A control procedure for the diameter of a Nd:YVO4 rutile, grown from the melt in a vacuum by edge-defied film-fed growth (E.F.G.) method
by
Liliana Braescu
Department of Mathematics, Polytechnical University of Timisoara, P-ta Regina Maria, No.1, 300004 - Timisoara, Romania
Coauthors: Robert Szabo (Department of Mathematics, The West University of Timisoara), Agneta M. Balint (Department of Physics, The West University of Timisoara), Stefan Balint (Department of Mathematics,The West University of Timisoara)

The objective of this paper is to give a model based control procedure for the diameter of a Nd:YVO4 rutile grown from the melt in a vacuum by E. F. G. method.

For this purpose we find the range of the pulling rate v and the melt temperature T0 couples 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 states. Computations are made for a rutile with a desired radius rf for a set of five values of die radii r0 in the range (rf ;1.6 rf) [mm]. For each of these values of r0 we consider several couples of (v, T0), and compute the corresponding steady-states (r*, h*). By interpolation we find the dependences r*=r*(v, T0, r0), h*=h*(v, T0, r0) and the set S(r0) of those couples (v, T0) for which r*(v, T0, r0)= rf.

Using the curves S(r0) we show that, if during the growth the pulling rate v and/or the melt temperature T0 at the meniscus basis are changed, then the rutile radius is changed too. For a given variation of the pulling rate and/or the melt temperature at the meniscus basis, during the growth, we give a control procedure i.e. a procedure to change adequately the pulling rate in order to obtain a single crystal with the prescribed radius rf.

Keywords: A1.Single crystal growth, A2. Growth from the melt, A2. Edge-defined film-fed growth, B3. Solid-state laser.

PACS codes: 8 1.10.-h; 81.05.Je; 44.40.+a; 02.70.Dh; 44.90.+c

Date received: December 18, 2003

Copyright © 2003 by the author(s). The author(s) of this document and the organizers of the conference have granted their consent to include this abstract in Atlas Conferences Inc. Document # cakt-15.