Atomic layer deposition for fabrication of ytterbium doped fibers

Atomic layer deposition (ALD) was used to fabricate an ytterbium (Yb)-doped silica fiber in combination with the conventional modified chemical vapor deposition (MCVD) method. An MCVD soot-preform with a porous layer of SiO2 doped with GeO2 was coated with layers of Yb2O3 and Al2O3 prior to sintering, using the ALD method. ALD is a surface controlled CVD-type process enabling thin film deposition over large substrates with good thickness control, uniformity and high conformality. A materials analysis study showed that the dopants successfully penetrated the full thickness of 320 mu m of the soot layer. Preliminary preform and fiber experiments on refractive index profiles, background losses, lifetime and the characteristic gain-loss curve were performed demonstrating the potential of this method for fabricating Yb-doped fibers with high concentration of dopants.