Laser plasma light source

Abstract

This invention relates to a laser plasma source, comprising a housing with an internally formed sealed cavity for containing a working gas, having a light input section and an output window thereon; an ellipsoidal reflector disposed within the sealed cavity, the ellipsoidal reflector having a first focal point and a second focal point, the first focal point being located within the sealed cavity, the region of the first focal point constituting a plasma generation region; an optical component disposed on the propagation path of a pump laser, used to shape the pump laser input from the light input section, so that the pump laser is focused to the first focal point directly or after being reflected by the ellipsoidal reflector; and a reflective element disposed within the sealed cavity, located on the propagation path of plasma light emitted from the plasma at the first focal point and reflected by the ellipsoidal reflector, the plasma light after being refracted by the reflective element being focused at a refracted equivalent focal point through the output window, the refracted equivalent focal point corresponding to the equivalent position of the second focal point after being refracted by the reflective element.

Description

Technical Field

[0001] This invention relates to the field of laser plasma source technology. Background Technology

[0002] Laser plasma sources are light sources that use pump lasers to excite and maintain plasma in a working gas, thereby generating high-brightness broadband radiation. Their output spectrum can cover ultraviolet, deep ultraviolet, vacuum ultraviolet and visible light bands, and are suitable for semiconductor quantity detection, high-resolution imaging, spectral analysis and other fields.

[0003] Existing laser plasma sources typically use a quartz glass bulb as a container for the high-pressure working gas, and external optical elements focus the pump laser into the bulb to excite and maintain the plasma. While this structure can achieve high-brightness broadband radiation, it still has shortcomings under high pressure, high laser power, and long-term operation conditions: First, the pressure resistance and thermal conductivity of the quartz glass bulb are limited, and the heat generated during plasma operation is not easily dissipated in time, which can easily affect the thermal stability and safety of the light source; second, the gas composition and pressure inside the sealed bulb are usually difficult to adjust flexibly during operation, limiting the optimization of the light source under different start-up and stable output conditions.

[0004] Furthermore, in lampless laser plasma sources, if the working gas pressure or composition needs to be dynamically changed, the refractive index of the working gas and the temperature distribution within the cavity will change accordingly. This can cause focus drift, thermal lensing, or convection aberrations as the pump laser propagates within the cavity, making it difficult for the pump laser to be stably focused on the predetermined plasma generation region. This affects the plasma's positional stability, light collection efficiency, and output light coupling efficiency. Simultaneously, the collection, deflection, and output of plasma light typically require complex external optical systems, resulting in a large overall structure and high assembly difficulty for the light source.

[0005] Therefore, it is necessary to provide a laser plasma source that can carry working gas, integrate plasma light collection and folding output structure within the cavity, and adapt to high-pressure and high-power operating conditions, so as to improve the pressure resistance, heat dissipation, optical path compactness and output stability of the source. Summary of the Invention

[0006] The purpose of this invention is to provide a laser plasma light source that solves the problems of limited pressure resistance and heat dissipation capacity of existing quartz glass bulbs, difficulty in flexibly adjusting gas pressure or composition, easy drift of pump laser focus caused by dynamic gas state changes, and complex plasma light collection and output structure.

[0007] This invention discloses a laser plasma light source, comprising:

[0008] The housing (101) has a sealed cavity inside for containing working gas, and the housing (101) is provided with a light input section and an output window (107).

[0009] An ellipsoidal reflector (102) is disposed in the sealed cavity. The ellipsoidal reflector (102) has a first focal point (106) and a second focal point. The first focal point (106) is located in the sealed cavity, and the area where the first focal point (106) is located constitutes a plasma generation area.

[0010] An optical component (104) is disposed in the propagation path of the pump laser and is used to shape the pump laser input by the light input unit, so that the pump laser is focused to the first focal point (106) directly or after being reflected by the ellipsoidal mirror (102); and

[0011] A reflective element (105) is disposed in the sealed cavity and located on the propagation path of the plasma light emitted from the plasma at the first focal point (106) and reflected by the ellipsoidal reflector (102). The plasma light after being refracted by the reflective element (105) converges at the refracted equivalent focal point (108) through the exit window (107). The refracted equivalent focal point (108) corresponds to the equivalent position of the second focal point after being refracted by the reflective element (105).

[0012] According to the laser plasma light source of the present invention, the reflective element (105) is a dichroic mirror, which transmits the pump laser and reflects the plasma light;

[0013] The optical component (104) includes a collimation system and / or a beam expander system for positioning the pump laser, after passing through the reflective element (105), at the equivalent source point of the ellipsoidal mirror (102) relative to the second focal point or the equivalent position of the second focal point.

[0014] The pump laser passes through the reflective element (105) and is incident on the ellipsoidal reflector (102), and is reflected by the ellipsoidal reflector (102) and converged to the first focal point (106).

[0015] The plasma light generated at the first focal point (106) is collected by the ellipsoidal reflector (102) and then reflected by the reflective element (105) toward the exit window (107).

[0016] The laser plasma light source according to the present invention further includes a control system and an adjustable mounting base:

[0017] At least one of the optical component (104), the reflective element (105), and the ellipsoidal reflector (102) is mounted on the adjustable mounting base;

[0018] The control system determines the offset of the focusing position of the pump laser relative to the first focal point (106) based on the gas state data and / or temperature data in the sealed cavity, and drives the adjustable mounting base to adjust the position or angle according to the offset.

[0019] According to the laser plasma light source of the present invention, the ellipsoidal reflector (102) is mounted on a mirror mount that is displaceable along its optical axis;

[0020] The control system drives the mirror mount to move along the optical axis according to the offset, so that the focusing position of the pump laser coincides with the first focal point (106) or is located in a predetermined neighborhood of the first focal point (106).

[0021] The laser plasma light source according to the present invention further includes a gas conditioning system, the gas conditioning system comprising:

[0022] Gas mixing chamber (109) is used to contain one working gas or to mix multiple working gases in a set ratio;

[0023] An air inlet pipe (110) connects the gas mixing chamber (109) and the sealed chamber, and an air inlet valve (111) is provided on the air inlet pipe (110).

[0024] A vent pipe (112) is connected to the sealed cavity, and a vent pipe valve (113) is provided on the vent pipe (112); and

[0025] A barometer (114) is installed on the vent pipe (112) or the sealed cavity to detect the gas pressure inside the sealed cavity.

[0026] The laser plasma light source according to the present invention further includes a control system:

[0027] The control system is electrically connected to the gas mixing chamber (109), the inlet valve (111), the outlet valve (113), and the barometer (114), respectively.

[0028] The control system controls the inlet valve (111) and the outlet valve (113) based on the pressure data fed back by the barometer (114), and controls the gas distribution state of the gas mixing chamber (109) based on the gas composition setting data.

[0029] According to the laser plasma light source of the present invention, the housing (101) is provided with a cooling channel or a cooling jacket; and / or,

[0030] At least one of the ellipsoidal reflector (102), the reflective element (105), and the optical assembly (104) is provided with a heat-conducting base or a water-cooling structure.

[0031] According to the laser plasma light source of the present invention, the optical component (104) includes one or more of a collimating lens, a beam expander group, a focusing lens, a reflecting mirror, an aspherical lens, or a beam shaping element.

[0032] According to the laser plasma light source of the present invention, the exit window (107) is made of calcium fluoride, magnesium fluoride, sapphire, or ultraviolet-grade fused silica; and

[0033] The working gas is one or more of the following: xenon, argon, krypton, neon, and helium.

[0034] According to the laser plasma light source of the present invention, the housing (101) is made of metal, ceramic material, or quartz material. The main differences and effects of the embodiments of the present invention compared with the prior art are as follows:

[0035] In this invention, a laser plasma source includes a housing with an internally sealed cavity for containing a working gas, and a light input section and an output window thereon; an ellipsoidal reflector disposed within the sealed cavity, the ellipsoidal reflector having a first focal point and a second focal point, the first focal point being located within the sealed cavity, and the region where the first focal point is located constituting a plasma generation region; an optical component disposed on the propagation path of the pump laser, used to shape the pump laser input from the light input section, so that the pump laser is focused to the first focal point directly or after being reflected by the ellipsoidal reflector; and a reflecting element disposed within the sealed cavity, located on the propagation path of the plasma light emitted from the plasma at the first focal point and reflected by the ellipsoidal reflector, the plasma light after being refracted by the reflecting element being focused at the refracted equivalent focal point through the output window, the refracted equivalent focal point corresponding to the equivalent position of the second focal point after being refracted by the reflecting element. This improves the pressure resistance, heat dissipation capacity, and operational safety of the source under high pressure and high laser power conditions. An ellipsoidal reflector is positioned within a sealed cavity, with its first focal point aligned with the plasma generation region. This allows for direct collection and focusing of plasma light within the cavity, reducing the complexity of external collection optical systems. Optical components focus the pump laser directly or after reflection by the ellipsoidal reflector to the first focal point, matching the pump laser's focusing position with the plasma light collection focal point, thus improving plasma excitation and light collection efficiency. A reflecting element refracts the plasma light collected by the ellipsoidal reflector to the output window, focusing the output light at the equivalent position of the second focal point. This achieves compact refracted output while maintaining the dual-focal collection relationship of the ellipsoidal reflector, facilitating connection with subsequent illumination, detection, or fiber optic coupling systems. Therefore, this invention enables integrated arrangement of pump laser input, plasma generation, plasma light collection, and refracted output within a sealed cavity, improving the light source's structural compactness, output brightness, and output stability. Attached Figure Description

[0036] Figure 1 A schematic diagram of the structure of a laser plasma source according to an embodiment of this application is shown. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0038] It should be noted that, in this application, "pump laser" refers to a laser used to break down and / or maintain the formation of plasma from the working gas; "plasma light" refers to target radiation emitted from the plasma generation region, which includes at least ultraviolet light, and may also include radiation in the visible, deep ultraviolet, or vacuum ultraviolet bands. "First focal point" refers to one focal point of the ellipsoidal reflector and corresponds to the plasma generation region; "second focal point" refers to the other focal point of the ellipsoidal reflector. When the light path corresponding to the second focal point is deflected by the reflecting element, the second focal point forms a corresponding equivalent position on the deflected light path, and this position is... Figure 1 The center can be represented by the equivalent focal point 108.

[0039] Embodiments of this application disclose a laser plasma source. (Reference) Figure 1 The light source includes a housing 101, an ellipsoidal reflector 102, an optical assembly 104, and a reflective element 105. In some embodiments, the light source may also include an optical fiber 103, a gas conditioning system, a control system, and a cooling structure.

[0040] The housing 101 serves as the main pressure-bearing component for containing the working gas, and its interior forms a sealed cavity for containing the working gas. According to the laser plasma light source of the present invention, the housing 101 is made of metal or ceramic material. Compared with the conventional structure that uses a quartz glass bulb to contain high-pressure gas, the housing 101 made of metal or ceramic material has higher pressure-bearing capacity and thermal conductivity, making it more suitable for operation under high-pressure and high-power pump laser conditions. It also facilitates the dissipation of heat generated by plasma thermal radiation, pump laser stray light, and absorption by internal optical components, thereby improving the safety and thermal stability of the light source operation.

[0041] The housing 101 is provided with a light input section and an output window 107. The light input section is used to introduce an external pump laser into the sealed cavity. As an example, the light input section may include a sealed fiber optic connector that is hermetically connected to the housing 101, and the pump laser enters the optical assembly 104 after being input through fiber optic cable 103. As another example, the light input section may also be an optical window through which the pump laser passes, and the optical window is hermetically connected to the housing 101. The output window 107 is used to output the collected and deflected plasma light to the outside of the housing 101. The output window 107 is preferably hermetically connected to the housing 101 to maintain the pressure stability of the working gas inside the sealed cavity.

[0042] An ellipsoidal reflector 102 is disposed within a sealed cavity and has a first focal point 106 and a second focal point. The first focal point 106 is located within the sealed cavity, and the region where the first focal point 106 is located constitutes the plasma generation region. The reflective surface of the ellipsoidal reflector 102 is used to collect plasma light emitted from the plasma near the first focal point 106 and to converge the plasma light toward the second focal point or its equivalent refraction position. The ellipsoidal reflector 102 can be installed as a freestanding reflector within the housing 101, or it can be fixed to an internal mounting structure of the housing 101 via a mirror mount. Preferably, the reflective surface of the ellipsoidal reflector 102 has a high reflectivity for the target plasma light wavelength band to improve the plasma light collection efficiency.

[0043] Optical component 104 is disposed in the propagation path of the pump laser and is used to shape the pump laser input from the light input unit. The shaping may include one or more of collimation, beam expansion, reflection, focusing, aberration compensation, or spot morphology adjustment. The pump laser processed by optical component 104 can be directly focused to the vicinity of the first focal point 106, or it can be focused to the vicinity of the first focal point 106 after reflection by ellipsoidal mirror 102. The high-power pump laser breaks down and sustains the working gas at the first focal point 106 or its predetermined neighborhood, causing the working gas to form laser plasma. This plasma generates broadband radiation, which, after being collected by ellipsoidal mirror 102, forms a high-brightness light output that can be used in subsequent illumination systems, detection systems, fiber optic coupling systems, or monochromators.

[0044] A reflective element 105 is disposed within the sealed cavity and positioned along the propagation path of the plasma light emitted from the plasma at the first focal point 106 and reflected by the ellipsoidal mirror 102. The reflective element 105 deflects the plasma light toward the exit window 107. The plasma light, deflected by the reflective element 105, passes through the exit window 107 and converges at the equivalent focal point 108. The equivalent focal point 108 corresponds to the equivalent position of the second focal point of the ellipsoidal mirror 102 after deflection by the reflective element 105. Thus, the ellipsoidal mirror 102 and the reflective element 105 together form the plasma light collection and deflection output optical path within the cavity.

[0045] In the above structure, the housing 101 provides a sealed and pressurized gas working space; the ellipsoidal reflector 102 utilizes its bifocal optical properties to collect plasma light at the first focal point 106 and converge it towards the second focal point or the equivalent focal point 108; the reflective element 105 deflects the plasma light to the output window 107, so that the output light path does not have to be completely aligned with the original second focal direction of the ellipsoidal reflector 102, thereby facilitating the arrangement of the light input, light collection, and light output structures within a limited cavity space. With this structure, a high-brightness, high-stability cavity laser plasma source can be achieved without using a traditional glass bulb as an independent gas container.

[0046] In one exemplary embodiment, the reflecting element 105 is a dichroic mirror. This dichroic mirror has high transmittance for the pump laser and high reflectivity for the target plasma light band. In this case, the optical assembly 104 may include a collimation system and / or a beam expander system for processing the pump laser input from the light input unit into a beam suitable for incident on the ellipsoidal reflector 102. The pump laser, processed by the optical assembly 104, passes through the reflecting element 105 and is incident on the ellipsoidal reflector 102, and after reflection by the ellipsoidal reflector 102, it converges to the first focal point 106. That is, for the ellipsoidal reflector 102, the equivalent source point of the pump laser can be located at the second focal point or the equivalent position of the second focal point, so that after reflection by the ellipsoidal reflector 102, the pump laser converges to the first focal point 106 according to the ellipsoidal bifocal imaging relationship.

[0047] In this embodiment, the plasma light generated at the first focal point 106 diverges into the surrounding space, with the portion incident on the ellipsoidal reflector 102 being collected by the ellipsoidal reflector 102 and propagating towards the second focal point. When the plasma light propagates to the reflective element 105, since the reflective element 105 has a reflective effect on the target plasma light band, the plasma light is deflected by the reflective element 105 and output towards the exit window 107. In this way, the pump laser can pass through the reflective element 105 into the reflected optical path of the ellipsoidal reflector 102, while the plasma light can be reflected and output by the reflective element 105. The pump laser input optical path and the plasma light output optical path are separated within the same compact cavity, reducing optical path crossings and structural obstructions, which is beneficial to improving system integration and output light stability.

[0048] In another exemplary embodiment, the optical component 104 can constitute a focusing system. After the pump laser enters through the light input section, it is directly focused by the optical component 104 to the first focal point 106 or its predetermined neighborhood. In this case, the ellipsoidal reflector 102 is mainly used to collect the plasma light generated at the first focal point 106 and focus the plasma light towards the second focal point or the deflected equivalent focal point 108. This method is suitable for structural arrangements where the pump laser incident path and the plasma light collection path are relatively independent. Both the direct focusing method and the focusing method via reflection by the ellipsoidal reflector 102 can be selected according to the internal space of the housing 101, the position of the exit window 107, the pump laser input direction, and the position of the interface of the subsequent system.

[0049] In some embodiments, the laser plasma source further includes a plasma triggering unit. The plasma triggering unit is used to pre-ionize or break down the working gas within the sealed cavity during the source startup phase to form an initial plasma. Subsequently, the pump laser inputs energy to the initial plasma and sustains it. The plasma triggering unit can be an electrode triggering unit or an electrodeless triggering unit. When an electrode triggering unit is used, it includes at least one pair of trigger electrodes disposed within or communicating with the sealed cavity. During the startup phase, the trigger electrodes receive a trigger voltage to break down the working gas; after the plasma enters the laser sustaining state, the trigger electrodes stop applying the trigger voltage. The trigger electrodes can be disposed near the first focal point 106 or within a gas region communicating with the first focal point 106, as long as the initial plasma generated can be captured and sustained by the pump laser.

[0050] In other embodiments, the plasma triggering unit is an electrodeless triggering unit, where no electrodes for triggering discharge are provided in the sealed cavity or lamp chamber. The electrodeless triggering unit may include a starting laser source and / or an electromagnetic wave generator. The starting laser source is used to input a high peak power or high power density starting laser to the first focal point 106 or its adjacent area, causing optical breakdown of the working gas and forming initial plasma; the pump laser may be a different timing output from the same laser source as the starting laser, or it may be provided by a sustaining laser source independent of the starting laser source. The electromagnetic wave generator may be a microwave generator, a radio frequency generator, or other electromagnetic wave excitation device, which couples electromagnetic wave energy into the sealed cavity or lamp chamber through a coupling window, antenna, resonant cavity, or waveguide structure to form initial plasma in the working gas. Using an electrodeless triggering method avoids the impact of electrode material evaporation, sputtering, or ablation on the working gas and emission spectrum, and is beneficial for improving the stability and lifespan of the light source.

[0051] In some embodiments, the container for holding the working gas can be a quartz container, which constitutes a lamp chamber or bulb. The quartz container can be made of ultraviolet-grade fused silica or other quartz materials suitable for transmitting light of the target wavelength and is hermetically connected to the light input section, output window, or external sealing structure. Unlike conventional short-arc bulbs, this quartz container does not have electrodes inside for triggering or maintaining the discharge. The working gas is activated by a high-power-density laser or electromagnetic wave excitation, and the plasma is maintained by a pump laser. Therefore, although this quartz container can be called a bulb, it does not rely on internal electrodes to generate an arc discharge; instead, it is used as a working gas container for an electrodeless laser plasma light source.

[0052] In some embodiments, the laser plasma source further includes a control system and an adjustable mounting base. At least one of the optical component 104, the reflective element 105, and the ellipsoidal reflector 102 is mounted on the adjustable mounting base. The adjustable mounting base is used to adjust the position and / or angle of the corresponding optical component. The control system can determine the offset of the pump laser's focusing position relative to the first focal point 106 based on gas state data and / or temperature data within the sealed cavity, and drive the adjustable mounting base to adjust its position or angle according to this offset.

[0053] Specifically, when the working gas pressure, gas composition, or temperature within the sealed cavity changes, the refractive index distribution of the working gas may change accordingly, potentially causing focus drift when the pump laser propagates within the sealed cavity. Simultaneously, plasma thermal radiation and gas thermal convection within the cavity may also introduce thermal lensing effects or aberrations, causing the actual focusing position of the pump laser to deviate from the first focus 106. The control system can establish or invoke preset compensation relationships based on gas pressure, gas composition, and temperature data to calculate the offset of the pump laser focus relative to the first focus 106, and drive at least one of the optical components 104, the reflecting element 105, or the ellipsoidal mirror 102 to adjust, ensuring that the actual focusing position of the pump laser coincides with or is located within a predetermined neighborhood of the first focus 106.

[0054] By employing the aforementioned control method, even if the gas pressure or composition of the light source is dynamically adjusted during operation, the pump laser focus drift caused by changes in gas refractive index, thermal lensing effect, or thermal convection can be reduced, thereby keeping the plasma generation region near the first focus 106 of the ellipsoidal reflector 102. Since the plasma light collection efficiency is closely related to the position of the plasma generation region relative to the first focus 106, this control method can improve the stability of the plasma light output intensity and enhance the coupling efficiency of the subsequent optical system.

[0055] In a further embodiment, the ellipsoidal mirror 102 is mounted on a mount that is displaceable along its optical axis. The optical axis can be understood as the axial direction of the two focal points of the ellipsoidal mirror 102, or the principal axis direction of the ellipsoidal mirror 102 in its optical design. The control system drives the mount to displace along the optical axis according to the offset, so that the focusing position of the pump laser coincides with or is located within a predetermined neighborhood of the first focal point 106. This mount allows for minute displacement adjustments to compensate for focus drift caused by changes in the gas state. If necessary, the control system can also synchronously adjust the position or angle of the optical component 104 to further correct the incident direction, convergence angle, or spot position of the pump laser.

[0056] By employing a compensation method based on the displacement of the ellipsoidal reflector 102 along the optical axis, feedforward or closed-loop compensation can be performed on the pump laser focusing state near the first focal point 106 without significantly altering the overall cavity structure. For scenarios requiring different gas pressures or different gas mixture ratios during startup and stable operation, this method can reduce the impact of dynamic gas adjustment on pump laser focusing and plasma light output coupling efficiency.

[0057] In some embodiments, the laser plasma source further includes a gas regulation system. The gas regulation system includes a gas mixing chamber 109, an inlet pipe 110, an inlet valve 111, a vent pipe 112, a vent valve 113, and a pressure gauge 114. The gas mixing chamber 109 is used to contain one working gas or to mix multiple working gases in a set ratio. The working gas can be one or more of xenon, argon, krypton, neon, and helium. The gas mixing chamber 109 is connected to the sealed cavity of the housing 101 via the inlet pipe 110. The inlet pipe 110 is equipped with an inlet valve 111, which controls the entry of the working gas or mixed working gas into the sealed cavity. The vent pipe 112 is connected to the sealed cavity, and the vent pipe 112 is equipped with a vent valve 113, which discharges gas from the sealed cavity or regulates the gas pressure within the sealed cavity. The barometer 114 is installed on the vent pipe 112 or on the housing 101 and is used to detect the gas pressure inside the sealed cavity.

[0058] In actual operation, a predetermined proportion of working gas can be prepared first by the gas mixing chamber 109, and then the inlet valve 111 can be opened to allow the working gas to enter the sealed cavity of the housing 101 through the inlet pipe 110. The barometer 114 monitors the pressure inside the sealed cavity in real time. When the pressure reaches the set value, the inlet valve 111 closes or enters the adjustment state, and the pump laser enters the sealed cavity through the light input section and optical components 104, and breaks down and maintains the working gas to form plasma near the first focal point 106. If it is necessary to reduce the pressure or replace part of the gas during operation, the vent valve 113 can be opened to allow the gas inside the sealed cavity to be discharged through the vent pipe 112. By controlling the inlet valve 111 and the vent valve 113, the gas pressure inside the sealed cavity can be dynamically adjusted.

[0059] The gas conditioning system can also employ different gas states depending on the operating stage. For example, during the light source startup stage, a more easily broken-down gas pressure or mixing ratio can be used to reduce the difficulty of the pump laser breaking down the working gas; during the plasma stable operation stage, the pressure or component ratio can be switched to a level more suitable for high-brightness plasma light output to improve output brightness and stability. Because the housing 101 has good pressure-bearing and heat dissipation capabilities, the aforementioned dynamic gas conditioning can be achieved within a sealed cavity without requiring the replacement of an independent glass bulb to change the gas state.

[0060] In some embodiments, the laser plasma source further includes a magnetic confinement device. This magnetic confinement device can be disposed on the outside of the housing 101, within the wall of the housing 101, or within a sealed cavity, and is used to generate a magnetic field near the first focal point 106. The magnetic field at least covers the plasma generation region where the first focal point 106 is located, to confine charged particles in the plasma, keeping the plasma within a predetermined neighborhood of the first focal point 106. The magnetic confinement device may include a permanent magnet, an electromagnetic coil, a magnetic yoke, or a combination thereof; when the magnetic confinement device includes an electromagnetic coil, the control system can adjust the energizing parameters of the electromagnetic coil to change the magnetic field strength or magnetic field distribution near the first focal point 106.

[0061] In some embodiments, the outlet end of the inlet pipe 110 is positioned towards the reflective element 105 or its adjacent region, so that the working gas entering the sealed cavity through the inlet pipe 110 forms an airflow flowing over the surface or back side of the reflective element 105. This airflow is used to remove the heat generated by the reflective element 105 after absorbing the pump laser or its stray light or plasma light, and can also purge the surface of the reflective element 105 to reduce heat accumulation or contaminant deposition. The outlet end of the inlet pipe 110 can be configured as a nozzle, an angled opening, or an annular outlet structure, so that the working gas flows through the reflective element 105 in a predetermined direction and then enters the main space of the sealed cavity.

[0062] In some embodiments, the laser plasma source further includes a control system. The control system is electrically connected to the gas mixing chamber 109, the inlet valve 111, the vent valve 113, and the barometer 114. The control system controls the inlet valve 111 and the vent valve 113 based on pressure data fed back from the barometer 114, and controls the gas distribution state of the gas mixing chamber 109 based on gas composition setting data. Specifically, when the barometer 114 detects that the pressure inside the sealed chamber is lower than a set range, the control system can control the inlet valve 111 to open or increase its opening, allowing the working gas in the gas mixing chamber 109 to replenish the sealed chamber; when the barometer 114 detects that the pressure inside the sealed chamber is higher than a set range, the control system can control the vent valve 113 to open or increase its opening, allowing some gas to be discharged; when the pressure is within the set range, the control system can maintain the valve state or make small adjustments to maintain pressure stability.

[0063] The control system can also implement overpressure protection based on the detection results of the barometer 114. When the pressure inside the sealed cavity exceeds the safety threshold, the control system can control the pump laser to reduce power or stop output, and control the vent valve 113 to perform a pressure relief action to improve the safety of the light source operation. The control system can also use gas pressure data, gas composition data, and temperature data as input parameters for optical compensation to calculate the pump laser focus drift and drive the adjustable mounting base to adjust the optical components 104, reflective elements 105, or ellipsoidal reflectors 102, thereby achieving coordinated control of gas regulation and optical regulation.

[0064] In some embodiments, the housing 101 is provided with a cooling channel or a cooling jacket. The cooling channel or cooling jacket may be arranged inside or around the wall of the housing 101 to allow a cooling medium to flow through the housing 101 to remove the heat generated during plasma operation. At least one of the ellipsoidal reflector 102, the reflective element 105, and the optical assembly 104 may be provided with a heat-conducting base or a water-cooling structure. The heat-conducting base is used to conduct the heat absorbed by the corresponding optical element to the housing 101 or an external heat dissipation structure; the water-cooling structure is used to directly remove the heat from the corresponding optical element through a circulating cooling medium.

[0065] The aforementioned cooling structure reduces the temperature rise of the housing 101 and internal optical components under high-power operation, thereby minimizing thermal deformation and drift. For the ellipsoidal mirror 102, reduced thermal deformation helps maintain its focal position and collection efficiency; for the reflective element 105, reduced temperature rise helps maintain its transmission and reflection spectral characteristics and surface shape; and for the optical assembly 104, reduced temperature rise helps reduce pump laser shaping and focusing errors. Therefore, the cooling structure improves the output stability of the light source during long-term operation.

[0066] In some embodiments, the optical component 104 includes one or more of a collimating lens, a beam expander assembly, a focusing lens, a reflecting mirror, an aspherical lens, or a beam shaping element. The collimating lens can be used to collimate the diverging laser beam output from the fiber optic cable 103 or other optical input unit into approximately parallel light; the beam expander assembly can be used to increase the diameter of the pump laser beam to adjust the beam aperture of the incident ellipsoidal reflecting mirror 102 or the focusing system; the focusing mirror can be used to directly focus the pump laser to the vicinity of the first focal point 106; the reflecting mirror can be used to change the propagation direction of the pump laser to adapt to the internal spatial layout of the housing 101; the aspherical lens or beam shaping element can be used to correct aberrations, improve spot quality, or adjust the energy distribution of the pump laser in the plasma generation region. These components can be used individually or in combination.

[0067] In some embodiments, the exit window 107 is made of calcium fluoride, magnesium fluoride, sapphire, or ultraviolet-grade fused silica. These materials have good transmittance for ultraviolet light or related target wavelengths, reducing absorption loss when plasma light exits the sealed cavity. The material of the exit window 107 can be selected according to the target output wavelength; for example, when the target output wavelength includes deep ultraviolet or vacuum ultraviolet wavelengths, a window material with high transmittance for the corresponding wavelength can be preferentially selected. The exit window 107 maintains an airtight connection with the housing 101 to ensure pressure stability within the sealed cavity.

[0068] The operation of this embodiment is described below with reference to a specific working process. First, the control system controls the gas mixing chamber 109 to configure the working gas according to preset gas component parameters, and fills the sealed cavity inside the housing 101 with the working gas through the inlet pipe 110 and the inlet valve 111. The barometer 114 detects the pressure inside the sealed cavity in real time and feeds the pressure data back to the control system. When the pressure reaches the set range, the pump laser is input through the optical fiber 103 or other optical input unit, and is collimated, expanded, shaped and / or focused by the optical component 104. The pump laser can be directly focused to the first focal point 106, or it can be incident on the ellipsoidal reflector 102 after passing through the reflective element 105, which acts as a dichroic mirror, and then focused to the first focal point 106 after reflection by the ellipsoidal reflector 102. The pump laser breaks down and maintains the working gas to form plasma near the first focal point 106. The plasma light emitted by the plasma is collected by the ellipsoidal reflector 102, refracted by the reflective element 105, and output through the exit window 107, forming a high-brightness light output near the refracted equivalent focal point 108.

[0069] During operation, if the control system detects changes in gas pressure, gas composition, or temperature that may cause a shift in the pump laser's focusing position, the control system determines the focus shift amount based on a preset algorithm or calibration data, and drives the adjustable mounting base to adjust the position or angle of the optical component 104, the reflective element 105, or the ellipsoidal mirror 102. Specifically, when the ellipsoidal mirror 102 is mounted on a mirror mount that can be displaced along the optical axis, the control system can drive the mirror mount to make a small displacement along the optical axis, so that the actual focusing position of the pump laser returns to the first focus 106 or its predetermined neighborhood. Simultaneously, the control system can adjust the inlet valve 111 and the outlet valve 113 based on feedback from the barometer 114 to maintain the pressure within the sealed cavity within a set range, and adjust the gas distribution state of the gas mixing chamber 109 as needed.

[0070] In one optional driving implementation, the laser plasma source employs a low-pressure electrodeless start-up and boosted laser sustaining driving method. Specifically, during the start-up phase, the control system first controls the gas conditioning system to bring the working gas within the sealed cavity into a first pressure range, which is lower than the working gas pressure during the stable output phase of the light source, thereby reducing the breakdown threshold of the working gas. Subsequently, the control system activates the electromagnetic wave generator, causing electromagnetic wave energy to be coupled into the sealed cavity through a coupling window, antenna, waveguide structure, or resonant cavity structure, forming a microwave electromagnetic field at or near the first focal point 106, thereby exciting the working gas and forming initial plasma under electrodeless conditions.

[0071] Upon detecting the initial plasma formation, the control system activates the pump laser or increases its power, causing the pump laser to converge at the first focal point 106 or its vicinity after being directly reflected by the optical component 104 or reflected by the ellipsoidal mirror 102. Laser energy is then coupled to the initial plasma to maintain and enhance it. The formation state of the initial plasma can be determined based on one or more of the following: plasma light intensity, spectral signal, pressure change within the cavity, electromagnetic wave reflection power change, or pump laser absorption state.

[0072] After the pump laser can stably maintain the plasma, the control system controls the inlet valve 111 and the outlet valve 113 according to a predetermined pressure rise curve, so that the working gas pressure in the sealed cavity gradually increases from the first pressure range to the second pressure range. Simultaneously, the control system synchronously or in stages increases the pump laser power, keeping the plasma at the first focal point 106 or its predetermined neighborhood during the pressure rise process, and gradually increasing the plasma density, temperature, and radiance. The second pressure range corresponds to the working gas pressure during the high-brightness stable output stage.

[0073] When the working gas pressure within the sealed cavity reaches the second pressure range, and the plasma light intensity, spectral distribution, or output stability meets predetermined conditions, the control system initiates the stable operation phase of the light source. During this stable operation phase, the control system can stop or reduce the output of the electromagnetic wave generator, maintaining the plasma solely through the pump laser; alternatively, it can maintain the electromagnetic wave generator at low power or intermittently to assist in stabilizing the plasma position or improving energy coupling efficiency. Thus, the light source can transition from a low-pressure, easily start-up state to a high-pressure, high-brightness, stable light-emitting state without the need for internal discharge electrodes or direct breakdown of the high-pressure working gas by a high-power laser.

[0074] Through the above embodiments, this application utilizes the housing 101 instead of the traditional glass bulb as a sealed pressure-bearing container for the working gas, thereby improving pressure resistance and heat dissipation; it utilizes the ellipsoidal reflector 102 to focus the pump laser to the first focal point 106 or collect the plasma light at the first focal point 106, thereby improving the efficiency of plasma generation and plasma light collection; it utilizes the reflective element 105 to realize the refracted output of the plasma light, making the light source structure more compact; it utilizes the gas mixing chamber 109, the inlet pipe 110, the inlet pipe valve 111, the vent pipe 112, the vent pipe valve 113, and the barometer 114 to realize the dynamic adjustment of the working gas pressure and composition; and it utilizes the control system and the adjustable mounting base to compensate for the focal point drift caused by changes in the gas state, thereby improving the stability of the light source output intensity, output position, and output coupling efficiency.

[0075] The above description is merely an exemplary embodiment of this application and is not intended to limit this application. For those skilled in the art, equivalent substitutions or combinations can be made to the structure, connection relationship, optical path form, gas type, window material, and control method in the above embodiments without departing from the concept of this application, and such substitutions or adjustments should all fall within the protection scope of this application.

[0076] It is understood that the specific embodiments described herein are merely for illustrative purposes and not for limiting the scope of this application. Furthermore, for ease of description, the accompanying drawings show only the parts relevant to this application, and not all of the structures or processes. It should be noted that similar reference numerals and letters in the drawings denote similar items throughout this application.

[0077] It should be understood that although the terms "first," "second," etc., may be used herein to describe various features, these features should not be limited by these terms. The use of these terms is merely for distinction and should not be construed as indicating or implying relative importance. For example, without departing from the scope of the exemplary embodiments, a first feature may be referred to as a second feature, and similarly, a second feature may be referred to as a first feature.

[0078] In the description of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment based on the specific circumstances.

[0079] The illustrative embodiments of this application include, but are not limited to, laser plasma light sources.

[0080] Various aspects of the illustrative embodiments will be described using terminology commonly employed by those skilled in the art to convey the essence of their work to others skilled in the art. However, it will be apparent to those skilled in the art that some alternative embodiments will be practiced using the features partially described. Specific figures and configurations are set forth for purposes of explanation in order to provide a more thorough understanding of the illustrative embodiments. However, it will be apparent to those skilled in the art that alternative embodiments may be practiced without specific details. In some other instances, well-known features have been omitted or simplified herein to avoid obscuring the illustrative embodiments of this application.

[0081] References to "an embodiment," "embodiment," "illustrative embodiment," etc., in this application indicate that the described embodiment may include specific features, structures, or properties; however, each embodiment may or may not necessarily include specific features, structures, or properties. Furthermore, these phrases are not necessarily directed at the same embodiment. Moreover, when specific features are described in conjunction with specific embodiments, the knowledge of those skilled in the art can influence the combination of these features with other embodiments, whether or not those embodiments are explicitly described.

[0082] Unless the context otherwise specifies, the terms “comprising,” “having,” and “including” are synonyms. The phrase “A and / or B” means “(A), (B), or (A and B).”

[0083] In the accompanying drawings, some structures may be shown in a specific arrangement and / or order. However, it should be understood that such a specific arrangement and / or order is not necessary. Rather, in some embodiments, these features may be illustrated in a manner and / or order different from that shown in the illustrative drawings. Furthermore, the structures included in a particular drawing do not mean that all embodiments need to include such features; in some embodiments, these features may not be included or may be combined with other features.

[0084] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, the use of the technical solutions of this application is not limited to the various applications mentioned in the embodiments of this application. Various structures and modifications can be easily implemented with reference to the technical solutions of this application to achieve the various beneficial effects mentioned herein. Within the scope of knowledge possessed by those skilled in the art, all changes made without departing from the spirit of this application should be considered within the scope of this patent application.

Claims

1. A laser plasma light source, characterized in that, include: The housing (101) has a sealed cavity inside for containing working gas, and the housing (101) is provided with a light input section and an output window (107). An ellipsoidal reflector (102) is disposed in the sealed cavity. The ellipsoidal reflector (102) has a first focal point (106) and a second focal point. The first focal point (106) is located in the sealed cavity, and the area where the first focal point (106) is located constitutes a plasma generation area. An optical component (104) is disposed in the propagation path of the pump laser and is used to shape the pump laser input by the light input unit, so that the pump laser is focused to the first focal point (106) directly or after being reflected by the ellipsoidal mirror (102); and A reflective element (105) is disposed in the sealed cavity and located on the propagation path of the plasma light emitted from the plasma at the first focal point (106) and reflected by the ellipsoidal reflector (102). The plasma light after being refracted by the reflective element (105) converges at the refracted equivalent focal point (108) through the exit window (107). The refracted equivalent focal point (108) corresponds to the equivalent position of the second focal point after being refracted by the reflective element (105).

2. The laser plasma source according to claim 1, characterized in that: The reflective element (105) is a dichroic mirror, which transmits the pump laser and reflects the plasma light. The optical component (104) includes a collimation system and / or a beam expander system for positioning the pump laser, after passing through the reflective element (105), at the equivalent source point of the ellipsoidal mirror (102) relative to the second focal point or the equivalent position of the second focal point. The pump laser passes through the reflective element (105) and is incident on the ellipsoidal reflector (102), and is reflected by the ellipsoidal reflector (102) and converged to the first focal point (106). The plasma light generated at the first focal point (106) is collected by the ellipsoidal reflector (102) and then reflected by the reflective element (105) toward the exit window (107).

3. The laser plasma light source according to claim 1, characterized in that, It also includes a control system and an adjustable mounting base: At least one of the optical component (104), the reflective element (105), and the ellipsoidal reflector (102) is mounted on the adjustable mounting base; The control system determines the offset of the focusing position of the pump laser relative to the first focal point (106) based on the gas state data and / or temperature data in the sealed cavity, and drives the adjustable mounting base to adjust the position or angle according to the offset.

4. The laser plasma source according to claim 3, characterized in that: The ellipsoidal mirror (102) is mounted on a mount that is movable along its optical axis; The control system drives the mirror mount to move along the optical axis according to the offset, so that the focusing position of the pump laser coincides with the first focal point (106) or is located in a predetermined neighborhood of the first focal point (106).

5. The laser plasma light source according to claim 1, characterized in that, It also includes a gas conditioning system, which comprises: Gas mixing chamber (109) is used to contain one working gas or to mix multiple working gases in a set ratio; An air inlet pipe (110) connects the gas mixing chamber (109) and the sealed chamber, and an air inlet valve (111) is provided on the air inlet pipe (110). A vent pipe (112) is connected to the sealed cavity, and a vent pipe valve (113) is provided on the vent pipe (112); and A barometer (114) is installed on the vent pipe (112) or the sealed cavity to detect the gas pressure inside the sealed cavity.

6. The laser plasma source according to claim 5, characterized in that, It also includes the control system: The control system is electrically connected to the gas mixing chamber (109), the inlet valve (111), the outlet valve (113), and the barometer (114), respectively. The control system controls the inlet valve (111) and the outlet valve (113) based on the pressure data fed back by the barometer (114), and controls the gas distribution state of the gas mixing chamber (109) based on the gas composition setting data.

7. The laser plasma source according to claim 1, characterized in that: The housing (101) is provided with cooling channels or cooling jackets; and / or, At least one of the ellipsoidal reflector (102), the reflective element (105), and the optical assembly (104) is provided with a heat-conducting base or a water-cooling structure.

8. The laser plasma source according to claim 1, characterized in that: The optical component (104) includes one or more of a collimating lens, a beam expander group, a focusing lens, a reflecting mirror, an aspherical lens, or a beam shaping element.

9. The laser plasma source according to claim 1, characterized in that: The exit window (107) is made of calcium fluoride, magnesium fluoride, sapphire, or ultraviolet-grade fused silica; and The working gas is one or more of the following: xenon, argon, krypton, neon, and helium.

10. The laser plasma source according to any one of claims 1-9, characterized in that: The housing (101) is made of metal, ceramic or quartz.

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