Development of 3D-semiconductive photonic crystals with a bandgap in the optical wave region

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Much interest has been drawing in photonic crystals in which the refractive index changes periodically. A photonic bandgap is formed in the crystals, and the propagation of electromagnetic waves is prohibited for all wave vectors. Various important scientific and engineering applications such as control of spontaneous emission, zero-threshold lasing, very sharp bending of light, trapping of photons, and so on, are expected by utilizing the photonic bandgap and the artificially introduced defect states and/or light-emitters. In this project, we have succeeded in developing complete 3D photonic crystals with sufficient bandgap effects at near-infrared wavelengths (1-2um) based on a method where III-V semiconductor stripes are stacked with the wafer-fusion and the laser-beam assisted very precise alignment. The properties of the full 3D photonic bandgap crystals at near-infrared wavelengths have been investigated in detail and possible applications to ultrasmall optical integrated circuits (optical chip) have been discussed.In this project, 3D photonic crystal research experience has been applied to 2D photonic crystals, which are also promising since specific (not almighty, but important) functional devices can be realized even though the control of light is limited two-dimensionally. We investigated novel functional devices utilizing 2D photonic crystals. One is a 2D photonic crystal laser with multi-directionally distributed feedback effect in 2D photonic lattice structure. It has been shown that the device can work as a high-output power surface-emitting laser, which can oscillate in very large area with single mode. The other is a device utilizing a single defect in 2D photonic bandgap structure. The defect traps the photons which propagate through a waveguide formed in 2D photonic crystal slab and emits them to free-space. The basic operations have been successfully demonstrated.