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


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.


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.

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