Title

Comparison Of Nonlinear Absorption In Three Similar Dyes: Polymethine, Squaraine And Tetraone

Keywords

Cyanine; Excited-state absorption; Polymethine; Squaraine; Tetraone; Two-photon absorption

Abstract

We performed a detailed experimental investigation and quantum-chemical analysis of two-photon absorption (2PA) spectra of symmetrical cationic polymethine and neutral squaraine and tetraone dyes having nearly identical terminal groups and similar conjugation length. Squaraine and tetraone structures differ from polymethines in that their conjugated backbone includes an electron accepting bridge. Frequency degenerate 2PA spectra of these molecules are measured by two-photon fluorescence spectroscopy and the Z-scan technique. Comparing 2PA spectra of polymethine with squaraine and tetraone structures, we find that we can access considerably larger 2PA cross-sections (≥8000 × 10-50 cm4 s/photon) in the squaraine and tetraone molecules due to an increase in the density of final states introduced by the electron accepting bridge in the conjugated chain. We discuss the difference in electronic structure for these molecules and introduce a link between 2PA and excited-state absorption spectra. The results of these experiments combined with agreement of quantum-chemical calculations moves us closer to a predictive capability for the relation between molecular structure and nonlinear optical properties. © 2008 Elsevier B.V. All rights reserved.

Publication Date

6-2-2008

Publication Title

Chemical Physics

Volume

348

Issue

1-3

Number of Pages

143-151

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1016/j.chemphys.2008.02.062

Socpus ID

43849097903 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/43849097903

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