pulses.

[0005] Existing pulse power amplifier systems typically suffer from several problems, such as low amplification efficiency, high system complexity, and poor stability. These issues limit the practical application of the system, especially in situations requiring high energy, short pulses, and high repetition rates.

[0006] To address these issues, this invention proposes a CO2 master pulse power amplification system. This system achieves efficient and stable amplification of laser pulses by combining a seed source (Q-switched CO2 laser), an isolator, a beam transmission module, and a multi-stage CO2 laser amplifier (including 4kW and 8kW specifications). Through precise system design and debugging, it ensures accurate transmission of the laser beam and efficient utilization of energy. Summary of the Invention

[0007] Based on the shortcomings of the prior art described above, the purpose of this invention is to provide a CO2 master electrode pulse power amplification system to solve the above-mentioned technical problems.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a CO2 master electrode pulse power amplification system, comprising: Seed source, used to generate CO2 pulsed laser with a pulse width in the nanosecond range, a pulse energy in the microjoule range, and a repetition frequency that is adjustable within a preset range; An isolator, located at the light-emitting end of the seed source, is used to polarize and reshape the CO2 pulsed laser. The beam transmission module is located between the isolator and the multi-stage amplifier. It is used to expand or shrink the CO2 pulse laser output from the isolator to achieve spot matching and beam transmission between different amplification stages. The multi-stage amplifier comprises a preamplifier group and a postamplifier group. The preamplifier group consists of at least one modified 4-kilowatt CO2 laser, which is used to perform primary energy amplification of the CO2 pulsed laser output through the beam transmission module. The postamplifier group consists of at least one modified 8-kilowatt CO2 laser, which is used to perform high-energy amplification of the CO2 pulsed laser after the preamplifier group, thereby increasing the output pulse energy from the microjoule level to the hundred-millijoule level. The control system is electrically connected to the seed source, isolator, beam transmission module and multi-stage amplifier. It is used to set and adjust the operating parameters of each part, and adjust at least one operating parameter according to the feedback signal during system operation to obtain a stable output at the target pulse energy and repetition frequency.

[0009] The present invention is further configured such that the seed source is a CO2 Q-switched laser, and the repetition frequency is continuously adjustable between 10,000 times per second and 100,000 times per second.

[0010] The present invention is further configured such that the isolator comprises a combination of at least two of the following devices: an electro-optic crystal, an acousto-optic crystal, a saturable absorber, and a thin-film polarizer, for simultaneously achieving unidirectional isolation and shaping of the pulse leading and trailing edges.

[0011] The present invention is further configured such that the beam transmission module includes at least one set of zinc selenide lens assembly and / or copper reflector assembly, wherein the zinc selenide lens assembly is used to expand or shrink the CO2 pulse laser beam, and the copper reflector assembly is used to deflect the optical path between each amplification stage and control the position of the light spot.

[0012] The present invention is further configured such that the preamplifier group consists of five modified 4-kilowatt CO2 laser amplifiers connected in series, and the postamplifier group consists of four modified 8-kilowatt CO2 laser amplifiers connected in series. After the CO2 pulsed laser passes through the five 4-kilowatt CO2 laser amplifiers and the four 8-kilowatt CO2 laser amplifiers in sequence, the output pulse energy reaches the level of hundreds of millijoules.

[0013] The present invention is further configured such that the control system includes a monitoring unit and an adjustment unit; The monitoring unit is used to acquire operating parameters including at least output pulse energy, repetition frequency, and beam quality; The adjustment unit adjusts at least one of the following based on the operating parameters: the operating current of the seed source, the discharge current and gas pressure of each amplifier in the multi-stage amplifier, and the position of the optical elements of the beam transmission module.

[0014] The present invention is further configured to include a sampling monitoring optical path, which is used to separate a portion of the laser from the output beam of the multi-stage amplifier, introduce it into an energy detector and / or a waveform detector, and send the detection result to the control system for closed-loop control of the output energy stability and pulse shape.

[0015] The present invention is further configured such that the control system is configured to: acquire detection results of output pulse energy, pulse width, and pulse waveform from laser samples obtained from the sampling monitoring optical path, compare the detection results with a preset target range; when the output pulse energy or pulse width is detected to deviate from the preset target range, automatically adjust the driving current of the seed source and the discharge current and gas pressure of at least one amplifier in the multi-stage amplifier, and make minor corrections to the position of the optical elements in the beam transmission module according to the adjustment results, so that the output pulse energy and pulse width after step-by-step amplification are restored to the preset target range.

[0016] The present invention is further configured such that the system includes the following process during operation: The seed source is activated to generate an initial pulse laser with a pulse width in the nanosecond range, a pulse energy in the microjoule range, and a repetition frequency within a preset range. The pulse width, pulse energy, and repetition frequency are set and adjusted by the control system. The initial pulse laser is sequentially fed into the isolator, which isolates the initial pulse laser by polarization and shapes the pulse shape and peak power. After the shaped pulsed laser is expanded or contracted by the beam transmission module, it is guided into the previous 4 kW CO2 amplifier, where energy extraction and primary amplification are completed in the gain medium of the amplifier. The pulsed laser, amplified by the previous stage, is passed through the beam transmission module again and guided into the subsequent 4 kW or 8 kW CO2 amplifier. The energy extraction and amplification process is repeated in each stage of the amplifier. The control system monitors the output energy, pulse width, and repetition frequency parameters in real time during the amplification process and adjusts at least one operating parameter based on the monitoring results to ensure the stability and efficiency of the amplification process. After the pulsed laser is passed through a preset number of 4-kilowatt CO2 amplifiers and 8-kilowatt CO2 amplifiers to complete a total of nine stages of amplification, a CO2 pulsed laser with pulse energy reaching the level of hundreds of millijoules is output from the output of the last stage amplifier.

[0017] The present invention is further configured such that, after completing nine stages of amplification and outputting a CO2 pulse laser of the order of hundreds of millijoules by the last stage amplifier, the invention further includes: focusing the output pulse laser onto the surface of a metal tin target droplet in a vacuum cavity via a focusing optical system, so that the metal tin forms plasma under the action of a single pulse and radiates extreme ultraviolet light for photolithography exposure or other extreme ultraviolet light source applications.

[0018] This invention provides a CO2 master-electrode pulse power amplification system. A seed source is used to generate a CO2 pulsed laser with a pulse width in the nanosecond range, a pulse energy in the microjoule range, and an adjustable repetition frequency within a preset range. An isolator, located at the output end of the seed source, is used to polarize and shape the CO2 pulsed laser. A beam transmission module, located between the isolator and the multi-stage amplifier, is used to expand or shrink the CO2 pulsed laser output from the isolator, achieving spot matching and beam transmission between different amplification stages. The multi-stage amplifier includes a pre-amplifier group and a post-amplifier group. The pre-amplifier group consists of at least one modified 4-kilowatt CO2 laser, used for primary energy amplification of the CO2 pulsed laser output from the beam transmission module. The post-amplifier group consists of at least one modified 8-kilowatt CO2 laser, used for high-energy amplification of the CO2 pulsed laser after the pre-amplifier group. The system amplifies the output pulse energy from the microjoule level to the millijoule level. The control system, electrically connected to the seed source, isolator, beam transmission module, and multi-stage amplifier, is used to set and adjust the operating parameters of each component. During system operation, it adjusts at least one operating parameter based on feedback signals to obtain a stable output at the target pulse energy and repetition frequency. The beneficial effects include: increasing the initial pulse laser energy to the millijoule (mJ) level through cascaded amplification by multi-stage CO2 laser amplifiers (including 4kW and 8kW models); generating nanosecond (ns) level short pulse lasers using a seed source (Q-switched CO2 laser), and ensuring the final output laser pulse width remains within the ideal range through fine control during multi-stage amplification; and the design of the seed source and amplifiers allows the laser pulse repetition frequency to be tunable between 10kHz and 100kHz, meeting the needs of high-frequency laser applications.

[0019] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 A schematic diagram of a CO2 master electrode pulse power amplifier system is shown as an exemplary embodiment of the present invention. Figure 2 A schematic diagram of amplifier parameters is shown as an exemplary embodiment of the present invention; Figure 3 This is a flowchart illustrating system steps for an exemplary embodiment of the present invention. Detailed Implementation

[0021] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0022] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0023] In the following description, numerous details are explored to provide a more thorough explanation of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring embodiments of the invention.

[0024] A CO2 master pulse power amplification system is provided, which consists of a seed source, namely a CO2 Q-switched laser (1), an isolator (2), a beam transmission module (3), a 4kW CO2 laser amplifier (4), and an 8kW CO2 laser amplifier (5).

[0025] A CO2 Q-switched laser (1) is used to generate pulsed lasers with pulse width in the ns and pulse energy in the uJ range, and the repetition rate is tunable from 10kHz to 100kHz.

[0026] The isolator (2) is composed of an electro-optic crystal, an acousto-optic crystal, a saturable absorber, and a thin-film polarizer, and is mainly used for laser polarization isolation or pulse shaping.

[0027] The beam transmission module (3) is a laser beam expander or shrinker composed of a zinc selenide lens or a copper mirror.

[0028] The system generates pulsed laser from seed source (1) which enters amplifier (4) through isolator (2) and beam transmission module (3) to extract energy. After entering second-stage amplifier (4) through beam transmission module (3), the pulse energy reaches the level of hundreds of millijoules after a total of 9 stages of amplification by 5 4kW CO2 laser amplifiers (4) and 4 8kW CO2 laser amplifiers (5), which is used to bombard tin droplets to generate extreme ultraviolet light.

[0029] Input laser intensity I in (7) After amplification by the gain medium, where L is the length of the gain medium, the output I is obtained. out (8), I avail Where g is the available light intensity for the amplifier, g0 is the small-signal gain coefficient, and I... sat For the amplifier's saturation light intensity, g0 and I sat Empirical values ​​can be obtained experimentally.

[0030] The entire system output Pout is determined by the following two formulas:

[0031] .

[0032] Specifically, the seed source, namely a CO2 Q-switched laser (1), is used to generate pulsed lasers with pulse widths in the nanosecond (ns) range and pulse energies in the microjoule (uJ) range, and the repetition rate of the pulsed lasers is tunable between 10 kHz and 100 kHz. Isolator (2), which is composed of at least one of electro-optic crystal, acousto-optic crystal, saturable absorber and thin film polarizer, is used to realize laser polarization isolation or pulse shaping to ensure the stability and quality of laser signal; Beam transmission module (3), such as Figure 2 As shown, it consists of optical elements such as zinc selenide lenses or copper mirrors, and is used to expand or shrink laser beams to meet the needs of different amplification stages. At least one 4kW CO2 laser amplifier (4) is modified to receive pulsed laser light processed by isolator (2) and beam transmission module (3) and to extract and amplify its energy; At least one 8kW CO2 laser amplifier (5), which is also modified to further amplify the laser energy output by the 4kW CO2 laser amplifier (4); The pulsed laser generated by the seed source (1) sequentially passes through an isolator (2) and a beam transmission module (3) into the first-stage 4kW CO2 laser amplifier (4). After energy extraction, it passes through the beam transmission module (3) again into the next stage amplifier, until it passes through at least 5 4kW CO2 laser amplifiers (4) and at least 4 8kW CO2 laser amplifiers (5) in sequence, for a total of 9 stages of amplification. The final output pulsed laser energy reaches the level of hundreds of millijoules (mJ) and is used to bombard tin droplets to generate extreme ultraviolet light. The output light intensity of the system is... It is determined by the following formula: I out =I sat log e (1+e g 0 L (e Iin / Isat -1)) Formula 1 Formula 2 Formula 3 like Figure 2 As shown, the input laser intensity I in (7) After passing through the gain medium, where L is the length of the gain medium, the output I is amplified. out (8), I out and I in The relationship is given by formula 1, I avail Where g is the available light intensity for the amplifier, and g0 is the small-signal gain coefficient I. sat For the amplifier's saturation light intensity, g0 and I sat Empirical values ​​can be obtained experimentally. g0 and I sat This can be achieved by performing an amplification experiment with a single amplifier and fitting the curves of the amplifier's output and input light intensities. When the input I... in By comparing the smaller values ​​and scaling up the experiment, we can obtain: I out =e g o L I in Formula 4 From this, we can determine g0; When I in When the comparison is large: lim(I) in )I out =I in +g0LI sat Formula 5 Isat can be calculated from this.

[0033] The isolator (2) can be selected from different combinations of electro-optic crystals, acousto-optic crystals, saturable absorbers and thin-film polarizers according to actual needs to achieve the best polarization isolation effect and pulse shaping effect.

[0034] In the CO2 master pulse power amplification system, the optical components such as zinc selenide lenses or copper mirrors in the beam transmission module (3) can be adjusted according to the diameter of the laser beam, the divergence angle and the requirements of the amplifier to achieve the best laser beam transmission effect.

[0035] The number of the 4kW CO2 laser amplifier (4) and the 8kW CO2 laser amplifier (5) can be increased or decreased according to actual needs to meet the output requirements of different energy levels.

[0036] The system also includes a control system for controlling the working status of the seed source (1), isolator (2), beam transmission module (3), 4kW CO2 laser amplifier (4) and 8kW CO2 laser amplifier (5) to achieve precise output of laser pulses and stable amplification of energy.

[0037] All components of the system are installed and adjusted using precise mechanical structures and optical adjustment devices to ensure accurate transmission of the laser beam and efficient amplification of energy.

[0038] The specific implementation steps of the system are as follows: Figure 3 As shown, it includes: S1: Start the seed source: First, start the CO2 Q-switched laser (seed source), which is set to generate an initial pulse laser with a pulse width in the nanosecond range and a pulse energy in the microjoule range.

[0039] Adjusting parameters: As needed, adjust the output parameters of the seed source, such as pulse width, pulse energy and repetition frequency, through the control system to ensure that the generated initial pulse laser meets the requirements of the subsequent amplification process.

[0040] S2: Polarization Isolation: After the laser pulse is emitted from the seed source, it first passes through an isolator. The isolator consists of an electro-optic crystal, an acousto-optic crystal, a saturable absorber, and a thin-film polarizer, etc., and is used to achieve polarization isolation of the laser, ensuring the purity and stability of the laser signal.

[0041] Pulse shaping: At the same time, the isolator can also shape the laser pulse, adjusting its shape and peak power to optimize the effect of subsequent amplification.

[0042] S3: Beam transmission: The laser pulses pre-processed by the isolator are expanded or contracted by the beam transmission module (such as a zinc selenide lens or a copper mirror) to meet the input requirements of the first-stage amplifier.

[0043] Energy Extraction and Amplification: After the laser pulse enters the first-stage 4kW CO2 laser amplifier, stimulated emission occurs in the gain medium, extracting and amplifying the energy. The amplifier's gain medium and pump source work together to ensure that the laser pulse obtains sufficient energy gain during the amplification process.

[0044] S4: Step-by-step transmission: After the first stage of amplification, the laser pulse passes through the beam transmission module again and enters the next stage amplifier (which may be a 4kW or 8kW CO2 laser amplifier).

[0045] Energy accumulation: In each stage of the amplifier, the laser pulse undergoes a similar energy extraction and amplification process. As the number of stages increases, the energy of the laser pulse gradually accumulates, reaching a higher level.

[0046] Monitoring and Adjustment: During the amplification process, the control system monitors the parameters of the laser pulse (such as energy, pulse width, and repetition frequency) in real time and makes adjustments as needed to ensure the stability and efficiency of the amplification process.

[0047] S5: Amplification complete: After a total of 9 stages of amplification (including 5 4kW and 4 8kW CO2 laser amplifiers), the energy of the laser pulse reaches the level of hundreds of millijoules, meeting the needs of high-energy applications.

[0048] Output and Application: The final amplified laser pulse is output through the output terminal of the last stage amplifier.

[0049] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A CO2 master electrode pulse power amplification system, characterized in that, include: Seed source, used to generate CO2 pulsed laser with a pulse width in the nanosecond range, a pulse energy in the microjoule range, and a repetition frequency that is adjustable within a preset range; An isolator, located at the light-emitting end of the seed source, is used to polarize and reshape the CO2 pulsed laser. The beam transmission module is located between the isolator and the multi-stage amplifier. It is used to expand or shrink the CO2 pulse laser output from the isolator to achieve spot matching and beam transmission between different amplification stages. The multi-stage amplifier comprises a preamplifier group and a postamplifier group. The preamplifier group consists of at least one modified 4-kilowatt CO2 laser, which is used to perform primary energy amplification of the CO2 pulsed laser output through the beam transmission module. The postamplifier group consists of at least one modified 8-kilowatt CO2 laser, which is used to perform high-energy amplification of the CO2 pulsed laser after the preamplifier group, thereby increasing the output pulse energy from the microjoule level to the hundred-millijoule level. The control system is electrically connected to the seed source, isolator, beam transmission module and multi-stage amplifier. It is used to set and adjust the operating parameters of each part, and adjust at least one operating parameter according to the feedback signal during system operation to obtain a stable output at the target pulse energy and repetition frequency.

2. The CO2 master electrode pulse power amplification system according to claim 1, characterized in that, The seed source is a CO2 Q-switched laser, and the repetition frequency is continuously adjustable between 10,000 times per second and 100,000 times per second.

3. The CO2 master electrode pulse power amplification system according to claim 1, characterized in that, The isolator comprises a combination of at least two of the following devices: electro-optic crystal, acousto-optic crystal, saturable absorber, and thin-film polarizer, for simultaneously achieving unidirectional isolation and shaping of the pulse leading and trailing edges.

4. The CO2 master electrode pulse power amplification system according to claim 1, characterized in that, The beam transmission module includes at least one set of zinc selenide lens assembly and / or copper reflector assembly. The zinc selenide lens assembly is used to expand or shrink the CO2 pulsed laser beam, and the copper reflector assembly is used to deflect the optical path between each amplification stage and control the position of the light spot.

5. The CO2 master electrode pulse power amplification system according to claim 1, characterized in that, The preamplifier group consists of five modified 4-kilowatt CO2 laser amplifiers connected in series, and the postamplifier group consists of four modified 8-kilowatt CO2 laser amplifiers connected in series. The CO2 pulsed laser passes through the five 4-kilowatt CO2 laser amplifiers and the four 8-kilowatt CO2 laser amplifiers in sequence, and the output pulse energy reaches the level of hundreds of millijoules.

6. The CO2 master electrode pulse power amplification system according to claim 1, characterized in that, The control system includes a monitoring unit and an adjustment unit; The monitoring unit is used to acquire operating parameters including at least output pulse energy, repetition frequency, and beam quality; The adjustment unit adjusts at least one of the following based on the operating parameters: the operating current of the seed source, the discharge current and gas pressure of each amplifier in the multi-stage amplifier, and the position of the optical elements of the beam transmission module.

7. The CO2 master electrode pulse power amplification system according to claim 1, characterized in that, It also includes a sampling monitoring optical path, which is used to separate a portion of the laser from the output beam of the multi-stage amplifier, introduce it into an energy detector and / or a waveform detector, and send the detection result to the control system for closed-loop control of the output energy stability and pulse shape.

8. A CO2 master electrode pulse power amplification system according to claim 7, characterized in that, The control system is configured to: acquire detection results of output pulse energy, pulse width and pulse waveform from laser samples obtained from the sampling monitoring optical path, and compare the detection results with a preset target range; When the output pulse energy or pulse width is detected to deviate from the preset target range, the driving current of the seed source and the discharge current and gas pressure of at least one amplifier in the multi-stage amplifier are automatically adjusted, and the position of the optical element in the beam transmission module is slightly corrected according to the adjustment result, so that the output pulse energy and pulse width after step-by-step amplification are restored to the preset target range.

9. A CO2 master electrode pulse power amplification system according to claim 8, characterized in that, The system includes the following processes during operation: The seed source is activated to generate an initial pulse laser with a pulse width in the nanosecond range, a pulse energy in the microjoule range, and a repetition frequency within a preset range. The pulse width, pulse energy, and repetition frequency are set and adjusted by the control system. The initial pulse laser is sequentially fed into the isolator, which isolates the initial pulse laser by polarization and shapes the pulse shape and peak power. After the shaped pulsed laser is expanded or contracted by the beam transmission module, it is guided into the previous 4 kW CO2 amplifier, where energy extraction and primary amplification are completed in the gain medium of the amplifier. The pulsed laser, amplified by the previous stage, is passed through the beam transmission module again and guided into the subsequent 4 kW or 8 kW CO2 amplifier. The energy extraction and amplification process is repeated in each stage of the amplifier. The control system monitors the output energy, pulse width, and repetition frequency parameters in real time during the amplification process and adjusts at least one operating parameter based on the monitoring results to ensure the stability and efficiency of the amplification process. After the pulsed laser is passed through a preset number of 4-kilowatt CO2 amplifiers and 8-kilowatt CO2 amplifiers to complete a total of nine stages of amplification, a CO2 pulsed laser with pulse energy reaching the level of hundreds of millijoules is output from the output of the last stage amplifier.

10. A CO2 master electrode pulse power amplification system according to claim 9, characterized in that, After completing nine stages of amplification and outputting a CO2 pulsed laser at the level of hundreds of millijoules by the last stage amplifier, the process further includes: focusing the output pulsed laser onto the surface of a metal tin target droplet in a vacuum cavity via a focusing optical system, causing the metal tin to form plasma under the action of a single pulse and radiate extreme ultraviolet light for photolithography exposure or other extreme ultraviolet light source applications.

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