Preparation, properties and application of sapphire single-crystal fibers grown by the EFG method

Abstract

Abstract. Sapphire -the single crystal of aluminum oxide (Al 2 O 3 ) -is one of the most important artificially produced materials. The sapphire fibres studied were grown in Crytur using the "edge-defined film-fed growth" (EFG) technique. Their unique physical and chemical properties can be employed in various applications. Due to their high refractive index and a broad transmission band spanning the ultraviolet, visible and infrared bands, sapphire fibres are perfect waveguides in harsh environments. The current major applications are Er:YAG laser beam delivery and pyrometric and spectrometric measurements in furnaces, combustion engines, etc. In this paper we summarize an adjustment of the EFG method to grow thin filaments by giving possible molybdenum die designs. We investigated the fibres using an optical microscope and measured their transmission of an Er:YAG laser beam (2.94 µm). The attenuation of the tested samples is approximately 0.1 dB/cm.

Facet Appearance on the Lateral Face of Sapphire Single-Crystal Fibers during LHPG Growth

“…Facet appearance on the lateral surface of SC fibers was observed while using different growth techniques. At the same time different explanations were provided for SC fiber faceting: (1) influence of manufacturing accuracy of the shaper in µ-PD (micro-pulling-down) technique [13]; (2) seed misalignment [14]; (3) fluctuations of the pulling rate, heating temperature and feed velocity [12,15]. The modeling of the time-dependent behavior of SC fiber growth in an LHPG arrangement [15] demonstrates that the Marangoni convection in the LHPG melting zone could change the growth angle, leading to diameter fluctuations of the growing fiber and thereby to the chance of facet appearance.…”