One-dimensional Magnetophotonic Crystals Research Articles

Preparation of one-dimensional photonic crystals by sol–gel process for magneto-optical materials

One-dimensional photonic crystal (PC) of periodically alternating low (SiO 2) and high (TiO 2) refractive index materials was prepared by sol–gel dip coating method that controls the thickness of each layer with nanometer level. The photonic band gap of high reflectivity was verified at wavelengths between 590 nm and 820 nm, which became significant with increasing the number of bilayer. The UV–vis spectra, SEM image and glow discharge optical emission spectroscopy indicate the periodic structure of SiO 2/TiO 2 multilayer. The magnetic layer of CoFe 2O 4 was also prepared by a sol–gel dip coating method. After the annealing at 700 °C, the single phase of CoFe 2O 4 film with spinel structure, without any preferred crystalline orientation, was obtained. In addition, the one-dimensional magnetophotonic crystal (MPC), in which the magnetic defect layer of CoFe 2O 4 is introduced into the periodic structure, was prepared. The light was localized at the magnetic defect due to the interference of the multilayer film, and the localized transmittance was observed around 530 nm. The Faraday rotation of MPC shows a peak at ∼ 570 nm which is close to the localized peak of transmittance. This may correspond to the enhancement of Faraday rotation due to the localization of light.

Couplonic parameters of a 1D magneto-photonic crystal

In the frame of an exact (non-perturbative) formulation of the coupled-mode theory, we describe a one-dimensional multilayer magneto-photonic crystal with alternate dielectric and magneto-optical materials.

Optics of circularly polarized light waves in one-dimensional magneto-photonic crystals: Theory

A theory is presented for propagation of electromagnetic waves through one-dimensional magnetic Bragg structures (magneto-photonic crystals). Within the self-consistent Green-function technique the transfer matrices and magneto-optical characteristics are derived in terms of circularly polarized waves propagating in periodical arrays of alternating magnetic and dielectric layers. For finite-thickness magneto-photonic crystals, the Faraday rotation and other magneto-optical responses are demonstrated to change considerably in the spectral range of stop-bands, the magnetic modulation of the in-plane reflection intensity being essentially enhanced.

Magnetic photonic crystals: 1-D optimization and applications for the integrated optics devices

The optimization of multilayer one-dimensional (1-D) magnetophotonic crystals (MPCs) with multiple phase shifts, enabling their design to be tailored to practical photonics applications, is reported. The properties of sample optimized structures suitable for application in infrared intensity modulators are discussed. A novel scheme of high-resolution magnetic field sensing using MPCs is proposed. The effect of material absorption on spectral properties is shown.

Enhancement of the magnetorefractive effect in magnetophotonic crystals

The magnetorefractive effect in a one-dimensional magnetophotonic crystal, more specifically, a photonic crystal (SiO2/Ta2O5) containing a built-in defect in the form of a thin layer of the Co-(Al-O) magnetic nanocomposite, is studied in a computer simulation experiment. The structure of the unit cell of the photonic crystal in which most of the field energy is concentrated in cells nearest to the defect is determined. This makes it possible to increase the defect-mode Q factor and, owing to the multiple passage of light along the defect, to enhance the magnetorefractive effect by more than one order of magnitude as compared to a thin film on a substrate and by two orders of magnitude as compared to thick films. The reflectance of these structures in an applied magnetic field can be as high as 60%.

Limits of enhancement of the Faraday effect in ultra-thin magnetic layers by one-dimensional magnetophotonic crystals

The optimization of the linear, first-order, Faraday effect in absorbing, ultra-thin, magnetic films is considered both analytically and by numerical simulations. Enhancement using one-dimensional magnetophotonic crystals is considered in parallel with a discussion of the principles of enhancement through an appreciation of the optical resonances that occur in the Fabry–Perot etalon. Simple formulae are presented for the approximate upper limits of enhancement and the associated photometric parameters of the system that accompany optimal conditions. For a 1 nm thick cobalt layer the degree of enhancement is approximately a factor of 4 greater than can be achieved with a single layer. The validity of the formulations is confirmed by numerical simulations based on the use of cobalt as the magnetic medium.

Investigation of a one-dimensional magnetophotonic crystal for the study of ultrathin magnetic layer

We investigated one dimensional magnetophotonic crystals consisting of a cavity containing a magnetic layer between two Bragg reflectors. This structure can be made very efficient to obtain a localized mode with enhanced Faraday rotation. In this paper, the parameters of the magnetic layer (thickness and position within the cavity) were systematically varied in order to find theoretically the most efficient structure according to a figure-of-merit. A significant enhancement of the Faraday rotation, θF, by a factor of twelve is found compared with a single cobalt layer. Our calculations show the possibility of using this huge enhancement for ultrathin magnetic layer studies. The experimental spectrum of the ellipsometric parameter tan(Ψ) agrees with the calculated results.

MAGNETO-OPTIC SPATIAL LIGHT MODULATORS WITH ONE DIMENSIONAL MAGNETOPHOTONIC CRYSTALS

We have developed the magneto-optic spatial light modulator (MOSLM) with one-dimensional magnetophotonic crystal (1D-MPC). The multilayer structure of SiO2, Ta2O5, and bismuth substituted yttrium iron garnet (Bi:YIG) were deposited by the RF magnetron sputtering to form 1D-MPC. By using 1D-MPCs, The large enhancement in Faraday rotation was obtained in localized light mode, and the fabricated MOSLM showed higher contrast than that of single magnetic film. We confirmed the brightness of the magneto-optical image changed by an external magnetic field.

Enhancement of Faraday rotation at photonic-band-gap edge in garnet-based magnetophotonic crystals

Spectral dependences of Faraday rotation angle in one-dimensional garnet-based magnetophotonic crystals are considered. The enhancement of Faraday angle is demonstrated at the photonic band gap (PBG) edge both theoretically and experimentally. It is shown to be associated with the optical field localization in the magnetic layers of the structure. The advantages of magnetophotonic crystals in comparison with traditional magnetic microcavities are discussed. The specially designed microcavity structures optimized for the Faraday effect enhancement at the PBG edge are suggested.

Transverse Kerr effect in one-dimensional magnetophotonic crystals: Experiment and theory

Magneto-optical transverse Kerr and Faraday effects are studied experimentally and theoretically in one-dimensional magnetophotonic crystals fabricated from a stack of four repetitions of layers of Bi-substituted yttrium iron garnet and SiO 2 layers. The results of theoretical calculations in the framework of modified matrices approach are consistent with the obtained experimental data with the exception of the one cusp at 480 nm in the transverse Kerr effect spectra. Possible mechanisms of this disagreement are discussed.

Phase-Matched Magnetization-Induced Second-Harmonic Generation in Yttrium–Iron–Garnet Magnetophotonic Crystals

Magnetization-induced second-harmonic generation (MSHG) is studied in one-dimensional magnetophotonic crystals formed from a stack of ferromagnetic Bi-substituted yttrium-iron-garnet layers alternating with dielectric films. The resonance enhancement of reflected MSHG due to the phase-mismatch compensation is observed for longitudinal dc-magnetic-field application if the fundamental radiation is tuned across the photonic band gap edge. The high-contrast magnetization-induced variations in the second-harmonic intensity are obtained in transversal configuration of the nonlinear magnetooptical Kerr effect.

Coexistence of large Faraday rotation and high transmittance in magnetophotonic crystals with multi-cavity structures

Abstract Magneto-optical effects of one-dimensional magnetophotonic crystals composed of a Bi:YIG thin film and Ta 2 O 5 /SiO 2 multilayer film were theoretically investigated. The calculations revealed that the required optical isolator performance ( T >95% and θ F =45°) can be fulfilled when the periodic multilayer films have only two or three magnetic layers. This mechanism which satisfies the properties of an optical isolator can be thought of as a transmittance to improve; because the peak of one side piles up, though each of the circular polarizations of light has two peaks and a square bandpass.

Preparation of magnetophotonic crystals with ND-controlled EB-evaporation method and their large enhancement of Faraday effect

Abstract The potential of one-dimensional magnetophotonic crystals (1D MPCs) were investigated in theoretical and experimental studies. We prepared 1D MPC of (Ta 2 O 5 /SiO 2 ) 9 /Bi:YIG/(SiO 2 /Ta 2 O 5 ) 9 and (Si/SiO 2 ) 3 /Bi:YIG/(SiO 2 /Si) 3 utilizing the dielectric layer formed by using the ND-controlled EB evaporation method. We obtained basic magneto-optical properties that were in agreement with 1D MPC predicted theoretically. θ F of the multilayer structure was more than 150 times larger than that of a Bi:YIG single-layer film.

Magnetorefractive effect in magnetophotonic crystals

ABSTRACTThe magnetorefractive effect in one-dimensional magnetophotonic crystals was investigated at a wavelength of about 3 μm. It is shown that the magnitude of magnetorefractive effect can be increased to 10–15 times in comparison with one magnetic layer of the same thickness positioned on a metallic mirror.

Observation of Enhanced Faraday Effect in Garnet-Based Magnetophotonic Crystals

ABSTRACTThe fabrication of one-dimensional magnetophotonic crystals (MPC) composed from Bi-substituted yttrium-iron-garnet films separated by the silicon oxide layers is presented. The enhancement of the Faraday rotation angle is observed at the spectral regions of the photonic band gap edges. The effective Faraday rotation achieves the values up to 1.5 degrees per micron at 1100-nm-wavelength.

Behavior of Large Faraday Rotation in Magnetophotonic Crystals with Single-Cavity Structures

We fabricated one-dimensional magnetophotonic crystals (1-D MPCs, hereafter) with single-cavity structures of (Ta2O5/SiO2) k/Bi: YIG/(SiO2/Ta2O5) k (k=2, 6). Their fundamental optical and magneto-optical fundamental properties were investigated in detail. We obtained experimental results that were in good agreement with the theoretical predictions: the Faraday rotation angle of the medium was more than 100 times larger than that of a Bi: YIG single-layer film. In addition, we performed numerical calculations by taking the optical dissipation effect into account, and the experimental results were examined. The optical dissipation was found to be a key parameter in determining the performance of 1-D MPCs apparatus. The Bi: YIG and dielectric films were deposited under the preparation conditions shown in Tables 1 and 2. The design wavelength was 720nm. Optical and magneto-optical properties of the prepared 1-D MPCs were calculated theoretically by solving Maxwell's equations with the bigyrotropic dielectric tensor for the magnetic layers under the electromagnetic boundary conditions imposed at all discontinuous planes. This is usually rather tedious, but is easily achieved by means of the matrix approach.

Numerical Analysis of One-Dimensional Magnetophotonic Crystals with an Active Layer of a Highly Bi-Substituted Iron Garnet

The one-dimensional magnetophotonic crystals having a structure of (AB)kM(BA)k, where k is the number of stacking layer, M is Bi-substituted iron garnet with a Bi content of 0.5 and 1.07, and A and B are SiO2 and Ta2O5, respectively, were numerically simulated in the visible and near infrared wavelengths. The Faraday rotation angle, transmittance, and figure of merit, which was defined by T|sin 2θF|, of the one-dimensional magneto-photonic crystals (1D-MPCs) as a function of Bi content and the thickness of the magnetic garnet layer are presented. In the near infrared region, several hundred times larger Faraday rotation angle reaching 30–40 degrees and several ten times of figure of merit reaching 0.4–0.5 were obtained as compared to the garnet single layer. In particular, the figure of merit of the one-dimensional magnetophotonic crystals in the near infrared region was several times larger than that in the visible region.

One-dimensional magnetophotonic crystals with granular magnetic films

A one-dimensional magnetophotonic crystal (1D-MPC) with a granular magnetic film has a large Faraday rotation angle at a localized photonic state inside a photonic forbidden band gap. The great advantage of using the granular magnetic film is that a thermal annealing process is unnecessary, which is in contrast to a 1D-MPC with a Bi:YIG film. We describe that the improved performance of the 1D-MPC with the granular film is obtained without thermal annealing.

Theoretical analysis of optical and magneto-optical properties of one-dimensional magnetophotonic crystals

We present a procedure for analyzing the properties of multilayer structures with magnetic film. The magneto-optical effect in multilayer-structure magnetic films [e.g., bismuth-substituted yttrium iron garnet (YIG)] and dielectric films (e.g., SiO2 and Ta2O5) was investigated theoretically and experimentally to examine the correlation between the magneto-optical properties and the localization effect of light. The film structure of interest, which has symmetric periodicity, is the (Ta2O5/SiO2)n/Bi:YIG/(SiO2/Ta2O5)n structure, where n is the repetition number. We fabricated experimentally a one-dimensional magnetophotonic crystal film of (Ta2O5/SiO2)n/Bi:YIG/(SiO2/Ta2O5)n (n=2,6) structures. The theoretical calculation and the measured value for the Faraday rotation were in close agreement. Furthermore, the Faraday rotation of the multilayer structure with n=6 is 150 times larger than that of a Bi:YIG single-layer film. This is of interest from the point of view of actual magneto-optical device (e.g., optical isolator) fabrication.

Effect of optical losses on optical and magneto-optical properties of one-dimensional magnetophotonic crystals for use in optical isolator devices

One-dimensional magnetophotonic crystal (1-D MPC) film composed of thin rare-earth iron garnet, SiO 2 and Ta 2O 5 films simultaneously exhibits very high optical transmittance and Faraday rotation. We investigated the structure of 1-D MPC, which by theoretical calculation has an optical isolation performance favorable from an industrial perspective. Furthermore, we considered, theoretically, whether it could be used as an optical isolator if a film had absorption. As a result, the structure of 1-D MPC film with satisfactory optical isolation has an industrially favorable structure by using a high refractive index material such as Si. It was also found that if the optical absorption (extinction coefficient κ) of a film was less than 0.000001, it did not affect the characteristics. This makes it very attractive for actual optical isolator fabrications.