Yasuhisa Sano

Computer numerically controlled plasma chemical vaporization machining with a pipe electrode for optical fabrication

We have developed a chemical vaporization machining device that has computer numerically controlled plasma, by using a pipe electrode for optical fabrications. In this device, less than approximately 1 atm of pressure, plasma is generated around the tip of a pipe electrode. During the process, a workpiece is scanned against the electrode under computer control to achieve the desired shape to be removed. A workpiece of silica glass plate is shaped by use of this device, and the removal characteristics of the device are examined. The equations to characterize numerically the shape resulting from scanning of a workpiece have been derived. The new device allows the high precision of optics from the micrometer to the nanometer level with high-speed removal. The shaped surface is sufficiently smooth to be suitable for optical use.

Fabrication of optics by use of plasma chemical vaporization machining with a pipe electrode

We figure optical surfaces by plasma chemical vaporization machining (CVM) with a pipe electrode, in which an rf plasma generated at the electrode tip under approximately atmospheric pressure moves over the surfaces. We propose a shaping method in which the movement of plasma on the surfaces can be determined. Flat and aspheric surfaces are successfully figured with the desired peak-to-valley shape accuracy of 0.1 microm. The root-mean-square roughness of the resultant surfaces is at the subnanometer level. These results confirm that the plasma CVM and the shaping method have the capability to fabricate optics with high accuracy.

Pit Formation, Patterning and Flattening of Ge Surfaces in O2-Containing Water by Metal-Assisted Chemical Etching

Metal-assisted chemical etching is a novel method of etching a Ge surface in contact with a noble metal in water. Its basic mechanism involves the catalytic activity of metals to reduce dissolved O2 molecules in water, which accompanies the formation of a soluble oxide (GeO2) on the Ge surface around the metal. Here, we apply this electroless etching to the pit formation, nanoscale patterning and surface flattening of Ge. The fundamental etching properties for these three processes are also presented.