Research Of Paraxial Propagation Properties Of Laser Beam In Negative Index Materials

Negative index materials (NIM) are artificially made composites that have both negative permittivity and permeability. Owing to their novel physical properties and exciting prospect in industrial applications, metamaterials have been gaining growing concern around the global academic communities. They’ve become one of the most important forefronts in scientific research and are expected to exert great and profound influence on traditional optics and modern photonics. This dissertation endeavors to probe into the propagation and manipulation of laser beams in metamaterials, which, to the best of knowledge, is a fairly timely contribution to this area. Our research has led to several new and interesting results.First, we study a cascaded negative index material slab system with the aid of matrix optics. The expressions of ABCD matrix element related to the NIM slab system are derived. Under the paraxial approximation, the propagation characteristics of Gaussian beams in various NIM slab systems are unveiled. We get the field intensity distributions in and outside the NIM slab and the conditions of focusing and phase compensation. As long as beams focus in the first region of the NIM slab systems, they will focus in the last positive region of the NIM slab system. Our research also indicates that whether beams focus in the intermediate regions with positive and negative index or not. the focusing properties in the last positive region remain unaffected. Only when the focusing conditions are satisfied in the first slab can the beams be reconstructed and restored without deformation. The ABCD matrix formalism utilized in the NIM slab systems stays away from the knotty integral formalism. An international peer commented that most of the theoretical works on wave interaction with NIM involved plane-wave propagation, this work, however, deals with the propagation of a TEM00Gaussian beam in a slab of an NIM.Second, we apply the ABCD formalism to the gradient negative index media and investigate the propagation and transformation properties of Gaussian beams in this medium. We derive the ABCD formalism in positive gradient NIM and obtain the propagation model as a result. Spatial soliton and the spatial breather propagation in this medium are revealed. Our research suggests that the gradient coefficient has a significant effect on the focusing ability of slab. When the gradient coefficient increases, the quasi-lense effect becomes more prominent and notable. As a result, the focusing ability improves and the beam waist in the focal point shrinks. When Gaussian beams propagate in negative gradient NIM, the beam waist enlarges as the distance increases. There are no spatial soliton and breather transmission phenomena, which is completely different from the propagation characteristics in positive gradient negative index media.Third, the anomalous propagation phenomena of electromagnetic wave and beam in complete anisotropic negative index materials are investigated as the angle between optical axis and the propagation axis is nonzero. The perfect or imperfect backward wave propagation will appear when certain conditions, like the angle between optical axis of NIM and wave axis, the permittivity and permeability tensors, and the incident angle, are satisfied. When TM wave is backward wave, the corresponding TM wave is progressive wave, and vice versa. We analyze backward wave in anisotropic negative index materials in several dispersion relations and find that the backward wave in Epsilon-Near-Zero negative index materials is a perfect backward wave. If a certain condition between the permittivity and permeability tensors is satisfied, anomalous omnibearing total reflection would show up. Based on the propagation phenomena of beam in complete anisotropic negative index materials, we propose a new type of thin high pass spatial filter. Our hypothesis is confirmed by the numerical stimulation results of modulated Gaussian beams in this medium. This property could also be applied to low frequency spatial reflectors.