Two-photon absorption properties of (N-carbazolyl)-stilbenes

We have studied the two-photon absorption (TPA) and fluorescence properties of a series of phenylpolyenes with N-carbazolyl as donor end-groups in symmetric positions. The symmetric substitution of carbazole end-groups enhances the photostability of the molecules and maintains high TP coefficients (delta(max) similar to 1000GM). High fluorescence quantum efficiencies have been measured. The results suggest that TP chromophores with carbazole donors are promising materials for applications in two-photon imaging and sensitization. The study covers a broad excitation spectrum from 580mm to 820nm using a picosecond optical parametric source. We take advantage of the correlation between idler and signal waves emerging from the parametric generator and calibrate our results against Rhodamine B for which reliable data is available in the long wave range.