Optical limiting of β-octa-octyloxy-phthalocyanines for pecosecond pulses in solution

摘要

The optical limiting performances for P-octa-octyloxy phthalocyanines with initial linear transmission T_0 = 88% ～92% at 532 run in a 5 mm spectroscopic cell in toluene have been measured with 35 ps pulses, in which β-octa-octyloxy phthalocyanine free-base exhibits the strongest optical limiting ability through a reverse saturable absorption from S_1?S_n excited singlet states with σ_(sl)= 4.0 x10~(-17)cm~2. The optical limiting thresholds are 50, 130 and 140 mJ/cm~2 at T/T_0 = 0.5 for phthalocyanine free base, nickel phthalocyanine, and lead phthalocyanine respectively. The throughput of the phthalocyanine free base is clamped down to 70 mJ/cm~2 with the limiting nonlinear transmittance T_(lim)= 18% as the incident fluence reaching to 400 mJ/cm~2. The solubility, aggregation behavior and photo-stability for P-octa-octyloxy phthalocyanines have been studied. The solubility of the P-octa-octyloxy phthalocyanines has an obvious improving, which dissolve in non-polar solvent more easily than in polar solvent. The aggregation equilibrium constant k = 5.6x10~3 in toluene for phthalocyanine free base is lager that in mixed solvent (k'=1.4x10~3), which means that the P-octa-octyloxy phthalocyanines aggregate more easily in non-polar solvent than in polar solvent through the π-π interaction . The P-octa-octyloxy lead phthalocyanine appeared a lower photo-stability among them.