雲母位相變調板에 관한 硏究

Abstract

By using a sharp point of a needle percussion is given cn to the natural cleavage plane of muscovite mica, and the characteristic percussion figure is observed under microscope. The. star-like percussion figure consists of six line fractures which all meet at the point of percussion at every 60^。of angle. The longest fracture line gives the intersection of the plane of optic axes and the (001) natural cleavage plane, which are perpendicular each other. This method developed in the present experiment is found convinient as it is applicable to a tiny piece of the crystal, and further the conoscope usually available can not give the large convergent angle to cover the exceptionally large of optic axis of mica. In the present work the etch pit of mica is also obtained by using 48% hydrofluoric acid. A great number of chemicals were tried to establish the etch pit, but hydrofluoric acid is found only successful. The etch pit is hexagonal and developes along the line which makes 60˚ of angle in clock-wise to the longest percussion line discussed above. The percussion figure and the etch pit figure have that definite correlation, so that they are both used in determination of the location of the optic axes plane. Upon locating the optic axes plane, the vector phase modulation plates λ/2 plate and λ/4 plate, are produced from mica. Tn this. method the intensity of transmitted light through the polarizer-mica-mica-analyzer system is plodttod against the thickness of mica measured with a micrometer. As shown in the theory the peaK intensity in sinee curve corresponds to the thickness of λ/2 plate and the half of the peak intensity does to λ/4 plate. As this method is entirely independent from the use of any polarimetric component, the instrumental error is mostly excluded.