Abstract

Solutions of metallophthalocyanines and metallonaphthalocyanines have recently attracted attention because of the large optical nonlinearities observed in these materials. These nonlinearities arise from the fact that the materials possess a delocalized electronic system confined in the macrocyclic ring plane. The linear absorption spectrum of these systems exhibits two sets of absorptions bands, which are associated with the transitions in the macrocyclic ring system. In addition, these compounds exhibit an excited-state absorption in the energy range between the Q- and B-bands, where the linear absorption is weak. This absorption can be ascribed at short times to the Sl-Sn and at long times to the Tl-Tn absorption. Transmission and Z-scan measurements have been performed on solutions of chloro-aluminum- phthalocyanines (CAP) in methanol, and a silicon naphthalocyanine derivative (SiNc) in toluene, by using 30 ps pulses at 532 nm. We determined the singlet-singlet absorption cross-sections to be 4 × 10⁻¹⁷ cm² for CAP and 5 × 10⁻¹⁷ cm² for SiNc. We also used trains of 10 of these pulses separated by 7 ns. These latter measurements clearly show a cumulative effect that demonstrates the effect of the triplet-triplet absorption at longer times. From the Z-scan results we calculated n₂ values of 3.3 × 10⁻¹² esu for CAP and 4 × 10⁻¹² esu for SiNc for concentrations of 6 × 10⁻⁴ mol/1.

© 1990 Optical Society of America