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

Abstract

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/spl deg/ Faraday rotator of an optical isolator. First, a single crystal of Nd/sub 1.21/Gd/sub 1.74/Sc/sub 2.07/Ga/sub 2.98/O/sub 12/, with a lattice constant of 1.2619 nm, was grown by the Czochralski method. Using this crystal as a substrate, Nd/sub 1.69/Bi/sub 1.31/Fe/sub 5/O/sub 12/ 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 Fe/sup 3+/ crystal field transition from /sup 8/A/sub 1g/ to /sup 4/T/sub 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.