基于纳米光学天线的扫描近场光学探针研究

Scanning Near-Field Optical Probe Based Nano-Antennas

提出了一种基于纳米光学天线的新型扫描近场光学探针,基本结构是在传统光学探针的下端面集成金属偶极纳米光学天线,当入射光照射金属纳米偶极天线时激发金属表面等离激元共振,在天线间隙处产生了巨大的局域场增强,既提高耦合进入探针的光信号强度,又提高信噪比,实现高分辨率。利用时域有限差分(FDTD)法研究了不同孔径(50,100,130,150,170和200 nm)的新型探针对同一样品的探测结果。照明光源为830 nm平面波,TE极化,扫描高度10 nm。研究结果表明新型探针分辨率随孔径增大时变化规律是先增加后减小,在孔径150 nm时分辨率最高,达45 nm,比同样孔径传统探针分辨率提高近4倍。对比分析了当探针位于样品中心时不同孔径探针端面光场分布图,认为新型探针分辨率变化规律是纳米天线在探针上的有效长度不同所致。对其灵敏度和对比度也进行了初步分析。

A novel probe is put forward based on the nano optical antenna which is added by a metallic dipole nano-antenna onto the tip of the ordinary probe.When the sample light arrives at the nano-antenna,the huge field enhancement will be obtained at the antenna feedback for the surface plasmon resonances produced on the surface of the metal.The light coupled into the probe and the signal-to-noise ratio is increased,and then the higher resolution is realized.Based on the FDTD algorithm the measure results are investigated numerically by different aperture probes for the same sample with the incident wavelength of 830 nm and the scan height of 10 nm.The results show that the the new probe resolution with aperture increass first and then decreases with the change of the aperture diameter and reaches the highest of 45 nm at 150 nm which is four times of the ordinary probe resolution.The optical fields on the probe with different diameter are analyzed.The results show that the change law of the new probe resolution is caused by the different efficient length of nano-antenna on the probe.The results also show that the new probe has higher sensitivity and contrast ratio.