A control procedure for the shape of a Nd:YAG and Nd:YVO4 cylindrical bar grown by edge-defined film-fed growth method under oscillated furnace pressure
✍ Scribed by A.M. Balint; L. Braescu; R. Szabo; St. Balint
- Publisher
- Elsevier Science
- Year
- 2006
- Tongue
- English
- Weight
- 242 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0925-3467
No coin nor oath required. For personal study only.
✦ Synopsis
The main purpose of this paper is to give a model based proof of the fact that the effect of the variations of the pressure p in the furnace can be compensated by an adequate variation of the pulling rate v in order to assure a constant diameter of a Nd:YAG and Nd:YVO 4 cylindrical bar grown from the melt by EFG method.
Using a nonlinear model, those (p, v) couples are found for which the system of differential equations, which governs the evolution of the crystal radius r = r(t) and the meniscus height h = h(t), has asymptotically stable steady-state solution (r * , h * ). By interpolation the dependencies of r * = r * (p, v), h * = h * (p, v) and the growth path S i.e. those (p, v) couples for which r * (p, v) = r f (where r f represents the desired radius) are determined.
Using the growth path S, for a given variation of the pressure (during the growth) an adequate variation of the pulling rate is found, which assures that the crystal radius constantly equal to r f . Numerical results are given for a Nd:YAG and Nd:YVO 4 cylindrical bar of r f = 2.0 (mm), grown in a furnace in which the vertical temperature gradient is k = 33 (K/mm).