Photonic crystal power splitter and wavelength multi/demultiplexer based on directional coupling

In this paper, first by applying a theoretical approach (coupled-mode theory and one-dimensional scattering theory model) as well as a numerical approach, the transmission properties of different right angle bend geometries are investigated. Then using optimized bends, a two-dimensional photonic crystal power splitter based on directional coupling is analyzed. Effects of changing coupling length and distance between parallel waveguides on output transmissions are investigated. By further splitting the power in each branch a power splitter with four output branches is proposed. Our numerical simulation with a finite-difference time-domain (FDTD) technique shows that total transmission up to 96% and 92% is obtained for power splitters with two and four output branches, respectively, throughout the calculated coupling lengths. As another application a compact size wavelength multi/demultiplexer composed of optimized 90° bent waveguides and directional couplers is designed.