Highly oriented molecular aggregates in 1-D photonic crystal slabs: toward the control of molecular arrangement from submicron to nanometer region

We have investigated the optical properties of one-dimensional photonic crystal slabs (PCSs) of molecular aggregates, and reported the vacuum Rabi splitting of 50 meV in pseudoisocyanine (PIC) J-aggregates in the strong coupling regime. The mode splitting should increase with the increase of the molecular density. Then, we fabricated PIC J-aggregates without any polymer matrix. As a result, we can observed Rabi splitting over 200 meV. Moreover, the strong J-band is observed only with the light polarization along the grooves. The observed strong anisotropy around the J-band indicates that almost all of the molecules are oriented along the grooves. It means the grooves with the several hundred nanometers period arrange the direction of molecules, nevertheless, the size of a molecule is less than 1 nm. This is one of the attractive features of molecular PCs, because we will be able to arrange nanometer structures with the use of the submicron structures.