Eur. Phys. J. E (2012) 35: 4
https://doi.org/10.1140/epje/i2012-12004-3

Regular Article

Tricritical-like behavior of the nonlinear optical refraction at the nematic-isotropic transition in the E7 thermotropic liquid crystal

¹ Departamento de Física, Universidade Estadual de Ponta Grossa, PR, Brazil
² Departamento de Física, Universidade Federal de Santa Catarina, SC, Brazil
³ Instituto de Física, Universidade de São Paulo, São Paulo, SP, Brazil

^* e-mail: sgomez@uepg.br

Received: 27 September 2011
Revised: 9 December 2011
Accepted: 15 December 2011
Published online: 24 January 2012

Abstract

We use Z-scan technique to investigate the nonlinear optical response of the thermotropic liquid crystal E7 in the neighborhood of the nematic-isotropic phase transition. The analysis of the data for the nonlinear optical birefringence is compatible with an effective critical exponent of the order parameter, β = 0.28 ± 0.03, which is close to the classical value, β = 0.25 , for a tricritical point. The nonlinear optical absorption in the nematic range depends on the geometrical configuration of the nematic director with respect to the polarization beam, and vanishes in the isotropic phase.