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Tunneling of optical pulses through photonic band gaps.

Propagation of electromagnetic wave packets through 1D photonic band gap materials has been studied using 12 fs optical pulses. The measured transit time is found to be paradoxically short (implying superluminal tunneling) and independent of the barrier thickness for opaque barriers, in analogy to the behavior of electrons tunneling through potential barriers. Shortening of Fourier-limited incident wave packets is observed upon transmission through these linear systems. Although in apparent conflict with causality and the uncertainty principle, neither of these general principles is violated because of the strong attenuation suffered by the transmitted signals.