Regensburg 2016 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 23: Plasmonics and Nanooptics: Light-Matter Interaction, Spectroscopy

O 23.8: Poster

Montag, 7. März 2016, 18:15–20:30, Poster E

Femtosecond pump-probe transmission measurements of spatially inhomogenous electron heating caused by plasmonic excitation in gold gratings — •Jonas Vondran¹, Felix Spitzer¹, Ilya Akimov¹, Boris Glavin², Vladimir Belotelov³, Sachin Kasture⁴, Arvind S. Vengurlekar⁴, Achanta V. Gopal⁴, and Manfred Bayer¹ — ¹Technische Universität Dortmund, Dortmund, Germany — ²V.E. Lashkaryov Institute of Semiconductor Physics, Kiev, Ukraine — ³Lomonosov Moscow State University, Moscow, Russia — ⁴Tata Institute of Fundamental Research, Mumbai, India

Periodically perforated gold films are subject to femtosecond resolved pump-probe transmission measurements which show ultrafast relaxation dynamics of optically excited electrons. Differential transmission is measured with varying incident angles and different polarisation configurations. Using biexponential fitting functions two distinct decay times can be observed in the transient data: A decay with a relaxation time of about 1 ps is attributed to electron-lattice energy transfer which is also present in unstructured gold films. A second, shorter relaxation is observed which shows a characteristic decay time of 200 to 300 fs. This decay is due to spatially inhomogeneous heat distribution inside the gold grating's slabs which causes an additional thermal diffusion process. Depending on the exciting pump polarisation this decay shows a changing sign which indicates an opposing direction of heat gradients with plasmonic compared to non-plasmonic excitation.