在纳米光子学中, 提高荧光物质的定向发光强度是许多应用要解决的关键问题。为了优化电介质纳米天线的荧光增强能力, 本文提出了一种由硅纳米球二聚体与TiO2微球组成的电介质球复合纳米天线。通过时域有限差分法, 本文分别从量子产率增强、荧光收集效率增强以及荧光激发率增强3个方面研究了该复合纳米天线对荧光的增强效果。结果表明, 这种复合纳米天线不仅可以解决单个TiO2微球增强荧光时量子产率较低的问题, 还可以弥补单个硅纳米球二聚体增强荧光时荧光收集效率较差的不足。该复合纳米天线可使CdSe量子点的量子产率增强约4倍、荧光收集效率增强约2倍。此外, 由于硅纳米球二聚体与TiO2微球对荧光激发过程具有增强效果, 该复合天线最终可以产生较高的荧光定向增强倍数。在量子点发光的中心波长523 nm处, 荧光定向增强约为3 064倍。

In nano-photonics, the enhancement of the intensity of directional luminescence in fluorescent substances is a key issue for many applications. In order to optimize the fluorescence enhancement capability of dielectric nano-antennas, a dielectric hybrid nano-antenna composed of a silicon nanosphere dimer and a TiO2 microsphere is proposed. Quantum yield enhancement, fluorescence collection efficiency enhancement and fluorescence excitation rate enhancement are all studied using the finite difference time domain method to illustrate the fluorescence enhancement effect of the dielectric sphere hybrid nano-antenna. The results show that the hybrid nano-antenna can not only solve the problem with low quantum yield using the single TiO2 microsphere, but can also compensate for low fluorescence collection efficiency using only the silicon nanosphere dimer. Due to the advantages possessed by both silicon nanosphere dimers and TiO2 microspheres in fluorescence enhancement, the quantum yield and fluorescence collection efficiency of this hybrid nano-antenna are enhanced by about 4 and 2 times, respectively. Moreover, due to the further enhancement effect on the fluorescence excitation process with the silicon nanosphere dimer and the TiO2 microsphere, a higher fluorescence directional enhancement factor can be achieved. When the emission wavelength is at a quantum dot central wavelength of 523 nm, the fluorescence directional enhancement can be up to 3 064 times than that of original fluorescence.