Characteristics Of Waveguides With Negative Refraction And Their Applications

Negative refraction media have been a focus recently for the electromagnetic waves in them exhibit many extraordinary and interesting properties. Now, metamaterials, which are found having negative refraction property, mainly include left-handed metamaterials (LHM), photonic crystals (PCs) and chiral media etc. In the paper, the guided waves in waveguides made of left-handed materials and common dielectric are investigated. The characteristics of waveguides which composed of a negative refraction PCs, core layer and air or both reflectors composed of negative refraction PCs are studied respectively. Besides, the giant negative Goos-Hanchen (GH) shifts for beam totally reflected by photonic crystal with a negative effective refraction index are discussed and the ways to fabrication the 3-D negative refraction photonic crystal by the self-organized method are also described. Our original jobs in research are listed as follow:1) The properties of guided waves in various waveguides are studied. In these waveguides, the fundamental modes may be absent, and two modes of same kind of mode but of opposite transferring direction may exit simultaneously. The speed of guided wave can be extremely slow, because of the present of LHM layer. This property of slow wave has many potential applications such as data storage and buffer. A waveguide structure to trap electromagnetic waves has also been proposed in the paper.2) The properties of guided waves in the waveguide which composed of 3 layers: air, core layer of high refraction index and PC layer are investigated. We found that the waveguide has some outstanding properties, such as the guide modes of several rangs of frequencies flow slowly, the slow-light modes can exist in the various waveguides of different thickness, even in a very thick waveguide, and the waveguide would be sigle mode one even for a large value of thickness. These properties can be utilized for the applications of optical memory, optical delay lines and so on.3) The GH lateral shift effects for a Gaussian beam totally reflected by the negative PC waveguide structure are studied by layer-KKR method. It is found that the giant negative GH shift can be obtained when the thickness of cladding layer over the PC is properly chosen, and after optimized, the totally reflected beam can retain a single beam of goodprofile even for a very narrow incident beam. For some special situation, the GH lateral shift is very sensitive to a small change of the refractive index of the cladding layer, and this property can be utilized for the applications of switching, modulating and sensing.4) The symmetric negative refraction PC waveguide, of which the core layer is made of air, is studied. It is found that the characteristic of the waveguide are similar to those of left-handed meta-material symmetric waveguide. Thus, for optical wave, the negative refraction PC waveguide is a better choice for application than left-handed meta-material waveguide, since the large loss of the left-handed meta-materials.