Reflective phase-only modulation using one-dimensional photonic crystals

Phase-only modulation is shown to be possible upon reflection off one-dimen sional photonic crystals. Within the photonic bandgap, photons travel to so me penetration depth in the periodic structure and experience phase change. Modulation of the effective index or layer thickness within the gap will t hen produce phase-only modulation. Phase modulation of more than pi is poss ible upon an equivalent variation of few nm of the layer thickness. This co uld be the basis for phase-only modulators used in mode locking of photonic crystal lasers and reflective adaptive optics components.