Sub-leader, Near-Field Optics Group, Special Research Laboratory for Optical Science, Kanagawa Academy of Science and Technology
Size-dependent electroless plating and its application to near-field optical fiber probes
We have developed a scanning near-field optical microscope with a fiber probe, which is expected to be a powerful tool in the development of near-field optical microscopy. Since the spatial resolution of this microscope is determined by the apex size of the probe, fabrication of the probe is very important in the development of high-resolution near-field optical microscopy. Tapering a fiber and making an aperture by coating the tip, except for the apex region, with a metal is an effective method for preparing probes. Previously, we prepared tapered fibers by chemical etching, coating with gold by sputtering, and removal of the gold film covering the apex. However, it is difficult to mass-produce the probes due to low reproducibility during the removal process. We have proposed an electroless plating method which does not require the removal of a metal film. In this method, a nanometer scale apex on a tapered fiber cannot be coated with metal easily because the ease of plating changes with the size of a substrate in electroless plating. The mechanism and temporal dynamics for this effect, as well as methods to control this effect, are not well understood. In this study, we develop physical and chemical methods to control the size-dependence effect in electroless plating. For example, we have added heavy metal ion to the plating bath.
