0.5-femtosecond-resolution measurement of optical resonant tunneling time

Summary form only given. As recently reported by Ebbesen et al. (1998), a subwavelength hole array in a metallic film shows extraordinary transmission of light at wavelengths much larger than the hole size. This unusual effect was attributed to the resonantly enhanced coupling of the incident beam into the surface plasmon polaritons. We report the measurement of the delay of a short pulse when transmitted through the hole array. This delay time is important because it directly verifies the resonant nature of the transmission through subwavelength holes.