Applied Physics

Directing Light

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Science  10 Mar 2000:
Vol. 287, Issue 5459, pp. 1713
DOI: 10.1126/science.287.5459.1713f

One of the future goals for all-optical circuitry is the miniaturization of the waveguides that direct light to where it is needed in a way that could be integrated with conventional electronic circuitry. One approach is to use photonic band gap materials, which consist of structures of periodically contrasting refractive indices. These materials prevent the propagation of electromagnetic waves with wavelengths on the order of the spatial periodicity of the structure. However, introduction of a “defect” to the periodicity produces a conduit for these otherwise excluded waves to propagate.

Previous work with relatively large periodicity structures (for example, a square array of 0.25mm diameter alumina rods arranged with a lattice constant of 1.27mm) have shown the ability to direct millimeter waves around 90° corners. Extending this idea to a much smaller scale, with submicrometer periodicity (0.8 μm), Tokushima et al. have etched an array of holes into a silicon wafer. Introducing a break in the periodicity of the array as the defective region, they have demonstrated the ability to direct 1.55 μm infrared light around sharp bends. The ability to direct light at this technologically important wavelength, the standard used in present optical communications, may spur the development of on-chip, all-optical waveguides.—ISO

Appl. Phys. Lett.76, 952 (2000).

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