Nonlinear optical absorption of [(C₂H₅)₄N] ₂Cu(dmit)₂ irradiated by picosecond and nanosecond laser pulses

Nonlinear optical absorption of [(C₂H₅) ₄N]₂ Cu(dmit)₂ (dmit^2- =4,5-dithiolate-1,3-dithiole-2-thione), abbreviated as EtCu, dissolved in acetone has been investigated by open-aperture Z-scan technique with picosecond and nanosecond laser pulses in the near infrared region. Under irradiation with 40 ps, laser pulses at 1064 nm, two-photon absorption is observed and the two-photon absorption coefficient β _TPA is (5.8 ± 0.3) × 10^-13 m/W. While excited by 15 ns laser pulses at 1053 nm, the sample presents a strong reverse saturable absorption and its nonlinear absorption coefficient β_RSA is as high as (1.7 ± 0.1) × 10^-10 m/W. The mechanism responsible for the difference between the results is analyzed. All the results suggest that this material may be a promising candidate for the application to optical limiting in the near infrared waveband. A graph is presented. OA Z-scan curves of EtCu sample solution irradiated by 40 ps laser pulses at 1064 nm and 15 ns laser pulses at 1053 nm. © 2007 by Astro Ltd.