Photonic band gap crystals offer unique ways to tailor light and the propagation of electromagnetic waves. In analogy to electrons in a crystal, EM waves propagating in a structure with a periodically-modulated dielectric constant are organized into photonic bands separated by gaps in which propagating states are forbidden. Proposed applications of such photonic band gap crystals, operating at frequencies from microwave to optical, include zero- threshold lasers, low-loss resonators and cavities, and efficient microwave antennas. Spontaneous emission is suppressed for photons in the photonic...