The fused silica play a key role among the High laser power device as the laser-transmitter. Many factor induced the damaging, such as the surface topography, the defect (bubbles, particulates), the doped-elements which can absorbing the laser-energy. Among them, the absorption of the specific wavelength laser can lead to the heating up which provide the motive power for the Silica tetrahedron Lattice disintegration. We did research on the absorption of the specific wavelength laser to find the relationship among the manufacturing process, the structure of the fused silica and the Laser damage threshold. From the research, there is rarely any relationship between the extent of the absorption of the specific wavelength laser and the OH. While the purity is the key factor.Although the Impure substance will lead to weak absorption, the LIDT of the 1064nm is beyond 100J/cm2.
Silica glass has many excellent properties such as high spectral transmittance and radiation resistance, and is widely used in semiconductors, lasers, optical instruments and other fields. The high performance synthetic silica glass prepared by SiCl4 has the problem of pollution of tail gas and waste water in the process of production, while chlorine-free organic silicon used in the preparation of synthetic silica glass can effectively solve the problem of environmental pollution. In this review, combined with the recent studies on the synthesis of silica glass using octamethylcyclotetrasiloxane(OMCTS, D4) as raw materials, this review mainly review the purification of octamethylcyclotetrasiloxane and the preparation technology of synthetic silica glass, as well as the characteristics of the internal reaction mechanism, and the related technologies, the prospect of synthetic silica glass technology is forecasted.
In this paper, synthetic silica glass was prepared by chemical vapor deposition using hydrogen and oxygen as carrier gases, respectively. Influences of different carrier gases on the distribution of hydroxyl and chlorine content and optical homogeneity in synthetic silica glass were investigated by ultraviolet-visible-near infrared spectrophotometer, X-ray fluorescence spectrometer and laser interferometer. The experimental results indicated that the hydroxyl content of silica glass prepared with hydrogen carrier gas is like a parabolic distribution, and the hydroxyl content decreases from 1270 ppm to 1020 ppm along the center to the edge of the silica glass in the direction of the transparent surface. The chlorine content distribution is the highest in the middle part of the glass, reaching about 60 ppm, while the other parts are basically the same and about 40 ppm. The change of refractive index caused by the distribution of hydroxyl and chlorine content is contrary and counteracts each other, which promotes the optical homogeneity of silica glass to be better. The hydroxyl content of silica glass prepared with oxygen carrier gas presents an inverse parabolic distribution, and the hydroxyl content increases from 880 ppm to 1010 ppm along the center to the edge of the silica glass in the direction of the transparent surface. The chlorine content increases from 60 ppm to 150 ppm and then decreases to about 40 ppm along the center to the edge of the silica glass. Because the distribution of hydroxyl content and chlorine content is extremely uneven, the change of refractive index caused by the distribution of hydroxyl and chlorine content can't offset each other, which leads to the optical homogeneity of silica glass to be poor. Therefore, synthetic silica glass with high optical homogeneity can be prepared by using hydrogen as the carrier gas.
The windows for the aerospace ship application is consist of fused silica and optical-films which can resist the ray-irradiation among the cosmos. For the optical-films produced by RF magnetron sputtering, the ray-irradiation anti-resist character is related with the sputtering temperature and the annealing temperature. As one of the high refractive index materials for the optical-design of the multi-layer optical film, CeOx film were exposed to Co60 irradiation of 107 、108 、and109rad(Si) respectively. The spectrum- transmission line showed the optical character before and after the irradiation. Due to the decreasing of the defect among the film with the raising of the temperature ,the higher the sputtering and annealing temperature, the well anti-irradiation character. The transform of the Ce3+ and Ce4+ is beneficial for the optical character while the E’ center can be moved from the visible-band to the ultraviolet band. But with the raising of the irradiation does, the micro-structure is key for the anti-irradiation character of the CeOx film.
The Oxygen-deficiency and the content and structure of OH had been proved to lead to various laser-irradiated damage threshold. In order to get the principle, we detected the changing tendency of the the Oxygen-deficiency and OH content after the irradiation without damaging. The results showed that the increasing of the Oxygen-deficiency and decreasing of the OH .Which is the result of the structure-collapsing and the effect to delaying the collapsing by Oxygen-deficiency and OH.
The occurrence of the damage among the silica glass being laser-irradiation
is closed related with the hydrogen. The laser of 248nm lead to the structure collapsing to
made the silica glass crystallized. With the crystallized and non- crystallized parts, the 1H
MAS NMR result shows that the concentration of the hydrogen are different of the
damaged and non-damaged silica glass. Which is the evidence for the damage-delaying
by the hydrogen.
The laser damage character of fused silica is studied experimentally. Firstly the distribution of the defects is presented.
Furthermore, the relevancy of the laser damage character and the defects is discussed. Finally, the fluorescence of
damage-occurring is explained. From the result, the way to ameliorate the laser damage character by controlling the
defects is given.
The fused silica have being used as the lens on the spacecraft ,In order to enhanced the optical character, the film works .We studied the changing of the ZnO film on the fused silica under the radiation of the 60Co irradiation which is close to the actual-condition. The anti- irradiation character under the 60Co γ-ray of the is ZnO film not good while the heat-treatment of the film leading to the optimizing of the physical-character under the radiation of the 60Co γ-ray. The cracking of the film is obvious being irradiation.
It is believed that the light emission induced by laser pulse gives some information on the damage initiation mechanics of fused silica. The laser induced fluorescence (LIF) of high purity fused silica irradiated by KrF laser is studied experimentally. LIF bands centered at 650nm of fused silica fused with surplus H2 atmosphere was observed simultaneously with CCD and spectrometer in the cross direction of laser beam. Significant blue-shift of LIF is observed with the irradiation intensity increasing before laser induced breakdown. The technique to improve the signal intensity of LIF and the signal/noise ratio are discussed.
The result shows that the fusing atmosphere and heat treatment process have different affluence on the laser induced damage threshold (LIDT) by 355nm and 248nm laser pules. As for the fused silca, the atmosphere and the temperature during the fuseing and heat treatment process contributes to the changing of structure and micro-composition. For high power 355nm laser pules, the affluence of H2 during the fusing process is benefical to reduced the destructive probability, the LIDT-values is about 20-22.2 J/cm2; But for the 248nm laser pules ,the highest LIDT-values is about 8-10J/cm2 of the fused silca fused with surplus O2 atmosphere. In order to improve the laser damage character, the heat treatment process is one of the effective way for the fused silica. We have investigated the peculiar heat treatment process with O2 atmosphere by 1100℃ can boost the LIDT to 28.2 J/cm2 and 13 J/cm2 by 355nm and 248nm laser pules, while the process time is not as long as better.
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