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The field of optics has been an exceptionally rich area of modern physics, and the optical lens has long been the essential tool in studying phenomena. These lenses are governed by classical optics and their focusing power derives from the refractive index contrast. However, an intrinsic limitation in wave mechanics is that no lens can ever focus light on an area smaller than a square wavelength; regardless of polishing techniques or inventions of new dielectrics, this fundamental limitation still holds. Our research is focused on utilizing a class of "superlenses" to transcend these traditional limitations. These superlenses are characterized by a negative index of refraction (NIR) which is possible in materials that have both dielectric and magnetic permeability being less than zero. Even a parallel-sided slab of such material will be able to effectively focus light to within a few square nanometers.
In particular, theoretical calculations suggest that NIR materials will actually amplify evanescent waves so that image reconstruction is near perfect. By achieving perfect impedance matching with the vacuum, it is possible to reduce the coefficient of reflection to zero, allowing for seamless transmission of images. The key limitation to this technique is the requirement that both the dielectric and magnetic permeability be negative; although this has been done at microwave frequencies using split-ring resonators, it has yet to be achieved at optical frequencies since magnetic response typically vanishes. Our research is interested in combining narrow atomic resonances with bent metallic structures that can effectively couple to magnetic fields. This hybrid system would allow for resonance phenomena to be observed at optical frequencies, and can resolve the limitations associated with previous experiments on meta-materials. Computational techniques involving the transfer matrix and simulations of negative refraction will be central to the development of effective NIR materials at optical frequencies. These matrix calculations will allow us to analytically study wave propagation and resonant tunneling in NIR materials, photonic crystals, and surface plasmons.
Yao, N., Larsen, R., and Weitz, D., Probing nonlinear rheology with inertio-elastic oscillations. Journal of Rheology 52, 1013-1025 (2008).
Yao, N., Larsen, R., and Weitz, D., Characterizing the nonlinear rheology of biopolymer networks using inertio-elastic oscillations. Conference proceedings, XVth International Congress on Rheology (2008).
Francisco Artigas, Alex Marti, Norman Yao, and Ildiko Pechmann, Chlorophyll Detection and Mapping of Shallow Water Impoundments Using Image Spectrometry, Research Letters in Ecology, vol. 2008, Article ID 146217, 4 pages, 2008. doi:10.1155/2008/146217
Yao, N., Broedersz, C., Lin, Y., Kasza, K., MacKintosh, F., and, Weitz, D., Elasticity in Ionically Cross-linked Neurofilament Networks. [Submitted to Biophysical Journal]
Lin, Y., Yao, N., Broedersz, C., Herrmann, H., MacKintosh, F., and Weitz, D., Origins of elasticity in intermediate filament networks, Physical Review Letters 104, 058101 (2010).
Nonlinear Viscoelasticity of Actin Cross-linked with Mutant alpha-Actinin-4 [To be submitted to PNAS]
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