Periodic doping in single crystal fibers grown by laser-heated pedestal growth technique

The height of the molten zone was modulated during single crystal fiber pulling by the laser-heated pedestal growth technique to create a periodically doped fiber. Different frequencies, in the order of 10(-3) Hz, were used to modulate the molten zone during the growth of LaAlO3:Cr3+ fibers, a material model. We demonstrated that the axial Cr3+ distribution varied periodically along the length of the fiber at the same frequency as the molten zone oscillations. A dopant distribution model, based on mass conservation, was successfully applied to predict the axial Cr3+ concentration profile. The effective segregation coefficient (k(eff)) of the LaAlO3:Cr3+ was determined to be 4.6 (without molten zone oscillation). The growth temperature was (2340 +/- 10)degreesC and growth was carried out in an air atmosphere. The fiber/pedestal-pulling ratio was equal to 1.0. Transparent fibers 450 mum in diameter and 3 cm in length were obtained. (C) 2002 Elsevier Science B.V. All rights reserved.