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, o ne-dimensional, periodic structure at the photonic band-edge transmiss ion resonance. We predict theoretically-and demonstrate experimentally -an approximate energy, momentum, and form invariance of the transmitt ed pulse, as well as large group index (up to 13.5). The group index i s tunable and many orders of magnitude more sensitive to variation in material refractive index than for bulk material. We interpret this ob servation in terms of time-dependent electromagnetic states of the pul se-crystal system.