Formation of ceramic and crystal claddings for a Ti:sapphire crystalline fiber core

We describe the fabrication and characterization of single-mode Ti:sapphire crystalline fibers, cladded by dip coating and high-temperature sintering at 1750 o C. Solid-state single crystal growth was observed at the perimeter of the crystalline core, and the growth speed along ( 1 1 ¯ 0 ) is about 2.7 times faster than that of (001). The grown cladding was single-crystalline as evidenced by electron backscattered diffraction and scanning electron microscopy examinations. From optical transmission measurement at 1550 nm, the far-field distribution of the transmitted light matches well with that of the fundamental mode. With a core size of 30 µm, the refractive index difference between core and clad was measured to be 1.0 × 10 −4 . From fluorescence mapping on the fiber end face, a very limited amount of the Ti 3+ ions in core were diffused into the grown crystalline cladding during the solid-state growth.