The Special Properties Of Metamaterial Waveguides And Their Applications To Photonic Devices

The emergence of metamaterial with artificially engineered building blocks provides a new perspective on electromagnetic wave manipulation. Metamaterial can not only exhibit novel electromagnetic phenomena such as negative refraction and super-resolution imaging, but also be designed to achieve e.g., invisible cloaking, ultra-high refractive indices, zero refractive indices and light propagation with ultra-small group velocity. In this thesis, some special properties of metamaterials waveguide are thoroughly investigated and their applications to photonic devices are explored.First of all, the momentum carried by an electromagnetic wave travelling inside a left-handed metamaterial is studied. The momentum of light in a medium has undergone intense debates for over a century. As to the momentum of light in a metamaterial, even the direction of the light’s momentum remains ambiguous. Here we have studied the momentum of electromagnetic waves in a metamaterial based on macroscopic Maxwell’s equations. It turns out that the momentum of light in a metamaterial is in the direction of energy flow, instead of wave vectors. Our further analysis shows that our momentum theory is consistent with the requirement of the two fundamental physical laws, namely, the energy conservation and momentum conservation.Then the propagation of light in a tapered metamaterial slow light waveguide is studied. A metamaterial waveguide can be designed to support mode with zero group velocity, by tuning the thickness of the metamaterial core layer. Since the critical thickness corresponding to zero velocity is different for different light frequency, an article published in Nature claimed that lights in a broad frequency range can be stopped in the tapered waveguide, forming "trapped rainbow". However, our investigation finds that strong intermodal coupling between the forward mode and the backward mode will occur due to the degeneracy of these two modes at the critical thickness. The mode coupling will lead to the reflection of incident light, breaking down the dream of "trapped rainbow". Despite that, light can indeed be trapped inside the slow light waveguide for a relatively long time.Some photonic devices are designed by exploiting the unique properties of metamaterial.We have designed a dielectric waveguide with two elliptical silver nanoparticles embedded. The two nanoparticles work as bright state and dark state. The near field coupling between these two resonators results in a transmission spectrum similar to the quantum effect of electromagnetically induced transparency.We have also investigated the properties of individual and coupled waveguides made of hyperbolic metamaterials. The hyperbolic metamaterial waveguides are found to support modes with ultra-high refractive indices. The high-index waveguides are then utilized to greatly enhance the optical fields and optical forces by constructing a slot waveguide configuration.We have also proposed an extremely loss-anisotropic metamaterial capable of supporting the propagation of a diffraction-free beam with deep subwavelength size and a perfect infrared absorber made of metallic nanowire cavity arrays. The deep subwavelength beam propagation inside the loss-anisotropic metamaterial is due to the ultra-flat iso-frequency contour. The perfect absorption of incident light is explained by examining its electric resonance and magnetic resonance.In the end, we give a brief summary of our investigations and discuss some future research directions.