Linear and nonlinear optical properties of pseudoisocyanine J aggregates in distributed feedback microcavities

The linear and nonlinear optical properties of pseudoisocyanine (PIC) J aggregates in 1-D distributed feedback (DFB) microcavities, photonic crystal slabs are investigated. The linear optical properties are well described by the DFB cavity-polaritons in the slabs. A polariton mode splitting of 50 meV and a photonic band gap of 30 meV are observed in PIC J aggregates dispersed in a polyvinyl-alcohol matrix. In the pump and probe experiments, we resonantly excited the cavity mode observed at the low energy side of the excitonic resonance, the virtual-exciton excitation condition. The response time is about 0.5 ps, which is approximately equal to the pump-pulse duration. We find the enhancement of the optical nonlinearity to be one-order of magnitude in the microcavity. Excitation of the dielectric-band mode is effective in enhancing the nonlinearity with an ultrafast response.