Enhancement of Magneto-Optical Effects in Gyrotropic Photonic Bandgap Materials

Friday, September 19, 2008 3:00 – 4:00 pm
Room 610, M&M Building

Dr. Amir A. Jalali
Department of Physics
Michigan Technological University

Abstract

Magneto-optic materials have many applications in a large variety of areas of integrated optics. Perhapsthe most common application of magneto-optic materials is in the construction of nonreciprocalwaveguides and magneto-optic isolators although there are also many applications in other areas ofintegrated optics such as magneto-optical fast switching, magneto-optical read-out disks, and magnetooptical sensors and visualizers. All of these applications are based on the magneto-optical activity of thematerial like polarization rotation of the light passing through the medium (Faraday rotation) andmagneto-optical tunability of the medium. Magneto-optical effects can be enhanced significantly in aperiodic structure, the so called photonic crystals, that exhibit photonic bandgaps. The enhancement ofmagneto-optical effects would thus allow large improvements in existing applications and even moreopen up new possibilities for advanced sensor devices and optical filters.

In this talk I will present a study of polarization rotation enhancement in one- and two-dimensionalphotonic crystals and provide theoretical and experimental support for a novel type of photonic bandgapin birefringent magnetooptic photonic crystal waveguides. Contradirectional coupling of fundamental tohigher order local normal modes in birefringent magnetooptic photonic crystal waveguides leads topartially overlapping gyrotropic bandgaps inside the Brillouin zone. The overlapping of gyrotropicbandgaps results in selective suppression of Bloch mode propagation. This type of photonic bandgapand degeneracy breaking inside the Brillouin zone are a result of the local coupling between differentelliptically polarized photonic states in magneto-photonic crystals. Large magnetically active changes inBloch mode polarization near the band edges are observed. These changes are not due to photontrapping as conventionally explained in other types of magnetooptic periodic systems.

The ability of magneto-optic photonic crystal waveguides to provide large polarization rotation and tightoptical confinement can also be exploited to produce highly sensitive biochemical sensors. Our studyshows that the polarization rotation at the edge of gyrotropic degenerate bandgaps is highly sensitive tosmall refractive index changes in the waveguide cover of the device.

Biography

Dr. Jalali received the PhD degree in Physics from the Royal Institute of Technology (KTH), Stockholm, Sweden, inNov. 2004. He spent two years as a Postdoctoral researcher at the Michigan Technological University, Michigan, USA. Since2007, He has been a Research Scientist at Michigan Technological University. His research interests are magnetooptic photoniccrystals, ferromagnetic resonance, waveguide technology and photonic biosensors.


Processing and Properties of Amorphous Reinforced Crystalline Matrix Composites in Ni-W Alloy System

Friday, September 5, 2008 3:00 – 4:00 pm
Room 610, M&M Building

Alex O. Aning
Virginia Polytechnic Institute & State University
Department of Materials Science & Engineering
Blacksburg, Virginia 24061

Abstract

Metal Matrix Composites (MMCs) are used as structural materials because of their ability tohave a combination of high strength and good ductility.  A common problem with MMCs utilizingvastly different materials is the difficulty in forming a strong matrix/reinforcement interfacewithout suffering extensive dissolution, debonding, or chemical reactions between thecomponents.  By using a reinforcement which has a similar chemistry and local atomic structureto that of the matrix, these critical problems can be reduced.  In this work, a nickel baseamorphous particulate reinforced crystalline nickel matrix composites were processed.  Thereinforcement, an equimolar NiW amorphous powder, was synthesized in a SPEX mill by themechanical alloying process.  The amorphous and crystalline nickel powders were blended inan Attritor mill in varying volume fractions and then consolidated using: hot-isostatic pressing(HIP), or combustion driven compaction (CDC) process.  This work revealed that the amorphousNiW reinforcement provided strength and hardness to the ductile Ni matrix while simultaneouslymaintaining a strong interfacial bond due to the similar chemistry of the two components.  Thestrengthening achieved in the composite is attributed to particulate/matrix boundary strengthening.

Biography

Dr. Alex O. Aning is an Associate Professor of Materials Science and Engineeringat Virginia Tech.  He obtained the BS degree in Physics from Morgan State University,Baltimore in 1977, and Ph.D. in Metallurgical Engineering from University of Missouri- Rolla in1982.  After a year of post-doctoral studies at Rolla he joined the Physics Department at MorganState in 1983.  At Morgan State he helped develop a new engineering school.  He later becamethe head the Electrical Engineering Department and lead it to become ABET accredited on thefirst attempt.  He joined Virginia Tech in 1992; from 1998 to 2005, he was part of theEngineering Education Department.  He has held visiting professorships at the Johns HopkinsUniversity (1992) and the University of Virginia (1989/90).  He does research in the areas ofphase transformations, and synthesis and processing of metallic, ceramic and compositematerials.  His current activities include solid-state formation of bulk amorphous alloys, andamorphous phase-strengthened metal matrix composites.  He is a member of TMS and ASMInternational.


New Funding

Peter Moran received $65,000 from the University of Michigan (MIIE program) for “IME: A Proposal to the MIIE Industry and Economic Engagement Fund for Forming a Partnership Between Tellurex, Corp. and Michigan Tech to Engineer Materials for High-Efficiency Thermoelectric Power Generators.” MIIE is Michigan Initiative for Innovation and Entrepreneurship.


New Funding

Associate Professor Peter Moran (MSE) received $76,000 from the U.S. Department of Defense Office of Naval Research for “Developing Highly Magnetoelectric Fe(1-x)Gax/PMN-PT Heterostructures for Integration onto SiC.”