Alexander M. Grishin

Enhanced Faraday rotation in all-garnet magneto-optical photonic crystal

Research on magneto-optical photonic crystals has so far been focused on theoretical investigations, because suitable multilayers of iron garnet, the most promising material, have not been readily available. We report the preparation and characterization of a one-dimensional magneto-optical photonic crystal composed of 17 heteroepitaxial layers of bismuth iron garnet and yttrium iron garnet. The magneto-optical Faraday rotation was increased by 140% while transmission decreased by just 16% at the design wavelength of 750 nm as compared with a single-layer bismuth iron garnet film of equivalent thickness. The sample is free of cracks, and good agreement of simulated and experimental spectra of optical transmission and Faraday rotation indicate high quality of the sample and robustness of the preparation technique.

Background oxygen effects on pulsed laser deposited Na0.5K0.5NbO3 films: From superparaelectric state to ferroelectricity

Ambient oxygen pressure in a pulsed laser deposition process has been observed to have a critical influence on the compositional, crystalline, and electrical properties of Na0.5K0.5NbO3 (NKN) thin films grown onto polycrystalline Pt80Ir20 and SiO2 (native oxide)/Si(111) substrates. Films prepared at high oxygen pressure (∼400 mTorr) were found to be single phase and highly c-axis oriented. X-ray diffraction θ–2θ scans and rocking curve data show a strong effect of NKN film self-assembling along the [001] direction regardless of the substrate texture. The high dielectric permittivity of 550, low dissipation factor of less than 3%, and high remanent polarization of 12 μC/cm2 indicate the high ferroelectric quality of the fabricated film. The role of the high-energy component of the erosion products has been proven to be crucial to film performance. On the other hand, films grown at low oxygen pressure (∼10 mTorr) have been found to be mixed phases of ferroelectric NKN and paraelectric potassium niobates. Th...

Epitaxial Bi3Fe5O12(001) films grown by pulsed laser deposition and reactive ion beam sputtering techniques

We report on processing and comparative characterization of epitaxial Bi3Fe5O12 (BIG) films grown onto Gd-3(ScGa)(5)O-12[GSGG,(001)] single crystal using pulsed laser deposition (PLD) and reactive ...

Plasmon-mediated magneto-optical transparency

Magnetic field control of light is among the most intriguing methods for modulation of light intensity and polarization on sub-nanosecond timescales. The implementation in nanostructured hybrid materials provides a remarkable increase of magneto-optical effects. However, so far only the enhancement of already known effects has been demonstrated in such materials. Here we postulate a novel magneto-optical phenomenon that originates solely from suitably designed nanostructured metal-dielectric material, the so-called magneto-plasmonic crystal. In this material, an incident light excites coupled plasmonic oscillations and a waveguide mode. An in-plane magnetic field allows excitation of an orthogonally polarized waveguide mode that modifies optical spectrum of the magneto-plasmonic crystal and increases its transparency. The experimentally achieved light intensity modulation reaches 24%. As the effect can potentially exceed 100%, it may have great importance for applied nanophotonics. Further, the effect allows manipulating and exciting waveguide modes by a magnetic field and light of proper polarization.

Tailoring the colossal magnetoresistivity: La0.7(Pb0.63Sr0.37)0.3MnO3 thin-film uncooled bolometer

Epitaxial Ca, Sr, and Pb doped manganite films of various compositions and thickness have been prepared to tailor metal-to-semiconductor phase transition to room temperature. Continuous series of solid solutions La0.7(Pb1−xSrx)0.3MnO3 grown by the pulsed laser deposition technique were found to possess superior performance regarding the maximum of temperature coefficient of resistivity (TCR) @300 K. In these films phase transition temperature Tc ranges from 266 to 327 K. We have engineered the film of the optimum composition x=0.37 exhibiting the maximum of TCR=7.4% K−1 @295 K. Relatively low excess noise (normalized value γ/n of 3×10−21 cm3) has been achieved due to the epitaxial quality of the fabricated film. Using this film, infrared radiation bolometer demonstrator, operating at room temperature, has been built and tested. The bolometer resolves the noise equivalent temperature difference as low as 120 nK/Hz and shows signal-to-noise ratio SNR=8×106 Hz/K, responsivity R=0.6 V/W, detectivity D=0.9×107...

Epitaxial colossal magnetoresistive La0.67(Sr,Ca)0.33MnO3 films on Si

La0.67(Sr,Ca)0.33MnO3 (LSCMO) films have been grown by a pulsed-laser deposition technique on Si(001) substrates buffered with Bi4Ti3O12/CeO2/yttrium-stabilized zirconia (YSZ) heteroepitaxial layers. X-ray diffraction has revealed cube-on-cube growth of an epitaxial Bi4Ti3O12/CeO2/YSZ/Si heterostructure whereas the LSCMO layer grows in the “diagonal-on-side” manner on top of the Bi4Ti3O12 (BTO) template. The maximum temperature coefficient of resistivity (TCR)=4.4% K−1 and colossal magnetoresistance (CMR) Δρ/ρ∼2.9% kOe−1 have been reached at 294 K. This was achieved due to the successive improvement of c-axis orientation of the layers: Full widths at half-maximum 0.65°, 0.58°, 0.65°, 1.13°, and 0.18° in LSCMO/BTO/CeO2/YSZ/Si stack, respectively. As a prototype of an uncooled bolometer, heteroepitaxial CMR structure on Si demonstrates, at 294 K, the noise equivalent temperature difference of 1.2 μK/√Hz@30 Hz.

Colossal magnetoresistance in ultrathin epitaxial La0.75Sr0.25MnO3 films

We present results on magnetotransport measurements of a series of La0.75Sr0.25MnO3 films with thickness ranging from 32 to 3300 A. Films were fabricated using pulsed laser deposition onto SrTiO3 and LaAlO3 substrates. The substrate-film lattice mismatch causes strain in ultrathin films which diminishes with increasing thickness. Ultrathin films exhibit perfect match of in-plane film and substrate lattice parameters. The inhomogeneity of lattice parameters in thick films is caused by film-substrate mismatch strain and displayed by nonuniform broadening of x-ray diffraction Bragg reflections. The observation of characteristic Kiessig fringes is evidence for very uniform thickness of fabricated films. We found that the magnetotransport properties are strongly controlled by the film thickness and that allowed us to tailor the temperature of the metal-to-semiconductor phase transition in the range of 100–340 K with a change in magnetoresistivity within a factor of 3. We also present comparisons between the th...

Submicron Y3Fe5O12 Film Magnetostatic Wave Band Pass Filters

Thin Y3Fe5O12 (YIG) films were pulsed laser deposited onto Gd3Ga5O12 (111) and (001) substrates. Processing conditions were optimized to obtain compressively strained films with a ferromagnetic res ...

[Bi3Fe5O12∕Gd3Ga5O12]m magneto-optical photonic crystals

A series of one-dimensional heteroepitaxial all-garnet magneto-optical photonic crystals has been synthesized and optically characterized. They are composed of alternating magneto-optically active Bi3Fe5O12 (BIG) and Gd3Ga5O12 (GGG) quarter-wave length layers pulsed laser deposited on to the GGG(001) substrate. Photonic crystals, as designed, exhibit stop band structure and the band gap with the transmittance central peak caused by the light localization in the half-wave length BIG cavity. Compared to previously reported [Bi3Fe5O12∕Y3Fe5O12]m photonic crystal [Appl. Phys. Lett. 84, 1438 (2004)], the replacement of optically dense Y3Fe5O12 garnet by transparent Gd3Ga5O12 enables significant enhancement of light rejection within the stop band. Photonic crystals spectra experience “blue” shift in oblique incidence geometry thus demonstrating feasibility to use this effect for tunable magneto-optical filters.

Optical waveguiding in magnetron-sputtered Na0.5K0.5NbO3 thin films on sapphire substrates

Preferentially oriented perovskite-structured Na0.5K0.5NbO3 (NKN) thin films have been deposited on hexagonal Al2O3(011_2) substrates using rf magnetron sputtering of a stoichiometric, high-density, ceramic target. Structural and film surface properties were measured using x-ray diffraction and atomic force microscopy, respectively. Optical and waveguiding properties were characterized using a prism-coupling technique. We observed sharp and distinguishable TM and TE propagation modes and measured the refractive index of NKN thin films of different thicknesses. The ordinary and extraordinary refractive indices were calculated to be no=2.247±0.002 and ne=2.216±0.002 for a 2.0-μm-thick film at 632.8 nm. This implies a birefringence Δn=ne−no=−0.031±0.002 in the film. These first results show the potential use of rf-sputtered NKN films as an electro-optical active material.