Optical limiting of penta-azadentate complexes in solution for picosecond pulses

Abstract

The passive optical limiters are of 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 performances for five new pentaazadentate metal complexes with transmission of 0.45 - 0.70 in a 1 cm cell in tetrahydrofuran have been measured at 532 nm with 35 ps pulses, in which the reverse saturable absorption from the singletyieldssinglet excited state is responsible for the optical limiting. The optical limiting thresholds of pentaazadentate and benzopentaazadentate cadmium complexes at T/To equals 0.5 are 44 mJ/cm2 and 146 mJ/cm2 respectively, the lowest nonlinear transmittance for pentaazadentate complex I is 7.7%, while the incident maximum fluence reaches to 881 mJ/cm2. The bounds of figure of merit-like are estimated at 1.7 - 8.7. The limiting thresholds are strongly influenced by the nature of the substituents on the benzene ring. Electron withdrawing groups of the complexes can enhance the limiting capability, while the effect of heavy atom acts opposite roles. The optical limiting abilities are compared with C60, tetra- phenyl-tetrabenzoporophyrin-zinc and octanoxyl- phthalocyanine free base at same conditions. The sequence of the limiting capability is pentaazadentate cadmium complex >C60 > tetra-phenyl-tetrabenzoporphyrin-zinc > octanoxyl-phthalocyanine free base.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.