title: Group velocity, energy velocity, and superluminal propagation in finite photonic band-gap structures.
abstract: We have analyzed the notions of group velocity V(g) and energy velocity V(E) for light pulses propagating inside one-dimensional photonic band gap structures of finite length. We find that the two velocities are related through the transmission coefficient t as V(E)=/t/(2)V(g). It follows that V(E)=V(g) only when the transmittance is unity (/t/(2)=1). This is due to the effective dispersive properties of finite layered structures, and it allows us to better understand a wide range of phenomena, such as superluminal pulse propagation. In fact, placing the requirement that the energy velocity should remain subluminal leads directly to the condition V(g)<or=c//t/(2). This condition places a large upper limit on the allowed group velocity of the tunneling pulse at frequencies of vanishingly small transmission.
authors: INFM at Dipartimento di Energetica, Università di Roma La Sapienza, Via Scarpa 16, I-00161 Rome, Italy.
authors: G
authors: G
authors: D'Aguanno
authors: M
authors: M
authors: Centini
authors: M
authors: M
authors: Scalora
authors: C
authors: C
authors: Sibilia
authors: M J
authors: MJ
authors: Bloemer
authors: C M
authors: CM
authors: Bowden
authors: J W
authors: JW
authors: Haus
authors: M
authors: M
authors: Bertolotti