Polariton Lasing by Intra-cavity Pumping in the Strong-Coupling Limit and Enhancement of Molecular Fluorescence in Critically Coupled Resonators

Speaker: Vladimir Bulovic, Massachusetts Institute of Technology

Date: September 14, 2011

Event: Solid-State Lighting Science Workshop in Novel Emitters and Nanostructured Materials

Abstract: The strongly coupled states of light and matter in microcavities, known as polaritons, can enable a radically new class of optoelectronic devices based on the macroscopic coherence of photons and excitons. In particular, strong optical absorption and efficient luminescence of molecular organic materials allow for strong coupling and polariton lasing to be achieved at room temperature and with substantially reduced requirements for cavity quality factor. The first part of the talk will present room temperature polariton lasing in a lambda-thick microcavity where a highly absorbing thin film of molecular J-aggregates serves as the strong-coupling material. We will show a new device excitation scheme of intra-cavity pumping which circumvents exciton-exciton annihilation losses inherent to organic materials at high optical excitation densities. Using this flexible cavity architecture, polariton lasing at room temperature is achieved.

The second part of the talk will show that one mirror and the J-aggregate active layer of the polariton laser microcavity can act as a critically coupled resonator, which can be used for scalable, tunable, and homogeneous enhancement of molecular fluorescence. The operation of this device, called a J-aggregate critically coupled resonator, is based on the excitonic energy transfer from a highly absorptive thin film of J-aggregating dye molecules positioned at the anti-node of an optical half-cavity to a overlaying film whose fluorescence is enhanced in this structure. A 20-fold enhancement in molecular fluorescence is demonstrated, with the role of optical interference, Förster energy transfer, and exciton diffusion quantitatively analyzed to optimize device geometry, which can be broadly useful in light emitting structures.