LX12496B- This work demonstrates theoretically and experimentally that the peak of a pulse can emerge from a metallic plate perforated with tiny holes and sandwiched between dielectrics before the pulse enters the sandwiched subwavelength-hole array. The effect known as superluminality arises because of the coupling interference between two states: one coming up from a mode supported by the grounded dielectric slab, and the other emerging from the periodic pattern. While being counterintuitive, this phenomenon is physical and does not violate the causality principle, which is defined with respect the pulse turn-on time occurring before the peak time. In contrast previous works, the presented superluminal mechanism is scalable to any wavelength regime from radio frequencies to visible light, it uses a simple structure without any special (e.g. gain or absorptive) materials, and it occurs for substantial values of the transmittance. This
work expands our fundamental understanding of periodic gratings and may find applications in pulse re-shaping, tunable delay element with canceled group velocity dispersion, and beam spectral analysis.
