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

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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