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

本研究的目的是将超快激光脉冲激发的局部光学近场技术应用于微加工。然后，我们从硬件和软件两个方面设计并开发了一种简单新颖的扫描近场光学显微镜系统。以下是本研究的总结。由于光学衍射极限的限制，传统的光学显微镜可以在观察区域内形成半波长大小的聚焦光斑。而SNOM利用物体表面的光学近场，可以获得远低于衍射极限的高空间分辨率。对光学近场的研究可以帮助我们设计出一种功能性的近场探头。我们的SNOM系统采用在金字塔形玻璃基板表面产生的微突起作为SNOM探针。该探头采用超显微技术照射。采用三维边界元法（3D-BEM）对探针的特性进行了数值研究。研究结果表明了高空间分辨率下探头结构的理想参数，以及探头周围光散射的角分布。计算了散射光对探针-样品距离的依赖关系，并与实验结果进行了比较。光学近场的强度与探针和样品的电磁化率差成正比。例如，一对介电探针和金属样品可以达到很好的效果。下面是对SNOM系统的设计和开发的总结。探头保持器——> XY平移台采样器——>测角仪寸虫电源——>高响应、低纹波噪声AD、DA、DIO板——>高响应、高分辨率系统软件——>操作简单、开发方便。因此，SNOM系统通过数字反馈软件对样品表面进行扫描，该软件通过PMT信号控制压电致动器的扩展。该SNOM系统尝试用5微米聚苯乙烯球探针对光栅表面进行扫描。扫描图像与光栅光学显微图像吻合，图像重现性好。图像的空间分辨率在1微米以下。然后，我们尝试在紫外树脂中聚焦飞秒激光脉冲激发多光子过程，使SNOM探针产生亚微米的突出。我们做了一个与激光光斑大小相当的突出物。但我们还没有制造出用3D-BEM模拟设计的探针。我们将开发纳米制造系统来实现纳米探针。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