Berlin 2008 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 9: Poster

DF 9.5: Poster

Tuesday, February 26, 2008, 15:00–18:00, Poster G

Transmission of light through subwavelength holes in thin metal films — •Mathieu Gentile^1,2, Felix Kalkum¹, Manfred Fiebig², and Karsten Buse¹ — ¹Physikalisches Institut, Wegelerstraße 8, 53115 Bonn, Germany — ²Helmholtz-Institut für Strahlen- und Kernphysik, Nussallee 14 - 16, 53115 Bonn, Germany

It was discovered a decade ago that a hole array in a thin metal film with hole diameters much smaller than the wavelength, λ, exhibit a transmission efficiency, η, higher than 100% in the visible range. Here, η denotes the intensity of light transmitted through the hole in relation to the intensity incident onto the hole area. Unfortunately, a satisfactory understanding of the intensity enhancement has not been reached up to date. The present work is devoted to the experimental quantification of η for transmission through a single circular hole. In particular, phase-conjugation experiments, in which holograms are recorded in LiNbO₃ crystals by focusing light onto a small hole in a metal film, will benefit from this quantification. Thus, LiNbO₃ crystals are used as a substrate for a 200-nm-thick gold metal film illuminated by a 532-nm-frequency-doubled Nd:YAG laser. Using the knife-edge method a Gaussian profile with radius of 3.82 µm and total power of 81 mW is determined for the focused beam. A peak transmission efficiency of (335 ± 7)% is observed for a 350-nm-diameter hole (2r/λ=0.66).