Optical limiting of pentaazadentate metal complexes for picosecond pulses in solution.

The optical-limiting performances for four pentaazadentate metal complexes in tetrahydrofuran have been measured at 532 nm for 35-ps pulses, in which reverse saturable absorption from the singlet-singlet excited states should be responsible for the limiting mechanism. The excited-state parameters are calculated according to a six-level model. The limiting threshold at T/T0 = 0.5. is 44 mJ/cm2, and the throughput is limited to 27 mJ/cm2 as incident fluence reaches 0.35 J/cm2 for carboxyl pentaazadentate cadmium. The limiting thresholds and the throughput values are strongly influenced by peripheral substituents and central metal ions of the complexes.