Abstract

We have measured the third-harmonic response, γ, of a centrosymmetric squaraine dye (ISQ) in chloroform at a range of frequencies for which the third harmonic is above the strong, narrow peak in the dye’s linear absorption spectrum but below the UV absorption band. By fitting the experimental dispersion of γ using a four-level model, we determine the strength, location, and width of the lowest-lying two-photon transition. We find that the 2¹Ag state appears just above the 1¹Bu state in energy and that the 1¹Bu–2¹Ag transition moment is somewhat smaller than the transition moment between the ground state and the 1 ¹Bu state but much larger than previously predicted for comparable squaraine dyes.

© 1994 Optical Society of America

Contribution of the 2 ¹Ag state to the third-order optical nonlinearity in a squaraine dye: errata

James H. Andrews, John D. V. Khaydarov, and Kenneth D. Singer
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Characterization of excited states of centrosymmetric and noncentrosymmetric squaraines by third-harmonic spectral dispersion

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