Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 19: Plasmonics and Nanooptics II

O 19.10: Vortrag

Montag, 11. März 2013, 18:15–18:30, H31

Adiabatic nanofocusing of few-cycle laser pulses with wave-front shaping using a deformable mirror — •Pascal Engelke, Slawa Schmidt, Petra Groß, and Christoph Lienau — Institut für Physik, Carl von Ossietzky Universität, Oldenburg, Germany

Adiabatic nanofocusing of ultrashort laser pulses can be used to generate a highly confined light source with few nanometer spatial and few femtoseconds time resolution [1,2]. By grating-coupling a spectrally broad-band light source onto ultra smooth single-crystalline gold tapers, typically coupling efficiencies below 1% are reached. We have identified a wave-front mismatch between the illuminating laser pulses and the conical surface of the tip as a possible cause for the restricted coupling efficiency. Here we demonstrate shaping of the wave front to match the surface radius of curvature using a deformable mirror. The wave front curvature was adapted to the tip surface using an evolutionary algorithm. We found that the coupling efficiency of the light to surface plasmon polariton (SPP) wavepackets was improved considerably, resulting in an enhancement by a factor 8 of the light scattered from the tip apex. Interferometric frequency resolved autocorrelation techniques confirmed that the time structure of the 6-fs pulses was preserved. We anticipate that the demonstrated technique offers considerable improvement for scanning near field optical microscopy techniques.

[1] Berweger, S. et al. Nano Lett. 2011, 11, 4309*4313.

[2] Schmidt, S. et al. ACS Nano 2012, 6, 6040*6048