The Fabrication And Second Harmonic Generation Of Aluminum Nanoparticles Array

Along with the development of micro and nano-fabrication technology, the fabrication of metal nano-structures is gradually developing. The nonlinear optical phenomenon appearing in the process of metal nano-arrays interacting with lasers attracted many attentions. The applications of the metal nano-arrays in optical microscopy, surface enhanced raman scattering, surface enhance fluorescence and biosensing have been widely reported.The second harmonic generation(SHG) in the metal nano-structures has characteristics of stability, wide tuning bandwidth, high quality coherence, high speed response and sensitive polarization. It can be used as an nano-scale coherent light source. And it can be used in laser scanning microscopy, nano-detection and nano-optical devices. Currently, the SHG in the metal nano-structures like Au or Ag nanosphere、nanowire and nanohole have been extensively studied. However, the research for other kinds of metals are rarely involved. The optical properties of Al nano-structures were studied in aspect of the absorption, scattering and surface plasmon resonance. At present, wavelength of SHG in gold and silver nano-structures are mainly located in the visible region(400 nm-750 nm). By introducing aluminum nano-structures the SHG wavelength can be extended to the ultraviolet region(200 nm-400 nm). It will improve the resolution of nano-micro imaging, which is important in high precision detection and sensing. In this paper, the fabrication of aluminum nano-arrays and the SHG of the fabricated arrays excited by femtosecond laser were studied. The main contents are as follows:(1) Periodic nano-particle arrays of aluminum were fabricated with nano-sphere lithography(NSL) and pulsed laser deposition method. Aluminum nano-arrays of different sizes were obtained by changing the deposition time. The transmission spectra were measured in the range from 200 nm to 900 nm by UV-Visible spectrophotometer. We found that the surface plasmon resonance peaks located in the range of ultraviolet. The surface morphology was determined by atomic force microscopy(AFM).(2) The intensity of SHG excited by femtosecond laser with different powers were measured. The results showed that the intensity of SHG is quadratic of the laser power. It verified that the signal was induced by SHG.(3) The influences of the laser polarization leaves on the SHG intensity were studied. The results showed that the surface SHG in the prepared aluminum nano-arrays were mainly induced by interactions between the surface dipole and the incident laser.