Abstract

Squaraines have attracted much research interest because of their large, nonresonant third-order optical susceptibilities γ_ijkl(−ω₄; ω₁, ω₂, ω₃).^1,2 Evidence has accumulated that a two-level model for γ_ijkl(−ω₄; ω₁, ω₂, ω₃). is not adequate even for molecules with negative γ_ijkl(−ω₄; ω₁, ω₂, ω₃).. Earlier we discussed the experimental observation of high-lying two-photon states that are critical to the negative γ_ijkl(−ω₄; ω₁, ω₂, ω₃). in squaraines, achieved by using femtosecond pump-probe techniques.³ We report here results from our recent full third-harmonic dispersion measurements on squaraine dyes using a tunable picosecond laser source based on optical parametric generation and amplification in KTP crystals pumped by a picosecond Nd:YAG laser.⁴

© 1995 Optical Society of America