Study on the core/cladding interface in Cr: YAG double-clad crystal fibers grown by the codrawing laser-heated pedestal growth method

This study reports, for the first time, atomic-scale high-resolution transmission electron microscope (HRTEM) microstructure studies on the interface between the crystal core and polycrystalline inner cladding and strain relaxation mechanism of high-quality Cr:YAG double-clad crystal fibers grown by a codrawing laser-heated pedestal growth method. HRTEM analysis indicates that the core has high crystallinity and a sharp core/inner-cladding interface, exhibiting coherent planes with a preferred orientation relationship to the γ-Al2 O3 nanocrystals in the inner cladding. The slightly distorted γ -Al2 O3 lattice facilitates the release of residual strain, and eliminates misfit dislocation at the interface. Lattice strain analysis and image processing reveal a ∼18.2 nm layer near the interface for strain relaxation. © 2010 American Institute of Physics.