Laser amplifier capable of detecting damage of output mirror

Abstract

The invention discloses a laser amplifier capable of detecting the damage of an output mirror, which comprises a seed light source, a fixing structure and an output mirror, the detection mechanism is arranged in the fixing structure and comprises an infrared signal generator and an infrared detector; the infrared detector judges whether the output mirror is damaged or not by receiving an infrared signal which is reflected by the output mirror and emitted by the infrared signal generator; and the signal controller is connected with the red detection mechanism and the seed light source and provides control signals for the detection mechanism and the seed light source. According to the laser amplifier, the detection mechanism is arranged in the fixing structure, and the detector receives the reflected infrared signal, so that the damage condition of the output mirror is detected in real time in the working process of the laser amplifier. Moreover, when the occurrence of damage is detected, the operation of the laser amplifier is timely and actively stopped.

Description

Technical Field

[0001] The invention relates to the technical field of carbon dioxide lasers, and in particular to a laser amplifier capable of detecting damage to an output mirror. Background Art

[0002] The 10,000-watt CO2 laser is an important component of the EUV lithography light source. The double-sided anti-reflection film-coated zinc selenide (ZnSe) lens has a transmittance of more than 99% for 10.6μm CO2 lasers, and is currently the first choice for CO2 laser output mirrors. When the CO2 laser is operated at high power for a long time, once the zinc selenide lens is damaged, it will directly affect the output power of the laser, thereby affecting the output power of the EUV light source, reducing the processing efficiency of the EUV lithography machine, and causing significant economic losses.

[0003] Thermal damage is the main cause of zinc selenide lens damage. Under the irradiation of a 10,000-watt carbon dioxide laser, the temperature of the lens film and base material rises sharply. When the temperature gradient distribution is too high or the thermal stress is too concentrated, it will cause bad spots, defects, ablation, cracking and other damage to the film and base material of the zinc selenide lens.

[0004] Thermocouples and thermal imagers are currently effective means of directly monitoring device temperature. The former can only contact the non-irradiated area of ​​the lens, so it is impossible to measure the temperature change of the lens at the center of laser irradiation; the latter is a non-contact measurement, but the high transmittance of the lens itself can easily introduce ambient temperature errors, and it requires sufficient shielding of stray light, otherwise it is easy to cause damage to the thermal imager, and the cost is relatively high. Summary of the invention

[0005] The purpose of the present invention is to provide a laser that can detect window mirror damage, which can solve at least one of the above-mentioned technical problems. The specific solution is as follows:

[0006] According to a specific embodiment disclosed in the present invention, the present invention discloses a laser amplifier capable of detecting output mirror damage, comprising: a seed light source,

[0007] A fixed structure, in which an output mirror is arranged;

[0008] The detection mechanism is arranged in the fixed structure, and includes: an infrared signal generator and an infrared detector; the infrared detector determines whether the output mirror is damaged by receiving the infrared signal reflected by the output mirror and emitted by the infrared signal generator;

[0009] A signal controller is connected to the red detection mechanism and the seed light source, and provides control signals for the detection mechanism and the seed light source.

[0010] Preferably, a detection chamber is provided in the fixed structure for accommodating the detection mechanism, so that the infrared signal emitted by the infrared signal generator is reflected by the output mirror and then received by the infrared detector.

[0011] Preferably, it also includes:

[0012] A first water cooling circuit is arranged in the seed light source;

[0013] a second water cooling circuit, disposed in the fixed structure;

[0014] The first water cooling circuit is connected to the second water cooling circuit, so that the temperature of the detection chamber is within the operating temperature range of the detection mechanism.

[0015] Preferably, the signal controller is connected to the infrared signal generator via a signal trigger circuit; connected to the infrared detector via a signal receiving circuit; and connected to the seed light source via a command control circuit;

[0016] When the infrared detector detects an abnormal electrical signal, the signal controller stops sending a trigger signal to the infrared signal generator and sends a stop instruction to the seed light source at the same time.

[0017] Preferably, the seed light source is a carbon dioxide laser.

[0018] Preferably, the laser output power outputted through the output mirror is in the order of 10,000 watts.

[0019] Preferably, the material of the output mirror is: ZnSe, GeAs, ZnS or diamond.

[0020] Preferably, the wavelength range of the infrared signal emitted by the infrared signal generator is: 750nm-900nm.

[0021] Preferably, the power range of the infrared signal generator is: 5mW-15mW.

[0022] Preferably, the output mirror fixing structure is made of metal.

[0023] Compared with the prior art, the above solution of the embodiment disclosed in the present invention has at least the following beneficial effects:

[0024] The present invention arranges an infrared signal generator and an infrared detector in a fixed structure of a fixed output mirror of a laser amplifier, and the detector receives reflected infrared signals to monitor the damage of the window mirror in real time during the operation of the laser. Moreover, when damage is detected, the operation of the laser amplifier can be stopped in time and actively. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the disclosure of the present invention, and together with the specification, are used to explain the principles disclosed in the present invention. Obviously, the drawings described below are only some embodiments disclosed in the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0026] Figure 1 A schematic diagram of the overall structure of a laser amplifier capable of detecting output mirror damage provided by an embodiment of the present invention.

[0027] Reference numerals:

[0028] 10: Seed light source;

[0029] 11: fixed structure; 111: output mirror; 112: water inlet; 113: water outlet;

[0030] 12: infrared signal generator; 13: infrared detector;

[0031] 14: signal controller; 141: signal trigger circuit; 142: signal receiving circuit; 143: command control circuit. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages disclosed in the present invention clearer, a laser amplifier capable of detecting output mirror damage disclosed in the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments disclosed in the present invention, rather than all the embodiments. Based on the embodiments disclosed in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection disclosed in the present invention.

[0033] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0034] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0035] It should be understood that although the terms first, second, third, etc. may be used to describe in the embodiments of the present application, these should not be limited to these terms. These terms are only used to distinguish. For example, without departing from the scope of the embodiments of the present application, the first may also be referred to as the second, and similarly, the second may also be referred to as the first.

[0036] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such product or device. In the absence of more restrictions, the elements defined by the sentence "comprises a" do not exclude the presence of other identical elements in the product or device including the elements.

[0037] The optional embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0038] The non-direct contact detection of damage to the anti-reflection film-coated lens can be achieved based on the changes in its optical properties (such as transmittance, reflectivity, scattering characteristics, etc.), that is, after the lens is damaged (such as scratches, cracks, pollution, etc.), its surface reflectivity will change. By measuring the intensity or distribution of the reflected light, it can be determined whether the lens is damaged. The above methods can detect the damage of the lens in real time, but they all require the lens to be tested to be placed in the corresponding detection device for detection separately. For lenses that are in operation, such as the output mirror in a working laser amplifier, the collimating mirror of the laser, etc., real-time detection cannot be performed.

[0039] Therefore, the present invention provides a laser amplifier capable of detecting output mirror damage, which can monitor whether the output mirror is damaged in real time during the operation of the laser. Figure 1 As shown, including:

[0040] Seed light source 10,

[0041] A fixing structure 11, used for fixing an output mirror 111;

[0042] The detection mechanism is arranged in the fixed structure 11, and includes: an infrared signal generator 12 and an infrared detector 13; the infrared detector 13 determines whether the output mirror 111 is damaged by receiving the infrared signal generated by the infrared signal generator 12 and reflected by the output mirror 111;

[0043] The signal controller 14 is connected to the infrared signal emitting and detecting mechanism and the seed light source 10 , and provides control signals to the detecting mechanism and the seed light source 10 .

[0044] Specifically, the seed light source 10 is a complete laser capable of laser output, which may be a solid laser, a gas laser or a fiber laser. In this embodiment, the seed light source 10 is a high-power carbon dioxide laser, which can output a 10,000-watt laser by matching a corresponding radio frequency module.

[0045] A laser amplification module is arranged at the light outlet direction of the seed light source 10 for amplifying the laser output power. The output mirror is an optical element of the laser amplification module. The fixing structure 11 can fix the output mirror 110 with an anti-reflection film, so that the amplified laser light is transmitted to the atmosphere through the output mirror 111.

[0046] In this embodiment, the overall structure of the fixing structure 11 is not particularly limited, and any fixing structure 11 that can fix the output mirror 111 is within the protection scope of the present invention.

[0047] Furthermore, a detection chamber is provided inside the fixed structure 11 for accommodating a detection mechanism, so that the infrared signal emitted by the infrared signal generator 12 is reflected by the output mirror 110 and then received by the infrared detector 13 .

[0048] Specifically, the plane where the output mirror 111 is located is used as a reference plane, and the detection chamber is set in a plane parallel to the reference plane and close to the laser output end in the fixed structure. There are two detection chambers, which are symmetrically arranged on both sides of the laser output end, and are used to install the infrared signal generator 12 and the infrared detector 13 respectively. The positions of the infrared signal generator 12 and the infrared detector 13 are adjusted so that the infrared signal emitted by the infrared signal generator 12 is reflected at the center of the laser irradiation of the output mirror 111 and then received by the infrared detector 13.

[0049] In this embodiment, there is no limitation on the fixing method of the infrared signal generator 12 and the infrared detector 13. As an optional embodiment, they can be fixed by spiral connection or bonding.

[0050] In this embodiment, the infrared signal generator 12 emits infrared signals in the wavelength range of 750nm-900nm, and the emission power is 5mW-15mW. The lens made of zinc selenide is sensitive to infrared signals in this wavelength range and can accurately identify abnormal signals. In addition, within the range of 750nm-900nm, when the power of the infrared signal generator is 5mW-15mW, the power stability of the infrared signal generator is good, which further improves the detection accuracy.

[0051] For the output power of the output carbon dioxide laser in the 10,000 watt level, or any high-power laser that needs to cool the laser cavity and uses water cooling, heat dissipation is required. If the seed light source is a high-power carbon dioxide laser, the first water cooling channel can be a liquid channel formed by sleeves on the outside of the laser tube, or a liquid channel formed in the wall of the carbon dioxide laser tube.

[0052] In this embodiment, since both the infrared signal generator 12 and the infrared detector 13 have optimal response operating temperatures, and the temperature near the output mirror may reach several hundred degrees Celsius due to the radiation of the emitted laser, it is necessary to control the temperature of the detection chamber.

[0053] Specifically, a second water cooling circuit is provided in the fixed structure, and the second water cooling circuit is connected to the first water cooling circuit provided in the seed light source, and shares the same external water cooler, and provides circulating cooling water through the water inlet 112 and the water outlet 113. The provision of the second water cooling circuit not only provides a suitable operating environment for the infrared signal generator 12 and the infrared detector 13, but also simplifies the complexity of the device by being connected to the first water cooling circuit.

[0054] Further, such as Figure 1 As shown, the signal controller 14 is connected to the infrared signal generator 12 via a signal trigger circuit 141; connected to the infrared detector 13 via a signal receiving circuit 142; and connected to the laser body 10 via a command control circuit 143;

[0055] When the infrared detector 13 detects an abnormal electrical signal, the signal controller 14 stops sending a trigger signal to the infrared signal generator 12 and sends a stop instruction to the laser body 10 at the same time.

[0056] Specifically, taking the output mirror material as zinc selenide as an example, the output mirror damage detection process of this embodiment is described:

[0057] First, preparatory work is carried out to ensure that the 10,000-watt carbon dioxide laser can output stably and long-term, and at the same time ensure that the laser safety protection device is reliable and effective.

[0058] Specifically, before installing the output mirror, the zinc selenide lens to be tested can be inspected with an optical microscope or an electron microscope to determine whether there are fine scratches, foreign particles, crystal structure defects, etc. on the sample film layer and substrate.

[0059] The zinc selenide lens is installed in the fixed structure, and the positions of the infrared signal generator and the infrared detector are adjusted so that the infrared light emitted by the external signal generator points to the center of the zinc selenide lens.

[0060] The controller controls the infrared transmitter and the infrared detector respectively based on the signal trigger circuit and the signal receiving circuit, measures the intensity of the infrared signal reflected by the zinc selenide lens in the initial state, and completes the initial infrared signal intensity calibration.

[0061] Then, set the signal controller:

[0062] Specifically, the test step length of automatic triggering is set in the signal controller, that is, the infrared signal generator and the infrared detector can work automatically as required, and at the same time, abnormal signal recognition and immediate stop instructions are set so that the signal controller stops sending trigger signals to the infrared signal generator, and uses the instruction control circuit to send a shutdown instruction to the high-power carbon dioxide laser to stop laser emission.

[0063] As an optional implementation, the zinc selenide lens is removed and an optical microscope or electron microscope is used to observe whether the zinc selenide lens is damaged and the severity of the damage, and the damage location and mechanism are analyzed.

[0064] In summary, this embodiment realizes the damage monitoring and identification of the zinc selenide lens in the laser irradiation center by emitting infrared light to the zinc selenide lens and monitoring the intensity of the reflected infrared signal based on the difference in the infrared light reflectivity before and after the damage, and effectively avoids the influence of environmental errors and stray light; at the same time, the required device has a simple structure, low cost, and is easy to automatically control and integrate. It can accurately identify damage based on the measured signal and quickly feedback, which greatly improves the cost-effectiveness of the zinc selenide lens damage test and can provide technical support for the selection and reliability improvement of the window mirror of the domestic 10,000-watt carbon dioxide laser.

[0065] As an optional implementation, the material of the output mirror may also be: GeAs, ZnS or diamond.

[0066] The carbon dioxide laser amplifier in this embodiment has a 10,000-watt laser output and uses a radio frequency electric field to excite carbon dioxide gas to generate plasma, thereby generating a high-power laser. However, radio frequency power supplies are usually accompanied by electromagnetic fields, which may interfere with photodetectors. Therefore, in this embodiment, the material of the fixed structure is selected as metal, which is beneficial to heat dissipation on the one hand, and is used to reduce electromagnetic interference to the infrared signal transmission and detection mechanism on the other hand.

[0067] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other. For the system or device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description.

[0068] The above embodiments are only used to illustrate the technical solutions disclosed in the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments disclosed in the present invention.

Claims

1. A laser amplifier capable of detecting output mirror damage, characterized in that: include: Seed light source, A fixed structure, in which an output mirror is arranged; The detection mechanism is arranged in the fixed structure, and includes: an infrared signal generator and an infrared detector; the infrared detector determines whether the output mirror is damaged by receiving the infrared signal reflected by the output mirror and emitted by the infrared signal generator; A signal controller is connected to the red detection mechanism and the seed light source, and provides control signals for the detection mechanism and the seed light source.

2. The laser according to claim 1, characterized in that A detection chamber is arranged in the fixed structure for accommodating the detection mechanism, so that the infrared signal emitted by the infrared signal generator is reflected by the output mirror and then received by the infrared detector.

3. The laser according to claim 1 or 2, characterized in that: Also includes: A first water cooling circuit is arranged in the seed light source; a second water cooling circuit, disposed in the fixed structure; The first water cooling circuit is connected to the second water cooling circuit, so that the temperature of the detection chamber is within the operating temperature range of the detection mechanism.

4. The laser according to claim 1, characterized in that The signal controller is connected to the infrared signal generator through a signal trigger circuit; connected to the infrared detector through a signal receiving circuit; and connected to the seed light source through a command control circuit; When the infrared detector detects an abnormal electrical signal, the signal controller stops sending a trigger signal to the infrared signal generator and sends a stop instruction to the seed light source at the same time.

5. The laser according to claim 1, characterized in that The seed light source is a carbon dioxide laser.

6. The laser according to claim 5, characterized in that The laser output power outputted through the output mirror is in the order of 10,000 watts.

7. The laser according to claim 5, characterized in that The material of the output mirror is: ZnSe, GeAs, ZnS or diamond.

8. The laser according to claim 5, characterized in that The wavelength range of the infrared signal emitted by the infrared signal generator is: 750nm-900nm.

9. The laser according to claim 8, characterized in that The power range of the infrared signal generator is: 5mW-15mW.

10. The laser according to claim 1, characterized in that The output mirror fixing structure is made of metal.

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