Nonlinear optical effects related to saturable and reverse saturable absorption by subphthalocyanines at 532 nm

It is found that both effects of saturable absorption and reverse saturable absorption are obtained with a solution of subphthalocyanine 2 at 532 nm depending on the intensity of 9 ns laser pulses; saturable absorption occurs at lower intensity levels whereas the reverse effect prevails at higher levels; contrary to expectations, subphthalocyanines can behave as reverse saturable absorbers at 532 nm, despite the high linear absorption at this wavelength; data have been fitted with a five-level model which considers three consecutive electronic transitions with absorption cross-section values of 1.4 × 10^-16, 1.0 × 10^-16 and 40 × 10^-16 cm^2, respectively.