Optical limiting of pentaazadentate complexes in solution for nanosecond pulses

Abstract

Passive optical limiters are significant for protecting sensors and human eyes from high intensity laser. The selection of materials is still the key point for optical power limiters. The optical limiting perfor- mances have been measured for six new pentaazadentate metal com- plexes with initial linear transmission of 0.90 i na2m mcell in chloroform at 532 nm with 8 ns pulses, in which the reverse saturable absorption from the triplet!triplet excited state is responsible for the optical limiting. The optical limiting thresholds at T/T050.5 are 139 mJ/cm 2 , 350 mJ/cm 2 and 420 mJ/cm 2 for ((PMC-NO2)Cd)Cl, ((PMC-Np)Cd)Cl and ((PMC)Sm)Cl, respectively. The lowest nonlinear transmittance for ((PMC-NO2)Cd)Cl is 10%, while the incident maximum fluence reaches to 600 mJ/cm 2 . The ratios of T0 /Tlim are estimated at 2.3 to 9.0. The limiting thresholds are strongly influenced by the nature of the substitu- ents on the benzene ring and the heavy atom effect. Electron withdraw- ing groups of the complexes can enhance the limiting capability, and the heavy atom effect facilitates the decreasing of the limiting threshold. © 2001 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1334948) Subject terms: optical limiting; pentaazadentate metal complexes; limiting thresh- olds; lowest nonlinear transmittance.