Principal Investigator Vladimir Bulovic
Co-investigator Timothy Swager
We demonstrate strong light-matter coupling using a promising new J-aggregate material based on a dibenz[a,j]anthracene macrocycle, that is robust under high power optical excitation. Strong light-matter coupling leads to polaritonic resonances that are superpositions of the underlying excitonic and photonic states and can exhibit laser-like coherent light emission at remarkably low excitation densities due to polariton condensation. A key hindrance to achieving polariton condensation thus far using cyanine dye J-aggregates has been exciton-exciton annihilation, which quenches excitations from the polaritonic states before they can condense. The J-aggregates of the dibenz [a,j] anthracene-based macrocycle show no signs of exciton-exciton annihilation until optical excitation densities exceeding 20 MW/cm2, while in thin films of a typical J-aggregated cyanine dye, TDBC, annihilation appears at 10 kW/cm2. Thin films of the macrocycle were prepared by spin-coating a 6 mg/ml solution of the dye in chlorobenzene, yielding layers that were 15 nm thick with an RMS roughness of less than 1 nm. The J-aggregation of the dye in these films was evidenced by the appearance of a narrow absorption line at 465 nm of FWHM = 15 nm and the concomitant disappearance of the monomer absorption band as the dye concentration was increased. The films possess an absorption coefficient of 2.1 x 105 cm-1 at the J-aggregate absorption peak wavelength of 465 nm, show good photochemical stability, and have photoluminescence quantum yield exceeding 90%. Strong coupling was observed when thin films of the macrocycle were situated in a lambda-2n planar optical microcavity consisting of a silver mirror and dielectric Bragg reflector. Devices exhibit polaritonic dispersion with a room temperature Rabi-splitting of 130 meV. Experiments are underway to demonstrate organic-based polariton condensation.