A. Verneuil developed flame fusion to grow sapphire and ruby on a commercial scale around 1890. Flame fusion was
further perfected by Popov in the Soviet Union in the 1930s and by Linde Air Products Co. in the U.S. during World
War II. Union Carbide Corp., the successor to Linde, developed Czochralski crystal growth for sapphire laser materials
in the 1960s. Edge-Defined Film-Fed Growth (EFG) was invented by H. Labelle in the 1960s and the Heat Exchanger
Method (HEM) was invented by F. Schmid and D. Viechnicki in 1967. Both methods were commercialized in the
1970s. Gradient solidification was invented in Israel in the 1970s by J. Makovsky. The Horizontal Directional
Solidification Method (HDSM) was invented by Kh. S. Bagdasorov in the Soviet Union in the 1960s. Kyropoulos
growth of sapphire, known as GOI crystal growth in the Soviet Union, was developed by M. Musatov at the State
Optical Institute in St. Petersburg in the 1970s. Today, half of the world's sapphire is produced by the GOI method.
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