Examination of Validity of Paraxial Approximation in Second Harmonic Generation Microscopy under Low Numerical Aperture

By using a vectorial approach, the validity of paraxial approximation in second harmonic generation （SHG） microscopy under low numerical aperture （NA） is examined when the sample is a collagen fibril. Due to the larger value of dzzz and tensorial nature of SHG, the component Ez of the focused fieM may have strong effect on the radiation pattern of SHG. Numerical results indicate that when the value of NA exceeds 0.3, the effect of Ez can not be neglected, which results in the invalidation of paraxial approximation in SHG microscopy despite the fact that SHG microscopy is still under low NA focusing.     

表面等离子体增强氧化锌纳米带发光特性的研究

利用简单的化学气相沉积方法在低温下高产量地合成了ZnO纳米带, 并利用磁控溅射对样品进行表面修饰, 制备了Au-ZnO复合纳米带. 通过扫描电镜、透射电镜及微区拉曼等手段系统地研究了表面修饰对ZnO 纳米材料发光性能的影响.结果表明, 在ZnO纳米带上溅射Au纳米颗粒, 可有效增强其近带边发光并使可见发光强度发生淬灭, 从而增强ZnO纳米带的发光性能. ZnO纳米带发光增强因子η最大可达到85倍. 基于Au纳米颗粒的散射、吸收、Purcell增强因子, 以及Ostwald熟化理论, 又进一步探讨了Au-ZnO复合材料的发光机制. 采用表面等离子体耦合的方法可以有效地提高光电半导体器件的发光效率. 关键词： 表面等离体子 光致发光 氧化锌