SATURABLE ABSORPTION DYNAMICS OF MODE-LOCKING DYE DODCI

The saturable absorption dynamics of DODCI (3,3'-diethyloxadicarbocyan ine iodide) is studied by nonlinear transmission measurements. At 527 nm dye solutions in ethylene glycol and methanol are excited with pico second pulses. In the wavelength region from 581 nm to 628 nm the dye in ethylene glycol is excited with femtosecond laser pulses. At 626 nm P-isomer-enriched DODCI is studied. The experimental transmission cur ves are analysed using a decoupled N-isomer and P-isomer S-0-S-1-S-m-S -n multilevel system. An S-m --> S-1 absorption recovery time of tau(A )(S1) = (600 +/- 100) fs is determined. The picosecond and femtosecond pulse excitation leads to S-0 --> S-1 ground-state absorption bleachi ng and S-1 --> S-m first excited-state absorption bleaching. The excit ed-state absorption cross-sections sigma(ex)(S1) (S-1 --> S-m) and sig ma(ex)(Sm) (S-m --> S-n) are determined.