Ka Yan Lee

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In this paper, we show that bone piezoelectricity-a phenomenon in which bone polarizes electrically in response to an applied mechanical stress and produces a short-range electric field-may be a source of intense blast-induced electric fields in the brain, with magnitudes and timescales comparable to fields with known neurological effects. We compute the(More)
We perform full 3D topology optimization (in which "every voxel" of the unit cell is a degree of freedom) of photonic-crystal structures in order to find optimal omnidirectional band gaps for various symmetry groups, including fcc (including diamond), bcc, and simple-cubic lattices. Even without imposing the constraints of any fabrication process, the(More)
We prove, via an elementary variational method, one-dimensional ͑1D͒ and two-dimensional ͑2D͒ localiza-tion within the band gaps of a periodic Schrödinger operator for any mostly negative or mostly positive defect potential, V, whose depth is not too great compared to the size of the gap. In a similar way, we also prove sufficient conditions for 1D and 2D(More)
We derive a sufficient condition for the existence of index-guided modes in a very general class of dielectric waveguides, including photonic-crystal fibers (arbitrary periodic claddings, such as "holey fibers"), anisotropic materials, and waveguides with periodicity along the propagation direction. This condition provides a rigorous guarantee of(More)
We present analytical results that shed new light on the properties of photonic-crystal fibers (optical fibers with periodic structures in their cladding). First, we discuss a general theorem, applicable to any periodic cladding structure, that gives rigorous conditions for the existence of cutoff-free guided modes—it lets you look at a structure, in most(More)
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