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Polarization Switching (polarization + switching)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Unraveling Deterministic Mesoscopic Polarization Switching Mechanisms: Spatially Resolved Studies of a Tilt Grain Boundary in Bismuth Ferrite

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009
Brian J. Rodriguez
Abstract The deterministic mesoscopic mechanism of ferroelectric domain nucleation is probed at a single atomically-defined model defect: an artificially fabricated bicrystal grain boundary (GB) in an epitaxial bismuth ferrite film. Switching spectroscopy piezoresponse force microscopy (SS-PFM) is used to map the variation of local hysteresis loops at the GB and in its immediate vicinity. It is found that the the influence of the GB on nucleation results in a slight shift of the negative nucleation bias to larger voltages. The mesoscopic mechanisms of domain nucleation in the bulk and at the GB are studied in detail using phase-field modeling, elucidating the complex mechanisms governed by the interplay between ferroelectric and ferroelastic wall energies, depolarization fields, and interface charge. The combination of phase-field modeling and SS-PFM allows quantitative analysis of the mesoscopic mechanisms for polarization switching, and hence suggests a route for unraveling the mechanisms of polarization switching at a single defect level and ultimately optimizing materials properties through microstructure engineering. [source]

Phase Field Simulations of Hysteresis and Butterfly Loops in Ferroelectrics Subjected to Electro-Mechanical Coupled Loading

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2006
A. K. Soh
Two-dimensional computer simulations of ferroelectric polarization switching have been performed using the phase field simulation model developed by employing the time-dependent Ginsburg,Landau equations. The bulk-free energy, polarization gradient energy, long-range dipole,dipole electrostatic interactions, and elastic energy were taken into account in the above-mentioned simulations. The influences of electric,mechanical coupled loading on the hysteresis and butterfly loops were studied. The results showed that the coupled electro-mechanical loading could change both the coercive field of ferroelectric materials and the symmetry of hysteresis and butterfly loops. [source]

Environmentally stable nonlinear optical polarization switching by using a nonreciprocal all-optical circuit

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2009
Naoto Kishi
Abstract We proposed and demonstrated a stable nonlinear optical polarization self-switching based on nonreciprocal nonlinear phase shift induced by self-phase modulation in optical fiber. The polarization self-switching was achieved at input power levels of around 10 mW in a nonreciprocal circuit using Faraday rotator mirrors. This nonlinear polarization switching is quite stable against polarization fluctuation caused by environmental perturbation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2056,2059, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24548 [source]

Optical gain and gain saturation of blue-green InGaN quantum wells

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2010
Dmitry Sizov
Abstract Using varied stripe length method we systematically studied optical gain properties of blue-green 3,nm InGaN QWs grown on c -plane and (11,22) semipolar substrates. We determined that for such structures when the product of modal net gain at peak and stripe length exceeds factor 5 the gain saturation occurs due to depletion of pumped carriers. We then focused our attention on the gain in unsaturated conditions. We observed strong gain peak position blue shift with increase of pumping power for both substrate orientations due to quantum well state filling and for c -plane due to piezoelectric field screening. Thus in order to increase lasing wavelength, minimizing optical losses, and maximizing modal gain are essential. We then found that for the semipolar QWs the gain at ,500,nm was 2× higher with the stripe along [,1,123] direction despite the fact that at low pumping level the polarization switching of spontaneous emission resulted predominant E||[,1,123]. Finally we compared the semipolar and c -plane QWs and found that the gain increase with pumping power of c -plane QW is slower than that for semipolar QW in high gain direction while the transparency pumping power is lower for c -plane. [source]