Professor C. C. (Chih-Chung) Yang's Laboratory

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

台湾大学光电所 杨志忠教授

Preparation of a high-concentration Au nanoring (NRI) water solution and its applications to the enhancement of image contrast in optical coherence tomography (OCT) and the generation of photothermal effect in a bio-sample through localized surface plasmon (LSP) resonance are demonstrated. Au NRIs are first fabricated on a sapphire substrate with colloidal lithography and secondary sputtering of Au, and then transferred into water solution through a liftoff process. By controlling the NRI geometry, the LSP dipole resonance wavelength in tissue can cover the spectral range of 1300 nm for OCT scanning of deep tissue penetration. The extinction cross sections of the fabricated Au NRIs in water are estimated to give the levels of 10^-10-10^-9 cm² near their LSP resonance wavelengths. The fabricated Au NRIs are then delivered into pig adipose samples for OCT scanning. It is observed that when resonant Au NRIs are delivered into such a sample, LSP resonance-induced Au NRI absorption results in a photothermal effect, making the opaque pig adipose cells transparent. Also, the delivered Au NRIs in the intercellular substance enhance the image contrast of OCT scanning through LSP resonance-enhanced scattering. By continuously OCT scanning a sample, both photothermal and image contrast enhancement effects are observed. However, by continually scanning a sample with a low scan frequency, only the image contrast enhancement effect is observed. Figure 1 shows the SEM image of an Au NRI. Figure 2 shows the extinction spectra of two NRI samples (A and B) obtained through transmission measurement. The major peak of each curve corresponds to the LSP dipole resonance. Figure 3 shows the OCT scanning image of a pig adipose sample with delivered Au NRIs. The adipose cells have become transparent. Figure 4 shows the lateral line-scan profiles of the OCT images of the heated pig adipose samples with and without Au NRIs. Enhanced scattering through LSP resonance of Au NRIs can be seen.

Fig. 1 SEM image of an Au NRI.	Fig. 2 Extinction spectra of Au NRIs (samples A and B).

Fig. 3 OCT image of a pig adipose sample with Au NRIs.	Fig. 4 Lateral line-scan profiles of the OCT images of the heated pig adipose samples with and without Au NRIs.

Numerical Synthesis of Metallic Nanostructures for Enhancing the Emission of a Dipole through Surface Plasmon Coupling

Professor Yean-Woei Kiang's Laboratory

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

台湾大学光电所 江衍伟教授

In this study, we numerically synthesize a two-dimensional metallic nanostructure consisting of a Au half-space and two separate Ag elliptical cylinders by the simulated annealing (SA) method. The simulated nanostructure is so designed that the surface plasmon polariton (SPP) and the localized surface plasmon (LSP) are simultaneously excited at their common resonant wavelength (535 nm), leading to the enhancement of emission of a nearby dipole source. This enhancement effect is more significant than that of the case where only one of SPP and LSP is excited. In numerically synthesizing a metallic nanostructure, we try to maximize both the downward emission (in the direction away from the metallic structure) and the emission efficiency. A cost function is defined as some combination of the downward emission and the emission efficiency. We adjust the simulated structure by SA to minimize the cost function at a designated resonant wavelength, and calculate and analyze the spectra of downward emission and emission efficiency for the optimal structure. Other structures are also investigated for comparison. From numerical simulations, it is demonstrated that the enhancement of dipole emission is better for optimization at wavelength 535 nm than at other wavelengths. Note that the downward emission and the emission efficiency can reach maxima almost simultaneously when the SPP and the LSP couple effectively at a common resonant wavelength. This implies that the lighting efficiency of green light-emitting diodes (LEDs) can be increased by the coupling effect at a common resonant wavelength of SPP and LSP.

Fig. 1 Variation of cost function in the iteration process. The solid curve represents the cost function and the dashed curve represents the chosen temperature distribution used in the SA process. The synthetic metallic nanostructure is shown schematically in the insert. An x-oriented dipole, denoted by an arrow and labeled by Jx, is located at (x, y) = (0, -h). The metal-dielectric flat interface is at y = 0.

Fig. 2 Spectra of (a) total emission (dashed curve) and downward emission (solid curve), and (b) enhancement factor of total emission (dashed curve) and downward emission (solid curve) for structure A (structure parameters: a = 12 nm, d = 60 nm, t = 10 nm, h = 21 nm).

姓名：田堃正   指导教授：吴忠帜教授

论文题目：微制程技术与光学系统之整合设计与应用—有机可形变面镜与微透镜数组

姓名：谢欣达   指导教授：苏国栋教授

— 数据提供：影像显示科技知识平台 (DTKP, Display Technology Knowledge Platform) —

— 整理：林晃岩教授、陈韦仲 —

MIT同时实现热电转换、太阳能发电和热水供应 

由美国麻省理工学院（MIT）、美国热电转换技术开发公司（GMZ Energy）、美国波士顿学院及阿拉伯联合大公国（UAE）马斯达尔理工学院（Masdar Institute of Science and Technology）所组成研究小组，开发出采用热电转换组件的平板型太阳能发电兼热水供应系统。该系统能够「热电联产」，不仅能发电还能同时供应热水。发电的转换效率为5%左右，同时还能提供50℃左右的热水。

有关技术详情论文已发表在学术杂志《Nature Materials》。该研究提到其发电转换效率比同类型系统提高了7～8倍，今后转换效率还可能达到10%以上。另外，由于制造成本有希望比使用光电转换方式的太阳能电池（PV）低，而且能够供应热水，折旧年限又比太阳能电池长，将来可能会成为太阳能电池的强劲对手。波士顿学院教授任志锋在接受《日经电子》采访时表示：「相对于发电功率的制造成本大约在0.5美元/W。由于还能供应热水，因此完全可以与太阳能电池展开竞争。」

以前也有过利用热电转换组件进行太阳能发电的尝试。但是，很难产生对热电转换至关重要的大温差，而且转换效率非常低，只有0.63%。

此次研究小组透过三大改善措施实现了高转换效率，分别为：（1）开发出利用高效吸收阳光的平板汇聚200～300倍太阳热量的系统，从而确保了温差；（2）用玻璃真空容器包围发电面板，大幅降低热损耗；（3）采用MIT等最近开发的的BiTe类热电转换组件，其ZT指数高达1.03。

实际的面板是利用面积约714 mm²或约1090 mm²的两块铜（Cu）板夹住尺寸为1.35mm×1.35mm×1.65mm的n型和p型两种热电转换材料，然后用玻璃真空容器密封而成。两块铜板中，接受阳光照射的表面铜板上贴有高效吸收阳光的材料，背面铜板上贴有起散热作用的陶瓷板。另外，背面铜板透过水冷式冷却使温度保持在20～60℃。面板的面积是热电转换组件本身面积的196倍或299倍。这种系统与集光式太阳能电池的主要差异在于：不需要大型聚光镜等，能够制成超薄的平板状，不需要追随太阳转动。

当照射一般阳光（其光谱为Air Mass（AM）1.5左右、能量密度为1kW/m²或1.5kW/m²）时，表面Cu板的温度达到160～250℃，最大可发电约60mW。转换效率对冷却端面板的温度依赖性较小，冷却端面板的温度维持在20℃时，转换效率为4.6～5.2%;即使冷却端面板的温度达到50℃，转换效率也保持在3.5～4%。「因此，冷却系统直接就是『热电联产』的太阳能热水器」。

该技术的特点是理论值与实测值差距很小。在论文中，理论转换效率与实际测量值基本上是一致的。理论转换效率大部分取决于热电转换材料的性能。「如果能够实现ZT＝2的热电转换组件，那么发电面板的转换效率就能够达到14%」。

另一方面，制造成本比现有太阳能电池低。因为采用集热式，所以可以采用小型热电转换组件，且无需追随太阳转动，论文部分也提到「（此次采用的）BiTe类材料的采购成本只有0.17美元/W」。另外关于采用真空容器这一点，论文介绍说「在中国，采用真空管的太阳能热水器已经导入73GW以上。这些产品的耐用年限为15年。」此外，此次系统的真空度比原有太阳能热水器差两个等级也没关系。