Regensburg 2013 – scientific programme

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O: Fachverband Oberflächenphysik

O 63: Plasmonics and Nanooptics V

O 63.3: Talk

Thursday, March 14, 2013, 11:00–11:15, H38

Nonlinear Optical Properties of Gold Thin Films by Controlled Percolation — •Stefano De Zuani, Tobias Knoblauch, Audrey Berrier, Bruno Gompf, and Martin Dressel — 1.Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart

When a metal is evaporated onto an insulating substrate and the metal filling factor is gradually increased, close to the percolation the almost touching metallic particles form an almost closed film and the insulator to metal transition occurs. The optical conductivity of such ultrathin metal films is dominated by a Drude component starting at the percolation threshold in the low-frequency range and by localized surface plasmons of the isolated particles. The interplay of both components leads to a dielectric anomaly in the infrared region with a divergence of the real dielectric constant at the insulator to metal transition. We present a systematic study of the nonlinear optical properties of ultrathin gold layers around the percolation threshold in order to correlate the dielectric anomaly in the real dielectric constant to the nonlinear signal of the films. We control the approach to percolation by using metallic seeds as templates for the formation of the islands, and by pre-heating the substrates. In this way the density of the metallic clusters is kept constant. We investigate the role of the capacitive coupling of the almost touching gold clusters on the nonlinear properties of the metallic film. This work brings fundamental understanding of the nonlinear properties of ultrathin metallic films and it opens the way to an active tailoring of the nonlinear signals.