Title

The Nature Of Excited-State Absorption In Polymethine And Squarylium Molecules

Keywords

Excited state absorption; Femtosecond; Nonlinear optics; Nonlinear spectroscopy; Polymethine dyes; Quantum chemical calculations; White-light continuum

Abstract

Subpicosecond transient absorption measurements were performed for several polymethine and squarylium dyes in ethanol solution and a polymeric host over the spectral range 400-1500 nm. A variety of nonlinear effects including saturable absorption, reverse saturable absorption, and gain were observed and analyzed. We observe strong excited-state absorption (ESA) in all dyes in the range 450-600 nm. We also report the first prediction and observation of additional ESA bands in the near-infrared range. The predictions were based on quantum chemical calculations and the ESA experiments were performed with femtosecond pump-continuum probe techniques. For polymethine dye 2-[2-[3-[(1,3-dihydro-3,3-dimethyl-1-phenyl-2H-indol-2-yli-dene) ethylidene]-2-phenyl-1-cyclohexen-1-yl]ethenyl]-3,3- dimethyl-1-phenylindolium perchorate, an additional ESA band was detected near 1250 nm, and for squarylium dye 1,3-Bis-[(1,3-dihydro-1-butyl-3,3-dimetyl-2H-benzo[e]indol-2-ylidene)methyl]squa raine, two additional ESA bands were found around 870- and 1380-nm, respectively. To further study the nature of these transitions, the steady-state excitation anisotropy was also studied and compared with predictions. The relationship between ESA spectra of organic dyes and their molecular structure is discussed.

Publication Date

9-1-2001

Publication Title

IEEE Journal on Selected Topics in Quantum Electronics

Volume

7

Issue

5

Number of Pages

849-863

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1109/2944.979347

Socpus ID

0035466354 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/0035466354

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