Solid state cavity QED: Strong coupling in organic thin films

We review our research efforts to develop solid state integrated devices that operate in the strong coupling limit of cavity quantum electrodynamics (QED) for eventual application in high speed optical switching, optical computing, and quantum computing. Our devices contain J-aggregates of (organic) cyanine dyes which, by virtue of their molecular arrangement and strong dipolar coupling, exhibit a collective narrow linewidth high oscillator strength optical transition. Using J-aggregates, the strong coupling limit can be reached at room temperature with large coupling strengths (Rabi-splitting >250 meV) in exciton-polariton microcavity structures. We demonstrate that high quality nanoscale thick J-aggregate films can be uniformly deposited over macroscopic substrates, engineered at the molecular level, and patterned into single or multi-dimensional photonic bandgap structures. Our unique methods for depositing J-aggregates enabled us to structure light emitting devices that demonstrated the first ever electrically pumped polariton emission, uniquely accomplished in room temperature operation. Additionally, we demonstrated critically coupled resonators that concentrate nearly all of the incident light into 5 nm thick J-aggregate films, yielding a record high effective absorption constant of 6.8 × 10⁶ cm^-1 for films with thickness that is less than 1% of the incident light wavelength. Such remarkable optical properties, enabled by scalable deposition techniques, suggest that J-aggregates are a unique materials platform on which to demonstrate integrated exciton-polariton devices with the far reaching properties of polaritons in the optical domain.