| Summary: | 碩士 === 國立中央大學 === 光電科學研究所碩士在職專班 === 95 === In conventional crystal optics, the permittivity of an optical medium is assumed to be positive and the relative permeability is always set as 1, in accord with the situations encountered for natural crystals. Around the beginning of this century, scientists had successfully realized the first prototype of left-handed metamaterial by constructing artificial structures consisting of periodic arrays of metallic wires and split rings. The negative-refraction behavior and anisotropic properties for electromagnetic waves propagating in these media have widened the available range of parameters in optics.
Responding to this developing trend, we study in this thesis according to Maxwell''s equations the propagation behaviors of electromagnetic waves in indefinite media. In these media, each of the principal elements of the permittivity and permeability tensors can be any positive or negative real number. The analytic results are expressed by vectorial diagrams with dispersion curves, which help us to choose the appropriate characteristics of the media in the beginning.
Propagation of Gaussian beams incident onto various kinds of indefinite media with arbitrary signs of permittivity and permeability tensors are then studied numerically using k-spectrum method (“summing over plane waves” method). The simulation results confirm the predictions made from analytical method on the transmission and reflection directions of the beams. We have also considered the situations that the principal and spatial coordinates are not parallel to each other.
By appropriately combining the medium parameters, we further discuss and illustrate four application examples, which include the omnidirectional polarizer, 2-in-1 polarizer, full transmittance collimator, and the excitation of surface waves. The analytical and simulation results and numerical tools provided here might be valuable for future researches on related topics.
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