QQ客服 官方微博 反馈留言

题名	基于非线性薄膜的远场超分辨光学成像研究
作者	丁晨良
文献子类	博士
导师	魏劲松
关键词	光学成像 optical imaging 超分辨成像 super-resolution 光学非线性 nonlinear optics 装置 devices 薄膜 thin films
其他题名	Far-field super-resolution optical imaging with nonlinear thin films
英文摘要	光学成像技术被广泛运用于纳米科技领域与生物医学领域，现已成为这些领域研究必不可少的工具。但是由于衍射极限的存在，阻碍了光学成像技术的进一步发展。超分辨成像技术的出现，为突破这一极限提供了可能，也为其他相关技术注入了新的发展力量。本文主要研究了非荧光远场超分辨光学成像方法，该方法基于薄膜材料的非线性吸收效应，使聚焦光斑上不同强度部分的透过率不同，进而形成超衍射极限的光斑，实现超分辨成像。 搭建了双光束多功能装置，能够同时进行Z-scan测量、双光束瞬态强度变化测量、瞬态光斑测量及扫描成像，为探究薄膜材料的非线性性能，优化成像的条件，实现超分辨的成像提供基础。并且提出了一种能够在共聚焦显微系统中快速、精确确定针孔轴向位置的方法。 根据理论模型详细地分析了线性吸收系数α0、非线性吸收系数β、入射激光强度I和薄膜厚度L对超分辨效果的影响。成像中需要薄膜厚度远小于系统的瑞利长度，基于非线性饱和吸收的超分辨成像技术需要材料具备以下条件：薄膜厚度L选取的尽可能小（<100nm）；线性吸收系数α0为一个较大的值（>107m-1）；非线性吸收系数β为负值，且绝对值也需要为一个较大的值；入射激光强度I与非线性吸收系数β乘积的绝对值接近线性吸收系数α0。 测量了薄膜材料Sb、InSb、Ge2Sb2Te5、Sb70Te30和AgInSbTe在非晶态下的非线性吸收系数β，测试的激光波长分别为405nm和658nm。结果表明Sb和InSb两种薄膜材料在405nm波长下的非线性饱和吸收系数相对较大，分别为 -6.9×10-2m/W和-3.2×10-2m/W，并且β和I乘积的绝对值也更接近α0。在对Sb和InSb薄膜材料进行瞬态响应的探测中，表明非线性效应的重复可逆性，并且在双光束瞬态光斑的探测中，都观察到了探测光光斑缩小的现象。 利用频率响应函数从理论上分析计算了增加薄膜材料后系统的成像分辨能力，并且采用Sb薄膜和InSb薄膜进行了超分辨成像实验。采用Sb薄膜的成像系统中，在激光波长为405nm，物镜数值孔径为0.25的条件下（极限分辨率为810nm），系统对周期为660nm的点阵结构实现了超分辨成像。此外研究还表明入射光强对系统的分辨能力会产生影响，其存在一个最优值，约为1.653×108 W/m2。采用InSb薄膜的成像系统中，在波长为405nm，物镜数值孔径为0.5的条件下（极限分辨率为405nm），系统对周期为300nm的BD-R基底和BD-ROM基底实现了超分辨成像，分辨能力略微优于Sb薄膜的成像结果。此外还讨论了入射光强和厚度对系统分辨能力的影响，结果表明两者都存在最优值，分别为6.519×108 W/m2左右和30nm。 探讨了利用金属薄膜实现超分辨成像的方法，该方法基于金属薄膜的电子声子碰撞效应温度依赖的特性，引起光斑聚焦区域不同位置的透射和反射率发生变化，实现超分辨成像。在波长为405nm，数值孔径为0.5的条件下，采用Al薄膜对BD-R 光盘基底上100nm宽的台和200nm宽的槽实现了超分辨成像。 最后提出了通过差分获得超衍射极限光斑的方法，该方法基于薄膜材料的非线性反饱和吸收特性。在单光束下，利用退火后的Si-InSb-ZnS-SiO2结构，获得了半径为原来52.5%的差分光斑信号，并且通过实验证明了两差分光束的光强差越小，入射激光的脉冲周期越长，则差分光斑的半径也就越小。在双光束下，同样利用退火后的Si-InSb-ZnS-SiO2结构，通过对激发光作用前后探测光斑的差分，获得了半径为原来50.0%的差分光斑信号。; Optical imaging techniques are widely used and have become indispensable tools for nano science and biomedicine. However, further development is hampered because of the optical diffraction limit. The emergence of super-resolution imaging techniques provides a method to break through the limit, and offers new oppotunities to other related techniques. In this dissertation, we focus on non-fluorescence far-field super-resolution imaging technique. This technique is based on nonlinear absorption characteristic of thin films, which induces the transmittance changes with intensity distribution of the focused spot, then the sub-diffraction-limit spot can be formed and used in super-resolution imaging. A double-beam muti-fuctional optical setup is established, one can use the setup to conduct z-scan measurement, double-beam transient intensity measurement, transient spot detection and laser scanning imaging. This setup provides the basis for studying the nonlinear performance of materials, optimizing the imaging conditions and achieving super-resolution imaging. A fast and accurate method to determine the pinhole location of the confocal laser scanning microscopy is presented. Based on the muti-layer system model, we analyze the influence factors on super-resolution imaging, including linear absorption coefficient α0, nonlinear absorption coefficient β, incident laser intensity I and film thickness L. Because of the limitation of Rayleigh length, the materials for super-resolution imaging technique based on nonlinear absorption characteristic should meet the following requirements: the film thickness L should be small (< 100 nm); the linear absorption coefficient α0 should be a large value (>107 m-1); the nonlinear absorption coefficient β need to be a negative value and the absolute value of it need to be large; and the absolute value of product of the incident laser intensity I and nonlinear absorption coefficient β should be close to the value of α0. The nonlinear absorption coefficient β and transient response process of amorphous thin films are determined, including Sb、InSb、Ge2Sb2Te5、Sb70Te30 and AgInSbTe, where the laser wavelengths are 405 nm and 658 nm. These results show that Sb and InSb thin films have large β values, which are -6.9×10-2 m/W and -3.2×10-2 m/W with 405 nm wavelength, respectively. The absolute value of product of β and I is close to the value of α0. Double-beam transient spots through Sb and InSb thin films are detected, the results show that the transient spots shrink with pump laser intensity. The resolution of imaging system is calculated through frequency response function. Subsequently, Sb and InSb thin films are used for super-imaging. In imaging with Sb thin films, polycarbonate substrates with regular pit arrays prefabricated on surface are chosen as the samples, and the central distance between two adjacent pits is 660 nm. Super-resolution imaging is achieved when the wavelength is 405 nm and the numerical aperture (NA) of objective is 0.25 (diffraction limit of the optical system is 810 nm). Further study shows that the intensity of incident laser will influence the resolution of system, and there is an optimal intensity of around 1.653×108 W/m2. In imaging with InSb thin films, Blu-ray disk recording (BD-R) substrate and Blu-ray read-only memory (BD-ROM) disk substrate are selected as samples. Super-resolution imaging is also achieved when the wavelength is 405 nm and the NA of objective is 0.5 (diffraction limit of optical system is 405 nm). The result is slightly better than that with Sb thin film. In addition, the influence of intensity of incident laser and thin film thickness on imaging results are also studied, and the results show that there are optimal intensity of around 6.519×108 W/m2 and thin film thickness of 30 nm. A far-field super-resolution imaging with metal thin films is proposed, which is based on the temperature-dependent electron–phonon collision frequency effect. In the proposed method, the structures with a land of 100 nm width and a groove of 200 nm widths on the Blu-ray disk substrates are clearly resolved and through a laser scanning microscopy with a laser wavelength 405 nm and objective lens of NA of 0.5. Non-fluorescent difference method to obtain sub-diffraction-limit spot is presented. This method is based on nonlinear reverse saturation absorption (NRSA) characteristic. Using Si-InSb-ZnS-SiO2 thin films, a difference spot is obtained with a single laser beam, the radius of difference spot is about 52.5% of the original spot. The difference spot is further reduced to 50.0% of the original spot through using dual beam method.
学科主题	光学工程
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/31062]
专题	中国科学院上海光学精密机械研究所
作者单位	中国科学院上海光学精密机械研究所
推荐引用方式 GB/T 7714	丁晨良. 基于非线性薄膜的远场超分辨光学成像研究[D].

个性服务

查看访问统计

相关权益政策

暂无数据

收藏/分享

除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。