Magnetophotonic crystals (MPCs) comprising cerium-substituted yttrium iron garnet (CeYIG) sandwiched by two Bragg mirrors were fabricated by vacuum annealing. CeYIG was deposited on Bragg mirrors at room temperature and annealed in 5 Pa of residual air. No ceria or other non-garnet phases were detected. Cerium 3 + ions substituted on the yttrium sites and no cerium 4 + ions were found. The Faraday rotation angle of the MPC was -2.92° at a wavelength of λ = 1570 nm was 30 times larger than that of the CeYIG film. These results showed good agreement with calculated values derived using a matrix approach.
Holographic memory is expected to become a high-capacity data storage. Magnetic volumetric holograms are rewritable holograms that are recorded as magnetization directions through thermomagnetic recording. However, the effective depth of magnetic holograms is limited by thermal diffusion that causes merging of magnetic fringes. In this study, we propose the insertion of heat-sink layers (HSLs) for retaining well-defined magnetic fringes during volumetric writing. Magnetophotonic microcavity media were used for demonstrating the HSL effect, and the structural design principle was established in numerical calculations. The results indicate that deep and clear magnetic fringes and an improvement in the diffraction efficiency can be achieved by the insertion of HSLs.
Hologram memory is a candidate for high-capacity data storage. Magnetic holograms formed as magnetization directions have been studied to realize rewritable hologram media. Recently, we reported that the magnetophotonic microcavity (MPM) can improve diffraction efficiency because of enhanced Faraday rotation angle and deep hologram writing. In this study, we demonstrated a clear reconstructed image from magnetic holograms in an MPM medium. The structural condition of MPMs for high diffraction efficiency was investigated, and the MPM medium was actually fabricated. The image reconstructed from the MPM medium had approximately twice the brightness of that reconstructed using a monolayer film.
Hologram memory is a promising data storage technology with a high recording density and fast data-transfer rate. Magnetic garnet media such as Bi1.3Dy0.85Y0.85Fe3.8Al1.2O12 (substituted rare-earth iron garnet, SRIG) films have advantages of rewritability and unnecessity of shielding. The diffraction efficiency of these garnet films, however, is not sufficient to apply to storage devices. In this paper, we proposed a use of magnetophotonic crystals (MPC) as hologram media and calculated their diffraction efficiency. The results indicated that MPC media showed a high diffraction efficiency compared with single SRIG films, and especially the MPC medium with the structure of substituted gadolinium gallium garnet substrate / (Ta2O5 / SiO2) 2 / SRIG / (SiO2 / Ta2O5) 2 with the SRIG thickness of 3.88 m exhibited the diffraction efficiency of 0.36%. A large Faraday rotation angle and deep magnetic hologram fringe originated from the localization of light results in such a high diffraction efficiency.
We report on microcavities comprising para-magnetic garnet and electro-optic films (MPMEO) for modulation of the polarization rotation angle of light at near-UV wavelengths with a slight intensity change, with applying a low voltage. The MPMEO are composed of para-magnetic garnet and electro-optic films sandwiched between two Bragg mirrors. The microcavity states in MPMEO are split and yield both the large rotation angle and high optical efficiency. Significant enhancement and modulation by applied voltages are verified through a conventional matrix calculation approach. High optical efficiency (>90%) and large modulation (~90 degree) of the polarization rotation are proved.
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