The nonlinear absorption and optical limiting in phenoxy-phthalocyanines liquid in nano- and femto-second regime: Experimental studies

• The RSA of Pc with fs pulse excitation is larger than that of ns pulse excitation.
• The critical intensity of Pc2 is higher than Pc1 when the high ESA is introduced.
• The limiting thresholds of optical limiting were evaluated for both samples.

The nonlinear optical properties of 2, 9, 16, 23-phenoxy-phthalocyanine (Pc1) and 2, 9, 16, 23-phenoxy-phthalocyanine-zinc (Pc2) in solution, have been investigated using the Z-scan technique at 800 nm with 100 fs pulse width and at 532 nm with 10 ns pulse width, respectively. It is found that the reverse saturable absorption (RSA) with femtosecond pulse excitation is much larger than that of nanosecond pulse excitation. The nonlinear absorption properties in nanosecond regime and femtosecond regime were analyzed by using five-level model and singlet four-level model, respectively. The results show that the critical intensity value of Pc2 is higher than Pc1 when the contribution of the high excited-state absorption is introduced in the sample. Moreover, optical limiting based on RSA was performed and limiting thresholds were evaluated for both samples. The results show that the Pc1 and Pc2 exhibit better limiting characteristics because of its stronger RSA response.