Issue 5, 2001

Abstract

The second-harmonic intensity from Langmuir–Blodgett films of 5-{4-[2-(4-dimethylaminophenyl)vinyl]benzylidene}-2-octadecyl-5,6,7,8-tetrahydroisoquinolinium octadecyl sulfate(1), interleaved with poly(tert-butyl methacrylate), increases quadratically with thickness to more than 100 bilayers. The susceptibility, molecular hyperpolarisability, thickness, refractive indices and chromophore tilt angle, relative to the substrate normal, are χzzz(2) = 45 ± 5 pm V−1 at 1064 nm, β = 8 × 10−38 m4 V−1, l = 3.65 ± 0.12 nm bilayer−1, nω = 1.53 ± 0.01, n = 1.56 ± 0.01 and φ = 44 ± 2°. The moderately high susceptibility arises from an optimised transparency/efficiency trade-off, the alternate-layer LB film being transparent at 1064 nm and having a very slight absorbance of 3.5 × 10−4 bilayer−1 at 532 nm. In contrast, alternate-layer films of the corresponding 7-diethylamino-2-oxo-2H-chromen-3-ylmethylene (2) and 3-(dimethylaminophenyl)prop-2-enylidene (3) derivatives, also reported, have absorbances of 1.1 × 10−3 and 1.5 × 10−3 bilayer−1 at 532 nm and resonantly enhanced susceptibilities of 60 and 95 pm V−1 respectively.

Graphical abstract: An improved efficiency/transparency trade-off for second-harmonic generation by extending the π-electron bridge of an optically nonlinear dye

Article information

Article type
Paper
Submitted
12 Dec 2000
Accepted
07 Feb 2001
First published
19 Mar 2001

J. Mater. Chem., 2001,11, 1345-1350

An improved efficiency/transparency trade-off for second-harmonic generation by extending the π-electron bridge of an optically nonlinear dye

G. J. Ashwell, A. J. Whittam, M. A. Amiri, R. Hamilton, A. Green and U. Grummt, J. Mater. Chem., 2001, 11, 1345 DOI: 10.1039/B009911M

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