Optical lithography fluoride crystal annealing furnace

摘要

A method of making below 250-nm UV light transmitting optical fluoride lithography crystals includes applying heat along a shortest path of conduction of a selected optical fluoride crystal, heating the optical fluoride crystal to an annealing temperature, holding the temperature of the optical fluoride crystal at the annealing temperature, and gradually cooling the optical fluoride crystal to provide a low-birefringence optical fluoride crystal for transmitting below 250-nm UV light.