90 research outputs found
Size Dependence and Convergence of the Retrieval Parameters of Metamaterials
We study the dependence of the retrieval parameters, such as the electric
permittivity, the magnetic permeability and the index of refraction, , on
the size of the unit cell of a periodic metamaterial. The convergence of the
retrieved parameters on the number of the unit cells is also examined. We have
concentrated our studies on the so-called fishnet structure, which is the most
promising design to obtain negative at optical wavelengths. We find that as
the size of the unit cell decreases, the magnitude of the retrieved effective
parameters increases. The convergence of the effective parameters of the
fishnet as the number of the unit cells increases is demonstrated but found to
be slower than for regular split ring resonators and wires structures. This is
due to a much stronger coupling between the different unit cells in the fishnet
structure.Comment: Journal-ref and DOI adde
Near infrared and optical beam steering and frequency splitting in air holes-in-silicon inverse photonic crystals
We present the design of a dielectric inverse photonic crystal structure that couples line-defect waveguide propagating modes into highly directional beams of controllable directionality. The structure utilizes a triangular lattice made of air holes drilled in an infinitely thick Si slab, and it is designed for operation in the near-infrared and optical regime. The structure operation is based on the excitation and manipulation of dark dielectric surface states, in particular on the tailoring of the dark states’ coupling to outgoing radiation. This coupling is achieved with the use of properly designed external corrugations. The structure adapts and matches modes that travel through the photonic crystal and the free space. Moreover it facilitates the steering of the outgoing waves, is found to generate well-defined, spatially and spectrally isolated beams, and may serve as a frequency splitting component designed for operation in the near-infrared regime and in particular the telecom optical wavelength band. The design complies with the state-of-the-art Si nanofabrication technology and can be directly scaled for operation in the optical regime
Negative refractive index due to chirality
We demonstrate experimentally and numerically that metamaterials based on
bilayer cross wires give giant optical activity, circular dichroism, and
negative refractive index. The presented chiral design offers a much simpler
geometry and more efficient way to realize negative refractive index at any
frequency. We also developed a retrieval procedure for chiral materials which
works successfully for circularly polarized waves
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