Three-dimensional control of light in a two-dimensional photonic crystal slab

Optoelectronic devices are increasingly important in communication and info rmation technology. To achieve the necessary manipulation of light (which c arries information in optoelectronic devices), considerable efforts are dir ected at the development of photonic crystals-periodic dielectric materials that have so-called photonic bandgaps, which prohibit the propagation of p hotons having energies within the bandgap region. Straightforward applicati on of the bandgap concept is generally thought to require three-dimensional (3D) photonic crystals(1-5); their two-dimensional (2D) counterparts confi ne light in the crystal plane(6,7), but not in the perpendicular z directio n, which inevitably leads to diffraction losses. Nonetheless, 2D photonic c rystals still attract interest(8-15) because they are potentially more amen able to fabrication by existing techniques and diffraction losses need not seriously impair utility. Here we report the fabrication of a waveguide-cou pled photonic crystal slab (essentially a free-standing 2D photonic crystal ) with a strong 2D bandgap at wavelengths of about 1.5 mum, yet which is ca pable of fully controlling light in all three dimensions. These features co nfirm theoretical calculations(16,17) on the possibility of achieving 3D li ght control using 2D bandgaps, with index guiding providing control in the third dimension, and raise the prospect of being able to realize unusual ph otonic-crystal devices, such as thresholdless lasers(1).