Fluoride crystals for IR optics, grown by the PVGF method

Plasma vertical gradient freezing (PVGF) is a method for growing crystals f rom the melt in a vertical temperature gradient using a DC glow discharge h eater. In particular, undoped crystals can be purified during growth becaus e of the complex shape of the vertical temperature gradient. Standard sampl es of LiF and CaF2 single crystals grown by the PVGF method from material o f 99.9% purity have the following parameters: (a) for lambda is an element of [2.5-5 mu m], average transmission coefficient is 97% for LiF and 92.5% for CaF2; (b) repeated (unlimited) pulse power density approximate to 218 w /mm(2) (1 pulse/min, pulse length = 350 mu s, lambda = 2.94 mu m) for LiF s amples. CaF2, and LIF single crystals were grown in a nitrogen atmosphere a t a pressure of 10(-1)-10(-2) Torr. They are used in laser optics. Some of these fluorides can be doped and used as active media, too. (C) 1999 Publis hed by Elsevier Science B.V. All rights reserved.