Enhanced photostability and optical nonlinearity of nickel and cobalt organometallic complexes

Nonlinear optical and limiting properties of nickel, cobalt metal-organic complexes and ligand (L) {L = N,N′-o-phenylenebis (4-hyrdoxy-salicylideneimine)} were studied using Z-scan technique using Q-switched Nd: YAG laser with nanosecond pulses at 532 nm. The results reveal that metal complexes exhibit large negative nonlinear refractive index (n ₂ ) of the order of 10 ⁻¹¹ esu. The metal complexes displays large nonlinearity than the ligand due to effective charge delocalization between metal ion and ligand. The magnitude of ground state absorption cross section is small compared to the effective excited-state absorption cross section implying the observed nonlinearity is due to reverse saturable absorption. Further, metal-organic complexes exhibit enhanced optical limiting behaviour at nanosecond laser pulses.