Reducing the optical absorption of LPE garnet films at a wavelength of around 1000 nm

This paper concerns the reduction of optical absorption loss L of Bi-substituted rare-earth iron garnet films at a wavelength of around 1000 nm for use as a 45° Faraday rotator of an optical isolator. First, a single crystal of Nd_1.21Gd_1.74Sc_2.07 Ga_2.98O₁₂, with a lattice constant of 1.2619 nm, was grown by the Czochralski method. Using this crystal as a substrate, Nd_1.69Bi_1.31Fe₅O₁₂ film was grown by the LPE (Liquid Phase Epitaxial) method. The resultant LPE film showed a reduced optical absorption at around 1000 nm, because its optical absorption peak at around 900 nm due to the Fe³⁺ crystal field transition from ⁸A_1g to ⁴T_1g shifted toward short wavelengths. In addition, the LPE film´s Faraday rotation coefficient increased, since Nd, as Bi does, contributes negatively to the Faraday rotation. The value of L for the LPE film was found to be 2.6 dB at a wavelength of 980 nm, and 1.0 dB at 1017 nm