Photonic crystal waveguides with multiple 90° bends

In order to emphasize and demonstrate the importance of light confinement in the vertical direction, an otherwise ordinary two-dimensional photonic crystal waveguide structure operating at microwave frequencies was sandwiched between two metal plates. Such waveguides exhibited excellent guiding properties despite the existence of multiple 90° bends. From the experimental data, we have estimated that the propagation velocity of the waveguide is about 0.47 c, regardless of the number of bends, and that the bending loss is only 0.1 dB per bend.