Stöferle, Thilo

Date: Thursday, May 21, 2015
Time: 11:15
Place: University of Bern, Sidlerstrasse 5, Hörsaal B116
Host: André Stefanov

Exciton-polariton Bose-Einstein condensation with a polymer at room temperature

Thilo Stöferle
IBM Research - Zurich

Integrated photonics is key for future data communication systems. A brief overview of the activities at IBM Research – Zurich will be given, with focus on our Quantum Photonics section, which investigates new microcavity structures and materials for enhanced light-matter interaction. In our experiments, we create exciton-polariton quasiparticles by exciting optically a microcavity filled with a ladder-type conjugated polymer in the strong coupling regime. At room temperature thermalization of these quasi-particles occurs while it is suppressed at low temperature because of a relaxation bottleneck. Above a certain excitation threshold with incoherent off-resonant picosecond laser pulses, we observe the emergence of non-equilibrium Bose-Einstein condensation in the lower polariton branch. This is evidenced by several distinct features such as a blue-shifted emission peak at zero in-plane momentum, accompanied by a nonlinear increase in the emission intensity and a sudden drop of the linewidth. Furthermore, the emission becomes polarized and the emission dynamics is drastically shortened. Spatially-resolved measurements with a Michelson interferometer show a macroscopic phase relation over almost the whole spot, and the fringe pattern exhibits non-flat phase fronts and fork-like dislocations, indicating a large number of vortices and excitations. Our approach demonstrates a radically simplified route to Bose-Einstein condensation physics at ambient conditions with easy-to-process non-crystalline materials.

Link: http://www.iap.unibe.ch/pdf.php?module=seminar&seminar=laser&id=457