R. Fujikawa

Contribution of the surface plasmon resonance to optical and magneto-optical properties of a Bi:YIG-Au nanostructure

We have studied the optical and magneto-optical properties of bismuth-substituted yttrium iron garnet (Bi:YIG) films with Au nanoparticles dispersed on their top surfaces. These structures exhibit surface plasmon resonances due to light coupling to Au nanoparticles, showing, for any direction of polarization of the incoming light beam, an absorption band in the spectral range of 500–750nm. For transmitted light beams with the plasmon-resonant wavelengths, the plane of polarization rotates slightly when the structure is not magnetized. Polarization-resolved transmission spectra show that this rotation is due to anisotropy of light propagation through the array of Au nanoparticles. For the structure comprising the 90-nm-thick Bi:YIG film and the array of Au nanoparticles of several tens of nanometers, the Faraday rotation angle enhances as compared with that for the original Bi:YIG film of the same thickness.

Fabrication and Optical Properties of Three-Dimensional Magnetophotonic Heterostructures

The vertical deposition technique and the RF-magnetron sputtering method were employed for fabrication of three-dimensional (3-D) magnetophotonic crystals, in which a bismuth-substituted yttrium-iron-garnet planar defect layer was sandwiched in between two opal thin films. Optical properties and structure of constitutive elements (opal thin films) were studied in detail. An evolution of optical response of a magnetophotonic heterostructure under preparation is presented

Mesoporous photonic crystals for sensor applications

Optical properties of mesoporous three-dimensional photonic crystals (3D PCs) based on thin opal films were found to be extremely sensitive to a humidity of the surrounding air. It was manifested that the internal structure of a single SiO2 sphere together with the net of voids between them in a thin opal film acts as a sponge for wet steams. Our experimental data have shown that hydrophilic internal structure of a mesoporous film sponges up (and lose) water (dry or wet steams) that influences dielectric permittivity, the latter causes significant changes in transmission spectra. High sensitivity, quick response and possibility of contactless measurements makes sensors based on optical effects in mesoporous PCs to be very promising. It concerns not only humidity sensors, but also sensors of various gases, temperature, deformation and other environmental impacts.

Fabrication of Three-Dimensional Magnetophotonic Crystals: Opal Thin Films Filled with Bi:YIG

We have fabricated three-dimensional magnetophotonic crystals based on a-SiO₂ opal films. Opal thin films grown on glass substrates were filled with bismuth substituted iron garnet (Bi:YIG). Scanning electron microscopy data, optical and magnetic properties of the synthesized samples confirm the presence of the Bi:YIG content in the opal lattice. It is shown that the samples exhibit the (111) stop band, and transmissivity of the threedimensional magnetophotonic crystals is defined by both the film lattice and the Bi:YIG content.

Fabrication and magneto-optical responses of Au-Bi:YIG films

We have studied magneto-optical responses of gold-bismuth-substituted yttrium iron garnet (Au-Bi:YIG) composite films in which Au particles are embedded into Bi:YIG in two different ways. First type were samples in which planar arrays of Au particles were introduced into the middle of Bi:YIG films using a step-by-step sputtering technique. Second type were granular films fabricated using simultaneous co-sputtering of Au and Bi:YIG; in these films Au particles occupy positions inside composite films in a random way. Absorption bands associated with localized surface plasmon resonances (LSPRs) were observed in transmission spectra of films of both types. In the spectral range of LSPRs, samples of Au-array type exhibited larger Faraday rotation angles as compared with that for reference Bi:YIG films of the same thickness. However, given that the volume fraction of Au particles was nearly the same for both types, the enhancement of Faraday rotation for samples of Au-granular type was insignificantly altered. Experiments showed that of the primary importance is the role of the interfaces between Au particles and Bi:YIG. Theoretical estimations showed that, in samples of Au-granular type, air shells appeared between Au particles and Bi:YIG during fabrication. In fact, annealing needed for crystallization of Bi:YIG films is always accompanied with an expansion of their thicknesses.

Magneto-optical properties of three-dimensional photonic crystals with a planar magnetic defect

We present a new method for calculation of optical and magneto-optical properties of three-dimensional magnetophotonic crystal heterostructures, composed from a sequence of homogeneous plates of a magneto-optical material and photonic crystal slabs. The algorithm is based on the layer KKR technique. As examples we consider the Bi:YIG (bismuth-substituted yttrium-iron-garnet) magneto-optical plate sandwiched by photonic crystal slabs consists of (i) simple cubic/face centered cubic lattices of SiO2 spheres in the air; (ii) air spheres in silicon background (inverse opals). The enhanced Faraday rotation appears at the resonant transmission frequency in analogy with one-dimensional structures with magneto-optical microcavity. However, the calculated spectral behavior of the Faraday rotation as well as its dependence on defect thickness is quite different and unusual. For instance, the Faraday rotation angle changes its sign within the photonic band gap that is due to complicated reflection of waves from 3D photonic crystal slabs.

Analysis of Opal Template for Three Dimentional Magnetophotonic Crystals

Periodic structures of dielectric materials in submicrometer are currently paid much attention as photonic crystals (PC) with photonic band gap (PBG), which prohibits light of specific wavelength from propagating in certain directions. We reported one-dimensional magnetophotonic crystals (1D-MPCs) constructed of dielectric multi layers and a magnetic defect layer obtained large enhancement of Faraday rotation in localized mode. On the other hand, three-dimensional photonic crystals (3D-PCs) have more capability as the materials exhibit remarkable effects such as acute angle optical waveguides, super prism, and magnetophotonic crystals (MPCs). In order to control that unique effect by applying external magnetic field, fabrication of three-dimensional magnetophotonic crystals (3D-MPCs) with magnetic materials is required.

Fabrication of two dimensional magnetophotonic crystal by selective-area sputter epitaxy

This study demonstrates the fabrication of 2D magnetophotonic crystal (MPC) by selective-area sputter epitaxy (SASE) of iron-garnet film, (BiYDy)/sub 3/(FeAl)/sub 5/O/sub 12/ for the first time. This fabrication method overcomes the disadvantages associated with groove etching due to underetching and nonplanar surface topology.

Fabrication of 3D-magnetophotonic crystal with artificial opal template prepared by gravitational sedimentation

We report results on fabrication of three-dimensional (3D)-magnetophotonic crystals (MPCs) based on artificial opals. The opal samples composed of amorphous SiO/sub 2/ spheres were prepared using gravitational sedimentation. Quantitative evaluation of opal structure was done by fitting the (111) photonic bandgap by a Gaussian function. Changes in depth and width of the (111) photonic bandgap were observed after polishing less-ordered bottom side of the as-grown opal samples. To create 3D-MPCs, terbium gallium garnet was synthesized in an opal matrix.