The confinement of a semiconductor material to an optical microcavity leads to an
inherent coupling between light and matter. Depending on the lifetime of the excited
state of the semiconductor (the exciton) and the cavity photon, two distinct regimes of
interaction are possible. The system is said to be weakly coupled if either the exciton or
the cavity photon decay before the two species interact. Weak exciton-photon coupling
results in a modification of the exciton lifetime, the spectral shape, and the angular
dispersion of emission from the microcavity. Conversely, when the lifetimes of the
exciton and cavity photon are long enough so that an interaction occurs prior to either
state decaying, the regime of strong exciton-photon coupling is realized. The timescale
for coupling is the Rabi period, which depends on exciton and cavity parameters
including the exciton oscillator strength and transition linewidths. The eigenstates of the
strongly coupled system are known as microcavity polaritons. Microcavity polaritons
have unique properties arising from their mixed exciton-photon character, permitting the
realization of novel optoelectronic devices. Organic semiconductors are attractive for
application in strongly coupled systems due to their large exciton binding energy (~1 eV), which permits a robust coupled state that is stable at room temperature and under
electrical excitation. In addition, organic semiconductors exhibit large exciton oscillator
strengths (~1015 cm-2) resulting in a strong interaction between the cavity photon and the
exciton. We aim to better the understanding of polaritons in organic semiconductor
microcavities to push the field towards novel optoelectronic devices.
University of Minnesota Ph.D. dissertation. December 2012. Major: Material Science and Engineering. Advisor: Russell J. Holmes. 1 computer file (PDF); ix, 194 pages, appendix p. 187-194.
Lodden, Grant H..
Light-matter interactions in optical nanostructures based on organic semiconductors.
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