Optical limiting, pulse reshaping, and stabilization with a nonlinear absorptive fiber system

Optical limiting, pulse reshaping, and stabilization effects have been demonstrated based on a two-photon absorption mechanism with a dye-solution-filled hollow fiber system. The nonlinear absorptive medium is the solution of a new dye, trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium iodide (ASPI) in dimethyl sulfoxide, with which we filled a 20-cm-long quartz hollow fiber of 100-mm internal diameter. The input optical signal was a laser pulse train that contained ∼30 pulses of 130-ps pulse width. When the input peak intensity reached 400-1000-MWycm² levels, obvious optical limiting could be observed and the envelope of the transmitted pulse train became flatter and broader. By using another new dye solution, 4-[N-(2-hydroxyethyl)-N-(methyl)amino phenyl[-49-(6-hydroxyhexyl sulfonyl)- stilbene (APSS) in benzyl alcohol, which interacted with a series of ∼800-nm laser pulses of ∼8-ns pulse width, we obtained a much higher nonlinear absorption coefficient and a superior optical peak-power stabilization effect.