Ultrashort pulse propagation at the photonic band edge: Large tunable group delay with minimal distortion and loss

We examine optical pulse propagation through a 30-period, GaAs/AlAs, one-dimensional, periodic structure at the photonic band-edge transmission resonance. We predict theoretically---and demonstrate experimentally---an approximate energy, momentum, and form invariance of the transmitted pulse, as well as large group index (up to 13.5). The group index is tunable and many orders of magnitude more sensitive to variation in material refractive index than for bulk material. We interpret this observation in terms of time-dependent electromagnetic states of the pulse-crystal system.