Temperature Dependence Free Magneto-Optical (Tb,Bi)Fe Garnet Films Grown By LPE Method
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Temperature Dependence Free Magneto-Optical (Tb,Bi)Fe Garnet Films Grown By LPE Method Nobuo Imaizumi1, Takashi Fukuhara1, Yasuhiko Kuwano2 and Kenichi Shiroki1 1 Namiki Precision Jewel Co., Ltd. 3-8-22 Shinden, Adachi-ku, Tokyo 123-8511, Japan 2 Dai-Ichi Kiden Co., Ltd. 1-54-1 Shimo-Ishihara, Chofu, Tokyo, 182-0035, Japan ABSTRACT Bi-substituted TbFe Garnet films grown by Liquid-Phase Epitaxial (LPE) method are demonstrated as a candidate for the temperature dependence free Faraday rotator in the telecom devices or the optical sensors applications. Several types of substituted GdGaGarnet (SGGG) substrates are applied in the tests. At X=0.48 ∼0.56 in the Tb(3-X)BiXFe5O12 , a series of very low temperature dependence garnet films are fabricated on the lattice constant of 12.465Å (GdCa)3(GaZrMg)5O12 substrates through the LPE-grown processing with optimized flux compositions. A couple of device applications are also demonstrated using these suppressed temperature dependence garnet films. INTRODUCTION It has been well known that Tb3Fe5O12 and Bi3Fe5O12 show opposite sign in temperature characteristics of the Faraday rotationθFR and the combined solid solution of (Tb,Bi)3Fe5O12 has been expected theoretically to form the temperature dependence free (TDF) magneto-optical garnet crystals by controlling the composition X in the chemical formula Tb(3-X) BiX Fe5 O12. In experimental, several authors reported the TDF Faraday rotator (FR) made by (Tb,Bi)3Fe5O12 for practical applications[1-5]. Tamaki et al. investigated the bulk garnet crystals of Tb(3-X) BiXFe5O12 grown by a flux method with an almost zero temperature coefficient of the Faraday rotation ⊿ θ FR,T, with X=0.46 at 1310nm and X=0.33 at 1550nm, respectively[3]. Honda et al. also reported the possibility of the zero ⊿θFR,T, by the LPE grown method with the same chemical system. They indicated that a relatively low Bi content suppressed theθFR and required a critical thick LPE-grown film over 1500μm for optical isolator applications wavelength at 1550nm for example, which induced the degradation of the crystal uniformity and the optical transparency[1]. In recent years, the above mentioned TDF-FR chips are recognized anew and are become a matter of great importance by the following reasons; several types of high-power laser light sources have been available wavelengths at 1310 or 1550nm, the insertion loss of the materials seems to be not so serious issue, a lot of un-cool transmission systems in the telecom- networks are required the TDF optical isolators for decreasing the total cost of the networks and the newly developed optical current transducer (OCT) composed with a photo-elastic flint-glass fiber (PEFG) as a FR sensing head together with a 22.5deg FR-chip made by a LPEgrown garnet crystal as a bias FR element invented by Kurosawa et al.[6] are also required the TDF magnetooptical FR-chip for the bias FR element owing to a improvement on the relative error of the sensor system. In the present report, the precise relation between Bi concentration of th
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