Study of surface plasmon polaritons near the photonic-bandgap edge for interphotonic band switching devices.

The photonic energy band structures near the bandgap edges of surface plasmon polariton in dielectric lattice structures on a smooth silver film were studied. At the bandgap edges, sharp changes of the surface plasmon polariton's transmittance arise owing to small changes in the refractive index around the lattice structure, which results in the band transition between the pass band and the stop band. On the analogy of 'the phase transition' between the surface plasmon polariton's conductive phase and the insulation phase, the surface plasmon polariton's phase diagram of the 1D lattice structure at a single frequency (lambda approximately 780 nm) with parameters of the pitch and the refractive index of lattice were investigated. At the boundary, the most sensitive transition was found between the second pass band and the first stop band, with the approximately 0.5 lattice filling factor. The surface plasmon polariton's phase state has been determined by far-field observation using an optical microscope.

Reduction of propagation and bending losses of heterostructured photonic crystal waveguides by use of a high-delta structure.

We describe the fabrication and evaluation of a low-loss, high-delta optical waveguide consisting of heterostructured photonic crystals. The waveguide is composed of a multilayer stack of Ta2O5/SiO2 and is prepared by use of the autocloning technique. Light is guided in the waveguide by the difference in the effective refractive indices of the constituent photonic crystals. By improving the design of the core region so that is has a flat multilayer structure, we achieve delta = 3.09% for the in-plane direction and net propagation loss of 0.56 dB/mm at lambda = 1.6 microm. Experiments also suggest that the bending loss of the waveguide can be reduced to less than 0.1 dB if the curvature radius is larger than 700 microm.

Photonic crystal waveguides utilizing a modulated lattice structure.

We experimentally demonstrate a new class of optical waveguide consisting of a-Si/SiO(2) autocloned photonic crystals with modulated lattice structure. The waveguide utilizes the macroscopic form birefringence of photonic crystals and confines light by the difference in the effective refractive index. A monopole modal field with spot diameters of 6.9 micromx6.5 microm was observed at a wavelength of 1.55 microm. The propagation loss of the waveguide at the wavelength was found to be ~4.2 dB/mm at most.