PHOTONIC crystals are artificial structures having a periodic dielectric structure designed to influence the behaviour of photons in much the same way that the crystal structure of a semiconductor affects the properties of electrons1. In particular, photonic crystals forbid propagation of photons having a certain range of energies (known as a photonic bandgap), a property that could be incorporated in the design of novel optoelectronic devices2. Following the demonstration of a material with a full photonic bandgap at microwave frequencies3, there has been considerable progress in the fabrication of three-dimensional photonic crystals with operational wavelengths as short as 1.5 μm (ref. 4), although the optical properties of such structures are still far from ideal5. Here we show that, by restricting the geometry of the photonic crystal to two dimensions (in a waveguide configuration), structures with polarization-sensitive photonic band-gaps at still lower wavelengths (in the range 800-900 nm) can be readily fabricated. Our approach should permit the straightfor-ward integration of photonic-bandgap structures with other optical and optoelectronic devices.