Micro-nano Metal Structure Near Field Optical Performance Research

In recent years, the study of nanomaterials and their applications have captured the imagination of people worldwide, and nano metal structures are one of the most popular fields due to their unique optical properties, which were generally attributed to excitation of surface plasmons. Surface plasmons (SP) are collective charge oscillation occurred at the interface between conductors and dielectrics, involving freely propagating electron density waves along metal surface and localized electron oscillations on discontinue nano metal structures, which were corresponding to surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR), respectively. Based on the surface plasmons, nano metal structures enable a wide range of applications, such as light guiding and manipulation at the nanoscale, biodetection at single molecule level and enhanced optical transmission through subwavelength apertures.Our work in this thesis is to study the near-field optical properties of nano metal structures, performed with near-field scanning optical microscope (NSOM) and compared to the simulation results using finite different time domain (FDTD) algorithm. Two kinds of structures are taken into account:1. Metal nanohole arrays:optical transmission can be enhanced through the metal nanohole arrays at specific frequencies, which can be used in bio-detections and optical device. Simulations were carried out with various factors, such as shapes and embedded periods of nanoholes, to study the transmission properties of metal nanohole arrays as well as experiments using NSOM to investigate the near-filed filed distribution. The rhombus, cross star and butterfly shaped gold nanohole arrays were further investigated both with simulation and experiment, the consistent results show the enhanced optical transmission through the nanohole arrays and electromagnetic field enhancement in the surface of the metal nanostructures.2. Metal nano gratings:another typical structures, having a great many specific optical properties. Here we focus on the polarization and dispersive effects of one-dimension grating structures. Two opposite structures:spoke and rings were investigated with NSOM and optical microscope, both near-field and far-field results verified the polarization properties of the nano grating structures, and the optical microscope imaging of the spoke structures also demonstrate that the grating structures can disperse visible light of different wavelengths. Additionally, the experimental results are in agreement with the theoretical simulation results, providing more reference for nano gratings’fabrication and applications.