TM-TE optical-mode conversion induced by a transversely propagating magnetostatic wave in a (BiLu)3Fe5O12 film

Abstract

Highly Bi‐substituted garnet films (BiLu)₃Fe₅O₁₂ (Bi=0.89/f.u.) have been grown on (111)‐oriented Gd₃Ga₅O₁₂ substrates by liquid‐phase epitaxy with only Bi₂O₃ as a flux. The specific Faraday rotation θ_F attains −0.14 deg/μm at 1.3 μm. Guided‐optical‐wave propagation loss of 0.6 dB/cm at 1.3 μm is obtained by doping an appropriate amount of MgO in the melt. Magnetostatic backward volume wave (MSBVW) is launched efficiently into the film as expected from the measured small ferromagnetic resonance linewidth of 0.7 Oe, whereas magnetostatic surface wave and magnetostatic forward volume wave are subject to the severe attenuation due to their coupling to spin‐wave modes. The interaction between guided optical wave and MSBVW is investigated in a transverse configuration where the input optical wave passes almost orthogonal to MSBVW. The TM‐TE optical‐mode conversion induced by MSBVW is observed over the frequency range of 3.5–7.5 GHz. Its efficiency, as high as 47%/0.8 W at 4 GHz, is obtained for the interaction length of 7 mm.