Transmission characteristics of 90° bent photonic crystal waveguides

There are several key factors that affect the transmission characteristics of the 90 degrees (L-shaped) bent photonic crystal waveguides. The first factor is the direct coupling efficiency from the incident lights into the waveguides. The second one is the bandgap deviations of the photonic crystals. And the third factor is the optical reflections in the bent corners. In this article, we compare three types of L-shaped bent photonic crystal waveguides. One is the original type, which has an abrupt right-angle bend. Another is an improved 90 degrees bend with a 45 degrees-mirror. The other is an L-shaped bent photonic crystal waveguide with a 45 degrees-transitional section. We investigate their respective frequency responses and observe the improvements in the total transmission efficiencies provided by the latter types.