A multi-band laser window suitable for high-power lasers

Abstract

The present application relates to the field of optical element technology, and more specifically, to a multi-band laser window suitable for high-power lasers. The present application discloses a multi-band laser window suitable for high-power lasers with operating bands of 355nm, 532nm, and 1064nm. The window's basic structure includes a substrate, a primary film system, and a secondary film system. The primary film system is located on one side of the substrate, and the secondary film system is located on the other side of the substrate opposite the primary film system. The primary film system includes eight layers of high-refractive index film layers and low-refractive index film layers alternately stacked from the substrate outward according to the primary film system structure. The secondary film system includes eight layers of high-refractive index film layers and low-refractive index film layers alternately stacked from the substrate outward according to the secondary film system structure. This all-pass filter can achieve a transmittance of more than 99.8% at 355nm, 532nm, and 1064nm, and an absorptivity of <2ppm.

Description

Technical Field

[0001] The present application relates to the technical field of optical elements, and in particular to a multi-band laser window suitable for high-power lasers. Background Art

[0002] In the tide of rapid development of modern science and technology, laser technology has shined in many fields with its unique advantages, such as high directivity, high monochromaticity and high energy density. Its application range covers a wide range of aspects, including industrial processing, medical beauty, communication transmission, scientific research and detection. In the laser system, the full-pass filter is a key optical component. It can accurately control the transmission and reflection of light of specific wavelengths, thereby realizing the screening, modulation and optimization of laser signals, and plays an indispensable and important role in ensuring the stability of laser system performance and the normal realization of functions.

[0003] In multi-band laser applications, such as laser processing, complex processing tasks often require the simultaneous processing of lasers of different wavelengths. Ultraviolet lasers with a wavelength of 355nm, due to their extremely short wavelength, enable ultra-fine processing and are widely used in fields such as microelectronic chip manufacturing and precision medical device processing, which require extremely stringent precision. Green lasers at 532nm excel in processing certain special materials, such as marking and cutting certain transparent materials and colored metals. Finally, infrared lasers at 1064nm, with their powerful energy and deep penetration, have become the mainstream choice for cutting and welding metal materials.

[0004] However, the existing full-pass filter coating process encounters difficulties in achieving high transmittance and low absorption in multiple bands, especially in multiple bands with a large span such as 355nm, 532nm, and 1064nm. It is extremely difficult to achieve the goals of high transmittance and low absorption at the same time.

[0005] Taking all factors into consideration, the overall performance of existing full-pass optical filters cannot meet the requirements of high-energy laser applications. Therefore, developing an all-pass optical filter that can simultaneously meet the high-efficiency transmission of multiple working bands such as 355nm, 532nm, and 1064nm is of great significance for improving the quality and efficiency of laser processing. Summary of the Invention

[0006] In view of the many problems existing in the overall performance of existing full-pass optical filters, this application aims to provide a full-pass optical filter with an operating band of 355nm, 532nm, and 1064nm, which can achieve high transmittance and low absorption in multiple bands.

[0007] The multi-band laser window provided in this application, which is suitable for high-power lasers, adopts the following technical solutions:

[0008] A multi-band laser window suitable for high-power lasers comprises a substrate, a main film system and a secondary film system. The main film system is located on one side of the substrate, and the secondary film system is located on the other side of the substrate opposite to the main film system. The film system structure of the multi-band laser window suitable for high-power lasers is: LHLHLHLH|Sub|(HL) 4 , the operating bands are 355nm, 532nm, and 1064nm;

[0009] Among them, Sub is the substrate, LHLHLHLH is the main film system, (HL) 4 is a secondary film system, H is the HfO2 film layer, L is the SiO2 film layer;

[0010] The main film system includes 8 layers of high refractive index film layers and low refractive index film layers alternately stacked from the base outward according to the main film system structure, and the geometric thickness values ​​of the first to eighth layers are: 10.17nm for the first layer, 21.64nm for the second layer, 88.37nm for the third layer, 20.55nm for the fourth layer, 36.27nm for the fifth layer, 39.14nm for the sixth layer, 23.04nm for the seventh layer, and 94.92nm for the eighth layer;

[0011] The sub-film system includes 8 layers of high-refractive-index film layers and low-refractive-index film layers alternately stacked in sequence from the base to the outside according to the sub-film system structure. The geometric thickness values ​​of layers 1-8 are: 10.17nm for the first layer, 21.64nm for the second layer, 88.37nm for the third layer, 20.55nm for the fourth layer, 36.27nm for the fifth layer, 39.14nm for the sixth layer, 23.04nm for the seventh layer, and 94.92nm for the eighth layer.

[0012] Furthermore, the substrate is Herrlich 313 quartz glass.

[0013] Furthermore, the HfO2 film layer is deposited by plasma-assisted dynamic pulsed magnetron sputtering.

[0014] Furthermore, dynamic pulsed magnetron sputtering was used to deposit the HfO2 film. During the initial pre-sputtering, the pulse width was 10-20 μs, the frequency was 10-20 kHz, the duty cycle was 20%-30%, and the power was 200-300 W.

[0015] Furthermore, the pulse parameters are dynamically adjusted as follows: in the early stage of film growth, the pulse power is 300-400W, and the duty cycle is 30%-40%; in the middle stage of film growth, the pulse power and duty cycle are kept unchanged; in the late stage of film growth, the pulse power is 200-300W, and the duty cycle is 20%-30%.

[0016] Furthermore, the SiO2 film layer is deposited by electron beam evaporation combined with reactive gas.

[0017] Furthermore, the evaporation rate of silicon is controlled at 0.08-0.8 nm / s, and the flow rate of oxygen is controlled at 2-8 sccm.

[0018] Furthermore, the multi-band laser window suitable for high-power lasers has a transmittance greater than 99.8% at wavelengths of 355 nm, 532 nm, and 1064 nm, and an absorptivity less than 2 ppm.

[0019] In summary, this application has the following beneficial effects:

[0020] 1. This laser window operates in the 355nm, 532nm, and 1064nm wavelength bands. Its transmittance is >99.8% and its absorptivity is <2ppm in these three wide-span wavelength bands. This performance overcomes the existing all-pass filter coating process's difficulties in achieving high transmittance and low absorptivity in multiple wavelength bands. It can meet the demands of high-energy laser applications and significantly improve the quality and efficiency of laser processing. For example, it enables more precise and efficient processing in laser processing fields such as microelectronic chip manufacturing, precision medical device processing, special material marking and cutting, and metal cutting and welding.

[0021] 2. This application designs a specific film structure and uses a special process of plasma-assisted dynamic pulsed magnetron sputtering to deposit the HfO2 film layer, and a coating process combining electron beam evaporation and reactive gas to deposit the SiO2 film layer. At the same time, the pulse parameters during the HfO2 film deposition process are dynamically adjusted to accurately control the film growth, ensure the uniformity and stability of the film, and thus achieve high performance indicators of the laser window in multiple bands. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is the reflectivity-wavelength curve of the multi-band laser window suitable for high-power lasers according to the embodiment of the present application;

[0024] Figure 2 This is a schematic structural diagram of a multi-band laser window suitable for high-power lasers according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] To more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. It should be understood that the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0026] Unless otherwise specified, all reagents and instruments used were commercially available.

[0027] Example

[0028] Refer to the attached Figure 2 A multi-band laser window suitable for high-power lasers, with an operating band of 355nm, 532nm, and 1064nm, comprising a substrate, a primary film system, and a secondary film system. The primary film system is located on one side of the substrate, and the secondary film system is located on the other side of the substrate opposite to the primary film system.

[0029] The main film system includes 8 layers of high-refractive-index film layers and low-refractive-index film layers alternately stacked from the substrate outward according to the main film system structure. The main film system structure is: substrate / 10.17nmH, 21.64nmL, 88.37nmH, 20.55nmL, 36.27nmH, 39.14nmL, 23.04nmH, 94.92nmL / air;

[0030] The secondary film system includes 8 layers of high refractive index film layers and low refractive index film layers alternately stacked from the substrate outward according to the secondary film system structure. The secondary film system structure is: substrate / 10.17nmH, 21.64nmL, 88.37nmH, 20.55nmL, 36.27nmH, 39.14nmL, 23.04nmH, 94.92nmL / air;

[0031] Wherein, H is a high-refractive-index film layer, and L is a low-refractive-index film layer. In this embodiment, H is an HfO2 film layer, and L is an SiO2 film layer. The substrate is made of Herlex 313 quartz glass, which has the characteristics of low thermal expansion coefficient, few impurities, high heat resistance, moisture resistance, and excellent chemical stability, and is suitable for high-energy lasers.

[0032] The primary and secondary films are deposited on the substrate via vacuum coating. The HfO2 film is deposited via plasma-assisted dynamic pulsed magnetron sputtering. Dynamic pulsed magnetron sputtering precisely controls the sputtering process by changing the parameters of the pulsed power supply. High voltage instantly excites the target surface to generate a high-density plasma. The O2 / Ar mixed gas plasma, synchronously introduced by the RF power supply, enhances the chemical reaction efficiency between Hf atoms and active oxygen through impact ionization, promoting the formation of HfO2 with a precise stoichiometric ratio and improving the stoichiometric ratio and purity of the film.

[0033] The specific process parameters are as follows: during the initial pre-sputtering, the pulse width is 10-20μs, the frequency is 10-20kHz, the duty cycle is 20%-30%, and the power is 200-300W, which cleans the target surface and stabilizes the plasma discharge; in the early stage of film growth, the pulse power is 300-400W, and the duty cycle is 30%-40%; in the middle stage of film growth, the pulse power and duty cycle are kept unchanged; in the late stage of film growth, the pulse power is 200-300W, and the duty cycle is 20%-30%, and hafnium oxide atoms are sputtered from the target surface, activated and accelerated by the plasma, move toward the substrate and deposit on the substrate surface to form an HfO2 film layer. By rotating the sample stage, the substrate is evenly plated, and the thickness of the film layer is monitored in real time. When the film layer thickness reaches a predetermined value, the sputtering is stopped;

[0034] The SiO2 film layer is deposited by combining electron beam evaporation with reactive gas. The electron beam evaporation equipment is used to heat the silicon material and evaporate it into silicon vapor. Then, reactive gases such as oxygen are introduced into the vacuum chamber. The silicon vapor and oxygen react chemically in the chamber to generate SiO2, which is deposited on the surface of the substrate to form a film layer. The specific process parameters are: the evaporation rate of silicon is controlled at 0.08-0.8nm / s, and the flow rate of oxygen is controlled at 2-8sccm. This allows the silicon vapor and oxygen to fully react to generate SiO2. The generated SiO2 moves toward the substrate in a vacuum environment and is deposited to form a film layer. The substrate is evenly plated by rotating the sample holder. The film thickness monitor is used to monitor the film thickness in real time, and evaporation is stopped when the predetermined thickness is reached.

[0035] The optical performance of the multi-band laser window suitable for high-power laser obtained in the embodiment of the present application after double-sided coating was measured by ultraviolet-visible-near-infrared spectrophotometer, and its reflectivity-wavelength curve was referenced to Figure 1 It can be seen that it maintains high transmittance at 300-1200nm, which is suitable for use in the full wavelength range from ultraviolet to infrared. It achieves a transmittance of more than 99.8% at 355nm, 532nm, and 1064nm, and reaches an absorption rate of <2ppm, which enables high transmittance and low absorption in multiple bands, meeting the needs of high-energy laser applications.

[0036] The above are all modifications that a person skilled in the art can make to this embodiment as needed after reading this specification, which do not contribute creatively or solutions that obviously constitute technical inspiration. However, as long as they are within the scope of the claims of this application, they should be protected by patent law.

Claims

1. A multi-band laser window suitable for high-power lasers, comprising a substrate, a primary film system, and a secondary film system, wherein the primary film system is located on one side of the substrate, and the secondary film system is located on the other side of the substrate opposite to the primary film system, characterized in that: The film structure of the multi-band laser window suitable for high-power laser is: LHLHLHLH|Sub|(HL) 4 , the operating bands are 355nm, 532nm, and 1064nm; Among them, Sub is the substrate, LHLHLHLH is the main film system, (HL) 4 is a secondary film system, H is the HfO2 film layer, L is the SiO2 film layer; The main film system includes 8 layers of high refractive index film layers and low refractive index film layers alternately stacked from the base outward according to the main film system structure, and the geometric thickness values ​​of the first to eighth layers are: 10.17nm for the first layer, 21.64nm for the second layer, 88.37nm for the third layer, 20.55nm for the fourth layer, 36.27nm for the fifth layer, 39.14nm for the sixth layer, 23.04nm for the seventh layer, and 94.92nm for the eighth layer; The sub-film system includes 8 layers of high-refractive-index film layers and low-refractive-index film layers alternately stacked in sequence from the base to the outside according to the sub-film system structure. The geometric thickness values ​​of layers 1-8 are: 10.17nm for the first layer, 21.64nm for the second layer, 88.37nm for the third layer, 20.55nm for the fourth layer, 36.27nm for the fifth layer, 39.14nm for the sixth layer, 23.04nm for the seventh layer, and 94.92nm for the eighth layer.

2. The multi-band laser window suitable for high-power laser according to claim 1, characterized in that: The substrate is Hellenic 313 quartz glass.

3. The multi-band laser window suitable for high-power laser according to claim 1, characterized in that: The HfO2 film layer is deposited by plasma-assisted dynamic pulsed magnetron sputtering.

4. The multi-band laser window suitable for high-power laser according to claim 3, characterized in that: Dynamic pulse magnetron sputtering is used to deposit the HfO2 film. During the initial pre-sputtering, the pulse width is 10-20μs, the frequency is 10-20kHz, the duty cycle is 20%-30%, and the power is 200-300W.

5. The multi-band laser window suitable for high-power laser according to claim 3, characterized in that: The dynamic adjustment of pulse parameters is as follows: in the early stage of film growth, the pulse power is 300-400W, and the duty cycle is 30%-40%; in the middle stage of film growth, the pulse power and duty cycle are kept unchanged; in the late stage of film growth, the pulse power is 200-300W, and the duty cycle is 20%-30%.

6. The multi-band laser window suitable for high-power laser according to claim 1, characterized in that: The SiO2 film layer is deposited by electron beam evaporation combined with reactive gas.

7. The multi-band laser window suitable for high-power laser according to claim 6, characterized in that: The evaporation rate of silicon is controlled at 0.08-0.8 nm / s, and the flow rate of oxygen is controlled at 2-8 sccm.

8. The multi-band laser window suitable for high-power laser according to claim 1, characterized in that: The multi-band laser window suitable for high-power lasers has a transmittance greater than 99.8% at wavelengths of 355 nm, 532 nm, and 1064 nm, and an absorptivity less than 2 ppm.

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