Light transmission in photonic bandgap waveguides and photonic band crystals

Light propagation characteristics of line defect optical waveguides in a photonic crystal slab are explained by the photonic band calculation and experimentally demonstrated at 1.5 micron wavelengths by using the SOI substrate. A high efficiency sharp bend, which is a key for high density photonic ICs, is numerically demonstrated by the FDTD method. The essential low propagation loss against the imperfection of the structure is discussed from the perturbation theory. On the other hand, light transmission characteristics of finite size uniform photonic crystals without defects are theoretically investigated for various applications. The superprism filter is analyzed from dispersion surfaces. The wavelength resolution parameter is defined, which includes the angular dispersion and the beam divergence of light, and the performance of the filter is esti-mated for the optimum design. As another application of the superprism effect, a light deflection device having angled out-put interfaces against the input interface is proposed and numerically demonstrated. The nonlinear response in a photonic crystal made of a Kerr medium is also calculated by the FDTD method. The enhancement of the nonlinearity observed at certain band edges are explained by the photonic band property. To improve the transmission efficiency of these devices, some modified input and output interfaces are proposed and their effects are numerically demonstrated.