High-transmittance lanthanide-doped optical glass for ultraviolet band

Abstract

This invention relates to the field of optical glass technology, and more particularly to a high-transmittance lanthanide-doped optical glass for the ultraviolet band, comprising: a lanthanide ion-doped fluorophosphate glass substrate; and a composite functional coating disposed on the surface of the substrate, the composite functional coating comprising a main functional layer composed of materials containing Li, Mg, and F elements. This invention achieves specific optical functions while maintaining high ultraviolet transmittance by optimizing the lanthanide doping concentration and coating composition. Traditional high-concentration rare-earth doping often exacerbates ultraviolet absorption, while this invention balances optical performance and functional requirements through the synergistic effect of the fluorophosphate matrix and the low-refractive-index coating.

Description

Technical Field

[0001] This invention relates to the field of optical glass technology, and more particularly to a high-transmittance lanthanide-doped optical glass for the ultraviolet band. Background Technology

[0002] Glass, as a functional matrix material, possesses excellent optical homogeneity and compositional flexibility in its amorphous structure. Its optical properties can be directionally controlled by doping with rare-earth ions to meet the design requirements of optical devices with different wavelengths and performance needs. Among these, lanthanide-doped optical glasses exhibit high transmittance in the ultraviolet (UV) band, making them highly promising for applications in UV optical systems, short-wavelength detection, and laser devices. Researchers have achieved efficient light emission, laser processing, and amplification in the visible to infrared region by introducing rare-earth ions into glass and utilizing their 4f electron transition characteristics. However, in the UV region, further optimization of the glass matrix composition and the coordination environment of rare-earth ions is needed to reduce UV absorption loss and improve transmittance. By controlling the basic glass system and combining it with specific lanthanide ion doping, it is possible to significantly improve the transmittance in the UV band while maintaining good formability and chemical stability, while also considering comprehensive properties such as refractive index, dispersion, and radiation resistance. In practical applications, this type of high UV transmittance rare earth glass can be used in high-end optical systems such as UV imaging lenses, UV laser windows, UV detection sensors, and photolithography optical components, meeting the stringent requirements for the UV optical performance of materials in fields such as aerospace, precision instruments, semiconductor manufacturing, and environmental monitoring.

[0003] To achieve specific optical functions, such as upconversion luminescence, existing technologies often require the introduction of high concentrations of lanthanide ions. However, many rare-earth ions exhibit intrinsic 4f-5d or charge-transfer absorption in the ultraviolet (UV) band. High-concentration doping significantly reduces the transmittance of the glass in the UV band, limiting its application in the deep UV region. Furthermore, traditional silicate and borate oxide glasses, due to the intrinsic absorption of their network structural units or trace impurities, typically have UV cutoff edges above 300-350 nm, making it difficult to meet the high transmittance requirements of the deep UV region. Summary of the Invention

[0004] To address the problems mentioned in the background section, the present invention provides a high-transmittance lanthanide-doped optical glass for the ultraviolet band.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A high-transmittance lanthanide-doped optical glass for the ultraviolet band, comprising: Lanthanide ion-doped fluorophosphate glass substrate; And a composite functional coating disposed on the substrate surface, the composite functional coating including a main functional layer composed of materials containing Li, Mg and F elements; the main functional layer is a lithium-magnesium composite fluoride material with a thickness of 30-150nm.

[0006] Furthermore, in the doped fluorophosphate glass substrate, the active dopant ions are selected from Nd... 3+ Er 3+ Yb 3+ or Tm 3+ At least one of them, wherein the molar concentration of the dopant ion is 0.1-2.5%.

[0007] Furthermore, an atomic layer-deposited Al2O3 passivation layer is formed on the outer surface of the composite fluoride coating, the thickness of which is 1-8 nm, preferably 1-5 nm.

[0008] Furthermore, the above-mentioned lanthanide-doped optical glass is prepared by the following steps: S1. The lanthanide-doped fluorophosphate glass substrate is cleaned and dried, including ultrasonic cleaning with organic solvent, alkaline cleaning solution and deionized water in sequence, followed by drying at 50-80℃. S2. A composite fluoride coating is deposited on the substrate surface using a reactive magnetron co-sputtering process, with the deposition rate controlled at 0.5-2 nm / min. S3. Perform in-situ post-treatment on the coating obtained by deposition in step S2; S4. An Al2O3 passivation layer is prepared on the post-treated coating surface using an atomic layer deposition process.

[0009] Further, the reactive magnetron co-sputtering process in step S2 is as follows: using LiF ceramic target and MgF2 ceramic target as sputtering sources, co-sputtering is performed in a mixed atmosphere containing fluorine compensation gas CF4, wherein the volume flow rate ratio of Ar to CF4 in the mixed atmosphere is (8-9):1, the substrate temperature is 180-220℃, the ratio of RF power density of LiF target to MgF2 target is (0.7-0.8):1, and the distance between the substrate sample stage and the target material is 8-12 cm.

[0010] Furthermore, the process conditions for reactive magnetron co-sputtering deposition also include: a chamber working pressure of 0.7-0.9 Pa, and a substrate sample stage rotating at a rate of 10-30 rpm; the chamber is evacuated to a background vacuum below 5.0 × 10⁻⁶ Pa before deposition. -4 Pa, and pre-sputter for 5-15 minutes to clean the target surface.

[0011] Furthermore, the in-situ post-processing in step S3 includes: S3a. Under an Ar atmosphere, the coating surface is bombarded with a wide beam of argon ions with an energy of 40-60 eV for 3-10 minutes, and the ion beam current density is 20-50 μA / cm². 2 ; S3b. The coating is vacuum annealed for 0.5-2 minutes in an Ar atmosphere at a temperature of 200-250℃, with the pressure inside the cavity maintained at 1-5 Pa during annealing.

[0012] Furthermore, in step S4, the atomic layer deposition process uses trimethylaluminum and deionized water as precursors, the deposition temperature is 80-120℃, the number of deposition cycles is 10-30, and the Al2O3 growth thickness in each cycle is 0.08-0.12nm.

[0013] The beneficial effects of this invention are: 1. In the technical solution of this invention, high transmittance in the ultraviolet band is achieved by using lanthanide-doped fluorophosphate glass as a substrate and combining it with a surface composite fluoride coating. Fluorophosphate glass itself has a low ultraviolet absorption cutoff edge, while lanthanide doping optimizes the ultraviolet optical properties of the glass and reduces losses caused by the intrinsic absorption of rare earth ions. Simultaneously, the fluoride coating has a low refractive index and a wide transmission range, forming a good optical match with the substrate and further reducing interface reflection losses.

[0014] 2. In the technical solution of this invention, a composite fluoride coating is deposited using a reactive magnetron co-sputtering process, and in-situ post-treatment is employed to optimize the microstructure of the coating. The coating prepared by this invention has a lower defect density and higher stability, and can maintain consistent optical performance under long-term ultraviolet irradiation, temperature cycling, or humidity changes, avoiding coating cracking or peeling and extending the service life of optical components.

[0015] 3. In the technical solution of this invention, an effective protective barrier is formed by depositing an Al2O3 passivation layer on the surface of the fluoride coating through atomic layer deposition. The Al2O3 layer is dense and chemically inert, which can prevent the penetration of environmental moisture and pollutants, and avoid performance degradation caused by moisture decomposition or fluorine loss of the fluoride coating.

[0016] 4. This invention achieves specific optical functions while maintaining high ultraviolet transmittance by optimizing the lanthanide doping concentration and coating composition. Traditional high-concentration rare earth doping often exacerbates ultraviolet absorption, while this invention balances optical performance and functional requirements through the synergistic effect of the fluorophosphate matrix and the low-refractive-index coating. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Unless otherwise specified, the raw materials used in this invention are all from commercially available conventional products. Example 1

[0019] A high-transmittance lanthanide-doped optical glass for ultraviolet band is prepared by the following steps: S1, for 0.5 mol% Nd doped 3+ The fluorophosphate glass substrate was cleaned and dried in sequence: it was ultrasonically cleaned for 15 minutes each with acetone, alkaline glass cleaning solution and deionized water, and then dried in a clean oven at 60°C for 30 minutes. S2. A composite fluoride coating is deposited on the substrate surface using reactive magnetron co-sputtering: The treated substrate is placed in the deposition chamber, and the vacuum is evacuated to a background vacuum of 4.0 × 10⁻⁶. -4 Pa, a mixture of Ar and CF4 gas was introduced, and the Ar / CF4 volume flow rate ratio was controlled at 8.5:1. The working pressure of the chamber was stabilized at 0.8 Pa. LiF and MgF2 targets were pre-sputtered for 10 min to clean the target surfaces. Then, the substrate temperature was controlled at 200℃, the sample stage was rotated at a speed of 20 rpm, the RF power density of the LiF target was adjusted to 1.5 W / cm², and the RF power density of the MgF2 target was adjusted to 2.0 W / cm². Co-sputtering deposition was performed at a distance of 10 cm from the target material, and the deposition rate was controlled at 1.2 nm / min until the coating thickness reached 80 nm. S3. Perform in-situ post-treatment on the coating obtained in step S2: S3a. Under an Ar atmosphere (pressure 1 Pa), the coating surface is bombarded for 5 min with a wide beam of argon ions with an energy of 50 eV and a beam density of 30 μA / cm². S3b, Subsequently, the coating was vacuum annealed for 1 hour at 220°C in an Ar atmosphere (pressure 2 Pa); S4. An Al2O3 passivation layer is prepared on the post-treated coating surface using an atomic layer deposition process: using trimethylaluminum and deionized water as precursors, 20 deposition cycles are performed at a deposition temperature of 100°C. Each cycle is followed by a trimethylaluminum pulse, nitrogen purging, a water pulse, and nitrogen purging to obtain an Al2O3 passivation layer with a thickness of approximately 2 nm. Example 2

[0020] A high-transmittance lanthanide-doped optical glass for ultraviolet band is prepared by the following steps: S1, for 1.5 mol% Yb doped 3+ The fluorophosphate glass substrate was cleaned and dried in sequence: it was ultrasonically cleaned for 20 minutes each with isopropanol, alkaline glass cleaning solution and deionized water, and then dried in a clean oven at 70°C for 40 minutes. S2. A composite fluoride coating is deposited on the substrate surface using reactive magnetron co-sputtering: The treated substrate is placed in the deposition chamber, and the vacuum is evacuated to a background vacuum of 3.5 × 10⁻⁶. -4 Pa, a mixture of Ar and CF4 gas was introduced, and the Ar / CF4 volume flow rate ratio was controlled at 8.2:1, with the working pressure of the chamber stabilized at 0.75 Pa. LiF and MgF2 targets were pre-sputtered for 8 min. Then, the substrate temperature was controlled at 190 °C, the sample stage was rotated at a rate of 15 rpm, the RF power density of the LiF target was adjusted to 1.2 W / cm², and the RF power density of the MgF2 target was adjusted to 1.7 W / cm². Co-sputtering deposition was performed at a distance of 9 cm from the target material, and the deposition rate was controlled at approximately 0.9 nm / min until the coating thickness reached 50 nm. S3. Perform in-situ post-treatment on the coating obtained in step S2: S3a. Under Ar atmosphere (pressure 1.5 Pa), the coating surface is bombarded for 8 min with a wide beam of argon ions with energy of 45 eV and beam density of 25 μA / cm². S3b, Subsequently, the coating was vacuum annealed for 1.5 h at 210 °C in an Ar atmosphere (pressure 3 Pa); S4. An Al2O3 passivation layer is prepared on the post-treated coating surface using an atomic layer deposition process: using trimethylaluminum and deionized water as precursors, 15 cycles of deposition are performed at a deposition temperature of 90°C to obtain an Al2O3 passivation layer with a thickness of approximately 1.5 nm. Example 3

[0021] A high-transmittance lanthanide-doped optical glass for ultraviolet band is prepared by the following steps: S1, for 0.2 mol% Tm doping 3+ and 0.8 mol% Er 3+ The fluorophosphate glass substrate was cleaned and dried in sequence: it was ultrasonically cleaned for 25 minutes each with ethanol, alkaline glass cleaning solution and deionized water, and then dried in a clean oven at 55°C for 35 minutes. S2. A composite fluoride coating is deposited on the substrate surface using reactive magnetron co-sputtering: The treated substrate is placed in the deposition chamber, and the vacuum is evacuated to a background vacuum of 4.5 × 10⁻⁶. -4Pa, a mixture of Ar and CF4 gas was introduced, and the Ar / CF4 volume flow rate ratio was controlled at 8.8:1. The working pressure of the chamber was stabilized at 0.85 Pa. LiF and MgF2 targets were pre-sputtered for 12 min. Then, the substrate temperature was controlled at 215℃, the sample stage was rotated at a rate of 25 rpm, the RF power density of the LiF target was adjusted to 1.8 W / cm², and the RF power density of the MgF2 target was adjusted to 2.3 W / cm². Co-sputtering deposition was performed at a distance of 11 cm from the target material, and the deposition rate was controlled at approximately 1.6 nm / min until the coating thickness reached 120 nm. S3. Perform in-situ post-treatment on the coating obtained in step S2: S3a. Under Ar atmosphere (pressure 1 Pa), the coating surface is bombarded for 4 min with a wide beam of argon ions with energy of 55 eV and beam density of 40 μA / cm². S3b, Subsequently, the coating was vacuum annealed for 45 min at 240 °C in an Ar atmosphere (pressure 4 Pa); S4. An Al2O3 passivation layer is prepared on the post-treated coating surface using an atomic layer deposition process: using trimethylaluminum and deionized water as precursors, 25 deposition cycles are performed at a deposition temperature of 110°C to obtain an Al2O3 passivation layer with a thickness of approximately 2.8 nm. Example 4

[0022] The difference between this embodiment and Embodiment 1 is that the thickness of the main functional layer of the composite fluoride coating is 30 nm, and the thickness of the Al2O3 passivation layer deposited in step S4 is 1 nm. The remaining steps are the same as in Embodiment 1. Example 5

[0023] The difference between this embodiment and Embodiment 2 is that the thickness of the main functional layer of the composite fluoride coating is 150 nm, and the thickness of the Al2O3 passivation layer deposited in step S4 is 5 nm. The remaining steps are the same as in Embodiment 2. Example 6

[0024] The difference between this embodiment and embodiment 3 is that the volume flow ratio of Ar to CF4 in the mixed atmosphere used for reactive magnetron co-sputtering in step S2 is 19:1, and the in-situ post-treatment in step S3 is not performed. The remaining steps are the same as in embodiment 3.

[0025] Comparative Example 1 The difference between this comparative example and Example 2 is that in step S2, a single LiF target is used instead of the co-sputtering of the LiF and MgF2 targets, and the RF power density of the LiF target is adjusted to make the deposition rate similar to that of Example 1. The remaining steps are the same as in Example 1.

[0026] Comparative Example 2 The difference between this comparative example and Example 2 is that in step S2, a single MgF2 target is used instead of the co-sputtering of the LiF and MgF2 targets, and the RF power density of the MgF2 target is adjusted to make the deposition rate similar to that of Example 2. The remaining steps are the same as in Example 2.

[0027] Comparative Example 3 The difference between this comparative example and Example 3 is that step S4 is omitted, while the remaining steps are the same as in Example 3.

[0028] The optical properties of the samples were evaluated using a double-beam UV-Vis spectrophotometer (Lambda 950). Before testing, all samples from Examples 1-6 and Comparative Examples 1-3 (including an uncoated fluorophosphate glass substrate as a reference) were stabilized for 24 hours at a temperature of (23±2) °C and a relative humidity of (50±5)%. The test wavelength range was 200-800 nm, with a scanning interval of 1 nm and a slit width of 2 nm. After background correction using air as a baseline, the uncoated substrate was scanned first to obtain the reference spectrum, followed by measurements of each sample. Each sample was measured three times after rotation at different angles, and the average value was taken as the final transmission spectrum. The transmittance at wavelengths of 250 nm, 300 nm, and 350 nm was extracted, and the average transmittance in the 200-400 nm UV band was calculated. The calculation formula is as follows: Where N is the total number of wavelength points, and T(λ) is the transmittance value at wavelength λ.

[0029] The test results are shown in Table 1: Table 1. Ultraviolet-Visible Light Transmittance Test Results

[0030]

[0031] As shown in Table 1, the average transmittance of the samples in Examples 1-3 in the 200-400 nm ultraviolet band was significantly higher than that of the uncoated substrate, and superior to that of Comparative Examples 1 and 2. The antireflection effect of the film is due to its refractive index being between that of air and glass substrates. LiF and MgF2 are both excellent low refractive index materials. The transmittance improvement of Comparative Examples 1 and 2 was limited, and even lower than that of the uncoated substrate. This may be because single-component films are difficult to achieve optimal antireflection over a wide spectral range, and the microstructure of a single film may contain more defects leading to light scattering. The LiF / MgF2 co-sputtering process used in Examples 1-3 may have formed a LiMgF3 composite phase or constituted a gradient refractive index structure. This composite structure can achieve a smooth transition of refractive index over a wider range, thereby more effectively suppressing Fresnel reflection throughout the ultraviolet band (200-400 nm) and obtaining a higher average transmittance. This proves that the fluorides of Li and Mg have a synergistic effect during co-deposition, rather than a simple summation.

[0032] The average UV transmittance of Example 6 was significantly lower than that of Examples 1-3, only comparable to that of the uncoated substrate. In reactive sputtering, CF4, as a fluorine compensation gas, effectively compensates for the stoichiometric imbalance caused by fluorine loss during sputtering. The excessively low CF4 ratio in Example 6 may lead to fluorine vacancy defects in the deposited fluoride coating. These defects can become light scattering centers and may introduce impurity energy levels, increasing UV absorption and scattering, thereby resulting in decreased transmittance.

[0033] The refractive index of atomically deposited Al₂O₃ is higher than that of the fluoride coating. Data from Comparative Example 3 demonstrates that, in its initial state, the Al₂O₃ passivation layer is not the direct cause of increased transmittance. Its primary function is to protect the underlying fluoride coating from environmental corrosion; its thickness needs precise control (1-5 nm). Excessive thickness may introduce additional reflection loss due to refractive index mismatch. In Example 4, the passivation layer may have been too thin, resulting in insufficient protection; Example 5, however, achieved a balance between protection and optical performance.

[0034] In summary, Examples 1-3, through LiF / MgF2 co-sputtering to form a composite fluoride coating and combining it with optimized reactive gas ratios and key in-situ post-processing techniques, produced antireflective films with high transmittance in the ultraviolet band. Their high performance stems from the excellent broad-spectrum antireflective properties of the composite coating and its highly dense, low-defect microstructure. The Al2O3 passivation layer primarily serves a protective function and does not affect the initial optical performance.

[0035] In the description of this specification, the reference to terms such as "embodiment," "various embodiments," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or preparation example is included in at least one embodiment of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-transmittance lanthanide-doped optical glass for the ultraviolet band, characterized in that, include: Lanthanide ion-doped fluorophosphate glass substrate; And a composite functional coating disposed on the surface of the substrate, the composite functional coating comprising a main functional layer composed of materials containing Li, Mg and F elements.

2. The optical glass according to claim 1, characterized in that, In the lanthanide-doped fluorophosphate glass substrate, the active dopant ions are selected from Nd... 3+ Er 3+ Yb 3+ or Tm 3+ At least one of them.

3. The optical glass according to claim 1 or 2, characterized in that, The outer surface of the composite fluoride coating is also covered with an atomic layer deposited Al2O3 passivation layer, the thickness of which is 1-5 nm.

4. The optical glass according to claim 1, characterized in that, It is prepared by the following steps: S1. Clean and dry the lanthanide-doped fluorophosphate glass substrate; S2. The composite fluoride coating is deposited on the surface of the substrate using a reactive magnetron co-sputtering process. S3. Perform in-situ post-treatment on the coating obtained by deposition in step S2; S4. An Al2O3 passivation layer is prepared on the post-treated coating surface using an atomic layer deposition process.

5. The optical glass according to claim 4, characterized in that, The reactive magnetron co-sputtering process described in step S2 is as follows: using a LiF ceramic target and a MgF2 ceramic target as sputtering sources, co-sputtering is performed in a mixed atmosphere containing fluorine compensation gas CF4, wherein the volume flow rate ratio of Ar to CF4 in the mixed atmosphere is (8-9):1, the substrate temperature is 180-220℃, and the ratio of the radio frequency power density of the LiF target to the MgF2 target is (0.7-0.8):

1.

6. The optical glass according to claim 5, characterized in that, The process conditions for reactive magnetron co-sputtering deposition also include: a chamber working pressure of 0.7-0.9 Pa and a substrate sample stage rotating at a rate of 10-30 rpm.

7. The optical glass according to claim 4, characterized in that, The in-situ post-processing described in step S3 includes: S3a. Under an Ar atmosphere, the coating surface is bombarded with a wide beam of argon ions with an energy of 40-60 eV for 3-10 minutes. S3b. The coating is vacuum annealed for 0.5-2 minutes in an Ar atmosphere at a temperature of 200-250°C.

8. The optical glass according to claim 4, characterized in that, The atomic layer deposition process described in step S4 uses trimethylaluminum and deionized water as precursors, with a deposition temperature of 80-120℃ and a deposition cycle count of 10-30 cycles.

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