Annealing effects on growth-induced optical birefringence in liquid-phase-epitaxial-grown Bi-substituted iron garnet films

Optical birefringence in liquid-phase-epitaxial-grown (LPE) Bi-substituted iron garnet films was investigated with annealing. The optical birefringence was found to be composed of a stress-induced part and a growth-induced part. The growth-induced optical birefringence Δng was about 5×10−4 at λ=1.15 μm. Δng and the growth-induced magnetic anisotropy Kg disappeared after the annealing. Time constants for changes of Δng and Kg by the annealing were nearly the same and orders of a few hours at 1100–1150 °C. A deformation of the microscopic structure around bismuth ions seems to be responsible for both Δng and Kg. The large growth-induced optical birefringence in Bi-substituted iron garnet films plays an important role to achieve high efficiency TE-TM mode conversion in magneto-optical waveguides.