Application of optical near-field excited with ultra fast laser pulses to microfabrication

本研究的目的是利用超快激光脉冲激发的局域光学近场在微细加工中的应用。在此基础上，我们从硬件和软件两个方面设计并开发了一套简单新颖的扫描近场光学显微镜（SNOM）系统。由于光学衍射极限的限制，传统的光学显微镜可能会在视场内构造出半波长大小的聚焦光斑。而近场光学显微镜利用物体表面的光学近场效应，可以获得远低于衍射极限的高空间分辨率。光学近场的研究可以为我们设计一种近场应用的功能探针提供基础。我们的SNOM系统采用在锥形玻璃衬底表面制作的微突起作为SNOM探针。利用超显微技术对该探针进行了照明，并采用三维边界元法（3D-BEM）对该探针的特性进行了数值研究 ...更多信息 程序应用于电磁场。计算结果给出了实现高空间分辨率的理想探针结构参数，以及探针周围光散射的角分布。计算了散射光与探针-样品距离的关系，并与实验结果进行了比较，结果表明，近场光强度与探针-样品间的极化率差成正比。例如，一对介质探针和金属样品可以达到很好的结果。下面是SNOM系统的设计和开发的总结。探头固定-> XY平移台样品台->测角仪尺蠖电源->高响应、低涟漪噪声AD、DA、DIO板->高响应、高分辨率系统软件->易于操作、易于开发因此，SNOM系统通过数字反馈软件对样品表面进行扫描，利用PMT信号控制压电驱动器的伸缩，用5微米聚苯乙烯球探针扫描光栅表面。扫描图像与光栅的光学显微图像一致，图像再现性好。在此基础上，我们利用飞秒激光脉冲在紫外树脂中的聚焦激发，通过多光子过程制备了亚微米级的SNOM探针。我们制作了一个尺寸与激光光斑尺寸相当的突起。但我们还没有创建的探头已设计与我们的三维边界元模拟尚未。我们将发展奈米加工系统以实现奈米探针。少

Aim of this research is the application of localized optical near-field excited with ultra fast laser pulses to micro fabrication. Then we have designed and developed a simple novel Scanning Near-field Optical Microscope (SNOM) system in both hardware and software. The followings are the summaries of this study.A conventional optical microscope may construct a half-wavelength size of the focused light spot in the view area because of the optical diffraction limit. But the SNOM could achieve high spatial resolution far below the diffraction limit by using of optical near-field on the surface of the objects. And the studies of optical near-field could allow us to design a functional probe for near-field application.Our SNOM system adopts a micro protrusion created on the surface of pyramidal glass substrate as a SNOM probe. This probe is illuminated by ultramicroscopic technique.The characteristic of the probe is numerically studied with three dimensional boundary element method (3D-BEM) … More program applied for electromagnetic field. The results show the ideal parameters of the probe configuration for high spatial resolution, and the angular distribution of the light scattering around the probe. The dependence of the scattering light on probe-sample distance is calculated and compared with the experimental results.The intensity of the optical near-field is proportional to the difference of electro susceptibility between probe and sample. For instance, a pair of dielectric probe and metal sample may achieve good result.The following is a summary of the design and development of the SNOM system. Probe holding ---> XY translational stage sample stag ---> goniometer inchworm powe supply ---> high response, low ripple noise AD, DA, DIO board ---> high response, high resolution system software---> easy operation, easy developmentAs a result, the SNOM system scans the sample surface by digital feedback software which controls the extension of piezo actuator with PMT signal.This SNOM system tried to scan the surface of optical grating with five-micron polystyrene sphere probe. The scanned image agreed with the optical microscopic image of the grating, and the image reproducibility was good. The spatial resolution of the image was below one micron.Then we have tried to make sub-micron protrusion for the SNOM probe by multiphoton processes excited with femto-second laser pulses focused in ultraviolet resins. We made a protrusion which size is comparable to the laser spot size. But we have not created the probe which has been designed with our 3D-BEM simulation yet. We will develop nano fabrication system for the realization of nano-probe. Less