Development of scanning near-field optical microscope with a micro rasonator and a optical resonator

点击翻译按钮获取中文摘要

There are many types of Scanning Near-field Optical Microscopes with differenet methods of near-field creation. But most of them can not accept both high spatial resolutions and variety of sample materials. In this report, our proposal of a prototypical SNOM probe consists of a micro resonator and a micro protrusion may solve the problem.Optical micro fabrication which has to be applied to optical waveguides and optical memories needs localization and enhancement of near-field. We have designed and created a new probe, as desribed above, for these purposes. A series of trial experiments showed that there are many sources of stray lights or light scattering around the probe. So a spherical micro resonator is formed from an single mode optical fiber, which was stretched by hand and heated with CO2 laser irradiation. As a result, the glass resonator had a supporting spoke. The end of the spoke was fixed with bond, and the resonator was installed on the quartz substrate to couple an illumi … More nation light without any unexpected light sources. In the next step, the micro protrusion was created from a photoresist with a focal spot of HeCd laser illumination. The laser was focused with a microscope objective, therefore the size of the protrusion was about 1 micron. The light scattering from the micro protrusion was observed by scanning the wavelength of Ti : Sapphire laser, because an appropriate wavelength caused an optical resonance inside the micro resonator. This result confirmed that the prototypical probe might acts as a SNOM probe.We scanned a surface of commercial compact disc as a standard sample with this probe. On the CD surface, there are many pits recorded with well-known sizes (depth=100nm, width=500-800nm, length=870-3180nm). As a result, the pits were sanned clearly, and we confirmed the validity of the prototypical probe. Further improvements will be achieved by an optimization of the probe configuration with computer aided designing as follows.We developed a computer simulation code with three dimensional boudary element method to analyze an electromagnetic wave propagation around the probe. This code simulated a near-field phenomenon of approaching of a sample to a probe. The increase of light scattering from the protrusion with decreasing the distance between probe and sample was simulated well. And also, the influence of the shape and the material of the protrusion on the light scattering was found. This result expected an importance of the optical resonance in the protrusion which size is below the light wavelength.We conclude that this research created an prototypical novel probe for SNOM, and the research results gave us an polestar in further improvement of the SNOM probes for optical nano fabrication. Less