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Proceedings Paper

An indole-based low molecular weight glass-former giving materials with high cooperative photorefractive optical gain
Author(s): Rocco Angelone; Marco Angiuli; Francesco Ciardelli; Arturo Colligiani; Francesco Greco; Annalisa Romano; Giacomo Ruggeri; Elpidio Tombari
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Paper Abstract

A derivative of 2-methylindole, namely 3-[2-(4-nitrophenyl)ethenyl]-1-(2-ethylhexyl)-2-metylindole (NPEMI-E) has been synthesized. Materials obtained from this molecule have been studied as thin films between two ITO layers. The study revealed that NPEMI-E collects in itself both photoconductivity and NLO characteristics. Differential Scanning Calorimetry (DSC) measurements showed the formation of stable glass films characterized by a Tg temperature lower than room temperature. Blends with the photoconductive poly-N-vinyl-2,3-dimethylindole (PVDMI) were also studied, giving again stable glass films independently of the wt.% contents of NPEMI-E. Photorefractivity measurements on both pure and blended NPEMI-E allowed to measure a value of the optical gain Γ = 627 cm-1 at an applied electric field E = 60 V/µm. This high value of Γ corresponds to a sharp maximum of the experimental trend of Γ as a function of the wt.% content of NPEMI-E. The corresponding content was wt.% = 91.5. The presence of this maximum induced us to make the hypothesis that, besides the well known reorientational contribution to the photorefractivity, a further mechanism (recently theoretically studied) is active in our blends. This mechanism arises in the interactions among the NLO polarized and polarizable moieties (cooperative effect). It can produce a rapid variation of some of the electrooptical parameters conditioning the extent of the photorefractivity. This can happen at a well defined mean intermolecular distance and hence at a well defined concentration of the NLO molecules.

Paper Details

Date Published: 20 April 2006
PDF: 12 pages
Proc. SPIE 6192, Organic Optoelectronics and Photonics II, 61922M (20 April 2006); doi: 10.1117/12.661692
Show Author Affiliations
Rocco Angelone, Univ. of Pisa (Italy)
Marco Angiuli, Istituto per i Processi Chimico-Fisici, CNR (Italy)
Francesco Ciardelli, Univ. of Pisa (Italy)
INFM, POLYLAB (Italy)
Arturo Colligiani, Univ. of Napoli Federico II (Italy)
INFM, POLYLAB (Italy)
Francesco Greco, Univ. of Pisa (Italy)
Annalisa Romano, Univ. of Napoli Federico II (Italy)
Giacomo Ruggeri, Univ. of Pisa (Italy)
INFM, POLYLAB (Italy)
Elpidio Tombari, Istituto per i Processi Chimico-Fisici, CNR (Italy)


Published in SPIE Proceedings Vol. 6192:
Organic Optoelectronics and Photonics II
Paul L. Heremans; Michele Muccini; Eric A. Meulenkamp, Editor(s)

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