Optimization of 2D photonic crystal waveguide using displacement and narrowing technique

Abstract

In this thesis, an approach to analyze PhC structures has been developed. This approach is based on the displacement and narrowing technique. The motive is to design and optimize the desired photonic crystal waveguides and to optimize the transmission loss. Firstly, a Z -shape, a Y-shape and a Mach Zehnder photonic crystal waveguide is designed and then the designs are optimized applying the displacement and narrowing technique. The displacement method allows altering positions of certain PhC rods/atoms, thus breaking the periodicity of the rods, which is known as the displacement of the PhC rods. The narrowing technique is mainly applied to alter the characteristics of the PhC rods/atoms, which basically implies that, it allows altering the shape or pattern of the PhC rods by changing its radius, width and other certain parameters. So basically, the parameters of the PhC rods have been modified according to the requirements. Then, the PhC waveguides have been fine-tuned by displacing these narrowed rods in the bending regions of the designed PhC waveguides. The resulting wave propagation through the optimized waveguide showed that relatively small design areas were enough to yield the wanted improvement in efficiency and the numerical results obtained have shown much improved transmission. The design has been realized in a gallium-arsenide photonic crystal structure. The whole design and simulation process including PhC band gap simulation and wave propagation analysis is done using the software RSOFT.