Plate laser beam splitter with mixture-based quarter-wave coating design

Du, Wenjuan; Zhu, Meiping; Shi, Jun; Liu, Tianbao; Zeng, Tingting; Sun, Jing; Yao, Kui; Shao, Jianda

doi:10.1016/j.optlastec.2022.108399

Cited by 10 publications

(5 citation statements)

References 34 publications

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“…The LIDT value is a key specification for thin films used in laser systems [ 39 , 40 ] . Firstly, we analyzed the main factors affecting the LIDT.…”

Section: Resultsmentioning

confidence: 99%

Neural network modeling and prediction of HfO₂ thin film properties tuned by thermal annealing

Gao,

Yin,

Shao

et al. 2024

High Pow Laser Sci Eng

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Plasma-enhanced atomic layer deposition (PEALD) is gaining interest in thin films for laser applications, and postannealing treatments are often used to improve thin film properties. However, research to improve thin film properties is often based on an expensive and time-consuming trial-and-error process. In this study, PEALD-HfO 2 thin film samples were deposited and treated under different annealing atmospheres and temperatures. The samples were characterized in terms of their refractive indices, layer thicknesses and O/Hf ratios. The collected data were split into training and validation sets and fed to multiple back-propagation neural networks with different hidden layers to determine the best way to construct the process-performance relationship. The results showed that the three-hidden-layer back-propagation neural network (THL-BPNN) achieved stable and accurate fitting. For the refractive index, layer thickness and O/Hf ratio, the THL-BPNN model achieved accuracy values of 0.99, 0.94 and 0.94, respectively, on the training set and 0.99, 0.91 and 0.90, respectively, on the validation set. The THL-BPNN model was further used to predict the laserinduced damage threshold of PEALD-HfO 2 thin films and the properties of the PEALD-SiO 2 thin films, both showing high accuracy. This study not only provides quantitative guidance for the improvement of thin film properties but also proposes a general model that can be applied to predict the properties of different types of laser thin films, saving experimental costs for process optimization.

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“…The LIDT value is a key specification for thin films used in laser systems [ 39 , 40 ] . Firstly, we analyzed the main factors affecting the LIDT.…”

Section: Resultsmentioning

confidence: 99%

Neural network modeling and prediction of HfO₂ thin film properties tuned by thermal annealing

Gao,

Yin,

Shao

et al. 2024

High Pow Laser Sci Eng

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“…Refractive index Extinction coefficient BK7 2.51 [33] 1.10 [33] 0.858 [33] 1.505 0 SiO 2 2.20 [34] 1.00 [34] 0.750 [34] 1.414 0 HfO 2 [34] 9.50 2.00 0.270 / / Al 2 O 3 3.98 [5] 1.60 [35] 0.777 [5] 1.585 [18] 0 HfO 2 -Al 2 O 3 5.56 1.71 0.632 1.669 1.82 × 10 -6 HfO x 9.50 2.00 0.270 2.000 [36] 0.07 [36] CeO 2 [7] 7.60 2.00 0.369 2.000 0.20 substrate-coating and layer-layer interfaces, and impurity particles on the substrate surface or in the coating (the seed of nodule defects). The impurity particles include subsurface impurities accumulated during the heating or material particles sputtered during deposition, etc.…”

Section: Methodsmentioning

confidence: 99%

“…A PLBS coating is designed to achieve a T of 50% ± 3% at 1053 nm and an incident angle of 45 PLBS coatings are deposited on BK7 (Φ50 mm × 5 mm) and fused silica substrates, where the former is used for stress characterization and LIDT measurements, and the latter for other measurements. All the substrates are ultrasonically cleaned in deionized water before being loaded into the coating chamber, followed by plasma ion cleaning prior to deposition [18] . The coating chamber is heated to the set temperature and evacuated to a base pressure of 5 × 10 -4 Pa.…”

Section: Coating Preparationmentioning

confidence: 99%

Effect of subsurface impurity defects on laser damage resistance of beam splitter coatings

Zhu

Shi

et al. 2023

High Pow Laser Sci Eng

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The laser-induced damage threshold (LIDT) of plate laser beam splitter (PLBS) coatings is closely related to the subsurface absorption defects of the substrate. Herein, a two-step deposition temperature method is proposed to understand the effect of substrate subsurface impurity defects on the LIDT of PLBS coatings. Firstly, BK7 substrates are heat-treated at three different temperatures. The surface morphology and subsurface impurity defect distribution of the substrate before and after the heat treatment are compared. Then, a PLBS coating consisting of alternating HfO2–Al2O3 mixture and SiO2 layers is designed to achieve a beam-splitting ratio (transmittance to reflectance, s-polarized light) of approximately 50:50 at 1053 nm and an angle of incidence of 45°, and it is prepared under four different deposition processes. The experimental and simulation results show that the subsurface impurity defects of the substrate migrate to the surface and accumulate on the surface during the heat treatment, and become absorption defect sources or nodule defect seeds in the coating, reducing the LIDT of the coating. The higher the heat treatment temperature, the more evident the migration and accumulation of impurity defects. A lower deposition temperature (at which the coating can be fully oxidized) helps to improve the LIDT of the PLBS coating. When the deposition temperature is 140°C, the LIDT (s-polarized light, wavelength: 1064 nm, pulse width: 9 ns, incident angle: 45°) of the PLBS coating is 26.2 J/cm2, which is approximately 6.7 times that of the PLBS coating deposited at 200°C. We believe that the investigation into the laser damage mechanism of PLBS coatings will help to improve the LIDT of coatings with partial or high transmittance at laser wavelengths.

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“…The middle rhombus-shaped part is the stealth area, which is composed of a rhombus-shaped PEC frame with a side length of 3360 μm. To verify the stealth properties of the proposed transmissive cloak, we performed full-wave simulations using the finite integration method [74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91].…”

Section: Unit Structure Designmentioning

confidence: 99%

Broadband achromatic transmission stealth cloak based on all dielectric metasurfaces

Li,

Xu,

Liu

et al. 2024

Phys. Scr.

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The emergence of metasurface technology has brought innovation to the design of optical devices, and many optical devices based on metasurface have been proposed. However, the inherent dispersion of metasurface structures limits their ability to operate at wide frequencies. By changing the geometric parameters of the metasurface unit structure, the unit structure has achromatic properties on the basis of satisfying the phase gradient. Numerical simulation results demonstrate that the proposed multilayer transmissive metasurface stealth cloak has broadband stealth function in the frequency range of 0.7 to 0.77 THz. Achromatic broadband metasurface stealth devices provide new ideas for the design of broadband metasurface stealth devices, and also promote the research of other broadband metasurface optical devices.

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Plate laser beam splitter with mixture-based quarter-wave coating design

Cited by 10 publications

References 34 publications

Neural network modeling and prediction of HfO₂ thin film properties tuned by thermal annealing

Neural network modeling and prediction of HfO₂ thin film properties tuned by thermal annealing

Effect of subsurface impurity defects on laser damage resistance of beam splitter coatings

Broadband achromatic transmission stealth cloak based on all dielectric metasurfaces

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Plate laser beam splitter with mixture-based quarter-wave coating design

Cited by 10 publications

References 34 publications

Neural network modeling and prediction of HfO 2 thin film properties tuned by thermal annealing

Neural network modeling and prediction of HfO 2 thin film properties tuned by thermal annealing

Effect of subsurface impurity defects on laser damage resistance of beam splitter coatings

Broadband achromatic transmission stealth cloak based on all dielectric metasurfaces

Contact Info

Product

Resources

About

Neural network modeling and prediction of HfO₂ thin film properties tuned by thermal annealing

Neural network modeling and prediction of HfO₂ thin film properties tuned by thermal annealing