Experiment and simulation on interface shapes of an yttrium aluminium garnet miniature molten zone formed using the laser-heated pedestal growth method for single-crystal fibers

Abstract

A two‐dimensional simulation was employed to study the melt/air and melt/solid interface shapes of the miniature molten zone formed in a laser‐heated pedestal growth (LHPG) system. Using a non‐orthogonal body‐fitting grid system with the control‐volume finite‐difference method, the interface shape can be determined both efficiently and accurately. During stable growth, the dependence of the molten‐zone length and shape on the heating CO2 laser is examined in detail under both the maximum and the minimum allowed powers with various growth speeds. The effect of gravity on the miniature molten zone is also simulated and the possibility of horizontally oriented LHPG is revealed. Such a horizontal system is good for the growth of long crystal fibers.

Simulation and experiment on laser-heated pedestal growth of chromium-doped yttrium aluminum garnet single-crystal fiber

“…In this paper, we report chromium (Cr) ions in yttrium aluminum garnet (Y 3 Al 5 O 12 ; YAG) crystal in a LHPG system, both experimentally and numerically, after verifying the melt shape [19] and further analysis of heat transfer and fluid flow [20]. The radial profiles of dopants at the growth front are verified by ex-situ measurements in similar conditions.…”

“…Except for the transformation of c, o and T [19], we add the transformation of concentration C with the algebraic coefficients a ¼1/r m , b¼rD, c¼1, and d ¼0. Owing to the non-uniform grid spaces in physical domain, finer fitting near the interfaces makes the fluid flow and temperature distribution more accurate.…”

“…Three boundary conditions of thermal flux and fluid flow [19] are involved for (1) along z axis, (2) at the growth and feed front, and (3) on the surfaces of the source rod, melt, and crystal fiber. The feed front is noted as the lower melt/solid interface near the source rod and the growth front is noted as the upper one near the crystal fiber.…”

“…1 [19,21], a 10.6-mm and M 2 $ 1.1 CO 2 laser system with an attenuator to adjust laser power was the heat source to enter the growth chamber. Power fluctuation can be improved from 75% too 71% using a feedback control.…”

“…Here a 2D simulation, modified from previous model for growing bulk crystals using floating-zone method [18], has been achieved and verified by observations on the melt shapes and volume in steady state [19]. Because a non-orthogonal body-fitting grid system with the control-volume finite-difference method was employed [15], the intermediate boundary behaviors can be determined both efficiently and accurately.…”