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Soft Matter and Biological Physics
Eur. Phys. J. E 9, 335-340 (2002)
DOI: 10.1140/epje/i2002-10090-4

Nonlinear optical characterization of cluster dynamic in water in oil microemulsion by a pump probe laser beam technique

L. Vicari

Istituto Nazionale per la Fisica della Materia, Università di Napoli "Federico II" and Dipartimento di Scienze Fisiche, Facoltà d'Ingegneria, p.le Tecchio 80, I 80125 Napoli, Italy

vicari@na.infn.it

(Received 26 October 2002 / Published online: 21 January 2003)

Abstract
We present a new pump probe laser beams configuration for the nonlinear optical characterization of microemulsions. We detect the variation of the on-axis optical intensity of the probe beam as generated by the concentration profile induced in an optically thin film of microemulsion by the pump beam. A mathematical model has been introduced to describe the phenomenon. The technique allows the determination of both Kerr-like optical nonlinearity and time constants and, therefore, it gives information both on cluster dimension and their shape. We discuss its application to WAD (water/AOT/decane, where AOT denotes sodium-bis-di-ethyl-sulfosuccinate) with the application of a strong electric field of optical source. Comparison between theoretical predictions and experimental results confirms the presence of giant optical nonlinearity in the absence of turbidity divergence. Chainlike shape of clusters, of the kind already reported with the application of strong electric field, could justify this result.

PACS
42.70.Nq - Other nonlinear optical materials; photorefractive and semiconductor materials.
82.70.Uv - Surfactants, micellar solutions, vesicles, lamellae, amphiphilic systems, (hydrophilic and hydrophobic interactions).
42.87.-d - Optical testing techniques.
78.20.-e - Optical properties of bulk materials and thin films.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2002