本文選題：熔石英光學(xué)材料 + Mie理論��； 參考：《西南科技大學(xué)》2015年碩士論文

【摘要】：激光應(yīng)用于慣性約束核聚變的設(shè)想被提出及理論和技術(shù)上得到證實后,大型激光驅(qū)動系統(tǒng)的研制受到許多國家的重視。光學(xué)元件的抗損傷能力一直是制約高功率激光系統(tǒng)發(fā)展的一個瓶頸,其表面及體內(nèi)含有的各種缺陷是誘導(dǎo)光學(xué)元件損傷的主要原因之一。熔石英光學(xué)材料是激光系統(tǒng)中常用的光學(xué)元件原材料之一,在材料熔煉及元件加工過程中難以避免地會引入雜質(zhì)顆粒。雜質(zhì)顆粒對入射激光的吸收和調(diào)制會導(dǎo)致光學(xué)元件損傷閾值下降。目前對雜質(zhì)熱效應(yīng)已有深入研究和共識,而關(guān)于雜質(zhì)對入射光場調(diào)制作用的研究不多而且沒有給出一個定量的關(guān)系。本文針對熔石英內(nèi)球形雜質(zhì)顆粒對入射光場的調(diào)制作用,進行了理論建模和計算分析。論文的主要研究內(nèi)容和結(jié)果如下:基于Mie散射理論,建立了熔石英體內(nèi)球形雜質(zhì)顆粒對入射光場調(diào)制的三維模型,針對雜質(zhì)參數(shù)(尺寸、折射率)和激光參數(shù)(波長、平面波、高斯波束)對調(diào)制光場的影響進行了計算仿真和分析。研究結(jié)果表明,對于波長為355 nm的平面波入射,如果雜質(zhì)顆粒的半徑小于?/10,雜質(zhì)對光場的調(diào)制影響不大,可以忽略。當(dāng)顆粒半徑大于?/10時,對非耗散雜質(zhì),光強增強因子(light intensity enhancement factor,LIEF)隨雜質(zhì)折射率與熔石英折射率差值的增大而增大,局部可以達到102量級。當(dāng)折射率小于熔石英的折射率時,后向散射強于前向散射;對于耗散雜質(zhì),其折射率虛部越大,LIEF受折射率實部的影響越小,前向散射強度隨雜質(zhì)顆粒半徑的增大先上升后下降,當(dāng)半徑大于?/2時,后向散射隨雜質(zhì)顆粒半徑增大而增大,且后向散射強于前向散射。光強最強處的位置距雜質(zhì)顆粒表面的最近距離L受雜質(zhì)的折射率和半徑的影響。對于高斯波束入射,雜質(zhì)周圍光強分布規(guī)律與平面波類似,但是束腰半徑對LIEF的影響較大,當(dāng)高斯波束的束腰半徑大于10倍波長時,可以將高斯波束入射退化為平面波入射的情況�？傊�,雜質(zhì)就像埋藏在熔石英內(nèi)部的微透鏡,它對入射光場調(diào)制引起局部光場增強對光學(xué)元件的損傷有很大的影響。本文結(jié)果對于實際應(yīng)用中熔石英的處理有一定的指導(dǎo)意義,在光學(xué)元件制備過程中降低雜質(zhì)顆粒含量,特別是大尺寸顆粒,可以有效的提高光學(xué)元件的抗激光損傷能力從而延長其使用壽命。
[Abstract]:After the idea of laser application in inertial confinement fusion has been put forward and proved theoretically and technically, the development of large laser drive system has received much attention in many countries. The anti-damage ability of optical elements has been a bottleneck restricting the development of high-power laser systems. The defects in the surface and body are one of the main reasons to induce the damage of optical elements. Fused quartz optical material is one of the commonly used raw materials of optical elements in laser system. Impurity particles are inevitably introduced in the process of material melting and element processing. The absorption and modulation of impurity particles to the incident laser will decrease the damage threshold of optical elements. At present, the thermal effect of impurity has been deeply studied and agreed, but there is not much research on the effect of impurity on the modulation of incident light field, and there is not a quantitative relation. In this paper, the modulating effect of spherical impurity particles on incident light field in fused quartz is studied. The main contents and results of this paper are as follows: based on Mie scattering theory, a three-dimensional model for the modulation of incident light by spherical impurity particles in fused quartz is established. The impurity parameters (size, refractive index) and laser parameters (wavelength, plane wave) are studied. The effect of Gao Si beam on the modulated light field is simulated and analyzed. The results show that if the radius of impurity particles is less than 10, the impurity has little effect on the modulation of light field, which can be neglected. For non-dissipative impurities, the light intensity enhancement factor (light intensity enhancement factor) increases with the increase of the difference between the refractive index of impurity and the refractive index of fused quartz when the particle radius is larger than / 10:00, and the local value can reach 102 orders of magnitude. When the refractive index is smaller than the refractive index of fused quartz, the backward scattering is stronger than the forward scattering, and for the dissipative impurity, the larger the refractive index imaginary part is, the smaller the effect of the refractive index real part is, and the forward scattering intensity increases first and then decreases with the increase of impurity particle radius. When the radius is larger than 2, the backscattering increases with the increase of the radius of impurity particles, and the backscattering is stronger than the forward scattering. The nearest distance from the strongest position to the surface of impurity particle L is affected by the refractive index and radius of impurity. For the incidence of Gao Si beam, the distribution of light intensity around the impurity is similar to that of plane wave, but the beam waist radius has a great effect on LIEF. When the beam waist radius of Gao Si beam is more than 10 times wavelength, The incidence of Gao Si beam can be reduced to plane wave incidence. In a word the impurity is like a microlens embedded in the fused quartz which has a great influence on the damage of the optical element caused by the local light field enhancement caused by the modulation of the incident light field. The results of this paper have certain guiding significance for the treatment of fused quartz in practical application, and reduce the content of impurity particles, especially the large size particles, in the process of fabrication of optical elements. It can effectively improve the ability of optical elements to resist laser damage and prolong their service life.
【學(xué)位授予單位】：西南科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TN249

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本文編號：1956508