Excited state absorption dynamics of fast relaxing dye no. 5

The excited state absorption dynamics of the fast mode-locking dye No. 5 for Nd-glass lasers is investigated. The excited state absorption cross-section σ_ex for 1.053 μm picosecond pulse excitation is determined from energy transmission measurements. The excited state absorption populates a higher lying singlet state S₄. The population lifetime τ₄ of this state is determined from two-step excited fluorescence quantum yield measurements. The obtained values are σ_ex= (5.5±1)×10^-17 cm² and τ₄=60±20 fs.