Optical and Magnetooptical Effects of Epitaxial Grown Ce:YIG/YAG

Magnetooptical effects can be applied to many dynamic optical/photonic applications, e.g., spatial light modulator [1] and optical Q-switch [2]. In these devices, the magnetooptical and light-emitting parts are usually separated. For instance, the magnetic film is separately placed in front of/behind the light sources. In these optical systems, all optical elements need to be aligned carefully to minimize the optical loss, preventing from miniaturization of the device and increasing the fabrication cost. Hence, integrating all-optical components into one chip provides a large advantage for developing optical applications. To demonstrate such an integration, we fabricated the cerium-substituted yttrium iron garnet (Ce:YIG) film on the yttrium aluminum garnet (YAG) substrate. Ce:YIG is widely known as a magnetooptical film showing a large Faraday rotation at the near-infrared wavelengths [3,4]. YAG doped with Nd is widely used as solid-state laser material. The Ce:YIG film was hetero epitaxially grown on YAG substrate using radio frequency ion beam sputtering. The Ce:YIG films were deposited onto double-side polished and (111) oriented YAG substrate. The temperature of the substrate was held at 850°C using the heater. The substrate size is 10 mm by 10 mm. The thickness of the grown film was about 2 micrometers.<br/>The x-ray diffraction peakｓ at (444) and (888) were observed, and other peaks were not, showing a single crystalline garnet phase. The reciprocal space map of the Ce:YIG/YAG sample showed a relaxed crystalline state. The magnetic properties measured by vibrating sample magnetometer (VSM) showed a magnetization of 91 emu/cc. The Faraday rotation loop was measured using a magnetooptical measurement system at a wavelength of 1064 nm. The Faraday rotation angle of -0.94°/µm was obtained. The remanent and coercivity of Faraday rotation angle were 0.09°/µm and 125 Oe. Therefore, these results showed the first integration of Ce:YIG on YAG substrate as an important milestone in developing magnetooptical elements combined with a light emitting system.<br/><br/>[1] H. Takagi, K. Nakamura, T. Goto, P. B. Lim, and M. Inoue, "Magneto-optic spatial light modulator with submicron-size magnetic pixels for wide-viewing-angle holographic displays," Optics Letters, 39, 3344-3347 (2014).<br/>[2] T. Goto, R. Morimoto, J. W. Pritchard, M. Mina, H. Takagi, Y. Nakamura, P. B. Lim, T. Taira, and M. Inoue, "Magneto-optical Q-switching using magnetic garnet film with micromagnetic domains," Optics Express, 24, 17635-17643 (2016).<br/>[3] Y. Yoshihara, T. Sugita, P. B. Lim, Y. Tamba, H. Inoue, K. Ishiyama, M. Inoue, C. A. Ross, and T. Goto, "Thickness-dependent magnetooptical properties of ion beam sputtered polycrystalline Ce₁Y₂Fe₅O₁₂ films," Optical Materials, (in press).<br/>[4] T. Goto, M.C. Onbasli, D.H. Kim, V. Singh, M. Inoue, L.C. Kimerling, C.A. Ross, "A nonreciprocal racetrack resonator based on vacuum-annealed magnetooptical cerium-substituted yttrium iron garnet," Optics Express, 22, 19047-19054, (2014).