Regensburg 2002 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 10: Funktionalisierte Polymere
CPP 10.1: Talk
Tuesday, March 12, 2002, 16:10–16:30, H38
Laser Emission of a Dye-Doped Cholesteric Polymer Network — •Jürgen Schmidtke1, Werner Stille1, Heino Finkelmann2, and Sung Tae Kim3 — 1Fakultät für Physik, Albert-Ludwigs-Universität, Hermann-Herder-Str.3, 79104 Freiburg — 2Institut für makromolekulare Chemie, Albert-Ludwigs-Universität, Stefan-Meier-Str. 31, 79104 Freiburg — 3Optoelectronic Materials Departments, LG Cable Research Center, Kyungki-do, 431-080, Korea
A cholesteric liquid crystal acts as a resonator for circularly polarized light, showing two resonance frequencies located at the edges of the selective reflection band. This gives rise to enhanced spontaneous as well as stimulated emission of embedded fluorescent dye molecules at one of the resonance frequencies, and above a certain pump theshold, laser emission is observed. In low molar mass cholesterics, laser emission is found to be limited by distortions due to the heat dissipated in the lasing process. We have investigated a possible way to improve the emission characteristics, namely by stabilizing the cholesteric order by chemically crosslinking the mesogens. We demonstrate that a highly crosslinked cholesteric polymer network as well can act as a laser resonator. By comparing the emission characteristics of the network and a low molar mass sample with similar optical parameters, we find that the network’s frozen-in heterogeneities don’t affect the lasing threshold significantly. Most remarkably, the lasing efficiency is found to be more than one order of magnitude higher than that of the low molar mass sample.