本所3月份演講公告：

【作品名稱】大霹靂
【參賽作者】趙嬿鈞   陳政營   林怡瑞   戴育安 

【作品說明】

藝術性：

強而有力且令人驚艷的散射狀，讓人聯想起宇宙的發展，是否始於這神奇微小的結構中呢？

實物說明：

此結構為ZnO奈米線球，可以看出ZnO放射狀的結構。此奈米線成長的方向為壓電性最強的c軸方向。 

Modal Characteristics of Antiresonant Reflecting Pipe Waveguides for Terahertz Waveguiding

Professor Hung-chun Chang

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

臺灣大學光電所 張宏鈞教授

The pipe waveguide, which is a thin pipe consisting of a large air core and a thin dielectric layer with uniform but low index, is promising for THz waveguiding owing to its low-loss feature and simple structure. In this research, modal characteristics of the leaky core modes of the pipe waveguide are investigated in the THz range. Utilizing the finite-difference frequency-domain (FDFD) mode solver, modal indices and attenuation constants of the core modes which are frequency dependent are calculated for different core diameters, cladding thicknesses, and cladding refractive indices. It is found that at certain frequencies no core modes can exist. Comparing these frequencies with the resonant frequencies of the cladding reveals that the guiding mechanism of the core modes is that of the antiresonant reflecting guiding. Calculated results also suggest that, to have a low-loss and high-bandwidth pipe waveguide, large core diameter, thin cladding thickness, and low refractive index are desired. The effect of material absorption is also examined, which shows that the attenuation constant magnitude will be increased and the increment is more significant at higher frequencies. Moreover, modal patterns are shown for the fundamental mode and the higher order modes, including modal intensity distributions and electric field vector distributions. It is observed that modal patterns of the core modes of the pipe waveguide resemble those of the guided modes of the step-index fiber. From the spectrum of the attenuation constant, it shows that the fundamental mode (HE₁₁-like) has the smallest attenuation constant and is the dominant mode for the pipe waveguide investigated. (Optics Express, vol. 18, no. 1, pp. 309–322, 5 January 2010.)

Fabrication of Sphere-like Au Nanoparticles with Laser Irradiation for Localized Surface Plasmon Resonance Applications

Professor C. C. Yang’s Laboratory

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

臺灣大學光電所 楊志忠教授

We have demonstrated a simple method for fabricating substrate adhesive Au nanoparticles (NPs) of no aggregation based on a process of laser ablation and annealing. The size, shape, surface density, and coverage of Au NPs on a substrate can be controlled by laser energy density, substrate material and surface condition, deposited Au film thickness, and the liquid covering the Au film during laser irradiation. With optical transmission measurements, the in-plane and out-of-plane localized surface plasmon resonance (LSPR) features can be clearly identified due to the similar shapes and vertical alignments of NPs on substrate. The spectral features of substrate-affected LSPR modes rely on the size, Au/substrate contact area, substrate material, and surrounding gas or liquid. Numerical simulations based on the finite-element method show highly consistent results in the LSPR-induced extinction spectral features. Fig. 1 and 2 show the plan- and tilted-view SEM images of Au NPs on a sapphire substrate. Fig. 3 shows the transmission spectra of Au NPs on sapphire and SiO₂ demonstrating the LSPR features. For details, please read the publication: C. Y. Chen et al., Optics Express 17, 14186 (2009).

本篇論文主要使用氮化鎵奈米柱接合再生長的方式來減少線差排(threading dislocation)密度。進行方式為：在傳統的氮化鎵基板上，用奈米壓印的方式於表面上製作出週期性孔洞的二氧化矽，再使用脈衝成長模態 (pulsed growth mode)於有機金屬氣相沉積的環境下成長高品質之氮化鎵奈米柱，再將成長模態轉換至二維成長模態進行接合再生長。圖一為接合再生長之氮化鎵基板之掃描式電子顯微鏡(scanning electron microscopy)橫截面影像，並且在原子力顯微鏡(atomic force microscopy)、穿透式電子顯微鏡(transmission electron microscopy)、深度解析X光繞射(depth-dependent X-ray diffraction)、變溫光激發螢光(temperature-dependent photoluminescence)等量測中，都顯示出此一基板之各項性質都比傳統基板更為優越。圖二為電激發螢光(electroluminescence)量測結果，於此基板上成長之藍光發光二極體比成長於傳統基板之發光二極體增加約百分之八十的發光強度。

圖一、印在一層薄塑膠板上、繞著手指的微型LED顯示器。

圖二、微型化LED製程步驟。

圖三、 可延展的微型LED，印製出來的微型LED相連成一張網，並附著在一個橡膠底層上。