We present our results of nonlinear optical properties of 2(3), 9(10), 16(17), 23(24) tetra tert-butyl
phthalocyanine (pc1) and 2(3), 9(10),16(17), 23(24) tetra tert-butyl Zinc phthalocyanine (pc2) studied in solution using
Z-scan technique with 800 nm, 100 fsec pulses, 532 nm, 6 nsec pulses and 633 nm continuous wave (cw) laser
excitation. Femtosecond open-aperture Z-scan data revealed these molecules exhibited strong 3PA coefficient (α3). The
estimated value of α3 was ~9.1 × 10-5 and ~9.5 × 10-5 cm3/GW2 for pc1 and pc2 respectively. Nanosecond open aperture Z-scan studies indicated the presence of strong nonlinear absorption with effective coefficients (α2) of ~310 and ~420 cm/GW for pc1 and pc2 respectively which are at least two orders higher than the recently reported phthalocyanines.
These phthalocyanines also exhibited strong optical limiting properties with nsec excitation with recorded limiting
thresholds of ~0.45 J/cm2. We observed large nonlinear response in the cw regime at 633 nm. The performance of
these alkyl phthalocyanines in various time domains vis-à-vis recently reported phthalocyanines is discussed in detail.