Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 46: Graphene: Dynamics (O with HL/TT)

HL 46.2: Talk

Wednesday, March 18, 2015, 10:45–11:00, MA 041

Non-linear luminescence and four-wave mixing from graphene, probed by femtosecond pulse shaping — •Richard Ciesielski¹, Alberto Comin¹, Matthias Handloser¹, Torben Winzer², Ermin Malic², and Achim Hartschuh¹ — ¹Ludwig-Maximilians-Universität, AK Hartschuh, Butenandtstr. 5-11, 81377 München — ²Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Germany

Ultrafast optical excitation of graphene leads to two main nonlinear emission signals in the visible. The first was described as incoherent non-linear photoluminescence (NLPL). The second results from near-degenerate four-wave mixing which is extraordinarily strong in graphene as compared to other materials. We investigated the two types of emission for different layer thickness using confocal microscopy and a 15 fs pulsed laser at 1.55 eV with a pulse shaper. Spectrally resolved autocorrelation scans revealed a continuously decreasing decay time of the NLPL from 1.2 eV towards 2.8 eV. Comparing the dynamics observed for different layers allows us to identify the influence of substrate induced doping. Finally, we were able to separate a weaker third contribution induced by the microscopic polarization of graphene [1].

Financial support by the DFG through the Nanosystems Initiative Munich (NIM) and the ERC (NEWNANOSPEC) is gratefully acknowledged.

[1] T. Winzer, R. Ciesielski, M. Handloser et al., arXiv:1411.0531v1 (2014).