Growth of multifunctional electro-optic Yb:LiNbO3 crystalline fibers by laser heated pedestal growth (LHPG) method

In this paper, we report the growth of ytterbium-doped lithium niobate (Yb:LiNbO₃) crystalline fibers by laser heated pedestal growth (LHPG) method. In the growth, first, a Yb:LiNbO₃ bulk crystal is grown by melting the Yb:LiNbO₃ powder in a platinum (Pt) crucible at 1300 °C. Second, a Yb:LiNbO₃ bulk crystal is cut/lapped/polished in a rectangularly shaped bar, which can serve as the feed rod of LHPG. Finally, a Yb:LiNbO₃ fiber is drawn using the LHPG method, in which the Yb:LiNbO₃ bar is served as the feed rod, and a pure LiNbO₃ crystal bar is served as the seed rod. The major properties of the Yb:LiNbO₃ fiber are evaluated, including (1) identifying the composition of the fiber by energy dispersive spectroscopy (EDS), (2) determining the crystalline structure by X-ray diffraction (XRD), and (3) measuring the absorption spectrum by a spectrophotometer. The results of characterization experiments confirm that the grown fiber is indeed Yb:LiNbO₃ crystalline fiber. This unique crystalline fiber has multifunctional capability, including (1) a very effective low quantum defect lasing medium; (2) an electro-optically tunable medium, in which the refractive index of medium can be quickly tuned by the applied external electric field; and (3) a light guiding medium that offers the advantage of low driving voltage and power. The multifunctional capability of this crystalline fiber makes it very useful for a variety of applications such as highly compact, high-efficiency tunable lasers and filters.