H. Takagi

Fabrication and characteristics of one-dimensional magnetophotonic crystals for magneto-optic spatial light phase modulators

We prepared the reflection type magnetophotonic crystals (R-MPC) to enhance the magneto-optic property of magneto-optic spatial light phase modulator (MOSLM). Magnetophotonic crystals have a localized wavelength by using a defect layer in which the magneto-optic property can be increased tremendously. By the calculation, it was revealed clearly that Kerr rotation can be enhanced with increasing the repetition number (k) which is the number of dielectric layer. In this study, Dy1.0Bi1.5Y1.0Fe3.8Al1.2O12 (DyBi:YIG) garnet material, of which Faraday rotation angle is about −3u2002deg/μm, was utilized as a defect layer. At the designed wavelength of 532 nm and k=5, SGGG/[SiO2/Ta2O5]2/DyBi:YIG/[SiO2/Ta2O5]k structure fabricated with garnet thickness of 347.6 nm showed Kerr rotation angle of 26° and reflectivity of 0.2% which is coincident considerably with the results (θk=30° and R=0.59%) calculated by the matrix approach method. The fabricated R-MPC-MOSLM structure exhibited the magneto-optic property of about 25...

Study on magnetophotonic crystals for use in reflection-type magneto-optical spatial light modulators

A magneto-optical spatial light modulator (MOSLM) is a real-time programmable device for modulating the amplitude and/or phase of two-dimensional optical signals at a high speed. Recently, we reported the development of the transmission-type MOSLM (T-MOSLM) based on a one-dimensional magnetophotonic crystal (MPC) with a high driving performance. However, further improvement of the T-MOSLM is required. The structure of the T-MOSLM has low optical efficiency due to weakening of transmittance through electrodes; furthermore, the fabrication of the driving electrodes is a very complicated process. In this study, we suggest a new design of the MPC for a reflection-type MOSLM (R-MOSLM). The idea of a reflection-type MPC (R-MPC) is to replace one of the Bragg mirrors with an aluminum reflection film. The structure is glass∕(Ta2O5∕SiO2)k∕Bi:YIG∕Al, where k is the repetition number. The approach of the optimal structure of the R-MPC was done by the calculation of the matrix approach method. In the calculation of t...

Novel magnetophotonic crystals controlled by the electro-optic effect for non-reciprocal high-speed modulators

We present a new type of electro- and magneto-optical spatial light modulators (e-MOSLMs) utilizing the concept of photonic crystals (PCs) – such e-MOSLMs have a microcavity structure. They comprise a magneto-optical (MO) and electro-optical (EO) constituents that can control the direction of the polarization plane, when applying voltage and/or external magnetic fields. Optical spectra of e-MOSLMs were analyzed by using the matrix approach. Calculations showed that e-MOSLMs can change the direction of polarization over a considerably large range of angles at relatively low power consumption and with no significant change of the light intensity.

Magnetic property of polycrystalline magnetic garnet for voltage driven type magneto-optic spatial light phase modulator

In this study, we investigated the magnetization response of the polycrystalline magnetic garnet film for stress. The calculation suggests that the balance of the magnetic anisotropic energy under magnetic field is an essential factor to modulate the magnetization by stress. We fabricated the magnetophotonic crystal based voltage driven type magneto-optic spatial light modulator, and measured the magneto-optic response for stress. The experimental results had a good agreement with our calculation. In our results, the magnitude and linearity of the modulation by stress was depending on static bias field, stress, and magnetostriction constant. The obtained results implied that the calculation could estimate the device performance by deciding material composition and prepare stress inside garnet.

Enhancement of modulation rate of magneto-optical spatial light modulators with magnetophotonic crystals

Thin-film-type magneto-optical spatial light modulator has been developed by combining one-dimensional magnetophotonic crystal (MPC) and micropatterned drive lines. The use of MPC is expected to be effective because the apparent Faraday effect, which is directly proportional to pixel contrast, is largely enhanced by the light localization of light in the vicinity of the magnetic defect in magnetophotonic crystal. The magnetophotonic crystal had a multilayer structure of (Ta2O5∕SiO2)k∕Bi: yttrium iron garnet∕(SiO2∕Ta2O5)k formed on a glass substrate, where k is the repetition number and one of optimization parameters in this study. The transmittance T decreased with an increase of k, while Faraday rotation θF increased, indicating that the enhancement of light modulation rate would be achieved by optimizing the figure of merit F defined by F≈Tsin2θF. At k=6, the maximum F=8.8 was obtained, which is about 20 times larger than that of single layer structure.

Preparation and Fundamental Properties of Magneto-Optic Analog Spatial Light Modulator with One Dimensional MagnetoPhotonic Crystals

This paper, for the first time, presents the preparation and fundamental properties of analog magneto-optic spatial light modulators (MOSLM) which is composed of one-dimensional (1D) magnetophotonic crystals (MPCs). The use of 1D-MPCs in MOSLM is very useful because large Faraday rotation angle of the medium can be obtained at a particular wavelength of light by designing the medium structure, which results in considerable improvement of optical contrast in MOSLM. Large enhancement in Faraday rotation (approximately 5 times large) was obtained for the localized mode of light, suggesting that the optical contrast of MOSLM can be enhanced considerably, although the garnet film thickness was very thin.