Ytterbium continues to play an important role in the advancement of optical fibers and semiconductor thin film devices. The output power of fiber lasers has advanced due mainly to the design and fabrication of Ytterbium doped fibers. Yb-doped silica fibers are the preferred choice for gain medium in high power sources due to their high threshold for optical damage, high glass stability, low optical losses, easy thermal management and high optical efficiencies.1 Yb-doped fibers are typically prepared by a combination of Modified Chemical Vapor Deposition (MCVD) and a solution doping technique. This process has become time consuming and expensive to make more complex core structures that require several core layer depositions. The next generation of laser fibers will require more control of doping concentration and uniformity while still maintaining low background losses.
Thin films of Ytterbium oxide, Yb2O3, have been successfully grown onto silicon and glass substrates by Atomic Layer Deposition (ALD) for use as oxide dielectrics in semiconductor devices.2 This same ALD technique can be combined with MCVD for fabricating large mode area Yb-doped fibers. It is reported that a MCVD soot-preform with a porous layer of SiO2 has been successfully coated with Yb2O3 and Al2O3 using the ALD method. The precursors used were Yb(thd)3 and ozone. The Yb-doped fiber fabricated by this technique showed that the dopants successfully penetrated the full thickness of the soot layer, showed a background attenuation of 20dB/km, demonstrated a uniform longitudinal Yb-doping profile and good laser characteristics with a slope efficiency of 80%.3 The MCVD-ALD fiber also appeared to be more photodarkening resistant. An integrated ALD-MCVD manufacturing process can potentially allow several core layer deposition/doping cycles without the need to remove the preform from the MCVD system which in turn would enable accurate in-situ doping with significantly reduced fabrication time.
The precursor Yb(thd)3, Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)ytterbium(III), 99%, is available from Strem as product #70-0100. Strem also offers a new alternative amidinate based Ytterbium precursor for the ALD growth of oxide films and the doping of optical fibers, Tris(N,N’-di-i-propylacetamidinato)ytterbium(III), 99%, product #70-1000. Amidinate precursors in general have good volatility and reactivity and are thermally stable making them ideal candidates for ALD and CVD processes.
Product #70-0100, Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)ytterbium(III), 99% :
Product #70-1000, Tris(N,N’-di-i-propylacetamidinato)ytterbium(III), 99%:
CVD/ALD Precursors contained in Swagelok® Cylinders
Cylinder and Adaptors
High Purity Precursors for CVD/ALD
Metal Amidinates for CVD/ALD Applications
MOCD, CVD & ALD Precursors
PURATREM High Purity Inorganics
Stainless Steel Bubblers: Vertical Electropolished