Two-dimensional Magnetophotonic Crystals Research Articles

Development of 3mm three-port Y-junction magnetic optical circulator with two-dimensional magneto-photonic crystals

Two kinds of defect structures of two-dimensional (2D) magnetic-photonic crystal (MPCs) are envisaged to realize circulators in millimeter wave band. The band gaps of the two kinds of photonic crystals are calculated by the plane wave expansion method. The function of the circulator is simulated by finite element method. The calculated excellent external characteristics of the circulator show that MPCs is a promising way for generating an optical circulator.

Polarization research of YIG based two-dimensional Magneto Photonic Crystals

In this paper, the axial propagation of light in two-dimensional YIG based MPCs (Magnetic Photonic Crystals) was simulated by three dimensional FDTD (Finite Difference Time Domain) algorithm with Matlab and Rsoft tools. The effects of structure, filling rate of lattice, wavelength of incident light and the external magnetic field on polarization of the output light were discussed. According to the simulation, a specific structure with 25% filling rate, 1.2 μm wavelength and 2um lattice constant in the absence of defects in MPCs was validated as an ideal model to obtain a good magneto-optical response. When a central defect existed, the Faraday rotation angle increased and the ellipticity of polarization was suppressed to a certain extent for the broken periodicity of the original structure. The defect model can reach a rotation angle of 9.4 degrees, which is larger than the angle of 8.3 degrees of non-defect model when transmitting a distance of 0.5 μm under the condition of the same incident light wavelength of 1.2 μm and filling rate of 25%. A large Faraday rotation in short propagating distance was obtained when a certain polarization degree was maintained, which can be used in magneto-optical modulation devices.

Magneto-photonic crystal microcavities based on magnetic nanoparticles embedded in Silica matrix

Using the three-dimensional finite difference time domain method (3D FDTD) with perfectly matched layers (PML), optical and magneto-optical properties of two-dimensional magneto-photonic crystals micro-cavity is studied. This micro-cavity is fabricated by SiO2/ZrO2 or SiO2/TiO2 matrix doped with magnetic nanoparticles, in which the refractive index varied in the range of 1.51–1.58. We demonstrate that the Q factor for the designed cavity increases as the refractive index increases, and we find that the Q factor decreases as the volume fraction VF% due to off-diagonal elements increases. These magnetic microcavities may serve as a fundamental structure in a variety of ultra compact magneto photonic devices such as optical isolators, circulators and modulators in the future.

Low-loss Y-junction two-dimensional magneto-photonic crystals circulator using a ferrite cylinder

A new defect structure of two-dimensional magnetic-photonic crystal is given and a new three-port Y-junction circulator using a ferrite cylinder is proposed in this short paper. Based on the agreements between the resonance frequency of micro-cavity constructed by a point defect in the 2D triangular lattice photonic crystal with those numerical results of corresponding literatures, external characteristics of the circulator were calculated by the plane wave expansion method and finite element method. According to the scaling theory of Maxwell's equations, a 3cm Y-junction 2D MPCs circulator is developed by scaling the radius of the center ferrite cylinder. The results show that there is a significant improvement for insertion loss 0.062dB and isolation 26.2dB compared with those in literatures.

Microcavity properties of 2D photonic crystal made by silica matrix doped with magnetic nanoparticles

In this present paper, quality factor of two-dimensional magneto-photonic crystals microcavity fabricated by SiO2/ZrO2 or SiO2/TiO2 matrix doped with magnetic nanoparticles, in which the refractive index varied in the range of 1.51 to 1.58, has been investigated. Finite difference time domain method (3D FDTD) with perfectly matched layers (PML) was used to calculate the transmission spectrum. We demonstrate that the Q factor for the designed cavity increases as the refractive index increases, and found that the Q factor decreases as the volume fraction VF% increases. The obtained results are useful for better designs of magneto photonic crystal devices.

Superprism phenomenon in two-dimensional magnetophotonic crystals: Experiment and numerical simulation

Magneto-optical phenomena in quasi two-dimensional magnetophotonic crystals (Q-2D MPCs) have been investigated experimentally and numerically. Multiple Bragg diffraction was shown to be responsible for enhancement of the Faraday rotation and for alteration of its sign in spectra of experimental samples fabricated from bismuth-substituted yttrium iron garnet. It was shown that, for the magnetic superprism effect–control of the light propagation direction by the external magnetic, materials with much larger magneto-optical activity than that of experimental samples are necessary. Spectra obtained by numerical simulations were in a good agreement with experimental ones. Magnetic superprism effect was demonstrated for model samples and parameters necessary for alteration flow of light in quasi-2D MPCs were obtained.

Optical waveguide circulators based on two-dimensional magnetophotonic crystals: Numerical simulation for structure simplification and experimental verification

We demonstrate results of a numerical analysis on functionality of waveguide circulators working in the spectral range of optical communication. Studied circulators were silicon-based three-port waveguide splitters where working elements were slabs of two-dimensional magnetophotonic crystals (2D MPCs) with different structural parameters. An optimized circulator had a 2D MPC slab–hexagonal array of cylindrical air holes in silicon with a magneto-optical defect made of bismuth-substituted yttrium iron garnet and demonstrated an insertion loss of 9 dB and an isolation of 16 dB. If compared to circulators reported in Z. Wan and S. Fan [Appl. Phys. B 81, 369 (2005)], the studied circulators are attractive for realization due to the relative simplicity of their designs.

Multiple diffraction in two-dimensional magnetophotonic crystals fabricated by the autocloning method

Quasi-2D magnetophotonic crystals (MPCs) comprising bismuth-substituted yttrium iron garnet/silicon dioxide multilayers were fabricated on top of 1D structured substrates and evaluated. Optical and magneto-optical (MO) spectra showed that light coupling to the structure of these MPCs happened in multiple Bragg diffraction regimes, where a mixing of modes with resonant wavelengths occurred within MPCs and a demultiplexing phenomenon was observed. Responses from the crystals were studied in transmission and diffraction geometries. We show that nano-scale tailoring of MPCs’ structure allows one to increase significantly the MO efficiency of magnetic materials and invert their natural MO responses.

Artificial Periodic Magnetic Structures for Photonic and High Frequency Micro-magnetic Devices

Magnetophotonic crystals and magnonic crystals having periodic structures formed band gaps by interference of waves. A one-dimensional magnetophotonic crystal (1D-MPC), which exhibits optical Tamm state at the interface between magnetic and nonmagnetic photonic crystals (PCs), shows resonant transmissivity and large enhancement of Faraday rotation at the localized mode inside the photonic band gap. We developed two-dimensional magnetophotonic crystals (2D-MPCs) on various types of templates with periodical structures. A 2D-MPC with multi-layers formed on a periodic 1D line resist template has several photonic band gaps with enhanced magneto-optical (MO) effects. In a structural garnet film formed on the opal template, a significant enhancement of MO response was obtained at edges of band gaps. Magnonic crystal with Cu metal strips formed on YIG surface showed high sensitivity of 11400 %/Oe as a magnetic sensor. In addition, enhanced MO effect was demonstrated by plasmonic composite films with noble metal particles and magnetic garnet.

Wafer-scale fabrication of magneto-photonic structures in Bismuth Iron Garnet thin film

In this paper we report on a reproducible technological process for wafer-scale fabrication of different photonic structures in Bismuth Iron Garnet (BIG: Bi 3Fe 5O 12) thin films: two-dimensional magneto-photonic crystals (PhC), ring circulators, Bragg gratings or ridge waveguides. Different fabrication techniques such as Ion Beam Etching (IBE), Focused Ion Beam (FIB) etching, wet chemical etching and Reactive Ion etching are compared. The transfer of different geometries in BIG is obtained with good etching verticality and conservation of the dimensions using Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE). This work demonstrates the possibility of wafer-scale high-quality nanostructuration of crystalline garnet thin films for magneto-photonic devices.

Theory of two-dimensional magneto-photonic crystals using complex Fourier factorization

The plane wave expansion method for calculating magneto-photonic crystals (MPCs) is modified via complex Fourier factorization whose basic principles are briefly explained. The new approach is used to simulate the photonic band structure of a two-dimensional MPC made as Bi:YIG rods arranged with square periodicity. The considerable improvement of the convergence properties is demonstrated for selected points of the bands.

Unidirectional band gaps in uniformly magnetized two-dimensional magnetophotonic crystals

By exploiting the concepts of magnetic group theory we show how unidirectional behavior can be obtained in two-dimensional magneto-photonic crystals (MOPhC) with uniform magnetization. This group theory approach generalizes all previous investigations of one-way MOPhCs including those based on the use of antiparallel magnetic domains in the elementary crystal cell. Here, the theoretical approach is illustrated for one MOPhC example where unidirectional behavior is obtained by appropriately lowering the geometrical symmetry of the elementary motifs. One-way transmission is numerically demonstrated for a photonic crystal slice.

Numerical analysis of two-dimensional magnetophotonic crystals with structural defects

The Faraday rotation of two-dimensional magnetophotonic crystals （including those with fourfold-symmetry and non-fourfold-symmetry） with structural defects and the ellipticity of outgoing optical waves are analyzed by using finite-difference frequency-domain （FDFD） method. The numerical simulation results show that the localization of the light wave in the vicinity of central defect occurs in these types of the structure. With increasing Faraday rotation of fourfold-symmetry structures, the change of the ellipticity of outgoing optical waves from these structures is unobvious. In contrast, the increases of the ellipticity of outgoing optical waves are obvious with the raise of Faraday rotation in non-fourfold-symmetry structures. It is concluded that introducing defects to the fourfold-symmetry structure constrains the change of the state of polarization of optical waves. This kind of two-dimensional magnetophotonic crystal with structural defects may be used to manufacture magnetophotonic crystal fiber.

Two-dimensional magnetophotonic crystals and analysis of the mode field

The mode field and effective index of two structures (square air core and circular air core) of two-dimensional magnetophotonic crystals is analyzed using finite-difference frequency-domain (FDFD) method. According to the result of numerical analysis, the two degenerate fundamental modes become non-degenerate (L-mode and R-mode) in the structures, and the two corresponding effective indices are different. The Faraday rotation of these two structures is enhanced compared with that of the continuous magneto-optical materials. By choosing proper parameters of the air core, the Faraday rotation can be increased by one order for the square air core structure and 4 times for the circular core structure. The polarization state of optical waves is changed after passing through the structure. With the increasing of Faraday rotation, the ellipticity of outgoing optical waves is increased. Finally, we discuss the cause of the phenomena and present a method to resolve the problem of variation of ellipticity by introducing defect in the structure.

The Faraday effect in two-dimensional magneto-photonic crystals

The necessary conditions for the observation of the Faraday effect in 2D magneto-photonic crystals are discussed. It is found. that the Faraday effect may be observed in the directions where any couple of the wave vectors of the harmonics consisting the Bloch waves of TE and TM solutions in zero magnetic field are identical. This direction corresponds neither to Faraday nor to Voigt geometry.