Abstract: Sol-gel methods, apparatus and compositions for cladding optical fiber cores provide optical fibers, including single crystal optical fiber cores with polycrystalline cladding, having improved performance in a variety of applications, such as fiber lasers.

Abstract: Disclosed are apparatuses and methods for growing thin crystal fibers via optical heating. The apparatuses may include and the methods may employ a source of optical energy for heating a source material to form a molten zone of melted source material, an upper fiber guide for pulling a growing crystal fiber along a defined translational axis away from the molten zone, and a lower feed guide for pushing additional source material along a defined translational axis towards the molten zone. For certain such apparatuses and the methods that employ them, the lower feed guide's translational axis and upper fiber guide's translational axis are substantially aligned vertically and axially so as to horizontally locate the source material in the path of optical energy emitted from the optical energy source, in some cases to within a horizontal tolerance of about 5 ?m.