MODEL BASED OPTIMIZATION OF SOME GROWTH PROCESS PARAMETERS OFAND:YAG CYLINDRICAL BAR GROWN IN A VACUUM BY THE EDGE-DEFINED FILM-FED GROWTH METHOD

摘要

The main purpose of this paper is to find those values of the die radius r0, pulling rate v and temperature To at the meniscus basis, which assures the growth of a Nd:YAG monocrystal (blue laser) cylindrical bar with a prescribed diameter 2rf and for which the nonuniformities of the surface of the bar, due to small uncontrollable oscillations of the pulling rate v and melt temperature To, are minimum possible. Numerical results are given for a Nd:YAG cylindrical bar of 5 mm diameter, grown in a furnace in which the vertical temperature gradient is k = 33 K/mm for the following three type of uncontrollable oscillations: Av = 0.001 mm/s, AT=1 K; Av = 0.01 mm/s, AT = 10 K; and Av = 0.02 mm/s, AT = 20 K. The optimal values obtained for r0, v and To are: r0 = 3.6 mm, v = 0.42 mm/s, To = 2248.373 K; r0 = 3.6 mm, v = 0.41 mm/s, To = 2225.273 K; and r0 = 3.6 mm, v = 0.40 mm/s, To = 2262.269 K, respectively. Therefore for a smooth surface, the parameters r0, v and To have to be chosen as follows: r0 = 3.6 mm, v = 0.40 mm/s, To = 2262 K.