Abstract: The invention is directed to method of preparing metal fluoride single crystals and particularly to crystals where the metal is calcium, barium, magnesium or strontium, or a mixture thereof. The invention uses a decreasing fast cooling profile and an increasing slow cooling profile for the hot zone and the cold zone, respectively, after crystal formation during cooling from melt temperatures to a first temperature. A substantially constant cooling rate is then applied to the both zones during cooling from the first temperature to a final temperature, usually room temperature. It has been found that the substantially constant cooling rate during the annealing process results in crystals having improved homogeneity and birefringence.

Abstract: The invention is directed to method of preparing metal fluoride single crystals and particularly to crystals where the metal is calcium, barium, magnesium or strontium, or a mixture thereof. The invention uses a decreasing fast cooling profile and an increasing slow cooling profile for the hot zone and the cold zone, respectively, after crystal formation during cooling from melt temperatures to a first temperature. A substantially constant cooling rate is then applied to the both zones during cooling from the first temperature to a final temperature, usually room temperature. It has been found that the substantially constant cooling rate during the annealing process results in crystals having improved homogeneity and birefringence.

Abstract: A method of making an oriented calcium fluoride single crystal includes loading calcium fluoride feedstock on top of a seed crystal having a specific crystallographic orientation, heating the calcium fluoride feedstock to a temperature sufficient to form a melt, and growing a calcium fluoride crystal on the seed crystal by progressively moving the melt and the seed crystal through a temperature gradient zone having an axial temperature gradient in a range from approximately 2° C./cm to approximately 8° C./cm, wherein a growth direction of the calcium fluoride crystal substantially conforms to the crystallographic orientation of the seed crystal.