高斯激光诱导非线性薄膜光场热场特性及超分辨图形刻写研究
文献类型：学位论文
| 作者 | 王睿 |
| 学位类别 | 博士 |
| 答辩日期 | 2014 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 魏劲松 |
| 关键词 | 超分辨 光学非线性 薄膜 激光直写 |
| 其他题名 | Gaussian laser induced optical and thermal field Characteristics in nonlinear thin films and applications for super-resolution pattern writing |
| 中文摘要 | 突破衍射极限，实现高密度存储，超分辨成像和微纳结构加工是当今社会的研究重点，本论文从衍射极限定义以及突破衍射极限的一些方法出发，介绍了非线性薄膜超分辨近场技术和激光热刻蚀技术。研究重点是硫系相变合金材料，对这类材料的光学非线性测量，超分辨近场结构的光场，热场的分布特性等方面进行了系统的研究，从理论上解释由非线性薄膜技术所形成的超分辨光斑以及由热刻蚀作用所形成的超分辨光刻点的成因，同时为超分辨薄膜结构的设计提供理论指导。论文工作主要包括以下几个方面： 在非线性测试方面，由于经典z-scan方法无法准确测量半透明材料的缺点，本论文提出了具有实时监测功能的z-scan非线性测量装置和方法。该装置能够方便地测量不同光源下，透明，不透明或半透明材料的非线性折射率和非线性吸收系数，并可以实时观察被测点的表面形貌变化情况以及作用激光的波形功率变化。研究了存在于z-scan测量中的伪非线性吸收，其产生主要来自于z-scan测量中激光变化的入射角度和偏振角度。伪非线性吸收效应与聚焦物镜的数值孔径有关，调节偏振角度能够降低伪非线性吸收的影响，并进行了实验验证。分析了z-scan中的菲涅尔反射对拟合数据的影响，提出一种反射开孔z-scan与透射开孔z-scan联立的方法来准确拟合材料的非线性吸收系数。用Sb2Te3薄膜作为测试样品，将实验数据与理论模型结合，所得的材料非线性吸收系数是采用经典z-scan理论拟合结果的一半，拟合得到的非线性吸收系数更加精确。拟合曲线更符合实验数据。 在光场分布的理论分析方面，提出抛物线近似法分析模型研究非线性薄膜的光场分布特性，将吸收系数和折射率沿径向方向进行抛物线近似，分析了在非线性薄膜中超分辨光斑的形成。对于强非线性折射特性薄膜结构，材料内部形成非线性法布里-珀罗腔，通过干涉调控得到超分辨光斑；对于强非线性吸收薄膜，在非线性饱和吸收材料中形成了一个低于衍射极限的光孔通道，激光光束穿过光孔通道并在非线性饱和吸收薄膜的后表面形成超分辨光斑。 在热场分析方面，提出多层薄膜结构热场分析模型，并编写了计算程序，对非线性多层膜结构中热场分布做了系统的分析，给出了脉冲激光作用于非线性薄膜结构的温度分布和变化特性，由此对相变材料的热刻蚀效应进行了分析。 在非线性薄膜超分辨光刻方面，搭建了高速旋转激光直写光刻装置，采用该装置进行超分辨激光刻写实验。设计和制备了“glass/Si/ZnS-SiO2/AgInSbTe”试样，该试样中Si作为非线性薄膜，AgInSbTe作为光刻薄膜，在激光波长为405nm和聚焦透镜NA为0.40的条件下，制备出最小线宽约为 200nm的结构，该线宽是光斑尺寸的1/6，实现了超分辨激光刻写。另外，使用激光直写技术探索了在硫系相变薄膜上进行灰度光刻，并在Sb2Te3薄膜上得到了高精度的灰度图像，这对高分辨率的微纳图像存储、微艺术品加工和灰度掩膜制备等许多方面具有潜在的应用价值。 |
| 英文摘要 | Overcoming the Abbe diffraction limit and obtaining a superresolution spot have been hot topics because of the important demands in the fields of nanolithography, ultrahigh density data storage, and nanoscale-resolved optical imaging and detection. In this dissertation, diffraction limit and the ways to break the diffraction limit are introduced first. The nonlinear thin films super-resolution near-field technique and laser thermal etching technique are described to overcome the Abbe diffraction limit. Accurate determination of optical nonlinear coefficients of the chalcogenide phase change materials and the distribution characteristic of optical field, thermal field in super-resolution near-field structure are the focus of the research. Super-resolution spot generation using nonlinear thin films super-resolution near-field technique and laser thermal etching technique is analyzed in detail, which can be used to provide theoretical guidance for the design of the super-resolution film structure. The main content of this dissertation is listed below: In z-scan measurement technique, the z-scan measurement with real-time observation is discussed in detail for accurate determination of optical nonlinear coefficients of translucent materials which can not be analyzed in traditional z-scan measurement. Nonlinear refractive index and nonlinear absorption coefficient of transparent, opaque or translucent materials can be measured by different wavelength. The observation parts are added to get the real time optical picture of the sample while measuring. Intensity of the laser power is also monitored. Pseudo-nonlinear absorption characteristics are numerically demonstrated in z-scan measurements even for samples of pure linear absorption materials. Numerical results reveal that the plausible nonlinear effects stem from two sources, namely the changes in the incident angle and azimuth polarization of the focused beam during the z-scan measurement. For a laser beam focused by a lens with a large numerical aperture, the polarization azimuth angle of the incident beam can be adjusted to the corresponding critical angle. Finally, the theoretical analysis is verified experimentally with experiment. We proposed a method and established the corresponding theoretical model and experimental configuration of combining the reflection open-aperture z-scan and the transmission open-aperture z-scan measurements to determine accurately the nonlinear absorption coefficients by considering the Fresnel reflection loss. The Sb2Te3 film was used as an example. The nonlinear absorption coefficient was experimentally measured and theoretically fitted by our model. The theoretical fitting curves are highly consistent with the experimental data, indicating that the theoretical model and the configuration of the experimental setup can reasonably and feasibly obtain an accurate nonlinear absorption coefficient in actual applications In the theoretical analysis of the optical field distribution of nonlinear thin films, a theoretical analytical model called the parabolic approximation analytical model is discussed that considers the absorption coefficient and refractive index in a parabolic approximation profile along the radial direction. By using this model the generation of a super-resolution spot is analyzed in detail, and a numerical simulation subsequently conducted to verify the analytical model. Large nonlinear refraction sample structures are typical nonlinear Fabry–Perot cavity structures. When the thickness of the nonlinear thin film inside the nonlinear Fabry–Perot cavity structure is adjusted to centain value, the constructive interference effect and self-focusing effect can be formed in the central point of the spot, which causes the nanoscale optical hot spot in the central region to be produced. For samples with nonlinear saturation absorption, the optical pinhole channel can be generated under a focused Gaussian laser beam. The central part of the light can be filtered out because of low absorptivity, which causes the super-resolution spot. In thermal field analyzation, the distribution characteristics of optical field and thermal field in super-resolution near-field structure are analyzed by muti-thin film layers model in detail. The dynamic process of laser pulse direct writing nonlinear thin films is simulated by theory. Temperature characteristics of multilayer structure are discussed which explain the laser thermal etching effects of phase change materials In super-reslution lithography of nonlinear thin films, high-speed rotating laser direct-write lithography machine is set up and experimental results of laser direct writing on glass/Si/ZnS-SiO2/AIST structure are produced to verify the analytical model. The structure of glass/Si/ZnS-SiO2/AIST is written by 405nm violet-blue laser focused by objective with NA=0.4. Using Si as nonlinear thin film and AgInSbTe as photoresist we obtain the periodic structures of the minimum line width 200nm, which is 1/6 of the size of incident spot and overcome the diffraction limit. In addition the study of grayscale patterns of chalcogenide phasechange thin films by laser direct writing technique is discussed in detail. The continuous-tone grayscale images are successfully written on Sb2Te3 phase-change thin films. The ability to form grayscale patterns of chalcogenide phasechange thin films reveals many potential applications in high-resolution optical images for micro/nano image storage, microartworks, and grayscale photomasks. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15867]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 王睿. 高斯激光诱导非线性薄膜光场热场特性及超分辨图形刻写研究[D]. 中国科学院上海光学精密机械研究所. 2014. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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