| 摘要 |
PURPOSE:To adhere tightly a vessel for contg. a fused salt and a substrate in the peripheral part of the substrate out of the area in contact with the fused salt by providing a negative pressure chamber which is opened at the bottom end and is airtightly isolated from a chamber contg. the fused salt to the outside circumferential part of said vessel on top of the substrate and evacuating only the negative pressure chamber while maintaining the chamber contg. the fused salt at the atm. pressure. CONSTITUTION:Sulfate, nitrate, etc. contg. the cations contributing to the increase in the refractive index of the substrate glass such as thallium (Tl) and silver (Ag) are put into the chamber 18 for contg. the fused salt in an inside cylinder 11. The inside of a gap 12 (negative pressure chamber) is evacuated. The substrate 15 is thereby tightly adhered and fitted to the vessel 10. The bottom surface side of the substrate 15 is brought into contact with the fused salt 19 in a heating chamber. The electrode plate 23B on the cathode side is immersed and dipped in the salt 19. The salt in the vessel 10 is then melted to the fused salt 20, into which the electrode plate 23A on the anode side is immersed and installed. An ion exchange treatment is executed while a voltage is impressed between the two plates 23A and 23B, then the cations diffuse through the aperture of a mask 16 into the substrate and the ions in the glass leach into the other fused salt 19 from the rear of the substrate 15. A desired optical element 21 such as a lens, waveguide or the like having the refractive index gradient corresponding to the density distribution of the diffused ions is formed in the substrate. |
