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 ar e calculated according to a six-level model. The limiting threshold at T/T- 0 = 0.5 is 44 mJ/cm(2), and the throughput is limited to 27 mJ/cm(2) as inc ident fluence reaches 0.35 J/cm(2) for carboxyl pentaazadentate cadmium. Th e limiting thresholds and the throughput values are strongly influenced by peripheral substituents and central metal ions of the complexes. (C) 2001 O ptical Society of America.