Refractive-reflective focusing laser plasma light source

Abstract

This invention relates to a laser plasma source with refraction, reflection, and focusing, comprising a shaping assembly, a refraction focusing assembly, a gas chamber, a reflection focusing assembly, and an exit window. The shaping assembly includes a conical lens group or an aspherical lens, through which the laser beam is formed into a ring beam. The refraction focusing assembly includes several lenses that focus the ring beam onto the gas chamber to generate and maintain plasma. The reflection focusing assembly includes a reflector and an ellipsoidal mirror; the gas chamber is placed at the first focal point of the ellipsoidal mirror; the laser beam passing through the plasma is reflected by the reflector to the ellipsoidal mirror, and then focused onto the plasma after a second reflection by the ellipsoidal mirror; the ultraviolet and visible light generated by the plasma are reflected by the ellipsoidal mirror and focused onto a second focal point through the exit window, which has high infrared reflectivity. Compared with existing technologies, this invention eliminates the ultraviolet reflection-infrared transmission beam splitter, reducing the complexity of the optical system and significantly reducing the cost of optical components.

Description

Technical Field

[0001] This application relates to the field of optical equipment technology, and in particular to a laser plasma source that uses refraction, reflection and focusing. Background Technology

[0002] Laser-excited plasma (also known as laser-sustaining plasma) source technology is an advanced light source technology. Its core principle involves focusing a high-power laser beam into a high-pressure rare gas, generating and maintaining a high-temperature plasma through absorption mechanisms such as inverse bremsstrahlung, thereby emitting high-brightness, broad-spectrum continuous radiation. Parameters such as the wavelength, power, and focusing method of the pump laser directly affect the temperature, size, and stability of the plasma; optimizing the laser optical path can effectively improve the performance of the plasma source. With its advantages of high brightness, broad spectral coverage, and long lifespan, laser-excited plasma sources are gradually becoming a new generation of light source technology to replace traditional arc lamps, holding an irreplaceable position in fields such as semiconductor wafer inspection, microscopic imaging, and spectral analysis.

[0003] In existing high-power laser-excited plasma source technologies (kilowatts and above), the pump laser typically employs a single-reflection focusing optical structure, as shown in CN202080070435, CN202480042851, and CN202510520373. However, this single-reflection focusing optical structure requires a beam-splitting optical device that can transmit infrared laser light and reflect ultraviolet-visible light, commonly known as a cold mirror or dichroic mirror. The coating of this optical device is very complex, and its large size makes it very expensive, while also affecting heat dissipation within the light source chamber. If this optical device could be eliminated from the optical structure, the cost of optical components in high-power laser-excited plasma sources could be significantly reduced, and the heat dissipation efficiency within the light source could be improved. Summary of the Invention

[0004] This invention is based on the above-mentioned prior art and provides a laser plasma source that is refracted, reflected and focused.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A laser plasma source with refraction, reflection and focusing includes a shaping component, a refraction and focusing component, a gas chamber, a reflection and focusing component and a light output window; the laser beam is formed into a ring beam by the shaping component; the refraction and focusing component focuses the ring beam onto the gas chamber to maintain the plasma; the reflection and focusing component includes a reflector and an ellipsoidal mirror, the center of the gas chamber is located at the first focus of the ellipsoidal mirror, the ring beam laser beam passing through the plasma is reflected by the reflector to the ellipsoidal mirror, and then focused onto the plasma after a second reflection by the ellipsoidal mirror, the ultraviolet light and visible light generated by the plasma are reflected by the ellipsoidal mirror and focused onto the second focus through the light output window (5), the light output window has high infrared reflectivity.

[0007] Furthermore, the reflector and ellipsoidal mirror surfaces of the reflection focusing assembly are placed opposite each other.

[0008] Furthermore, the reflector has a surface shape that is one of a sphere, an aspherical surface, or a freeform surface.

[0009] Furthermore, the coating of the reflective focusing component has high reflectivity in the infrared laser spectrum range and also in the ultraviolet-visible light range.

[0010] Furthermore, the light-emitting window is positioned between the second focal point of the reflector and the ellipsoidal mirror. After being focused by the reflection and focusing assembly, the ultraviolet-visible light emitted by the plasma can pass through the light-emitting window to reach the focal point. The coating of the light-emitting window has high transmittance in the ultraviolet-visible light range and high reflectance in the infrared laser range.

[0011] Furthermore, the shaping component includes a conical lens group or an aspherical lens, and the pump laser can form a ring beam after passing through the shaping component.

[0012] Furthermore, the shaping component includes a spherical lens, a first conical lens, and a second conical lens. The spherical lens is a plano-convex lens, and both the first and second conical lenses are convex conical lenses.

[0013] Furthermore, the refractive focusing assembly includes one or more lenses that can focus the annular beam onto the plasma.

[0014] Furthermore, the refractive focusing assembly includes multiple lenses whose surface shape is one or more combinations of spherical, aspherical, and freeform surfaces.

[0015] Furthermore, the refractive focusing assembly includes a plano-convex lens.

[0016] Furthermore, the lens material of the shaping component and the lens material of the refractive focusing component are one or more of fused silica glass, synthetic silica glass, calcium fluoride, magnesium fluoride, and sapphire.

[0017] Furthermore, the lens coating of the shaping component and the lens coating of the refractive focusing component are antireflective coatings.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] This invention eliminates the ultraviolet reflection-infrared transmission beam splitter, reducing the complexity of the optical system and significantly lowering the cost of optical components.

[0020] This invention uses ring light as the shaping laser, avoiding the risk of the central beam reflecting back to the laser and burning out the fiber optic head or the laser.

[0021] This invention maintains plasma through multiple focusing of refracted and reflected laser light, efficiently utilizing laser energy. The laser beam is formed into a ring beam by a shaping component, which increases the laser power reflected to the ellipsoidal mirror, resulting in more secondary reflections. Laser refraction and focusing do not completely absorb the plasma; secondary focusing and absorption through reflection improves efficiency. The coaxial focusing method of refraction and reflection restricts the plasma shape, increasing plasma luminescence efficiency. Improved laser utilization reduces excess heat loss, thus reducing the load on the heat dissipation system. Using an elliptical aspherical cavity to collect plasma radiation allows for a more compact structure. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a refractive, reflective, and focused laser plasma source according to Embodiment 1 of the present invention.

[0023] Figure 2 This is a schematic diagram of the incoherent irradiance linear distribution of the laser focused spot in the plasma section, which is an embodiment of this application.

[0024] Figure 3 This is a schematic diagram of the non-linear distribution of incoherent irradiance of the laser focused spot in the plasma section, which is an embodiment of this application.

[0025] Figure 4 This is a detailed view of the gas chamber in Embodiment 1 of the present invention.

[0026] Figure 5 This is a schematic diagram of the structure of a refractive, reflective, and focused laser plasma source according to Embodiment 2 of the present invention.

[0027] Figure 6 This is a schematic diagram of the incoherent irradiance linear distribution of the laser focused spot in the plasma section in Embodiment 2 of this application.

[0028] Figure 7 This is a schematic diagram of the non-linear distribution of incoherent irradiance of the laser focused spot in the plasma section, which is an embodiment of this application.

[0029] 1. Shaping assembly; 11. Spherical lens; 12. First conical lens; 13. Second conical lens; 2. Refraction focusing assembly; 21. Plano-convex lens; 31. Gas chamber; 311. Electrode; 312. Glass spherical shell; 32. Plasma; 4. Reflection focusing assembly; 41. Mirror; 42. Ellipsoidal mirror; 5. Light exit window; 6. Second focal point; 7. Laser. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0031] Example 1

[0032] Embodiment 1 of this application provides a laser plasma source that uses refraction, reflection, and focusing. Figure 1 As shown, the system includes a shaping component 1, a refractive focusing component 2, a gas chamber 31, a reflective focusing component 4, and a light-emitting window 5.

[0033] Laser 7 emits a pump laser, primarily infrared laser, which illuminates shaping component 1. Shaping component 1 includes a spherical lens 11 and a conical lens group, the conical lens group comprising a first conical lens 12 and a second conical lens 13. In a preferred embodiment, the spherical lens 11 is a plano-convex lens. In this embodiment, the pump laser is collimated into a parallel beam after passing through the spherical lens 11, and then shaped into a parallel annular beam after passing through the first conical lens 12 and the second conical lens 13 with their tips facing each other.

[0034] The shaped ring pump laser passes through the refraction focusing assembly 2 and is focused into the gas chamber 31, maintaining the state of the plasma 32. The refraction focusing assembly 2 includes a plano-convex lens 21 made of quartz material, which can focus the passing ring pump laser. The gas chamber 31 may include an electrode 311 and a glass spherical shell 312, and the gas chamber 31 can withstand high-temperature and high-pressure gas.

[0035] The ring laser beam passing through plasma 32 is refocused onto plasma 32 by the reflection focusing assembly 4. The reflection focusing assembly 4 includes a reflector 41 and an ellipsoidal mirror 42, both placed with their curved surfaces facing each other, where the reflector 41 is a spherical reflector. The gas chamber 31 is placed at the first focal point of the ellipsoidal mirror 42, meaning plasma 32 is located at the first focal point. Reflector 41 and ellipsoidal mirror 42 have high reflectivity within the infrared laser spectrum. The ring laser beam passing through plasma is reflected by reflector 41 onto ellipsoidal mirror 42, and then refocused onto plasma 32 by ellipsoidal mirror 42. The ring beam avoids damage to the fiber optic cable and laser caused by axial reflection of the laser beam by reflector 41. The light radiated from plasma 32 is focused onto the second focal point 6 of ellipsoidal mirror 42 through the exit window 5. The exit window 5 is made of a high-transmittance material for ultraviolet light and also has high infrared reflectivity to ensure that the emitted light is the desired ultraviolet-visible light generated by plasma 32. The incoherent irradiance distribution of the focused spot at the plasma 32 location is as follows: Figure 2 , Figure 3 As shown.

[0036] Figure 4 This is a detailed view of the gas chamber in this embodiment. It can be seen that the plasma is located between the two electrodes within the gas chamber. The ring laser used in this invention can, on the one hand, increase the reflected light intensity of the reflector 41, allowing more laser light to be refocused onto the plasma 32; on the other hand, it can avoid problems such as the laser irradiating the electrodes and causing them to overheat and burn out.

[0037] Example 2

[0038] This second embodiment provides a laser plasma source with refraction, reflection, and focusing. Components with the same or similar structure or function as those in the first embodiment are labeled with the same reference numerals, and specific descriptions of these components are omitted.

[0039] Embodiment 2 of this application provides a laser plasma source that uses refraction, reflection, and focusing. Figure 5 As shown, the system includes a shaping component 1, a refractive focusing component 2, a gas chamber 31, a reflective focusing component 4, and a light exit window 5. The ring pump laser generated by the TEM01* laser 7 is collimated into a parallel ring beam by the spherical lens 11. In a preferred embodiment, the spherical lens 11 is a plano-convex lens. A schematic diagram of the incoherent irradiance distribution of the focused spot at the plasma position 32 is shown below. Figure 6 , Figure 7 As shown.

[0040] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should fall within the protection scope of the present invention.

Claims

1. A laser plasma source with refraction, reflection, and focusing, characterized in that, The device includes a shaping component (1), a refraction focusing component (2), a gas chamber (31), a reflection focusing component (4), and a light-emitting window (5). The laser beam is formed into a ring beam by the shaping component (1). The refraction focusing component (2) focuses the ring beam onto the gas chamber (31) to generate and maintain plasma (32). The reflection focusing component (4) includes a reflector (41) and an ellipsoidal mirror (42). The center of the gas chamber (31) is located at the first focal point of the ellipsoidal mirror (42). The ring beam laser beam passing through the plasma (32) is reflected by the reflector (41) to the ellipsoidal mirror (42), and then focused onto the plasma (32) after a second reflection by the ellipsoidal mirror (42). The ultraviolet light and visible light generated by the plasma (32) are reflected by the ellipsoidal mirror (42) and focused onto the second focal point (6) through the light-emitting window (5). The light-emitting window (5) has high infrared reflectivity.

2. The laser plasma source with refraction, reflection, and focusing according to claim 1, characterized in that, The reflective surfaces of the reflective focusing assembly (4) and the ellipsoidal mirror (42) are placed opposite each other.

3. The laser plasma source with refraction, reflection, and focusing according to claim 2, characterized in that, The surface shape of the reflector (41) is one of spherical, aspherical and freeform surfaces.

4. The laser plasma source with refraction, reflection, and focusing according to claim 2, characterized in that, The coating of the reflective focusing component (4) has high reflectivity in the infrared laser spectrum range and also in the ultraviolet-visible light range.

5. The laser plasma source with refraction, reflection, and focusing according to claim 1, characterized in that, The light-emitting window (5) is positioned between the second focal point (6) of the reflector (41) and the ellipsoidal mirror (42). After the ultraviolet-visible light emitted by the plasma (32) is focused by the reflection focusing component (4), it can pass through the light-emitting window (5) to reach the second focal point (6). The coating of the light-emitting window (5) has high transmittance in the ultraviolet-visible light range and high reflectance in the infrared laser range.

6. The laser plasma source with refraction, reflection, and focusing according to claim 1, characterized in that, The shaping component (1) includes a conical lens group or an aspherical lens, and the pump laser can form a ring beam after passing through the shaping component (1).

7. The laser plasma source with refraction, reflection, and focusing according to claim 6, characterized in that, The shaping component (1) includes a spherical lens (11), a first conical lens (12) and a second conical lens (13). The spherical lens (11) is a plano-convex lens, and the first conical lens (12) and the second conical lens (13) are both convex conical lenses.

8. The laser plasma source with refraction, reflection, and focusing according to claim 1, characterized in that, The refractive focusing assembly (2) includes one or more lenses, which can focus the annular beam onto the plasma.

9. The laser plasma source with refraction, reflection, and focusing according to claim 8, characterized in that, The refractive focusing assembly (2) includes multiple lenses whose surface shape is one or more combinations of spherical, aspherical and freeform surfaces.

10. The laser plasma source with refraction, reflection, and focusing according to claim 8, characterized in that, The refractive focusing assembly (2) includes a plano-convex lens (21).

11. The laser plasma source with refraction, reflection, and focusing according to claim 1, characterized in that, The lens material of the shaping component (1) and the lens material of the refractive focusing component (2) are one or more of fused silica glass, synthetic silica glass, calcium fluoride, magnesium fluoride and sapphire.

12. The laser plasma source with refraction, reflection, and focusing according to claim 1, characterized in that, The lens coatings of the shaping component (1) and the refractive focusing component (2) are anti-reflective coatings.

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