Ohmic loss in metal based metamaterials continues to be one of the primary impediments to their application at infrared and visible frequencies. Dielectric metamaterials offer one potential solution to this issue by eliminating ohmic loss as well as avoiding saturation in the magnetic response at high frequencies. In this talk, I will discuss our recent efforts to develop purely dielectric metamaterials at optical frequencies based on structured silicon including both non-resonant and resonant configurations. Non-resonant dielectric metamaterials are implemented for chip-based photonics using both nanostructured waveguides and adiabatically tapered waveguides. In both cases, a spatially varying refractive index profile is utilized for achieving transformation optics devices including highly efficient free-space couplers and massively parallel waveguide crossings. By avoiding resonances and metallic elements, the devices are both broadband and low-loss. I will also outline the development of resonant dielectric metamaterials for achieving near-zero refractive index at optical frequencies. These metamaterials are formed from unit cells exhibiting both electric and magnetic dipole Mie resonances. By overlapping these two resonances, we show how an impedance matched zero-refractive index can be achieved at optical frequencies. Such materials can be applied for a variety of applications including directional emitters, filters, and compact lens systems.
Events Calendar View
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Departmental Colloquium
Nov 8, 2012
All-Dielectric Optical Metamaterials and Devices
Guest: Prof. Jason Valentine, Mechanical Engineering Department, Vanderbilt University
Thursday, November 8, 2012 4:00 pm - 5:00 pm
Location: 202 -
Observatory Open House
Nov 9, 2012
Observatory Open House
Friday, November 9, 2012 7:00 pm - 9:00 pm
Location: Physics Building Observatory 4th Floor -
Departmental Colloquium
Nov 15, 2012
Discovery of a Higgs-like Boson with the ATLAS Experiment at the CERN LHC
Guest: Kenneth Johns, University of Arizona
Thursday, November 15, 2012 4:00 pm - 5:00 pm
Location: 202The Standard Model of particle physics has been successfully tested experimentally for over 30 years with no discrepancies.
Yet the Higgs boson, a key component of the Standard Model needed to provide mass to elementary particles, remained undetected. Now in 2012 the hunt for the Higgs boson is likely over. Experimental evidence from the ATLAS experiment at the CERN Large Hadron Collider (LHC) for the production of a new neutral boson will be presented.The production and decay of this particle is compatible with Standard Model Higgs boson. The future LHC and Higgs physics program will be discussed.
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NanoSEC Seminar
Nov 30, 2012
Fabrication, Electrokinetics, and Applications of Carbon Nanotube Membranes
Guest: Prof. Ji Wu, Department of Chemistry, Georgia Southern University
Friday, November 30, 2012 4:00 pm - 5:00 pm
Location: Riverbend Research South Laboratory AuditoriumRecently carbon nanotube (CNT) membrane has been a subject of intensive research activities due to their unique attributes, such as i) a dramatically enhanced fluid flow, ii) functional chemistry at the CNT tip entrance for effective chemical and biological separations, and iii) electrically conductive carbon nanotubes allowing for efficient electrochemical functionalization and electro-osmosis pumping.1-5 Meanwhile, the estimated overall costs of drug addiction and abuse in the United States alone exceed half a trillion dollars annually as reported by National Institute on Drug Abuse (NIDA). Classical transdermal patches for drug addiction and abuse treatments like nicotine patch can only provide constant dosing rates. However many drug abuse and addiction treatments demands variable dosing rates. Herein, a relatively low-cost microtoming method has been developed to fabricate carbon nanotube (CNT) membranes in large scale. The tips of CNT membranes were functionalized using an efficient electrochemical grafting method, following by a series of chemical coupling reactions. It was demonstrated that Ionic mobilities through CNT cores are enhanced by a factor of ~4 with a significant rectification seen for large anion/cation mixtures. High electro-osmotic flows of ~3 cm/s-V is seen for ~ 1nm single walled CNTs and ~0.15 cm/s-V for ~ 7nm multi-walled CNTs. The enhanced electrophoretic and electro-osmotic phenomenon of CNT membranes have been successfully applied to a programmed transdermal nicotine patch that can provide therapeutically useful fluxes ranging from high (1.30.65 μmol/hr-cm2) and to low (0.330.22 μmol/hr-cm2) for efficient smoking cessation treatments (in vitro (human skin) & in vivo (hairless guinea pig)).
Bio: Dr. Ji Wu is an assistant professor of chemistry at Georgia Southern University, Statesboro, GA. He has been working as a postdoctoral scholar in University of Kentucky with research focus on the fabrication, electro-kinetics and applications of carbon nanotube membranes from 2007-2012. He received his PhD degree in Inorganic and Materials Chemistry from Texas Christian University in 2007, following his Advisor, J. L. Coffer. His PhD research was on erbium-doped semiconducting nanomaterials such as silicon and germanium nanowires. He also earned a Masters’ degree in Organometallic Chemistry from Anhui University (Hefei, China) in 2000. He has contributed over 20 publications on peer-reviewed journals, such as Nature Nano., PNAS, Nano Letters, Advanced Materials, J. Pharm. Sci. etc.
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Observatory Open House
Dec 7, 2012
Observatory Open House
Friday, December 7, 2012 7:00 pm - 9:00 pm
Location: Physics Building Observatory 4th Floor -
CSP Lunch Seminar
Jan 15, 2013
Probability Distribution of the Order Parameter in the Directed Percolation Universality Class
Guest: Paulo Martins, Institute of Physics, University Federal de Mato Grosso, Brazil
Tuesday, January 15, 2013 12:30 pm - 1:30 pm
Location: CSP Conference Room (322)
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