Ultraviolet laser-induced damage on fused silica substrate and its sol-gel coating

Boron nitride (BN) nanosheets incorporated silica antireflective (AR) coating was successfully prepared on fused silica substrate to improve the antilaser-damage ability of transmissive optics used in high-power laser systems. The BN nanosheets were obtained by urea assisted solid exfoliation, and then incorporated into basic-catalyzed silica sols without any further treatment. The transmission electron microscope (TEM) images indicated that the BN nanosheets generally consisted of 2–10 layers. The antireflective BN/$\text{SiO}_{2}$ coating exhibited excellent transmittance as high as 99.89% at 351 nm wavelength on fused silica substrate. The thermal conductivity $0.135~\text{W}\cdot \text{m}^{-1}\cdot \text{K}^{-1}$ of the BN/$\text{SiO}_{2}$ coating with 10% BN addition was about 23% higher than $0.11~\text{W}\cdot \text{m}^{-1}\cdot \text{K}^{-1}$ of the pure $\text{SiO}_{2}$ AR coating. The laser-induced damage threshold (LIDT) of that BN/$\text{SiO}_{2}$ coating is also 23.1% higher than that of pure $\text{SiO}_{2}$ AR coating. This research provides a potential application of BN/$\text{SiO}_{2}$ coatings in high-power laser systems.

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Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.5.146 ◽

2014 ◽

Vol 5 ◽

pp. 1334-1340 ◽

Cited By ~ 1

Author(s):

Wataru Nomura ◽

Tadashi Kawazoe ◽

Takashi Yatsui ◽

Makoto Naruse ◽

Motoichi Ohtsu

Keyword(s):

Molecular Structure ◽

Energy Density ◽

Femtosecond Laser ◽

Laser Light ◽

Damage Threshold ◽

Fused Silica ◽

Optical Component ◽

Continuous Irradiation ◽

Silica Substrate ◽

Laser Induced Damage

The laser-induced damage threshold (LIDT) is widely used as an index for evaluating an optical component’s resistance to laser light. However, a degradation in the performance of an optical component is also caused by continuous irradiation with laser light having an energy density below the LIDT. Therefore, here we focused on the degradation in performance of an optical component caused by continuous irradiation with femtosecond laser light having a low energy density, i.e., laser-induced degradation. We performed an in situ observation and analysis of an increase in scattering light intensity in fused silica substrates. In experiments conducted using a pulsed laser with a wavelength of 800 nm, a pulse width of 160 fs and pulse repetition rate of 1 kHz, we found that the scattered light intensity increased starting from a specific accumulated fluence, namely, that the laser-induced degradation had a threshold. We evaluated the threshold fluence F t as 6.27 J/cm2 and 9.21 J/cm2 for the fused silica substrates with surface roughnesses of 0.20 nm and 0.13 nm in R a value, respectively, showing that the threshold decreased as the surface roughness increased. In addition, we found that the reflected light spectrum changed as degradation proceeded. We analyzed the details of the degradation by measuring instantaneous reflectance changes with a pump–probe method; we observed an increase in the generation probability of photogenerated carriers in a degraded silica substrate and a damaged silica substrate and observed a Raman signal originating from a specific molecular structure of silica. From these findings, we concluded that compositional changes in the molecular structure occurred during degradation due to femtosecond laser irradiation having an energy density below the LIDT.

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Ultraviolet Laser Induced Damage Characteristic of SiO2 Single Layers

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.513-517.74 ◽

2014 ◽

Vol 513-517 ◽

pp. 74-77

Author(s):

Wei Sun ◽

Hong Ji Qi ◽

Zhou Fang ◽

Zhen Kun Yu ◽

Hai Yuan Li

Keyword(s):

Physical Vapor Deposition ◽

Sol Gel ◽

Gaussian Model ◽

Damage Threshold ◽

Fused Silica ◽

Threshold Distribution ◽

Laser Induced Damage ◽

Damage Characteristic ◽

Effect Of Surface ◽

Subsurface Defects

Surface and subsurface defects of optics are of major concern in improving laser induced damage threshold. SiO2single layers were fabricated by physical vapor deposition and sol-gel technique on fused silica substrates. HF acid etching and ultrasonic cleaning process are used to investigate the effect of surface and subsurface defects of substrates on the laser induced damage threshold (1-on-1, 8 ns at 355nm). Experimental data are then fitted with the Gaussian model of threshold distribution, which permits to discriminate different kinds of defects and extract their densities and threshold distribution. The interpretation of these data is further discussed according to their cleaning and fabrication method.

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Microwave dielectric properties and optical transmittance of SrTiO3/ZnTiO3 heterolayer thin films fabricated by sol–gel processing

Journal of Advanced Dielectrics ◽

10.1142/s2010135x20500277 ◽

2020 ◽

Vol 10 (06) ◽

pp. 2050027

Author(s):

Yang Li ◽

Biao Xu ◽

Song Xia ◽

Peng Shi

Keyword(s):

Thin Films ◽

Dielectric Properties ◽

Sol Gel ◽

Microwave Dielectric Properties ◽

Optical Transmittance ◽

Fused Silica ◽

Structure Characterization ◽

Silica Substrate ◽

Microwave Dielectric ◽

Dielectric And Optical Properties

SrTiO3/ZnTiO3 heterolayered thin films were fabricated by spin coating Sr–Ti and Zn–Ti sol–gel precursors on fused silica substrate. The SrTiO3 and ZnTiO3 were coated alternatively to form ABAB heterolayered thin films. The thickness of individual layers was tailored by controlling the coating layers. The structure characterization of the thin films showed independent structure of each layer while the microwave dielectric properties and optical band gaps can be tuned by changing the layer configuration. The effects of the layer configuration on the dielectric and optical properties were studied.

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SEM analysis of DC magnetron sputtered beryllium films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100106867 ◽

1988 ◽

Vol 46 ◽

pp. 960-961

Author(s):

E. F. Lindsey ◽

C. W. Price ◽

E. L. Pierce ◽

E. J. Hsieh

Keyword(s):

Fine Structure ◽

Electron Emission ◽

Secondary Electron ◽

Low Voltage ◽

Ion Beam ◽

Secondary Electron Emission ◽

Sem Analysis ◽

Fused Silica ◽

Grain Structure ◽

Silica Substrate

Columnar structures produced by DC magnetron sputtering can be altered by using RF biased sputtering or by exposing the film to nitrogen pulses during sputtering, and these techniques are being evaluated to refine the grain structure in sputtered beryllium films deposited on fused silica substrates. Beryllium is brittle, and fractures in sputtered beryllium films tend to be intergranular; therefore, a convenient technique to analyze grain structure in these films is to fracture the coated specimens and examine them in an SEM. However, fine structure in sputtered deposits is difficult to image in an SEM, and both the low density and the low secondary electron emission coefficient of beryllium seriously compound this problem. Secondary electron emission can be improved by coating beryllium with Au or Au-Pd, and coating also was required to overcome severe charging of the fused silica substrate even at low voltage. The coating structure can obliterate much of the fine structure in beryllium films, but reasonable results were obtained by using the high-resolution capability of an Hitachi S-800 SEM and either ion-beam coating with Au-Pd or carbon coating by thermal evaporation.

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