近场光学虚拟光探针的数值分析

Numerical Simulation Analysis of Near-Field Optical Virtual Probe

虚拟光探针是基于近场光学隐失场干涉原理产生的一种非实体探针，可以应用于近场光学超高密度存储、纳米光刻、近场光学成像、光谱探测、纳米样品的近场光学操作等领域。本研究采用三维时间域有限差分（FDTD）方法对近场光学虚拟光探针的光场分布特性进行了数值模拟计算和比较，分析了孔的形状、大小及偏振态等因素对虚拟光探针光场分布的影响，研究结果表明虚拟光探针的通光效率较普通的纳米孔径光纤探针提高10^2-10^4倍；其光场分布的中间峰的半峰全宽（即虚拟光探针的尺寸）在一定距离范围内基本保持不变，从而可以解决近场光学系统中纳米间距控制的难题，避免光学头与介质的磁撞。优化虚拟光探针的设计参量能有效的抑制虚拟光探针中的旁瓣。文章还给出了应用虚拟探针实现高密度光存储的原理方案。

Virtual probe is a kind of immaterial tip based on the principle of near-field evanescent wave interference, which can be used in near-field high-density optical data storage, nano-lithography, near-field optical imaging and spectral detection, near-field optical manipulation of nano-scale specimen etc. The optical intensity distribution of near-field virtual probe has been numerically simulated by the method of 3-D finite-difference time-domain (FDTD) and the factors that have some influence on the field distribution of virtual probe such as the shape and size of aperture, polarization etc have been analyzed. The result reveals that the transmission efficiency of virtual probe is 102 - 104 times higher than usual nano-aperture probe used in near-field scanning optical microscopy. FWHM of the peak, that is, the size of virtual probe, is constant whatever is the distance in a certain range so that the critical nano-separation control in near-field systems can be relaxed, which the scratch between the optical head and media can be avoided. The optimization of parameters of virtual probe can improve sidelobe suppression. An application scheme of virtual probe in ultrahigh density optical data storage is given.