Research Of Reflection Lesswave Guide Couplers Based On Transformation Optics

Transformation optics, reported by Pendry, J.B. in 2006, enables us to control electromagnetic waves. It is a theory of guiding people to achieve the special permeability and permittivity that needed when electromagnetic wave propagating in a particular way. Waveguide couplers based on transformation optics have the advantages of compact structure and little distortion. However, the most typical devices based on traditional transformation optics suffer from the reflections as long as connect region with different cross sectionsIn this thesis, we proposed an approach to solve the reflection which can be used in almost any manner. And then, on this basis, we paved a way to make the material nonmagnetic. They can help us to design reflectionless devices and to simplify the parameters of the material with important theoretical significance. We designed some waveguide couplers without reflection to ensure those methods are valid. And the simulation results indicated that those devices have excellent functionalities.First, we showed the details of transformation optics derivation. At the same time, we got the changed values of permittivity and permeability. Moreover we derived the inherent relationship of transformation matrix elements. And then we introduced the existing modes in the rectangular waveguide. Furthermore, we showed the electric and magnetic fields distribution of those modes. We also introduced the boundary condition of electric and magnetic fields. Those are all needed by following demonstration of reflectionless transformation optics.Second, we derived a reflectionless condition of transformation optics for TE and TM modes by introducing a coefficient, which is non-zero, from the above basic knowledge. And then we designed a general waveguide coupler with the purpose to verify the versatility of reflectionless condition. Then we simulated these waveguide couplers based on traditional transformation-optical design and reflectionless condition on computer. Furthermore, we got the curve of S-parameter and the flux density distribution on waveguides and couplers. And then we compared these data to verify the correctness of the condition and introduce the excellent functionalities of the coupler. We also compared these characteristic parameters in different boundary of waveguide couplers to find a better one.Finally, in order to simplify the parameters of transformation material, we let the coefficient become a matrix to derive the nonmagnetic and reflectionless condition of transformation optics for TE mode. Additionally we designed a waveguide coupler based on this condition. And then we compared this coupler with that based on traditional transformation optics to verify the condition and the excellent functionalities of the coupler.