Abstract: A method of making a fluoride crystal suitable for use as an optical element is disclosed. The method includes a mixing step for mixing a prepared raw fluoride material with a scavenger to yield a fluoride mixture. In a preliminary step, the fluoride mixture is formed into a fluoride disk. A grown fluoride crystal is formed by melting and then gradually cooling the fluoride disk in a cylindrical crucible. The grown fluoride crystal is then annealed.

Abstract: In order to provide a fluoride refining method and a fluoride crystal manufacturing method that have great general-purpose properties and can reduce the manufacturing cost and to provide at a low cost a fluoride crystal, an optical part and an aligner the transmission characteristics of which are hardly degraded even when repeatedly irradiated with a high-output light of a short wavelength for a long term, there is provided a method of refining a fluoride comprising the heating step of heating a solid scavenger-added fluoride raw material to melt the raw material and the cooling step of cooling the molten fluoride material to solidify the melt, wherein the environment of a chamber housing the fluoride raw material is changed to such an environment that a gas in the chamber is discharged to the outside of the chamber more easily than the environment before the change, during the heating step.

Abstract: A method of making a fluoride crystal suitable for use as an optical element is disclosed. The method includes a mixing step for mixing a prepared raw fluoride material with a scavenger to yield a fluoride mixture. In a preliminary step, the fluoride mixture is formed into a fluoride disk. A grown fluoride crystal is formed by melting and then gradually cooling the fluoride disk in a cylindrical crucible. The grown fluoride crystal is then annealed.

Abstract: A calcium fluoride crystal in which the light transparency does not deteriorate with consecutive irradiation by high output short wavelength light over long time periods. A calcium fluoride crystal in accordance with the present invention has an internal transmittance of 70% or more for light of a 135-nm wavelength or more. A calcium fluoride crystal contains any one of strontium, aluminum, silicon and magnesium, with the strontium content ranging from 1 ppm to 600 ppm, the aluminum content ranging from 1 ppm to 50 ppm, the silicon content ranging from 1 ppm to 50 ppm, or the magnesium content ranging from 1 ppm to 10 ppm. A calcium fluoride crystal has an internal transmittance of 70% or more for light of a 135-nm wavelength or more and contains 1 ppm or less of La and 10 ppm or less of Y. An optical system for an excimer laser in accordance with the present invention comprises a lens comprising any calcium fluoride crystal set forth above.

Abstract: It is an object of the present invention to provide a calcium fluoride crystal in which the light transparency does not deteriorate with consecutive irradiation by high output short wavelength light over long time periods. A calcium fluoride crystal in accordance with the present invention has an internal transmittance of 70% or more for light of 135-nm wavelength or over. A calcium fluoride crystal contains any one of strontium, aluminum, silicon and magnesium, with the strontium content ranging from 1 ppm to 600 ppm, the aluminum content ranging from 1 ppm to 50 ppm, the silicon content ranging from 1 ppm to 50 ppm, or the magnesium content ranging from 1 ppm to 10 ppm. A calcium fluoride crystal has an internal transmittance of 70% or more for light of 135-nm wavelength or over and contains 1 ppm or less of La and 10 ppm or less of Y. An optical system for an excimer laser in accordance with the present invention comprises a lens comprising any calcium fluoride crystal set forth above.

Abstract: The present invention provides a raw material for manufacturing an inexpensive fluoride crystal with excellent optical characteristics, and a method of manufacturing a fluoride crystal using a carbon fluoride-based gas that can easily be handled and is capable of preventing gases from being taken into a crystal to avoid degradation of transmittance, etc., and provides further a fluoride crystal and a manufacturing method thereof.